Soil Nematode Fauna and Microbial Characteristics in an Early-Successional Forest Ecosystem

Windstorms can often decrease the diversity of native local biota in European forests. The effects of windstorms on the species richness of flora and fauna in coniferous forests of natural reserves are well established, but the effects on biotas in productive deciduous forests have been less well studied. We analyzed the impact of windstorms on the diversity and abundance of soil nematode communities and microbial activity and their relationships with the succession of plant species and basic soil physicochemical properties 12 and 36 months after a windstorm in Fagus sylvatica forests. The relationships were investigated in cleared early-successional forest ecosystems and at undamaged forest sites as a control. The windstorm significantly affected total nematode abundance, number of nematode species, and the diversity and abundance of all nematode functional guilds, but no functional guilds disappeared after the disturbance. The abundance of several nematode taxa but not total nematode abundance was positively correlated with soil-moisture content. Indices of the nematode communities were inconsistent between sites due to their variable ability to identify ecosystem disturbance 12 months after the storm. In contrast, the metabolic activity of various functional groups identified ecosystem disturbance well throughout the study. Positive correlations were identified between the number of plant parasites and soil-moisture content and between carnivore abundance and soil pH. Positive mutual links of some nematode genera (mainly plant parasites) with the distribution of dominant grasses and herbs depended on the habitat. In contrast, microbial activity differed significantly between disturbed and undisturbed sites up to 36 months after the storm, especially soil basal respiration, N mineralization, and microbial biomass. Our results indicated different temporal responses for two groups of soil organisms to the destruction of the tree canopy. Soil nematodes reacted immediately, but changes in the microbial communities were visible much later after the disturbance.