Haibei Alpine Meadow Research Articles

高寒草地不同径级根形态对围封年限的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 高寒草地不同径级根形态对围封年限的响应 DOI: 10.5846/stxb202012203234 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 甘肃省自然科学基金重大项目(18JR4RA002);中国科学院内陆河流域生态水文重点实验室开放基金项目(KLEIRB-ZS-16-01);寒区旱区陆地表面过程及气候变化重点实验室开放基金项目(LPCC2018008) The response of the root morphology under different diameter classes to grazing exclosure duration in alpine grassland Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以根径级表征根系形态结构,可以反映植物资源利用和生物量分配状况。研究高寒草地不同径级根形态,对了解地下碳分配、水分和养分吸收及生产力具有重要意义。围封被认为是防治草地退化的最有效措施之一,但目前有关围封年限对不同径级根形态影响的研究还极度缺乏,以致无法确定有利于根生态效益,即资源吸收利用能力最大化的围封年限。以位于青海省海北台站围封5、13、22、39 a的高寒草地为研究对象,季节性放牧草地为对照,探讨围封年限对不同径级根形态(包括根长、根表面积和根尖数)的影响。结果表明:在0-15 cm土层中,径级小于0.5 mm时,围封13 a的根尖数显著高于围封5 a的草地,其对应的生物量也最大;径级小于0.6 mm时,围封13 a的根长和根表面积均显著高于围封5 a和放牧草地,且其对应的生物量也达最大;径级大于0.5 mm时,各草地之间的根尖数均无差异;径级大于0.6 mm时,围封39 a的根长和根表面积均显著高于放牧草地,且其对应的生物量最大。在15-30 cm土层中,各径级下,围封5 a的根长、根表面积和根尖数均显著大于围封39 a和放牧草地,但其对应的生物量在围封13 a时达最大。土壤硝态氮、地下生物量是影响各径级根形态的主要因素。研究结果表明,研究区的根生态效益与围封年限有关,13 a时的效果较好,更长时间的围封不再明显提高这一效益。 Abstract:The diameter class characterizes the morphological structure of the root system and reflects the state of resource use and biomass allocation. The study on root morphology at different diameter classes in alpine grasslands is important for understanding subsurface carbon allocation, water and nutrient uptake and productivity. Grazing exclosure (GE) was considered one of the most effective measures to combat grassland degradation. But there are few studies on the effects of GE duration on root morphology at different diameter classes, making it impossible to determine a suitable GE duration that can maximise the ecological benefits of roots such as the capacity of resource use. The root morphology patterns, including root length, root surface area, and the number of root tip of the 5, 13, 22, and 39 a exclosure were investigated in alpine grassland at the Haibei alpine meadow ecosystem research station in Qinghai Province, with nearby seasonal grazing grassland as a control. The results showed that at the 0-15 cm soil layer, the number of root tip under the 13 a GE was significantly higher than under the 5 a GE at a diameter class of less than 0.5 mm, and its corresponding biomass was the greatest. Root length and root surface area under the 13 a GE were significantly higher than under the 5 a GE and grazing grassland at a diameter class of less than 0.6 mm, and its corresponding biomass was also the greatest. However, at a diameter class of greater than 0.5 mm, there was no difference in the number of root tips among different grasslands. At a diameter class of greater than 0.6 mm, values of root length and root surface area under the 39 a GE were significantly higher than under seasonal grazing grassland, and its corresponding biomass also reached the greatest value. At the 15-30 cm soil layer, root length, root surface area and the number of root tip under the 5 a GE were significantly greater than under the 39 a GE and seasonal grazing grassland, but their corresponding diameter biomass reached maximum in the 13 as of GE. The soil nitrate nitrogen and the below-ground biomass were the main factors affecting root morphology at each diameter level. The results from the study suggest that the root ecological benefit is related to the duration of GE and its value is relatively higher under the 13 a GE, with longer duration of GE no longer significantly increasing this benefit. 参考文献 相似文献 引证文献

UV-B Radiation Effects on the Alpine Plant Kobresia humilis in a Qinghai-Tibet Alpine Meadow.

