2018 ESA Annual Meeting (August 5 -- 10)

COS 93-9 - Interacting effects of climate change and soil characteristics on carbon and nitrogen loss from northern hardwood forests

Thursday, August 9, 2018: 10:50 AM
357, New Orleans Ernest N. Morial Convention Center
Stephanie M. Juice1, E. Carol Adair1, Paul G. Schaberg2, Gary J. Hawley1, Alexandra M. Kosiba1, Carl Waite1, Deane Wang1 and Julia N. Perdrial3, (1)Rubenstein School of Environment and Natural Resources, University of Vermont, Burlington, VT, (2)USDA Forest Service, Burlington, VT, (3)Geology, University of Vermont, Burlington, VT
Background/Question/Methods

Warmer conditions and snowpack reduction associated with climate change in the northeast USA could increase carbon (C) and nutrient losses from northern forest soils. Effects may vary on soils with different physical and chemical characteristics that determine soil nutrient status and water holding capacity. Additionally, climate change may increase phenological disconnects between plant and microbial communities, lengthening periods of microbial activity during plant dormancy when nutrients are vulnerable to leaching. We conducted a replicated climate change mesocosm experiment to address the following questions: (1) Does the effect of warming and snowpack reduction on water, C, and nutrient losses vary by soil type? (2) Do changes in microbial and plant phenology increase water, C, and nutrient losses? Mesocosms contained two soils (coarse/high calcium or fine/low calcium) and received three climate treatments (control, 2 °C warming, or snow exclusion). Mesocosms were planted with four deciduous tree species to mimic the northern forest. For two years, we monitored plant and soil phenology to identify periods when microbes were active and plants were not. Throughout the experiment we measured soil respiration, in situ nitrogen mineralization and nitrification, and soil water volume and chemistry for loss of nitrogen, C, and base cations.

Results/Conclusions

While soil type had no effect on soil water dynamics, we found that climate treatments reduced the mean soil water volume draining from the mesocosms (P = 0.0043). Plant biomass also significantly altered soil water volume (P = 0.0395). A linear model including soil type, treatment, and plant biomass described 64% of the variability observed in soil water volume. Additionally, warming significantly elevated dissolved organic carbon (DOC) losses compared to control and snow exclusion (P = 0.0650). DOC losses were also significantly greater from the coarse textured soil (P = 0.0002), as was total nitrogen (TN) loss (P<0.0001). TN loss was additionally greater from both climate treatments relative to control (P = 0.0093). However, the effect of climate treatment varied across soils (P = 0.0107), with snow exclusion experiencing the greatest loss from fine textured soils but not from coarse soils. Collectively, these results indicate that climate change can be expected to increase soil losses of water, C, and N, but local soil conditions will play an important role in determining the ultimate effects.