Australian Rivers Institute, Griffith University, 170 Kessels Road, Nathan, Brisbane, QLD 4111, Australia.
Australian Rivers Institute, Griffith University, 170 Kessels Road, Nathan, Brisbane, QLD 4111, Australia; Laboratoire des Sciences du Climat et de l'Environnement, Unité Mixte de Recherche (CEA/CNRS/UVSQ), Gif-sur-Yvette 91198, France.
Sci Total Environ. 2017 Jan 1;575:1384-1394. doi: 10.1016/j.scitotenv.2016.09.219. Epub 2016 Oct 5.
Understanding the sources of sediment, organic matter and nitrogen (N) transferred from terrestrial to aquatic environments is important for managing the deleterious off-site impacts of soil erosion. In particular, investigating the sources of organic matter associated with fine sediment may also provide insight into carbon (C) and N budgets. Accordingly, the main sources of fine sediment, organic matter (indicated by total organic carbon), and N are determined for three nested catchments (2.5km, 75km, and 3076km) in subtropical Australia. Source samples included subsoil and surface soil, along with C and C vegetation. All samples were analysed for stable isotopes (δC, δN) and elemental composition (TOC, TN). A stable isotope mixing model (SIAR) was used to determine relative source contributions for different spatial scales (nested catchments), climatic conditions and flow stages. Subsoil was the main source of fine sediment for all catchments (82%, SD=1.15) and the main N source at smaller scales (55-76%, SD=4.6-10.5), with an exception for the wet year and at the larger catchment, where surface soil was the dominant N source (55-61%, SD=3.6-9.9), though contributions were dependent on flow (59-680m/s). C litter was the main source of organic C export for the two larger catchments (53%, SD=3.8) even though C grasses dominate the vegetation cover in these catchments. The sources of fine sediment, organic matter and N differ in subtropical catchments impacted by erosion, with the majority of C derived from C leaf litter and the majority of N derived from either subsoil or surface soil. Understanding these differences will assist management in reducing sediment, organic matter and N transfers in similar subtropical catchments while providing a quantitative foundation for testing C and N budgets.
了解从陆地向水生环境转移的泥沙、有机质和氮（N）的来源，对于管理土壤侵蚀的有害场外影响非常重要。特别是，研究与细泥沙相关的有机质来源，也可以深入了解碳（C）和 N 预算。因此，对澳大利亚亚热带地区三个嵌套流域（2.5km、75km 和 3076km）的细泥沙、有机质（以总有机碳表示）和 N 的主要来源进行了确定。源样本包括亚土层和表土层，以及 C 和 C 植被。所有样本均进行了稳定同位素（δC、δN）和元素组成（TOC、TN）分析。使用稳定同位素混合模型（SIAR）确定不同空间尺度（嵌套流域）、气候条件和流量阶段的相对源贡献。亚土层是所有流域细泥沙的主要来源（82%，SD=1.15），也是较小尺度的主要 N 来源（55-76%，SD=4.6-10.5），但在湿年和较大流域中，表土是主要的 N 来源（55-61%，SD=3.6-9.9），尽管其贡献取决于流量（59-680m/s）。C 凋落物是两个较大流域有机质输出的主要来源（53%，SD=3.8），尽管 C 草类在这些流域的植被覆盖中占主导地位。受侵蚀影响的亚热带流域中，泥沙、有机质和 N 的来源不同，大部分 C 来自 C 叶凋落物，大部分 N 来自亚土层或表土层。了解这些差异将有助于在类似的亚热带流域中减少泥沙、有机质和 N 的转移，同时为测试 C 和 N 预算提供定量基础。
