Soil organic carbon dynamics following afforestation in the Loess Plateau of China

Abstract

Soil organic carbon (SOC) is the largest terrestrial carbon pool and sensitive to land use and cover change; its dynamics is critical for carbon cycling in terrestrial ecosystems and the atmosphere. In this study, we combined a modeling approach and field measurements to examine the temporal dynamics of SOC following afforestation of former arable land at six sites under different climatic conditions in the Loess Plateau during 1980–2010. The results showed that the measured mean SOC increased to levels higher than before afforestation when taking the last measurements (i.e., at age 25 to 30 yr), although it decreased in the first few years at the wetter sites. The accumulation rates of SOC were 1.58 to 6.22% yr^–1 in the upper 20 cm and 1.62 to 5.15% yr^–1 in the upper 40 cm of soil. The simulations reproduced the basic characteristics of measured SOC dynamics, suggesting that litter input and climatic factors (temperature and precipitation) were the major causes for SOC dynamics and the 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 the first few years at all the sites, although the magnitudes of decreases were small at the drier sites. This suggested that the modeling may be advantageous in capturing SOC changes at finer time scale. The discrepancy between the simulation and measurement was a result of uncertainties in model structure, data input, and sampling design. Our findings indicated that afforestation promoted soil carbon sequestration at the study sites, which is favorable for further restoration of the vegetation and environment. Afforestation activities should decrease soil disturbances to reduce carbon release in the early stage. The long-term strategy for carbon fixation capability of the plantations should also consider the climate and site conditions, species adaptability, and successional stage of recovery

Influence of Vegetation Restoration on Topsoil Organic Carbon in a Small Catchment of the Loess Hilly Region, China

“…Lu et al (2013), studying afforestation in the Loess Plateau, found that the time of the SOC source to sink transition was 3 to 8 years after afforestation. The decrease of SOC in the first few years following afforestation has been attributed to low net primary productivity of plants, decreased litter inputs and increased decomposition rates [12] , [29] .…”

“…Over 60–80% of the land in the Loess Plateau has been affected by soil erosion, with an average annual soil erosion of 2000 to 20000 t km −2 yr −1 [25] –. Severe soil erosion has resulted in land degradation, which was manifested primarily in the thinning of the soil layer, nutrient loss and fertility reduction, which has directly caused decreases in the local farmers' income and has economically and socially hindered sustainable development [27] – [29] . Unreasonable human activities, such as deforestation and tillage on slopes, have further intensified soil erosion and land degradation in the Loess Plateau [30] .…”

Impact of land use type and altitudinal gradient on topsoil organic carbon and nitrogen stocks in the semi-arid watershed of northern Ethiopia

“…On the other hand, the altitudinal gradient affects SOM concentration by controlling temperature regimes, precipitation, solar radiation, relative humidity, and geologic deposition processes (Tsui et al, 2004). SOC's spatial variability is highly heterogeneous due to topography, landscape complex, and soil thickness (Doetterl et al, 2016;Hu et al, 2014;Lu et al, 2013;Patton et al, 2019;Xin et al, 2016). The current study indicates that SOC and TN accumulation in highland areas are due to diverse environmental conditions such as altitude, slope, and location (Arunrat et al, 2020).…”

Spatial Variation in the Storages and Age-Related Dynamics of Forest Carbon Sequestration in Different Climate Zones—Evidence from Black Locust Plantations on the Loess Plateau of China

“…Lu et al . (2013) reported that SOC decreased in the first few years after black locust trees were planted on the Loess Plateau, where the magnitude of decrease was large in wetter sites (MAP ~600 mm) and small in drier sites (MAP from ~450–500 mm) [ 37 ]. Consistently, planting trees has been shown to disturb soil texture and enhance the amount of soil microbiological activity, resulting in the release of some soil C stores to the atmosphere [ 8 ].…”