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Effects of Nitrogen Additions on Soil Carbon Pools in Two Humid Tropical Forest Types


EMSL Project ID
25398

Abstract

Human activity has greatly increased available nitrogen (N) on Earth, with N deposition rates in tropical regions predicted to be the highest globally in coming decades. Because plant growth is not commonly limited by N in tropical forests, effects of N deposition on carbon (C) cycling are likely to be largest in soils. We observed an increase in bulk soil C after 3.5 years of N fertilization in two tropical forest types. The proposed study will focus on the mechanisms responsible for this increase in soil C. We are proposing to use 13C-NMR spectroscopy to analyze the relative abundance of organic functional groups in soil organic matter (SOM) to better understand the mechanisms of C cycling and sequestration in soils. The work would be done by one graduate student whose dissertation project will greatly benefit from 13C-NMR analyses, as it provides valuable information on the source, quality and stability of organic matter in soils. The project will examine two organic soil C pools (labile and occluded). Soil are currently being separated in pools using a density fractionation scheme in the laboratory of Dr. Margaret Torn at Lawrence Berkeley National Laboratory in Berkeley, CA. Examination of the different pools using 13C-NMR spectroscopy will help us identify the mechanisms responsible for the observed increase, and the potential for long-term changes in soil C storage. This project addresses DOE BER research areas because nitrogen deposition is an environmental impact of fossil fuel energy use and because nitrogen-carbon interactions are important for terrestrial carbon sequestration.

Project Details

Project type
Large-Scale EMSL Research
Start Date
2007-09-01
End Date
2010-09-30
Status
Closed

Team

Principal Investigator

Daniela Cusack
Institution
Colorado State University

Team Members

Margaret Torn
Institution
Lawrence Berkeley National Laboratory