Climatic and Geochemical Controls on Soil Carbon at the Continental Scale: Interactions and Thresholds
Climatic and Geochemical Controls on Soil Carbon at the Continental Scale: Interactions and Thresholds
复制标题
DOI：
10.1029/2020gb006781
复制
发表时间：
2021-03
影响因子：
5.2
通讯作者：
Wenjuan Yu;S. Weintraub;S. Hall
中科院分区：
文献类型：
--
作者：
Wenjuan Yu;S. Weintraub;S. Hall
以往的研究发现，温度和降水与地球化学变量预测土壤有机碳（SOC）浓度和趋势的重要性相互矛盾的结果与深度，大多数利用线性统计模型。为了调和这一争议，我们使用了来自北美国家生态观测站网络675个坑的2574个矿物层位的数据，这些数据通常收集到1米深。气候是土壤有机碳的基本预测因子，其作用与地球化学预测因子相似。然而，这只出现在广义可加混合模型和随机森林模型中，在线性混合模型中被掩盖。水分有效性与有机碳的关系在非常干旱的生态系统中最强，在年平均温度< 0°C时，有机碳增加最强烈。在所有模型中，深度，草酸可提取的铝（Alox），pH值，交换性钙和交换性镁是重要的，而粉砂+粘土，草酸可提取的铁（Feox），植被类型是较弱的预测。气候和pH值是独立相关的SOC，也与地球化学组成：Feox和Alox相关性更强的SOC在潮湿或寒冷的气候。大多数预测与SOC的非线性阈值关系，和饱和反应增加活性金属表明土壤中的SOC可能是有限的C输入。我们观察到的地球化学和气候预测SOC的相对重要性，随着深度的增加，挑战以前的声明。总的来说，我们的研究结果挑战了地球化学后气候是多余的概念，并表明考虑它们的非线性和相互作用可以提高SOC的空间预测。
Previous studies found conflicting results on the importance of temperature and precipitation versus geochemical variables for predicting soil organic carbon (SOC) concentrations and trends with depth, and most utilized linear statistical models. To reconcile the controversy, we used data from 2574 mineral horizons from 675 pits from National Ecological Observatory Network sites across North America, typically collected to 1 m depth. Climate was a fundamental predictor of SOC and played similarly important roles as some geochemical predictors. Yet, this only emerged in the generalized additive mixed model and random forest model and was obscured in the linear mixed model. Relationships between water availability and SOC were strongest in very dry ecosystems and SOC increased most strongly at mean annual temperature < 0°C. In all models, depth, oxalate‐extractable Al (Alox), pH, and exchangeable calcium plus exchangeable magnesium were important while silt + clay, oxalate‐extractable Fe (Feox), and vegetation type were weaker predictors. Climate and pH were independently related to SOC and also interacted with geochemical composition: Feox and Alox related more strongly to SOC in wet or cold climates. Most predictors had nonlinear threshold relationships with SOC, and a saturating response to increasing reactive metals indicates soils where SOC might be limited by C inputs. We observed a mostly constant relative importance of geochemical and climate predictors of SOC with increasing depth, challenging previous statements. Overall, our findings challenge the notion that climate is redundant after accounting for geochemistry and demonstrate that considering their nonlinearities and interactions improves spatial predictions of SOC.