Fate and effect of N deposition in tropical forest – University of Copenhagen

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Fate and effect of N deposition in tropical forest

Bro i en tropisk skov i Kina

The emission of nitrogen (N) to the atmosphere is increasing globally and thus the N deposition to forest is several times higher than the natural level. Some of the world’s highest N inputs to forest are found in regions with tropical or subtropical climate in South-eastern China. Soils in the tropics are often very old and usually forest growth is limited by the nutrient phosphorus (P). Researchers therefore expect tropical forests to have enough N, and inputs from pollution will provide excess N likely to be lost by leaching to ground and surface waters. However the possible consequences of elevated N input to such warm humid forests have only been addressed in few studies world-wide.

To study the effects of elevated N deposition the first field scale nitrogen input manipulation study under warm and humid climate was established in 2003 at the Dinghushan Biosphere Reserve, China by the South China Botanical Garden in cooperation with Per Gundersen from the Biogeochemisty Reseach Group. The experiment is run by a Chinese research group headed by Prof. Jiang-Ming Mo. It includes studies of the impact of nitrogen on tree growth and physiology, plant diversity, soil fauna, soil microbiology, N cycling, interaction with phosphorus, nitrate leaching, soil acidification, carbon sequestration and greenhouse gas exchange with results published in several international journals.

Currently PhD-student Geshere A. Gurmesa is involved in the Chinese experiment. The aim of his PhD project is to investigate the fate of deposited N (simulated increased N-deposition and ambient) in tropical forest ecosystems and especially to understand the N retention mechanisms in these forests using isotopic labeling techniques (15N), and to compare the fate of changed N input in the humid tropics with that found in similar experiment in temperate forests.

Financial support for the PhD on the fate of N was received from the Sino-Danish Center for Education and Research (SDC).

Project period: 2003-2015