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| Titel |
Environmental influences on carbon dioxide fluxes over three grassland ecosystems in China |
| VerfasserIn |
Y. Fu, Z. Zheng, G. Yu, Z. Hu, X. Sun, P. Shi, Y. Wang, X. Zhao |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 6, no. 12 ; Nr. 6, no. 12 (2009-12-07), S.2879-2893 |
| Datensatznummer |
250004219
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| Publikation (Nr.) |
 copernicus.org/bg-6-2879-2009.pdf |
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| Zusammenfassung |
| This study compared carbon dioxide (CO2) fluxes over three grassland
ecosystems in China, including a temperate semiarid steppe in Inner Mongolia
(NMG), an alpine shrub-meadow in Qinghai (HB), and an alpine meadow-steppe
in Tibet (DX). Measurements were made in 2004 and 2005 using the eddy
covariance technique. Objectives were to document the seasonality of the net
ecosystem exchange of CO2 (NEE) and its components, gross ecosystem
photosynthesis (GEP), and ecosystem respiration (Reco), and to examine
how environmental factors affect the CO2 exchange in these grassland
ecosystems. The 2005 growing season (from May to September) was warmer than
that of 2004 across the three sites, and precipitation in 2005 was less than
that in 2004 at NMG and DX. The magnitude of CO2 fluxes (daily and
annual sums) was largest at HB, which also showed the highest temperature
sensitivity of Reco among the three sites. A stepwise multiple
regression analysis showed that the seasonal variation of GEP, Reco, and
NEE of the alpine shrub-meadow was mainly controlled by air temperature,
whereas leaf area index can likely explain the seasonal variation in GEP,
Reco, and NEE of the temperate steppe. The CO2 fluxes of the alpine
meadow-steppe were jointly affected by soil moisture and air temperature.
The alpine shrub-meadow acted as a net carbon sink over the two study years,
whereas the temperate steppe and alpine meadow-steppe acted as net carbon
sources. Both GEP and Reco were reduced by the summer and spring drought
in 2005 at NMG and DX, respectively. The accumulated leaf area index during
the growing season (LAIsum) played a key role in the interannual and
intersite variation of annual GEP and Reco across the study sites and
years, whereas soil moisture contributed most significantly to the variation
in annual NEE. Because LAIsum was significantly correlated with soil
moisture at a depth of 20 cm, we concluded that the available soil moisture
other than annual precipitation was the most important factor controlling
the variation in the CO2 budgets of different grassland ecosystems in
China. |
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