Estratégias de facilitação da sucessão ecológica no póscontrole de gramíneas invasoras

Abstract

Biological invasion refers to the process of entry, establishment and dissemination of an alien species in an environment where it did not previously occur. Currently, biological invasion is a challenge also faced by Conservation Units (UCs). The Quarta Colônia State Park (PEQC) is classified as an Integral protection UC, located in the central region of the state of Rio Grande do Sul. In its limits are present large portions of degraded areas with the presence of invasive exotic species, causing negative impacts to the processes of natural succession. Faced with this scenario, the PEQC management carried out a previous control of invasive exotic plants using combined mechanical and chemical methods. After that, a high percentage of regeneration of invasive exotic grasses was observed, even after the implementation of control practices for these species. Given the above, this work aims to test and validate strategies that favor ecological succession in post-control areas of invasive exotic grasses in the PEQC, in order to provide subsidies to initiate ecological restoration in the UC. The experiment followed the experimental design of randomized blocks and four treatments were tested, referring to different types of biomass: Woody residues (T1), Rice husks (T2), Cover species (T3) and Control (T4). Methodologies were applied for the evaluation of soil cover, quantification of biomass and survey of natural regeneration in two experiments: 1) Postcontrol area of Pennisetum purpureum Schumach; 2) Urochloa sp. Data on land cover, biomass, abundance and richness of natural regeneration of the shrub-tree stratum were submitted to ANOVA and the means of treatments were compared by Tukey's test (p<0.05). Phytosociological indices were also calculated for the shrub-tree stratum. All statistical analyzes were processed in R. The most effective treatment for the two invasive exotic grass species studied was the T1 “Woody residues”. This biomass refers to a material commonly produced during the execution of management and control plans in large areas on a large scale, a reality found in the PEQC. The natural regeneration of native species is occurring satisfactorily, taking into account the historical degradation of the site. Most regenerating species are dispersed by animals, so we suggest that after the implementation of biomass, active restoration techniques be installed, such as planting in cores and artificial perches in order to enhance the ecological succession of the post-control areas.