Littoral zones of lakes are important for carbon and nutrient recycling because of the accumulation and decomposition of organic matter (OM) coming from terrestrial and aquatic plants. Here, we aimed to study OM decomposition from the most abundant riparian trees (Nothofagus dombeyi and Myrceugenia exsucca), and an emergent macrophyte (Schoenoplectus californicus), in the littoral zone of an ultraoligotrophic North-Patagonian Andean lake. We analysed the initial 2-days leaching, and litter mass loss and litter nutrient changes after one year of decomposition in a litter-bag experiment. The three studied species had very slow decay rates (k < 0.005 day⁻¹), and initial nutrient release by leaching was not related to differences in decomposition rates. However, differences in leaf traits (lignin content) were related to interspecific variation in decomposition rates. The highest decomposition rates were observed for the macrophyte S. californicus, the species with the lower lignin content, while the opposite was observed in the Myrtaceae M. exsucca. In the three studied species, nitrogen content increased during decomposition. Our results indicated that in the shore of ultra-oligotrophic lakes, litter remains for long periods with net nutrient immobilization, thus OM of the riparian vegetation represents a carbon and nutrient sink.

由于来自陆地和水生植物的有机物质 (OM) 的积累和分解，湖泊沿岸带对碳和养分循环很重要。在这里，我们的目的是研究最丰富的河岸树（Nothofagus dombeyi和Myrceugenia exsucca）和一种新兴的大型植物（Schoenoplectus californicus）的有机质分解，位于超贫营养的北巴塔哥尼亚安第斯湖沿岸地区。我们在垃圾袋实验中分析了最初 2 天的浸出，以及分解一年后的垃圾质量损失和垃圾营养变化。三个研究的物种具有非常缓慢的衰减率（k < 0.005 天^-1)，并且通过浸出的初始养分释放与分解速率的差异无关。然而，叶片性状（木质素含量）的差异与分解率的种间差异有关。对于木质素含量较低的大型植物S. californicus观察到最高的分解率，而在桃金娘科M. exsucca 中观察到相反的情况。在三个研究的物种中，氮含量在分解过程中增加。我们的研究结果表明，在超贫营养湖泊的岸边，枯枝落叶长期保持净养分固定，因此河岸植被的 OM 代表了碳和养分汇。