Contrasting seasonal abiotic stress and herbivory incidence in <em>Cistus albidus</em> L. plants growing in their natural habitat on a Mediterranean mountain

Abstract

Mediterranean climate mountain areas are characterized by stressful abiotic conditions for plants. Drought, high photosynthetically active photon flux density and extreme temperatures are the main abiotic factors that drive shrub biodiversity in these areas. However, little is known of the extent to which herbivory may additionally influence the physiology of these shrub communities. We studied the incidence of abiotic and biotic stresses in a representative Mediterranean shrub, Cistus albidus L., growing under natural conditions, with an emphasis on the seasonal occurrence of abiotic stress and herbivory, and the possible influence of mountain aspect and plant ageing on the stress response. Reductions in maximum quantum yield of photosystem II (PSII) occurred during early summer and coincided with a combination of drought, high light and high temperatures (above 35 °C in July). East-facing plants experienced greater reductions in PSII quantum yield during July and leaf water content during September than west-facing ones. However, east-facing plants also showed less herbivory-related damage during winter than west-facing plants, particularly from goats. Plant age did not influence herbivory pressure or the stress response to abiotic factors. It is concluded that C. albidus is a highly tolerant shrub to both abiotic and biotic stress factors in Mediterranean mountain areas. It only shows slight photoinhibition during early summer and mild symptoms of herbivory attack in winter.