Structure and function of C3and C4Chihuahuan Desert plant communities. Energy balance components

Dugas, William A.; Hicks, R. A.; Gibbens, Robert P.

doi:10.1006/jare.1996.0093

Cited by 53 publications

(66 citation statements)

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“…For vegetation canopies, τ 1 and τ 2 are larger than for bare soil because the transpiration process is added to the evaporation and slows the decrease of EF. Dugas et al (1996) observed qualitatively similar differences over arid surfaces in the southwestern United States. τ 2 ranges from 1.7 to 5.5 days and can be compared to a value of 2 days found by Kurc and Small (2004).…”

Section: Surface Recoverysupporting

confidence: 53%

“…Rainfall is characterized by high intermittency and large spatial variability, as well as high temporal variability at the synoptic, intraseasonal, interannual and multidecadal timescales Nicholson, 2013). Land-atmosphere exchanges and surface fluxes are impacted by rainfall variability at all scales, either as a direct response to soil water availability or through vegetation changes, and have been identified as major influences on climate and weather in West Africa (Eltahir and Gong, 1996;Zeng et al, 1999;Koster et al, 2004;Taylor et al, 2011b). Recent results demonstrated that convection triggering, which is a critical process in the tropics, was significantly enhanced by mesoscale heterogeneity of surface soil moisture (Taylor et al, 2011a(Taylor et al, , 2012.…”

Section: Introductionmentioning

confidence: 99%

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Surface response to rain events throughout the West African monsoon

et al. 2014

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Abstract. This study analyses the response of the continental surface to rain events, taking advantage of the longterm near-surface measurements over different vegetation types at different latitudes, acquired during the African Monsoon Multidisciplinary Analysis (AMMA) by the AMMA-CATCH observing system. The simulated surface response by nine land surface models involved in AMMA Land Model Intercomparison Project (ALMIP), is compared to the observations. The surface response, described via the evaporative fraction (EF), evolves in two steps: the immediate surface response (corresponding to an increase of EF occurring immediately after the rain) and the surface recovery (characterized by a decrease of EF over several days after the rain). It is shown that, for all the experimental sites, the immediate surface response is mainly dependent on the soil moisture content and the recovery period follows an exponential relationship whose rate is strongly dependent on the vegetation type (from 1 day over bare soil to 70 days over forest) and plant functional type (below and above 10 days for annual and perennial plants, respectively). The ALMIP model ensemble depicts a broad range of relationships between EF and soil moisture, with the worst results for the drier sites (high latitudes). The land surface models tend to simulate a realistic surface recovery for vegetated sites, but a slower and more variable EF decrease is simulated over bare soil than observed.

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Section: Surface Recoverysupporting

confidence: 53%

Section: Introductionmentioning

confidence: 99%

Surface response to rain events throughout the West African monsoon

et al. 2014

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“…Bare-soil evaporation was not measured independently in this study owing to our lack of recording microlysimeters and the difficulties in obtaining a spatially-representative estimate for an entire growing season from small-scale micro-lysimeters. Nevertheless, it is a common practice to estimate a component flux as a residual (Barbour et al, 2005;Dugas et al, 1996;Scott et al, 2003;Williams et al, 2004), and we can check whether the independent estimates of T and ET are compatible. As the time from the last precipitation event increased in an interstorm period, it is reasonable to expect that T increasingly dominates an ET signal because surface soil rapidly dries, increasing the resistance to water flux from deeper layers despite a large demand from the atmosphere (Wythers et al, 1999).…”

Section: Transpiration and Evaporationmentioning

confidence: 99%

“…On an annual basis this ratio would decrease owing to the dormancy of the shrubs in the colder winter months. Following several rain events, Dugas et al (1996) found that average T/ET ranged from 40-70% over several different Chihuahuan shrub sites in New Mexico. Kemp et al (1997) simulated the annual ET partitioning of several different Chihuahuan Desert communities and found that annual T/ET was about 40% for a creosote community with 30% peak cover, but T/ET increased to 60% in a mixed community with about 60% cover.…”

