Too many mites, too little time: Expeditious methods for manipulating and characterizing soil microarthropod communities

Soil ecologists studying microarthropods are blessed (or plagued, depending on your perspective) with samples each containing hundreds to thousands of individuals belonging to tens to hundreds of morphotypes, of which most are typically mites. Unfortunately, time and research budgets are very rarely commensurate with the quantity and diversity of specimens collected. In this talk, we will review some strategies and tools that can help researchers to leverage limited resources when characterizing complex soil microarthropod communities. We will also present a low-cost, low-tech field mesocosm method for medium-term (1 to a few years) manipulation of soil and litter microarthropod assemblages by size. Units are constructed from 20 cm diameter PVC sewer pipe with large windows cut in the sides, wrapped in mesh of various sizes and capped with removable 40 µm mesh lids. These mesocosms were designed to reduce microclimate differences while also permitting repeated internal sampling of soil and litter, retrieval of standard substrates in decomposition studies, and gas flux analysis using LI-COR survey chambers. We tested this mesocosm method at two forest sites and found that mesh and defaunation worked effectively to manipulate the soil microarthropod community. Challenges and considerations of field mesocosms will be discussed, including microclimate differences and their measurement, defaunation methods and their side effects, and quantification of ecological functions performed by microarthropods. Together, this group of tools can enhance our ability to understand the functional roles of mites in ecosystems.