Assessing different agricultural land uses and ecological disturbances on tropical rainforest regeneration

Background/Question/Methods

Disturbance regimes imposed by different agricultural practices determine the regenerative capacity of old-fields. Therefore, it is a great challenge developing tools to evaluate in an efficient and inexpensive way the level of disturbance generated by different agricultural land uses (ALUs). In this context we (1) developed an ecological disturbance index (EDI) caused by different ALUs, incorporating various elements of disturbance (i.e., extent, duration and intensity); (2) tested the usefulness of EDI to predict the natural regeneration capacity of woody vegetation in recently abandoned fields; and (3) explored the relative importance of different elements of disturbance on regeneration. Using semi-structured interviews we characterized the elements of disturbance on the ALUs practiced in the Marques de Comillas region, Chiapas, México (e.g., cacao, oil-palm and corn plantations, and livestock pastures). Therefore, these disturbance elements were integrated in the EDI. In contrasting ALUs we quantified the standing biomass, density and richness of woody seedlings at the time of abandonment and after two years, and characterized environmental conditions and soil properties (i.e. site quality).

Results/Conclusions

The greater disturbance was found in pastures and oil-palm crops, followed by the monocultures with intermediate disturbance levels; and the ALUs with the lowest disturbance included coffee, cocoa, mahogany and fruit orchards. Overall, the ecological disturbance caused by different ALUs modified site quality and reduced the seedling bank affecting short-term regeneration. The EDI can be useful to predict the response of woody seedlings to disturbance in the short term, but not for standing biomass. Finally, disturbance intensity was the variable explaining the greater proportion of variation in density and richness of woody plants. The methodology developed in this study is useful to identify those agricultural lands that have less impact on the environment and that are compatible with the conservation of biodiversity and the persistence of the rainforest in the long-term.