Tropical and Subtropical Agroecosystems

In Yucatan Mexico the method of slash and burn is used for the establishment of pastures. Pastures are developed for 15 to 20 years, no more because weed control is too expensive. The impact of these practices on soil macrofauna had not been evaluated. Because of its wide distribution, diverse habits and high sensitivity to disturbance, soil macrofauna is considered a valuable indicator of soil health, allowing monitoring of soil sustainability. We studied soil macrofauna communities in low deciduous tropical forest and four livestock agroecosystems with increasing management-derived disturbance including a silvopastoral system, Taiwan grass (Cynodon nlemfuensis) and Star grass (Pennisetum purpureum) pastures in order to describe community structure across systems, and evaluate disturbance sensitivity of taxonomical groups to detect taxa with potential use as biological indicators of soil health or degradation. Pitfall traps were used at each of the systems to sample soil macrofauna. We estimate their taxonomical abundance, biomass, richness (order, morphospecies), diversity, dominance and response to disturbance on agroecosystems and the forest. We found 133 macrofauna morphospecies of 15 taxa. Groups with more individuals were: Hymenoptera (64.97%), Coleoptera (22.68%), and Orthoptera (3.91%).  Agroecosystem of two-year old Taiwan-grass pasture (TP2) had the highest macrofauna abundances, biomass and richness, low diversity, and a non-homogeneous distribution of individuals among species; in contrast, silvopastoral system (SP), had low abundance and biomass, the lowest specific richness, high diversity and a homogeneous distribution of individuals among species. The discriminant analysis revealed that the agroecosystems and the forest serve to predict the macrofauna communities, since they have particular or typical soil macrofauna. The cases (sampled points) with a correct assignation by agroecosystems were: Forest (70%), Sivopastoral system (70%), Taiwan pasture of two year old (80%), Taiwan pasture of 12 years old (60%) and Star grass of 12 years old (60%). Hymenoptera (the most abundant taxa) and Orthoptera were the macrofauna groups that differ among agroecosystems. Response to disturbance by taxonomical groups showed that Hymenoptera had a temporal pattern, with peak dominance at systems with intermediate disturbance and decrease in dominance at SP; Coleoptera had an opportunistic behavior, becoming dominant as disturbance increased; Orthoptera and Arachnida showed susceptibility to disturbance.

Hymenoptera; Coleoptera; Orthoptera; Arachnida; Leptosol; Karst