虫草蝠蛾分布与高寒草甸植物的关系

本文报道了滇西北冬虫夏草寄主昆虫——虫草蝠蛾分布与高寒草甸植物分布的关系。滇西北海拔3800m以上区域的高寒草甸是虫草蝠蛾主要分布区,草甸植物群体的分布状况明显地制约着蝠蛾昆虫种群的分布。在海拔3800～4200m内,有少量蝠蛾种类和种群分布;海拔4200～4600m是典型的高寒草甸类型区,该虫嗜食的草本植物繁多,生长旺盛,是蝠蛾种类和群体密集分布区;海拔4700m以上地区,随着海拔增高,植被减少,蝠蛾种类和群体分布下降;海拔5100m以上地区则没有该虫分布。植物的季相与幅蛾种群数量和生物量有着十分密切的关系。

不同环境条件下几种高寒草甸植物的非克隆繁殖投入和生长

通过对高寒草甸生态系统金露梅灌丛、矮嵩草草甸、围栏矮嵩草草甸以及模拟地球增温效应下5种植物繁殖投入和生长特性的测定,结果表明,矮嵩草、麻花艽、苔草以及美丽风毛菊的叶长沿对照矮嵩草草甸、0TC、围栏以及金露梅灌丛呈现上升趋势,只是灌丛中苔草和麻花艽两种植物的叶长较围栏和OTC有所下降,而环境变化对植物的叶宽的影响较小。苔草在金露梅灌丛中的繁殖投入最大,其次是矮嵩草草甸和围栏,OTC中苔草的繁殖投入几乎为零。围栏与矮嵩草草甸内苔草的繁殖投入差异不显著,而两者中植物的繁殖投入与金露梅灌丛相比,差异性显著(P<0.05)。矮火绒草在矮嵩草草甸中的繁殖投入最大,其次是0Tc和围栏,灌丛中矮火绒草的繁殖投入最小。OTC与矮嵩草草甸内矮火绒草的繁殖投入差异不显著,而OTC与围栏中矮火绒草的繁殖投入差异性显著(P<0.05)。由此我们可以得出一个结论:繁殖投入随环境梯度的变化,反映了植物繁殖对策和繁殖投入在整个生活史特征中的可塑性。

不同放牧强度对高寒草甸植物群落返青的影响

针对不同放牧强度下海北地区高寒草甸植物群落进行调查,结果表明,不同放牧强度对植物群落种类组成影响不明显,植株高度随放牧强度的减小而逐渐增高。群落中的优势种矮嵩草、披碱草的密度随放牧强度的减小而逐渐减小,但地上生物量随放牧强度的减小而逐渐增加。次优势种异针茅、紫羊茅、唐松草和黑褐苔草的密度随放牧强度的减小而逐渐减小,地上生物量的变化也逐渐减小。一些适口性差的阳性植物如美丽凤毛菊的密度、地上生物量随放牧强度的减小而逐渐增大,且植物群落随着放牧强度的减小其差异性显著。高寒草甸植物群落在返青期由于对重度放牧条件下过度采食,植物光合叶面积减小,根系营养物质被大量消耗,植株生长发育不良导致植物净生产量下降。因此,适宜地采食有利于植物返青,且植物地上净生产量将有所提高。

高寒草甸优势植物叶内、根内与土壤原核微生物群落的分异

植物内生菌具有帮助植物吸收营养元素,增强植物免疫力,抵御外界生物和非生物胁迫等功能。植物的根内和叶内存在大量的内生菌,影响着植物的健康生长。但不同植物地下(根内)和地上(叶内)内生原核微生物,以及与土壤微生物在组成和群落结构上的差异和联系还有待探索。以青藏高原高寒草甸三种优势植物青藏苔草(Carex moorcroftii)、火绒草(Leontopodium jacotianum)和高山嵩草(Carex parvula)为对象,研究了高寒草甸优势植物叶内、根内、土壤原核微生物组的组成及其与样品类型和植物类型之间的关系。结果表明:1)在门分类水平上,有13个门在土壤、叶内和根内之间有显著差异,只有5个门在不同植物之间有显著性差异,分别是变形菌门、厚壁菌门、酸杆菌门、疣微菌门以及FBP;2)在α多样性上,同种植物土壤、叶内、根内之间差异显著,而不同植物在土壤和根内差异显著,但在叶内无显著性差异;3)样品类型(叶内、根内以及土壤)是决定植物微生物组差异的最主要因子,对微生物群落变异的贡献度为20.13%;不同植物类型之间微生物群落也有显著性差异,植物类型对总变异的贡献率为14.41%,并且植物类型和植物相关部位(叶内,根内)以及土壤之间有强烈的交互作用(17.40%)。以上结果表明,每种植物叶内、根内以及周边土壤都具有独特的生态位,体现了原核微生物在样品类型和不同植物间上生态位的差异,同时也表明了原核微生物群落对这些生态位的适应性。最后,我们确定了与土壤相比有显著性差异的叶内和根内特有的微生物菌群并对高丰度菌群进行功能预测,以假单胞菌Pseudomonas为代表的菌群在叶内和根内显著富集,这些微生物包含参与多种代谢过程的功能基因,在促进营养元素吸收、提高植物在寒冷中的生态适应性方面有着重要的潜在功能。本研究的结果对深入探索高寒环境下植物-内生微生物互作机制提供了科学数据。

