2000-2017年新疆天山植被水分利用效率时空特征及其与气候因子关系分析

水分利用效率(WUE)是衡量生态系统碳水循环耦合程度的重要指标, 估算新疆天山及南北主要绿洲的植被WUE并分析其时空变化规律, 探索其影响因素, 对该区域生态系统保护、农业水资源的合理利用与开发等方面具有重要的意义。基于MODIS遥感数据、气象数据和土地利用类型数据, 分析新疆天山近18年植被WUE时空变化特征以及与气候因子的关系。结果表明: (1) 2000-2017年新疆天山植被WUE变化范围为0.84-1.34 g·mm ^-1·m ^-2, 多年均值为1.11 g·mm ^-1·m ^-2, 整体呈减少趋势, 变化率为-0.014 1 g·mm ^-1·m ^-2·a ^-1; 空间分布具有较强的垂直地带性规律, 1 000 m以上的区域随着海拔的升高而减少。(2)植被WUE年内变化呈单峰型变化格局, 具有明显的季节性差异, 表现为: 夏季>春季>秋季>冬季。(3)相关分析和统计结果表明, 新疆天山植被WUE时空变化受到气温影响的区域占33.23%, 受降水影响的区域占8.57%, 受气温和降水综合强影响的区域占5.63%, 气温和降水综合弱影响的区域占13.13%; 因此气候因素中气温在新疆天山植被WUE的变化中起到主导作用。(4)水田与旱地水分利用效率随着时间变化呈持续减少趋势, 并且这些区域基本上受到非气候因子的影响, 说明当地人类活动存在不合理性。     

大小兴安岭可培养细菌的资源多样性

细菌作为微生物中的重要组成部分, 在有机质的形成与分解、维持生态系统平衡、促进动植物发育等多方面都有着重要作用。2014-2017年, 我们采用常见培养基分离纯培养法及16S rRNA基因序列分析方法对大小兴安岭地区土壤可培养细菌的群落结构和多样性进行了调查研究。结果表明: 从大小兴安岭地区的17个自然保护区内不同生境的土壤中分离获得3,180个菌株, 隶属于24属120种。其中, 芽孢杆菌属(Bacillus)的种数和株数最多, 分别为38种和2,419株, 是大小兴安岭地区可培养细菌的绝对优势类群(占总株数的76.1%); 其次是短杆菌属(Brevibacterium)(13.0%)。大兴安岭地区的物种数、Simpson多样性指数和Shannon-Wiener指数高于小兴安岭地区。优势类群芽孢杆菌属的枯草芽孢杆菌(B. subtilis)、苏云金芽孢杆菌(B. thuringiensis)、巨大芽孢杆菌(B. megaterium)等有重要的生产及科学研究价值。     

不同海拔温度和降水对新疆阿尔泰山西伯利亚落叶松径向生长的影响

为定量并分离关键气候因子对新疆阿尔泰山不同海拔树木径向生长的影响,通过对高、中和低海拔的西伯利亚落叶松(Larixsibirica)树轮宽度标准年表与气候因子分别进行相关、多元线性回归等统计分析,并进一步计算了线性模型中不同气候因素的绝对和相对贡献率。结果表明,高海拔地区,当年6月温度和上年7月降水分别与径向生长呈显著正相关和负相关,两者共同解释西伯利亚落叶松径向生长变异的33.1%,相对贡献率分别为66.2%和33.8%;中海拔地区,当年6月温度和上年6月降水分别与径向生长呈显著正相关和负相关,两者共同解释径向生长变异的26.8%,相对贡献率分别为40.1%和59.9%;低海拔地区,上年6月温度和7月降水分别与径向生长呈显著负相关和正相关,两者共同解释径向生长变异的29.4%,相对贡献率分别为31.9%和68.1%。这表明限制树木径向生长的主要影响因子随海拔的不同而异,在高海拔地区,温度是主要限制因子;而在低海拔地区,降雨是主要限制因子。     

Phylogeography suggest the Yili Valley being the glacial refuge of the genus Ixiolirion (Amaryllidaceae) in China

