Response of a Grassland Cactus to Frequency and Size of Rainfall Events in a North American Shortgrass Steppe

Dougherty, R. L.; Lauenroth, W. K.; Singh, J. S.

doi:10.2307/2261353

Cited by 42 publications

(33 citation statements)

References 26 publications

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“…Increased grass biomass in a dry year, following high productivity in wet years, may increase fuel load and Wre frequency that could reduce shrub persistence if Wres occur in the community (Kirkman et al 2001;Heisler et al 2003). Although we did not observe changes in succulent species richness and density over the 5-year period, they may decline if future precipitation regimes favor higher grass densities, which have been shown to reduce succulent establishment (Dougherty et al 1996;Powell and Weedin 2004).…”

Section: Resultscontrasting

confidence: 51%

“…Typically, long-lived and deep-rooted shrubs such as those in the sotol grassland respond slowly to alterations in precipitation and water availability (Huenneke et al 2002;Yahdjian and Sala 2006;Robertson et al 2009). Similarly, the water storage capacity of succulents confounds their responses to increased seasonal precipitation due to the potentially long lag periods between precipitation events (Dougherty et al 1996;Adler and Levine 2007;Robertson et al 2009). Buonopane et al (2005) conducted a 5-year experiment on the response of a Chihuahuan Desert shrubland community to the removal of diVerent plant functional groups and found that shrubs and succulents were generally not responsive; this suggests recovery from alterations in the environment could take decades.…”

Section: Functional Group Responses To Seasonal and Supplemental Precmentioning

confidence: 99%

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Precipitation magnitude and timing differentially affect species richness and plant density in the sotol grassland of the Chihuahuan Desert

2009

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Arid and semi-arid environments are dynamic ecosystems with highly variable precipitation, resulting in diverse plant communities. Changes in the timing and magnitude of precipitation due to global climate change may further alter plant community composition in desert regions. In this study, we assessed changes in species richness and plant density at the community, functional group, and species level in response to variation in the magnitude of natural seasonal precipitation and 25% increases in seasonal precipitation [e.g., supplemental watering in summer, winter, or summer and winter (SW)] over a 5-year period in a sotol grassland in the Chihuahuan Desert. Community species richness was higher with increasing winter precipitation while community plant density increased with greater amounts of winter and summer precipitation, suggesting winter precipitation was important for species recruitment and summer precipitation promoted growth of existing species. Herb and grass density increased with increasing winter and summer precipitation, but only grass density showed a significant response to supplemental watering treatments (SW treatment plots had higher grass density). Shrubs and succulents did not exhibit changes in richness or density in response to natural or supplemental precipitation. In this 5-year study, changes in community species richness and density were driven by responses of herb and grass species that favored more frequent small precipitation events, shorter inter-pulse duration, and higher soil moisture. However, due to the long life spans of the shrub and succulent species within this community, 5 years may be insufficient to accurately evaluate their response to variable timing and magnitude of precipitation in this mid-elevation grassland.

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Section: Resultscontrasting

confidence: 51%

Section: Functional Group Responses To Seasonal and Supplemental Precmentioning

confidence: 99%

Precipitation magnitude and timing differentially affect species richness and plant density in the sotol grassland of the Chihuahuan Desert

2009

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“…For example, plains prickly pear (Opuntia polyacantha Haw. ), which occurs extensively throughout the shortgrass steppe, maintains a very super®cial ®ne-root network in the surface soil layers, enabling it to exploit small (<5 mm) rainfall events (Dougherty et al 1996). The conceptual expansion of the two-layer/two life-form model to a three-layer/three life-form model and beyond may be more appropriate for complex communities.…”

Section: Discussionmentioning

confidence: 99%

Differential water resource use by herbaceous and woody plant life-forms in a shortgrass steppe community

