Roth Holly K, Nelson Amelia R, McKenna Amy M, Fegel Timothy S, Young Robert B, Rhoades Charles C, Wilkins Michael J, Borch Thomas
Department of Chemistry, Colorado State University, Fort Collins, CO, USA.
Department of Soil and Crop Sciences, Colorado State University, Fort Collins, CO, USA.
Environ Sci Process Impacts. 2022 Oct 19;24(10):1661-1677. doi: 10.1039/d2em00184e.
Wildfires, which are increasing in frequency and severity in the western U.S., impact water quality through increases in erosion, and transport of nutrients and metals. Meanwhile, beaver populations have been increasing since the early 1900s, and the ponds they create slow or impound hydrologic and elemental fluxes, increase soil saturation, and have a high potential to transform redox active elements (, oxygen, nitrogen, sulfur, and metals). However, it remains unknown how the presence of beaver ponds in burned watersheds may impact retention and transformation of chemical constituents originating in burned uplands (, pyrogenic dissolved organic matter; pyDOM) and the consequences for downstream water quality. Here, we investigate the impact of beaver ponds on the chemical properties and molecular composition of dissolved forms of C and N, and the microbial functional potential encoded within these environments. The chemistry and microbiology of surface water and sediment changed along a stream sequence starting upstream of fire and flowing through multiple beaver ponds and interconnecting stream reaches within a burned high-elevation forest watershed. The relative abundance of N-containing compounds increased in surface water of the burned beaver ponds, which corresponded to lower C/N and O/C, and higher aromaticity as characterized by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The resident microbial communities lack the capacity to process such aromatic pyDOM, though genomic analyses demonstrate their potential to metabolize various compounds in the anaerobic sediments of the beaver ponds. Collectively, this work highlights the role of beaver ponds as biological "hotspots" with unique biogeochemistry in fire-impacted systems.
美国西部野火发生的频率和强度不断增加，通过加剧侵蚀以及营养物质和金属的迁移，对水质产生影响。与此同时，自20世纪初以来，海狸数量一直在增加，它们建造的池塘减缓或拦截了水文和元素通量，增加了土壤饱和度，并且极有可能转化氧化还原活性元素（碳、氧、氮、硫和金属）。然而，火烧流域中的海狸池塘如何影响源自火烧高地的化学成分（如热解溶解有机物；热解DOM）的保留和转化以及对下游水质的影响仍不清楚。在此，我们研究了海狸池塘对溶解态碳和氮的化学性质、分子组成以及这些环境中编码的微生物功能潜力的影响。地表水和沉积物的化学性质及微生物学特征沿着一条溪流序列发生变化，该溪流始于火灾上游，流经多个海狸池塘，并连接了一个火烧高海拔森林流域内的多个溪流段。在火烧海狸池塘的地表水中，含氮化合物的相对丰度增加，这与较低的碳氮比和氧碳比以及较高的芳香性相对应，这是通过傅里叶变换离子回旋共振质谱（FT-ICR MS）表征的。虽然基因组分析表明常驻微生物群落有潜力在海狸池塘的厌氧沉积物中代谢各种化合物，但它们缺乏处理此类芳香热解DOM的能力。总体而言，这项研究突出了海狸池塘在受火灾影响的系统中作为具有独特生物地球化学性质的生物“热点”的作用。
