Mechanisms influencing physically sequestered soil carbon in temperate restored grasslands in South Africa and North America
Mechanisms influencing physically sequestered soil carbon in temperate restored grasslands in South Africa and North America
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DOI：
10.1007/s10533-021-00774-y
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发表时间：
2021-03
期刊：
影响因子：
4
通讯作者：
D. Scott;E. Bach;C. D. du Preez;J. Six;S. Baer
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文献类型：
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作者：
D. Scott;E. Bach;C. D. du Preez;J. Six;S. Baer
将碳(C)封存到稳定的土壤库中有可能减缓大气中不断增加的二氧化碳浓度。开垦后恢复的草地土壤碳积累，但物理保护的碳量（这里以微团聚体-大团聚体- C测量）和主要的积累机制尚不清楚。利用美国堪萨斯州东北部不同恢复年龄的数据集，模拟了3个跨大陆地区中温带多年生恢复草原的物理保护碳积累速率；美国内布拉斯加州东南部；以及南非自由邦东北部。此外，我们使用结构方程模型研究了每个遗址中物理保护C含量的主要控制因素。结构方程模型的变量为根系生物量、根系C:N比、土壤结构（以体积密度、每整个土壤质量基础上的大团聚体百分比和每大团聚体质量基础上的大团聚体内微团聚体百分比表示）、微生物组成（以微生物生物量C、总磷脂脂肪酸[PLFA]生物量和丛枝菌根真菌[AMF]生物量表示）、和微团聚体中大团聚体C在整个土壤基础上。在所有站点中，受物理保护的碳以16±5 g m−2年−1的速率累积。来自南非的数据符合为东北KS开发的优先元模型，该模型假设物理保护的C可以解释为微生物组成、土壤结构、根C:N比和根生物量的函数（按对物理保护的C的直接影响强度排序）。与基于模型的假设相反，根C:N比对南非物理保护的C的影响最大（负）。AMF对南非自然保护C的影响较小，这与干旱环境中AMF生物量较低一致。假设的模型不适合内布拉斯加州东南部的数据，可能是由于粘土含量高（~ 30%）。总的来说，这些结果表明，在含有适量粘土（大于10%和小于30%）的土壤中，物理保护的C可以通过根系（生物量和C:N比）、微生物生物量和土壤团聚体的知识来预测。
Sequestering carbon (C) into stable soil pools has potential to mitigate increasing atmospheric carbon dioxide concentrations. Carbon accrues in grassland soil restored from cultivation, but the amount of physically protected C (here measured as microaggregate-within-macroaggregate C) and predominant mechanisms of accrual are not well understood. We modeled the rate of physically protected carbon accrued in three mesic temperate perennial restored grasslands from cross-continental regions using datasets with a wide range of restoration ages from northeast Kansas, USA; southeast Nebraska, USA; and northeast Free State, South Africa. Further, we investigated major controls on the amount of physically protected C in each site using structural equation modeling. Variables in the structural equation model were root biomass, root C:N ratio, soil structure (indicated by bulk density, percent of macroaggregates on a per whole soil mass basis, and percent of microaggregate-within-macroaggregates on a per macroaggregate mass basis), microbial composition (indicated by microbial biomass C, total phospholipid fatty acid [PLFA] biomass, and PLFA biomass of arbuscular mycorrhizae fungi [AMF] biomass), and microaggregate-within-macroaggregate C on a per whole soil mass basis. Across all sites, physically protected C accrued at a rate of 16 ± 5 g m−2year−1. Data from South Africa fit ana priorimetamodel developed for northeast KS that hypothesized physically protected C could be explained as a function of microbial composition, soil structure, root C:N ratio, and root biomass (listed in order of strength of direct effect on physically protected C). In contrast to the model-based hypothesis, root C:N ratio was the strongest influence (negative) on physically protected C in South Africa. The lesser effect of AMF on physically protected C in South Africa was consistent with lower AMF biomass in arid environments. The hypothesized model did not fit southeast Nebraska data possibly due to high (~ 30%) clay content. Overall, these results suggest that physically protected C in soil with moderate amounts of clay (more than 10% and less than 30%) can be predicted with knowledge of roots (biomass and C:N ratio), microbial biomass, and soil aggregation.