Effect of burrowing activity of root vole (Microtus oeconomus Pallas) on plant diversity in alpine meadow

Herbivory and burrowing activity of mammals may influence the species composition and diversity of plant communities. The effect of corridors and holes systems constructed by root vole (Microtus oeconomus Pallas) on the plant species diversity was studied in the habitat of high - mountain meadow (3250 in a.s.l in Qinghai-Tibet Plateau, China). By using grid method, these disturbances were studied on 16 plots (100 cm x 100 cm) distributed in 4 transects in studied area, in August 2000 and 2001. The disturbance intensity index, D, was calculated as the percent of the ground surface disturbed by voles in the study area. Plant species were identified and counted on the same plots. In total 46 plant species were identified - 39% of this number was considered as sensitive to the vole disturbances as their occurrence and/or abundance decreased along the disturbance intensity. Generally, a significantly negative correlation (r = - 0.911 P < 0.01) between vole aboveground disturbances and plant species diversity (H') was found. The results suggest that root vole ground disturbances, especially in the form of actively utilized holes and corridors have significantly negative influence on plant species diversity in high-mountain grassland habitat.

Analysis of diets of upland buzzards using stable carbon and nitrogen isotopes

We measured the stable carbon and nitrogen isotope ratios for muscles of the upland buzzards (Buteo hemilasius) and their potential food sources, plateau pikas (Ochotona curzoniae), Qinghai voles (Lasiopodomys fuscus), plateau zokors (Myospalax fontanierii), and several passerine bird species at the alpine meadow in Maduo county, Guoluo prefecture of Qinghai province, People's Republic of China, to provide diet information of upland buzzards, highlighting different diet composition of upland buzzards exposed to different locations. The results demonstrated that stable carbon isotope ratios of upland buzzards, passerine birds, plateau pikas, plateau zokors, and Qinghai voles were -24.42 +/- 0.25parts per thousand, -22.89 +/- 1.48parts per thousand, -25.30 +/- 1.47parts per thousand, -25.78 +/- 0.22parts per thousand, and -25.41 +/- 0.01parts per thousand, respectively, and stable nitrogen isotope ratios were 7.89 +/- 0.38parts per thousand, 8.37 +/- 2.05parts per thousand, 5.83 +/- 1.10parts per thousand, 5.23 +/- 0.34parts per thousand, and 8.86 +/- 0.06parts per thousand, respectively. Fractionation of stable carbon and nitrogen isotope ratios between upland buzzards and their food were 1.03parts per thousand and 2.11parts per thousand, respectively. Based on mass balance principle of stable isotopes and the Euclidean distance mixing model, upland buzzards depended mainly on plateau pikas as food (74.56%). Plateau zokors, Qinghai voles, and passerine birds only contributed a small proportion (25.44%) to diets of upland buzzards. The results were closely accordant with analyses of stomach contents and food pellets, which firmly supported the feasibility of using stable carbon and nitrogen isotope ratios to investigate diet information of upland buzzards. Another study based on stable carbon isotopes showed that upland buzzards living in the Haibei prefecture (another prefecture located in the southeast Qinghai province) mainly preyed on passerine birds (64.96% or more) as food supply. We were alarmed by the preliminary results that widespread poisoning activities of small mammals could reshape the food composition of upland buzzards, influencing the stability and sustainability of the alpine meadow. Bio-control on rodent pests should be carried out rather than the chemical measures.

Burrowing rodents as ecosystem engineers: the ecology and management of plateau zokors Myospalax fontanierii in alpine meadow ecosystems on the Tibetan Plateau

1. Plateau zokors, Myospalax fontanierii, are the only subterranean herbivores on the Tibetan plateau of China. Although the population biology of plateau zokors has been studied for many years, the interactions between zokors and plants, especially for the maintenance and structure of ecological communities, have been poorly recognized. In the past, plateau zokors have been traditionally viewed as pests, competitors with cattle, and agents of soil erosion, thus eradication programmes have been carried out by local governments and farmers. Zokors are also widely and heavily exploited for their use in traditional Chinese medicine.2. Like other fossorial animals, such as pocket gophers Geomys spp. and prairie dogs Cynomys spp. in similar ecosystems, zokors may act to increase local environmental heterogeneity at the landscape level, aid in the formation, aeration and mixing of soil, and enhance infiltration of water into the soil thus curtailing erosion. The changes that zokors cause in the physical environment, vegetation and soil clearly affect the herbivore food web. Equally, plateau zokors also provide a significant food source for many avian and mammalian predators on the plateau. Zokor control leading to depletion of prey and secondary poisoning may therefore present problems for populations of numerous other animals.3. We highlight the important role plateau zokors play in the Tibetan plateau ecosystem. Plateau zokors should be managed in concert with other comprehensive rangeland treatments to ensure the ecological equilibrium and preservation of native biodiversity, as well as the long-term sustainable use of pastureland by domestic livestock.

碳、氧稳定同位素分析在古环境研究中的应用

A number of proxy records of paleoenvironment using stable isotopes could show the history of past environmental changes. These archives include peat and lake sediments, loess-paleosot sequence, fossil mammals and stalagmite, and so on. The stable isotopic composition of carbonate and organic matter and frequency magnetic susceptibility from Tianshuigou and Yuanlei loess-palesol sequence can be used to give estimates of the paleoenvironmental history of Dali, and even of the whole Chinese Loess Plateau during the last 250ka. Features of the High Temperature and Large Precipitation Event in the Tibet Plateau and its adjacent area during 40~30kaBP had been studied by Professor Shi Y. In this dissertation, its impact on Chinese Loess Plateau has been discussed again. Carbon and oxygen isotopic ratios, magnetic susceptibility and frequency magnetic susceptibility in Tianshuigou and Yuanlei profiles show that the Event in this area is not so stronger as the Tibet Plateau. The carbon isotopic composition of organic matter in Tianshuigou, Yuanlei, dingcun and Jingcun loess-palesol sequences are indicative of major changes in the paleovagetation between terrace and plain of the Chinese Loess Plateau. Water is one of the most important factors adjusting the relative biomass of C4 plant in terrestrial ecosystems. Stable carbon isotope ratio of vertebrate tooth enamel is used increasingly to reconstruct environmental and ecological information modern and ancient ecosystems. The SI3C value of tooth enamel bioapatites can distinguish between browsers and grazers. Data from typical grassland of Inter Mongolia, the Alpine meadow of Qinghai-Tibet Plateau and the Yaluzangbu Great Canyon indicate that diets of mammals could record the relative biomass of C4 plant only in the C4 dominated ecosystem. In a C3 dominated ecosystem, diet of mammals would include more C3 plants than vegetation. According to Professor Cerling, proxy records from North and South America, Africa and Pakistan show that at the end of the Miocene (between 8Ma to 6 Ma) there was a global expansion of CA biomass, probably when atmospheric CO2 levels declined. Thus, "C4 world" and "CO2 starvation" are put forward. In this dissertation, carbon isotopes of fossil tooth such as Equus sanmeniensis and Hipparion chiai from Linxia, China reveal that there is a C3 dominated ecosystem in the late Miocene. Diets of ancient mammals in Linxia are not evidence of global expansion of C4 biomass.