Section: Evapotranspiration Partitioningmentioning

confidence: 99%

“…Ecosystem ET has been partitioned into bare-soil evaporation, interception reservoir evaporation, and transpiration from the overstory and understory vegetation (e.g. Barbour et al, 2005;Dugas et al, 1996;Ham et al, 1990;Scott et al, 2003;Williams et al, 2004;Yepez et al, 2003). Often, these studies have been over relatively short time periods (days to weeks) and data for woody plant encroached areas are sparse.…”

Section: Introductionmentioning

confidence: 99%

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Partitioning of evapotranspiration and its relation to carbon dioxide exchange in a Chihuahuan Desert shrubland

Scott

Huxman

Cable

et al. 2006

Hydrological Processes

194

154

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Key to evaluating the consequences of woody plant encroachment on water and carbon cycling in semiarid ecosystems is a mechanistic understanding of how biological and non-biological processes influence water loss to the atmosphere. To better understand how precipitation is partitioned into the components of evapotranspiration (bare-soil evaporation and plant transpiration) and their relationship to plant uptake of carbon dioxide (CO 2 ) as well as ecosystem respiratory efflux, we measured whole plant transpiration, evapotranspiration, and CO 2 fluxes over the course of a growing season at a semiarid Chihuahuan Desert shrubland site in south-eastern Arizona. Whole plant transpiration was measured using the heat balance sap-flow method, while evapotranspiration and net ecosystem exchange (NEE) of CO 2 were quantified using the Bowen ratio technique.Before the summer rainy season began, all water and CO 2 fluxes were small. At the onset of the rainy season, evapotranspiration was dominated by evaporation and CO 2 fluxes were dominated by respiration as it took approximately 10 days for the shrubs to respond to the higher soil moisture content. During the growing season, periods immediately following rain events (<2 days) were dominated by evaporation and respiration while transpiration and CO 2 uptake peaked during the interstorm periods. The surface of the coarse, well-drained soils dried quickly, rapidly reducing evaporation. Overall, the ratio of total transpiration to evapotranspiration was 58%, but it was around 70% during the months when the plants were active. Peak respiration responses following rain events generally lagged after the evaporation peak by a couple of days and were better correlated with transpiration. Transpiration and CO 2 uptake also decayed rather quickly during interstorm periods, indicating that optimal plant soil moisture conditions were rarely encountered. NEE of CO 2 was increasingly more negative as the growing season progressed, indicating a greater net uptake of CO 2 and greater water use efficiency due mainly to decreases in respiration.

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The impact of neogene grassland expansion and aridification on the isotopic composition of continental precipitation

Chamberlain

Winnick

Mix

et al. 2014

Global Biogeochemical Cycles

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The late Cenozoic was a time of global cooling, increased aridity, and expansion of grasslands. In the last two decades numerous records of oxygen isotopes have been collected to assess plant ecological changes, understand terrestrial paleoclimate, and to determine the surface history of mountain belts. The δ18 O values of these records, in general, increase from the mid-Miocene to the Recent. We suggest that these records record an increase in aridity and expansion of grasslands in midlatitude continental regions. We use a nondimensional isotopic vapor transport model coupled with a soil water isotope model to evaluate the role of vapor recycling and transpiration by different plant functional types. This analysis shows that increased vapor recycling associated with grassland expansion along with biomechanistic changes in transpiration by grasses themselves conspires to lower the horizontal gradient in the δ 18O of atmospheric vapor as an air mass moves into continental interiors. The resulting signal at a given inland site is an increase in δ 18O of precipitation with the expansion of grasslands and increasing aridity, matching the general observed trend in terrestrial Cenozoic δ 18O records. There are limits to the isotopic effect that are induced by vapor recycling, which we refer to here as a "hydrostat." In the modern climate, this hydrostatic limit occurs at approximately the boundary between forest and grassland ecosystems.

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Structure and function of C3and C4Chihuahuan Desert plant communities. Energy balance components

Cited by 53 publications

References 0 publications

Surface response to rain events throughout the West African monsoon

Surface response to rain events throughout the West African monsoon

Partitioning of evapotranspiration and its relation to carbon dioxide exchange in a Chihuahuan Desert shrubland

The impact of neogene grassland expansion and aridification on the isotopic composition of continental precipitation

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