青藏铁路沿线温性草原区芨芨草(Achnatherum splendens)群落特征

芨芨草群落是青藏铁路沿线一类重要的温性草原植被类型,对青藏铁路两侧及其四周的水土保持起着非常重要的作用。对青藏铁路西格段海晏县附近的芨芨草草原的空间分布特征、物种丰富度和生物量等特征进行了分析。结果显示,研究地区芨芨草群落由芨芨草斑块和针茅斑块镶嵌而成,两类斑块的数量、大小和斑块间大小变化幅度等特征在空间上表现出一定的规律;芨芨草斑块大小在样线上所占的比例比针茅斑块为小,且有随远离铁路而减小的趋势,而物种丰富度则出现相反的变化趋势;芨芨草斑块的盖度和单位面积上地上生物量显著高于针茅斑块。斑块的大小和数量在一定程度上反应了芨芨草群落的退化状况。人为活动往往会加剧芨芨草群落的斑块片段化。针对芨芨草群落的特征和现状,建议加强对这些区域内人为活动的限制力度以减少对芨芨草群落的干扰。     

ISSR analysis of genetic diversity of the Qinghai-Tibet Plateau endemic Rhodiola chrysanthemifolia (Crassulaceae)

Inter-simple sequence repeat markers (ISSR) were used to estimate genetic diversity within and among 10 populations of Rhodiola chrysanthemifolia along Nianqingtangula Mountains and Brahmaputra, a species endemic to the Qinghai-Tibet Plateau and an endangered medicinal plant. Of the 100 primers screened, 13 produced highly polymorphic DNA fragments. Using these primers, 116 discernible DNA fragments were generated of which 104 (89.7%) were polymorphic, indicating substantial genetic diversity at the species level. Genetic diversity measured by the percentage of polymorphic bands (PPB) at the population level ranged from 21.97% to 48.8%. Analysis of molecular variance (AMOVA) showed that the genetic variation was found mainly among populations (77.3%), but no regional differentiation was discernible. Variance within populations was only 22.7%. The main factor responsible for this high level of differentiation among populations is probably the historical geographical and genetic isolation of populations in a harsh mountainous environment. Concerning the management of R. chrysanthemifolia, the high genetic differentiation of populations indicates the necessity of conserving the maximum possible number of populations.     

青藏高原药用植物唐古特山莨菪和唐古特大黄光合作用对强光的响应

与唐古特大黄相比,唐古特山莨菪的表观光合量子效率(AQY)较高,但最大净光合速率(Pmax)较低。在光强小于1200μmolm-2s-1时,后者用于碳同化的电子传递占总光合电子传递的比例(JC/JF)比前者高,而分配于光呼吸的电子传递(JO/JF)及Rubisco氧化和羧化速率的比值(VO/VC)则相反;光强大于1200μmolm-2s-1以后两种植物的这些参数都趋向稳定。随光强增加,后者叶片吸收光能分配于热耗散(D)的增加斜率较前者高,表明两高山植物对强辐射的适应方式略有不同。加强光呼吸途径的耗能代谢和PSII天线热耗散份额是唐古特山莨菪适应高原强辐射的主要方式,而提高叶片光合能力则是唐古特大黄的一种适应方式。     

青藏高原生态系统服务功能的价值评估

青藏高原具有丰富多样的生态系统类型 ,这些生态系统不仅生产了大量的产品 ,而且提供了巨大的生态服务功能。根据计算表明 ,高原生态系统 2 0 0 0年生产的产品经济价值为 170× 10 8元。生态服务功能中年固碳总量为 15× 10 8t,释放氧气量为11× 10 8t。根据二氧化碳固定量和氧气释放量估算的调节大气的服务价值总计为 10 0 15× 10 8元。以高寒草甸和高寒草原为主的草地生态系统具有重要的水源涵养功能 ,每年高原生态系统的水源涵养量达 2 6 12× 10 8m3,其经济价值为 174 4× 10 8元。森林的净化功能价值大约为 2 5 5× 10 8元。高原生态系统产品的经济价值与生态服务功能价值的比值为 1:70 ,显然 ,高原生态系统的生态服务价值远远高于直接使用价值。因此 ,保护生态系统和生物多样性是维持生态系统稳定和保育高原生态过程的根本     

