Temporal Shifts in Plant Diversity Effects on Carbon and Nitrogen Dynamics During Litter Decomposition in a Mediterranean Shrubland Exposed to Reduced Precipitation

Mathieu Santonja (1, 2) , Alexandru Milcu (3, 4) , Nathalie Fromin (3) , Anaïs Rancon (2) , Ammar Shihan (3) , Catherine Fernandez (2) , Virginie Baldy (2) , Stephan Hättenschwiler (3)

1 ECOBIO - Ecosystèmes, biodiversité, évolution [Rennes]
2 IMBE - Institut méditerranéen de biodiversité et d'écologie marine et continentale
3 CEFE - Centre d’Ecologie Fonctionnelle et Evolutive
4 Écotron Européen de Montpellier

Climate and plant diversity are major determinants of carbon (C) and nitrogen (N) dynamics in decomposing plant litter. However, the direction and extent to which thesedynamics are affected by combined changes in climate and biodiversity is not well understood.We used a field experiment in a Mediterranean shrubland ranging from one to four shrub species with partial rain exclusion (-12%) to test how lower precipitation interacts with shrub species diversity to influence C and N release during decomposition. We also distinguished between first-year (0-12 months) and second-year decomposition (12-24 months) to test the hypothesis of stronger diversity effects at the beginning of the decomposition process. Litter C and N release increased with litter species richness during the first year, but not during the second year of decomposition. However, these richness effects were weak and less consistent than litter composition effects, which persisted over time and became even stronger for C release after two years of decomposition. Partial rain exclusion reduced N release by 17% only during the first year and had no effect on C release in either year. Community weighted mean (CWM) traits and functional dissimilarity (FD) of litter traits contributed both to explain litter species composition effects. These litter trait effects were not altered by partial rain exclusion, but were more important after two years than after one year of decomposition. Our findings suggest increasing trait legacy effects with ongoing decomposition. More generally, our data showed that changes in the diversity of dominant shrub species had stronger effects on C and N release during litter decomposition than a moderate reduction in precipitation.

Mots clés: Community weighted means; Rainfall exclusion; Biodiversity-ecosystem functioning; Garrigue; Functional trait dissimilarity; Decomposition stage; Litter functional traits

Domaines: Sciences de l'environnement; Biodiversité et Ecologie

Mathieu Santonja, Alexandru Milcu, Nathalie Fromin, Anaïs Rancon, Ammar Shihan, et al.. Temporal Shifts in Plant Diversity Effects on Carbon and Nitrogen Dynamics During Litter Decomposition in a Mediterranean Shrubland Exposed to Reduced Precipitation. Ecosystems, 2019, 22 (5), pp.939-954. ⟨10.1007/s10021-018-0315-4⟩. ⟨hal-01928001⟩