Ligustrum lucidum invasion decreases abundance and relative contribution of soil fauna to litter decomposition but increases decomposition rate in a subtropical montane forest of northwestern Argentina

Abstract

Invasive plant species can alter litter decomposition rates through changes in litter quality, environment conditions and decomposer organisms (microflora and soil fauna) but limited research has examined the direct impact on soil fauna. We assessed the abundance and relative contribution of soil meso- and macrofauna to litter decomposition in invaded forest by Ligustrum lucidum and non-invaded forest in a subtropical mountain forest of northwest Argentina using litterbags (0.01, 2 and 6 mm mesh size). Additionally, we analyzed litter quality and soil properties of both forest types. Soil fauna abundance was lower in invaded than in non- invaded forest. The contribution of soil macrofauna to litter decomposition was important in both forest types, but soil mesofauna contribution was only significant in non-invaded forest. Litter decomposition was significantly faster in invaded than in non-invaded forest, consistent with its highest quality. Invaded forest had significantly lower litter accumulation, lower soil moisture and greater soil pH than non-invaded forest. Our results showed that, although soil fauna was less abundant and played a less pronounced role in litter decomposition in invaded forest; these changes did not translate into a reduced litter decomposition rate due to the higher quality of litter produced in the invaded forest.