Patterns of distribution of nine Quercus species along an environmental gradient in a fragmented landscape in central Mexico
AbstractElucidating the factors determining plant distribution is still on discussion. It has been stated that the distribution is mostly determined by environmental factors, but the evidence on whether this or other processes are the determinants remains inconclusive. In the present study, we hypothesized that oak species differ in their distribution, which might be mostly influence by the environment. Particularly, we explored: i) the patterns of distribution of Quercus species at a landscape scale; ii) the climatic, soil and topographic factors that might determine their distribution, and iii) the degree of association between the species within fragments. The study included the analysis of 78 oak forest fragments at the Cuitzeo lake Basin in Michoacán state, Mexico in which nine oak species were registered. The species showed clear differences in their distribution; three groups of oak species that differ significantly in their spatial arrangement were detected with a NMDS (Non-metric Multidimensional Scaling) analysis. We observed a relationship between oak species distribution with temperature and precipitation. In particular, Q. candicans, Q. crassipes and Q. rugosa were frequently distributed at sites with higher rainfall and lower temperature; in contrast, Q. deserticola, Q. gentryi and Q. glaucoides were at more arid areas. We found associations between pairs of oak species; the most recurrent one was between species from the Quercus and the Lobatae sections. Overall, the pattern of distribution among oak species was determined by environmental factors, which suggests that they partition their habitat to avoid competition for resources.
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