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'1'11' " 1'11 1i 1, 1" 1111,1111 '11 -,'"'.1"."T"'1',1‘ 1' '1. 1 , 1111' l, 0" ‘ '1 1', 'JF""'L1'y":11' I'1II'F'I'"'1‘1"'"" ,11 “"‘""',1"1"'I'II'1 1"'I ',1'""'1“"'° 'l",""A,'N'.1,-'('1""'1 ' t'hi . "I . .. ,l 1 '1' f3'-“~ ' '111"""'"'1 11' "1'1 ' '~""“1 1111‘ 1'1 '1'; “’11-.171'13111‘11Y" ' ' {1'95 11-1“-1?12"" " -' . 1; 'I '11 1'1111' 'l1'1'1' ' .I I", "."'."' 1“,? "1:11, II II, '1 J‘.‘ ' ' '1I|\1',1I"," '1" l' “0'“. 'EE ' '..1"' ".111 ""1'1'1.'v,l'1p1 $11111“ '. 1&1"?le 'W'i'i'""""i1".""'1"y ' "IN;.'L\I"" .'-4“"' ' 1"‘""'¢1.:N “I 1AL I! 'h 'uifilf'i' 36"" Stub"? i'l'ufjfilgn'l ' ["111"!\"1 ‘ "3’ ¢ 7*;1111'1 .. THESlS This is to certify that the thesis entitled Comparisons of Resource Allocation, Growth Rates and Phenology between the Sexes of Box-Elder (Acer negundo L.) presented by Paul F . Ramp has been accepted towards fulfillment of the requirements for M. S . degree in ___QL§n.}L_B yfflaééjwému— / t, M or professor Date 9 May 1984 0.7639 MS U is an Affirmative Action/Equal Opportunity Institution MSU LIBRARIES .—:— RETURNING MATERIALS: Place in book drop to remove this checkout from your record. FINES will be charged if book is returned after the date stamped below. COMPARISONS OF RESOURCE ALLOCATION, GROWTH RATES AND PHENOLOGY BETWEEN THE SEXES OF BOX-ELDER (ACER NEGUNDO L.) BY Paul F. Ramp A THESIS Submitted to Michigan State University in partial fulfilment of the requirements for the degree of MASTER OF SCIENCE Department of Botany and Plant Pathology 1984 ABSTRACT COMPARISONS OF RESOURCE ALLOCATION, GROWTH RATES AND PHENOLOGY BETWEEN THE SEXES OF BOX-ELDER (ACER NEGUNDO L.) BY Paul F. Ramp Biomass allocation, growth rates, and sex ratios were investigated in studies of Acer negundo. Dimension analysis techniques indicated significant differences between sexes in both vegetative and reproductive allocation patterns. Leaf biomass of staminate (male) trees was 21% greater than pistillate (female) trees (P<.001). Biomass allocation to wood and bark is slightly, though not significantly, greater in females. Females expend a greater biomass to reproductive effort at field levels of seed production (835% greater, P<< .001). Females exhibited a significantly greater radial growth than males (6.7% greater, P<.05). On a yearly basis, females produced 11.2% more aboveground biomass than males of which 7.6% is wood biomass. Sex ratios of several populations were not significantly different from 1:1 although males consistently outnumber females. These findings are in contrast to a previous report on A, negundo. This study provides insight into the ecological significance of dioecy in this species. ACKNOWLEDGMENTS I would like to gratefully acknowledge the encouragement and assistance of my major professor, Dr. S. N. Stephenson. His observations and insights played a major role in this research. I would also like to thank my committee members, Dr. P. G. Murphy and Dr. J. W. Hanover for their suggestions on an earlier draft and their appraisals of the study. ii TABLE OF CONTENTS List of Tables...................................iv List of Figures...................................v Introduction......................................1 Description of Plant..............................8 Allometric Analysis..............................12 Methods......................................13 Results......................................19 Discussion...................................30 Demographic Stand Structure and Growth Interactions..........................38 Methods......................................38 Sex Ratio...........................£...38 Size Relationships......................38 Growth Rates............................39 open Stand...0.0.00.00000000000000039 Juvenile Stand.....................39 Dense Stand........................40 Results......................................4O Sex Ratio...............................40 Size Relationships......................42 Growth Rates............................45 Open Stand.........................45 Juvenile Stand...0.0.0.00000000000045 Dense StandOOOOOOO00.0.00000000000045 Discussion...................................53 Sex Ratio...............................53 Size Relationships......................54 Growth Rates............................55 Phenology and Resource Allocation................68 MethOdSOO0.00.00.00.00.00000000000000000000.068 Results.OOOOOOOOOOOOOOOO0.0.0.00000000000000070 Seasonal Phenology......................7O Seasonal Allocation.....................76 DiscuSSion...I.0.0.0.0....000000000000000000079 summarYOOO...OOOOOOOOOOOOOOOOI0.0.0.000000000000094 Appen61XOOOOOOOOOOOOOOOOOOOO0.00.00.00.000000000097 Literature CitedOOOOOOOOOOOO0.00.00.00.000000000103 iii LIST OF TABLES Previously Reported Sex Differences in Acer negundo Regression parameters for above ground oven dry biomass Regression parameters for 1982 growth correction Regression parameters for reproductive structures Regression parameters for leaf mas and leaf area Regression parameters for tree form Mean basal area and sex ratio of ten Michigan populations Regression parameters for growth of mature and juvenile trees Analysis of variance of growth in closed canopy stand Mass accumulation in spring growth Seasonal biomass accumulation Wood and bark oven dry densities (grams) Regression parameters for new branch mass Regression parameters for new branch leaf mass Regression parameters for calcualtion of new branch mass on existing branches Regression parameters for total branch mass Regression parameters for leaf mass iv 20 25 26 33 36 41 46 52 71 77 97 99 99 100 101 102 LIST OF FIGURES Relationship between female oven dry wood mass and stem diameter Relationship between male oven dry wood mass and stem diameter Relationship between female mass of new shoots and stem diameter Relationship between male mass of new shoots and stem diameter Relationship between female leaf mass and stem diameter Relationship between male leaf mass and stem diameter Relationship between female spring diameter and fall diameter in 1982 Relationship between male spring diameter and fall diameter in 1982 Relationship between female inflorscence number and stem diameter Relationship between male inflorscence number and stem diameter Relationship between total seed mass and the number of seeds per inflorscence, mid-summer Relationship between total seed mass and the number of seeds per inflorscence, end of summer Distribution of standing biomass in 10 cm diameter trees (kilograms) Distribution of standing biomass in 10 cm diameter trees (percent of total mass) Relationship between female leaf area and stem diameter Relationship between male leaf area and stem diameter 21 21 22 22 23 23 27 27 28 28 29 29 31 31 34 34 Size distribution of sexes from Haslett Rd. E. site Female mean size of maturity Male mean size of maturity Relationship between female tree diameter and age (in centimeters) Relationship between male tree diameter and age (in centimeters) Mean ring widths of trees 70+ centimeters in girth from closed canopy stand Mean ring widths of trees 60 to 69.9 centimeters in girth from closed canopy stand Mean ring widths of trees 50 to 59.9 centimeters in girth from closed canopy stand Mean ring widths of trees 40 to 49.9 centimeters in girth from closed canopy stand Mean ring widths of trees 30 to 39.9 centimeters in girth from closed canopy stand Mean ring widths of trees 0 to 29.9 centimeters in girth from closed canopy stand 1978 mean 1978 mean 1979 mean 1979 mean 1980 mean 1980 mean 1981 mean 1981 mean 1982 monthly monthly monthly monthly monthly monthly monthly monthly monthly precipitation deviation from the temperature deviation from the precipitation deviation from the temperature deviation from the precipitation deviation from the temperature deviation from the precipitation deviation from the temperature deviation from the precipitation deviation from the vi 43 44 44 47 47 48 48 49 49 50 50 6O 60 61 61 62 62 63 63 mean 1982 monthly temperature deviation from the mean Spring mass accumulation in reproductive tissue Spring mass accumulation of tissue developing from the terminal bud Spring mass accumulation in leaf tissue associted with reproductive tissue Spring mass accumulation rate of foliage associated with reproductive tissue Distribution of biomass in one seasons growth (kilograms) Distribution of biomass in one seasons growth (percent of total mass) Seasonal progression of mass accumulation in reproductive tissue Rate of mass accumulation in reproductive tissue Upper leaf surface of male Upper leaf surface of female Lower leaf surface of male Lower leaf surface of female Seasonal mass accumulated per photosynthetic mass investment Seasonal mass accumulation per leaf area Growth of the prolific tree from the WQA N. site Relationship between female bark density and stem diameter Relationship between male bark density and stem diameter vii 64 64 73 74 75 75 78 78 80 80 85 85 87 87 89 89 92 98 98 INTRODUCTION Sexual recombination of genes in plants occurs with the fusion of two gametes produced by the gametophyte generation of a plant's life cycle. In all higher plants the gametophyte generation has specialized into two distinct forms; one for the transport of genes from their origin to a location where fertilization is possible, the second, a non-mobile gametophyte imbedded in specialized sporophyte tissue to protect and provide nutrient support to the developing embryo. These gametophyte plants are designated male and female, respectively. The development of dioecy (the production of only one form of gametophyte by an individual sporophyte) in a species creates the potential for specialization of the sporophyte generation into either a gene disperser (the male function) or an embryo developer (the female function). This study has been conducted to examine what, if any, specialization has occured in the sporophyte generation of Acer negundo L., a woody, long-lived, dioecious perennial. The measures by which the sexes are compared are biomass production, resource partitioning patterns, growth rates and seasonal phenologies. In approximately 95% of the species of flowering plants, an individual of the sporophyte generation is capable of, and normally produces both Sperm producing and egg producing gametophytes (Yampolsky and Yampolsky, 1922). 