Soil moisture is a key integrative variable in natural and managed ecosystems, dependent on a location's climate, vegetative cover, soil type, topography, and other factors. A study of spatial and temporal variations in soil moisture in the Great Lakes region of the USA was undertaken to better understand the impacts of varying land cover and soil types as well as variations in climate. Soil moisture was simulated with the Soil Water and Assessment Tool (SWAT) model for 5 different land cover types and 6 representative soil types at 29 climate observation sites across the region during a study period of 1900-2008.Significant increases in growing season soil moisture levels were found across much of the region during the study period associated with concurrent increases in precipitation, the largest positive trends in south eastern Michigan and the largest negative trends in eastern Iowa. Some distinct changes in seasonality were also noted. The average date during the spring season on which soil moisture fell below field capacity is gradually occurring up to 18 days earlier in the year over the study period. Similarly, the dates at which the minimum soil moisture occurred each warm season and the date of recharge of soil moisture to field capacity late in the calendar year occurred up to 19 days earlier.Collectively, the results suggest that soil moisture and plant available water across the region have increased with time with a corresponding decrease in the risk of water-related stress, which has important implications for plant-based agriculture and the management of natural resources.
Read
