Viscarra Rossel Raphael A, Webster Richard, Bui Elisabeth N, Baldock Jeff A
Bruce E. Butler Laboratory, CSIRO Land and Water, PO Box 1666, Canberra, ACT, 2601, Australia.
Glob Chang Biol. 2014 Sep;20(9):2953-70. doi: 10.1111/gcb.12569. Epub 2014 Apr 28.
We can effectively monitor soil condition-and develop sound policies to offset the emissions of greenhouse gases-only with accurate data from which to define baselines. Currently, estimates of soil organic C for countries or continents are either unavailable or largely uncertain because they are derived from sparse data, with large gaps over many areas of the Earth. Here, we derive spatially explicit estimates, and their uncertainty, of the distribution and stock of organic C in the soil of Australia. We assembled and harmonized data from several sources to produce the most comprehensive set of data on the current stock of organic C in soil of the continent. Using them, we have produced a fine spatial resolution baseline map of organic C at the continental scale. We describe how we made it by combining the bootstrap, a decision tree with piecewise regression on environmental variables and geostatistical modelling of residuals. Values of stock were predicted at the nodes of a 3-arc-sec (approximately 90 m) grid and mapped together with their uncertainties. We then calculated baselines of soil organic C storage over the whole of Australia, its states and territories, and regions that define bioclimatic zones, vegetation classes and land use. The average amount of organic C in Australian topsoil is estimated to be 29.7 t ha(-1) with 95% confidence limits of 22.6 and 37.9 t ha(-1) . The total stock of organic C in the 0-30 cm layer of soil for the continent is 24.97 Gt with 95% confidence limits of 19.04 and 31.83 Gt. This represents approximately 3.5% of the total stock in the upper 30 cm of soil worldwide. Australia occupies 5.2% of the global land area, so the total organic C stock of Australian soil makes an important contribution to the global carbon cycle, and it provides a significant potential for sequestration. As the most reliable approximation of the stock of organic C in Australian soil in 2010, our estimates have important applications. They could support Australia's National Carbon Accounting System, help guide the formulation of policy around carbon offset schemes, improve Australia's carbon balances, serve to direct future sampling for inventory, guide the design of monitoring networks and provide a benchmark against which to assess the impact of changes in land cover, land management and climate on the stock of C in Australia. In this way, these estimates would help us to develop strategies to adapt and mitigate the effects of climate change.
只有借助准确的数据来界定基线，我们才能有效地监测土壤状况，并制定合理的政策以抵消温室气体排放。目前，各国或各大洲的土壤有机碳估算数据要么无法获取，要么在很大程度上不确定，因为这些数据来自稀疏的数据，在地球的许多区域存在很大空白。在此，我们得出了澳大利亚土壤中有机碳分布和储量的空间明确估算值及其不确定性。我们整合并统一了来自多个来源的数据，以生成关于该大陆土壤中有机碳当前储量的最全面数据集。利用这些数据，我们制作了大陆尺度上有机碳的精细空间分辨率基线图。我们描述了如何通过结合自助法、基于环境变量的分段回归决策树和残差的地统计建模来制作该图。在一个3弧秒（约90米）的网格节点上预测储量值，并将其与不确定性一起绘制出来。然后，我们计算了整个澳大利亚及其各州、领地以及定义生物气候区、植被类别和土地利用的区域的土壤有机碳储存基线。澳大利亚表层土壤中有机碳的平均含量估计为29.7吨/公顷，95%置信区间为22.6至37.9吨/公顷。该大陆0至30厘米土层中有机碳的总储量为24.97亿吨，95%置信区间为19.04至31.83亿吨。这约占全球土壤上层30厘米总储量的3.5%。澳大利亚占全球陆地面积的5.2%，因此澳大利亚土壤中的有机碳总储量对全球碳循环做出了重要贡献，并且具有显著的固碳潜力。作为2010年澳大利亚土壤中有机碳储量最可靠的近似值，我们的估算具有重要应用。它们可以支持澳大利亚的国家碳核算系统，帮助指导围绕碳抵消计划的政策制定，改善澳大利亚的碳平衡，用于指导未来清单抽样，指导监测网络的设计，并提供一个基准，据此评估土地覆盖、土地管理和气候的变化对澳大利亚碳储量的影响。通过这种方式，这些估算将有助于我们制定适应和减轻气候变化影响的策略。
