青藏高原东部高寒灌丛生物量分配对模拟增温的响应

植物生物量分配特征的变化反映了不同环境条件下植物的适应策略,全球气候变暖正在改变青藏高原高寒生态系统植被动态和生物量分配格局。然而,到目前为止,有关青藏高原高寒灌丛生物量分配特征对气候变暖的响应研究较少。为了探究气候变暖对高寒灌丛生物量分配的影响,以青藏高原东部典型的窄叶鲜卑花高寒灌丛为研究对象,分析了高寒灌丛灌木层、草本层和群落水平生物量分配特征对开顶式生长室（OTC）模拟增温的响应。研究结果表明：整个生长季节,模拟增温使空气温度和表层土壤温度分别升高0.6℃和1.2℃,使表层土壤水分含量下降2.7%。模拟增温使草本层和群落地上生物量显著增加57.8%和7.2%,使灌木层、草本层和群落根系生物量显著增加42.5%、105.6%和45.6%。然而,模拟增温没有显著影响灌木层地上生物量。同时,模拟增温使灌木层、草本层和群落总生物量显著增加25.6%、85.7%和28.4%,使灌木层、草本层和群落根冠比显著增加33.2%、30.4%和36.0%。由此可见,模拟增温在促进高寒灌丛生物量生产的同时将显著提高向地下根系部分的分配比例。Pearson相关分析表明,高寒灌丛生物量分配与空气温度、土壤温度和土壤硝态氮含量呈显著正相关关系;多元线性回归分析结果也表明,空气温度、土壤温度和土壤硝态氮含量解释了高寒灌丛生物量分配变异的50.8%以上。这些结果表明,青藏高原东部高寒灌丛植被能够通过调节生物量分配模式应对未来气候变暖。     

青藏高原多年冻土区不同水分条件的高寒草甸根系功能性状对增温的响应

在青藏高原多年冻土广泛分布的风火山地区,选择小嵩草（Kobresia pygmea）草甸和藏嵩草（Kobresia tibetica）沼泽化草甸为研究对象,采用开顶增温室（Open top chambers, OTCs）模拟气候变暖,探讨模拟增温对土壤水分差异的两种草甸地下生物量及根系功能性状的影响。结果显示,（1）增温显著增加小嵩草草甸0—20 cm根系生物量,主要是由于表层（0—10 cm）根系生物量显著增加,而对藏嵩草沼泽化草甸根系生物量无影响。（2）增温显著增加了小嵩草草甸根组织密度,同时提高了藏嵩草沼泽化草甸10—20 cm的比根长和比根面积（3）增温降低了小嵩草草甸的根系碳含量及10—20 cm根系氮含量,增加了藏嵩草沼泽化草甸的碳含量及10—20 cm根系氮含量,显著提高了小嵩草草甸和藏嵩草沼泽化草甸深层（10—20 cm）根系碳氮比。这些结果预示着增温使得土壤水分较低的小嵩草草甸朝着资源保守的慢速生长型发展,以适应暖干化的环境;土壤水分较高的藏嵩草沼泽化草甸朝着资源获取的快速生长型发展,加速利用土壤中的养分满足植物生长需要。可见,土壤水分可以调节高寒草甸对气候变暖的演变趋势,强调了水分的重要性。     

青藏高原多年冻土区高寒植被物种多样性和地上生物量

基于样方调查统计了青藏高原多年冻土区高寒草地生态系统植物的科属组成,计算了多样性指数和均匀度指数,探讨了多年冻土退化对高寒草地物种多样性的影响。结果表明:多年冻土退化过程中物种组成在属和物种丰富度上呈现降低趋势,湿、中生植物逐渐被旱中生和旱生植物替代;青藏高原多年冻土退化会导致高寒草地生态系统的物种多样性和初级生产力的降低,影响高寒草地生态系统的稳定性;物种多样性与初级生产力具有密切的抛物线型关系。     

气候变暖对青藏高原腹地高寒植被的影响

研究区高寒植被碳同位素组成的研究,表明气候环境对高原腹地植被具有明显的控制意义。在此基础上,通过对研究区植被样方的研究,对该区植被在高原气候暖干化过程中的变化趋势进行了探讨。提出暖干化的气候(环境是区域植被退化的主因,并对研究区植被退化速率进行了推算(14.2km/10a)。以样方数据分析为依托,重新拟定了研究区内干旱湿润区分界线,获得该区植物碳同位素值拟合干湿界限的支持。通过对年代间干湿分界线位置的比较,对高原气候暖干化模式下植被的退化趋势进行了模拟。     

