A chironomid-based salinity inference model from lakes on the Tibetan Plateau

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• 作者：Enlou Zhang ; Richard Jones ; Alan Bedford ; Peter Langdon and Hongqu Tang
• 关键词：Chironomids ; Hydrological balance ; Lakes ; Tibetan Plateau ; Transfer functions ; Total Dissolved Salts (TDS).
• 刊名：Journal of Paleolimnology
• 出版年：2007
• 出版时间：November, 2007
• 年：2007
• 卷：38
• 期：4
• 页码：477-491
• 全文大小：350 KB
• 刊物类别：Earth and Environmental Science
• 刊物主题：Environment
  Environment
  Sedimentology
  Climate Change
  Physical Geography
  Hydrobiology
  Geology
  
• 出版者：Springer Netherlands
• ISSN：1573-0417

文摘

Previous studies have shown chironomids to be excellent indicators of environmental change and training sets have been developed in order to allow these changes to be reconstructed quantitatively from subfossil sequences. Here we present the results of an investigation into the relationships between surface sediment subfossil chironomid distribution and lake environmental variables from 42 lakes on the Tibetan Plateau. Canonical correspondence analysis (CCA) revealed that of the 11 measured environmental variables, salinity (measured as total dissolved solids TDS) was most important, accounting for 10.5% of the variance in the chironomid data. This variable was significant enough to allow the development of quantitative inference models. A range of TDS inference models were developed using Weighted Averaging (WA), Partial Least Squares (PLS), Weighted Averaging–Partial Least Squares (WA–PLS), Maximum Likelihood (ML), Modern Analogues Technique (MAT) and Modern Analogues Techniques weighted by similarity (WMAT). Evaluation of the site data indicated that four lakes were major outliers, and after omitting these from the training set the models produced jack-knifed coefficients of determination (r 2) between 0.60 and 0.80, and root-mean-squared errors of prediction (RMSEP) between 0.29 and 0.44 log₁₀ TDS. The best performing model was the two-component WA–PLS model with r 2 _jack = 0.80 and RMSEP_jack = 0.29 log₁₀ TDS. The model results were similar to other chironomid-salinity models developed in different regions, and they also showed similar ecological groupings along the salinity gradient with respect to freshwater/salinity thresholds and community diversity. These results therefore indicate that similar processes may be controlling chironomid distribution across salinity gradients irrespective of biogeographical constraints. The performance of the transfer functions illustrates that chironomid assemblages from the Tibetan Plateau lakes are clearly sensitive indicators of salinity. The models will therefore allow the quantification of long-term records of past water salinity for lacustrine sites across the Tibetan Plateau, which has important implications for future hydrological research in the region.