Functional leaf-trait variability and herbivory in oaks along a Mexican avocado agrosystem mosaic

Abstract

Land-use changes transforming forested landscapes to avocado orchards affect abiotic conditions and ecological processes. As a consequence, such changes can also affect leaf functional traits expression of co-occurring trees in orchards and related plant–insect interactions. Here, we evaluated changes in chemical soil properties and the effects of micro-climatic variables on leaf functional traits and herbivory in Quercus castanea and Q. obtusata in fragments occurring in a mosaic with avocado orchards. We differentiate three cases: forest cover > orchards, forest cover = orchards and forest cover < orchards in Michoacan state, Mexico. In each case, at least 17 individuals of each oak species were selected to analyze leaf functional traits and herbivory. Soil samples were collected to analyze chemical properties. Soils of areas with higher proportion of forest had higher concentrations of NH4+ and K+, whereas soils with higher proportion of orchards displayed higher concentrations of Mg2+, NO3− and SO42−. Leaf thickness, fresh mass and water content were higher in areas with higher forest cover and were influenced by Mg2+, NO3−, SO42- and local climatic variables. Leaf dry weight, specific leaf area, leaf area and chlorophyll content, as well as herbivory were higher in areas with higher proportions of orchards and were affected by PO43−, total P, K+, NH4+, and by local climatic variables. These results highlight the responses and links of plant functional traits associated with soil properties and local climatic variables and their possible consequences of biotic interactions in a landscape mosaic with different covers of avocado orchards and temperate forests.