高寒植物叶片性状对模拟降水变化的响应

降水变化对高寒草甸生态系统产生了显著影响,植物叶片性状特别是叶脉特征对降水变化非常敏感,然而高寒植物叶片性状特征如何响应降水变化还知之较少。采用集雨棚模拟增减50%降水的条件,以高寒草甸8种主要植物叶片为研究对象,研究了降水变化对叶片的叶脉率、叶脉密度、叶片大小、比叶质量、叶片总有机碳含量、叶片全氮含量、叶片碳同位素相对含量和碳氮比等叶片性状的影响。发现增水显著增加了植物的叶片大小、稳定碳同位素千分值、总有机碳含量、全氮含量,但显著降低了叶脉密度;而减水显著降低了叶片大小、稳定碳同位素千分值。植物叶片性状各指标对降水变化的响应存在协同变化和相互制约。不同水分生态类型的植物对降水变化的响应存在差异,中生植物通过增加叶片大小和减少叶脉密度积极应对降水的增加,矮生嵩草的叶片大小分别增加了200.3%,叶脉密度减小了17.5%,而旱中生植物通过减少叶片大小和增加叶脉密度应对降水的减少,垂穗披碱草和异针茅的叶片大小分别减少54.9%和30.7%,其叶脉密度分别增加25%和22.4%。羽状叶脉植物增加叶脉密度和稳定碳同位素千分值以适应增水条件,花苜蓿、异叶米口袋的叶脉密度的增加了7.8%和4.0%,稳定碳同位素千分值增加2.5%和3.3%,但增水条件下平行叶脉植物的叶脉密度不变或降低和稳定碳同位素千分值保持不变;减水增加了平行叶脉植物叶脉密度并减低了稳定碳同位素千分值,异针茅的叶脉密度增加了22.4%,稳定碳同位素千分值减小2.9%,而对羽状叶脉植物的叶脉密度和稳定碳同位素千分值减少或不变。植物叶片性状对增水的敏感性显著大于对减水的敏感性,增水的效应约为减水的2倍;叶片大小的敏感性显著大于其它叶片性状,约为其它叶片性状的10倍。因此,植物在应对短期降水变化时,植物形态可塑性的作用凸显,放大或缩小叶片大小是植物应对降水变化的最有效的途径,但是不同水分生态类型和叶脉类型植物可塑性的方向存在显著差异。     

青藏高原高寒矮嵩草草甸碳增汇潜力估测方法

以广布于青藏高原的高寒矮嵩草草甸为研究对象,研究了草甸碳储存的场所、碳库容量随草甸演替的变化过程及其碳增汇潜力的空间分布格局,同时探讨了高寒草甸碳增汇潜力估测的困惑与解决方法。结果表明,高寒草甸生态系统碳增汇潜力空间分布格局差异极大,主要受到土层厚度和草地演化进程的影响。高寒草甸碳主要贮存于草毡表层,其增汇潜力在于退化草地草毡表层的恢复与重建。保持适宜厚度的草毡表层是协调高寒草甸生产与碳生态服务功能的关键。随着退化高寒草甸的恢复,土壤容重呈现下降趋势,计算其系统碳增汇潜力,需要用根土体积比进行土层深度的校正。高寒草甸具有较大的固碳潜力,但其潜力的发挥受到气候和草地恢复与管理措施的影响,比较漫长。     

青藏高原矮火绒草(Leontopodium nanum)叶片性状对海拔高度变化的响应

植物叶片对环境变化十分敏感,能反映植物适应环境所形成的生存策略。为揭示高寒植物叶片性状对海拔高度变化的响应,对位于青藏高原东北部的冷龙岭3400—4200 m之间5个不同海拔高度的矮火绒草(Leontopodium nanum)叶片进行取样,采用常规石蜡制片技术和显微观察方法测定叶片外部形态、表皮气孔特征和解剖结构,探讨其叶片性状随海拔的变化,结果表明：（1）随海拔高度升高,叶面积呈减小的趋势,而比叶重和叶干物质含量增加;（2）叶片下表皮气孔密度随海拔升高呈先增加后下降的趋势,且气孔密度、气孔器面积、长度、宽度和潜在气孔导度指数等气孔特征之间存在显著相关性;（3）叶厚、栅栏组织和海绵组织厚度随海拔升高呈显著增厚的趋势;（4）叶片解剖结构可塑性和相关性分析显示,上、下角质层厚度的可塑性指数最大,而部分解剖结构指标间存在极显著的相关性。研究表明,矮火绒草为适应沿海拔上升温度降低的环境,主要采取叶片变小、变厚的对策,使植物趋于保温、保水和抗机械损伤的方向发展,并将资源最大化地投入到自身生长发育中。     

