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Soil seed banks and regeneration of tropical rain forest from milpa fields at the Selva Lacandona, Chiapas, Mexico

Abstract:

The traditional milpa agriculture system (slash-burn) of the Lacandon Maya people in eastern Chiapas, Mexico has created and uses a variety of habitat patches including the whole range of seral stages during forest development. This study examines seed bank attributes in habitats associated with slash-burn agriculture and with the more recent expansion of grasslands. We estimated the abundance and floristic composition of seeds in the soil from induced grasslands, milpa fields neighboring early and mature forests, and from secondary forest and mature tropical rain forest (15 samples by site, 2-3 replicated sites per successional stage). A total of 130 species germinated from the soil samples. The seeds of fate successional tree species were scarce in all the seed soil samples ( < 27 of the species). Twenty-five early successional species accounted for ca. 70 percent of all individuals. Soil seed density (but not species richness) increased as milpas and fallows dominated the landscape. Affinity analysis based on presence/absence and abundance data showed a different soil seed bank composition for the grasslands when compared to that of all other successional communities. Our results suggest that current expansion of pastures and agricultural fields modifies seed deposition and storage patterns in the soil that may alter the process of secondary- succession. This compromises both the regenerating potential of tropical rain forest in the region, and the sustainabtlity of traditional practices and economic relationships of the Lacandon Maya.