Abstract ID: 624

Changes and Recovery of Biogeochemical Processes in Disturbed Ecosystems at Local Scale in Central Amazon

The study aimed to identify changes in the functioning of forest biogeochemical processes triggered by the deforestation and replacement by cattle pastures, as well as the recovery by the second growth after pasture abandonment. Soil and hydrological processes were investigated in both catchments, one in intact forest and other in impacted area. Chemical and biological parameters of the stream running from pasture into the second growth and mature forest recovered surprisingly well, likely because: (i) it runs for only a short while in the pasture, soon entering into the forested area; (ii) at the edges of the stream, a strip of the original forest was preserved, protecting the water body from direct impacts of the former pasture which covered most of the area and lasted for ca. 10 years. Litter decomposition rates within the stream waters showed no significant differences among points located near or far from the pasture area; only the density of the collector-gatherer invertebrates changed significantly from the beginning of the water body towards a 300-m downstream point. Leaf litter falling into the stream appears to be important hiding places for the invertebrate animals in the stream, and thus a key resource for the functioning of the system. In the existing mosaic of second growth in the surroundings (aged between 10 and 24 years), those originated from slash-and-burn agriculture or pastures produced less litterfall and stored more litter on soil surface than those growing in no-burnt areas. Among the second growth originated in slash-and-burn abandoned pastures, the older ones produced more litterfall and stored relatively lower amounts of litter on soil surface. On the other hand, areas suffering more burnings in the pasture phase showed greater accumulation in the litter layer. Low-quality of litterfall and reduced density and diversity of litter decomposers are likely among the causes of greater litter-layer

Session:  Biogeochemistry - Nutrient cycling in forest and savanna ecosystems and agroecosystems.

Presentation Type:  Oral