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

Section of Evolution and Ecology, University of California, Davis 95616, USA.
Oecologia (Impact Factor: 3.25). 11/2004; 141(2):236-53. DOI: 10.1007/s00442-004-1551-1
Source: PubMed

ABSTRACT 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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Available from: Peter Chesson, Jul 28, 2015
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    • "Furthermore , the short life cycle of these annual species allowed us to cover entire ontogenetic plant development, avoiding misleading results due to changes in the magnitude and direction of interactions throughout the life stages of the co-occurring plants (Holzapfel & Mahall 1999; Luzuriaga & Escudero 2008). Water pulses can also largely determine plant assemblages in semi-arid environments (Chesson et al. 2004; Miranda et al. 2011), particularly in those dominated by annuals (Venable et al. 1993; Pake & Venable 1995; Rivas- Arancibia et al. 2006). Some perennial neighbours act as biotic filters in annual plant assemblages (Facelli & Temby 2002; Armas & Pugnaire 2011). "
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    ABSTRACT: Questions: Does edaphic heterogeneity (i.e. switches between gypsum and cal-careous soils) affect annual plant community assembly in highly restrictive soils? Our main hypothesis is that soil filtering is the main determinant of species assembly, subsequently modulated by climate and lastly by biotic interactions, such as Stipa tenacissima and the biological soil crust (BSC) at fine spatial scales. Our study system is highly suitable to test the importance of edaphic heteroge-neity to the assembly of annual plant communities, since calcareous and gyp-sum soils are in close contact and freely receive propagules. Location: Annual plant communities of semi-arid steppes in central Spain. Methods: We built a soil affinity index (SAI) for each species to measure mean soil affinity (MSA; analogous to the community-weighted mean – CWM) in each local assemblage. Results: Most species were able to establish in both substrates, but gypsum soils clearly exerted a stronger filtering effect. Stipa favoured an expansion of the niche space in calcareous soils but not in gypsum, and BSCs not only reduced annual species richness, diversity and cover, but also the range of SAI values of local assemblages. Conclusions: This study highlights the importance of the probabilistic filtering (sensu From plant traits to vegetation structure, 2010, Cambridge University Press, Cambridge, UK) of soil characteristics to the assembly of annual plant communities , as opposed to an 'all-or-nothing' filter.
    Journal of Vegetation Science 03/2015; DOI:10.1111/jvs.1228 · 3.37 Impact Factor
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    • "Furthermore , the short life cycle of these annual species allowed us to cover entire ontogenetic plant development, avoiding misleading results due to changes in the magnitude and direction of interactions throughout the life stages of the co-occurring plants (Holzapfel & Mahall 1999; Luzuriaga & Escudero 2008). Water pulses can also largely determine plant assemblages in semi-arid environments (Chesson et al. 2004; Miranda et al. 2011), particularly in those dominated by annuals (Venable et al. 1993; Pake & Venable 1995; Rivas- Arancibia et al. 2006). Some perennial neighbours act as biotic filters in annual plant assemblages (Facelli & Temby 2002; Armas & Pugnaire 2011). "
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    ABSTRACT: QuestionsDoes edaphic heterogeneity (i.e. switches between gypsum and calcareous soils) affect annual plant community assembly in highly restrictive soils? Our main hypothesis is that soil filtering is the main determinant of species assembly, subsequently modulated by climate and lastly by biotic interactions, such as Stipa tenacissima and the biological soil crust (BSC) at fine spatial scales. Our study system is highly suitable to test the importance of edaphic heterogeneity to the assembly of annual plant communities, since calcareous and gypsum soils are in close contact and freely receive propagules.LocationAnnual plant communities of semi-arid steppes in central Spain.Methods We built a soil affinity index (SAI) for each species to measure mean soil affinity (MSA; analogous to the community-weighted mean – CWM) in each local assemblage.ResultsMost species were able to establish in both substrates, but gypsum soils clearly exerted a stronger filtering effect. Stipa favoured an expansion of the niche space in calcareous soils but not in gypsum, and BSCs not only reduced annual species richness, diversity and cover, but also the range of SAI values of local assemblages.Conclusions This study highlights the importance of the probabilistic filtering (sensu From plant traits to vegetation structure, 2010, Cambridge University Press, Cambridge, UK) of soil characteristics to the assembly of annual plant communities, as opposed to an ‘all-or-nothing’ filter.
    Journal of Vegetation Science 02/2015; DOI:10.1111/jvs.12285 · 3.37 Impact Factor
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    • "To this pair of definitions we now add a third that logically belongs with them, which is (iii) partitioning of recruitment opportunities among years caused by species specializing on particular patterns of temporal variance of water supply. This can promote coexistence through the temporal storage effect (Chesson et al. 2004). "
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    ABSTRACT: 1.Despite the fundamental significance of water to plants and the persisting question of how competing species coexist, this is the first review of hydrological niches. We define hydrological niche segregation (HNS) as: (i) partitioning of space on fine-scale soil-moisture gradients, (ii) partitioning of water as a resource, and/or (iii) partitioning of recruitment opportunities among years caused by species specializing on particular patterns of temporal variance of water supply (the storage effect).2.We propose that there are three types of constraint that lead to the trade-offs that underlie HNS. (i) An edaphic constraint creates a trade-off between the supply to roots of O2 on the one hand vs. water and nutrients on the other. (ii) A biophysical constraint governs gas exchange by leaves, leading to a trade-off between CO2 acquisition vs. water loss. (iii) A structural constraint arising from the physics of water-conducting tissues leads to a safety vs. efficiency trade-off.3.Significant HNS was found in 43/48 field studies across vegetation types ranging from arid to wet, though its role in coexistence remains to be proven in most cases. Temporal partitioning promotes coexistence through the storage effect in arid plant communities, but has yet to be shown elsewhere. In only a few cases is it possible to unequivocally link HNS to a particular trade-off.5.Synthesis. The field and experimental evidence make it clear that HNS is widespread, though it is less clear what its precise mechanisms or consequences are. HNS mechanisms should be revealed by further study of the constraints and trade-offs that govern how plants obtain and use water and HNS can be mechanistically linked to its consequences with appropriate community models. In a changing climate, such an integrated programme would pay dividends for global change research.This article is protected by copyright. All rights reserved.
    Journal of Ecology 10/2014; 103(1). DOI:10.1111/1365-2745.12332 · 5.69 Impact Factor
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