Projections of Forest and Nutrient Dynamics with Future Climate Change in Watershed 2 of the H.J. Andrews Experimental Forest. Zheng Dong, Syracuse University.
Tuesday, October 10, 10-11 AM, Richardson Hall 107.
Abstract: Statistically downscaled climate change scenarios from four General Circulation Models for two Representative Concentration Pathways (RCP4.5 and RCP8.5) were applied as inputs to the ecosystem model, PnET-BGC, to examine future dynamics of water, carbon, and nitrogen in an old-growth Douglas-fir forest.
Projections show large increases in stomatal conductance throughout the year from 1986-2010 to 2076-2100 and increases in leaf carbon assimilation between October and June over the same period. The CO2 effects on vegetation are projected to 1) amplify decreases in transpiration and increases in soil moisture; and 2) alleviate decreases in photosynthesis, plant biomass, and soil organic matter; while 3) having negligible effects on the dynamics of nitrogen. Future dynamics of water and carbon under the RCP scenarios are largely affected by a 37% to 72% reduction in leaf area index (LAI) resulting from severe air temperature and humidity stress to the forest in summer. Important implications of future decreases in LAI include 1) decreases in transpiration and increases in summer and fall soil moisture; 2) decreases in photosynthesis, plant biomass, and soil organic matter; and 3) accumulation of nitrogen in plant tissue and altered foliar and soil stoichiometry of carbon to nitrogen.
These model projections suggest that future decrease in transpiration and moderate water holding capacity may mitigate soil moisture stress to the old-growth Douglas-fir forest. Future increases in nitrogen concentration in soil organic matter result in a large increase in net nitrogen mineralization. Our findings highlight the important roles of foliar production and LAI on future dynamics of water, carbon, and nitrogen in Douglas-fir forests under climate change. Models suggest that projected air temperature and humidity stress without considering acclimation of optimal temperature for photosynthesis can be more detrimental to foliar production than soil moisture stress related to the lack of downward feedback in severity through reduced transpiration.
Zheng will be available in the afternoon of Oct 10 and morning of Oct 11 for one on one or small group followup discussions - Contact Sherri Johnson to schedule