增温对青藏高原高寒草甸呼吸作用的影响

生态系统呼吸(ER)和土壤呼吸(SR)是草地生态系统碳排放的关键环节,其对气候变化极为敏感。高寒草甸是青藏高原典型的草地生态系统,其呼吸作用对气候变化的响应对区域碳排放具有重要的影响。以高寒草甸生态系统为对象,于2012—2016年采用模拟增温的方法研究呼吸作用对增温的响应。结果表明:增温对高寒草甸ER的影响存在年际差异,2013年和2014年增温对ER无显著影响,其他年份显著增加ER(P<0.05),综合5年结果,平均增幅达22.3%。增温显著促进了高寒草甸SR(P<0.05),较对照处理5年平均增幅高达67.1%;增温总体上提高了SR在ER中的比例(P<0.05),最高增幅达到59.9%。ER和SR与土壤温度有显著的正相关关系(P<0.05),与土壤水分没有显著的相关关系(P>0.05)。对照样地中,土壤温度分别能解释33.0%和18.5%的ER和SR变化。在增温条件下,土壤温度可以解释20.5%和13.0%的ER和SR变化。在增温条件下,SR的温度敏感性显著增加,而ER的温度敏感性变化较小,导致SR的比重进一步增加。因此,在未来气候变暖条件下,青藏高...     

青藏高原高寒草地群落叶片功能性状对降水的非线性响应

群落叶片功能性状受到外界环境和自身发育的共同影响,其响应特征和过程的研究有助于了解环境胁迫下植物的适应策略,以应对全球变化下的生物多样性和生态系统功能丧失。通过对青藏高原高寒草地115个样点的调查取样,测定群落叶片碳、氮和磷含量(LC、LN和LP)及干物质量(LDMC)4种能够反映植物生存策略的叶片功能性状,以物种相对多度为基础计算群落加权平均值(CWM)。结合降水量、气温和土壤因子,探索高寒草地群落叶片功能性状响应机制。结果表明：(1)降水量对群落叶片功能性状影响显著(P<0.01),而温度对群落叶片功能性状影响不显著(P>0.05);(2)土壤全氮和有机碳对CWM＿LC、CWM＿LN、CWM＿LP和CWM＿LDMC影响显著(P<0.01),且除CWM＿LDMC外,其余性状均表现为非线性响应,呈先下降后上升趋势;(3)土壤含水量和容重对CWM＿LC、CWM＿LN、CWM＿LP和CWM＿LDMC影响显著(P<0.05),且土壤含水量对各性状的影响为非线性,呈先下降后上升趋势。该研究说明水分是青藏高原高寒草地群落叶片功能性状的主要影响因子,高寒草地对恶劣环境的适应...     

Changes in individual plant traits and biomass allocation in alpine meadow with elevation variation on the Qinghai-Tibetan Plateau

Plant traits and individual plant biomass allocation of 57 perennial herbaceous species, belonging to three common functional groups (forbs, grasses and sedges) at subalpine (3700 m ASL), alpine (4300 m ASL) and subnival (⩾5000 m ASL) sites were examined to test the hypothesis that at high altitudes, plants reduce the proportion of aboveground parts and allocate more biomass to belowground parts, especially storage organs, as altitude increases, so as to geminate and resist environmental stress. However, results indicate that some divergence in biomass allocation exists among organs. With increasing altitude, the mean fractions of total biomass allocated to aboveground parts decreased. The mean fractions of total biomass allocation to storage organs at the subalpine site (7%±2% S.E.) were distinct from those at the alpine (23%±6%) and subnival (21%±6%) sites, while the proportions of green leaves at all altitudes remained almost constant. At 4300 m and 5000 m, the mean fractions of flower stems decreased by 45% and 41%, respectively, while fine roots increased by 86% and 102%, respectively. Specific leaf areas and leaf areas of forbs and grasses deceased with rising elevation, while sedges showed opposite trends. For all three functional groups, leaf area ratio and leaf area root mass ratio decreased, while fine root biomass increased at higher altitudes. Biomass allocation patterns of alpine plants were characterized by a reduction in aboveground reproductive organs and enlargement of fine roots, while the proportion of leaves remained stable. It was beneficial for high altitude plants to compensate carbon gain and nutrient uptake under low temperature and limited nutrients by stabilizing biomass investment to photosynthetic structures and increasing the absorption surface area of fine roots. In contrast to forbs and grasses that had high mycorrhizal infection, sedges had higher single leaf area and more root fraction, especially fine roots.     

