N2O emissions from N saturated subtropical forest in South China (completed)

About the project

Surplus of reactive nitrogen (Nr) is one of China's most pressing environmental problems, and may cause a positive feedback to climate change through increased N₂O emission. We previously found that forests in sub-tropical China receiving high atmogenic N loads (> 4g N m^-2 yr^-1) differ in their apparent ability to retain Nr, suggesting that denitrification may be a major sink for excess N and that forests may become N-saturated. Rapid N-cycling and the monsoonal climate with wet, warm summers imply potentially high N₂O emissions from multiple sources but no systematic assessment of N₂O emissions on a watershed level has been conducted yet.

This is a multidisciplinary study in an N-saturated research site (TieShanPing, Chongqing, PR China) aiming at identification of hotspots for nitrification, denitrification and N₂O emissions in relation to the availability of Nr and hydrological conditions. The overall goal is to estimate N₂O emission rates in humid sub tropical south China and to understand the environmental controls at a watershed level. Ultimately, these data are needed to facilitate upscaling approaches for N₂O emissions and to predict the effect of changing hydrological conditions on N₂O emissions at a regional scale. Our approach draws on a strong alliance of Sino-Norwegian expertise in terrestrial biogeochemistry proven in previous projects. The proposed project provides an important arena for Sino-Norwegian exchange of expertise with respect to quantification and process understanding of greenhouse gas emissions from forest and mountain ecosystems.

Objectives

To determine quantitative relationships between climate-related factors and N₂O emission fluxes from representative N saturated sub-tropical forests in south China

Sub-goals:

1. To quantify fluxes of nitrogen deposition, N₂O emission and nitrogen runoff in the representative sub-tropical forest catchment TieShanPing (TSP) near Chongqing, southwest China
2. To parameterize the LISEM, COUP and Brook90 models to describe and simulate the water and energy balances in the TSP catchment
3. To determine quantitative relationships between climate, nitrification, denitrification and N₂O emissions for the dominant soil-vegetation types in the catchment
4. To scale up annual N₂O emission strength to the catchment and regional level

Financing

- An RCN funded project under the NORKLIMA program with Plant & Env. Sciences at University of Life Science (UMB-IPM)

Links: RCN NORKLIMA program NMBU:IPM

Cooperation

This is a collaborative interdisciplinary research project between UMB, BioForsk, NVE, UiO, NIVA, RCEES, CAF, Tsinghua Univ. and Chongqing Inst. Environ. Protection Monitoring

Master thesis

Cathrine Brecke Gundersen, June 2012. Biodegradation and Characterization of Dissolved Organic Matter (DOM) along the Flowpath of a N-saturated Subtropical Forested Catchment in China.