Habitat Complexity Enhances Comminution and Decomposition Processes in Urban Ecosystems

Decomposition of organic matter is an essential process regulating fluxes of energy and matter within ecosystems. Although soil microbes drive decomposition, this is often facilitated by detritivores through comminution. The contribution of detritivores and microbes to comminution and decomposition processes is likely to be affected by the habitat complexity. In urban ecosystems, human activities and management of vegetation and litter and soil components determine habitat complexities unobserved in natural ecosystems. Therefore, we investigated the effect of habitat complexity of low- and high-complexity urban parks and high-complexity woodland remnants on microbial decomposition and detritivore comminution using litter bags of differing mesh size. Detritivores were sampled using pitfall traps and their assemblage structure related to rates of comminution. Habitats of lower complexity had significantly lower decomposition and comminution rates. In more complex habitats, site history did not affect decomposition and comminution processes. Vegetation complexity and the indirect effect on microclimate explained most of the variation in decomposition and comminution processes. The abundance of macrofauna detritivores and their species richness were both positively related to higher comminution rates. The volume of understory vegetation was the best predictor for both macrofauna detritivore assemblage structure and comminution and decomposition processes. The study demonstrated that relatively modest changes in habitat complexity associated with different management practices can exert significant effects on the decomposition and comminution processes. The structure of detritivores assemblages was also subjected to modifications of the habitat complexity with significant effects on comminution processes. Simple management practices aimed to increase the complexity of habitats, particularly in the understory vegetation and litter layers, could restore and enhance soil biodiversity and functioning in urban ecosystems.