Enhanced UV-B radiation resulting from stratospheric ozone depletion has been documented both globally and on the Qinghai-Tibet Plateau in China. The response of Kobresia humilis, an important alpine meadow plant species, to enhanced UV-B radiation was experimentally investigated at the Haibei Alpine Meadow Ecosystem Research Station (37°29'-37°45' N, 101°12'-101°23' E; alt. 3200 m). K. humilis was exposed to UV-B radiation including ambient UV-B and enhanced UV-B (simulating a 14% reduction in the ozone layer) in a randomized design with three replications of each treatment. Enhanced UV-B radiation resulted in a significant increase of both leaf area and fresh weight chlorophyll and carotenoid but had no effect on UV-B absorbing pigments. Similarly, enhanced UV-B radiation did not significantly change the photosynthetic O2 elevation rate while leaf thickness, width, and length significantly increased (p < 0.01). The enhanced UV-B radiation was associated with 2-3 days earlier flowering and a larger number of flowers per spikelet. The enhanced UV-B generally resulted in larger leaves and more flowers but earlier phenology. In summary, these findings suggest that alpine species of K. humilis have adapted to the strong solar UV-B radiation intensity presented on the Qinghai-Tibet Plateau, but the interspecies differences and their influence on trophic level should be more concerning.

Calibration of Near-Infrared Spectra for Phosphorus Fractions in Grassland Soils on the Tibetan Plateau

Soil phosphorus (P) is essential for plant growth and influences biological processes. Determining the amounts of available P to plants has been challenging, and many different approaches exist. The traditional Hedley sequential extraction method and its subsequent modification are applied to determine different soil P forms, which is critical for understanding its dynamics and availability. However, quantifying organic and inorganic P (Po & Pi) in different extracts is labor-intensive and rarely used with large sample numbers. As an alternative, near-infrared spectroscopy (NIRS) has been employed to determine different P fractions at reasonable costs in a short time. This study aimed to test whether the analysis of P fractions with NIRS is an appropriate method to disentangle the effects of P limitation on high-altitude grassland ecosystems, particularly with fertilizer amendments. We explored NIRS in soils from the grassland soil samples on the northern Tibetan Plateau. First, we extracted the P fractions of 191 samples from the Haibei Alpine Meadow Ecosystem Research Station at four depth increments (0–10 cm, 10–20 cm, 20–40 cm, and 40–70 cm), including nutrient additions of nitrogen (N) and P. We compared the results of the Hedley extraction with the laboratory-based NIRS model. The fractionation data were correlated with the corresponding NIRS soil spectra; the coefficient of determination (R2) of the NIRS calibrations to predict P in P fractions ranged between 0.12 and 0.90; the ratio of (standard error of) prediction to the standard deviation (RPD) ranged between 1.07 and 3.21; the ratio of performance to inter-quartile distance (RPIQ) ranged from 0.3 to 4.3; and the model prediction quality was higher for Po than Pi fractions, and decreased with fertilizer amendment. However, the external-validation results were not precise enough for the labile P fractions (RPD < 1.4) due to the limited number of samples. The results indicate that using NIRS to predict the more stable P pools, combined with Hedley fractionation focusing on the labile P pool, can be a promising approach for soils in alpine grasslands on the Tibetan Plateau.

Effects of predation risk on behavior, hormone levels, and reproductive success of plateau pikas

AbstractPredation is a strong selective force that affects animal population dynamics either through direct killing or predation risk effects. Although recent empirical research has shown that the non‐consumptive effect of predator risk on prey dynamics can be as large (or even larger) as direct effects, little is known about the strength of predation risk effects in wild populations or the physiological mechanisms that mediate them. Here, we test both the predator‐sensitive food hypothesis and predation‐stress hypothesis in a single system by investigating activity budgets, stress/sex hormone levels, and demography of plateau pikas (Ochotona curzoniae) and their predators in Haibei Alpine Meadow Ecosystem Research Station of the Chinese Academy of Science. During the study period (2009 and 2010), plateau pikas experienced various predation pressures due to many predators being poisoned in 2010. In the year of high predator numbers, pikas spent more time on vigilant duty and less time foraging and they also showed higher plasma corticosterone levels and lower plasma estradiol and testosterone levels. Reproductive success and male with developed testes also reduced in the year of higher predation risk. In general, our results support both the predator‐sensitive food and predation‐stress hypothesis. Predator‐induced risk affects prey reproduction by changes in feeding patterns and stress physiology.

