COS 130-7
Litter trait impacts microfoodweb in a French agricultural soil
Anthropogenic pressures on agricultural soils are known to decrease their biodiversity. However, the impacts of this loss on soil services and functioning need to be better assessed. We measured the effects of litter trait i.e. quality on soil microfoodweb functioning, modulated by the presence or absence of an ecosystem engineer, Lumbricus terrestris. Our hypothesis was that the composition and functioning of soil microfoodweb change with decomposition following the evolution of litter quality. Aerial and underground parts of maize plants were used as labile and recalcitrant litter, respectively. A dynamic experiment was performed using soil columns filled with a silt loam agricultural soil (Estrées-Mons, Northern France) in which we incorporated in the 0-5 cm layer either maize leaves or maize roots. For both type of litter, we created microcosms with or without L.terrestris. Controls without litter added were also used. We measured regularly soil respiration, litter quality, enzymes activities, microbial diversity and nematodes communities during the incubation.
Results/Conclusions
Litter quality strongly influenced C mineralization rates which were the highest for microcosms incubated with maize leaves. This lead to higher rate of degradation of litter soluble fraction and polysaccharides in presence of maize leaves compared to roots. However enzyme efficiency followed an opposite pattern being higher in presence of roots than leaves thus demonstrating different strategy of microfoodweb. Both microorganisms and nematodes densities were stronger in microcosms incubated with leaves. Time of incubation and initial litter quality explained 73.4% of the trophic structure of nematodes population in PCA. Addition of L.terrestris had no effect on C mineralization rates and this was probably due to the initial incorporation of litter in the 0-5 cm soil. Nevertheless, L.terrestris had a significant effect on the first level of microfoodweb composition and subsequently significantly decreased microbial biomass C and alters microorganisms’ diversity. These results indicate the importance of litter quality before and during its decomposition on soil microfoodweb composition and strategy. The relationships between soil microfoodweb composition and functioning will also be discussed.