Abstract：
In general, dietary habits of pastoralists are livestock-derived, but are also influenced by external food sources under globalization. We hypothesized that dietary habits of pastoralists would be influenced by their remoteness, and that changes from the traditional diet would result in deviations in the local ecological chain. To test this hypothesis, we determined the δ13C and δ15N values of soil, plants, and hair of animals and pastoralists (n = 885). The δ13C value in human hair reflects the proportions of protein originating from C3 and C4 plants; whereas, the δ15N value reflects the proportions of protein derived from plants and animals, with higher values indicating a greater consumption of meat. The isotopic signatures enabled us to estimate the variation in dietary habits of pastoralists across a socio-economic gradient of easily accessible to remote areas on the Tibetan plateau, and to determine the trophic transfer of the isotopes along an ecological chain. The trophic magnification factor (TMF) evaluated the trophic transfer of δ15N in the soil-plants-animals-pastoralists ecological chain. The high δ15N values in soil and plants were not recovered in animals and pastoralists in easily accessible and developed areas, indicating the use of external feed and food resources, and that they deviated from the ecological chain. The mean δ13C (-22.0 ‰) and δ15N values (6.9 ‰) of pastoralists indicated diets consisting mainly of local C3 plants and animal products. However, pastoralists in remote areas relied more on meat protein and on the local ecological chain than pastoralists in easily accessible areas, as their δ15N values and trophic magnification factor of δ15N in the ecological chain were greater. In addition to remoteness, per capita GDP influenced dietary changes in pastoralists, with richer pastoralists consuming more external food. We concluded that dietary changes of pastoralists in the easily accessible areas were due to external food resources and alterations in the local ecological chain of animals and plant-based foods available to the pastoralists.
摘要：
总的来说,牧民的饮食习惯源于牲畜，但也受到全球化下外部食物来源的影响。我们假设牧民的饮食习惯会受到他们偏远的影响，传统饮食的改变将导致当地生态链的偏差。为了检验这个假设，我们确定了土壤的δ13C和δ15N值，植物,动物和牧民的毛发（n=885）。人发中的δ13C值反映了源自C3和C4植物的蛋白质的比例；然而，δ15N值反映了来自植物和动物的蛋白质的比例，较高的值表示更多的肉类消费。同位素特征使我们能够估计在青藏高原偏远地区容易到达的社会经济梯度上，牧民的饮食习惯的变化，并确定同位素沿生态链的营养转移。营养放大因子（TMF）评估了土壤-植物-动物-牧民生态链中δ15N的营养转移。在容易到达和发达地区的动物和牧民中，土壤和植物中的高δ15N值没有恢复，表明外部饲料和食物资源的使用，他们偏离了生态链。牧民的平均δ13C（-22.0‰）和δ15N值（6.9‰）表明饮食主要由当地C3植物和动物产品组成。然而,偏远地区的牧民比容易到达的地区的牧民更依赖肉类蛋白质和当地的生态链，因为它们在生态链中的δ15N值和δ15N的营养放大因子更大。除了遥远，人均GDP影响了牧民的饮食变化，更富有的牧民消费更多的外部食物。我们得出的结论是，在容易到达的地区，牧民的饮食变化是由于外部食物资源以及牧民可获得的当地动植物食品生态链的变化。
