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Harvard Forest Symposium Abstract 2012
- Title: Ectomycorrhizal abundance effects on Eastern Hemlock element cycling
- Primary Author: Colin Averill (University of Texas - Austin)
- Abstract:
Soil nitrogen limitation of primary productivity is a globally observed phenomenon. Increases in productivity requires increases in plant nitrogen (N) uptake to support photosynthesis. Much focus has been placed on the rate of nitrogen cycling with the assumption that increases in nitrogen cycling rates are required to support increases in plant nitrogen uptake.
What has gone largely ignored is the large pool of labile N stored in microbial biomass. Microbial biomass N is 3-4 times annual plant N uptake in temperate coniferous forests. Symbiotic ectomycorrhizal fungi in these forests have CN much greater CN ratios than bulk microbial biomass. An increase in the relative abundance of ectomycorrhizal fungi in the microbial biomass could effectively change the partitioning of N between plant and microbial N cycles. N stored in the microbial biomass N cycle could pass to the plant/symbiont N cycle. This would allow increased rates on plant N uptake without commensurate changes in N cycling rates, as ecosystem N cycling encompasses both plant/symbiont and heterotrophic microbial N cycles.
I will test this idea using a chronosequence of Hemlock stands in and around the Harvard Forest. I hypothesize that increasing forest age will result in an increase in the relative abundance of ectomycorrhizal fungi in the microbial biomass. I will then compare the ratio of annual plant N uptake to microbial biomass N pools to determine if a change in partitioning of N between plant and microbial cycles occurs.
- Research Category: Large Experiments and Permanent Plot Studies
Soil Carbon and Nitrogen Dynamics
