Primary Productivity and Water Use in Native Forest, Grassland, and Desert Ecosystems

Webb, Warren L.; Szarek, Stan R.; Lauenroth, William K.; Kinerson, Russell S.; Smith, Matthew D.

doi:10.2307/1938237

Cited by 246 publications

(173 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: 86%

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

Baldocchi

2004

Agricultural and Forest Meteorology

547

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: 86%

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

Baldocchi

2004

Agricultural and Forest Meteorology

547

350

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“…For example, the dry years of 1954 and 1964 were followed by years 401 of low forage production despite the fact that in both cases precipitation following the dry year was normal or above (Table 1). Such a lag in the recovery offorage production following a drought is likely the result of an interaction among population, community, and ecosystem processes (Webb et al 1978). The structure of the vegetation, as reflected in abundance of lifeforms and species and in the density of seeds and tillers, provides a constraint within which normal fluctuations in precipitation cause bounded fluctuations in production.…”

Section: Discussionmentioning

confidence: 99%

Long‐Term Forage Production of North American Shortgrass Steppe

Lauenroth

Sala

1992

Ecological Applications

612

515

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Abstract. We evaluated the relationship between annual forage production and annual and seasonal precipitation and temperature at a shortgrass steppe site in north-central Colorado using a long-term data set (52 yr). We also constructed a relationship between forage production and aboveground net primary production (ANPP). Precipitation fluctuated randomly, but temperature had clear warming and cooling trends including a 17-yr warming trend from 1974 to 1990.Forage production was significantly related to both annual and seasonal precipitation but not temperature. Precipitation events between 15 and 30 mm accounted for most of the variability in production because they accounted for most of the variability in precipitation and because they wetted the soil layers that have the largest effect on production. Forage production amplified variability in annual precipitation.Production showed time lags of several years in responding to increases in precipitation. Change in vegetation structure has a characteristic response time, which contrains production responses in wet years. Constraint caused by vegetation structure is the reason why regional ANPP-precipitation models have a steeper slope than long-term models and point out a weakness of exchanging space for time in predicting production patterns.

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“…This material derives from primary and secondary contexts, ranging from crops stored in pots in small storage rooms of high-status late Early Jazira (EJ) III (c. 2400 cal BC) households destroyed by fire in areas CH and ER, to an Akkadian public building ('Southern Building') (c. 2300-2200 cal BC) in area FS and post-Akkadian (c. 2200-1950 cal BC) domestic contexts (Oates, Oates, and McDonald 2001, 15-98). As in other semi-arid regions (mean annual rainfall 300-600 mm; FAO 1987;Noy-Meir 1973;Webb et al 1978), rain-fed farming is possible in northern Mesopotamia, but water is the major limitation to growth. We have estimated Brak's EBA rainfall as c. 310-450 mm pa, using δ The landscape around the site does not lend itself to large-scale irrigation but would encompass variable soil moisture, with better watered soils along wadis a few km to the south and east (Wilkinson et al 2001).…”

Section: Application Of the Model To Archaeobotanical Data From Bronzmentioning

confidence: 99%

From Traditional Farming in Morocco to Early Urban Agroecology in Northern Mesopotamia: Combining Present-day Arable Weed Surveys and Crop Isotope Analysis to Reconstruct Past Agrosystems in (Semi-)arid Regions

Bogaard

Styring

Ater

et al. 2016

Environmental Archaeology

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We integrate functional weed ecology with crop stable carbon and nitrogen isotope analysis to assess their combined potential for inferring arable land management practices in (semi-)arid regions from archaeobotanical assemblages. Weed and GIS survey of 60 cereal and pulse fields in Morocco are combined with crop sampling for stable isotope analysis to frame assessment of agricultural labour intensity in terms of manuring, irrigation, tillage and handweeding. Under low management intensity weed variation primarily reflects geographical differences, whereas under high management intensity fields in disparate regions have similar weed flora. Manured and irrigated oasis barley fields are clearly discriminated from less intensively manured rain-fed barley terraces in southern Morocco; when fields in northern and southern Morocco are considered together, climatic differences are superimposed on the agronomic intensity gradient. Barley δ 13 C and δ 15 N values clearly distinguish among the Moroccan regimes. An integrated approach combines crop isotope values with weed ecological discrimination of low-and high-intensity regimes across multiple studies (in southern Morocco and southern Europe). Analysis of archaeobotanical samples from EBA Tell Brak, Syria suggests that this early city was sustained through extensive (low-intensity, large-scale) cereal farming. ARTICLE HISTORY

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Primary Productivity and Water Use in Native Forest, Grassland, and Desert Ecosystems

Cited by 246 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

Long‐Term Forage Production of North American Shortgrass Steppe

From Traditional Farming in Morocco to Early Urban Agroecology in Northern Mesopotamia: Combining Present-day Arable Weed Surveys and Crop Isotope Analysis to Reconstruct Past Agrosystems in (Semi-)arid Regions

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