Changes in photosynthesis of alpine plant Saussurea superba during leaf expansion

The native alpine plant Saussurea superba is widely distributed in Qinghai–Tibetan Plateau regions. The leaves of S. superba grow in whorled rosettes, and are horizontally oriented to maximize sunlight exposure. Experiments were conducted in an alpine Kobresia humilis meadow near Haibei Alpine Meadow Ecosystem Research Station (37°29′–37°45′N, 101°12′–101°33′E; alt. 3200 m). Leaf growth, photosynthetic pigments and chlorophyll fluorescence parameters were measured in expanding leaves of S. superba. The results indicate that leaf area increased progressively from inner younger leaves to outside fully expanded ones, and then slightly decreased in nearly senescent leaves, due to early unfavorable environmental conditions, deviating from the ordinary growth pattern. The specific leaf area decreased before leaves were fully expanded, and the leaf thickness was largest in mature leaves. There were no significant changes in the content of chlorophylls (Chl) and carotenoids (Car), but the ratios of Chl a/b and Car/Chl declined after full expansion of the leaves. The variation of Chl a/b coincided well with changes in photochemical quenching (qP) and the fraction of open PSII reaction centers (qL). The maximum quantum efficiency of PSII photochemistry after 5 min dark relaxation (F(v)/F(m)) continuously increased from younger leaves to fully mature leaves, suggesting that mature leaves could recover more quickly from photoinhibition than younger leaves. The light-harvesting capacity was relatively steady during leaf expansion, as indicated by the maximum quantum efficiency of open PSII centers (\(F_{\text{v}}^{{\prime }}\)/\(F_{\text{m}}^{{\prime }}\)). UV-absorbing compounds could effectively screen harmful solar radiation, and are a main protection way on the photosynthetic apparatus. The decline of qP and qL during maturation, together with limitation of quantum efficiency of PSII reaction centers (L(PFD)), shows a decrease of oxidation state of QA in PSII reaction centers under natural sunlight. Furthermore, light-induced (ΦNPQ) and non-light-induced quenching (ΦNO) were consistent with variation of L(PFD). It is concluded that the leaves of S. superba could be classified into four functional groups: young, fully expanded, mature, and senescent. Quick recovery from photoinhibition was correlated with protection by screening pigments, and high level of light energy trapping was correlated with preservation of photosynthetic pigments. Increasing of ΦNPQ and ΦNO during leaves maturation indicates that both thermal dissipation of excessive excitation energy in safety and potential threat to photosynthetic apparatus were strengthened due to the declination of qP and qL, and enhancement of L(PFD).

Urea addition and litter manipulation alter plant community and soil microbial community composition in a Kobresia humilis meadow

Overgrazing and climate change strongly affect alpine meadows by decreasing the plant community biomass and deteriorating the soil environment. To understand how the plant community and soil microbial community structure respond to grazing and N deposition, we conducted an experiment to remove or maintain the plant litter under the chronic addition of N in the Haibei Alpine Meadow in 2005. The experiment included four treatments: added N (+N, 20 g m−2) with the litter removed (LR), +N with the litter left intact (LI), LI without N addition (−N), and LR with −N. Soil samples were collected at depths of 0–10 and 10–20 cm, and the following parameters were measured: 1) aboveground biomass (AGB) and litter biomass and 2) microbial community composition and content. Overall, the AGB and litter biomass significantly increased by 45.85% and 50.42% in response to N addition, whereas litter removal increased the AGB by 52.96%. The addition of urea N significantly decreased the PLFA content of the bacterial, gram-positive (G+), gram-negative (G−) at a soil of 0–10 cm in the LI and LR treatments by 64.87%, 61.82%, 76.07% and 64.86%, 53.02%, 51.44%, respectively. However, the PLFA content of the bacterial increased from 37.09 to 53.54 nmol g−1 and from 37.09 to 62.05 nmol g−1 at a depth of 10–20 cm for the +N + LI and +N + LR treatments compare to the LR+(−)N treatment, respectively. In addition, the total PLFAs in the LR+(−)N treatment significantly increased by 50.61% at a depth of 0–10 cm but decreased from 121.62 to 42.31 nmol g−1 at a depth of 10–20 cm relative to the LI+(−)N treatment. Using PLFA as a biomarker, we detected that G− bacteria and total PLFA generally increased with increasing soil depth in the +N plots. However, the content of G− was the highest at a depth of 0–10 cm and the lowest at a depth of 10–20 cm in the LR plots. The modification of soil microbial biomass at a depth of 0–10 cm was induced by the bottom-up effect of changes in soil nutrient contents and using ability, which were driven by N addition and litter manipulation. Thus, different soil depths with different soil nutrient conditions resulted in a strong microbial community composition gradient.

