PARENT SESSION
Poster Session # 13: Biogeochemistry, Photosynthesis, and Respiration.
Tuesday, August 5 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.
Coupled cycles of carbon and phosphorus in tropical scosystems: A modeling study.
Zhang, Chi*,1, Tian, Hanqin1, Pan, Shufen1, Melillo, Jerry2, Kicklighter, David2, 1 The University of Kansas, Lawrence, KS 660452 Marine Biological Laboratory, Woods Hole, MA 02543
ABSTRACT- Phosphorus (P) is an important nutrient element for ecosystem production that affects carbon (C) exchange between terrestrial ecosystems and the atmosphere. Evidences from field experiments and observations have indicated that P is the limitation factor for terrestrial ecosystems in their late succession period, especially for tropical rain forests growing on intensively weathered soil. This has been suggested to be caused by the low content of soil P as well as the low availability of P fixed in soil. Our study on 2,400 soil pedons shows that the average soil P density of the top 50 cm soil is only 830 g/m3. And the spatial distribution of P is uneven, and the tropical region has a low supply of soil P. The P storage is also threatened by land conversion, which could cause a mean P loss of about 2 t/ha from the terrestrial ecosystems. To study the interaction of P supply and C sequestration processes, we have developed a submodel of the P cycle for the Terrestrial Ecosystem Model (TEM). The P cycle is coupled with C process by limiting gross primary production with the available P supply, and by the feedback of net primary production on resource allocation to the P uptake. To address the problem of tropical P limitation, the model is specially calibrated against several intensively studied tropical rainforest sites. Then we apply the model to investigate coupled cycles of P and C in tropical terrestrial ecosystems, and further to assess how the P loss induced by tropical deforestation could influence ecosystem production in tropics.
Key words: Carbon cycle, Ecosystem modeling, Phosphorus cycle, Tropical Ecosystem