Wu Yantao, Guo Zhiwei, Li Zhiyong, Liang Maowei, Tang Yongkang, Zhang Jinghui, Miao Bailing, Wang Lixin, Liang Cuizhu
Key Laboratory of Ecology and Resource Use of the Mongolian Plateau Ministry of Education of China Hohhot China.
Collaborative Innovation Center for Grassland Ecological Security Ministry of Education of China Hohhot China.
Ecol Evol. 2022 Aug 4;12(8):e9182. doi: 10.1002/ece3.9182. eCollection 2022 Aug.
Soil organic carbon (SOC) dynamics is regulated by a complex interplay of factors such as climate and potential anthropogenic activities. Livestocks play a key role in regulating the C cycle in grasslands. However, the interrelationship between SOC and these drivers remains unclear at different soil layers, and their potential relationships network have rarely been quantitatively assessed. Here, we completed a six-year manipulation experiment of grazing exclusion (no grazing: NG) and increasing grazing intensity (light grazing: LG, medium grazing: MG, heavy grazing: HG). We tested light fraction organic carbon (LFOC) and heavy fraction organic carbon (HFOC) in 12 plots along grazing intensity in three soil layers (topsoil: 0-10 cm, mid-soil: 10-30 cm, subsoil: 30-50 cm) to assess the drivers of SOC. Grazing significantly reduced SOC of the soil profile, but with significant depth and time dependencies. (1) SOC and SOC stability of the topsoil is primarily regulated by grazing duration (years). Specifically, grazing duration and grazing intensity increased the SOC lability of topsoil due to an increase in LFOC. (2) Grazing intensity was the major factor affecting the mid-soil SOC dynamics, among which MG had significantly lower SOC than did NG. (3) Subsoil organic carbon dynamics were mainly regulated by climatic factors. The increase in mean annual temperature (MAT) may have promoted the turnover of LFOC to HFOC in the subsoil. When evaluating the impacts of grazing on soil organic fraction, we need to consider the differences in sampling depth and the duration of grazing years. Our results highlight that the key factors influencing SOC dynamics differ among soil layers. Climatic and grazing factors have different roles in determining SOC in each soil layer.
土壤有机碳（SOC）动态受到气候和潜在人为活动等多种因素复杂的相互作用的调节。牲畜在调节草原碳循环中起着关键作用。然而，在不同土壤层中，SOC与这些驱动因素之间的相互关系仍不明确，它们潜在的关系网络也很少得到定量评估。在此，我们完成了一项为期六年的放牧排除（不放牧：NG）和增加放牧强度（轻度放牧：LG、中度放牧：MG、重度放牧：HG）的控制实验。我们在三个土壤层（表土：0 - 10厘米、中层土：10 - 30厘米、底土：30 - 50厘米）沿放牧强度的12个样地中测试了轻组有机碳（LFOC）和重组有机碳（HFOC），以评估SOC的驱动因素。放牧显著降低了土壤剖面的SOC，但具有显著的深度和时间依赖性。（1）表土的SOC及其稳定性主要受放牧持续时间（年）的调节。具体而言，由于LFOC的增加，放牧持续时间和放牧强度增加了表土的SOC易分解性。（2）放牧强度是影响中层土SOC动态的主要因素，其中MG的SOC显著低于NG。（3）底土有机碳动态主要受气候因素调节。年平均温度（MAT）的升高可能促进了底土中LFOC向HFOC的周转。在评估放牧对土壤有机组分的影响时，我们需要考虑采样深度和放牧年份的差异。我们的结果强调，影响SOC动态的关键因素在不同土壤层中有所不同。气候和放牧因素在决定各土壤层的SOC方面具有不同的作用。