Nitrogen deposition impacts on the amount and stability of soil organic matter in an alpine meadow ecosystem depend on the form and rate of applied nitrogen

SummaryThe effects of atmospheric nitrogen (N) deposition on carbon (C) sequestration in terrestrial ecosystems are controversial. Therefore, it is important to evaluate accurately the effects of applied N levels and forms on the amount and stability of soil organic carbon (SOC) in terrestrial ecosystems. In this study, a multi‐form, small‐input N addition experiment was conducted at the Haibei Alpine Meadow Ecosystem Research Station from 2007 to 2011. Three N fertilizers, NH4Cl, (NH4)2SO4 and KNO3, were applied at four rates: 0, 10, 20 and 40 kg N ha−1 year−1. One hundred and eight soil samples were collected at 10‐cm intervals to a depth of 30 cm in 2011. Contents and δ13C values of bulk SOC were measured, as well as three particle‐size fractions: macroparticulate organic C (MacroPOC, > 250 µm), microparticulate organic C (MicroPOC, 53–250 µm) and mineral‐associated organic C (MAOC, < 53 µm). The results show that 5 years of N addition changed SOC contents, δ13C values of the bulk soils and various particle‐size fractions in the surface 10‐cm layer, and that they were dependent on the amounts and forms of N application. Ammonium‐N addition had more significant effects on SOC content than nitrate‐N addition. For the entire soil profile, small additions of N increased SOC stock by 4.5% (0.43 kg C m−2), while medium and large inputs of N decreased SOC stock by 5.4% (0.52 kg C m−2) and 8.8% (0.85 kg C m−2), respectively. The critical load of N deposition appears to be about 20 kg N ha−1 year−1. The newly formed C in the small‐input N treatment remained mostly in the > 250 µm soil MacroPOC, and the C lost in the medium or large N treatments was from the > 53 µm POC fraction. Five years of ammonium‐N addition increased significantly the surface soil POC:MAOC ratio and increased the instability of soil organic matter (SOM). These results suggest that exogenous N input within the critical load level will benefit C sequestration in the alpine meadow soils on the Qinghai–Tibetan Plateau over the short term.

