Soil organic carbon dynamics of black locust plantations in the middle Loess Plateau area of China

[摘要] Soil organic carbon (SOC) is the largest terrestrial carbon pool andsensitive to land use and cover change; its dynamics are critical for carboncycling in terrestrial ecosystems and the atmosphere. In this study, wecombined a modeling approach and field measurements to examine the temporaldynamics of SOC following afforestation (Robinia pseudoacacia) of former arable land at sixsites under different climatic conditions in the Loess Plateau during1980–2010, where the annual mean precipitation ranging from 450 mm to 600 mm. Theresults showed that the measured mean SOC increased to levels higher thanbefore afforestation when taking the last measurements (i.e., at age 25 to30 yr) at all the sites, although it decreased at the wetter sites in thefirst few years. The accumulation rates of SOC were 1.58 to 6.22% yr⁻¹in the upper 20 cm and 1.62 to 5.15% yr⁻¹in the upper40 cm of soil. The simulations reproduced the basic characteristics ofmeasured SOC dynamics, suggesting that litter input and climatic factors(temperature and precipitation) were the major causes for SOC dynamics andthe differences among the sites. They explained 88–96, 48–86 and 57–74%of the variations in annual SOC changes at the soil depths of 0–20, 0–40,and 0–100 cm, respectively. Notably, the simulated SOC decreased during thefirst few years at all the sites, although the magnitudes of decreases weresmaller at the drier sites. This suggested that the modeling may beadvantageous in capturing SOC changes at finer timescale. The discrepancybetween the simulation and measurement was a result of uncertainties inmodel structure, data input, and sampling design. Our findings indicatedthat afforestation promoted soil carbon sequestration at the study sitesduring 1980–2010. Afforestation activities should decrease soil disturbancesto reduce carbon release in the early stage. The long-term strategy forcarbon fixation capability of the plantations should also consider theclimate and site conditions, species adaptability, and successional stage ofrecovery.

[学科分类] 地球化学与岩石