A complex network of interactions controls coexistence and relative abundances in Patagonian grass-shrub steppes

The coexistence of shrubs and grasses has intrigued ecologists for the past century, and the conundrum of shrub-grass coexistence is at the core of debates on the functioning of semi-arid ecosystems. Here, we explored how the interplay of root competition and facilitation between life-forms at diffe...

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Otros Autores: Cipriotti, Pablo Ariel, Aguiar, Martín Roberto, Wiegand, Thorsten, Paruelo, José María
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Lenguaje:Español
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Acceso en línea:http://ri.agro.uba.ar/files/intranet/articulo/2014cipriotti.pdf
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Aporte de:Registro referencial: Solicitar el recurso aquí
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245 1 0 |a A complex network of interactions controls coexistence and relative abundances in Patagonian grass-shrub steppes 
520 |a The coexistence of shrubs and grasses has intrigued ecologists for the past century, and the conundrum of shrub-grass coexistence is at the core of debates on the functioning of semi-arid ecosystems. Here, we explored how the interplay of root competition and facilitation between life-forms at different life stages and demographic bottlenecks controls the long-term coexistence of multiple shrub and grass species in semi-arid Patagonian steppes. We used the spatially explicit and individual-based simulation model DINVEG that integrates the abundant information on the semi-arid Patagonian grass-shrub steppes to test six competing hypotheses on the mechanisms that govern the coexistence and relative abundances of several grass and shrub species. The structurally realistic model allows for a direct comparison of model outputs with a wide range of previously collected field data. We formulate three competing hypotheses on vertical root overlap between grasses and shrubs [no overlap, partial overlap, full overlap] that were crosses with two hypotheses on asymmetric shrub-grass facilitation [with and without]. Each of the six variants of DINVEG were tested in their ability to generate dynamics in accordance with detailed field data, and we performed global sensitivity analyses to reveal demographic bottlenecks and controls. The hypothesis combining partial vertical root overlap with no facilitation was the most likely hypothesis given the data. It created demographic bottlenecks in recruitment and emergence that controlled grass and shrub abundances, respectively, and only this hypothesis generated a situation where grasses controlled shrub abundances [by limiting shrub recruitment], but where grass abundance was only weakly controlled by shrubs. Internal water dynamics generated reduced competition of shrubs to neighboured grasses that was sufficient to produce the observed ring of grasses around shrubs, and most of the parameterizations that approximated the observed species-specific abundances were able to reproduce the observed equilibrated spatial patterns of the mature community. Synthesis. We found a complex network of mechanisms that controlled growth-form coexistence and relative abundances in the Patagonian grass-shrub steppe where both, demographic bottlenecks and species interactions across life-forms, species and life stages were important. Our study points to alternative mechanisms of shrub-grass coexistence that may play an important role in dry grasslands and steppes where fire and herbivory are not key drivers and provide an avenue to detect them. 
653 0 |a ARID ECOSYSTEMS 
653 0 |a ARID REGION 
653 0 |a BIOTIC FACTOR 
653 0 |a BIOTIC INTERACTIONS 
653 0 |a COEXISTENCE 
653 0 |a COMMUNITY STRUCTURE 
653 0 |a COMPETITION 
653 0 |a DETERMINANTS OF PLANT COMMUNITY DIVERSITY AND STRUCTURE 
653 0 |a ENVIRONMENTAL FACTOR 
653 0 |a FACILITATION 
653 0 |a GRASS 
653 0 |a HYPOTHESIS TESTING 
653 0 |a INDIVIDUAL-BASED MODEL 
653 0 |a INDIVIDUAL-BASED MODELS 
653 0 |a INTERSPECIFIC COMPETITION 
653 0 |a NICHE PARTITIONING 
653 0 |a NICHE SEPARATION 
653 0 |a PARAMETERIZATION 
653 0 |a PATAGONIA 
653 0 |a PLANT COMMUNITY 
653 0 |a PLANT DEMOGRAPHY 
653 0 |a PLANT-PLANT INTERACTIONS 
653 0 |a POACEAE 
653 0 |a POPULATION BOTTLENECK 
653 0 |a RELATIVE ABUNDANCE 
653 0 |a ROOT SYSTEM 
653 0 |a SEMIARID REGION 
653 0 |a SHRUB 
653 0 |a STEPPE 
700 1 |9 20940  |a Cipriotti, Pablo Ariel 
700 1 |9 12939  |a Aguiar, Martín Roberto 
700 1 |a Wiegand, Thorsten  |9 38577 
700 1 |9 788  |a Paruelo, José María 
773 |t Journal of Ecology  |g vol.102, no.3 (2014), p.776-788 
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