增氮对青藏高原东缘高寒草甸土壤甲烷吸收的早期影响

PDF HTML阅读 XML下载 导出引用 引用提醒 增氮对青藏高原东缘高寒草甸土壤甲烷吸收的早期影响 DOI: 10.5846/stxb201208281217 作者: 作者单位: 中国科学院大学,中国科学院地理科学与资源研究所,中国科学院大学,中国科学院大学,中国科学院大学,中国科学院地理科学与资源研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金(31070435,41071166,31130009);中国科学院知识创新工程重要方向项目(Y225017EA2);国家重点基础研究发展计划项目(2010CB833502,2010CB833501);中国科学院地理科学与资源研究所"秉维"优秀青年人才基金(2011RC202);中国科学院战略性先导科技专项(XDA05050600)资助 The early effects of nitrogen addition on CH4 uptake in an alpine meadow soil on the Eastern Qinghai-Tibetan Plateau Author: Affiliation: University of Chinese Academy of Sciences,Institute of Geographical Sciences and Natural Resources Research,Chinese Academy of Sciences,Graduate University of Chinese Academy of Sciences,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:研究大气氮沉降对青藏高原高寒草甸土壤CH4吸收的影响,对于揭示氮素调节土壤CH4吸收的机制和评价氮沉降增加背景下大气CH4收支平衡至关重要。通过构建多形态、低剂量的增氮控制试验,测定土壤CH4净交换通量和相关土壤理化性质,分析高寒草甸土壤CH4通量变化特征及其主要驱动因子。研究结果表明:自然状态下高寒草甸土壤是大气CH4汇,CH4平均吸收量为(35.40±1.92)μg·m-2·h-1。土壤CH4吸收主要受水分驱动,其次为土壤NH4+-N和NO3--N含量。NH4+-N抑制CH4吸收,NO3--N促进CH4吸收;不同剂量氮素输入对土壤CH4吸收影响也不尽相同,低氮处理促进土壤CH4吸收,而中氮和高氮处理抑制土壤CH4吸收。结果显示青藏高原高寒草甸土壤是重要的大气CH4汇,在未来大气氮沉降加倍的情景下CH4汇功能增强,但当氮沉降量增加两倍以上时CH4汇功能将会减弱。 Abstract:The increase in atmospheric nitrogen (N) deposition caused by human activities significantly changes carbon cycling and the carbon budget in terrestrial ecosystems. Unsaturated soil is a unique biological methane (CH4) sink, accounting for about 5% of all atmospheric CH4 absorption. Alpine meadow is a typical N-limited ecosystem in which the soil microorganisms and plants have adapted to the N poor environment so that long-term slow N input will change the carbon cycle process, structure and function of this fragile ecosystem. Therefore, it is crucial and helpful to explore the mechanisms responsible for the responses of soil CH4 uptake to exogenous N input. In 2007, a multi-form, low-level N addition experiment was conducted at the Haibei Alpine Meadow Ecosystem Research Station on the Qinghai-Tibetan Plateau. Three N fertilizers; NH4Cl, (NH4)2SO4, and KNO3 were added at four rates; control (0 kgN·hm-2·a-1), low N (10 kgN·hm-2·a-1), medium N (20 kgN·hm-2·a-1), and high N (40 kgN·hm-2·a-1). Each N treatment contained three replicates, making a total of 36 plots. During the growing season (May to October), soil CH4 fluxes were monitored weekly by the static chamber-gas chromatograph technique. Simultaneously to the soil CH4 flux measurements, soil temperature and soil moisture were also recorded at 10 cm depth. In addition, the soil ammonium, nitrate and dissolved organic carbon contents as well as the pH were measured monthly to examine the key driving factors of soil CH4 uptake. The results showed that: (1) N addition significantly changed the soil moisture content. Both low and high levels of N addition tended to consume soil moisture, whereas a medium level of N input was favorable to maintaining soil moisture, which mainly depended on the soil moisture balance of precipitation, soil evaporation and plant transpiration. (2) N addition significantly changed soil NH4+-N, but did not affect the soil NO3--N pool. As the most vulnerable part of the ecosystem to a change in N forms, plants preferentially absorbed NO3--N rather than NH4+-N and added NO3--N was absorbed more strongly by plants than NH4+-N. Therefore, accumulation of soil NH4+-N caused by N addition was more significant than that of soil NO3--N. Nitrogen addition did not significantly decrease the soil pH values. (3) Soil-dissolved organic carbon strongly fluctuated within the growing season. After accumulating over the non-growing season, dissolved organic carbon content was at a maximum in May, and then continued to decrease until October because of microbial consumption. (4) Soil CH4 uptake was mainly driven by soil moisture, followed by soil NH4+-N and NO3--N contents. Ammonium fertilizer addition inhibited soil CH4 uptake, where as nitrate fertilizer promoted it. This research suggests that alpine meadow soils are an atmospheric CH4 sink and that N addition can significantly affect CH4 uptake in the short term. Low N addition can promote CH4 uptake from alpine meadow soil, while medium and high N deposition inhibits CH4 uptake and decreases the atmospheric CH4 sink. The critical level of atmospheric N deposition is about 20 kgN/hm2·a if the ambient N deposition rate is considered. 参考文献 相似文献 引证文献