高原鼠兔有效洞穴密度对高寒草甸优势植物叶片和土壤氮磷化学计量特征的影响

采用有效洞穴密度代替高原鼠兔(Ochotona curzoniae)活动强度的方法,研究了高原鼠兔有效洞穴密度(10、15、21和31个/625 m^2)对高寒草甸优势植物高山嵩草(Kobresiapygmaea)、垂穗披碱草(Elymus nutans)、小花草玉梅(Anemone rivularis)叶片和土壤氮(N)磷(P)化学计量特征的影响。结果表明,3种优势植物叶片N含量随有效洞穴密度增加而显著增加(P<0.05),但叶片P含量却出现分异,表现为高山嵩草和垂穗披碱草叶片P含量随有效洞穴密度增加而先增加后降低(P<0.05),小花草玉梅叶片P含量逐渐增加(P<0.05);高山嵩草叶片N:P随有效洞穴密度增加先降低后增加(P<0.05),垂穗披碱草叶片N:P逐渐增加,小花草玉梅叶片N:P则先增加后降低。土壤0-10 cm和10-20 cm土层N含量随有效洞穴密度增加无明显变化;0—10cm土层P含量随有效洞穴密度增加先降低后增加,10—20 cm土层P含量逐渐降低;0—10 cm土层N:P随有效洞穴密度增加元明显变化,而10-20 cm土层N:P则逐渐增加。优势植物叶片N、P、N:P与土壤N、P、N:P的相关性受植物根系分布特征和生存微环境的约束。

青藏高原东部高寒草甸特有植物染色体倍性与耐寒适应性研究

以青藏高原东部4种高寒草甸特有植物为研究对象,对其染色体倍性进行了鉴定及统计学分析,以期探明染色体倍性与植物耐寒机制间的关系。结果表明,所选的4个特有种独一味、羽叶点地梅、星叶草、天蓝韭染色体均为二倍体,无染色体加倍现象。与低海拔亲缘关系较近的植物相比,二倍体更能适应高海拔地区寒冷缺氧的环境。

施肥和增雨雪对矮嵩草草甸4种典型植物凋落物分解的影响

设9个试验处理(夏季增雨、冬季增雪、施N肥、施N肥与夏季增雨交互作用、施N肥与冬季增雪交互作用、施P肥、施P肥与夏季增雨交互作用、施P肥与冬季增雪交互作用和对照)研究增施氮磷肥及水分对海北站矮嵩草(Kobresia humilis)草甸中垂穗披碱草(Elymus nutans)、矮嵩草、甘肃棘豆(Oxytropis kansuensis)与麻花艽(Gentiana straminea)4种典型植物地上部分凋落物分解速率的影响。结果表明:凋落物分解速率为甘肃棘豆>麻花艽>矮嵩草>垂穗披碱草,甘肃棘豆地上部分分解最快,垂穗披碱草的分解最慢,不同植物功能类群间差异显著。4种植物地上部分分解最快的时间都在降水充足的夏季。分解第185 d和262 d时,垂穗披碱草的质量残留率均极显著高于其他3种(P<0.01),麻花艽质量残留率极显著低于矮嵩草(P<0.01);分解362 d时,甘肃棘豆的分解速率显著高于垂穗披碱草和矮嵩草,但棘豆与麻花艽间差异并不显著,这与不同牧草的适口性、氮磷含量等属性有关。在N处理下,棘豆地上部分分解最快,分解其质量的95%所需时间为649.5 d,比对照缩短286.7 d。在没有增雨雪的基础上增施氮磷肥则对矮嵩草地上部分的分解起抑制作用,但影响不显著,水肥效应加以耦合会加速凋落物的分解。

