State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, College of Natural Resources and Environment, Northwest A&F University, Yangling, 712100, Shaanxi, China.
State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, College of Natural Resources and Environment, Northwest A&F University, Yangling, 712100, Shaanxi, China.
J Environ Manage. 2024 May;359:120998. doi: 10.1016/j.jenvman.2024.120998. Epub 2024 Apr 26.
Afforestation is beneficial to improving soil carbon pools. However, due to the lack of deep databases, the variations in soil carbon and the combined effects of multiple factors after afforestation have yet to be adequately explored in >1 m deep soils, especially in areas with deep-rooted plants and thick vadose zones. This study examined the multivariate controls of soil organic carbon (SOC) and inorganic carbon (SIC) in 0-18 m deep under farmland, grassland, willow, and poplar in loess deposits. The novelty of this study is that the factors concurrently affecting deep soil carbon were investigated by multiwavelet coherence and structural equation models. On average, the SOC density (53.1 ± 5.0 kg m) was only 12% of SIC density (425.4 ± 13.8 kg m), with depth-dependent variations under different land use types. In the soil profiles, the variations in SOC were more obvious in the 0-6 m layer, while SIC variations were mainly observed in the 6-12 m layer. Compared with farmland (SOC: 17.0 kg m; SIC: 122.9 kg m), the plantation of deciduous poplar (SOC: 28.5 kg m; SIC: 144.2 kg m) increased the SOC and SIC density within the 0-6 m layer (p < 0.05), but grassland and evergreen willow impacted SOC and SIC density insignificantly. The wavelet coherence analysis showed that, at the large scale (>4 m), SOC and SIC intensities were affected by total nitrogen-magnetic susceptibility and magnetic susceptibility-water content, respectively. The structural equation model further identified that SOC density was directly controlled by total nitrogen (path coefficient = 0.64) and indirectly affected by magnetic susceptibility (path coefficient = 0.36). Further, SOC stimulated the SIC deposition by improving water conservation and electrical conductivity. This study provides new insights into afforestation-induced deep carbon cycles, which have crucial implications for forest management and enhancing ecosystem sustainability in arid regions.
造林有利于提高土壤碳库。然而，由于缺乏深入的数据库，造林后 >1 米深处土壤碳的变化以及多种因素的综合影响尚未得到充分探索，尤其是在根系深植植物和厚隔水层地区。本研究考察了黄土沉积物中农田、草地、柳树和杨树下 0-18 米深处土壤有机碳（SOC）和无机碳（SIC）的多变量控制。本研究的新颖之处在于，通过多小波相干和结构方程模型研究了同时影响深层土壤碳的因素。平均而言，SOC 密度（53.1±5.0 kg·m）仅为 SIC 密度（425.4±13.8 kg·m）的 12%，且在不同土地利用类型下具有随深度变化的特征。在土壤剖面中，SOC 的变化在 0-6 米层更为明显，而 SIC 的变化主要发生在 6-12 米层。与农田（SOC：17.0 kg·m；SIC：122.9 kg·m）相比，落叶松人工林（SOC：28.5 kg·m；SIC：144.2 kg·m）增加了 0-6 米层的 SOC 和 SIC 密度（p<0.05），而草地和常绿柳树对 SOC 和 SIC 密度的影响不显著。小波相干分析表明，在大尺度（>4 m）上，SOC 和 SIC 强度分别受总氮-磁化率和磁化率-含水量的影响。结构方程模型进一步确定，SOC 密度直接受总氮控制（路径系数=0.64），间接受磁化率影响（路径系数=0.36）。此外，SOC 通过改善保水能力和电导率来促进 SIC 的沉积。本研究为造林引起的深层碳循环提供了新的见解，对干旱地区的森林管理和增强生态系统可持续性具有重要意义。