1 2 The majority of these species are refered to as hermaphrodites, plants which produce both male and female gametophytes within the same flowering structure. A much smaller percentage of these plants fall into a catagory termed monecious. As with hermaphrodites, a single individual of a monecious species will produce both male and female gametophytes, however these are formed in separate flowering structures. The study at hand is concerned with the remaining 5% of flowering plant species which are termed dioecious. In these plants a single individual sporophyte is capable of producing only one form of gametophyte, either male or female. Interestingly in spite of the fact that such a small proportion of higher plants have developed this mode of reproduction that is considered by some as an evolutionary failure (Westergaard,1958), approximately 75% of the angiosperm families have species that are dioecious (Yampolsky and Yampolsky, 1922). Because of this wide spread occurrence, dioecy is considered to have evolved from hermaphrodite ancestry many different times in the angiosperms (Westergaard,1958). This suggests that rather than being an evolutionary "dead-end", dioecy may be an adaptive response to one or more environmental forces encountered by the species, and as such, represent one facet of niche specialization. With the evolution of dioecy in a species, the potential exists for the specialization of the sporophyte generation to its sexual role just as the gametophyte generation has been found to specialize (Lloyd and Webb, 1977; Soule, 1981). The staminate sporophytes, which produce male gametophytes (pollen grains) and consequently the male gametes (sperm), may be able to specialize specifically for more efficient dispersal and delivery of pollen to the female sporophyte. Likewise, pistillate sporophytes, producing the female gametophyte (the embryo sac), potentially could specialize for the procurement of pollen, the fertilization of the egg, the development of the embryo into a viable seed, and the dispersal of seed. This specialization by the sexes may include the evolution of mechanisms for the Optimal use of potentially limiting resources such as carbon, water, and nutrients (Wallace and Rundel, 1979). Many dioecious species have, in fact, been found to produce staminate and pistillate sporophyte individuals with divergent morphological, physiological, and in some ecological characters which are not directly related to the reproductive process. In the desert shrub, Simmondsia chinensis, Wallace and Rundel (1979) found leaf and canopy dimorphisms between the sexes. These differences observed are presumably due to specialization by the plants to their respective sexual functions. Because the sporophyte of a dioecious species produces gametophytes and thus gametes of one form only, e.g. sperm or egg, it has become common and accepted practice to refer to staminate and pistillate sporophyte plants as males and females respectively (Westergaard, 1958). This report will adhere to this convention. Male reproductive functions are generally presumed less energy and material demanding and of shorter duration than female reproductive functions and, consequently, male sporophytes are considered to have a greater supply of resources available for vegetative growth and an increased probability of survival (Darwin, 1877; Putwain and Harper, 1972; Freeman et al., 1976; Lloyd and Webb, 1977; Wallace and Rundel, 1979; Gross and Soule, 1981; Soule, 1981). Several such cases have been described. There are several reports on long—lived perennials which indicate males tend to exceed females in size, vigor, growth, and vegetative propagation. Dioecious trees which have been described having larger males include Juniperus communis, Ginkgo biloba, Taxus baccata, Fraxinus excelsior, and Populus nigra (cited by Bourdeau, 1958). In the herbaceous Aciphylla scott-thornsonii and Asparagus officinalis, males were found to be larger than females (cited in Lloyd and Webb, 1977). Lloyd and Webb (1977) give an extended account of previous studies and one is refered there for a summary of these reports. One notable exception to this trend is described in a study by Grant and Mitton (1979) in which females of Populus tremuloides were found to have greater growth increments (indicated by ring widths) than males. In contrast to this class of dioceious species, the reports of annuals and short lived perennials indicate that females are generally taller and have greater biomass than males. In Cannabis, Amaranthus palmerii, Silene alba, g. diocia, Rumex acetosa, Mercurialis perennis, M. ggggg, Thalictrum dioicum, I, dasycarpum and Acnida altissima females are found to exceed males in growth or height (cited in Lloyd and Webb, 1977; Lemem, 1980; S.N. Stephenson, pers. comm.). In these instances, the greater size of females is generally attributed to the extended growing period relative to the males (Lloyd and Webb, 1977). In the reports to date, the degree to which the sexes differ in secondary characters is generally small. The differences are usually not in themselves of a magnitude and constancy to reliably identify a sex without the sexual structures present (Lloyd and Webb, 1977). Considering this general lack of qualitative secondary sexual distinction, it is not too surprising that the number of reports comparing quanitative measurments is somewhat small. However, when one considers the potential implications of secondary sexual specialization to the ecological requirments of the sexual function and the evolutionary effort to maintain a viable species, the lack of attention is somewhat surprising. The impetus of this study results from the preliminary results of Stephenson (pers. comm.) which indicate that the mean basal area of females is greater than the mean basal area of males in 8 of 9 populations in central Michigan. These results are in disagreement with a previous study of Age; negundo in which males are reported to have a greater diameter and height than females (Lysova and Khizhnyak, 1975). Additionally, their report, which has been cited relatively frequently by other authors, describes males as having greater hardiness and as having a productivity and "vitality" of up to 2 times greater than females. A summary of their results as well as the results from the nine Michigan populations are shown in Table 1. The differences between these data should serve as a backdrop to the present study. TABLE 1. Previously reported sex differences in Acer negundo. From Lysova and Khizhnyak (1975) and Stephenson (pers. comm.). STAND DENSITY, BASAL LOCATION AGE TREES AREA HEIGHT MASS SEX PER HA RATIO* RATIO* RATIO* RATIO* "Demin" kokhoz 20 4950 1.49 1.32 1.95 1.00 near Kamyshin 36 6400 2.66 1.14 1.75 1.10 in Kamyshin 32 - 1.40 1.50 - 2.20 Volgograd 9 625 1.12 1.08 1.21 1.70 Michigan Populations** 1 5-6 520 .72 - - 1.40 2 12-15 - .78 — - 1.38 4 14-15 800 .65 - - 1.13 5 14-15 - .82 - - 1.41 6 20 - 1.04 - - 1.02 7 - - .59 - - 1.11 8 - - .57 - - 1.10 9 - - .75 - - 1.74 10 - - .82 - - 1.08 * Malezfemale ratio. ** Michigan locations provided in Table 7. DESCRIPTION OF PLANT Acer negundo L. is a small maple rarely reaching 22 meters in height (Preston 1976) although individuals may attain a much greater stature (the national champion from Washtenaw CO., Michigan has a height of 33.5 meters, a girth of 5.25 meters, and a crown spread of 36.5 meters, Thompson 1983). The tree is little used as a domestic or commercial wood source due to its soft wood and typically poor tree form (Preston 1976). However, because of its rapid growth, A. negundo has been suggested as a source of wood fiber and energy (Gyer 1981, Schlaegel 1982). Five varities of A. negundo are recognized in North America, A. negundo var. violaceum J.& B. is the variety found in the northeastern portion of the United States and studied in this report (Preston 1976). The leaves of A. negundo are compound with reportedly 3 and rarely 5 to 7 leaflets (Preston 1976); however, it has been my observation that only the leaves which develop early in the season have 3 leaflets. As the season progresses, the number of leaflets steadly increases. As commonly found in dioecious species, the flowers are small and a neutral (light green) color (Bawa and Opler, 1975). The staminate (hereafter refered to as male) flowers are born in dense clusters arrising from the bud. Pistillate (hereafter refered to as female) flowers are on drooping racemes with an average of slightly over 7 flowers per 8 raceme (see Table 4). Four to six stamens are produced on each male flower. Female flowers contain two ovaries with two long stigmas (to 10 mm, Wagner, 1975). As previously reported (Hesse, 1979) and observed in this study, pollination is strictly anemophyllus. Wind pollintaion has been found to be most common among dioecious Species (Freeman et al., 1980). The seed of A. negundo is contained within a single-winged fruit (samara) adapted for wind dispersal. The length of the samara ranges from 3 to 5 cm. A detailed examination of the samaras of A. negundo and several other species with special emphasis on thier dispersive capabilities has been conducted by Green (1980). As far as has been observed, the sexes of A. negundo are fixed. No evidence of the switching of sex, or of individuals producing organs of both males and females has been observed during this study. In only one case, in which a branch from a juvenile individual had grafted to a male individual, has a single tree been found to possess both reproductive functions. In this situation a limb, partially broken from a nearby individual, had formed a natural graft. Below the graft, the limb was nonreproductive, above the graft, pistillate flowers had been produced and seed was set. Three previous reports have identified or suggested that hermaphrodites, though exceedingly rare, may be found in A. negundo. Fraser (1912) described a tree which had 10 bisexual flowers on an injured branch, the remainder of the tree being pistillate. Otis (1931) illustrated the flower of A. negundo as bisexual although no evidence was cited that bisexual flowers had actually been found. More recently, Wagner (1975) found six small trees with bisexual flowers in southeastern Michigan. In five of these trees the majority of flowers were pistillate with only a few bisexual but in the sixth, the majority of flowers had both stamens and pistils. The number of stamens produced in the bisexual flowers (between 1 and 4) is less than the number typically found in strictly male individuals. The infructescence of bisexual flowers was also found to differ from those found on strictly female individuals in that the reproductive axis is much shorter and the samaras are noticably smaller. A delay in the dehiscence of anthers from bisexual flowers results in these flowers being functionally pistillate making this rare occurance of bisexuality effectively rarer . That the sexes are fixed, or nearly so, is not surprising, gender apparently being determined by an unequal chromosome pair in males (Sinoto, 1929). Unfortunately, this sex determining mechansim is as yet insufficiently established and should only be accepted with reservation (Sinoto, 1929). A later report by Foster (1933) confirms n=13 in A. negundo but fails to note an unequal chromosome pair. However, Foster's report was a survey of the chromosome number in AEEE and Staphylea and was not looking for sex determining mechanisms. 