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Net ecosystem carbon dioxide exchange over grazed steppe in central Mongolia.
- Source :
- Global Change Biology; Nov2005, Vol. 11 Issue 11, p1941-1955, 15p, 1 Diagram, 2 Charts, 21 Graphs
- Publication Year :
- 2005
-
Abstract
- This paper presents results of 1 year (from March 25, 2003 to March 24, 2004, 366 days) of continuous measurements of net ecosystem CO<subscript>2</subscript> exchange (NEE) above a steppe in Mongolia using the eddy covariance technique. The steppe, typical of central Mongolia, is dominated by C<subscript>3</subscript> plants adapted to the continental climate. The following two questions are addressed: (1) how do NEE and its components: gross ecosystem production (GEP) and total ecosystem respiration ( R<subscript>eco</subscript>) vary seasonally? (2) how do NEE, GEP, and R<subscript>eco</subscript> respond to biotic and abiotic factors? The hourly minimal NEE and the hourly maximal R<subscript>eco</subscript> were −3.6 and 1.2 μmol m<superscript>−2</superscript> s<superscript>−1</superscript>, respectively (negative values denoting net carbon uptake by the canopy from the atmosphere). Peak daily sums of NEE, GEP, and R<subscript>eco</subscript> were −2.3, 3.5, and 1.5 g C m<superscript>−2</superscript> day<superscript>−1</superscript>, respectively. The annual sums of GEP, R<subscript>eco</subscript>, and NEE were 179, 138, and −41 g C m<superscript>−2</superscript>, respectively. The carbon removal by sheep was estimated to range between 10 and 82 g C m<superscript>−2</superscript> yr<superscript>−1</superscript> using four different approaches. Including these estimates in the overall carbon budget yielded net ecosystem productivity of −23 to +20 g C m<superscript>−2</superscript> yr<superscript>−1</superscript>. Thus, within the remaining experimental uncertainty the carbon budget at this steppe site can be considered to be balanced. For the growing period (from April 23 to October 21, 2003), 26% and 53% of the variation in daily NEE and GEP, respectively, could be explained by the changes in leaf area index. Seasonality of GEP, R<subscript>eco</subscript>, and NEE was closely associated with precipitation, especially in the peak growing season when GEP and R<subscript>eco</subscript> were largest. Water stress was observed in late July to early August, which switched the steppe from a carbon sink to a carbon source. For the entire growing period, the light response curves of daytime NEE showed a rather low apparent quantum yield ( α=−0.0047 μmol CO<subscript>2</subscript> μmol<superscript>−1</superscript> photons of photosynthetically active radiation). However, the α values varied with air temperature ( T<subscript>a</subscript>), vapor pressure deficit, and soil water content. [ABSTRACT FROM AUTHOR]
- Subjects :
- STEPPES
CARBON dioxide
GRASSLANDS
CARBON
ECOLOGY
TEMPERATURE
CLIMATOLOGY
Subjects
Details
- Language :
- English
- ISSN :
- 13541013
- Volume :
- 11
- Issue :
- 11
- Database :
- Complementary Index
- Journal :
- Global Change Biology
- Publication Type :
- Academic Journal
- Accession number :
- 18904161
- Full Text :
- https://doi.org/10.1111/j.1365-2486.2005.01047.x