1998

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We conducted a study to test the predictions of Walter's two-layer model in the shortgrass steppe of northeastern Colorado. The model suggests that grasses and woody plants use water resources from different layers of the soil profile. Four plant removal treatments were applied in the spring of 1996 within a plant community codominated by Atriplex canescens (a C shrub) and Bouteloua gracilis (a C grass). During the subsequent growing season, soil water content was monitored to a depth of 180 cm. In addition, stem and leaf tissue of Atriplex, Bouteloua and the streamside tree Populus sargentii were collected monthly during the growing seasons of 1995 and 1996 for analysis of the δO value of plant stem water (for comparison with potential water sources) and the δC value of leaves (as an indicator of plant water status). Selective removal of shrubs did not significantly increase water storage at any depth in the measured soil profile. Selective removal of the herbaceous understory (mainly grasses) increased water storage in the top 60 cm of the soil. Some of this water gradually percolated to lower layers, where it was utilized by the shrubs. Based on stem water δO values, grasses were exclusively using spring and summer rain extracted from the uppermost soil layers. In contrast, trees were exclusively using groundwater, and the consistent δC values of tree leaves over the course of the summer indicated no seasonal changes in gas exchange and therefore minimal water stress in this life-form. Based on anecdotal rooting-depth information and initial measurements of stem water δO, shrubs may have also had access to groundwater. However, their overall δO values indicated that they mainly used water from spring and summer precipitation events, extracted from subsurface soil layers. These findings indicate that the diversity of life-forms found in this shortgrass steppe community may be a function of the spatial partitioning of soil water resources, and their differential use by grasses, shrubs, and trees. Consequently, our findings support the two-layer model in a broad sense, but indicate a relatively flexible strategy of water acquisition by shrubs.

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“…Likewise, succulents quickly produce new rain roots (Nobel and Sanderson 1984;Nobel 1988) and increase stomatal conductance (Szarek and Ting 1975;Nobel 1976;Green and Williams 1982) and stem water storage after small pulse events (Nobel 1988;Dougherty et al 1996). These characteristics would confer a relatively high rain use efficiency to these classes of plants by minimizing delay times during which water would only be lost by evaporation, and by utilizing a greater portion of the rainfall size distribution.…”

Section: Plant Functional Types and Precipitation Pulsesmentioning

confidence: 99%

Precipitation pulses and carbon fluxes in semiarid and arid ecosystems

et al. 2004

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In the arid and semiarid regions of North America, discrete precipitation pulses are important triggers for biological activity. The timing and magnitude of these pulses may differentially affect the activity of plants and microbes, combining to influence the C balance of desert ecosystems. Here, we evaluate how a "pulse" of water influences physiological activity in plants, soils and ecosystems, and how characteristics, such as precipitation pulse size and frequency are important controllers of biological and physical processes in arid land ecosystems. We show that pulse size regulates C balance by determining the temporal duration of activity for different components of the biota. Microbial respiration responds to very small events, but the relationship between pulse size and duration of activity likely saturates at moderate event sizes. Photosynthetic activity of vascular plants generally increases following relatively larger pulses or a series of small pulses. In this case, the duration of physiological activity is an increasing function of pulse size up to events that are infrequent in these hydroclimatological regions. This differential responsiveness of photosynthesis and respiration results in arid ecosystems acting as immediate C sources to the atmosphere following rainfall, with subsequent periods of C accumulation should pulse size be sufficient to initiate vascular plant activity. Using the average pulse size distributions in the North American deserts, a simple modeling exercise shows that net ecosystem exchange of CO2 is sensitive to changes in the event size distribution representative of wet and dry years. An important regulator of the pulse response is initial soil and canopy conditions and the physical structuring of bare soil and beneath canopy patches on the landscape. Initial condition influences responses to pulses of varying magnitude, while bare soil/beneath canopy patches interact to introduce nonlinearity in the relationship between pulse size and soil water response. Building on this conceptual framework and developing a greater understanding of the complexities of these eco-hydrologic systems may enhance our ability to describe the ecology of desert ecosystems and their sensitivity to global change.

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Response of a Grassland Cactus to Frequency and Size of Rainfall Events in a North American Shortgrass Steppe

Cited by 42 publications

References 26 publications

Precipitation magnitude and timing differentially affect species richness and plant density in the sotol grassland of the Chihuahuan Desert

Precipitation magnitude and timing differentially affect species richness and plant density in the sotol grassland of the Chihuahuan Desert

Differential water resource use by herbaceous and woody plant life-forms in a shortgrass steppe community

Precipitation pulses and carbon fluxes in semiarid and arid ecosystems

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