11 The communities in which A, negundo may have historically occurred in the deciduous forest region of North America are probably similar to those described by Petranka and Holland (1980). In an analysis of the bottomland communities of south-central Oklahoma, they found A. negundo to be an important species adjacent to stream channels. The biology of A. negundo, with its rapid, weed-like growth, has undoubtedly been selected to take advantage of the relatively short lived sites created by flood damaged banks and Shifting sand bars. In more recent times, aided by the disturbances of man, this species has been able to invade upland areas for short periods of time following disturbance. A. negundo is a common inhabitant of old fields and ditches in central Michigan and has been found to be one of the two most common Species to establish on road cut disturbances in eastern Kentucky (Levy, 1981). ALLOMETRI C ANALYS I S The following section of this report presents the distribution and accumulation of above ground biomass in the vegetative and reproductive tissues of Acer negundo. Differences (if such exist) in biomass accumulation and biomass partitioning might be expected based on the literature and current theories relating sexual dimorphisms and from the results of the census data presented in Table 1 and 7. Biomass has been chosen as the alloted "currency" to be measured for three reasons. First, despite its drawbacks and limitations, biomass has been the traditional measure of reproductive allocation patterns, consequently comparisons to previous reports are readily made. Second, although biomass and nutrient allocations have been found to be significantly different, a study based on biomass may still reveal the "essential patterns" of nutrient allocation (Abrahamson and Caswell, 1982). Finally, because of the ease of biomass measurment, more data collection is possible, hopefully providing greater accuracy without taxing those resources allocated to the researcher. I do not subscribe to the point of view that biomass measurments applied to reproductive effort is inherently inappropriate due to the photosynthetic capabilities of some of these structures as suggested by Thompson and Stewart (1981). The carbohydrate production in these tissues is 12 13 available to the whole plant's pool (Bazzaz and Carlson, 1979), and it need only be recognized that this production is present. While biomass units are used throughout the study and as I have indicated above, they may serve as our inital best guess of the gross nutrient allocation patterns, I heed Abrahamson's and Caswell's (1982) warning and in no fashion intend these results to be interperted as the nutrient allocation pattern of Acer negundo. Within this study, the following definitions will apply; reproductive effort refers to total accumulated biomass in reproductive tissues to the point in time indicated. Following the suggestions by Thompson and Stewart (1981), reproductive tissues include flower, seed and the supporting tissues up to the first encountered leaf or permanent branch. Foliage or leaf effort refers to the total biomass accumulated in leaf blade and petiole tissues, and vegetative effort refers to the accumulation of all non-reproductive biomass, i.e. the biomass in wood, bark and foliage tissues. Methods The methods used for the determination of biomass allocation to the various plant tissues are similar to the methods described by Whittaker and Woodwell (1968) and by Reiners (1972). The analysis and compilation of data for males and females were kept separate at all times despite 14 the fact the results were not necessarily significantly different. The number of flower buds per unit length of a branch or stem were counted in the spring of 1982, on trees in the Water Quality Research Area on the campus of Michigan State University. The basal diameters of branches were measured for the development of a regression of basal diameter vs. flower number. As the flowers of A. negundo are in racemes, one flowering bud consists of several individual flowers. The raceme is considered as the flowering unit throughout this study. As the season progressed, samples of the flowering buds were collected for the determination of dry mass. Samples of leaf material were also collected at this time for the determination of the leaf dry weight. During the later half of August and the first of September, 1982, trees were harvested for the determination of mass allocation to the vegetative structures of the trees. It is felt that at this period, prior to leaf yellowing, nearly all seasonal growth has been completed yet the physiological changes of fall senescence have not yet altered the biomass of the various tissues. In studies cited by Kramer and Kozlowski (1979) the period of the translocation of elements from the leaves to the stem corresponds to the period in which the biomass loss associated with senescence occurs. Zimka and Stachurski (1980) have found that in Acer negundo the translocation of 15 N, P, K, Na, Mn, Mg, and Ca occurs almost entirely during the period of leaf yellowing. Because the flower number counts were taken in the Spring while the remainder of the dimension analysis was conducted in the fall, correction of the branch diameter for one seasons growth was applied to the flower number per branch diameter regressions. Because not all racemes were found to produce the same number of flowers, a regression equation was used to estimate the entire mass of the raceme (including both the seeds and supporting structures). Five trees of each sex were selected for the dimension analysis. The criteria for selection of these trees were 1) that they were uncrowded; 2) single stemmed for at least 1 meter; and 3) had a suitable tree of approximately the same size of the opposite sex nearby. It is felt that by selecting the trees in pairs there is a smaller probability of microclimatic differences effecting the results of the dimension analysis. The trees were harvested in random order. The stems of the selected trees were first divided into one meter sections. Within each section, all branches were recorded for their basal diameter and condition (living or dead, new shoot this year or previously existing branch). One or more of the branches in each meter section were selected at random and sampled as described below. Once all 16 attached branches were measured and recorded, the diameters of the wood and bark were measured at the apical and basal ends of the stem section. This measurment was replicated three times along three different diameters for determination of the average diameter. This procedure was repeated in each meter section along the length of the stem of the tree. The upper—most end of the stem was considered to be the apex of the previous year's growth. Branch sampling was of a similar nature to stem sampling. The randomly selected branch from the stem segment was divided into meter length sections and all attached branches were measured for their basal diameter and condition (living or dead, and if they were branches of the current year). Sample branches under two centimeters in diameter were randomly collected within each meter segment of the branch and placed in labeled, plastic bags for transport to the laboratory. The leaves and any attached seeds remained attached to the branches. All branch samples from a particular stem segment were kept separate for analysis. As with the stem segments, branch diameters for the wood and bark were measured at the apical and basal ends. Again, three separate measurments being taken for determination of the average diameters. At this time, a subsample of the stem or branch wood and bark were obtained for the determination of weight/volume relationships. 17 Laboratory analysis of the sampled material was conducted within 8 hours of sampling. Leaves of the sample branches were stripped and leaf area per branch determined. Leaf area was measured on a portable area meter manufactured by Lambda Insturments Corporation (model LI—3000). The leaves, with petioles, were then dried for the determination of leaf mass per basal diameter. Branches were dried for the determination of dry branch mass per basal diameter. The samples of wood and bark tissue from the stem and branches were measured to determine their wet volume, then dried and weighed for determination of wood and bark densities. The data obtained from these measurments were used to calculate the regression equations for mass of leaf or wood tissue per branch basal and stem basal diameter. The mass of wood and bark in the segments was determined by first calculating the volume of each. Volumes were determined by the following equation: V = (1/3)*H(RA’ +RB’ +RA*RB), where V is the volume, H is the length (1 meter in most cases), RB is the basal radius, and RA is the apical radius of the stem or branch segment. The respective masses of each were then found by multiplying the estimated volume by the densities determined above. The density of the wood was not found to vary significantly with location in the tree or with sex. Consequently, the average wood densities were used (.5194 and .5138 G/Cm3for male and female respectively, Table A1). As stated earlier, the compiling of data for the sexes was kept separate at all times despite any lack of significant differences. However, 18 if these values of wood density were averaged, the result would be an increase in the difference in standing wood biomass shown in Figure 13. In contrast to wood