Abstract
Degraded soil has a high carbon sink potential. However, the carbon sequestration capacity and efficiency of comprehensive control measures in soil erosion areas are still not fully understood, and this information is essential for evaluating the effects of adopted restoration measures. The objective of this study was to determine the restoration of soil organic carbon and active carbon components under the impact of soil erosion measures and reforestation following different restoration ages. A small watershed with four typical restored plots following the same control measures (combination measures with horizontal bamboo burl-groove + replanting trees, shrubs and grasses) but different restoration ages (4 years, 14 years, 24 years and 34 years) and two reference plots (bare land (carbon-depleted) and nearby undisturbed forest (carbon-enriched)) in subtropical China was studied. The results showed that the soil organic carbon contents at a 1 m soil depth and the dissolved organic carbon and microbial biomass carbon concentrations in the upper 60 cm of soils of the four restored lands were higher than those in the bare land. Furthermore, the restored lands of 4 years, 14 years, 24 years and 34 years had soil organic carbon stocks in the 1 m soil depth of 22.83 t hm−2, 21.87 t hm−2, 32.77 t hm−2 and 39.65 t hm−2, respectively, which were higher than the bare land value of 19.86 t hm−2 but lower than the undisturbed forestland value of 75.90 t hm−2. The restored forestlands of 34 years of ecological restoration also had a high potential of being a soil organic carbon sink. Compared to the bare land, the restored lands of 4 years, 14 years, 24 years and 34 years had soil organic carbon sequestration capacities of 2.97 t hm−2, 2.01 t hm−2, 12.91 t hm−2 and 19.79 t hm−2, respectively, and had soil organic carbon sequestration rates of 0.74 t hm−2 a−1, 0.14 t hm−2 a−1, 0.54 t hm−2 a−1 and 0.58 t hm−2 a−1, respectively. Our results indicated that the combined measures of horizontal bamboo burl-groove and revegetation could greatly increase carbon sequestration and accumulation. Suitable microtopography modification and continuous organic carbon sources from vegetation are two main factors influencing soil organic carbon recovery. Combination measures, which can provide suitable topography and a continuous soil organic carbon supply, could be considered in treating degraded soils caused by water erosion in red soil areas.
Highlights
Forest soils play a key role in the global carbon (C) cycle and the future mitigation of climate change because approximately 45% of terrestrial C is in forest soils [1]
At site F4, the w(TOC) decreased by 7.97% compared to bare land (BL), which may be due to human disturbance, causing bamboo-burl-groove construction in the early restoration stage
Horizontal bamboo burl-groove can reduce soil erosion and soil organic carbon (SOC) loss, while vegetation construction mainly plays a role as the source of SOC and nutrients
Summary
Forest soils play a key role in the global carbon (C) cycle and the future mitigation of climate change because approximately 45% of terrestrial C is in forest soils [1]. Long-term severe human disturbance has had a serious effect on subtropical forest ecosystems, with complex topography and climate change resulting in fewer climax forests and a decrease in the functioning of an ecological security barrier [3]. As highlighted by the Bonn Challenge, forest vegetation restoration has become a priority research area in efforts to solve global environmental problems, e.g., the global effort to restore 1.50 × 106 km of degraded land and deforested areas by 2020 [4]. Increasing the C sink of degraded soil has become a major problem to be solved in China. The Chinese government initiated a series of state-funded forestry ecological projects, especially in relation to the key projects of soil and water conservation [9,10]
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