Gas exchange in two high andean plant species of central Chile: effect of the association with cushion plants

Abstract

It has been proposed that on stressful environments as high mountain habitats, interactions between species of plants would tend to be of the positive type, increasing in intensity and frequency when resources in the environment become more limited. In this work, we studied the microclimatic modifications produced by cushions of Laretia acaulis species and its effects on the physiological performance of two associated species of the high mountain community located at 2800 m.a.s.l. in Los Andes of central Chile: Taraxacum officinale and Euphorbia collina, which frequently grow within and outside the cushions respectively. Gas exchange measures were taken in order to assess the effects caused by the microclimatic modifications done by cushions plants. We demonstrated that individuals of T. officinale that grow within cushions displayed, unlike their co-specifics in open spaces, a greater net photosynthesis rate. E. collina did not show differences in the rate of net photosynthesis between individuals present within and outside cushions. Only T. officinale displayed a greater rate of photosynthesis in the microsite where it is frequently distributed (within cushions). The effect of association with a nurse (e.g. cushion plants) for large biomass species, such as E. collina, could be less beneficial due to the competition for resources and space; this would explain why E. collina is more frequently found in open spaces.