Research Of Lake Diatom Community And Biodiversity Distribution Feature In Yunnan

During the past few decades, global warming and human activities such as land use have signficntly changed the functioning and structure of ecosystems, posing serious challenges to the conservation of biodiversity. Lakes serve as a special natural complex and are in risk of multiple environmental stressors such as eutrophication, industrial pollution and hydrological modulation. These have signficantly influenced the community structure and the distribution patterns of aquatic biota. Yunnan, located southwest China, is characterized by a variety of climate types and diverse landscapes. Yunnan is known for high biodiversity and abundant biological resources, serving as one of world’s biodiversity hotspots. However, much of what is known about biodiversity in Yunnan is derived from terrestrial ecossytems and short-term surveys and little is known of aquatic ecosystems and the long-term patterns of the change in local biodiversity. Therefore, it is urgently needed to uncover the spatio-temporal patterns of lacustrine biodiversity and to identify the key stressors, so that sustainable management and conservation of lake biodiversity can be achieved. Here, we apply surface sediment records to explore the spatial patterns of diatom community and biodiversity and to identify the key driving factors in 22 lakes. In addition, sedimentary diatom records from Fuxian and Dianchi, which are characterized by distinct limnological features and human disturbances, were examined to reveal the long-term change in diatom communities and to compare the patterns in productivity-diversity relationship between both lakes.The main results from this thesis include: · 1) that regional distribution of diatom communities is mainly affect by lake morphology, water chemistry and lake productivity, but predominantly by lake productivity over the last century in Fuxian and Dianchi lakes.· 2) that some diatoms can be sensitive indicators of lake environment, including Cyclotella ocellata as a indicator of nutrient-poor waters, and Nitzschia gracilis as an indicator of lake eutrophication. · 3) that the biodiversity patterns based on alpha and beta diversity are consistent in response to lake productivity over both time and space, with the relationship between lake productivity and diatom diversity being hump-shaped in both deep and shallow lakes over space, and showing different models between Fuxian and Dianchi lakes over time; · 4) and finally, that diatom diversity played different roles in maintaning community productivity in Fuxian and Dianchi lakes, suggesting that the intensity ofhuman disturbance can modulate the role of biodiversity in maintaining ecosystem functioning.