densities, bark densities were found to be dependent on the stem diameter and regression equations were used to determine its density for individual stem sections. These regressions equations for male and female bark densities were not significantly different from one another (see Table A1 and Figures A1 and A2 for woodland bark density regressions). It was suspected and later substantiated that the leaf and branch masses from older, established branches would differ from the current year's leaf and branch masses. Separate regression equations were used to determine the branch mass for each branch diameter and leaf mass for each branch diameter of these new branches. Nearly all branches falling into this cataegory were found to be less than 2 cm in diameter. The regression parameters used for branch and leaf mass are found in Table A2 and A3 respectively. To calculate the estimated biomass larger than two cm, the masses of smaller branches were progressively added to build the larger branches on which they were found. The regressions for biomass were formed in a step-wise maner, from smallest to largest, forming six size classes (see Tables A4 through A6). In addition, in the smaller size classes, it was found that improved coefficients of correlation could be had by sub-dividing the trees into upper, middle, and lower levels (each generally about 2 19 meters in height). In this fashion, the regression equations were found to estimate the mass for branches up to 11 cm in diameter (larger than the largest branch encountered). The values of the slopes and intercepts of these regressions are found in Tables A4, A5, and A6 for new branch mass on existing branches, total branch mass, and leaf mass respectively. To determine the total mass of a tree, the estimated mass of all branches was added to the calculated mass of the tree's bole. This results in the final regression equations which estimate the mass per tree diameter. Slopes of male and female mass regressions were compared using the Student-t test (Steel and Torrie, 1980). Results For the whole tree vegetative tissues, the regression equations for male and female new branch mass and leaf mass are significantly different from one another. Females are found to have a greater mass of new branches for a given stem diameter than males (P<.05) while males have a greater leaf mass for a given stem diameter (P<<.001). The total wood and bark mass regressions were found not to differ significantly. Slopes and intercepts for these regressions are presented in Table 2. The regressions lines with data points are found in Figures 1 through 6. As seen in Table 3, the regressions equations for the seasonal growth correction of male and female branches did 20 TABLE 2. Regression parameters for above ground oven dry biomass. All dependent data were square root transformed. MALE FEMALE t TOTAL A -13.963 -13.296 WOOD & B 13.365 13.395 1.202 BARK r’ .988 .992 n 76 72 A -1.410 -1.067 NEW B 3.138 3.179 2.326* BRANCH r2 .950 .946 n 76 72 LEAF A -2.386 -1.134 MASS B 6.374 5.672 33.973*** r2 .973 .980 n 76 73 Mass = A + B*(Diameter) * P <.05 *** P (.001 HEW mmnz EDW mmnz H H H Mlfllflfid CM CO **' 4% ‘J C? Elfiflifilfl 5 film m N G B O G D 21 FEI‘1f-1'1LE NUDE) FIRES; a I. . Pu "FAM- fl‘d’f‘l air-‘- ,4 5’“ .PJ—FF-f 9 .~!-. I”? met ........ +|+|+|+l++ 6 1H 12 14 16 13 251 DI HNETEF! FIGURE 1. Relationship between female oven dry wood mass and stem diameter. The ordinate axis is the square root of the mass in grams. NHLE NUDE) P11543333 - lap-"P,- 15-" 0.-.?” P'F‘.’ an a Er'r'..- a an"! fir“ ...... e. lilililili E1 2 4 6 3 1'3 1'2 14 16 1:3 28 22 DIHMETER FIGURE 2. Relationship between male oven dry wood mass and stem diameter. The ordinate axis is the square root of the mass in grams. mm L") 0'! 11"}; EU: I) 370530) -' k [00333 CD - 22 FEI'li-"lLE HEM BRHHIZH Flt-"1.9352 [-1 in] h L0 IT: ’1 02' El :31! III IE! IS) (I) ..r l l l I l 1 l 1 I I II a H '3 l IS) I . l3 2 4 6 8 1E1 12 14 16 13 28 BI HNETER FIGURE 3. Relationship between female mass of new shoots and stem diameter. The ordinate axis is the square root of the mass in grams. :33-.. HRLE HEN EtRF'thtH MASS; ?E|-»- I! ’5": as..— f,- na __..-—" SEl-l— fan" ‘33,, 4‘3-1— _ I" a B'-}-" 313-..- " -_,.,- -a-JI I 26!-— 9‘59" pun-ff .......... I ......... + ......... | ......... + ......... I ......... + ......... I ......... l ......... l ......... l 6 18 12 14 16 13 2E1 22 DIAMETER FIGURE 4. Relationship between male mass of new shoots and stem diameter. The ordinate axis is the square root of the mass in grams. WILLIE-3 TlII-ITll'" 3333 III 0303133 TIE-"1|" IJEZIU'.) 23 FEl'lt-"iLE LEF-‘iF FIRES H rlJ 1‘33 J l 1934— . (,3 (Ln? ..... i .......... I .......... i .......... l .......... i .......... l .......... i .......... l .......... i .......... i' EIIHI‘IETEF! FIGURE 5. Relationship between female leaf mass and stem diameter. The . ordinate axis is the square root of the mass in grams. 1621—»— MF‘iLE LERF MASS 1 4 I34)— I 1 E: E1 3.. ref-ff 1 UB-L— . “#fy’.-« 813-— a “p.33“.- 6 E1 -70 cm circumference) show growth trends similar to the trees examined in the adjacent uncrowded area. In this size class, female mean ring widths are significantly greater than male ring widths during the interval from 1978-81 (P<.05, F: 4.75). The next two smaller size classes (60-69.9 cm and 50-59.9 cm in circumference) indicate a trend of increasingly greater male ring width relative to the female mean width. In the 50-59.9 cm size class the mean male width is clearly greater than female width though the differences are not significant. The three smallest size classes (40-49.9 cm, 30-39.9 cm, and less than 30 cm in circumference) all indicate essentially equalivent male and female growth. The mean ring widths for females in the smallest size class becomes somewhat erratic probably due to the small sample size (n = 5, see Figure 27). An analysis of variance was used to examine the effect of tree size on the annual growth ring width of the three largest size classes in this stand. A split plot design was used with sex and size class as the whole plot factors. The split plot factor was the year of growth for the years 1978 through 1981. As can be seen in Table 9, the size class and year in which the growth occurs has a significant effect on the annual growth ring width. Ring width increases as both the size class and the year of growth increases. The sex of the tree, as a single factor, does not have a significant effect 52 TABLE 9. Analysis of variance of growth in closed canopy stand. SOURCE DF MS F Sex 1 26.597 1.43 Size class 2 76.069 4.08 * Sex X Size 2 104.375 5.61 * Error 42 18.62 Year 3 75.91 14.71 ** Sex X Year 3 .57 .11 Size X Year 6 3.18 .62 Sex X Size X Year 6 1.94 .38 Error 126 5.16 * P <.05 53 on annual ring width within the stand. Of the four possible interactions only the sex X size class interaction is significant. As stated above, in the largest size class females have greater ring widths during these years while in the two smaller classes the male ring width becomes relatively greater. Discussion Sex Ratio Despite natural selection for a primary sex ratio of 1:1 (Shaw and Mohler, 1953; Hamilton, 1967), skewed secondary sex ratios, as observed in this study, are not uncommon among dioecious species (Grant, 1975; Freeman et al., 1976; Opler and Bawa, 1978; Grant and Mitton, 1979). Lloyd and Webb (1977) cite reports that indicate Petasites japonicus, Myrica gale, Diospyros melanowylon, and Dodonaea visocsa have male biased (often significantly) sex ratios. Meagher (1981) reports that populations of Chamaelirum luteum are always found to have a significant excess of males. In other species a female biased sex ratio has been reported. These include Borassus fabellifer, Potentilla fruticosa, Silene alba, Rumex acetosa, Cannabis sativa and Triplaris americana (Putwain and Harper, 1972; Melampy and Howe, 1977; Lloyd and Webb, 1977). In several cases of female biased sex ratios, the cause is attributed to differential pollen tube growth. The pollen tubes bearing both the X sex chromosomes, the female 54 determining in these species, are found to have greater elongation rates and consequently fertilize more eggs than the male producing pollen, bearing the X and Y sex chromosomes (Heslop-Harrison, 1972; Werren and Charnov, 1978). The cause for at least some of the male biased populations appears to be due to differential survival of the sexes (Lloyd and Webb, 1977). Lloyd and Webb (1977) cite several examples of increased male bias with population age. The differences in male:female survivorship are shown to be at least in part responsible for the male biased sex ratios in Chamaelirium luteum (Meagher, 1981). This has been considered as circumstantial evidence supporting Darwin's hypothesis of increased female mortality resulting from greater reproductive demands (Lloyd and Webb, 1977). Size Relationships Differences in the size of male and female individuals in dioecious species has frequently been reported. Rarely however has the difference in size been found to be significant in woody species (but see Grant and Mitton, 1979). In the Michigan Acer nugundo populations examined, females were generally found to have larger mean basal areas than males. In fact, the probability that 8 of the 10 populations looked at would have greater mean female basal area if no differences existed is less than 10% (x’: 3.6). When all observations and data from previous reports are considered, two main hypotheses accounting for the differences in gender size emerge. The first, is that males 55 and females do in fact grow at different rates. Generally it is expected, and often found, that males will increase in vegetative size faster than females, presumably due to their lesser resource requirement for reproductive functions (Lloyd and Webb, 1977). Despite this, in some species it is the females which are found to be larger and grow faster (Grant and Mitton, 1979, Lloyd and Webb, 1977). The second explanation which frequently emerges and has been shown to account for the differences in at least one instance (Meagher, 1981), is that there are different mortality rates for males and females. Females, because of their greater reproductive effort have a higher mortality rate than comparable sized males. Consequently, the size distribution is skewed in favor of larger females while at the same time, the sex ratio becomes more and more male biased. Growth Rates The