Ploidy in the alpine sedge Kobresia pygmaea (Cyperaceae) and related species: combined application of chromosome counts,new microsatellite markers and flow cytometry

Polyploidy is a fundamental mechanism in evolution, but is hard to detect in taxa with agmatoploidy or aneuploidy. We tested whether a combination of chromosome counting, microsatellite analyses and flow cytometric measurements represents a suitable approach for the detection of basic chromosome numbers and ploidy in Kobresia (Cyperaceae). Chromosome counting resulted in 2n = 64 for Kobresia pygmaea and K. cercostachys, 2n = 58 and 64 for K. myosuroides, and 2n = 72 for K. simpliciuscula. We characterized eight microsatellite loci for K. pygmaea, which gave a maximum of four alleles per individual. Cross‐species amplification was tested in 26 congeneric species and, on average, six of eight loci amplified successfully. Using flow cytometry, we confirmed tetraploidy in K. pygmaea. Basic chromosome numbers and ploidy were inferred from chromosome counts and the maximum number of alleles per locus. We consider the basic numbers as x = 16 and 18, with irregularities derived from agmatoploidy and aneuploidy. Across all Kobresia taxa, ploidy ranged from diploid up to heptaploid. The combination of chromosome counts and microsatellite analyses is an ideal method for the determination of basic chromosome numbers and for inferring ploidy, and flow cytometry is a suitable tool for the identification of deviating cytotypes. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176 , 22–35.     

黄土丘陵区草地植被群落优势种叶片功能性状对氮磷添加的响应

以黄土丘陵区草地植被群落3种优势种白羊草、长芒草和达乌里胡枝子为对象,采用裂区试验设计,设置0、50和100 kg N·hm^-2·a^-13个氮处理和0、40和80 kg P₂O₅·hm^-2·a^-1 3个磷处理,于生长旺盛期测定了各植物的叶长、叶宽、比叶面积、叶片干物质含量、叶片氮、磷含量和氮磷比等指标,分析不同优势种叶片功能性状对氮磷添加的响应差异.结果表明:与未施肥相比,50和100 kg N·hm^-2·a^-1处理下白羊草叶长和叶宽分别显著增加35.3%和64.4%,而长芒草仅有叶长显著增加58.8%,达乌里胡枝子仅有叶宽显著增加33.9%,但三者叶片干物质含量分别显著降低10.7%、15.3%和11.2%,白羊草和长芒草叶片氮含量分别显著增加23.0%和99.2%,氮磷比分别显著增加45.8%和96.9%;40和80 kg P₂O₅·hm^-2·a^-1处理下达乌里胡枝子叶长、叶宽和比叶面积分别显著增加56.9%、41.4%和19.6%,叶片干物质含量显著下降14.9%,三者叶片磷含量分别显著增加96.7%、110.9%和238.4%,氮磷比分别显著降低45.8%、42.8%和53.7%.50 kg N·hm^-2·a^-1处理下,与未施磷相比,40和80 kg P₂O₅·hm^-2·a^-1处理后仅达乌里胡枝子叶长和叶宽显著增大,3种植物叶片磷含量显著增加,白羊草和长芒草叶片氮含量显著降低;100 kg N·hm^-2·a^-1处理下,施磷后白羊草和长芒草叶长、达乌里胡枝子叶宽显著增大,三者叶片磷含量显著增加,白羊草叶片氮含量显著降低.综上表明,3个优势种植物叶片功能性状对短期氮磷添加的响应存在明显差异,这些差异与物种属性和施肥水平有关,不同优势种对氮磷添加响应的差异对维持草地群落多样性和稳定性具有重要作用.     