No C_4 Plants Found at the Haibei Alpine Meadow Ecosystem Research Station in Qinghai, China: Evidence from Stable Carbon Isotope Studies

Using the measurement of stable carbon isotopes in leaves as a tool to investigate photosynthetic pathway of 102 plant species grown at an alpine meadow ecosystem, at the foot of the Qilian Mountain, Qinghai, China. The results indicate that the delta C-13 values of plants have a narrow range from -28.24parts per thousand to -24.84parts per thousand, which means that none of the species examined belongs to C-4 and crassulaceous acid metabolism (CAM) photosynthetic pathway and all of these species perform photosynthesis through the C-3 pathway. This is likely due to a long-term adaptation to environments at the alpine meadow ecosystem.

Response of Biomass Spatial Pattern of Alpine Vegetation to Climate Change in Permafrost Region of the Qinghai-Tibet Plateau,China

Alpine ecosystems in permafrost region are extremely sensitive to climate changes.To determine spatial pattern variations in alpine meadow and alpine steppe biomass dynamics in the permafrost region of the Qinghai-Tibet Plateau,China,calibrated with historical datasets of above-ground biomass production within the permafrost region's two main ecosystems,an ecosystem-biomass model was developed by employing empirical spatialdistribution models of the study region's precipitation,air temperature and soil temperature.This model was then successfully used to simulate the spatio-temporal variations in annual alpine ecosystem biomass production under climate change.For a 0.44°C decade-1 rise in air temperature,the model predicted that the biomasses of alpine meadow and alpine steppe remained roughly the same if annual precipitation increased by 8 mm per decade-1,but the biomasses were decreased by 2.7% and 2.4%,respectively if precipitation was constant.For a 2.2°C decade-1 rise in air temperature coupled with a 12 mm decade-1 rise in precipitation,the model predicted that the biomass of alpine meadow was unchanged or slightly increased,while that of alpine steppe was increased by 5.2%.However,in the absence of any rise in precipitation,the model predicted 6.8% and 4.6% declines in alpine meadow and alpine steppe biomasses,respectively.The response of alpine steppe biomass to the rising air temperatures and precipitation was significantly lesser and greater,respectively than that of alpine meadow biomass.A better understanding of the difference in alpine ecosystem biomass production under climate change is greatly significant with respect to the influence of climate change on the carbon and water cycles in the permafrost regions of the Qinghai-Tibet Plateau.

Uptake and Recovery of Soil Nitrogen by Bryophytes and Vascular Plants in an Alpine Meadow

Due to their particular physiology and life history traits, bryophytes are critical in regulating biogeochemical cycles and functions in alpine ecosystem. Hence, it is crucial to investigate their nutrient utilization strategies in comparison with vascular plants and understand their responses to the variation of growing season caused by climate change. Firstly, this study testified whether or not bryophytes can absorb nitrogen(N) directly from soil through spiking three chemical forms of 15N stable isotope tracer. Secondly, with stronger ability of carbohydrates assimilation and photosynthesis, it is supposed that N utilization efficiency of vascular plants is significantly higher than that of bryophytes. However, the recovery of soil N by bryophytes can still compete with vascular plants due to their greater phytomass. Thirdly, resource acquisition may be varied from the change of growing season, during which N pulse can be manipulated with 15N tracer addition at different time. Both of bryophytes and vascular plants contain more N in a longer growing season, and prefer inorganic over organic N. Bryophytes assimilate more NH4+ than NO3– and amino acid, which can be indicated from the greater shoot excess 15N of bryophytes. However, vascular plants prefer to absorb NO3– for their developed root systems and vascular tissue. Concerning the uptake of three forms N by bryophytes, there is significant difference between two manipulated lengths of growing season. Furthermore, the capacity of bryophytes to tolerate N-pollution may be lower than currently appreciated, which indicates the effect of climate change on asynchronous variation of soil N pools with plant requirements.

