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SENSITIVITY OF MESQUITE SHRUBLAND CO 2 EXCHANGE TO PRECIPITATION IN CONTRASTING LANDSCAPE SETTINGS
Author(s) -
Potts Daniel L.,
Scott Russell L.,
Cable Jessica M.,
Huxman Travis E.,
Williams David G.
Publication year - 2008
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1890/07-1177.1
Subject(s) - shrubland , environmental science , riparian zone , ecosystem , soil respiration , canopy , ecology , soil water , hydrology (agriculture) , soil science , geology , biology , geotechnical engineering , habitat
In semiarid ecosystems, physiography (landscape setting) may interact with woody‐plant and soil microbe communities to constrain seasonal exchanges of material and energy at the ecosystem scale. In an upland and riparian shrubland, we examined the seasonally dynamic linkage between ecosystem CO 2 exchange, woody‐plant water status and photosynthesis, and soil respiration responses to summer rainfall. At each site, we compared tower‐based measurements of net ecosystem CO 2 exchange (NEE) with ecophysiological measurements among velvet mesquite ( Prosopis velutina Woot.) in three size classes and soil respiration in sub‐canopy and inter‐canopy micro‐sites. Monsoonal rainfall influenced a greater shift in the magnitude of ecosystem CO 2 assimilation in the upland shrubland than in the riparian shrubland. Mesquite water status and photosynthetic gas exchange were closely linked to the onset of the North American monsoon in the upland shrubland. In contrast, the presence of shallow alluvial groundwater in the riparian shrubland caused larger size classes of mesquite to be physiologically insensitive to monsoonal rains. In both shrublands, soil respiration was greatest beneath mesquite canopies and was coupled to shallow soil moisture abundance. Physiography, through its constraint on the physiological sensitivity of deeply rooted woody plants, may interact with plant‐mediated rates of soil respiration to affect the sensitivity of semiarid‐ecosystem carbon exchange in response to episodic rainfall.