Abstract Soil organic carbon (SOC) stocks in Australia’s temperate forests have been overlooked in national soil databases and in global SOC analyses of natural ecosystems despite the importance of temperate forests to the global terrestrial carbon balance. This limits the potential to both predict change in SOC stocks in temperate Australia and to identify where and how SOC stocks can be managed to mitigate climate change. Based on data from 707 sites, we examine variations in SOC concentrations and stocks across a range of natural temperate broadleaf forests in south-eastern Australia. Comparisons with current Australia-wide databases highlight previous under-estimation of forest SOC concentrations, leading to substantial underprediction of SOC stocks in the most productive forests (e.g. this study’s mean of 207 Mg C ha−1 compared with a database mean estimate of 141 Mg C ha−1 for Tall open-forests to 30-cm soil depth). Random Forest models involving 27 environmental variables (representing climate, terrain, parent material, soil attributes, vegetation, and fire history) explained up to 79% of the variation in SOC concentrations and 77% of the variation in SOC stocks to 30-cm depth. Climate variables (precipitation, temperature) were of greatest importance to the prediction of both SOC concentrations and SOC stocks, tending to override the importance of terrain and fire-history variables at this study’s regional scale. While patterns in SOC concentrations and stocks were correlated, SOC concentrations were not a reliable proxy for SOC stocks to 10-cm depth, reiterating the importance of mass equivalent measures (i.e. soil bulk density) to assessing changes in soil carbon storage. Our study provides a timely check of the model-based estimates of SOC concentrations and stocks in Australia’s temperate forests that are currently available in nation-wide databases and improves the available information for defining benchmarks, and for identifying potential areas of SOC loss and gain, in programs that aim to mitigate climate change.

中文翻译：

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澳大利亚温带森林土壤有机碳的提炼基准

摘要 尽管温带森林对全球陆地碳平衡很重要，但澳大利亚温带森林的土壤有机碳 (SOC) 储量在国家土壤数据库和自然生态系统的全球 SOC 分析中一直被忽视。这限制了预测澳大利亚温带 SOC 储量变化以及确定可在何处以及如何管理 SOC 储量以缓解气候变化的潜力。根据来自 707 个地点的数据，我们研究了澳大利亚东南部一系列天然温带阔叶林中 SOC 浓度和库存的变化。与当前澳大利亚范围内的数据库的比较突出了先前对森林 SOC 浓度的低估，导致对生产力最高的森林（例如 本研究的平均值为 207 Mg C ha-1，而对于 30 厘米土壤深度的高大开阔森林，数据库平均估计值为 141 Mg C ha-1）。涉及 27 个环境变量（代表气候、地形、母质、土壤属性、植被和火灾历史）的随机森林模型解释了高达 79% 的 SOC 浓度变化和 77% 的 30 厘米深度 SOC 储量变化. 气候变量（降水、温度）对 SOC 浓度和 SOC 储量的预测最为重要，在本研究的区域尺度上，往往会忽略地形和火灾历史变量的重要性。虽然 SOC 浓度和储量的模式相关，但 SOC 浓度不是 10 厘米深度 SOC 储量的可靠代表，重申质量等效措施的重要性（即 土壤容重）来评估土壤碳储存的变化。我们的研究及时检查了澳大利亚温带森林中基于模型的 SOC 浓度和存量估计值，这些估计值目前可在全国数据库中使用，并改进了用于定义基准和识别 SOC 损失和增加的潜在区域的可用信息，在旨在减缓气候变化的计划中。