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51.
利用1981—2018年羌塘自然保护区周边5个气象台站的地表逐日最低温度和平均气温资料,采用线性回归和Mann-Kendall非参数检验方法,分析了近38 a以及全球变暖1.5℃和2℃阈值时羌塘自然保护区地表土壤冻结天数的时空变化特征。结果表明:(1)近38 a近地表土壤冻结开始日期呈推迟趋势,变化率为7.72 d·10 a^-1,冻结终止日期以8.17d·10 a^-1的速率显著提早;冻结持续时间和冻结天数均呈显著缩短趋势,平均每10年分别缩短14.69和11.19 d;同时段内,自然保护区大部分土壤冻结参数的变化率均大于青藏高原。(2)在年代际变化上,自然保护区呈现土壤冻结开始日期推迟、冻结终止日期提前、冻结持续时间和冻结天数缩短的变化特征。(3)土壤冻结参数在21世纪初均发生了气候突变,较青藏高原土壤冻融时间的突变点偏晚。(4)在全球变暖1.5℃时,RCP4.5和RCP8.5情景下的自然保护区土壤冻结参数变化值相同,冻结开始日期推迟25 d,冻结终止日期提早22 d,冻结持续时间和冻结天数分别缩短46和28 d;变暖2.0℃时,RCP4.5和RCP8.5情景下的土壤冻结开始日期推迟35和33 d,冻结终止日期提早30和29 d,冻结持续时间减少64和62 d,冻结天数缩短40和39 d。 相似文献
52.
Martin Pckert Adrien Favre Jan Schnitzler Jochen Martens Yue‐Hua Sun Dieter Thomas Tietze Frank Hailer Ingo Michalak Patrick Strutzenberger 《Ecology and evolution》2020,10(17):9283-9300
Encompassing some of the major hotspots of biodiversity on Earth, large mountain systems have long held the attention of evolutionary biologists. The region of the Qinghai‐Tibet Plateau (QTP) is considered a biogeographic source for multiple colonization events into adjacent areas including the northern Palearctic. The faunal exchange between the QTP and adjacent regions could thus represent a one‐way street (“out of” the QTP). However, immigration into the QTP region has so far received only little attention, despite its potential to shape faunal and floral communities of the QTP. In this study, we investigated centers of origin and dispersal routes between the QTP, its forested margins and adjacent regions for five clades of alpine and montane birds of the passerine superfamily Passeroidea. We performed an ancestral area reconstruction using BioGeoBEARS and inferred a time‐calibrated backbone phylogeny for 279 taxa of Passeroidea. The oldest endemic species of the QTP was dated to the early Miocene (ca. 20 Ma). Several additional QTP endemics evolved in the mid to late Miocene (12–7 Ma). The inferred centers of origin and diversification for some of our target clades matched the “out of Tibet hypothesis’ or the “out of Himalayas hypothesis” for others they matched the “into Tibet hypothesis.” Three radiations included multiple independent Pleistocene colonization events to regions as distant as the Western Palearctic and the Nearctic. We conclude that faunal exchange between the QTP and adjacent regions was bidirectional through time, and the QTP region has thus harbored both centers of diversification and centers of immigration. 相似文献
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Arianna E. C. Ormrod Francis I. Doyle Kirstie J. Lawson Karen E. Hodges 《Ecology and evolution》2021,11(11):6248
Many food webs are affected by bottom‐up nutrient addition, as additional biomass or productivity at a given trophic level can support more consumers. In turn, when prey are abundant, predators may converge on the same diets rather than partitioning food resources. Here, we examine the diets and habitat use of predatory and omnivorous birds in response to biosolids amendment of northern grasslands used as grazing range for cattle in British Columbia, Canada. From an ecosystem management perspective, we test whether dietary convergence occurred and whether birds preferentially used the pastures with biosolids. Biosolids treatments increased Orthoptera densities and our work occurred during a vole (Microtus spp.) population peak, so both types of prey were abundant. American Kestrels (Falco sparverius) consumed both small mammals and Orthoptera. Short‐eared Owls (Asio flammeus) and Long‐eared owls (Asio otus) primarily ate voles (>97% of biomass consumed) as did Northern Harriers (Circus hudsonius, 88% vole biomass). Despite high dietary overlap, these species had minimal spatial overlap, and Short‐eared Owls strongly preferred pastures amended with biosolids. Common Ravens (Corvus corax), Black‐billed Magpies (Pica hudsonia), and American Crows (Corvus brachyrhynchos) consumed Orthoptera, Coleoptera, vegetation, and only a few small mammals; crows avoided pastures with biosolids. Thus, when both insect and mammalian prey were abundant, corvids maintained omnivorous diets, whereas owls and Harriers specialized on voles. Spatial patterns were more complex, as birds were likely responding to prey abundance, vegetation structure, and other birds in this consumer guild. 相似文献
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For marine fish and invertebrates, larval dispersal plays a critical role in determining connections among source and sink habitats, and the lack of a predictive understanding of larval dispersal is a fundamental obstacle to the development of spatially explicit restoration plans for marine populations. We investigated larval dispersal patterns of eastern oyster in an estuary along the Northern Gulf of Mexico under different simulation scenarios of tidal amplitude and phase, river discharge, wind direction, and larval vertical migration, using a coupled biophysical transport model. We focused on the dispersal of larvae released from the commercially exploited (Cedar Point, CP) and non‐exploited (Bon Secour Bay, BSB) oyster populations. We found that high flushing rates through the dominant inlet prevented larval exchange between the commercially exploited and non‐exploited populations, resulting in negligible connectivity between them. Variations in tidal amplitude, river discharge and wind direction played a more important role in the amount of larvae retained in Mobile Bay when they are released from CP than from BSB. Under most of the scenarios, larvae from BSB were retained around the spawning area, while larvae from CP showed a predominant westward flow. Net sinking behavior of late‐stage larvae increased larval retention in the bay, but physical transport showed a higher impact in the amount of larvae retained. These findings have enhanced our understanding of larval dispersal of eastern oyster in a wide, shallow estuarine system, and been used to establish spatially explicit strategies for oyster restoration in the Mobile Bay system, Alabama. 相似文献
58.
