The impact of soil structure on euedaphic Collembola

Summary

Tillage operations and field traffic can lead to soil compaction and alter the pore structure in soil. These practices often lead to a reduction in habitable pore space for euedaphic Collembola. In the present study the reproduction of some euedaphic Collembola species was investigated under a range of soil bulk densities normally found in agricultural soils.
The study was performed using microcosms with defaunated and remolded raw soil that was compressed to bulk densities between 1.02 – 1.56 g cm-3. One of the following species was added to each series: Mesaphorura macrochaeta, Protaphorura armata, and Folsomia fimetaria. The number of individuals and ergosterol concentrations (used to estimate fungal biomass) were measured after each experiment and related to bulk density and pore size distribution. A series of experiments in which straw was added to the soil in order to increase microbial life was also included. Only F. fimetaria was used in the straw amended series.
In the raw soil experiments with M. macrochaeta and P. armata the number of individuals was significantly lowered when bulk densities increased from 1.37 to 1.47 g cm-3. F. fimetaria did not exhibit any response to compaction. The ergosterol concentrations were constant in all bulk densities. When straw was added, the reproduction of F. fimetaria declined significantly with increasing bulk density from 1.21 g cm-3. The decline in collembolan numbers was probably due to the decline in coarse pores (>120 µm) because there was no correlation between bulk density and ergosterol (food) after 26 days. Ergosterol decreased with compaction after 61 days, but the 78% decline in individuals was more likely due to the 87% reduction in coarse pores than the 37% reduction in ergosterol. These results show that soil structure and decline in habitable pore space are key parameters in determining the abundance of euedaphic Collembola in soil.