data gathered on the growth rates of mature isolated trees suggests that growth rate is responsible, at least in part, for the size differences encountered in the populations of Acer negundo. For a class of individuals of the species growing under comparable conditions but at a greater rate, while investing substantially more resources toward reproduction than another class, raises more than a few questions. Some possible explanations for the cause of growth differences as well as other secondary sex character have been offered by Lloyd and Webb (1977). These possible causes fall into three categories of control; genetic, 56 physiological, and adaptive. Causes of secondary sex characters which can be attributed to the accumulation of specific genetic differences in the differential segment of the sex chromosome are considered genetic. To date, no evidence of direct genetic control of secondary sex characters has been demonstrated (Lloyd and Webb, 1977) Physiological mechanisms are those which control the development of secondary characters through the physiologic byproducts of the primary sex functions. A possible example of this type of control, suggested by Heslop-Harrison (1972), is that females posses high auxin concentrations while males contain high levels of gibberellins. High concentrations of auxins are known to inhibit bud development (Bidwell, 1974) and, if present, may in part be responsible for the later bud break in females. Gibberellins on the other hand are known to effect growth, are involved in flowering and bolting, and also interact with various other hormones (Bidwell, 1974). Another physiological mechanism may be the stimulation of photosynthesis by a strong and persistent resource sink (the developing seed) in females. Stimulus of photosynthesis and the subsequent carbohydrate formation and its export has been shown to significantly increase when strong sinks are present (Thorne and Koller, 1974). The creation of carbohydrate sinks in Glycine max L. resulted in a 50% increase in carbon dioxide assimilation. The stimulation may be sufficient that 57 significant increases in total plant carbon assimilation are possible. Lloyd and Webb (1977) divide adaptive explainations for secondary characters into five facets which are defined by the role each sex plays in reproduction. These catagories are: 1. adaptions for pollen transfer; 2. food availablity for animals; 3. time required for seed and fruit maturation; 4. reproductive effort; and 5. seed release and dispersal and seedling establishment mechanisms. If males were to grow taller, as in some dioecious species (Bourdeau, 1958), but not found in Acer negundo, more effective pollen dispersal may be possible in an anemophyllus species. Females are burdened for substantially more time than males in their reproductive functions, consequently, females may be more susceptible to environmental hazards and have an increased likelihood of death (Freeman et al., 1977). Reproductive effort in 4 species has been demonstrated to be greater in females than males provided there is a minimum seed set. The possibility that females could also have a greater vegetative effort than males in an interoperous species with persistant shoots is not even considered by Lloyd and Webb (1977) and puzzles Grant and Mitton (1979). The degree of supression in a dense stand such as the one examined, increases for the relatively smaller individuals within that stand. Thus, in this population, the largest size class is least effected by the supressive environment created by the closed canopy. In progressively 58 smaller size classes the degree of supresssion rises. Because of the these interactions, the relative ability of males and females within a size class to garner resources in stressful conditions may be inferred from their growth. When stress is slight, as in the largest size classes here, little effect is seen on the relative growth (and presumably vigor) of the sexes when compared to isolated trees. In the next two smaller size classes, in which stress may be expressed as moderate, male growth is significantly less supressed and exceeds female growth. From the significant Sex X Size Class interaction, one may conclude that males relative to females, have a superior ability to garner resourses in moderately stressed situations in which light and or spce are the limiting factors. The smaller size classes, in which supression is severe, indicate a lack of difference in the response of the sexes to severe light limitation. The growth responses for these three factors whithin the closed canopy stand may account for the difference in results between this study and the previous report by Lysova and Khizhnyak (1975). At least two of their study sites had tree densities up to 8 times higher than the 800 trees/ha in the closed canopy stand studied here (see Table 1). Their third stand with a reported density is roughly equivalent to the closed canopy stand here. Consequently I view their results as being highly influenced by the sexe's differing responses to light and space stressed conditions. 59 A consistent pattern of reduced seasonal growth can be seen for the year 1981 in all mean ring widths for both the crowded populations (Figures 22 through 27) and in the uncrowded trees (note the typical mean in Figure 52). That this is a seasonal deviation for the one year only is indicated by the return to a smoother growth progression in 1982 by the uncrowded trees (Figure 52). Presumably, this reduction in growth has been caused by some climatological stress during the 1981 growing season or during the previous winter. The relative decrease in ring widths between males and females was measured by the percent decrease from the 1980 ring width. The average male ring width decrease, 19.4%, is 7.4% more than the average female ring width decrease, 12%, a nonsignificant difference. Precipitation or temperature seem to be the most obvious environmental factors which could potentially effect tree growth. The deviation from the monthly record mean precipitation and temperature for the years 1978 through 1982 is shown in Figures 28 through 37. These data were obtained from the National Weather Service Station located at the Capitol City Airport, Lansing, Michigan, approximately 15 kilometers from the study site. From the graphs, there is no indication of a severe drought period in the 1981 season. Temperatures also appear not to deviate from the mean temperature to a degree which '2 ._: NILLIMETEE' 3". ('__'0 (fl REE 1 L: DE 60 '13” .315 M H M .5 j H é: u N f: - DEU. FROM MEHH FIGURE 28. 1978 monthly precipitation deviation from the mean. 1 973 TENF’ERHTUR‘E 1.11 .3. GM -6'jFfiémtTtIfiéCINII MONTH - DEU. FROM MEHH FIGURE 29. 1978 monthly temperature deviation from the mean. D MILLIMETER“ DEGREES (C) 61 1979 PRECIPITHTION 5” J F M H M j J H s O N O MONTH ll DEU. FROM MEHN FIGURE 30. 1979 monthly precipitation deviation from the mean. 1979 TENPEEBTURE ”6 J F M H M j j H MONTH I DEU. FROM MEHN FIGURE 31. 1979 monthly temperature deviation from the mean. NILLIMETEES 62 J 9'31?! PRECIJPJTHTIDH Mur I new. FFJCIM MEHH FIGURE 32. 1980 monthly precipitation deviation from the mean. JFMHMJJHéONfi _ MONTH I DEU. FROM MEHN FIGURE 33. 1980 monthly temperature deviation from the mean. ~Z' MILLIHETER DEGREES (C) 63 1931 PRECIPITHTION ”13“" .3 F M H M .j J H E O N f: MONTH - DELI. FROM MEHH FIGURE 34. 1981 monthly precipitation deviation from the mean. 1931 TEMPERHTURE J -..TFMHMJJH:§ONO MONTH I DEL). FROM MEHN FIGURE 35. 1981 monthly temperature deviation from the mean. MILLINETERS ct) - \- DEEREE' 64 -1338. ............................................................................................................... "13” J F M H M J J H O O M O MONTH - IIEU. FRCIM HEHH FIGURE 36. 1982 monthly precipitation deviation from the mean. NI 13 IT- ‘5' “5 J F M H M J J H O O N n MONTH I DEU. FE‘CIM MEHH FIGURE 37. 1982 monthly temperature deviation from the mean. 65 could result in the observed ring width decline. One possible temperature related cause for the decreased growth in 1981 may have been the above normal temperatures in Feburary, March, and April followed by the below normal temperatures in May. The deviations in any one of these months are not to the extent that they may alone be stressful, but this observed pattern may have promoted an early break in dormancy, followed by damaging cold temperatures. There is no sure knowledge that this is in fact the environmental stress in 1981. Freeman et a1. (1976) has suggested that in Age; negundo, the sex ratio shifts significantly at opposite ends of an ecological gradient. Females are found to be in greater abundance in areas of higher moisture. A preponderance of males were found on hillsides where moisture stress is presumed to be more frequent and extreme. The habitat dependent sex ratio suggested is felt to be due to disruptive selection. During periods of environmental stress, the smaller resource demands of males relative to mature females developing seed, is suggested to cause differental survival (Freeman et al., 1976; Freeman et al., 1980). If this is the case, one would expect females to have a greater response to environmental stress, even on a seasonal basis. This was not observed for the 1981 growth of A, negundo in the study site. Grant and Mitton (1979) found biased sex ratios in Populus tremuloides are related to population position on an 66 ecological gradient. They found that females were in the majority (56%) at lower elevations but in a minority (36%) at the higher elevations. In the festucoid grass, Hesperochloa kingii, Fox and Harrison (1981) found a similar habitat assortment of the sexes. However when attempting to find a physiological mechanism, they found insufficient difference in plant water potentials to account for the observed habitat assortment. Consequently, they question the disruptive selection hypothesis put forward by Freeman et a1. (1976) in favor of adaptive sex ratio theories. Assuming that some, as yet undetermined environmental stress has resulted in the ring width reduction it is supprising to find at best no difference in male:fema1e response and perhaps even greater male response to environmental stress. It is interesting to note that in several species, males have been found to be more vulnerable to environmental stress than females (Werren and Charnov, 1978). If the 1981 stress had been caused by the