蛋白质水平解析高山嵩草对青藏高原昼夜环境的响应（英文）

高山嵩草(Kobresia pygmaea)是高寒草甸的重要建群种,其生长发育同时受到年际、季节和昼夜环境变化的影响,但目前对高山嵩草响应昼夜环境变化的研究很少。本研究通过差异蛋白质组学的方法,结合抗氧化酶活性测定和蛋白质免疫印迹技术,分析了高山嵩草在一天中每4个小时的蛋白质表达变化。结果表明:在白天的高温、强光和紫外辐射,以及夜里的低温等不利条件下,高山嵩草体内的抗氧化酶、热休克蛋白和脱落酸代谢相关的蛋白质等能够被大量诱导表达,从而对细胞和机体起到保护作用。同时,受蛋白质调控的一些生命活动如光合作用会集中在较为适宜的时间段进行。通过体内蛋白质表达的可塑性和灵活性,高山嵩草能够有效地应对短时间里环境的变化。     

近30年来青藏高原高寒草地NDVI动态变化对自然及人为因子的响应

草地生态系统是陆地生态系统的重要组成部分,在调节气候、水土保持、防风固沙、保护生物多样性等方面发挥着重要作用。青藏高原是全球海拔最高的独特地域单元,平均海拔超过4000 m,素有“世界第三极”之称,亦是我国重要的生态安全屏障,其对气候变化敏感且易受人类活动的影响,属于气候变化敏感区和生态脆弱带。近年来,由于气候变化和人类活动的不断加剧,青藏高原区域气候和环境发生了重大变化,气候变暖、水污染、草地退化和沙化等问题已严重阻碍了当地社会经济的可持续发展。高寒草地是青藏高原主要的植被类型,在气候变化和人类活动加剧的背景下,青藏高原高寒草地植被的动态变化受到人们的广泛关注。归一化植被指数（Normalized difference vegetation index, NDVI）因能有效地反映植被覆盖程度和生长状况而被广泛应用于植被动态的研究中。气温与降水被认为是影响青藏高原植被动态的主要气候因子,放牧强度与人口数量则是主要人为因子。因此,研究高寒草地植被对气候变化和人类活动的响应机制对预测未来草地变化有着重要的意义。基于青藏高原生长季草地的NDVI、气温、降水、放牧强度及人口数量等数据,在县区尺度上,采用趋势分析法探究了1982—2013年青藏高原143个县区生长季草地NDVI动态变化、气候变化及人类活动的变化,同时采用面板数据模型分析了32年来青藏高原143个县区气候、人为因子变化对草地NDVI变化的相对贡献。研究结果显示：（1）青藏高原高寒草地生长季NDVI总体呈增长趋势,草地植被生长状态呈现“整体改善、局部退化”趋势;（2）青藏高原生长季平均气温与降水量整体增加,气候呈现“暖湿化”趋势;（3）在长时间尺度上,气候因子主导了青藏高原高寒草地NDVI的变化,降雨和气温的增加促进草地NDVI的增加,放牧强度的持续增加则导致草地NDVI的减少。     

Changes in plant biomass and species composition of alpine Kobresia meadows along altitudinal gradient on the Qinghai-Tibetan Plateau

Alpine Kobresia meadows are major vegetation types on the Qinghai-Tibetan Plateau. There is growing concern over their relationships among biodiversity, productivity and environments. Despite the im-portance of species composition, species richness, the type of different growth forms, and plant bio-mass structure for Kobresia meadow ecosystems, few studies have been focused on the relationship between biomass and environmental gradient in the Kobresia meadow plant communities, particularly in relation to soil moisture and edaphic gradients. We measured the plant species composition, her-baceous litter, aboveground and belowground biomass in three Kobresia meadow plant communities in Haibei Alpine Meadow Ecosystem Research Station from 2001 to 2004. Community differences in plant species composition were reflected in biomass distribution. The total biomass showed a de-crease from 13196.96±719.69 g/m2 in the sedge-dominated K. tibetica swamp to 2869.58±147.52 g/m2 in the forb and sedge dominated K. pygmaea meadow, and to 2153.08±141.95 g/m2 in the forbs and grasses dominated K. humilis along with the increase of altitude. The vertical distribution of below-ground biomass is distinct in the three meadow communities, and the belowground biomass at the depth of 0-10 cm in K. tibetica swamp meadow was significantly higher than that in K. humilis and K. pygmaea meadows (P<0.01). The herbaceous litter in K. tibetica swamp was significantly higher than those in K. pygnaeca and K. humilis meadows. The effects of plant litter are enhanced when ground water and soil moisture levels are raised. The relative importance of litter and vegetation may vary with soil water availability. In the K. tibetica swamp, total biomass was negatively correlated to species richness (P<0.05); aboveground biomass was positively correlated to soil organic matter, soil moisture, and plant cover (P<0.05); belowground biomass was positively correlated with soil moisture (P<0.05). However, in the K. pygnaeca and K. humilis meadow communities, aboveground biomass was posi-tively correlated to soil organic matter and soil total nitrogen (P<0.05). This suggests that the distribu-tion of biomass coincided with soil moisture and edaphic gradient in alpine meadows.     

