Short‐term dynamics and long‐term recolonization of protozoa in soil

Abstract

Most studies of Protozoa in the soil are based on the “most probable number” (MPN) estimates from cultured sub‐samples. This approach has been criticized in recent years by protistologists. In order to work around these criticisms, we have tried to develop a set of procedures that rely on direct counts, without culturing. We show that the method is more sensitive and requires less effort than the MPN approach. Our species extractions focus on “active species at the time of sampling”, and we tried to estimate the variation between days, as species adjust to soil moisture and temperature changes over several days. These variations are compared to species composition and abundance fluctuations observed between seasons, in decomposing leaf litter bags. We also obtained abundance and community structure data based on samples from a 25‐year agro‐ecosystem chronosequence under no‐tillage management. We found that direct count methods, without prior culturing of samples, were more sensitive in detecting changes over several days, over several months, and in decadal succession from field samples. This provides a great advantage over culture‐based methods that generally fail to distinguish between encysted and re‐activated species.