Shifts in positive and negative plant interactions along a grazing intensity gradient
Isolating the single effects and net balance of negative and positive species effects in complex interaction networks is a necessary step for understanding community dynamics. Facilitation and competition have both been found to operate in harsh environments, but their relative strength may be predi...
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2007
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| Acceso en línea: | https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00129658_v88_n1_p188_Graff http://hdl.handle.net/20.500.12110/paper_00129658_v88_n1_p188_Graff |
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paper:paper_00129658_v88_n1_p188_Graff2023-06-08T14:35:37Z Shifts in positive and negative plant interactions along a grazing intensity gradient Associational defenses Biotic refuges Bromus pictus Facilitation Grazing intensity Herbivory Indirect interactions Patagonian steppe Plant traits Poa ligularis Root competition Stipa speciosa antiherbivore defense arid environment biomass community dynamics environmental stress facilitation grass grazing herbivory interspecific competition plant community plant-herbivore interaction remediation root competition sheep animal Argentina article Bromus ecosystem plant Poa Poaceae sheep Animals Argentina Bromus Ecosystem Plants, Edible Poa Poaceae Sheep Achnatherum speciosum Bromus Bromus pictus Ovis aries Poa Poa ligularis Poaceae Stipa Isolating the single effects and net balance of negative and positive species effects in complex interaction networks is a necessary step for understanding community dynamics. Facilitation and competition have both been found to operate in harsh environments, but their relative strength may be predicted to change along gradients of herbivory. Moreover, facilitation effects through habitat amelioration and protection from herbivory may act together determining the outcome of neighborhood plant-plant interactions. We tested the hypothesis that grazing pressure alters the balance of positive and negative interactions between palatable and unpalatable species by increasing the strength of positive indirect effects mediated by associational resistance to herbivory. We conducted a two-year factorial experiment in which distance (i.e., spatial association) from the nearest unpalatable neighbor (Stipa speciosa) and root competition were manipulated for two palatable grasses (Poa ligularis and Bromus pictus), at three levels of sheep grazing (none, moderate, and high) in a Patagonian steppe community. We found that grazing shifted the effect of Stipa on both palatable grasses, from negative (competition) in the absence of grazing to positive (facilitation) under increasing herbivore pressure. In ungrazed sites, belowground competition was the dominant interaction, as shown by a significant reduction in performance of palatable grasses transplanted near to Stipa tussocks. In grazed sites, biomass of palatable plants was greater near than far from Stipa regardless of competition treatment. Proximity to Stipa reduced the amount of herbivory suffered by palatable grasses, an indirect effect that was stronger under moderate than under intense grazing. Our results demonstrate that facilitation, resulting mainly from protection against herbivory, is the overriding effect produced by unpalatable neighbors on palatable grasses in this rangeland community. This finding challenges the common view that abiotic stress amelioration should be the predominant type of facilitation in arid environments and highlights the role of herbivory in modulating complex neighborhood plant interactions in grazing systems. © 2007 by the Ecological Society of America. 2007 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00129658_v88_n1_p188_Graff http://hdl.handle.net/20.500.12110/paper_00129658_v88_n1_p188_Graff |
| institution |
Universidad de Buenos Aires |
| institution_str |
I-28 |
| repository_str |
R-134 |
| collection |
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) |
| topic |
Associational defenses Biotic refuges Bromus pictus Facilitation Grazing intensity Herbivory Indirect interactions Patagonian steppe Plant traits Poa ligularis Root competition Stipa speciosa antiherbivore defense arid environment biomass community dynamics environmental stress facilitation grass grazing herbivory interspecific competition plant community plant-herbivore interaction remediation root competition sheep animal Argentina article Bromus ecosystem plant Poa Poaceae sheep Animals Argentina Bromus Ecosystem Plants, Edible Poa Poaceae Sheep Achnatherum speciosum Bromus Bromus pictus Ovis aries Poa Poa ligularis Poaceae Stipa |