early bud break followed by damaging cold in May as suggested above, the slight difference in stress response may be explained by the differences in seasonal phenology (see below). Males break bud slightly earlier than females, consequently a damaging cold shortly after the initation of growth might be expected to harm the further progressed males more than females. Late frost damage was observed to cause greater 67 damage to the emerging male inflorscence than to the female structures still contained within the buds in 1983. PHENOLOGY AND RESOURCE ALLOCATION To more accurately assess the allocation of biomass resources at any one point in time, this section describes the seasonal phenology of each gender of A, negundo and couples this with both the gender's growth rate and standing mass allocation pattern. Through this coupling, an estimate of the seasonal biomass production in wood, leaf and reproductive structures may be made. As timing has been suggested as a potentially important aspect of a gender's allocation strategy (Gross and Soule, 1981), mass allocation to leaf and reproductive tissues was followed throughout the season. Methods The accumulation of biomass in vegetative and reproductive tissues during the early seasonal growth of Acer negundo was followed in the Water Quality Area, N. population (site #4). The tissues in these samples were divided into two classes depending on their function (vegetative or reproductive). The vegetative tissues developing from the terminal bud were measured separately from those tissues developing from the lateral buds. The lateral bud vegetative tissue was futher divided into two catagories dependent on its position in relation to an inflorscence. These classes are refered to as associated lateral buds (i.e. with reproductive tissue developing adjacent the vegetative tissue) and unassociated lateral 68 69 buds (i.e. those without adjacent reproductive tissues). The reproductive tissues, as defined earlier, developed from the associated lateral buds. To estimate the mass accumulated in reproductive vs. vegetative tissues within the closed bud prior to May 2, the total mass of the bud was divided into reproductive tissue mass and vegetative tissue mass in the same proportions as found on May 2nd. With the application of the growth rate regressions and the dimension analysis regressions, the seasonal above ground biomass allocation may be estimated. Estimations are made for apical tissues (tissues originating from the shoot apical meristem, e.g. the current seasons twig growth), cambial tissues (tissues originating from the cambial meristem), leaf tissue and reproductive tissue. As the stage (size) of an individual has been found to be a better indicator of plant development status than age in Dipsacus sylvestris (Werner and Caswell, 1977) the primary results presented here are for standarized (each tree 10 cm in diameter before the growing season) male and female trees. The age of the trees (determined from the growth regression) is not the same (9.99 years for the male vs 9.41 years for the female). Seasonal allocation of resources is also estimated for individuals within the same age class, each during their tenth year of growth. One difficulity which arises when considering the allocation of resources is to what extent the current year's development is supplied by resources stored from previous 70 years. In A. negundo this problem would probably most effect the estimate of male reproductive effort since the majority of male effort occurs at a time in which resource production (carbon assimilation in this case) as at low levels. Rather than attempt to proportion the mass production into categories based on whether supplied from stored or newly acquired resources, all biomass is assigned to the season in which the tissues become fully developed. Results Seasonal Phenology The seasonal phenological development of the sexes of ‘A. negundo is significantly different. Prior to the initation of spring growth, differences in the bud size of males and females are readily apparent. Males were found to have significantly greater bud mass than females (P<.05, Table 10). As spring growth commences, males accumulate mass in their buds, prior to bud break at a greater rate than females. The buds of males were observed to begin to break on the 17th of April, 1982 while the buds of females did not open for another 3 to 5 days. At the time of male bud break, the mean lateral bud mass of males was 380% greater than the mean female bud mass (Table 10). Following bud break, male flowers, which had already reached 55% of their maximum mass, developed quickly. The maximum biomass accumulated in male flowers occured just prior to anthesis, approximately 15 days after bud break. After anthesis, the entire male inflorscence rapidly withered and dropped from 71 TABLE 10. Mass accumulation in spring growth SAMPLE DATE 4/17 TERMINAL BUD MASS UNASSOC LAT BUD MASS TOTAL ASSOC BUD MASS ASSOC ## LAT BUD (VEG.) LAT BUD (REPRO.) 1.61 8.26 3/31 4/11 9.94 10.67 (.58) (1.03) (10) (10) 7.53 9.88 (.84) (1.36) (10) (10) NA NA NA NA 9.38* 15.06* (1.15) (1.25) (20) 3.58* (.26) (20) 1.41 1.71 7.97 (20) 5.06* (.63) (20) 2.26 2.41 12.80 15.16 (1.30) (10) 12.79 (10) NA NA 23.71* (1.23) (20) 6.24* (.79) (20) 3.56 2.98 20.15 4/22 5/2 5/12 15.19* 64.03* (1.84) (5.65) NA (10) (19) 20.37*112.92* (1.72) (3.07) NA (10) (12) 17.2 NA ( 1) NA 29.60 49.84 NA (2.23) (2.49) ( 7) (13) 36.42* 48.57 43.31# (1.84) (20) 10.48* 45.19 123.56 (.75) (20) 5.47 7.30* 43.31* (2.25) (2.61) (17) (30) 5.00 21.55* 25.48* (3.24) (2.65) ( 6) (26) 30.95 41.27* NA (2.98) (30) 5.48 23.64* 98.08 (2.67) (6.47) ( 6) (25) * Indicates that the respective measurment for the opposite sex differs significantly with 95% confidence. # Male total bud mass of 5/12 is vegetative tissues only ## The distribution of vegetative and reproductive tissue mass prior to 5/2 was calculated by the veg:repro mass ratio found on 5/2 for each sex 72 the tree. At anthesis, the mean mass of the female inflorscence was only 57% of that of the male reproductive structures. Shortly after pollination, females dropped their stigmas, the only mass loss noted in the developing fruits. Mass accumulation in the developing female reproductive structures then increased rapidly for the next few weeks of the season (see Figure 38 and 44), reaching 87% of the maximum mass by early July. A small, yet significant, decline in reproductive mass occured in the fall after leaf drop (a 16% loss, P<.001, Figure 44). The development of vegetative tissues from terminal buds did not differ significantly between males and females prior to bud break. At anthesis females were found to have significantly greater biomass in terminal bud tissues (P<.05, see Table 10, Figure 39). The sample size for lateral buds without associated reproductive structures is quite small (n=7 for females and n=1 for males) at this sampling date. Vegetative tissues which developed from buds which were in association with reproductive tissues were found to differ significantly in their mass and the rate of mass accumulation between males and females (see Table 10, Figure 40 and 41). Prior to bud break, vegetative development in males occurs at a slightly greater rate than in females, although the masses are comparable at this time. During the period just prior to anthesis, when male reproductive demands are :'sn'Lr"!:' 1 21.2. ;—:e£ 517w." ’~:-L 95.59." :15.— ; . “0-er *1 .2393} 13.-e =2”: 1 ”Greer: but. f--.‘!-., - 1' 1.03 sale «Dianna " - «'11 86:11:31)“: ow 7I'JU71I‘1 - 1. . . . _ affii-M (uni-m 16? 1...: .. .' p L i 6688: 8613.. W9!) :16: m :9: . . .2“. (ml: : m *8” mitifmzqwx (1 (w 3 .- a . ram (25% mmm‘ms n.‘ vlui»;-i-.—.»._ warm (.3: y .1 ' W 0M”? ”5“? Eu; “(gm w-m‘m.‘ 6*."6294-1933 “I: --‘ , : . . 2 <2; -. .4») 3.». u") 1 ‘ :f I '5 , u; I ‘jWth M 6m: 61 ma! (I... :. w T. '- _.‘f.. . . :' ‘ ,, : . : g);-...;;;l,.. .21: - W *W”“ m ”"9- * ' T; i) 1;); .5 ,. 17:33:; . .wmw - ~= '- MESS Una] 0-!- 73 FLONER DEUELOPMEHT BB ""' 1:. SBH- M 1 SIB-(- II: '1 261—— _. g 1' .- U +9 " uB-H at c . L c; I 5):.) -1- D 4‘,- .1 413-1— 3 .' 1 33—1— ‘3 .. 226-4 ' "‘- 151 a.“ ' FEI‘IF‘LE B j::::::::::::::::::':::::::::IZZI223.1232:IIIIIIIIIIIIIIIIKI ........... ( .................. I .................. .I, 3 23 3 31 4«"'11 4” 7’ 4’55. ”‘7 2 5. IE. SQNPLE DHTE FIGURE 38. Spring mass accumulation in reproductive tissue. ;, -. l '- '~T 3'3 + : ‘31": '3 -’ '3 m“: 301 Ma r. ..;.'.az , .‘.q. ." Haw-n": .903“: r- :v‘wwwa‘ .1! WUFDE 03 74 123__ TERMIHHL BUD DEUELDPMEHT 133—— FEMHLE sa-— eu~— % “ W .5 4‘3"” T1.fl s g .D '. 29-— . g " “lily—B D MHLE .§ t3 ...................... I ...................... ’ ...................... I ...................... ' ...................... +. 3*”27 3a"31 4,-"11 4 17 4 2:2. 5"”.5.’ SHNF’LE UQTE FIGURE 39. Spring mass accumulation of tissue developing from the terminal bud. i” \‘usrttfite av.“ :,- Hm . 31" an: a?“ or up; M933 hug]- MB PER DH? DEP‘HNNHH M IL." I Ci! N m hJ-d N «Ira-q m .4 L" 75 45__ REPRDDUCTIUE LERF DEUELDPMENT 43‘” .fl 35%~ $ .1: 381— fi 25-b- x 3 u. ..... rf' P U 4... d6 . T" L 157 13d 5-4 G 3 "2:3 3”"31 4111 4rd? 4/’22 53/2 5’12 SRMPLE DQTE FIGURE 40. Spring mass accumulation in leaf tissue associated with reproductive tissue. REF’FLU. FOLIHG‘E GRDHTH RFITE m M U! UIUI 1 2 3 ‘4 E 6 SfiMPLE PERIOD - MHLE FEMHLE HE! FIGURE 41. Spring mass accumulation rate of foliage associated with reproductive tissue. The sample periods correspond to the sampling intervals of Figure 40. . Ahvuflhf , ‘.IU.~I‘ ‘ I 7 »~ «c.1' » ---.. - 76 at their peak, the rate of vegetative development in males drops 52% while the rate in females increases 410%, 9 times that of males (Figure 41). In the period following anthesis, when reproductuve demands have dropped to zero in males and demands in females are increasing exponentialy, the respective rates of vegetative development are reversed, the male development increasing nearly 2000 times to 9 times greater than the female rate which has droped 76% from the previous period. At this time, the actual mean biomass in vegetative tissues is 43.3 mg per bud and 25.5 mg per bud for males and females respectively (Table 10, Figure 40). Seasonal Allocation Seasonally, females in the same size class accumulate greater biomass than males. The distribution of this mass (see Table 11 and Figures 42 and 43) is such that in all catagories of plant tissue with the exception of foliage, females accumulate more mass than males, however only in reproductive tissues do females allocate a greater percentage of their total plant effort. The accumulation of resources in reproductive tissues is strikingly different from the pattern of allocation to vegetative tissues. The accumulation of biomass in reproductive tissues through the season is shown in Figure 44 for male and female trees, each 10 cm in spring diameter. The maximum rate of accumulation of biomass by males is 11.4 grams per day per tree and occurs just after bud break (Figure 45). Male reproductive effort is considered to end JP.) .