食物资源的枯竭对丹顶鹤营养位的影响

Characterization of trophic position of red-crowned crane (Grus japonensis) influenced by the food resource exhausting

随着扎龙湿地生物资源的迅速减少,在该地栖息的丹顶鹤种群的营养关系可能发生显著的变化.本文使用稳定同位素(δ^(15)N和δ^(13)C)监测食物资源的枯竭对丹顶鹤营养位的影响.结果表明:丹顶鹤种群的δ^(15)N和δ^(13)C的丰度范围分别为6.9‰~8.1‰和-17.8‰^-18.5‰.扎龙湿地系统以大型水禽为食物顶端的食物链长度为3.8±0.2,其中丹顶鹤种群所处的平均营养位为3.1(范围在2.9~3.3).丹顶鹤的δ^(15)N的丰度近年波动范围为7.4‰~8.8‰(波动幅度1.4,小于营养位发生显著变化的阈值3.4),这说明在该地区活动的丹顶鹤的营养位并没有随着大面积的栖息地和食物资源的消失而发生显著变化.然而,随着本地区生物资源的枯竭,丹顶鹤种群规模迅速减少,当前必须合理解决当地居民从湿地获取生活资源的需求与丹顶鹤觅食之间的矛盾,从而更好地保护这种濒危种群.

The trophic relations of the red-crowned crane species in Zhalong Wetland, northeastern China may change significantly with rapid decrease of biological resources. In this paper, the influ- ence of food resource exhausting on the trophic levels of this vulnerable species was determined by using stable isotope （δ13C and δ15N） methods. The results indicated that the mass of δ13C and δ15N in the red-crowned cranes were in the range of -17.8‰ to -18.5‰ and 6.9%0 to 8.1‰, respectively. The dominant food chain length of large water fowls in the ecosystem of Zhalong Wet- land was 3.8±0.2 in average, of which the examined species, i.e., red-crowned cranes were 3.1 in average, with the range of 2.9 to 3.3. The annual fluctuation range of δ15N values in the red- crowned cranes was from 7.4%0 to 8.8%0 （ with the gap of approximately 1.4, which was below the threshold 3.4 that was considered as a trophic level significant change in an ecosystem） , indicating the trophic level of this vulnerable species did not change significantly with the losses of large area of their habitats and foods. Nevertheless, the rapid decrease of the target species population with the food resource exhausting indicated that the conflict of food demand of the red-crowned cranes versus resource need of local residents should be resolved for better protecting this extinguishable species.