The Analysis Of The Stable Carbon And Nitrogen Isotopes In The Process Of Soil- Grass-Livestock-human Material Circulation On Qinghai-tibet Plateau Alpine Pastoral Area

Isotope stability is isotope, which refers to the nucleus is stable, which does not spontaneously undergo radioactive decay or nuclear fission. It is a kind of isotope that does not have radioactive in nature. Due to the different natural environment and other factors in the ecological system, the different stable isotope abundance values can reflect the composition characteristics of the elements and the flow characteristics between the different ecology components.The Qinghai Tibet Plateau is known as the third pole of the earth, the environment is harsh, ecosystem is simple and fragile. Special geographical and climatic characteristics make the ecological system of the Qinghai Tibet Plateau have the characteristics of fragile and vulnerable to damage and difficult to recover after the destruction. Nitrogen is one of the important nutrient elements in the ecosystem,and it is one of the essential nutrition elements in the process of biology growth and development. And carbon cycle is one of the most important and basic components of the materials circulation in nature. Therefore, it is very important to study the flow and transformation characteristics of carbon and nitrogen in grassland ecosystem on Qinghai Tibet Plateau.We selected 5 different altitude height areas in Qinghai Tibet Plateau; we choose the pasture soils, edible grass, yak tail hair, Tibetan ship wool and herdsmen’ hair as our research objects; measured stable carbon and nitrogen isotope δ¹³C, δ¹⁵N value,total carbon and total nitrogen content in these samples; aimed to: 1. Analysis the stable carbon and nitrogen isotope 13 C, 15 N values in each component of Qinghai Tibet Plateau grassland ecosystem; 2. Try to analyze the characteristics of stable carbon and nitrogen isotope transformation and enrichment in the process of soil-grass-animal fur tissue- hair substances flow between the various components of Qinghai Tibet Plateau grassland ecosystem. Through the processing, measure and analysis of the data, we draw the following conclusions:1. The distribution of organic carbon content in five sampling areas of 81 soil samples was in the range of 2.53¹3.26g/kg, the total average value was 6.161g/kg;δ¹³C value range within-28.03 ‰ ^-18.55 ‰, average value was-25.29 ‰, both overall showed significant negative correlation（P < 0.05）. The distribution of total nitrogen content is in the range of 1.18⁰.21g/kg, the total average value was0.54g/kg; δ¹⁵N value range in the range of 9.33 ‰ ².30 ‰, average value was5.82 ‰, both overall showed no significant negative correlation.2. The total carbon content of 85 herbage samples in five sampling areas was in range of 52.21²6.42g/kg, average value was 42.30g/kg; δ¹³C value in the range of-29.62 ‰ ^-24.96 ‰, average value was-27.36 ‰; total carbon content in forage samples and δ¹³C values had no significant correlation（P > 0.05）. The distribution of total nitrogen content was 4.73¹.23g/kg, the total average value was 2.42g/kg; δ¹⁵N value in the range of 8.39‰^-2.52‰, average value was 2.87%. Both overall showed very significant positive correlation（P < 0.01）. The δ¹³C value of total 315 yak tail hair samples from five sampling areas was in the range of-21.32‰^-25.05‰. δ¹³C value’s average was-23.64‰, samples had the uniform distribution; δ¹⁵N values in the range of 7.92‰².21 ‰, average value was 4.22‰.3. The δ¹³C values of 258 Tibetan sheep wool samples from five sampling areas was in the range of-20.02‰ ^-24.75 ‰, δ¹³C average value was-23.30 ‰, samples had the uniform distribution; δ¹⁵N values in the range of 8.02 ‰ ².39‰, δ¹⁵N average value was4.64‰. The δ¹⁵N values of Tibet wool samples did not exist significant differences mutual in the five regions.4. Eating grass in the same grassland area, Tibetan sheep wool tissue enrich more stable carbon and nitrogen isotopes than yak tail hair, namely δ¹³C value of sheep >δ¹³C value of yak, δ¹⁵N value of sheep > δ¹⁵N value of yak.5. The two factors（one was the interaction of age and area, the other was age） had little influence on the stable carbon and nitrogen isotope abundance in Yak tail hair and Tibetan sheep wool. The difference altitude between the regions was the main factor that caused the significant differences of the stable carbon and nitrogen isotope abundance in Yak tail hair or Tibetan sheep wool.6. The δ¹³C value of 146 hair samples from five regions was in range of-20.18‰^-24.19‰, δ¹³C average values was-21.87 ‰; δ¹⁵N values in range of8.97‰².95‰, δ¹⁵N average values was7.02 ‰. Gender and regional were the two indicators that made significantly effects on δ¹³C value of herdsmen’ hair samples（P<0.05）.7. In the ecosystem of Tibetan Plateau, the stable carbon isotope enrichment factor from forage samples to livestock fur samples was in range of 3.5‰-4.5‰; the enrichment factor from livestock fur samples to herdsmen’ hair samples was in range of 1.0‰-2.0‰; the stable nitrogen isotope enrichment factor from soil samples to forage samples was about 2.281‰; the stable nitrogen isotope enrichment factor from forage samples to livestock fur samples was in the range of 0.5‰-1.0‰; the factor from livestock fur samples to herdsmen’ hair samples was about 2.3‰.