Grassland Precipitation-Use Efficiency Varies Across a Resource Gradient

Paruelo, José M.; Lauenroth, William K.; Burke, Ingrid C.; Sala, Osvaldo E.

doi:10.1007/s100219900058

Cited by 281 publications

(351 citation statements)

References 24 publications

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“…Depending on precipitation, more carbon uptake occurs during wet years and vice versa (Flanagan et al, 2002;Meyers, 2001;Suyker et al, 2003). These physiological results, based on the eddy covariance method, are consistent with numerous ecological studies, which have shown that aboveground net primary production (ANPP) of grasslands growing in the continental region of North America is correlated linearly with annual precipitation (Sims and Singh, 1978;Webb et al, 1978;Sala et al, 1988;Paruelo et al, 1999;Lauenroth and Sala, 1992;Knapp and Smith, 2001).…”

Section: Introductionsupporting

confidence: 72%

Seasonal variation in carbon dioxide exchange over a Mediterranean annual grassland in California

Baldocchi

2004

Agricultural and Forest Meteorology

538

350

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Understanding how environmental variables affect the processes that regulate the carbon flux over grassland is critical for large-scale modeling research, since grasslands comprise almost one-third of the earth's natural vegetation. To address this issue, fluxes of CO 2 (F c , flux toward the surface is negative) were measured over a Mediterranean, annual grassland in California, USA for 2 years with the eddy covariance method.To interpret the biotic and abiotic factors that modulate F c over the course of a year we decomposed net ecosystem CO 2 exchange into its constituent components, ecosystem respiration (R eco ) and gross primary production (GPP). Daytime R eco was extrapolated from the relationship between temperature and nighttime F c under high turbulent conditions. Then, GPP was estimated by subtracting daytime values of F c from daytime estimates of R eco .Results show that most of carbon exchange, both photosynthesis and respiration, was limited to the wet season (typically from October to mid-May). Seasonal variations in GPP followed closely to changes in leaf area index, which in turn was governed by soil moisture, available sunlight and the timing of the last frost. In general, R eco was an exponential function of soil temperature, but with season-dependent values of Q 10 . The temperature-dependent respiration model failed immediately after rain events, when large pulses of R eco were observed. Respiration pulses were especially notable during the dry season when the grass was dead and were the consequence of quickly stimulated microbial activity.Integrated values of GPP, R eco , and net ecosystem exchange (NEE) were 867, 735, and −132 g C m −2 , respectively, for the 2000-2001 season, and 729, 758, and 29 g C m −2 for the 2001-2002 season. Thus, the grassland was a moderate carbon sink during the first season and a weak carbon source during the second season. In contrast to a well-accepted view that annual production of grass is linearly correlated to precipitation, the large difference in GPP between the two seasons were not caused by the annual precipitation. Instead, a shorter growing season, due to late start of the rainy season, was mainly responsible for the lower GPP in the second season. Furthermore, relatively higher R eco during the non-growing season occurred after a late spring rain. Thus, for this Mediterranean grassland, the timing of rain events had more impact than the total amount of precipitation on ecosystem GPP and NEE. This is because its growing season is in the cool and wet season when carbon uptake and respiration are usually limited by low temperature and sometimes frost, not by soil moisture.

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Section: Introductionsupporting

confidence: 72%

Seasonal variation in carbon dioxide exchange over a Mediterranean annual grassland in California

Baldocchi

2004

Agricultural and Forest Meteorology

538

350

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“…These results were consistent with a previous study that found that RUE decreased with increasing annual precipitation from an analysis of a 24-year dataset in the typical steppe (Bai et al 2008). Our results supported previous work that RUE decreased over time with increasing annual precipitation (Paruelo et al 1999;Lauenroth et al 2000).…”

Section: Response Of Anpp To Annual Precipitationsupporting

confidence: 83%

Response of the annual biomass production of a typical steppe plant community to precipitation fluctuations

et al. 2014

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Abstract. Understanding the relationship between the aboveground net primary production (ANPP) and annual precipitation in arid and semiarid grasslands is crucial for assessing the effects of climate change on grassland ecosystems. The temporal pattern of ANPP, based on long-term data on a semiarid ecosystem in Inner Mongolia, was investigated. The biomass of perennial grasses, perennial forbs and Stipa grandis P. Smirn., showed a positive relationship with annual precipitation. The amount of annual precipitation also changed the annual biomass of 13 other dominant species and consequently the ANPP. The coefficient of variation of the ANPP of the plant community was lower than the coefficient of variation of annual precipitation. Irrespective of the strong inter-annual variation in annual precipitation, the positive relationship found between ANPP and annual precipitation suggests the dependence of ANPP upon hydrological variations in typical steppe. Our findings highlight the importance of dominant perennial species and functional groups in mediating the responses of ANPP to annual precipitation in the typical steppe in northern China.

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“…Rainfall-use efficiency (biomass production by plants as a function of precipitation) has been an important variable describing function in water-limited systems (Le Houerou, 1984;Paruelo et al, 1999), but there have been difficulties relating the eco-physiological characteristics of vegetation to ecosystem processes owing to the fact that precipitation is not completely consumed by vegetation (Huxman et al, 2004c). At the leaf scale, water use efficiency has been computed in many different ways (e.g.…”

Section: Relationships Between Components Of Et and Neementioning

confidence: 99%

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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Grassland Precipitation-Use Efficiency Varies Across a Resource Gradient

Cited by 281 publications

References 24 publications

Seasonal variation in carbon dioxide exchange over a Mediterranean annual grassland in California

Seasonal variation in carbon dioxide exchange over a Mediterranean annual grassland in California

Response of the annual biomass production of a typical steppe plant community to precipitation fluctuations

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

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