Linkages between traits and decomposition of spontaneous vegetation along a soil management and pedoclimate gradient in Mediterranean vineyards

Background/Question/Methods

Plant decomposition is a key ecosystem process which lies at the core of the biogeochemical cycles. Few studies have analysed the spontaneous vegetation decomposition process in agricultural context while most agrosystems are facing decreasing soil quality, especially vineyards. New management practices of vineyard flora are emerging (e.g. spontaneous cover cropping) gradually replacing chemical weeding. The objective of this study is to understand the impacts of both pedoclimate and these alternative weed managements (tillage and spontaneous cover cropping) compared to chemical weeding on the decomposition of spontaneous vegetation communities through their functional properties. In 16 Mediterranean vineyards representing a pedoclimate and a soil management gradient, we measured the potential decomposition of green aboveground biomass of 50 spontaneous vegetation communities and key structural leaf traits (e.g. Leaf Dry Matter Content, LDMC) and chemical traits (e.g. leaf lignin to nitrogen ratio, Lign:N ; leaf carbon to nitrogen ratio, C:N) of the dominant species, related to the decomposition process. Both the mean (i.e. Community Weighted Means, CWM) and diversity (i.e. RaoQ) of these traits were computed at the community level. Structural equation modelling was used to quantify the effects of agro-environmental filters on the potential decomposition of spontaneous communities through changing their functional properties.

Results/Conclusions

Spontaneous vegetation lost on average 45% of its initial mass after 2 months of decomposition. Tillage and spontaneous cover cropping filtered more decomposable communities (49% and 45% of mass loss) compared to chemically weeded communities (41% of mass loss). Spontaneous cover cropping favoured communities with 47% higher biomass and with 46% higher nitrogen content. Path analysis selected the weed management practice types as the main factor determining mass loss through changing functional properties while soil and climate had minor effects. Chemical weeding favoured communities with higher investment in leaf structure (16% higher C:N, 38% higher Lign:N, 22% lower leaf nitrogen content) which were related to lower mass loss compared to tilled and spontaneous cover cropped communities. Functional diversity did not influence directly mass loss. According to our results, replacing chemical weed control with tillage and spontaneous cover cropping managed by mowing might favour more decomposable communities and potentially improve soil chemical fertility.