青藏高原高寒草甸夏季植被特征及对模拟增温的短期响应

以青藏高原高寒草甸为研究对象,研究了草甸植被夏季生长动态特征;同时采用红外辐射器模拟增温的方法,探讨了草甸植被对增温的短期(1a)响应.结果表明:(1)高寒草甸夏季植被高度与地下生物量、总生物量相关性不显著,盖度与二者相关性极显著;高度对地上生物量影响较大(R=0.892,P＜0.01),盖度对地下生物量(R=0.883,P＜0.01)和总生物量(R=0.888,P＜0.01)影响较大.(2)高寒草甸夏季植被地上部分和地下部分表现出不同的生长模式,地上部分近似等速生长(幂指数为1.011),地下部分则表现为异速生长(幂指数为0.459),但整体呈现异速生长(幂指数为0.473).(3)高寒草甸夏季植被地上生物量(P＜0.05)在6月份较地下生物量(P＞0.05)对环境更为敏感,且一年之后地上-地下生物量均呈减小趋势,这与空气温度、土壤温度和土壤水分的显著减小密切相关.(4)红外辐射器在高寒草甸的增温度效果较好,空气、地表、土壤温度都随增温幅度增强而增加;短期增温对高寒植被有正效应(T0-T1),而温度持续升高则对植被产生负效应(T1-T2);各植被指标的方差分析都未达到显著水平,表明短期增温对该植被影响不显著.     

川西北高寒草地3种主要植物的生长及物质分配对温度升高的响应

在野外自然条件下采用开顶式生长室模拟增温的方法, 研究了增温对川西北高寒草地3种主要植物(单子叶草本植物垂穗披碱草(Elymus nutans)和双子叶草本植物尼泊尔酸模(Rumex acetosa)和鹅绒委陵菜(Potentilla anserina))的生长及物质分配的影响。研究结果表明, 增温对3种植物的生长产生了显著影响, 垂穗披碱草和尼泊尔酸模的比叶面积和生物量积累在增温后显著增加, 而鹅绒委陵菜在增温后显著减少。在各组分中, 增温处理使尼泊尔酸模的叶生物量显著增加, 根生物量却显著下降, 而鹅绒委陵菜叶和茎的生物量在增温后显著减少, 根生物量却显著增加。增温对尼泊尔酸模各组分的养分含量产生了显著影响, 其中, 根部碳含量在增温后显著增加, 而氮含量在增温后显著减少。增温对尼泊尔酸模和鹅绒委陵菜的生物量在各组分中的分配产生了显著影响, 增温显著增加了尼泊尔酸模的叶重比(LMR)、根重比(RMR)和地下生物量/地上生物量(R/S), 而茎重比(SMR)在增温后却显著降低; 增温显著增加了鹅绒委陵菜的RMR和R/S, 而SMR和LMR在增温后却显著降低。增温对尼泊尔酸模和鹅绒委陵菜各组分中的碳、氮分配产生了显著影响, 增温显著增加了碳、氮在尼泊尔酸模叶片的分配比例, 并且使尼泊尔酸模根部的碳分配比例也显著增加, 而茎部的碳、氮分配比例却显著减少; 增温显著减少了碳在鹅绒委陵菜叶片的分配比例, 而根部的碳、氮分配比例却显著增加。     

