The Influence of Precipitation on Sap-flux Scaled Transpiration and Variability in Soil Moisture and Microclimate in Different Land Cover Types in Central New York State

Climate change is expected to increase flooding and drought in the northeastern United States with more frequent high intensity precipitation events and the potential for plant water stress under warmer, drier conditions. Soil moisture plays a key role in the impacts of extreme variability in precipitation on plant stress, flooding, and agricultural disruptions. Land use/ land cover influences surface microclimate and soil moisture via characteristics of vegetation, the surface, and soil. Proposed New York State climate directives may drive changes in land cover, particularly transitions between forest and agricultural fields. To better understand the link between precipitation events and soil moisture in central New York, we address two questions: i.) how is soil moisture linked to precipitation and vapor pressure deficit in different land cover classes? and ii.) in a mature, native, mixed coniferous-deciduous forest environment, how is sap flux-scaled plant transpiration linked to soil moisture and environmental conditions? We measured precipitation, VPD, canopy leaf area, surface temperature, and soil moisture and temperature in five different types of land cover: a mature mixed forest, a mature deciduous forest, a field in early stages of reforestation, mowed lawn, and an agricultural field used for winter wheat production. We measured sap flow scaled tree transpiration by establishing sap flow probes in a mature Eastern Hemlock (Tsuga canadensis) and American Basswood (Tilia americana) forest. oil moisture was lowest in the reforestation meadow, mowed site and agriculture field compared to forested sites with greater leaf area. This was driven by faster drying of the soil following rain events, despite these locations having the greatest increase in soil moisture after rain events. Daily hemlock transpiration increased after rainfall declined on drier days. Basswood transpiration stayed at a steady, lower rate. Mature hemlock tree cover can be highly sensitive to fluctuations in soil moisture and drier conditions. Accounting for greater variability in their soil moisture and temperature in types of land cover dominated by grass vegetation will be a key factor in characterizing plant transpiration, soil carbon cycling and water cycling.