Effects of check dam on species assemblage and distribution of amphibian and reptile in a deciduous forest in Nan Province, Thailand

Since numerous check dams have been constructed in Thailand and there were only a few reports on their effects on biotic components, a systematic field research on assemblage and distribution of amphibian and reptile was carried out to monitor the check dam effects in this study. Effects of the check dam were determined based on 1) spatial comparison between check dam and non-check dam areas during the same period and 2) temporal comparison between pre- and post-check dam periods of the same study site. Ten replicates of 5 transects at stream and terrestrial habitats were used for animal survey in two ephemeral streams at the Chulalongkorn University Forest and Research Station, Nan Province. The surveys in every transect were conducted in both daytime and nighttime on monthly basis for 2 years during April 2009 to April 2011. It was found that physical factors related to water pattern including hydroperiod, water depth and number of water body were significantly increased in check dam conditions in both spatial and temporal comparisons, indicating that the check dam could prolong the water availability of the stream. However, the rarefaction curves indicated that species diversity of amphibian and reptile was not significantly different between check dam and non-check dam conditions in both spatial and temporal comparisons. The non-metric multidimensional (NMDS) plots and analysis of similarity (ANOSIM) results also indicated that species composition of amphibian and reptile was generally similar between check dam and non-check dam conditions in both stream and terrestrial habitats. Although the distribution patterns, as revealed by Kruskal-Wallis test and non-parametric Tukey type multiple comparison, of some amphibians and reptiles were altered in a presence of the check dam, the distribution patterns of the majority of amphibian and reptile species were not different as a result of the check dam in both comparisons. Overall results suggested that the check dam can be regarded as an effective measure to prolong water period with minimal short-term impact on herptile community in the ephemeral stream habitat in the successive forest.