Exchangeable Ca2+ content and soil aggregate stability control the soil organic carbon content in degraded Horqin grassland
Exchangeable Ca2+ content and soil aggregate stability control the soil organic carbon content in degraded Horqin grassland
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交换性Ca2+含量和土壤团聚稳定性控制退化科尔沁草原土壤有机碳含量
DOI：
10.1016/j.ecolind.2021.108507
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发表时间：
2022-01
影响因子：
6.9
通讯作者：
Wei Sun
中科院分区：
文献类型：
--
作者：
Yuan Yao;Junda Chen;Fei Li;Mingwei Sun;Xuechen Yang;Gui Wang;Jian-Ying Ma;Wei Sun
土壤有效磷含量对微生物碳利用效率有正影响。·交换性Ca 2+和Mg 2+的流失削弱了土壤有机碳的理化保护作用;·草地退化通过削弱土壤有机碳的理化保护作用而加剧了土壤有机碳的流失;·微生物碳利用效率的提高和微生物生物量的减少减缓了土壤有机碳的流失。草地储存了全球20-30%的土壤有机碳，但大多数草地正在遭受退化伴随着SOC损失。土壤有机碳储量是由植物碳输入和微生物碳输出之间的平衡决定的，但这些因素在控制土壤有机碳中的相对重要性以及土壤有机碳的稳定机制还知之甚少。以科尔沁草地为研究对象，研究了草地退化梯度沿着土壤有机碳流失的主要影响因子，包括非退化草地（ND）、轻度退化草地（LD）、中度退化草地（MD）和重度退化草地（SD）。ND和LD样地土壤有机碳、全氮和全磷含量显著高于MD和SD样地。植物地上、地下和凋落物生物量随着退化的加剧而显著降低。与ND样地相比，LD、MD和SD样地土壤团聚体的平均重量直径分别减小了8.70%、17.39%和26.1%。交换性Ca 2+和Mg 2+含量也沿着降低.结构方程模型的结果表明，草地退化降低了植物生物量，导致土壤有效磷含量增加，从而减少了微生物通过胞外酶的释放而损失的能量，最终导致微生物碳利用效率的提高。相关性分析也证实了微生物碳利用效率与G + /G -比值呈正相关。推升回归树模型的结果表明，在13个变量中，交换性Ca 2+和平均重径是影响土壤有机碳的2个最重要的因子。多价阳离子的化学稳定作用和土壤团聚作用是草地退化过程中土壤有机碳含量变化的主要控制因素。综上所述，尽管微生物通过降低其总生物量和提高其碳利用效率在一定程度上缓解了土壤碳流失，但对土壤有机碳的物理保护作用减弱导致了草地退化过程中土壤有机碳的流失。
• Soil available phosphorus content positively affected microbial C use efficiency. • Exchangeable Ca 2+ and Mg 2+ loss weakened physico-chemical protection of SOC. • Grassland degradation enhanced SOC loss via weakening physico-chemical protection of SOC. • An increase in microbial C use efficiency and decrease in microbial biomass mitigated SOC loss. Grasslands store 20–30% of global soil organic carbon (SOC) but a majority of grasslands are suffering degradation accompanied by SOC loss. SOC stock is determined by the balance between C input from plants and C output from microbial decomposition, but the relative importance of these factors in controlling SOC and the stabilization mechanisms of SOC are poorly understood. Here, we investigated the main factors influencing SOC loss along a grassland degradation gradient in the Horqin grassland, including non-degraded (ND), lightly degraded (LD), moderately degraded (MD), and severely degraded (SD) grasslands. The contents of SOC, TN and TP at the ND and LD sites were significantly higher than those at the MD and SD sites. Plant aboveground, belowground and litter biomass significantly decreased with the intensification of degradation. Compared to the ND site, the mean weight diameter of soil aggregates decreased by 8.70%, 17.39% and 26.1% at the LD, MD and SD sites, respectively. Exchangeable Ca 2+ and Mg 2+ contents also decreased along the degradation gradient. Moreover, the results of structural equation modeling indicated that grassland degradation reduced plant biomass, resulting in an increase in soil available phosphorus content, thus causing less energy losses for microbes through their deployment of extracellular enzymes, eventually leading to an increase in microbial carbon use efficiency. Correlation analysis also confirmed that microbial carbon use efficiency was positively correlated with the ratio of G + /G - . The results of boosted regression tree model suggested that exchangeable Ca 2+ and mean weight diameter were the two most influential factors on SOC among the 13 studied variables. Stabilization mechanisms linked to chemical stabilization by polyvalent cations and soil aggregation were the most important controlling factors on SOC content during grassland degradation. In summary, although microorganisms mitigated soil carbon loss to some extent by decreasing their total biomass and increasing their carbon use efficiency, the weakened physical protection of SOC resulted in SOC loss during grassland degradation.
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