Resource Pulses, species interactions, and diversity maintenance in arid and semi-arid environments

Department of Biological Sciences, University of Denver, Denver, Colorado, United States
Oecologia (Impact Factor: 3.09). 11/2004; 141(2):236-53. DOI: 10.1007/s00442-004-1551-1
Source: PubMed


Arid environments are characterized by limited and variable rainfall that supplies resources in pulses. Resource pulsing is a special form of environmental variation, and the general theory of coexistence in variable environments suggests specific mechanisms by which rainfall variability might contribute to the maintenance of high species diversity in arid ecosystems. In this review, we discuss physiological, morphological, and life-history traits that facilitate plant survival and growth in strongly water-limited variable environments, outlining how species differences in these traits may promote diversity. Our analysis emphasizes that the variability of pulsed environments does not reduce the importance of species interactions in structuring communities, but instead provides axes of ecological differentiation between species that facilitate their coexistence. Pulses of rainfall also influence higher trophic levels and entire food webs. Better understanding of how rainfall affects the diversity, species composition, and dynamics of arid environments can contribute to solving environmental problems stemming from land use and global climate change.

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    • "Water and N are closely linked and commonly interact to limit ecosystem activity in semi-arid ecosystems (Hooper and Johnson, 1999). Water is the principal limiting factor restricting plant growth (Chesson et al., 2004). It also affects the amount and distribution of soil nutrients in arid and semi-arid ecosystems (Manzoni et al., 2012). "
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    ABSTRACT: The understanding of the seasonal dynamics of leaf nitrogen (N) relative to leaf traits for desert shrub species is limited. We investigated the seasonal changes in leaf N, soil N, specific leaf area (SLA) and photosynthetic capacity (Pmax) in relation to the phenology of Artemisia ordosica in a desert shrubland area in northern China during the growing season of year 2012. We found that the amount of leaf N per unit dry mass varied in different phenological phases, having higher values during the early leaf expansion and leaf coloration and early defoliation periods and lower values during the expanded leaf and flowering periods. Pmax was positively related to leaf N from the late leaf expansion period to the flowering and bearing period. Photosynthetic nitrogen use efficiency (NUE) correlated with SLA during the growing period. However, similar relationships were not observed for the leaf expansion and defoliation periods. During the flowering and bearing period, leaf N content per unit dry mass remained relatively stable, although fluctuations occurred due to precipitation. Our findings could help with modelling the dynamics of plant-soil N coupling of desert shrub-land ecosystems under changing environment.
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    • "Prior research suggests that not all vegetation types on this transect would equally utilize summer moisture in a " pulsedriven ecosystem, " where brief, intense rains are unpredictable with regards to timing, spatial coverage, and contribution of moisture towards annual total moisture amount (Ehleringer et al. 1998; Chesson et al. 2004; Schwinning and Sala 2004). Significant correlations between δ 2 H and MAP in previous transect studies have been attributed to less seasonally biased precipitation input than in this monsoon-influenced region (Sachse et al. 2006; Tipple and Pagani 2013). "
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    ABSTRACT: The use of hydrogen isotope ratios (δ(2)H) of sedimentary n-alkanes from leaf waxes has become an important tool for reconstructing paleoenvironmental and ancient hydrologic conditions. Studies of modern plant waxes can elucidate driving ecological mechanisms behind geologic deposits. Here, we used a transect across the North American Monsoon region of the western USA from Tucson, Arizona to Salt Lake City, Utah to study variations in leaf wax δ(2)H among co-occurring plants. Three co-occurring life forms were selected: perennial shrub (rabbit brush, Chrysothamnus nauseosus; sagebrush, Artemisia tridentata); tree (Gambel's oak tree, Quercus gambelii); and annual (sunflower, Helianthus annuus). Our results showed that the distributions and abundances of n-alkanes in perennial plants were similar across all sites and generally did not vary with environmental conditions (e.g., precipitation and temperature). In contrast, variations in n-alkane δ(2)H were significantly correlated with the fraction of the annual precipitation coming during the summer monsoon period. We use a modified Craig-Gordon model to speculate on the possible drivers of the δ(2)H values of leaf wax n-alkanes of plants across the region. The model results suggest that the most likely explanation for variation in wax δ(2)H values was a combination of seasonal source water usage and subsequent environmental conditions.
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    • "The Puna, high Andes and most likely other arid environments are predicted to change profoundly not only in average precipitation , but also in variability of precipitation. Between-and withinyear rainfall are both expected to become more variable (Chesson et al., 2004). Our ability to predict the responses of arid and semiarid ecosystems to these changes depends on being able to interpret the short-term responses of individuals and populations to precipitation. "
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