Plant interactions balance under biotic and abiotic stressors: the importance of herbivory in semi-arid ecosystems

HIERRO, JOSÉ L.; COCK, MARINA C.

OECOLOGIA

SPRINGER

Año: 2020 vol. 194 p. 685 - 694

0029-8549

Biotic and abiotic stressors commonly co-occur in plant communities and infuence interactions between plants. However, their combined eiects 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-year-field 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 diierences were greatest under high grazing pressure. Diierences 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 diierences inffecundity 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 tha fherbivore pressure is an important driver of the balance of plant interactions in semi-arid environments.