The Pleistocene climatic oscillations had profound effects on the demographic history and genetic diversification of plants in arid north-west China where some glacial refugia have been recognized. The genus Ixiolirion comprises three species, of which two, I. tataricum and I. songaricum (endemic), occur in China. In some locations they are sympatric. We investigated their population structure and population history in response to past climatic change using a sample of 619 individuals in 34 populations with nITS and ptDNA sequences. A significant genetic divergence between the two species was supported by a high level of pairwise genetic differentiation, very low gene flow, and phylogenetic analysis showing that I. songaricum haplotypes were monophyletic, whereas those of I. tataricum were polyphyletic. We found significant differentiation and phylogeographic structure in both species. The split of the two species was dated to the late Miocene (～7?Ma), but deep divergence occurred in the mid-late Quaternary. A similar haplotype distribution pattern was found in both species: one to two dominant haplotypes across most populations, with unique haplotypes in a few populations or a geographic group. The genetic diversity, haplotype number, and haplotype diversity decreased from the Yili Valley to the central Tianshan and Barluk Mountains. Additionally, ptDNA analysis showed that I. tataricum diversified in the eastern Tianshan and Barluk Mountains, which might be due to physical barriers to long distance seed dispersal such as desert. In conclusion, our results indicated that the Yili Valley was likely a glacial refuge for Ixiolirion in China, with postglacial dispersal from the Yili Valley eastward to the eastern Tianshan Mountains, and northward to the Barluk Mountains. The climatic changes in the Miocene and Pleistocene and geographic barriers are important factors driving species divergence and differentiation of Ixiolirion and other taxa.     

天山一号冰川表面冰尘和底部沉积层中可培养酵母菌系统发育类群的分布及生态生理特征

【目的】揭示乌鲁木齐河源天山1号冰川表面冰尘(CS)和底部沉积层(DS)可培养酵母菌系统发育类群及其结构组成差异,分析低温酵母菌代表菌株之间的生态、生理生化特性。【方法】利用4种培养基分离天山1号冰川可培养酵母菌,采用ITS基因序列分析确定菌种的系统进化地位。对分离菌株的最适生长温度、耐盐性和产酶等生态、生理学特性进行分析。【结果】从冰尘和底部沉积层中共分离出152株酵母菌菌株,通过ITSrRNA基因序列的NCBI比对和Rep-PCR指纹分型,结果表明酵母菌类群包括担子菌门(Basidiomycota)和子囊菌(Ascomycota),分属于14个属26种,其中担子菌门柄锈菌亚门(Pucciniomycotina)88株、伞菌亚门(Agariomycotina)24株,子囊菌门40株,冰川广布酵母菌Vishniacozyma victoriae为优势菌株(占比21.84%)。17种酵母的最适生长温度为15°C、2种为10°C、6种为20°C。25株代表酵母菌株产酶分析显示,产脂肪酶、淀粉酶、蛋白酶菌株分别为11株、11株、5株,6株3种酶都不产。【结论】天山1号冰川冰尘及底部沉积层可培养低温酵母系统发育类群结构存在差异,产低温酶活性高、稳定性好,为今后冰川低温酵母菌的研究提供有价值的数据支持。     

秦岭大熊猫冬春季节对巴山木竹竹林生长指标的选择

2004~2005年冬季的12月、1月和春季的4月、5月,在秦岭山系南坡佛坪自然保护区内就大熊猫对构成其主要栖息地和食物来源的巴山木竹竹林的选择进行研究后的结果表明:在冬季,大熊猫栖息地多为幼竹与死竹比例基本持平、密度稳定的巴山木竹竹林,主要取食老竹;在春季,大熊猫更偏好选择竹子密度和盖度略低、竹子粗壮高大、幼竹与竹笋比例高的竹林活动,主要取食幼竹。大熊猫春季栖息地幼竹比例通常高过死竹比例,竹林密度处于增长期。竹林进入发笋期后,稀疏、高大的竹林下的粗大竹笋成为大熊猫的主要食物来源。     

Initial Trends of Bird Assemblages Before and After River Diversion in an Endemic-rich African Forest

