Species-Specific Responses of Tree Saplings to Herbivory in Contrasting Light Environments: An Experimental Approach

Light availability and herbivory are 2 major factors affecting the regeneration of woody species, and thus a better perception of how light and herbivory interact to shape the sapling performance of cohabitant tree species emerges as a key issue. The purpose of this work is to experimentally analyze the influence of light conditions on tree responses to browsing. We evaluated the responses to browsing (simulated by mechanical clipping of 50% of current-year shoots) of saplings from 2 deciduous (Acer opalus ssp. granatense and Quercus pyrenaica) and 2 evergreen (Quercus ilex and Pinus nigra ssp. salzmannii) late-successional tree species, measuring an array of morphological, physiological, and biochemical traits. The experiment was performed with saplings grown for 2 y under 3 experimental light environments emulating natural microhabitats: full (open microhabitats), 80% (below pioneer shrub canopy), and 13% (below tree canopy) sunlight. Clipping affected biomass distribution, growth, and sapling size, while only slight physiological and biochemical effects were detected. Species characteristics and the light environment in which saplings grow determine their capacity to recover biomass lost after herbivore damage. Black pine was found to be the least tolerant species to clipping, whereas the broadleaf species displayed greater recovery after clipping. Light scarcity increased the nutritional quality of plants and negatively affected herbivory tolerance of 3 of the 4 species.