Dynamic of nematode communities in energy plant cropping systems
The perennial cropping system of the cup plant (Silphium perfoliatum) might counteract major drawbacks of intensively managed annual biomass production systems due to a long-term reduction of agricultural management. In this context, the ecological value of the cup plant was assessed for free-living soil nematodes to reveal changes in soil biodiversity and functions associated with cultivation period length. For this purpose, cup plant fields from a chronosequence were sampled in two consecutive years and compared to energy maize production systems. Nematodes were identified on a family level and assigned to feeding guilds. General and nematode-specific diversity indices, as well as multivariate redundancy analysis were used to assess changes in community structure. General mixed-effects modeling and multi model averaging were applied to reveal the influence of cultivation period length and environmental factors on nematode assemblages. Major changes were found in almost all trophic groups. In the long-term, abundances of herbivores, fungivores and carnivores increased along with total nematode abundance. Bacterivores remained almost unchanged, but decreased in dominance. Old cup plant fields (8+ years) showed mass occurrences of Helicotylenchus spp.. In cup plant fields, facilitation of fungal decomposer channels and top-down regulation within the nematode food web could improve soil fertility and soil quality. However, long-term dynamic of the nematode community was not indicative of succession and remained characteristic for agroecosystems, hence positive effects are presumably restricted to conversion of farmed land.