Leibniz University Hannover, Institute of Soil Science, Hannover, Germany.
Ludwig-Maximilians-Universität München, Department of Geography, Munich, Germany.
Sci Total Environ. 2022 Sep 10;838(Pt 4):156542. doi: 10.1016/j.scitotenv.2022.156542. Epub 2022 Jun 9.
The Tibetan Plateau (TP) is a sensitive alpine environment of global importance, being Asia's water tower, featuring vast ice masses and comprising the world's largest alpine grasslands. Intensified land-use and pronounced global climate change have put pressure on the environment of the TP. We studied the tempo-spatial variability of dissolved organic matter (DOM) to better understand the fluxes of nutrients and energy from terrestrial to aquatic ecosystems in the TP. We used a multiparametrical approach, based on inorganic water chemistry, dissolved organic carbon (DOC) concentration, dissolved organic matter (DOM) characteristics (chromophoric DOM, fluorescence DOM and δC of DOM) in stream samples of three catchments of the Nam Co watershed and the lake itself. Satellite based plant cover estimates were used to link biogeochemical data to the structure and degradation of vegetation zones in the catchments. Catchment streams showed site-specific DOM signatures inherited from glaciers, wetlands, groundwater, and Kobresia pygmaea pastures. By comparing stream and lake samples, we found DOM processing and unification by loss of chromophoric DOM signatures and a change towards an autochthonous source of lake DOM. DOM diversity was largest in the headwaters of the catchments and heavily modified in terminal aquatic systems. Seasonality was characterized by a minor influence of freshet and by a very strong impact of the Indian summer monsoon on DOM composition, with more microbial DOM sources. The DOM of Lake Nam Co differed chemically from stream water samples, indicating the lake to be a quasi-marine environment in regards to the degree of chemical modification and sources of DOM. DOM proved to be a powerful marker to elucidate consequences of land use and climatic change on biogeochemical processes in High Asian alpine ecosystems.
青藏高原（TP）是一个对全球具有重要意义的敏感高山环境，是亚洲的水塔，拥有广阔的冰体，是世界上最大的高山草原。土地利用的加剧和明显的全球气候变化给青藏高原的环境带来了压力。我们研究了溶解有机物（DOM）的时空调变，以更好地了解从陆地到高山生态系统的营养物质和能量通量。我们使用了一种多参数方法，基于无机水化学、溶解有机碳（DOC）浓度、溪流样品中的溶解有机物（DOM）特征（发色DOM、荧光 DOM 和 DOM 的δC），这三个流域的流域和湖泊本身。基于卫星的植被覆盖估计用于将生物地球化学数据与流域植被带的结构和退化联系起来。流域溪流显示出特定于地点的 DOM 特征，这些特征来源于冰川、湿地、地下水和矮嵩草草甸。通过比较溪流和湖泊样本，我们发现 DOM 处理和统一是通过损失发色 DOM 特征和向湖泊 DOM 的自生来源转变来实现的。DOM 的多样性在流域的源头最大，并在终端水生系统中受到严重的修饰。季节性的特点是洪水的影响较小，而印度夏季季风对 DOM 组成的影响非常大，微生物 DOM 来源更多。纳木错湖的 DOM 在化学上与溪流水样不同，表明该湖在化学修饰程度和 DOM 来源方面具有准海洋环境的特征。DOM 被证明是一个强大的标记，以阐明土地利用和气候变化对高山高山生态系统生物地球化学过程的影响。