~:! .. . v- "; 1 ”HQ"? ,,.-. 5 ~.' aubm aid?) lo "a: .miicl 1c- ma‘i :n r a?" 1.51m :19th (39--m ;171. nu£*u“fipu ad" a -: . 9 Handy u'5ialfii id? 1! .n-. ~ nr #20? .gnilsvrtwk “ f. 1; , . a} wvifau . wvxioabpxfidi aihu’} tan 3 1L ; "' 93 :: eooanjoi. 91'3- ‘Ib‘h m z-Mum: a M rot-s- 3 hes-3r! up! . ‘- MW tam m’fi ahWWd hip": r ‘ -. «a vase; Room: {YUI§’Y#F§‘ figfi filflfifi 13'! ..19 *e .sm~- 9 -%T0? ‘ 7’ 1 I“ «dig!» fim hm» @902»; any» . an M) <§¢ghggflfliflb¢ Econ stud “swoon laal ”-’Q 1 .‘J. - 1‘ :h ..; #~.-:;:21_ 82 inital slow development of vegetative tissues is not thought to account for the size differences found in A, negundo. The ’greater reproductive effort put forth by females at this early date is unlike Silene alba, in which females only surpass male reproductive effort late in the growing season (Gross and Soule, 1981). In In only two other species has the pre—anthesis mass of male and female reproductive structures been compared. In Silene alba, the female's reproductive effort of flowering alone is approximately 2/3 of male reproductive effort (Gross and Soule, 1981). Females of Simmondsia chinensis have a reproductive effort of approximately 1/20 male effort when there is zero seed set. The pre-anthesis reproductive effort of females in Acer negundo is 1/4 of the male effort, between the herbaceous perennial and the desert shrub. The differences between males and females indicated above undoubtly reflect physiological differences in the sexes. Differences between the photosynthetic capabilities of the sexes have previously been described by Bourdeau (1958) for Populus tremuloides. He reports that the female net photosynthesis though not significantly different, is 10% less per gram fresh weight. Although the net photosynthesis was not statistically different, significant differences were observed in respiration rates. Females were found to have a 37% higher respiration per gram fresh weight. Physiological differences in the photosynthetic mechanism of Acer negundo are indicated by greater leaf area .r . 4 ‘ o ,. 1‘ _. .1 ,§ r f"; "if.“ «.r 1 fwsrfisn-L .55...3trvc'. . 1; ‘4. 9d! at m129':2‘_‘ ' :iniims usierzflu'mpyr .11. 4" 0W ‘6 bad; ; zest. .19?- 3%! NIB ”1 6153043? w .1; 8i .3. “‘38 whactlnnp’a 11,. fl-s a 43. v5pWi-A 335‘ W M 9’31")“: .21 3137-”: 61!} 1:; “sum: "‘7‘," 1; I ‘16 mt! fits”? to» d an: 3 129“ q It 1 m ,h "new "' ' ~- : Juanita .tOBI‘ . ’4' .‘ 3,.m, atwm' , ‘l si‘t’ TIE; 1 “-‘*£ . .'- 3W“, bmn“ '13-: 9'5: ‘QIJ.3|I}(1(: ‘JI .; 4"} ”’3": M1". . 1‘37".“ it; 15:1).yolai M ' p_ ' 3 , - ALE-t ‘ . i v " I» , r5099” ‘ f n ._ 1‘ rj-' I ."V r *1“ '..-' m1; J 7'1", "3. I"; 1. z‘ “0" 83 in females despite their relatively lower biomass in foliage tissues. Previous studies have shown that A. negundo, as well as other dioecious species, have differing concentrations of biological metabolites in the foliage tissue (Kotaeva and Chkhubianishvili, 1978; Kotaeva and Chkhubiamishvili, 1981). While these researchers found no evident differences in the content of lamellar proteins in leaf tissue, they report that females of the several species studied generally have greater total proteinaceous nitrogen than males. In addition to differences in the concentrations of certain elements in the leaves of Simmondsia chinensis, Wallace and Rundel (1979) also found the surface morphology to differ between the sexes. They found females to have lower densities of leaf hairs than males, but at the same time the individual hairs tended to be longer in females. With this in mind, the surface morphology of Age; negundo was examined. Preliminary examination indicates that females may have more trichomes, on both leaf surfaces, than males (Figure 46 through 49). Sex related differences in leaf morphology in §, chinensis and 5, negundo may be the rusult of a sex-related adaptation to different environmental stresses. While females of g, chinensis may be adapting to increased resistance to minimum terperature extremes (Wallace and Rundel, 1979), females of A, negundo may be specializing for water conservation or increased carbon assimilation (see below). “ 2233*; _ . ”If: . . .. .mé "‘ ‘ I 1‘ “A 4'1 Lfifvm fimfid 941 ‘. 2) :‘;:,,».,m’. .3, 5 ' _. 922119.22. .2. r2 —‘ . ' ' ”final!" ”If: aajrv.‘ ; w W n: 1‘ Janet“. 'm. 1 it“; «e.gocnrre-fi'ev. my: I. , ,u . a w m .LTM-‘r‘hbli .7} 23.: ' "3;:1’l' 1‘ _ 1;. r, . 1w; " ai‘fi’q.hfliiflfi 3‘I¥OH‘ b :3 r¢,: ;.Qfl na 31- -$!I ‘: a: My; git w: “W :3 :c, wan-r. . . em .l‘ I” ,M 4va 84 FIGURE 46. Upper leaf surface of u 17. Upper leaf surface of t 85 86 FIGURE 48. Lower leaf surface of male. 216033 49. Lower leaf surface of female. 87 88 If there are, in fact, differences in the photosynthetic physiology between males and females, one may be more efficient relative to the other. Although photosynthetic efficiency is generally expressed as assimilated carbon per unit absorbed light (Bidwell, 1974), the data obtained in this study allows the expression of photosynthetic efficiency in two different units which provide insight into the manner in which energy is utilized. The first of these is the annualy produced biomass (a measure of carbon assimilated) per unit of biomass invested in photosynthetic tissue. The second expression of photosynthetic efficiency is the biomass annually produced per area of photosynthetic tissue. These are two fundamentally different measures which may represent different strategies in the production of photosynthate. Figures 50 and 51 show the photosynthetic efficiencies of males and females by these two measures. In terms of the return on their investment (Figure 50), female photosynthetic efficiency is 35% greater than the male photosynthetic efficiency. For each unit a female invests into photosynthetic tissues, there is a net profit of 1.5 units which are available for other plant functions. Males on the other hand only have a net profit of .8 units per unit invested. When the efficiency is expressed in the second form, as return per area of leaf surface, it is the males which have a more efficient system. For each square meter of 'territory' covered males have an income of 171 grams of carbohydrate produced while female income is 147 . . c. I . .2 I I l ' I V 2 2 1 a , y » V if ' .0- ‘ H, ‘ ellele miewel a i!rr:.r 19 10' ' Q ' l. ) K ‘F . ,gi’._. P.‘ in #:Seuq "an s a; 3:37; i “Matty P ‘ 2‘ 4"!“ n, 2 ‘ firm—i? ‘(0‘ n? -" 1‘ - xii-am =43; .zmu? ."‘h!“.’.‘ f' I g4“" _ “f" are!“ -Ofl¢13fiflv9 inn!" 1~%"w we? I“; x -~; .-. ;;fm a: ' V _ . I “j 1.”;'2_ seq satay 3. to alianc fieu r *1.’ a 7 'n2 '-x!r $43 r—Lf. ‘ to!” at WW dz? Vermin?“ .4 54* z -. y .2; -.='~.-.-,2. :1 3:. mm a: gun m u. - 8.". "3'1“. RHM an ctr} _.r BRHM (q C}: RfiHC-,..-METE .. J 89 F'HCITCIEi‘r'NTHET I C EFF I C I ENCI‘r' - MHLE FEMHLE FIGURE 50. Seasonal mass accumulated per photosynthetic mass investment. PHUTCIEI‘r'NTHET I C: EFF I C I ENCZ‘I' - HHLE FEMHLE FIGURE 51. Seasonal mass accumulation per leaf area. 90 grams of carbohydrate (Figure 51). Males are 16% more efficient on an area basis which may have important population effects. As previously indicated, males are less responsive to stresses created by crowding. One possible explanation for this may be that in such situations, the ability to more efficiently use the space one occupies is more important than receiving a greater return for biomass invested. Consequently, male productivity would increase relative to female productivity in these situations. The previous calculations consider the foliage tissues as the only photosynthate producing structures on the plant. However, the samaras are probably photosynthetic (indicated by the presence of chlorophyll and stomata) and undoubtly contribute to their own photosynthate requirments. The reproductive tissues of Ambrosia trifida have been found to supply nearly 50% of their carbohydrate needs by their own photosynthesis (Bazzaz and Carlson, 1979). If the extreme case in which seed development is totally reliant on the photosynthetic capacity of the samaras, i.e. it is independent of the vegetative portion of the plant with regard to carbohydrates, and discount the seed mass in the efficiency calculations, females are still 12% more efficient in the biomass return per biomass investment while males become even more efficient, relative to females, in the return per area occupied (Figures 50 and 51). Interestingly, when one compares the proportion 'disposable' tissues (those produced and annually shed, i.e. 3"..7 WH’fl- w ‘ ,4 ‘ . : f ii‘ I ’61: ‘ ‘-1‘-r_¥"‘ . - ‘ ' ’1 :‘.V' | "1.5 2' «r. inn-1.; "2:.“ .'“1' “w"; '. x 3......- ci (ac-Hm! oz: 2.9::830‘1 .ias;o:§!~ rs‘xr‘a‘. n: 2...»..an an!" Pawn um...» um n2 «muff «‘32-:‘3 )7 1', 332321.141; 91 foliage and reproductive tissues) of the total biomass accumulation, the male (56%) and female (57%) allocation strategies are comparable. Of course variations from the norm are always found when dealing with biological systems. One individual on the sample site was conspicuously different from the remaining population in its distribution of resources to vegetative and reproductive growth. In 1982 the reproductive effort of this individual had all appearences of being well above any other female. From seed counts, the biomass in reproductive tissues is estimated at being 146% greater than a typical individual of its size. While the reproductive effort was high, vegetative efforts appear to be at a minimum. The leaf biomass was visually estimated to be, at best, 5 to 10 percent of a typical individual. Ring widths also indicate greatly reduced vegetative growth. Ring widths from the years 1980 through 1982 are substantially less than the mean of the sampled females (Figure 52). In contrast, during the preceding 2 years a pattern of accelerated growth, indicated by greater than normal ring widths during the years 1978 and 1979 is seen in Figure 52. This has been observed previously in trees prior to their senescence and death (G. Donnely and J.R. Dougle, personal communication). No evidence of similar high reproductive effort prior to death in trees or other iteroparisous plants is known to me. There is no evidence of externally caused stress to this individual. It is relatively uncrowded so that shading c- MILLNflETERn 92 141-.MERH RING NIDTH-FRDLIEIc TREE 12—_ .fl PRULIFIC.3 2 19-- . . . . '9' ' # 3.4.. . . . . . . . . . .,.".' . .h..:‘,..o"!"'