Global negative vegetation feedback to climate warming responses of leaf litter decomposition rates in cold biomes

Whether climate change will turn cold biomes from large long-term carbon sinks into sources is hotly debated because of the great potential for ecosystem-mediated feedbacks to global climate. Critical are the direction, magnitude and generality of climate responses of plant litter decomposition. Here, we present the first quantitative analysis of the major climate-change-related drivers of litter decomposition rates in cold northern biomes worldwide. Leaf litters collected from the predominant species in 33 global change manipulation experiments in circum-arctic-alpine ecosystems were incubated simultaneously in two contrasting arctic life zones. We demonstrate that longer-term, large-scale changes to leaf litter decomposition will be driven primarily by both direct warming effects and concomitant shifts in plant growth form composition, with a much smaller role for changes in litter quality within species. Specifically, the ongoing warminginduced expansion of shrubs with recalcitrant leaf litter across cold biomes would constitute a negative feedback to global warming. Depending on the strength of other (previously reported) positive feedbacks of shrub expansion on soil carbon turnover, this may partly counteract direct warming enhancement of litter decomposition

Portrait of Governor Thomas Bibb

This is a circa 1820 portrait of Governor Thomas Bibb, who was the second governor for the State of Alabama

Fusarium Species Infection in Wheat: Impact on Quality and Mycotoxin Accumulation

International audienceWheat is the most consumed cereal worldwide and can be processed to different products for human consumption. This crop can be infected by Fusarium species, among them those within the Fusarium graminearum complex causing Fusarium head blight (FHB. The disease can severely reduce grain yield and quality under conditions of high humidity and warm temperatures during anthesis. Moreover the grains can be contaminated with mycotoxin such as trichothecenes, among them deoxynivalenol and their acetyl derivates 3-ADON, 15-ADON and DON-3-glucoside. Some years, depending on the environmental conditions Fusarium proliferatum can also infect the grain and fumonisin contamination can be observed. To understand the way of grain infection by Fusarium species will help to undertake strategies to reduce the problem both at pre-harvest and during processing to select adequate procedures to manage mycotoxin production. Different strategies at different stages of the wheat chain have been proposed to reduce the impact of FHB and mycotoxin accumulation