来自西非苏丹稀树草原不同生态系统的二氧化碳通量。

Carbon dioxide fluxes from contrasting ecosystems in the Sudanian Savanna in West Africa.

作者信息

Quansah Emmanuel, Mauder Matthias, Balogun Ahmed A, Amekudzi Leonard K, Hingerl Luitpold, Bliefernicht Jan, Kunstmann Harald

机构信息

Federal University of Technology, Akure, Nigeria ; Kwame Nkrumah University of Science and Technology, Kumasi, Ghana.

Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology, Garmisch-Partenkirchen, Germany.

出版信息

Carbon Balance Manag. 2015 Jan 13;10(1):1. doi: 10.1186/s13021-014-0011-4. eCollection 2015 Dec.

DOI:10.1186/s13021-014-0011-4

PMID:25632297

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC4302244/

Abstract

BACKGROUND

The terrestrial land surface in West Africa is made up of several types of savanna ecosystems differing in land use changes which modulate gas exchanges between their vegetation and the overlying atmosphere. This study compares diurnal and seasonal estimates of CO fluxes from three contrasting ecosystems, a grassland, a mixture of fallow and cropland, and nature reserve in the Sudanian Savanna and relate them to water availability and land use characteristics.

RESULTS

Over the study period, and for the three study sites, low soil moisture availability, high vapour pressure deficit and low ecosystem respiration were prevalent during the dry season (November to March), but the contrary occurred during the rainy season (May to October). Carbon uptake predominantly took place in the rainy season, while net carbon efflux occurred in the dry season as well as the dry to wet and wet to dry transition periods (AM and ND) respectively. Carbon uptake decreased in the order of the nature reserve, a mixture of fallow and cropland, and grassland. Only the nature reserve ecosystem at the Nazinga Park served as a net sink of CO, mostly by virtue of a several times larger carbon uptake and ecosystem water use efficiency during the rainy season than at the other sites. These differences were influenced by albedo, LAI, EWUE, PPFD and climatology during the period of study.

CONCLUSION

These results suggest that land use characteristics affect plant physiological processes that lead to flux exchanges over the Sudanian Savanna ecosystems. It affects the diurnal, seasonal and annual changes in NEE and its composite signals, GPP and RE. GPP and NEE were generally related as NEE scaled with photosynthesis with higher CO assimilation leading to higher GPP. However, CO effluxes over the study period suggest that besides biomass regrowth, other processes, most likely from the soil might have also contributed to the enhancement of ecosystem respiration.

摘要

背景

西非的陆地表面由几种类型的稀树草原生态系统组成，这些生态系统在土地利用变化方面存在差异，而土地利用变化会调节植被与上层大气之间的气体交换。本研究比较了苏丹稀树草原中三种不同生态系统（草地、休耕地与农田混合地以及自然保护区）的二氧化碳通量的日变化和季节估计值，并将它们与水分可利用性和土地利用特征联系起来。

结果

在研究期间，对于三个研究地点，旱季（11月至3月）普遍存在土壤水分可利用性低、蒸气压亏缺高和生态系统呼吸低的情况，但雨季（5月至10月）则相反。碳吸收主要发生在雨季，而净碳排放分别发生在旱季以及旱季到雨季和雨季到旱季的过渡时期（上午和下午）。碳吸收量按自然保护区、休耕地与农田混合地、草地的顺序递减。只有纳津加公园的自然保护区生态系统是二氧化碳的净汇，这主要是因为在雨季其碳吸收量和生态系统水分利用效率比其他地点大几倍。这些差异在研究期间受反照率、叶面积指数、生态系统水分利用效率、光合有效辐射和气候学的影响。

结论

这些结果表明，土地利用特征会影响导致苏丹稀树草原生态系统通量交换的植物生理过程。它影响净生态系统交换及其复合信号、总初级生产力和呼吸作用的日变化、季节变化和年变化。总初级生产力和净生态系统交换通常相关，因为净生态系统交换与光合作用成比例，较高的二氧化碳同化导致较高的总初级生产力。然而，研究期间的二氧化碳排放表明，除了生物量再生长外，其他过程（很可能来自土壤）也可能导致了生态系统呼吸的增强。