Classification of plant functional types based on the nutrition traits： a case study on alpine meadow community in the Zoigê Plateau

The ecological concept of Plant Functional Types（PFTs）, which refers to the assemblage of plants with certain functional traits, has been introduced for the study of plant responses to the environment change and human disturbance. Taking the alpine meadow community in the Zoigê Plateau as a study case, this paper classified PFTs in terms of plant nutrition traits. The sequential results are as follows.（1） The main herbages in the Zoigê Plateau included 16 species in 5 families. Among the five families, Cyperaceae vegetation accounted for 81.37%of herbage area in total, while the remaining 4families occupied less than 20%. As for the species,Kobresia setchwanensis Hand.-Maizz. was dominant,accounting for 48.74% of the total area; while the remaining 51.26% was comprised of Polygonum viviparum L., Anaphalis fiavescens Hand.-Mazz.,Stipa aliena Keng and other species.（2） By using the Principal Component Analysis（PCA）, the assessment of herbages nutrition was carried out based on the comprehensive multi-index evaluation model.Polygonum viviparum L. had the highest nutritional value score（1.43）, and Stipa aliena Keng had the lowest（-1.40）. Nutritional value of herbage species had a significantly positive correlation with altitude（P＆lt;0.01） in the Zoigê Plateau.（3） Based on the nutritional values, herbages in the Zoigê Plateau could be grouped into 3 nutrition PFTs（high, medium and low） by using the Natural Breaks（Jenks） method.

Sources of uncertainty in exploring rangeland phenology： A case study in an alpine meadow on the central Tibetan Plateau

Global climate change has been found to substantially influence the phenology of rangeland,especially on the Tibetan Plateau. However, there is considerable controversy about the trends and causes of rangeland phenology owing to different phenological exploration methods and lack of ground validation. Little is known about the uncertainty in the exploration accuracy of vegetation phenology.Therefore, in this study, we selected a typical alpine rangeland near Damxung national meteorological station as a case study on central Tibetan Plateau, and identified several important sources influencing phenology to better understand their effects on phenological exploration. We found man-made land use was not easily distinguished from natural rangelands, and therefore this may confound phenological response to climate change in the rangeland. Change trends of phenology explored by four methods were similar, but ratio threshold method(RTM) was more suitable for exploring vegetation phenology in terms of the beginning of growing season(BGS) and end of growing season(EGS). However, some adjustments are needed when RTM is used in extreme drought years. MODIS NDVI/EVI dataset was most suitable for exploring vegetation phenology of BGS and EGS. The discrimination capacities of vegetation phenology declined with decreasing resolution of remote sensing images from MODIS to GIMMS AVHRR datasets. Additionally, distinct trends of phenological change rates were indicated in different terrain conditions, with advance of growing season in high altitudes but delay of season in lower altitudes. Therefore, it was necessary to eliminate interference of complex terrain and man-made land use to ensure the representativeness of natural vegetation. Moreover, selecting the appropriate method to explore rangelands and fully considering the impact of topography are important to accurately analyze the effects of climate change on vegetation phenology.

Effects of Enclosure on Plant and Soil Nutrients in Different Types of Alpine Grassland

Enclosure is one of the most widely used management tools for degraded alpine grassland on the northern Tibetan Plateau, but the responses of different types of grassland to enclosure may vary, and research on these responses can provide a scientific basis for improving ecological conservation. This study took one site for each of three grassland types(alpine meadow, alpine steppe and alpine desert) on the northern Tibetan Plateau as examples, and explored the effects of enclosure on plant and soil nutrients by comparing differences in plant community biomass, leaf-soil nutrient content and their stoichiometry between samples from inside and outside the fence. The results showed that enclosure can significantly increase all aboveground biomass in these three grassland types, but it only increased the 10–20 cm underground biomass in the alpine desert. Enclosure also significantly increased the leaf nutrient content of the dominant plants and contents of total nitrogen(N), total potassium(K), and organic carbon(C) in 10–20 cm soil in alpine desert, thus changing the stoichiometry between C, N and P(phosphorus). However, enclosure significantly increased only the N content of dominant plant leaves in alpine steppe, while other nutrients and stoichiometries of both plant leaves and soil did not show significant differences in alpine meadow and alpine steppe. These results suggested that enclosure has differential effects on these three types of alpine grasslands on the northern Tibetan Plateau, and the alpine desert showed the most active ecological conservation in the responses of its soil and plant nutrients.

