Soil microbial activity and functional diversity in declining cork oak forests (Doñana National Park, SW Spain)

Comunicación presenteada al citado congreso, celebrado del 2-4 de octubre 2013, en Madrid, España.

Oak decline is a widespread phenomenon around the Mediterranean area, however soil factors promoting such decline are still poorly understood. In the cork oak forest at Doñana National Park (SW Spain), decline is related with the presence of large colonies of wading birds, which supply the soil with high amounts of detritus, altering main biogeochemical cycles (1). We analysed the activity and composition of soil microbial communities along bird influence gradient in these declining forests. Key variables induced soil enzyme activities (dehydrogenase, urease, aryl-sulphatase, beta-glucosidase and acid phosphatase), physiological profiles at community level (CLPP analysed by the MicroResp method) and structural diversity of archae, eubacteria, actinobacteria and fungi (analysed by TRFLPs). Bird influence resulted in remarkable changes in the physico-chemical properties of the soil, such as pH decrease, salinity increase, and increases in the bioavailability of phosphorus, nitrate and ammonium. These caanges onfluenced the activity of the soilborne microbial communities: basal respiration, acid phosphatase, urease and beta-glucosidase activities increased under the bird influence, as well as the amount of C and P in the microbial biomass. CLPP analysis did not reveal any change in preferences for the tested substrates (low molecular weight C-compounds) under bird influence. Despite functional diversity remained similar along the bird influence gradient, preliminary results suggested important changes in the structural diversity of microbial communities (analysed by TRFLP), with an increase in the abundance of archae in soils exposed to the highest levels of bird influence. In conclusion, the presence of large colonies of wading birds at Doñana National Park clearly influences soilborne microbial communities, and by extension, biogeochemical cyckes in this declining ecosystem.

Peer reviewed