Differential long-term effects of climate change and management on stocks and distribution of soil organic carbon in productive grasslands

[摘要] We studied the impact of climate change on the dynamics of soil organiccarbon (SOC) stocks in productive grassland systems undergoing two types ofmanagement, an intensive type with frequent harvests and fertilizerapplications and an extensive system without fertilization and fewerharvests. Simulations were conducted with a dedicated newly developed model,the Oensingen Grassland Model. It was calibrated using measurements taken ina recently established permanent sward in Central Switzerland, and run tosimulate SOC dynamics over 2001–2100 under various climate change scenariosassuming different elements of IPCC A2 emission scenarios. We found that:(1) management intensity dominates SOC until approximately 20 years aftergrassland establishment. Differences in SOC between climate scenarios becomesignificant after 20 years and climate effects dominate SOC dynamics fromapproximately 50 years after establishment. (2) Carbon supplied throughmanure contributes about 60 % to measured organic C increase in fertilizedgrassland. (3) Soil C accumulates particularly in the top 10 cm of the soiluntil 5 years after establishment. In the long-term, C accumulation takesplace in the top 15 cm of the soil profile, while C content decreases belowthis depth. The transitional depth between gains and losses of C mainlydepends on the vertical distribution of root senescence and root biomass. Wediscuss the importance of previous land use on carbon sequestrationpotentials that are much lower at the Oensingen site under ley-arablerotation with much higher SOC stocks than most soils under arable crops. Wefurther discuss the importance of biomass senescence rates, because Cbalance estimations indicate that these may differ considerably between thetwo management systems.

[学科分类] 地球化学与岩石