Impacts of Disturbance on Detritus Food Webs in Agro-Ecosystems of Contrasting Tillage and Weed Management Practices

This chapter illustrates detritus-based food webs responding to various disturbance regimes occurring in conventionally tilled (CT) and non-tilled (NT) systems. The detritus food web is based largely in the soil system, and is important in regulating nutrient cycling and energy flow, it is reasonable to expect that this food web may be a viable and meaningful indicator of disturbance exerted by tillage and alternative weed management strategies. The principal differences in disturbance regimes involve cultivation, herbicide application, residue management and manipulation of weed levels, therefore, emphasis is placed on these factors. The chapter also reviews the results of previous studies, determines how different components of the detritus food web respond to the disturbances relative to each other, and examines the consequences of these disturbances for overall food web structure. Furthermore, while disturbances in CT systems may exert predictable negative effects on most groups of soil organisms, the responses of species assemblages are less predictable. Individual taxonomic species are undoubtedly a more sensitive indicator of ecosystem disturbance than are entire functional groups, and is therefore a more appropriate unit for biomonitoring purposes.