Understanding the impact of climate on forest productivity requires knowledge of soil nutrient fluxes derived from interactions among climate, soils, the biotic community, and disturbance or management.  Soil nutrient fluxes can be characterized by placing an ion adsorbing sink in situ during critical periods.  This poster reports the use of Plant Root Simulator (PRS)™-probes to quantify soil nutrient dynamics in boreal, temperate, and tropical forest ecosystems.  Boreal forest: PRS™-probes were used in north-western Quebec to determine the effects of open-top chamber (OTC) climate change simulations on soil nutrient fluxes in mixedwood-boreal, post-disturbance forests. Temperate forest: In a temperate region of Tennessee PRS™-probes were used to assess the impact of free-air CO₂ enrichment (FACE) on nutrient cycling of a sweetgum (Liquidambar styraciflua L.) monoculture plantation. Tropical forest: In regenerating Acacia koa (N-fixing) tropical forests of Hawaii, PRS™-probes were used to measure the impact of precipitation and elevation/temperature gradients on soil N and P bioavailability as related to forest structure and productivity. 
Results/Conclusions

Boreal forest: Compared to the control treatment, OTCs significantly reduced soil temperature (~2º) and volumetric soil water content (~10%), which significantly reduced Ca (p=0.001) and Mg (p=0.007) supply rates.  PRS™-N supply rates at post-logging sites were significantly higher (p≤0.006) in control plots than in all other combinations of OTC treatments. Temperate forest: PRS™-N and P nutrient supply rates were not significantly affected by FACE, despite the fact that both plant N uptake and N requirement were significantly greater (p<0.10) with elevated CO₂. Tropical forest: PRS™-N supply rates were similar along a moisture gradient but N bioavailability declined significantly with elevation (R²=0.86, p<0.05) from 33.4 to 15.7 μg cm⁻².  Soil P availability generally declined with elevation, but the correlation was less significant (p=0.07). These studies demonstrate that small spatial scale, topography, soil depth, mineralogy, and physical and chemical properties influence soil nutrient bioavailability, as well as the cycling of organic matter. Measuring the effect of climate change on soil nutrient flux in forest ecosystems is an important component of plant community research and crucial for sustainable management of forest productivity.