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1 Polish Journal of Ecology

1 2011

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Effect of road on the distribution of amphibians in wetland area - test with model-averaged prediction

Dai Q., Wang Y.

Polish Journal of Ecology

2011

Vol. 59, nr 4

813-821

We studied the effects of roads on presence of Plateau brown frogs (Rana kukunoris Nikolsky, 1918) and Tibetan frogs (Nanorana pleskei Gunther, 1896) in temporary pools of Sedges dominated wetland area in eastern Qinghai-Tibetan Plateau. The road is seven meter-wide, asphalt-paved with daily traffic rate about 400 vehicles. The temporary pools hold water only in summer with surface area of about 2 m2. We used logistic regression models, a theoretic information approach, and model averaging to test the effects of distance from road and depth, area and pH of pools on distribution of frogs in terms of presence/absence in 180 small pools located at 10 to 150 m from the road edge. Observed data showed that presence probabilities of both species declined in the vicinity of roads, starting at approximately 100 m away from the road edge. Model averaging based on AICc ([Sigma Omega i] = 95% confidence) indicated that both distance from road edge and its quadratic term were important predictors for explaining presence of both amphibians. Model-averaged prediction based on 95% confidence model set also revealed non-monotonic increasing curve relationships between presence probability of both amphibians and distance from road edge, even when other habitat variables were held constant. These results indicated that the road-effect zone for both amphibians extended 100 m on side of the wetland roads along which we sampled. Additionally, the results showed that water depth and water pH of pools positively influenced presence of Tibetan frogs and had highest contribution to the models. In contrast, water depth influenced presence of Plateau brown frogs negatively. It was indicated that environmental variables influence the presence of the two species of amphibians in different ways.