Long-term effects on soil nematode community structure in spruce forests of removing or not removing fallen trees after a windstorm

Abstract

More than 12000ha of a Norway spruce forest in Tatra National Park, Slovakia, were laid down by a strong windstorm on 19 November 2004. Most of the broken and uprooted trees were completely removed from the area in the following months, but the remaining fallen trees were left in their natural successional state. We analysed the impact of these two strategies of forest management on the structure of the soil-nematode community and its relationships with the structure of the plant community and with basic soil physicochemical properties nine years after the windstorm. The relationships were investigated in a cleared windstorm plot (EXT), a non-extracted windstorm plot (NEX), and an undamaged forest plot (REF) as a control. All plots were sampled twice, in June and October 2013. Results showed that EXT and NEX had a significantly higher mean nematode abundance at both sampling dates than REF (LSD, P=0.05). REF had the mean number of species, similar to the mean number in NEX. Analysis of variance showed significant main interaction among sampling time (P=0.01), plots (P=0.05) and number of species. Spearman’s correlations identified positive correlations between the number of species and soil carbon and nitrogen contents (P⩽0.05) and between the number of fungivores and soil nitrogen content (P⩽0.05). A detrended correspondence analysis indicated that the abundance of plant parasitic nematodes was positively affected by the dominance of the grasses Avenella flexuosa in EXT and Calamagrostis villosa in NEX. Predators and root-fungal feeders were significantly less abundant in EXT and NEX (P=0.05), and omnivores were most abundant in EXT and NEX. Analyses of the nematode communities by ecological and functional indices, except the plant-parasitic and enrichment indices, indicated that nematode abundance and species numbers did not differ between management strategies. The soil environments of all habitats could be characterised as mature, structured, nitrogen-rich, or nutrient-balanced with high or narrow carbon/nitrogen ratios, confirmed by an analysis of metabolic footprints. In summary, the impact of the windstorm on the soil-nematode community was still visible nine years later. The structure of the nematode community, however, had rehabilitated, likely due more to changes in the secondary herbaceous layer associated with the two management strategies than to the soil properties, which were not affected by the windstorm or management in the long term.