Abstract

AbstractThe stress‐gradient hypothesis (SGH) predicts that, although facilitation and competition occur together, facilitative interactions will be more prevalent with increasing abiotic stress. In water‐limited ecosystems, support for the SGH has been controversial. Because of the relevance of ecotones to local and regional diversity and the susceptibility to disturbance of the species inhabiting them, these systems represent interesting opportunities to test the SGH. Our aim was to determine whether the spatial pattern of species distribution along an arid ecotone is consistent with the SGH. Vegetation surveys were performed along topographical gradients found between several palaeochannels and bars where two communities dominated by Chuquiraga avellanedae and Larrea divaricata coexist. Daily precipitation and soil water potential at three depths were measured at a palaeochannel and a bar. Univariate and bivariate distribution patterns were investigated by second‐order spatial analysis based on Ripley's K function in order to evaluate the possible existence of positive or negative interactions among plants. Soil water potential was higher at palaeochannels, indicating that a gradient of water stress exists between the palaeochannels and the bars. Whereas palaeochannels showed regularity among C. avellanedae individuals, bars showed aggregation among L. divaricata individuals and among both species. These results suggest a change in dominant interactions along the gradient from facilitative at the more xeric bars to more competitive at the relatively wetter palaeochannels in accordance with the stress‐gradient hypothesis.

Full Text
Paper version not known

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.