Effect of mixing herbaceous litter with tree litters on decomposition and N release in boreal plantations

Abstract

International audienceAbandoned lands are increasingly used to establish fast-growing tree plantations, and are often rapidly colonized by a high density of herbaceous undergrowth. These weeds are generally removed since they compete with trees for resources, in particular soil nutrients. However, mixing herbaceous litter with the litter of planted trees could also stimulate the activity of decomposers and associated nutrient release due to an increase of litter quality (lower C:N ratio), plant diversity (more diverse litter traits) and water holding capacity. The objective was to determine the impact of herbaceous litter on the litter decomposition process of white spruce and hybrid poplar litters alone or in mixtures. Litter mass loss rate, nutrient release and decomposer communities were monitored on single and mixed-species litters using litterbags during two years in three plantations types (hybrid poplar, white spruce and mixed plantations). Litters within mixtures were separated by species to identify species-specific responses of leaf mass loss. N release of all litter types increased with the presence of herbaceous litter. This finding could be linked to the greater abundance of decomposers and fungal biomass brought about by the herbaceous litter. Addition of herbaceous litter had no effect on spruce litter mass loss but had positive effects on poplar and mixed spruce/poplar litter mass loss. Abundance of fungi and mites was more affected by litter quality, whereas the abundance of collembola was more affected by the diversity of resources than by litter quality. In these 10-year plantations with poplar, increased litter mass loss for poplar and mixed litters and N release associated to the presence of herbaceous litter showed that weeds may change soil C sequestration and N cycling

Plant secondary metabolites: a key driver of litter decomposition and soil nutrient cycling

“…; Chomel et al . ). One mechanism by which these litter mixing effects occur is through disproportionate effects of individual species, whose influence on decomposition outweighs those of surrounding species (Diaz et al .…”

“…Rather than aggregated traits values, the dissimilarity of litter traits within plant communities can also be used to explain how the plant community composition influences the decomposition of mixed litter (Epps et al 2007;Barantal et al 2011). However, these approaches do not account for the widely observed synergistic or antagonistic interactions between the decomposing litter of different plant species through litter mixing effects (Gartner & Cardon 2004;Santonja et al 2015;Chomel et al 2016). One mechanism by which these litter mixing effects occur is through disproportionate effects of individual species, whose influence on decomposition outweighs those of surrounding species (Diaz et al 2007;Qu etier, Thebault & Lavorel 2007;Barantal et al 2011).…”

Diversity-decomposition relationships in forests worldwide

“…Forests mediate biosphere-atmosphere carbon (C) dynamics via primary productivity ( Huang et al, 2018 ; Liang et al, 2016 ) and decomposition ( Handa et al, 2014 ; Hooper et al, 2012 ). The biodiversity of organisms involved in C and nutrient cycling can modify these ecosystem processes, for example, during the decomposition of plant litter that typically occurs in mixtures ( Chomel et al, 2016 ; Hättenschwiler et al, 2005 ). Litter mixtures can decompose at different rates than would be predicted from the rates of the individual component species, resulting in non-additive effects with either faster (synergistic effects) or slower (antagonistic effects) decomposition ( Gartner and Cardon, 2004 ; Wardle et al, 1997 ).…”

Tree species identity alters decomposition of understory litter and associated microbial communities: a case study

“…A sufficient amount of N was also reflected in a significantly higher N content in Calamagrostis litter that was apparent from the seventh month of the experiment at this site. Several authors (e.g., Voříšková et al 2011;Šnajdr et al 2013;Chomel et al 2016) claimed that N increases fungal biomass in litter. This was not observed in the present study.…”