Abstract: Carbon and nitrogen stable isotope ratios were used to analyze animals’ trophic level and the contribution rates of organic carbon source in light zone of Zhijin cave, Guizhou. The results showed that the δ¹³C of plants ranged from (-43.46±0.06)‰ to (-37.54±0.03)‰, and δ¹⁵N ranged from (0.71±0.01)‰ to (2.38±0.00)‰. The mean of δ¹³C of soil organic matter (SOM) was （-24.99±0.01）‰, which showed that the contribution of the plants to SOM was small. δ¹⁵N of SOM in the light zone was (3.93±0.03)‰, being lower than that of SOM out the cave. The contribution of 6 kinds of organic carbon source to the food sources of cave animals was calculated using IsoSource, and the results showed that the mean rate of contribution of soil organic matter to cave animals (except for the food sources of Tipula sp. and Sypna sp.) was more than 60%, being higher than those from the plants, indicating that soil organic matter was the main food source of cave ecosystem. According to the calculation formula of trophic level, the ecosystem was composed of 3 trophic levels. Soil organic matter was the first trophic level, followed by Diestrammena sp., Pocellio scaber, Camberlinius sp., Bradybaena strictotaenia, Phalangiidae sp., Hahnia sp. Drosophila sp., Uenotrechus sp. and most of spider groups were the third trophic level.

Key words: wetland soil, Spartina alterniflora, aquaculture pond., dissolved inorganic carbon