Carbon fluxes and vegetal groups composition of an alpine grassland in relation to grazing and climate

Mountain prairies represent vulnerable ecosystems whose resilience is strictly connected to climate but also to management practices. During the years 2008 and 2009 in the alpine pasture (Festuco-Deschampsieto) of Malga Arpaco (Italy), monitoring actions of the grassland species compositions and greenhouse gases emissions were carried out through chamber-based measurements. About a hundred of cattle beef and dairy cows grazed in three summer months of both years. Summer 2008 recorded warmer June and July than the average and abundant rains whilst in
summer 2009 mean temperature in July and August was much higher than the average. NEE per leaf area index (NEE/LAI), soil respiration (Rsoil) and night respiration per leaf area index (Rpatch) were measured fortnightly on patches of grassland in the grazed area. The results showed higher Rsoil in the grazed area compared to an ungrazed area as control, likely connected to higher soil fertility (richer in N and C). LAI of different patches of vegetation pattern was generally lower in 2009 and the best NEE/LAI was observed in patches of mixed vegetal groups than in patches of D. cespitosa which resulted little effective on carbon uptake. On the other side, grasses
and forbs showed the highest values of Rpatch. Regarding the vegetation composition, a strong decrease of grasses in summer 2008 -likely connected to the higher presence of palatable grasses species and the cattle selectivity, and ontrast, an increase of invasive species cover (D. cespitosa and C. eriophorum) and less selectivity between grasses and forbs in 2009 were observed. The results lead to think about the role of management practices in connection to climate variables, in bounding the spread of invasive and little palatable species like D. cespitosa and C. eriophorum, also little influent on carbon sequestration.