Efeitos da silvicultura com eucaliptos sobre a estrutura de Comunidades Campestres no sul do Rio Grande do Sul, Brasil

Abstract

Grasslands comprises areas with high biological diversity, provide habitat for breeding and migrating birds, maintain a diverse edaphic fauna, serve as pastures for wild herbivores, and participate in water and nutrient cycling. Among the main threats to the fields is the introduction of Eucalyptus sp., which can cause competition and even the loss of native species. The present study aimed to investigate the influence of eucalyptus monoculture on grassland plant community structure. The study was conducted at the western of Rio Grande do Sul state, Brazil. Two areas were considered as follows: areas planted with eucalyptus (defined as Eucalyptus) and their Permanent Protected Areas - PPA (Eucalyptus' PPA) and grasslands areas without eucalyptus plantation (Control) and their respective PPA (Control PPA), but used for the livestock. In those areas parallel linear transects were established, considering the distance from the edge toward the Eucalyptus' PPA and considering the water body distance for the Control areas. The influence of the management, treatment and transect on abundance, composition, richness, diversity, height and exposed soil were analyzed. The influence of the edge was found only in Eucalyptus areas. 135 plant species were identified, distributed in 30 families. Among the results of the analysis of variance (ANOVA Split Plot), management (with and without eucalyptus) and treatments (Eucalyptus, Eucalyptus' APP, Control APP and Control) were highlighted as important factors in patterns of richness, diversity, abundance, height and soil (p <0,05). The NMDS for abundance (p <0,0001, r = 0,32) ordered the first axis in as a function of management and subsequently on the basis of treatments and transects. Eucalyptus and Eucalyptus APP's formed well defined groups meanwhile Control areas and their respective PPAs were ordered all together. The PPAs always showed the highest values of richness and diversity when compared with its adjacent areas. It was concluded that the types of management and treatment can significantly influence the richness, diversity, abundance, height of grassland vegetation and exposed soil. The importance of maintaining the grassland PPAs next to the eucalyptus monocultures for the conservation of plant diversity is stressed.