Seasonal variation of carbon fluxes in a sparse savanna in semi arid Sudan

被引：58
作者：
Ardö J. [1 ]
Mölder M. [1 ]
El-Tahir B.A. [2 ]
Elkhidir H.A.M. [2 ]
机构：
[1] Physical Geography and Ecosystems Analysis, Lund University, S-223 62 Lund
[2] Agricultural Research Cooperation, El Obeid Research Station, 51111 El Obeid
来源：
Carbon Balance and Management | / 3卷 / 1期
关键词：
Photosynthetic Photon Flux Density; Ecosystem Respiration; Mean Annual Precipitation; Soil Heat Flux; Volumetric Soil Moisture;
D O I：
10.1186/1750-0680-3-7
中图分类号：
学科分类号：
摘要：
Background: Large spatial, seasonal and annual variability of major drivers of the carbon cycle (precipitation, temperature, fire regime and nutrient availability) are common in the Sahel region. This causes large variability in net ecosystem exchange and in vegetation productivity, the subsistence basis for a major part of the rural population in Sahel. This study compares the 2005 dry and wet season fluxes of CO2 for a grass land/sparse savanna site in semi arid Sudan and relates these fluxes to water availability and incoming photosynthetic photon flux density (PPFD). Data from this site could complement the current sparse observation network in Africa, a continent where climatic change could significantly impact the future and which constitute a weak link in our understanding of the global carbon cycle. Results: The dry season (represented by Julian day 35-46, February 2005) was characterized by low soil moisture availability, low evapotranspiration and a high vapor pressure deficit. The mean daily NEE (net ecosystem exchange, Eq. 1) was -14.7 mmol d-1 for the 12 day period (negative numbers denote sinks, i.e. flux from the atmosphere to the biosphere). The water use efficiency (WUE) was 1.6 mmol CO2 mol H2O-1 and the light use efficiency (LUE) was 0.95 mmol CO2 mol PPFD-1. Photosynthesis is a weak, but linear function of PPFD. The wet season (represented by Julian day 266-273, September 2005) was, compared to the dry season, characterized by slightly higher soil moisture availability, higher evapotranspiration and a slightly lower vapor pressure deficit. The mean daily NEE was -152 mmol d-1 for the 8 day period. The WUE was lower, 0.97 mmol CO2 mol H2 O-1 and the LUE was higher, 7.2 μmol CO2 mmol PPFD-1 during the wet season compared to the dry season. During the wet season photosynthesis increases with PPFD to about 1600 μmol m-2s-1 and then levels off. Conclusion: Based on data collected during two short periods, the studied ecosystem was a sink of carbon both during the dry and wet season 2005. The small sink during the dry season is surprising and similar dry season sinks have not to our knowledge been reported from other similar savanna ecosystems and could have potential management implications for agroforestry. A strong response of NEE versus small changes in plant available soil water content was found. Collection and analysis of flux data for several consecutive years including variations in precipitation, available soil moisture and labile soil carbon are needed for understanding the year to year variation of the carbon budget of this grass land/sparse savanna site in semi arid Sudan. © 2008 Ardö et al; licensee BioMed Central Ltd.
引用
收藏
相关论文
共 73 条
[1]  
Veenendaal M.E., Kolle O., Lloyd J., Seasonal variation in energy fluxes and carbon dioxide exchange for a broad leaved semi-arid savanna (Mopane woodland) in Southern Africa, Global Change Biology, 10, 3, pp. 318-328, (2004)
[2]  
Prentice I., Farquhar G., Fasham M., Goulden M., Heimann M., Jaramillo V., Kheshgi H., Le Quere C., Scholes R., Wallace D., The carbon cycle and atmospheric carbon dioxide, Climate Change 2001, (2001)
[3]  
Scurlock J., Hall D., The global carbon sink: A grassland perspective, Global Change Biology, 4, pp. 229-233, (1998)
[4]  
Lal R., Potential of Desertification Control to Sequester Carbon and Mitigate the Greenhouse Effect, Climatic Change, 51, pp. 35-72, (2001)
[5]  
Olsson L., Ardo J., Soil carbon sequestration in degraded semi arid agro-ecosystems - Perils and potentials, Ambio, 31, pp. 471-477, (2002)
[6]  
Grace J., San Jose J., Meir P., Miranda H.S., Montes R., Productivity and carbon fluxes of tropical savannas, Journal of Biogeography, 33, 3, pp. 387-401, (2006)
[7]  
Taylor J., Lloyd J., Sources and sinks of atmospheric CO<sub>2</sub>, Australian Journal of Botany, 40, pp. 407-418, (1992)
[8]  
Ardo J., Olsson L., Soil carbon sequestration in traditional farming in Sudanese dry lands, Environmental Management, 31, SUPPL. 1, (2003)
[9]  
Grunzweig J.M., Lin T., Rotenberg E., Schwartz A., Yakir D., Carbon sequestration in arid-land forest, Global Change Biology, 9, 5, pp. 791-799, (2003)
[10]  
Lal R., Hassan H., Dumanski J., Desertification Control to Sequester C and Mitigate the Greenhouse Effect, Carbon Sequestrations in Soils: Science, Monitoring and Beyond, pp. 83-139, (1999)
12345678