Charcoal consumption and casting activity by Pontoscolex corethrurus (Glossoscolecidae)

Abstract

The endogeic earthworm Pontoscolex corethrurus (Glossoscolecidae) is a peregrine species commonly found in tropical lands cleared by man for cultivation. We compared the charcoal consumption and casting activity of a population of P. corethrurus from a cultivated area under repeated slash-and-burn (fallow population) with that of a population living in a field cultivated after recent burning of a mature forest (forest population). Their cast production was measured in containers in the presence of pure charcoal, soil of fallow and forest origin, or a mixture of charcoal and soil. The forest population defecated less in pure charcoal than in forest soil, whereas the reverse was observed in the fallow population. When living in fallow soil, both populations defecated more at the surface of a mixture of charcoal and soil than at the surface of pure soil (x 2 and x 3 with fallow and forest population, respectively). In forest soil, both populations showed an increased charcoal consumption (x 12). In the light of these experiments, we hypothesized that an adaptation of P. corethrurus to charcoal and fallow soil exists, supporting the observed distribution of this earthworm species in tropical open lands.

Impact of Biochar on Earthworm Populations: A Review

“…In tropical regions, populations of the peregrine earthworm species, P. corethrurus, are capable of translocating charcoal residues from slash-and-burn land clearings deeper into the soil profile [70]. This activity by P. corethrurus indicates its potentially vital role in stabilizing organic matter and historical development of Terra preta soils [46,71]. Because of their vital role, some researchers have proposed that earthworms, particularly in the tropics, can be used as ecosystem engineering tools to maintain and/or improve soil fertility and ecosystem function [72] particularly in conjunction with charcoal additions [73].…”

“…Even though the chars used in these studies [46,47] are both considered slash-and-burn residue, the materials are quite different as indicated by the high C content of the wood-derived char-soil mixture (39% C) versus the low C of the rice-derived char-soil mixture (11% C). Therefore, one could expect different responses due to the inherent differences in black carbon chemistries.…”

“…for the fishing industry (bait) is known to take place primarily in recently (within days) control-burned forest areas in the Appalachicola National Forest, Florida, USA [64]. Topoliantz and Ponge [45,46] have already shown that P. corethrurus was unaffected by biochar in short-term studies, but field application rates were difficult to discern. As with Husk and Major [75] a low application rate of biochar, particularly one derived from wood, might not have had a substantial effect in the field.…”

“…One noted impact of the charcoal application was the increase in soil pH from moderately acidic to nearly neutral pH values ( Table 1). The neutralizing of soil pH was provided as a reason why earthworms were not deterred from burrowing into the charcoal-soil mixtures [46]. The prospect of using char from slash-and-burn management practices in rice crops in China for reducing environmental contaminants was evaluated [47].…”

“…Charcoal additions along with slash-and-burn practices paved the way for the formation of carbon-dense fertile black soils [44] (see Section 3.4). Under this premise, Topoliantz and Ponge [45,46] undertook the evaluation of an earthworm's reaction to charcoal obtained from a slash-and-burn field in laboratory analyses. In these two studies, a geophagous tropical peregrine earthworm, Pontoscolex corethrurus, was presented with pure soil (Oxisol), pure charcoal, or 60% sieved (<2 mm) wood-derived charcoal-soil mixtures, and growth rates, ingestion, burrowing, and casting activity were evaluated.…”