Modification of the bait-lamina test to estimate soil macrofauna and mesofauna feeding activity

Abstract

The bait-lamina test (BLT) is a widely used method for assessing the feeding activity of soil detritivores. However, one of its limitations is the ambiguity in the interpretation of results, as it is difficult to determine which taxa or size groups consumed the bait. To address this issue, we propose a modification of the BLT called the differential BLT, which allows for the estimation of the contribution of macrofauna to the total feeding activity of soil detritivores. In the differential BLT, the size of the holes is reduced to prevent bait ingestion by macrofauna. The values obtained from the large holes represent the bait consumption by all groups, while the difference between values obtained from large and small holes is attributed to macrofauna alone. Through a laboratory experiment with defaunated soil subsequently inoculated with earthworms and using the strips with various hole sizes, we identified the threshold aperture size of 0.2–0.3 mm that excludes earthworms from the bait. In an experiment with laboratory-cultured enchytraeids, we demonstrate that these aperture sizes do not prevent bait consumption by mesofauna. We also conducted a field experiment in the southern taiga coniferous forests, where we verified the applicability of the differential BLT in situ and estimated that macrofauna contributes two-thirds to the total feeding activity. The partitioning of the total feeding activity of soil detritivores using the differential BLT can be a valuable tool for soil ecologists to assess the functioning of below-ground animal communities.