PS 67-38 - Will elevated N inputs from acid rain stimulate C storage in an aggrading appalachian temperate deciduous forest?

Thursday, August 9, 2012
Exhibit Hall, Oregon Convention Center
Zachariah K. Fowler1, Mary Beth Adams2 and William T. Peterjohn1, (1)Biology, West Virginia University, Morgantown, WV, (2)Northern Research Station, USDA Forest Service, Morgantown, WV

Elevated available N inputs due to acid rain may affect C storage in forest ecosystems by changing the rates of productivity and decomposition.  Increases in productivity due to relaxation of N limitation or decreases in decomposition due to the effect of added N on microbial processes could lead to an increase in C storage and help explain the “missing C sink”.  However, decreases in productivity due to the effects of N saturation and soil acidification or increases in decomposition due to changes in microbial processes could lead to a reduction in C storage capacity of these forests.  This relationship between elevated N inputs and C storage is especially important to understand in young aggrading temperate deciduous forests in Appalachia because there is a relatively high rate of N deposition in this region and these forests have been implicated in the missing sink.   This study compares various C pools between plots in the Long Term Soil Productivity (LTSP) experiment at Fernow Experimental Forest in Parsons, WV.  The LTSP experiment is a blocked, replicated study in which treatment plots were harvested and then allowed to regenerate with one of three treatments, ambient N and S inputs, elevated N and S inputs, and elevated N and S inputs plus dolomitic lime addition. 


After 14 years of continuous treatment, it was found that total plot level C storage was greater in plots receiving elevated N inputs: ~22% increase in NS plots and ~18% increase in NS+LIME plots (F=8.51, p=0.0177).  Furthermore, this increase in C storage was driven by increases in aboveground tree biomass C (F=5.43, p=0.0450) and forest floor C content (F=24.02, p=0.0014), while there were no changes in fine root C pools (F=1.16, p=0.3747) or soil C pools (F=1.5751, p=0.2819).  The aboveground tree biomass C pool increased by ~27% in the NS and ~25% in the NS+LIME plots, and the forest floor C pool increased by ~35% in the NS plots and ~12% in the NS+LIME plots.  It is important to note that the longevity of this increase in C storage depends on continued positive growth response to elevated N.  If N saturation and soil acidification weaken or reverse this positive growth response, then the increase in C storage could disappear.