Bracken fern (Pteridium aquilinum) is one of the most successful plant colonizers of soils in temperate regions; however, its effects on microbial community structure and activity and nutrient dynamics remain poorly understood. We studied whether colonization of forest soil by bracken fern modifies the structure and function of the soil microbial communities and considered the implications for ecosystem functioning. For this purpose, we analyzed microbial community structure (PLFAs) and activity (basal respiration, metabolic quotient), litter decomposition and nutrient dynamics (C, N and P) in monospecific oak (Quercus robur L.), eucalyptus (Eucalyptus globulus Labill.) and maritime pine forests (Pinus pinaster Aiton) colonized by bracken fern. Colonization of forest soil by bracken fern led to a reduction in differences in microbial community structure, as revealed by principal component and cluster analysis, although samples from oak forests were grouped separately. According to this, bracken litter decomposed to a greater extent than native tree litter in pine forest soils, whereas the opposite was found in oak forest soils. Such differences were not observed in eucalyptus forest soils. Colonization by bracken fern affected C mineralization, with no difference between the different types of forest; however, both N and P mineralization were higher in oak than in the other types of forest. In conclusion, colonization by bracken fern homogenizes soil microbial community structure. Differences in the decomposability of bracken litter in the different forest systems suggest a high degree of metabolic specialization of soil microorganisms. Thus, the soil microorganisms associated with bracken are continuously driven to decompose the bracken litter. In the long-term this will alter nutrient cycling, slowing decomposition and enhancing sequestering of nutrients by bracken ferns.
Microbial Community Structure and Oxidative Enzyme Activity in Nitrogen-amended North Temperate Forest Soils
