Conversion of cerrado into riparian forest impacting soil attributes

Abstract

Construction of Hydroelectric Power Plants (HPP) promotes the disappearance of several ecosystems. including the riparian forests, vvhich follow the watercourses and carry out functions such as the maintenance of biodiversity and the soil protection. The Riparian Forest Project was implanted in Itutinga/Camargos reservoirs (Southern Brazil) to recover both form and function of these forests. Nevertheless, aspects related to soil sustainability in the forested áreas had not been assessed so far. Soil organic matter (SOM) is a key factor for studying sustainability, since it is related to the main soil processes. We hypothesised that elucidation of changes in SOM and their relationship with alterations in physical, chemical and biological soil attributes could be userul for assessing soil sustainability. Our objectives were (i) to verify the impact of the forest plantation on soil sustainability. by comparing litter and soil (Acric Red-Yellow Latosol) samples of an área maintained under native vegetation (Brazilian savannah or "cerrado"'), and other one planted with riparian species in 1992: and (ii) to contribute to the knowledge on SOM in Brazilian conditions. In order to reach these goals. we studied the impacts ofthe vegetation conversion on SOM dynamics (by density fractionation and ô,JC) and chemical composition (by l5C nuclear magnctic resonance and pyrolysis). and evaluated changes in soil attributes after conversion. We found that the organic material is quite different between the áreas. In the cerrado, grasses (C4- derived C) predominate. carbon input is mainly below ground (root system), SOM is easily degradable, and C stocks are higher. In the forest, C3 vegetation is the major source of C and its input is mainly above ground. moreover SOM is more recalcitrant. Although these existing differcnces in SOM between cerrado and forest. and the relationships between SOM characteristics and several soil attributes for both áreas, there were no consistent changes in soil conditions that could be caused by the vegetation conversion by itself. Considering the results of this research as a whole. the establishment of the riparian forest nas not effectively improved soil sustainability. The soil under both áreas is able to sustain the vegetation growth. with no damages to the environment. In terms of environmental sustainability. the forestation might bring about the recomposition of the lakeshores in a long-term. contributing to the recovery of the riparian forest functions.