Challenges related to soil biodiversity research in agroecosystems - Issues within the context of scale of observation

Soil biodiversity, the study of the variety of life in the soil, has received increasing attention as an outcome of recent national and international initiatives, such as the Convention on Biological Diversity, and various programs related to sustainable development of agroecosystems. The broad objectives of this paper are to set the stage for a "state of the art" review of soil biodiversity research in Canadian agricultural systems, to highlight the relevance of soil biodiversity studies at various scales of observation, to acknowledge the importance of soil biodiversity to the soil system with respect to soil functions, and processes and to suggest research challenges and opportunities. Study scale is of critical importance as it determines both the kind of soil biodiversity information and the feasible level of detail (spatially and temporally). At all scales from global to national to regional to landscape to ecosystems ranging to even fine scales of habitat niches at soil particle level, soil biota respond to the physical, chemical and biological constraints of their environment as mediated by environmental and anthropogenic influences. For example, at the landscape level, there exists a mosaic of ecosystems that can be characterized as a continuum ranging from unmanaged (natural), uncontrolled systems regulated primarily by environmental influences to managed, controlled systems regulated primarily by anthropogenic influences. In agroecosystems, soil biota contribute to the decomposition of crop residues and nutrient cycling, soil aggregation and water infiltration, suppression of soil-borne diseases and pests, and detoxification of chemicals. The intensity and duration of environmental and anthropogenic influences on these soil biota will affect their spatial and temporal distribution within this continuum of ecosystems occurring in the landscape and thereby also affect the extent of their capability for contributing towards soil functions and processes. Within this spatial and temporal context, research challenges are discussed.