Spatial variability and uncertainty of soil nitrogen across the conterminous United States at different depths
Spatial variability and uncertainty of soil nitrogen across the conterminous United States at different depths
复制标题
DOI：
10.1002/ecs2.4170
复制
发表时间：
2022-07
期刊：
影响因子：
2.7
通讯作者：
E. M. Smith;R. Vargas;M. Guevara;T. Tarín;R. Pouyat
中科院分区：
文献类型：
--
作者：
E. M. Smith;R. Vargas;M. Guevara;T. Tarín;R. Pouyat
土壤氮是植物生产力和生态系统功能的重要驱动力;因此，从局部到全球尺度了解其空间变异性至关重要。在这里，我们提供了一个定量评估的三维空间分布的土壤氮在美国（CONUS）使用数字土壤制图方法。我们使用随机森林回归克里格算法来预测5 km空间网格上6个土壤深度（0-5，5-15，15-30，30-60，60-100和100-200 cm）的土壤氮浓度和相关的不确定性。在整个美国大陆，有一个很强的空间依赖性，土壤氮浓度下降，但不确定性增加土壤深度。太平洋西北地区、东北地区和五大湖国家生态观测站网络（氖）生态气候区域的土壤氮含量较高。在大西洋新热带区、南落基山脉/科罗拉多高原和东南部氖区域，模型的不确定性较高。我们还将我们的土壤氮预测与来自国家生物量和碳数据集的卫星衍生的总初级生产量和森林生物量进行了比较。最后，我们使用不确定性信息，提出优化的位置设计未来的土壤调查，发现大西洋新热带，太平洋西北，太平洋西南，阿巴拉契亚/坎伯兰高原氖域可能需要更大的调查工作。我们强调需要增加对调节更深深度土壤过程的生物物理因素的了解，以更好地表征土壤的三维空间。我们的研究结果提供了一个国家基准土壤氮的空间变异性和不确定性，并揭示了需要更好的代表性的领域。
Soil nitrogen (N) is an important driver of plant productivity and ecosystem functioning; consequently, it is critical to understand its spatial variability from local‐to‐global scales. Here, we provide a quantitative assessment of the three‐dimensional spatial distribution of soil N across the United States (CONUS) using a digital soil mapping approach. We used a random forest‐regression kriging algorithm to predict soil N concentrations and associated uncertainty across six soil depths (0–5, 5–15, 15–30, 30–60, 60–100, and 100–200 cm) at 5‐km spatial grids. Across CONUS, there is a strong spatial dependence of soil N, where soil N concentrations decrease but uncertainty increases with soil depth. Soil N was higher in Pacific Northwest, Northeast, and Great Lakes National Ecological Observatory Network (NEON) ecoclimatic domains. Model uncertainty was higher in Atlantic Neotropical, Southern Rockies/Colorado Plateau, and Southeast NEON domains. We also compared our soil N predictions with satellite‐derived gross primary production and forest biomass from the National Biomass and Carbon Dataset. Finally, we used uncertainty information to propose optimized locations for designing future soil surveys and found that the Atlantic Neotropical, Pacific Northwest, Pacific Southwest, and Appalachian/Cumberland Plateau NEON domains may require larger survey efforts. We highlight the need to increase knowledge of biophysical factors regulating soil processes at deeper depths to better characterize the three‐dimensional space of soils. Our results provide a national benchmark regarding the spatial variability and uncertainty of soil N and reveal areas in need of a better representation.