青藏铁路温性草原区铁路运营对啮齿动物群落结构的影响

以青藏铁路海晏段的温性草原区为研究地点,通过铗日法确定距离铁路不同距离的区域中啮齿动物的种群密度和群落结构,分析啮齿动物群落结构与植物群落结构之间的关系,探讨温性草原区铁路运营对啮齿动物群落结构的影响。结果表明,研究区域内所捕获的啮齿动物有甘肃鼠兔、五趾跳鼠、长尾仓鼠和灰仓鼠;从1984 年铁路投入运营以来,没有发现铁路运营带来新物种的入侵;啮齿动物的种群密度和群落结构在距离铁路不同距离的样带之间有明显的不同,在铁路路基附近的种群密度、物种数、多样性指数均明显高于距离铁路0.5 km和1 km的区域,而均匀性指数在路基附近最小;在距离铁路不同距离的区域中植物群落的特征没有明显差异,啮齿动物群落特征与植物群落特征之间没有明显的相关性。引起铁路路基附近啮齿动物种群密度、物种数、多样性指数偏高的原因可能是铁路修建与运营为啮齿动物提供了合适的生存环境与额外的食物资源。因此,铁路建设及运营对啮齿动物的群落结构有一定程度的影响。     

青藏高原微生物生态功能研究进展

青藏高原作为地球“第三极”和全球气候变化敏感区,有着复杂和极端的气候环境,同时也蕴藏了丰富而特殊的生物资源,因此其生物多样性及其对全球气候变化的响应等研究备受关注。随着免培养的分子生态学和高通量测序等技术的迅速发展,青藏高原微生物的多样性及其功能、与其他生物互作等方面的研究不断深入,人们得以进一步认识青藏高原微生物在调节和维持生态系统平衡稳定等方面的重要作用。本文以青藏高原微生物合成功能中的固碳、固氮和藏区特色食品生产和分解作用中的碳、氮、磷、硫元素循环和有毒有害物质的降解以及共生作用中的与微生物、动物、植物共生为主要内容,讨论了微生物对青藏高原其他物种以及生态环境等方面的独特贡献,并对其生态功能进行总结,明确青藏高原微生物对于其脆弱生态环境的重要意义,以期为青藏高原生物多样性保护及微生物资源的开发利用提供参考。     

青藏高原几种牧草附着耐低温乳酸菌的筛选

为筛选出适宜青藏高原低温发酵优良菌株,针对从青藏高原垂穗披碱草(Elymus nutans)、燕麦(Avena satival L.)和藏嵩草(Koeleria tibetica)中分离出的148株乳酸菌,经10℃低温条件下MRS液体培养基与不同培养时间(12、24、36和48 h)初筛后,进一步将初筛的菌株通过不同温度(10、15和25℃)条件下绿汁发酵液的复筛,并对其进行生理生化特性研究。结果表明,植物乳杆菌(Lactobacillus plantarum)31、干酪乳杆菌(Lactobacillus casei)Q5、戊糖片球菌(Pediococcus pentosaceus)Q6和棒状乳杆菌(Lactobacillus coryniformis)Q7这4株菌在MRS液体培养基和绿汁发酵液较低温环境中生长活性和快速产酸能力较强,而且生理生化特性指标表明,Q5比对应模式菌具有更广泛的糖源利用能力,Q7较对应模式菌具有更强的耐酸和耐低温特性。因此,上述4株乳酸菌可作为适宜青藏高原低温发酵青贮饲料备选菌株。     

Phylogeography of the Qinghai–Tibet Plateau endemic alpine herb Pomatosace filicula (Primulaceae)

