Nematode and microbial communities in a rapidly changing compost environment: How nematode assemblages reflect composting phases

The microbial community (fungi and bacteria) is the main decomposer of organic matter during composting. Its composition is sometimes used as a proxy to assess compost maturity. Although nematodes are probably its most important grazers, only one previous study has highlighted clear shifts in nematode species composition during composting, and the assumption that nematodes reflect changes in the microbial community in compost has not yet been formally tested. Here, the microbial and nematode communities of a single composting process are analyzed together for the first time. Although both displayed broadly similar patterns, the abundance of fungal-feeding nematodes showed a distinct delay as compared to the increase in fungal PLFA. We argue that the nematode community may be a more promising tool to use in assessing compost maturity because it allows to discriminate between the three composting phases. First, during the thermophilic phase, bacterial-feeding nematodes dominate; during cooling, the bacterial-feeding/predators bloom; and during maturation, the abundance of fungal-feeding nematodes increases. Based solely on the microbial community, it was only possible to discriminate between the thermophilic phase and the rest of the process. Bacteria dominated during the thermophilic phase, while bacterial and fungal PLFA had more-or-less equal shares during cooling and maturation.

► First study on dynamics of both nematode and microbial dynamics during composting.
► The microbial and nematode community showed broadly similar patterns.
► Shifts in nematode community between all three temperature-related composting phases.
► Major shifts in microbial PLFAs only during thermophilic and early cooling phase.
► Nematode community is a promising tool to assess compost maturity.