甘肃陇东黄土高原冬小麦对气候变暖的响应

使用地面试验田平行观测资料,就甘肃陇东黄土高原冬小麦对气候变暖的响应进行了比较分析。结果表明,1981年以来,冬小麦对气候变暖的响应主要表征为全生育期与越冬期的缩短,返青期与收获期提前,而越冬前和返青后的生长期总日数并无明显变化;各发育阶段对增温的响应差异明显,增温使营养生长阶段的返青至起身至拔节和生殖生长阶段的开花及成熟日期提前,乳熟日期和开花至成熟期间的总日数无明显变化,但增温使生殖生长阶段的开花至乳熟有延长趋势,而乳熟至成熟期有缩短趋势。籽粒重随≥10℃积温的增加而增加,随3月至收获期最高气温的升高而减少;产量随平均最低气温的升高和≥0℃、≥5℃、≥10℃和≥15℃积温的增加而增加,随≥20℃积温的增加而减少,表明高温天气增加对冬小麦产量有一定程度的逼熟减产负作用产生。     

History and evolution of alpine plants endemic to the Qinghai-Tibetan Plateau: Aconitum gymnandrum (Ranunculaceae)

How Quaternary climatic oscillations affected range distributions and intraspecific divergence of alpine plants on the Qinghai‐Tibetan Plateau (QTP) remains largely unknown. Here, we report a survey of chloroplast DNA (cpDNA) and nuclear ribosomal internal transcribed spacer (ITS) DNA variation aimed at exploring the phylogeographical history of the QTP alpine endemic Aconitum gymnandrum. We sequenced three cpDNA fragments (rpl20–rps12 intergenic spacer, the trnV intron and psbA‐trnH spacer) and also the nuclear (ITS) region in 245 individuals from 23 populations sampled throughout the species’ range. Two distinct lineages, with eastern and western geographical distributions respectively, were identified from a phylogenetic analysis of ITS sequence variation. Based on a fast substitution rate, these were estimated to have diverged from each other in the early Pleistocene approximately 1.45 Ma. The analysis of cpDNA variation identified nine chlorotypes that clustered into two major clades that were broadly congruent in geographical distribution with the two ITS lineages. The east–west split of cpDNA divergence was supported by an amova which partitioned approximately half of the total variance between these two groups of populations. Analysis of the spatial distribution of chlorotypes showed that each clade was subdivided into two groups of populations such that a total of four population groups existed in the species. It is suggested that these different groups derive from four independent glacial refugia that existed during the Last Glacial Maximum (LGM), and that three of these refugia were located at high altitude on the QTP platform itself at that time. Coalescent simulation of chlorotype genealogies supported both an early Pleistocene origin of the two main cpDNA clades and also the ‘four‐refugia’ hypothesis during the LGM. Two previous phylogeographical studies of QTP alpine plants indicated that such plants retreated to refugia at the eastern/south‐eastern plateau edge during the LGM and/or previous glacial maxima. However, the results for A. gymnandrum suggest that at least some of these cold‐tolerant species may have also survived centrally on the QTP platform throughout the Quaternary.     

Responses of white spruce (Picea glauca) to experimental warming at a subarctic alpine treeline

From 2001 to 2004 we experimentally warmed 40 large, naturally established, white spruce [Picea glauca (Moench) Voss] seedlings at alpine treeline in southwest Yukon, Canada, using passive open‐top chambers (OTCs) distributed equally between opposing north and south‐facing slopes. Our goal was to test the hypothesis that an increase in temperature consistent with global climate warming would elicit a positive growth response. OTCs increased growing season air temperatures by 1.8°C and annual growing degree‐days by one‐third. In response, warmed seedlings grew significantly taller and had higher photosynthetic rates compared with control seedlings. On the south aspect, soil temperatures averaged 1.0°C warmer and the snow‐free period was nearly 1 month longer. These seedlings grew longer branches and wider annual rings than seedlings on the north aspect, but had reduced Photosystem‐II efficiency and experienced higher winter needle mortality. The presence of OTCs tended to reduce winter dieback over the course of the experiment. These results indicate that climate warming will enhance vertical growth rates of young conifers, with implications for future changes to the structure and elevation of treeline contingent upon exposure‐related differences. Our results suggest that the growth of seedlings on north‐facing slopes is limited by low soil temperature in the presence of permafrost, while growth on south‐facing slopes appears limited by winter desiccation and cold‐induced photoinhibition.