分类： 地球科学 >> 地球科学史 提交时间： 2020-06-22 合作期刊: 《干旱区科学》
摘要： Overgrazing is regarded as one of the key factors of vegetation and soil degradation in the arid and semi-arid regions of Northwest China. Grazing exclusion (GE) is one of the most common pathways used to restore degraded grasslands and to improve their ecosystem services. Nevertheless, there are still significant controversies concerning GE's effects on grassland diversity as well as carbon (C) and nitrogen (N) storage. It remains poorly understood in the arid desert regions, whilst being essential for the sustainable use of grassland resources. To assess the effects of GE on community characteristics and C and N storage of desert plant community in the arid desert regions, we investigated the community structure and plant biomass, as well as C and N storage of plants and soil (0–100 cm depth) in short-term GE (three years) plots and adjacent long-term freely grazing (FG) plots in the areas of sagebrush desert in Northwest China, which are important both for spring-autumn seasonal pasture and for ecological conservation. Our findings indicated that GE was beneficial to the average height, coverage and aboveground biomass (including stems, leaves and inflorescences, and litter) of desert plant community, to the species richness and importance values of subshrubs and perennial herbs, and to the biomass C and N storage of aboveground parts (P<0.05). However, GE was not beneficial to the importance values of annual herbs, root/shoot ratio and total N concentration in the 0–5 and 5–10 cm soil layers (P<0.05). Additionally, the plant density, belowground biomass, and soil organic C concentration and C storage in the 0–100 cm soil layer could not be significantly changed by short-term GE (three years). The results suggest that, although GE was not beneficial for C sequestration in the sagebrush desert ecosystem, it is an effective strategy for improving productivity, diversity, and C and N storage of plants. As a result, GE can be used to rehabilitate degraded grasslands in the arid desert regions of Northwest China.
分类： 地球科学 >> 地质学 提交时间： 2018-03-02 合作期刊: 《古脊椎动物学报》
摘要： Moschus grandaevus was firstly uncovered from the Late Miocene deposits at Ertemte, Olan Chorea, Harr Obo and Hua Ba in or around Huade County in the middle part of Nei Mongol and was described by Schlosser in 1924. The excavations by Sino-Soviet Joint Paleontological Team in 1959 and recent excavations since 2013 at Tuchengzi (Tuchetse), another locality at Huade, accumulated many specimens of the musk deer. The morphology and metric studies show that the musk deer specimens from Tuchengzi are the same as those described by Schlosser and can be included into the same species. M. grandaevus ranges from Siberia of Russia to North China, and likely to southern China, in the Late Miocene and Pliocene. The appearance of such folivorous musk deer in the Late Miocene deposits at Tuchengzi indicates that there were forests there during that period. The cladistic analyses show that the fossil species of Moschus are closely related to each other and can be grouped together as Moschini or Moschinae. Micromeryx is closer to Moschus and Cervidae, but the relationship between Micromeryx and Moschus is more complicated than previously considered; nonetheless Hispanomeryx is closer to Bovidae. Schlosser (1924)记述了最初发现于内蒙古化德境内或附近的二登图、敖兰卓蕾、哈尔敖包及华坝的古麝(Moschus grandaevus)。1959年中苏古生物考察队在化德的另一个地点土城子采集到不少古麝化石。2013年以来作者在土城子进行的野外发掘积累了更多的古麝化石标本。土城子标本在形态和测量数据方面和二登图等地点的古麝非常接近，可以归入同一种。根据现有资料归纳，古麝的地理分布范围自俄罗斯的西伯利亚到华北，很可能延伸到华南；其地质时代分布范围为晚中新世–上新世。食叶型古麝在土城子晚中新世地层中的出现说明当时土城子一带有森林环境。支序分析显示麝属(Moschus)化石种相互之间的系统关系非常近，可以归并为麝族(Moschini)或麝亚科(Moschinae); Micromeryx更接近麝属和鹿科，它与麝属之间的关系比以前认为的复杂，而Hispanomeryx更接近牛科。
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