Earthworm functional traits, landscape degradation and ecosystem services in the Brazilian Amazon deforestation arc

Earthworms, as ecosystem engineers, help to mineralize soil organic matter, construct and maintain soil structure, and often stimulate plant growth and protect plants from pests. The aim of this study was (i) to determine the connection between earthworm traits and indicators of soil ecosystem services and (ii) to identify earthworm “response” traits, which are selected by the landscape or changes in the soil, and “effect” traits, which contribute to soil processes. In the southern portion of the state of Parà (eastern Brazilian Amazonia), we sampled earthworms at 135 points distributed among 3 locations, 9 sub-locations and 27 farms (5 sampling points per farm). At each point, three 25 cm × 25 cm soil samples were hand-sorted for earthworms. We measured eight functional traits in 1148 individuals: relative gizzard size, type of typhlosole, length and type of caudal setae, pigmentation, overall length, thickness of septa and musculature in anterior segments. We found a significant, although relatively low, relationship between landscape classes and trait proportions. Earthworm trait proportions significantly covaried with soil parameters and indicators of soil ecosystem services. We did not find significant covariation between earthworm morphospecies and soil ecosystem services. We identified earthworm “response” traits that had been selected and assessed consequences of these changes on effects of earthworm communities (via their “effect” traits) on soil processes and ecosystem services. Typhlosole type, gizzard size and septa thickness were identified as “response” traits selected by soil and landscape conditions. These traits were also identified as “effect” traits for their influence on soil structure. Results indicated a connection between earthworm traits and landscape degradation and soil services, which is a new step toward conceptualizing earthworm ecological studies that go beyond the species level. (Résumé d'auteur