-.n.h . a“ 3'... . may”. “'....,.....I‘- U. T'T.F.;'I CF”. 6-... . ..... 3' """" .4 ........... j-l .. I """ . . . I . . . . . flfixmmm ....... q ...... ' 4.4L. . I . I g .............. FIGURE 52. Growth of the prolific tree from the WQA N. site. 93 is only slight and not likely the casuative factor. There is no evidence of disease or mechanical damage to the tree above or below ground. However the tree is dying. During the 1983 season much of the previous years growth was found to be dead and only an estimated 10% of the branches carried foliage. It will be supprising if this individual survives through the 1984 season. The only explanation for the abnormal growth of this individual is that a physiological imbalance exists, causing massive reproductive efforts at the expense of vegetative growth and probably survival. The expenditures to vegetative and reproductive processes have lost their "functional harmony" as expressed by Williams (1966). In effect, the tree is apparently commiting reproductive suicide. "-r" Halli“ ' , 9 ?CI ‘0 2 ‘ vl‘L‘J' 953 SUMMARY The following ten points summarize the results of this study: 1. Staminate and pistillate individuals of Acer negundo differ significantly in their distribution of standing biomass to wood, foliage and reproductive tissues. 2. These differences are not apparent from simple examinations of an individual's height, spread or volume, measures which have been used in previous studies. 3. Males consistently outnumber females. Among all populations examined, the sex ratio significantly departs from 1:1. 4. Males become reproductively active at a smaller size than females. 5. Mature uncrowded females grow at a significantly greater rate than mature uncrowded males. 6. Juvenile (pre-reproductive) male and female trees were not found to have significantly different growth rates. 7. Females show a greater response to moderate levels of stress. 8. The seasonal phenology of the sexes is significantly different, males commencing growth earlier than females. 9. The sexes differ significantly in their seasonal 94 .3. , msr ‘ - 193592! .‘ '3‘ [ H1313}. .1 ;. , . 2 _ "My; '11. .‘ ‘ t '1‘.’ 7m» 2291:! sham 2'. 2.» “new fan. r! -- 2 mt .“fl'! «hang $M¢3§ffib yL-Aawo. z. ;. r5 4.2V!!! 0! tang} 95 accumulation of biomass, males accumulating more mass in foliage tissues only. 10. The photosynthetic strategies of males and females differ. The many significant differences between the sexes of Acer negundo strongly suggest that the sexes have specialized to preform their respective reproductive roles. The results of this study resolve several details of some secondary characters of A, negundo but many points suggested by the data require futher investigation before conclusions can be drawn. Additionally, the results of this study raise new questions about the secondary sex characters of A. negundo not previously considered. Problems which one may more easily address include a reinvestigation of the chromosomes to establish the existance of an unequal pair of sex chromosomes and a thorough investigation into growth responses by the sexes in a closed canopy situation. A chromosome investigation would be straight forward though perhaps tedious for personal observation of mitotic divisions indicates that the chromosomes are quite small. The growth response to a closed canopy may be addressed through a survey of various aged stands of A. ne undo, in effect following growth rates through time. Another area of potential research suggested by this report are the alleged differences in the photosynthetic L 7' l . 3"“ ‘- ‘ l . .». ._ 1‘} ’41-")8 ".1! . ,7, 72.1.. _ ‘I‘JOL‘ x.)L*nr_:;.' «In. “hwm‘i ' '2. 11.- r ‘ 'm‘ctg‘m} 101 .'. 2-0." :qm‘. as; war; '9 ;,z. . .JD ” - ' , e4") 35.633 33.139123? 39243;; u.- :.‘u$‘ta': 5m can mam-mm trim; «'2 Jim: Jump me a 1 96 capabilities of the sexes. Investigations in this area may require experiments involving the carbon assimilation rate per specified leaf area and leaf mass and at various light levels. One may also examine this with and without the presence of a resource sink (developing fruits) and at various stages of fruit development. Also of importance in the question of photosynthetic contribution of the fruit to its own development. This study only dealt with above ground biomass. An investigation of the below ground biomass would be of interest to determine if the above ground differences are reflected in the root system. An extremely interesting area of investigation would be a detailed study of resource allocation and growth in the few hermaphroditic individuals observed by Wagner (1975). A comparison of this information with the results of this study could provide very enlightening information on advantages and/or disadvantages of dioecy in A. negundo. Finally, it has be suggested that the genus Age; is evolving toward dioecy (Hesse, 1979). How the sex differences of Acer negundo relate to the present patterns of growth and resource allocation in the other species of this genus may provide a foundation of data on which to build a proposal for the evolution of dioecy, information which is lacking in many of the current theories. nannies. :t‘ .2 " ' 4‘ 1: 132; aura; 21-3 1.2;) 13193;...9122: to 222:: 'r 2.» m o5??? wail .Eht“ mass?) - w .701 ear-x535” svva:--.~~.c $1.1 «1.1 $136.! We ram 2.. Mums new amino 9“ $3 ueismlia 9542mm. M5 at an?» no “é 56315562122! : Wu“ m0 can»? ' was“: mfg :62erm 94.) no! A»: m a; 3“ 1m 3e 15"?“ at mu»: .1 A.“ § . L.,:yrl APPENDIX Regressions for the calcualtion of tree biomass 97 TABLE A1. Wood and bark oven dry densities (grams per cubic centimeter). All differences are nonsignificant. MALE FEMALE t WOOD x .5194 .5138 .300 se .0115 .0135 n 23 12 A .663 .678 r2 .469 .476 n 35 22 BARK DENSITY = A + B(DIAMETER) -_...-.---.-<—» ,'—-—»- 1mm -:j —-l H II: INC] -:: —-—( r—J. if; QT! .J- ‘ '3'! E1 H ['0 Ill] 1; U L 1 F I. 3.4.! H 98 an- BREE DENSITV — FEMALE 34 4— .. I: :2: —2-- Cl D ‘2? I IS: D “Ha—h". g D 1.... L I L” TI 1 J l u u an a n n n n I 1 a a 1 I .......... +1+1+1+1++ 4:4 :3 4 E E 14:11:: 14 12:12- as D I f—‘IHETEF-Z FIGURE A1. Relationship between female bark density and stem diameter. E} H F2 K E! E H 352 I T "n" -' H H L E ~12" u "" fl 9-- 0:1 I_v ---- U ”'1' I“ .3... ”a n 1%...“ a D U =- D I -4-- 31 a " D D hi -d~ . a D N n u . _ .2»... u a an HER-ck.“ a D .. DR%.L~ — “-2... L. F" H"!!! 1 .. D .24 M E T E: E: FIGURE A2 Relationship between male bark density and stem diameter. IIDIIDI Iii} Ill". TABLE A2. Regression parameters for new branch mass. All dependent data were square root transformed. DIAMETER SIZE CLASS MALE 0 - 2.0 B 4.712 r2 .961 n 85 FEMALE t -1.101 4.806 .40 .953 80 Table A3. Regression parameters for new branch leaf mass. All dependent data were square root transformed. DIAMETER SIZE CLASS MALE A -0114 0 - 2.0 B 4.355 r2 .936 n 85 FEMALE t -0291 4.776 .927 80 1.78 {barn-E wan no? \t..17.‘£14 2‘. l¢39‘1?93 .EA _ .4 m sun” 97“. age» tend».- "2‘9." [ll -38“ , 4.3.“ .bmo! 2. " " A d j: - . 3. , .as J u... .|'_~. w‘M-q'?“n”—-—ufiv _.. 4 <-- ---...—-...o—.---'~n“ 5g 4 ' ." I i‘. o ‘, ‘6 3 . ._ 7 . . ~ :2; . ”—p—bqa¢¢uggd§. ‘ . ’I. -.| .. _ ~ ._ 124‘s" : , ~ 1 4‘ . ' . , 2‘ . ._ __ ____-_-___.._____ _.._.-_ . m—__—__.—_._ 100 TABLE A4. Regression parameters for calculation of new branch mass on existing branches. All dependent data were square root transformed except were indicated by *, these were log transformed. DIAMETER SIZE CLASS MALE FEMALE A -.403 -.527 B B 1.833 1.960 r3 .724 .675 n 79 83 A -.450 -.623 0 - 1.8 M B 2.171 2.332 r’ .662 .755 n 56 49 A -.887 -1.255 T B 3.340 3.995 r’ .917 .885 n 44 42 A 1.033 1.327 B B 1.152 1.368 r’ .460 .392 n 18 16 A 1.915 1.9 - 2.9 M B 1.356 r’ .471 n 12 A .246* -3.675 T B .564 5.157 r’ .672 .892 n 23 7 A -.221 -6.010 3.0 - 3.9 B 2.705 4.750 r’ .266 .553 n 34 34 A -16.163 .769* 4.0 - 4.9 B 6.593 .299 r’ .669 .265 n 14 16 A -6.840 -2.689 5.0 - 5.9 B 4.299 3.704 r2 .536 .242 n 13 12 A 2.099* -4.355 6.0 - 10.9 B .084 3.762 r’ .594 .706 n 9 12 Mason»! 1‘. 22.3. d .0, 9mm nab wj Misc ”-0- mac-5‘ 0. will ‘ FA 418m 101 TABLE A5. Regression parameters for total branch mass. All dependent data were square root transformed except were indicated by *, these log transformed. SIZE CLASS MALE FEMALE A -1.939 -1.963 B B 7.226 7.112 r2 .930 .949 n 79 83 A -1.396 -1.876 0 - 1.8 M B 5.964 6.884 r' .928 .956 n 56 49 A -1.610 -1.811 T B 6.311 6.270 r’ .975 .940 n 44 42 A -3.208 1.157* 1.9 - 2.9 B 8.901 .571 r2 .882 .929 n 41 35 A -9.886 -10.635 3.0 - 3.9 B 11.508 12.189 r’ .892 .957 n 34 34 A -34.216 2.129* 4.0 - 4.9 B 17.434 .254 r’ .951 .872 n 14 16 A -16.545 -16.904 5.0 - 5.9 B 13.372 13.671 r’ .921 .871 n 13 12 A 2.831* -20.877 6.0 - 10.9 B .135 14.321 r2 .874 .962 n 9 12 .' P7” 5“.“ 322'. 102 TABLE A6. Regression parameters for leaf mass. All dependent data were square root transformed except where indicated by *, these log transformed. DIAMETER SIZE CLASS 0 — 1.8 1.9 - 2.9 3.0 - 3.9 4.0 "' 4.9 500 - 509 6.0 - 10.9 UHUV 5Hw> SHWV :wa SHWF ”Hwy :2 o u u u a sum» 5H0!» MALE -.674 4.510 .831 79 -0433 4.570 .834 56 -0464 4.917 .929 44 2.106 3.270 .631 18 -0370 5.589 .880 23 -1.454 5.671 .576 34 -23.086 10.891 .800 14 -8.557 7.492 .702 13 2.546* .104 .744 FEMALE -.791 4.644 .809 83 -0562 4.400 .812 49 -1.122 5.695 .896 42 1.185* .391 .781 35 -3.934 6.514 .825 34 1.779* .209 .429 16 6.228 .518 -4.762 6.300 .831 12 i! g. -—v r 5 *“2%9#2:4“° L J ' * r , , 1 1.0:}; 1 A 103 LITERATURE CITED Abrahamson, W.G. and H. Caswell. 1982. On the comparative allocation of biomass, energy, and nutrients in plants. Ecology 63: 982-991. Bawa, K.S. and P.A. Opler. 1975. Dioecism in tropical forest trees. Evolution 29: 167-179. Bazzaz, F.A. and R.W. Carlson. 1979. Photosynthetic contribution of flowers and seeds to reproductive effort of an annual colonizer. New Phytol. 82: 223-232. Bidwell, R.G.S. 1974. Plant Physiology. 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