The Lower Kihansi Hydropower Project in southern Tanzania caused the diversion of the Kihansi River from the Kihansi Gorge in the year 2000. By sampling the understorey avifauna prior to diversion, we examined (i) whether the adjacent Udagaje Gorge was an adequate control for observations in the Kihansi Gorge; (ii) which species of conservation interest occurred; and, (iii) which season best suited annual monitoring. Species composition and capture rates at three and two elevational transects in the Kihansi Gorge and Udagaje Gorge, respectively, confirmed that Udagaje had a comparable avifaunal assemblage to Kihansi. The cold season was most appropriate for population monitoring because >2 times more individuals were captured in the cold than hot season at both gorges, and at least four altitudinal migrants were present in the cold but not hot season. Post-diversion sampling revealed that only the Upper Kihansi transect suffered a significant decrease in number of individuals, a result that was driven largely by a decline in the Little Greenbul, Andropadus virens. This transect is closest to the Kihansi waterfall and associated spray zone which were lost after river diversion. Lack of differences in bird communities at other transects after diversion illustrates that early post-diversion effects on birds are probably concentrated near the base of the main falls. Together with studies of other biota in Kihansi, we propose that long-term monitoring is necessary to understand the factors that regulate changes in species composition of this threatened forest site.     

秦岭山区中国大鲵生境因子的选择

通过对秦岭山区中国大鲵(Andrias davidianus)栖息地生境因子调查、统计,利用R语言分析了各因子与大鲵生境选择的相关性,得出研究结果:秦岭山区影响大鲵生存的主要因子为栖息地类型(相关系数r=0.98),其次是水温(相关系数r=-0.8)、河岸坡度(r=-0.6)和p H (r=-0.6);浊度(相关系数r=0.5)、电导率(r=0.49)、DO(r=0.4)、人为干扰(r=0.35)和海拔(r=0.31)对大鲵分布影响不大。研究结果为探讨中国大鲵对野生环境的适应性选择提供了参考。     

Is dietary or microhabitat specialization associated with environmental heterogeneity in horned lizards (Phrynosoma)?

Niche breadth is predicted to correlate with environmental heterogeneity, such that generalists will evolve in heterogeneous environments and specialists will evolve in environments that vary less over space and time. We tested the hypothesis that lizards in a heterogeneous environment were generalists compared to lizards in a homogeneous environment. We compared niche breadths of greater short‐horned lizards by quantifying resource selection in terms of two different niche axes, diet (prey items and trophic level), and microhabitat (ground cover and shade cover) between two populations occurring at different elevations. We assessed the heterogeneity of dietary and microhabitat resources within each population's environment by quantifying the availability of prey items, ground cover, and shade cover in each environment. Overall, our results demonstrate that despite differences in resource heterogeneity between elevations, resource selection did not consistently differ between populations. Moreover, environmental heterogeneity was not associated with generalization of resource use. The low‐elevation site had a broader range of available prey items, yet lizards at the high‐elevation site demonstrated more generalization in diet. In contrast, the high‐elevation site had a broader range of available microhabitats, but the lizard populations at both sites were similarly generalized for shade cover selection and were similarly specialized for ground cover selection. Our results demonstrate that environmental heterogeneity of a particular resource does not necessarily predict the degree to which organisms specialize on that resource.     

秦岭汉江流域新发现旧石器遗址的地层与释光年代

汉江流域旧石器时代文化遗存丰富,南方砾石石器工业和北方小石片石器工业类型的遗存并存,对研究中国南北旧石器文化交流和发展演化具有重要的意义。2016-2018年夏天,我们在汉江流域进行野外调查,新发现十个含更新世晚期旧石器遗存的地点,利用热转移光释光（TT-OSL）方法对各遗址的地层进行了测年。测年结果表明,这几处旧石器地点的古人类活动主要发生在距今20-5万年之间,涵盖了L₂、S₁和L₁三个阶段,与之前汉江流域第二级阶地发现的旧石器遗址年代基本一致。新发现的十个旧石器地点丰富了汉水流域旧石器遗存,为进一步研究该区域古人类旧石器遗址年代学和石器技术提供了新的材料。