Decreasing fallow duration in tropical slash-and-burn agriculture alters soil macroinvertebrate diversity: A case study in southern French Guiana

In the humid tropics, slash-and-burn cultivation causes changes in the composition of soil biota communities. We investigated the soil macroinvertebrates (body length ≥2≥2 mm) in five sites, two at Maripasoula, an Aluku village along the Maroni river (French Guiana), with short fallow (≈8≈8 years), and the other three at Elahe, a Wayana village along the same river, with long fallow (≈25≈25 years). We report observed species richness, the corresponding estimates by bootstrap and its associated standard deviation. At both sites the cultivation led to impoverished communities. The overall observed species richness i.e. γγ diversity was ca. twice as larger in Elahe than in Maripasoula. The landscape at Maripasoula was dominated by highly disturbed areas with the direct consequence that local species richness relied on colonization from an impoverished regional species pool. On the contrary, in Elahe, crops formed small patches scattered across a landscape essentially constituted of rich undisturbed or slightly disturbed forests hence higher γγ diversity. The proportion of rare species ranged from 44% to 54%. We found 6 indicator species amongst which 5 were associated to the old secondary forest in Elahe and one, the earthworm Pontoscolex corethrurus was associated to crop fields in Maripasoula (short fallow system). Results are discussed in a landscape context in terms of conservation and management of soil macrofaunal diversity in agro-ecosystems.