In order to trace the response of alpine plants on the Qinghai–Tibet Plateau (QTP) to the Quaternary climate oscillations, the phylogeographic history of Pomatosace filicula Maxim. was investigated in the present study. Based on sequence variations of two maternally inherited plastid markers, matK and trnH-psbA, and the biparentally inherited nuclear ribosomal internal transcribed spacer (nrITS), we estimated the population genetic structure, lineage divergence timescale, and population dynamics of P. filicula. Seven plastid haplotypes and two nrITS genotypes were identified across the range-wide sampling of 200 individuals from 24 populations. Although AMOVA revealed a high level of differentiation among populations (F_ST = 0.560), no significant phylogeographic structure was detected (N_ST = 0.503, G_ST = 0.518, P > 0.05). Molecular dating suggested that the divergences between major plastid lineages and nrITS genotypes occurred during the early and middle Pleistocene, and the middle Pleistocene, respectively. This species most likely survived at multiple unglaciated sites on the QTP during the Last Glacial Maximum, with most of these sites located above 4000 m a.s.l. The species probably experienced range expansion at its distribution fringe, but demographic tests did not suggest significant population size changes. We proposed that pronounced effective gene flow (N_em = 0.393) and short generation time may have obscured the phylogeographic and demographic patterns of this species. Our findings will shed new light on the Quaternary evolutionary history of the alpine flora of the QTP.     

Carbon Balance in an Alpine Steppe in the Qinghai-Tibet Plateau

Carbon fluxes were measured using a static chamber technique in an alpine steppe in the Qinghai-Tibet Plateau from July 2000 to July 200t. It was shown that carbon emissions decreased in autumn and increased in spring of the next year, with higher values in growth seasons than in winters. An exponential correlation (Ecarbon = 0.22(exp(0.09T) + In(0.31P + 1)), R2 = 0.77, P < 0.001) was shown between carbon emissions and environmental factors such as temperature (T) and precipitation (P). Using the daily temperature (T) and total precipitation (R), annual carbon emission from soil to the atmosphere was estimated to be 79.6 g C/m2, 46% of which was emitted by microbial respiration. Considering an average net primary production of 92.5 g C/m2 per year within the 2 year experiment, alpine steppes can take up 55.9 g CO2-C/m2 per year. This indicates that alpine steppes are a distinct carbon sink, although this carbon reservoir was quite small.     

高山嵩草气孔导度对环境因子的响应模拟

以青藏高原地区高寒草甸常见建群种高山嵩草（Kobresia pygmaea）为研究对象，利用光合测定仪于2018年7-9月测定高山嵩草气体交换参数与环境因子的日变化值，利用土壤水分测量仪及环刀法、透膜法测得0-10 cm土壤水分数据作为模型变量。首先，采用3种气孔导度模型对高山嵩草气孔导度进行拟合和检验，其次，用Jarvis模型、Leuning模型和Gao模型对高山嵩草气孔导度在不同月份（7，8，9月）日变化的模拟结果进行分析，最后，总结并讨论了气孔导度对3个主要环境因子（光合有效辐射（Photosynthetically active radiation，PAR）、气温（T_air）、饱和水汽压差（Vapor pressure deficit，VPD））的响应特征。主要研究结果：（1）3个气孔导度模型都可以较好地模拟高山嵩草的气孔导度变化，Leuning模型表现最好（R²=0.726），Jarvis模型次之（R²=0.659），Gao模型准确度最低（R²=0.624）。（2）高山嵩草叶片气孔导度对3个环境因子的响应敏感度为PAR > VPD > T_air。在5-35℃气温范围内气孔导度呈现"钟形"响应，在T_air为24.83℃时达到最高值；气孔导度随着光合有效辐射强度PAR的增加（300-2100 μmol m^-2 s^-1）而增加，在高PAR时G_s增速变慢，随后出现下降趋势；气孔导度随着VPD增加（0.12-3.48 kPa）而降低。（3）三个模型均可以较好地模拟高山嵩草气孔导度对环境因子的响应特征，其中最敏感的环境因子均是VPD。Leuning模型对T_air和VPD最敏感，而Gao模型对PAR最敏感，对T_air不敏感。以上结果以期为气候变化背景下青藏高原地区植物叶片气孔导度的响应变化以及更大尺度的陆面模式中气孔导度模型的应用提供参考。