Zonal Species Distribution Response To Climate Change In Yanhe River Catchment

Loess Plateau, with fragile ecological environment, is very sensitive to climate change. Climate change may cause changes in vegetation structure and productivity and create opportunities for niche differentiation when empty niches are created at rear edges of range shifts. Moreover, the climate change will lead to more notable changes in species distribution and a more significant shift in realized niche due to the complex topography in the loess Plateau. Conservation managers must be able to detect measure and accurately predict such impacts of climate change on species in order to mitigate impacts on biodiversity and ecological restoration. This paper will try to address this problem through a case study in Yanhe River Catchment, aiming at studying the relations between remnant natural vegetation and environment, and building prediction models for different species. Combining with GIS spatial analysis, to predict the zonal species distribution in Yanhe River catchment and quantify the drifts of species niche center in main environmental gradients under six climate change scenarios in 2050, aiming at providing a simulated reference system for the planning and decision-making under climate changes in natural conservation and ecological restoration and studying methods accurately detecting species responses to climate change. As an initial work in this area, the author hopes that this work can provide scientific implications for ecological restoration under climate change scenarios in Yanhe River catchment, and experiences in methods and model building for studies in large scale. Here are the main outputs.1) Based on the sampling plan according to stratification sampling and random sampling strategies, this paper collected 265 sample plots. It can meet with the requirement of building GAM(generalized additive models)model. Based the model building on the equilibrium theories, which assumed that the vegetation is in a relative equilibrium with environment, GAM models were built for 23 zonal species. The minumum of ROC validation of these models is 0.7, and cvROC is 0.6. Validation of these models showed that established models are sound in terms of statistic terms. According to the established GAM models, this paper mapped 23 species'distribution in Arcview using GAM models and lookup tables produced in S-Plus.2) Based on the established GAM models, this paper predicted zonal species'distribution under climate change scenarios. In general, our results showed that climate change would cause change in the distribution of endemic species. Following temperature increase, most species shifts to the higher latitude and some of these species shift their ranges out of Yanhe River Catchment.3) Climate change will create opportunities for niche differentiation when empty niches are created at rear edges of range shifts. It will cause niche shift under climate change scenarios. The results showed that the species niche center drift to higher temperature gradient; Species distribution has the same response to climate change in precipitation gradient. But different species responded differently to climate change, Species with restricted ranges are more likely to be sensitive to climate change than widespread species. Concerning the temperature gradient and precipation gradient, the result shows a significant shift in response optimum 3.55℃and 75 mm under climate changes scenarios. Species that encounter a broader array of climatic conditions across their range shows inconspicuous shift in envioroment gradient.4) Compared to the general methods which study the sensitivity of species to climate change, calculated each species'the percentage of range expansion or contraction can immediately detect the responses of species to climate change. Analysis the percentage of range expansion or contraction can reveal the change of species distribution area and calculate species habitat loss and gain. It can detect and accurately predict species distribution changes in order to mitigate impacts on regional species protection or ecological restoration.5) Analyzed the relationship between the species potential distribution area and the percentage of stable suitable habitat and percentage of potentially new suitable habitat, the results showed that the ecology theory that generalist species should have broader tolerances to climate changes than specialist species didn't sound in the Loess Plateau where topography is very important to species distribution. Species distribution ranges can't reflect the sensitivity of species reponse to climate change.