| spellingShingle |
Associational defenses Biotic refuges Bromus pictus Facilitation Grazing intensity Herbivory Indirect interactions Patagonian steppe Plant traits Poa ligularis Root competition Stipa speciosa antiherbivore defense arid environment biomass community dynamics environmental stress facilitation grass grazing herbivory interspecific competition plant community plant-herbivore interaction remediation root competition sheep animal Argentina article Bromus ecosystem plant Poa Poaceae sheep Animals Argentina Bromus Ecosystem Plants, Edible Poa Poaceae Sheep Achnatherum speciosum Bromus Bromus pictus Ovis aries Poa Poa ligularis Poaceae Stipa Shifts in positive and negative plant interactions along a grazing intensity gradient |
| topic_facet |
Associational defenses Biotic refuges Bromus pictus Facilitation Grazing intensity Herbivory Indirect interactions Patagonian steppe Plant traits Poa ligularis Root competition Stipa speciosa antiherbivore defense arid environment biomass community dynamics environmental stress facilitation grass grazing herbivory interspecific competition plant community plant-herbivore interaction remediation root competition sheep animal Argentina article Bromus ecosystem plant Poa Poaceae sheep Animals Argentina Bromus Ecosystem Plants, Edible Poa Poaceae Sheep Achnatherum speciosum Bromus Bromus pictus Ovis aries Poa Poa ligularis Poaceae Stipa |
| description |
Isolating the single effects and net balance of negative and positive species effects in complex interaction networks is a necessary step for understanding community dynamics. Facilitation and competition have both been found to operate in harsh environments, but their relative strength may be predicted to change along gradients of herbivory. Moreover, facilitation effects through habitat amelioration and protection from herbivory may act together determining the outcome of neighborhood plant-plant interactions. We tested the hypothesis that grazing pressure alters the balance of positive and negative interactions between palatable and unpalatable species by increasing the strength of positive indirect effects mediated by associational resistance to herbivory. We conducted a two-year factorial experiment in which distance (i.e., spatial association) from the nearest unpalatable neighbor (Stipa speciosa) and root competition were manipulated for two palatable grasses (Poa ligularis and Bromus pictus), at three levels of sheep grazing (none, moderate, and high) in a Patagonian steppe community. We found that grazing shifted the effect of Stipa on both palatable grasses, from negative (competition) in the absence of grazing to positive (facilitation) under increasing herbivore pressure. In ungrazed sites, belowground competition was the dominant interaction, as shown by a significant reduction in performance of palatable grasses transplanted near to Stipa tussocks. In grazed sites, biomass of palatable plants was greater near than far from Stipa regardless of competition treatment. Proximity to Stipa reduced the amount of herbivory suffered by palatable grasses, an indirect effect that was stronger under moderate than under intense grazing. Our results demonstrate that facilitation, resulting mainly from protection against herbivory, is the overriding effect produced by unpalatable neighbors on palatable grasses in this rangeland community. This finding challenges the common view that abiotic stress amelioration should be the predominant type of facilitation in arid environments and highlights the role of herbivory in modulating complex neighborhood plant interactions in grazing systems. © 2007 by the Ecological Society of America. |
| title |
Shifts in positive and negative plant interactions along a grazing intensity gradient |
| title_short |
Shifts in positive and negative plant interactions along a grazing intensity gradient |
| title_full |
Shifts in positive and negative plant interactions along a grazing intensity gradient |
| title_fullStr |
Shifts in positive and negative plant interactions along a grazing intensity gradient |
| title_full_unstemmed |
Shifts in positive and negative plant interactions along a grazing intensity gradient |
| title_sort |
shifts in positive and negative plant interactions along a grazing intensity gradient |
| publishDate |
2007 |
| url |
https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00129658_v88_n1_p188_Graff http://hdl.handle.net/20.500.12110/paper_00129658_v88_n1_p188_Graff |
| _version_ |
1768542439730053120 |