Plant interactions balance under biotic and abiotic stressors: the importance of herbivory in semi-arid ecosystems
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COMMUNITY ECOLOGY – ORIGINAL RESEARCH
Plant interactions balance under biotic and abiotic stressors: the importance of herbivory in semi‑arid ecosystems Marina C. Cock1,2 · José L. Hierro1,2 Received: 27 February 2020 / Accepted: 10 October 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Biotic and abiotic stressors commonly co-occur in plant communities and influence interactions between plants. However, their combined effects on plant interactions have not been widely studied and are still unclear. Here, we assessed the balance of interactions between neighboring plants along a grazing gradient and under two water regimes. We conducted a three-yearfield experiment in semi-arid central Argentina with transplants of the dominant palatable grass Piptochaetium napostaense growing in Baccharis ulicina and open microsites across a gradient of grazing pressure. Additionally, we established a water addition treatment along that gradient. We recorded herbivory, size, and fecundity of P. napostaense. During the first two years, P. napostaense was consumed less and was larger below Baccharis than in the open. These differences were greatest under high grazing pressure. Differences in fecundity between microsites were only detected under high and medium grazing pressure in the first two years. In the third year, Baccharis lost their leaves for unclear reasons and provided poor herbivory protection; hence, P. napostaense plants in Baccharis were larger than those in the open only under medium and low grazing pressure, and there were no differences in fecundity between microsites under any grazing condition. Water additions exerted no effect on plant interactions. The balance of interactions changed from positive under heavy grazing to neutral at low and no grazing and water availability did not alter that balance. We conclude that herbivore pressure is an important driver of the balance of plant interactions in semi-arid environments. Keywords Grazing pressure · Water stress · Stress gradient hypothesis · Central Argentina
Introduction
Communicated by Douglas A. Frank. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00442-020-04789-4) contains supplementary material, which is available to authorized users. * Marina C. Cock [email protected] José L. Hierro [email protected] 1
Laboratorio de Ecología, Biogeografía y Evolución Vegetal (LEByEV), Instituto de Ciencias de la Tierra y Ambientales de La Pampa (INCITAP), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)Universidad Nacional de La Pampa (UNLPam), Mendoza 109, 6300 Santa Rosa, La Pampa, Argentina
Departamento de Biología, Facultad de Ciencias Exactas y Naturales, UNLPam, Uruguay 151, 6300 Santa Rosa, La Pampa, Argentina
2
Plant community structure and composition are largely determined by the balance of the positive and negative interactions that simultaneously occur between neighboring plants (HilleRisLambers et al. 2012). When the net balance of int
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