A field mesocosm method for manipulation of soil mesofauna communities and repeated measurement of their ecological functions over months to years

In situ manipulation of mesofauna communities is necessary to understand their functional importance in complex natural systems. Field mesocosms that control the recolonization of defaunated soil and litter by mesofauna are well suited to this purpose, but are infrequently used and can produce undesirable side effects on microclimate. Here, we present an inexpensive and easy to construct field mesocosm design that is intended to address some limitations of existing mesocosm methods. Our mesocosms were engineered to manipulate mesofauna communities over one or two years via mesh treatments (21 µm, 41 µm, and 1000 µm mesh opening sizes) while minimizing mesh treatment side effects and allowing repeated access to mesocosm interiors for measurement of microclimate differences and mesofauna functions through time. They are also compatible with LI-COR survey chambers, enabling measurement of gas flux from mesocosms. We tested these mesocosms in untreated and thinned/burned ponderosa pine (Pinus ponderosa) forests in Valles Caldera National Preserve, New Mexico, USA to compare their performance in differing abiotic and biotic contexts. The mesocosm treatments successfully manipulated microarthropods > 150 µm for fifteen months but were only partially effective at manipulating microarthropods < 150 µm. This mesocosm technique advances our ability to disentangle the functional contributions of mesofauna in complex natural systems because it enables manipulation experiments with repeated sampling in time and space.