Effects of the hummock-depression microhabitat on plant communities of alpine marshy meadows in the Yellow River Source Zone,China

Our objectives are to examine the effects of hummock-depression spatial heterogeneity on plant communities and soil properties,and to understand the process of maintaining and adjusting microtopography-mediated hydrological inputs and their spatial fluctuations that produce obvious microhabitats.We set up 36 plots(1 m×1 m)and sampled 45 plant and 225 soil samples in flooded(FH)and non-flooded hummocks(NFH)and depressions of the marshy,and the surrounding non-wetland meadows as well as in the Yellow River Source Zone,west China.We evaluated whether the alpine marshy wetland has a fertile island effect by the comparison method.Our results show that hummock presence can increase the spatial heterogeneity of the microhabitat and promote the plant diversity and soil fertility of the Kobresia tibetica community.Plant height,coverage,above-ground biomass,species richness and diversity were significantly higher in the FH and NFH microhabitat than in the areas between hummocks and surrounding non-wetland meadows.Compared with broad alpine meadows,the hummock-depression complex provided a microhabitat favorable to the growth of Cyperaceae.In the 0-50 cm soil layer,the closer the soil layer was to the ground surface,the higher its soil organic carbon and total nitrogen contents.Thus,in deeper layers,the gap between soil nutrients in wetland hummock-depression microhabitat and in the surrounding alpine meadows becomes smaller.Hence,the wetland hummock-depression microhabitat formed a fertile island pattern.Therefore,these results contribute toward improving our understanding of ecosystem restoration in alpine marshy meadows.

The uptake diversity of soil nitrogen nutrients by main plant species in Kobresia humilis alpine meadow on the Qinghai-Tibet Plateau

We studied the uptake of ammonium, nitrate, and a variety of amino acids by alpine plant species in the Kobresia humil alpine meadow ecosystem in situ. We examined the extent of niche separation in uptake of N source by different plant species in alpine communities, and investigated the contribution of symbiotically fixed N to the total N in alpine meadow. The results are （1） δ15N natural abundance values of 13 plant species lie between -2.680‰ and 5.169‰, and the scope is 7.849‰. （2） Le- guminous plants, such as Trigonella ruthenica, Gueldenstaedtia diversiffolia, and Oxytyopis ochrocephala, and non-legumi- nous plant Gentiana straminea uptake low amounts of 15N labeled ammonium, nitrate, glycine or aspartate in soil. （3） As far as the plant uptake of organic N is concerned, Kobresia humilis, Poa pratensis, and Gentiuna spathutifolta can effectively uptake organic nitrogen, and about 37%-40% of the nitrogen of these species comes from soil organic nitrogen sources （such as glycine and aspartate）. Stipa aliena can effectively uptake nitrate, and 60% of its nitrogen comes from soil nitrate. Potentilla anserina, Poa pratensis, and Thalictrum alpinum can effectively absorb ammonium in comparason to other plant species in the meadow, and about 25%-27% of the nitrogen in these plants comes from soil ammonium. （4） The contribution of leguminous fixed N to total N is 7.48%-9.26% in Kobresia humilis alpine meadow. （5） These data show many plant species of alpine meadow may effectively utilize dissolved organic nitrogen such as amino acids, and these plants have diverse ways to uptake soil nitrogen in alpine meadows. Based on the results we can partly explain why there are abundant biodiversities and how plants at alpine habitat utilize the limited soil N sources.

Vegetation physiological parameter setting in the Simple Biosphere model 2(SiB2) for alpine meadows in the upper reaches of Heihe river

Land surface process modeling of high and cold area with vegetation cover has not yielded satisfactory results in previous applications. In this study, land surface energy budget is simulated using a land surface model for the A'rou meadow in the upper-reach area of the Heihe River Basin in the eastern Tibetan Plateau. The model performance is evaluated using the in-situ observations and remotely sensed data. Sensible and soil heat fluxes are overestimated while latent heat flux is underestimated when the default parameter setting is used. By analyzing physical and physiological processes and the sensitivities of key parameters, the inappropriate default setting of optimum growth and inhibition temperatures is identified as an important reason for the bias. The average daytime temperature during the period of fastest vegetation growth(June and July) is adopted as the optimum growth temperature, and the inhibition temperatures were adjusted using the same increment as the optimum temperature based on the temperature acclimation. These adjustments significantly reduced the biases in sensible, latent, and soil heat fluxes.