Seed rain as a source of propagules for natural regeneration in a temperate forest in Mexico City.

摘要

The regeneration of temperate forests is important, especially for those located in urban areas. Sources of propagules, such as seed rain, shape the structure and composition of systems where the availability of diaspores from forest species contribute to both local biodiversity and ecosystem services; these elements are crucial in Mexico City. Over the course of one year, we estimated natural regeneration potential through an analysis of the seed rain deposited in traps that were placed at soil level in plots in three vegetation types: oak, fir and pine forests. We addressed the following questions: Do abundance, density, species composition and diversity of seed rain differ among vegetation types and seasons? How similar is the seed rain to the standing vegetation? Is seed rain a potential source for the natural regeneration of temperate forests? The results showed that the abundance and density of seeds were significantly higher for oak and fir forests due to a higher number of herb, shrub, and tree species in the standing vegetation. The most abundant species in the total seed rain was Ageratina enixa (B.L. Rob.) R.M. King & H. Rob. (12%), but inside individual forest plots, the most abundant were Quercus rugosa Nee (16%), Abies religiosa (Kunth) Schltdl. & Cham. (17.5%) and Pinus hartwegii Lindl. (41%). Diversity index values differed among vegetation types but not seasons. Most diaspores in the seed rain corresponded to native species (97%). The similarity between seed rain and the standing vegetation was 40%. In total, 62% of the species are anemochorous, as a result of the high number of Asteraceae species present, and endozoochory is the second most important (17%) dispersal syndrome. A slight asynchrony was observed between the peaks of anemochorous and zoochorous species.