Cenozoic bird tracks are known largely from North America, Europe, and the Middle East. There have been no reports of Cenozoic bird tracks from East Asia. This paper describes a series of two trackways produced by a galliform-like or gruiform-like bird from the Oligocene to Early Miocene of Tibet. The tracks are represented by tracings collected from a coal mine in Shigatse, Tibet, during the late 1970s. The tracks are comparable to Ornithoformipes and Pavoformipes and likely represent a medium-sized to large cursorial or flightless bird. In relation to modern bird tracks, the tracks bear a striking resemblance to those produced by the North American Wild Turkey (Meleagris gallopavo) except that M. gallopavo tracks often possess a small, elevated hallux impression. Due to the fact that these are tracings, however, a hallux may have been present and simply have been overlooked. The Shigatse trackways were, unfortunately, lost when the mine was closed and then backfilled during the 1980s, and there is little to no likelihood of recovery. Casts can be catalogued as holotype specimens but tracings cannot; however, all the original tracings have been donated to a public institution by their discoverer, Yimin Wu. 相似文献
59.
于顺利;方伟伟;泽仁旺姆;尼珍;张小凤 《植物研究》2013,33(2):154-158
统计了分布在西藏自治区的被子植物及各生活型果实的类型及比例,并与藏东南地区做了比较。结果如下,西藏自治区果实以蒴果为主(占37.74%),其次为瘦果、坚果、浆果等;干果的比例远远大于肉果;不同生活型的果实类型谱差异较大,乔木中核果的比例最高,藤本中浆果比例最高,灌木中瘦果比例最高,草本中蒴果占优势;4个生活型中,肉果的比例乔木为最高,其次为藤本、灌木、草本。藏东南地区植物的果实类型也以蒴果为主,其次为瘦果、浆果、核果等;藏东南乔木中核果比例最高,藤本中浆果比例最高,灌木和草本植物以蒴果占优势;乔木肉果的比例最高,其次为藤本、灌木、草本。藏东南肉果比例大于全藏区,而干果比例则相反。果实类型的这些性状特征与各自的环境相适应,是植物长期适应自然环境的进化结果,该研究对于理解植物果实对生态环境的长期适应进化具有一定的意义。 相似文献
60.
Impact of Perinatal Photoperiod on the Chronotype of 11- to 18-Year-Olds in Northern European Russia
《Chronobiology international》2013,30(3):305-310
The study investigates the effect of the month of birth and ambient light conditions at birth on sleep length and chronotype among residents of high latitudes. The authors surveyed 1172 persons (609 girls, 563 boys) age 11 to 18 yrs living in five villages and four towns located between 59.5°N and 67.6°N latitude. Survey participation was voluntary and anonymous. Sleep length and chronotype were assessed using the Munich chronotype questionnaire (MCTQ). The study showed the sleep length and chronotype of the children and adolescents depended on sex, age, type of settlement (town/village), and latitude of residence. Latitude exerted a stronger impact on sleep length and chronotype of children and adolescents living in villages than on those of their urban counterparts. Month of birth had no effect on sleep length and chronotype. There was a significant effect of the time of sunrise, sunset, and day length at birth on the chronotype of children and adolescents. A later chronotype was observed in the sample of young persons living above the Arctic Circle who were born during the polar day and polar night. (Author correspondence: borisenkov@physiol. komisc. ru) 相似文献