Anthropogenic climate change is altering precipitation regimes globally, creating more extreme soil moisture dynamics, which translates into increased water stress and altered ecosystem structure and function. To explore the potential consequences of this water stress on plants, we established two field experiments at the Purdue Wildlife Area in West Lafayette, IN.
Throughfall was manipulated in a deciduous forest to simulate seasonal redistribution of precipitation. Using a fully factorial, nested design, winter and summer throughfall were altered to create wet, dry, and control (ambient) treatments. Summer treatments consisted of rainout shelters (-50%) and manual water addition (+50%), and winter treatments consisted of snow removal (-100%) and snow addition (+100%). The objectives of this study were to explore changes in (1) N cycling using intact soil core incubations and N extractions, (2) woody plant recruitment by planting and tracking germination and survival of tree seeds, and (3) understory community dynamics using percent cover measurements.
To examine the effects of extreme drought on a tallgrass prairie, precipitation was reduced by 40% using partial rainout shelters to simulate a 1-in-100-year drought. The objectives of this study were to examine the effects of summer drought on plant community composition, using percent cover and biomass measurements.
Results/Conclusions
Snow removal in dry winter plots resulted in lower soil temperatures compared to control treatments, which typically stayed at or near 0°C. This could have implications for woody plant recruitment of species, such as Lindera benzoin, a common understory shrub, which had lower germination rates and higher mortality rates under dry winter treatments. After one year of manipulation, there were no differences found in understory community composition or net nitrogen mineralization rates across treatments.
In the grassland experiment, precipitation manipulations did not consistently affect soil moisture. After only one year of manipulation, there were no differences found in plant community composition or in annual net primary production.