The Flow Processes of Carbon Fixation Value of Typical Ecosystems

Based on data from ChinaFLUX this study analyzed the daily value flow processes of carbon fixation, monthly value distribution, and daily accumulative processes in a year of two kinds of typical forest, two kinds of grasses and a farmland. The results showed that the annual value of carbon fixation of these ecosystems was different, and flow processes and cumulative processes followed different trends over a year. The sequence of the five kinds of ecosystems based on the annual value of carbon fixation from largest to smallest was Yucheng warm temperate agriculture ecosystem (Yucheng), Qianyanzhou subtropical artificial coniferous forest ecosystem (Qianyanzhou), Changbai Mountain temperate mixed coniferous broad-leaved forest ecosystem (Changbaishan), Haibei alpine meadow ecosystem (Haibei)and Dangxiong alpine meadow ecosystem (Dangxiong). Variability in the daily and monthly carbon fixation at Qianyanzhou was the smallest, followed by Changbaishan, Yucheng, Dangxiong and Haibei. The cumulative processes of daily carbon fixation for the five kinds of ecosystems were well fitted to cubic curves.

典型草地的土壤保持价值流量过程比较

内蒙古温带草原和海北高寒草甸的土壤侵蚀以风力侵蚀为主。利用改良的风力侵蚀模型,比较分析了这两类草地生态系统土壤保持价值日流量过程和累积过程。结果表明,风力侵蚀条件下,草地生态系统的土壤保持服务是离散的,不连续的,与风速和植被盖度直接相关。土壤保持价值构成以保持土壤养分为主。内蒙古温带草原的年潜在侵蚀量和年现实侵蚀量都高于海北高寒草甸。但是,内蒙古温带草原的土壤保持年价值高于海北高寒草甸,是海北高寒草甸年价值的7倍。春季和秋季是内蒙古温带草原潜在侵蚀量、现实侵蚀量和土壤保持量最高的两大季节。海北高寒草甸的潜在侵蚀量和现实侵蚀量主要分布在12月份到翌年4月份,土壤保持量主要分布在春季和夏季。;Grassland is the largest land resources by area in China. It plays an important role in food production, carbon fixation and sequestration, O₂ release, soil and water conservation, water supply, nutrient recycling, entertainment, and biodiversity sustaining, among which, soil conservation is one of the most essential services delivered by grassland ecosystem. There have been few studies specially focusing on soil conservation value of grassland ecosystem till now, although soil conservation has historically been emphasized in the practice of grassland management, resulting in limited understanding about the mechanism of soil conservation of grassland especially at spot scale. Therefore, the dynamic flow processes of soil conservation value of grassland at spot scale are urgent to be researched. In the context, the study targeted at the dynamic processes of soil conservation of two kinds of typical grasslands: Neimenggu Temperate Grassland and Haibei Alpine Meadow. Due to that soil erosion of both the selected grassland ecosystems was mainly caused by wind, on the basis of simplicity and scientificity, we chose the Pasak wind erosion model and improved it through the input of factors to assess wind induced soil erosion. The accuracy of the model was tested by the existing research results of other scientists. Related data were from Chinese Ecosystem Research Net (CERN).The soil conserved by grassland was the subtraction of soil eroded under vegetation coverage the actual soil erosion, from the soil eroded without vegetation the potential soil erosion. The soil conservation value was calculated using the method of shadow price and opportunity cost. The results showed that the soil conservation service supplied by grassland ecosystems was discrete, which was highly related to the wind velocity and vegetation coverage. The annual soil conservation value of Neimenggu Temperate Grassland was at 1.06×10⁴ ￥/hm²,while that of Haibei Alpine Meadow was at 1520 ￥/hm². The soil nutrient conservation was dominant in soil conservation service, contributing as high as 99% to the total soil conservation value. Both the potential and actual soil erosion of Neimenggu Temperate Grassland was higher than those of Haibei Alpine Meadow in a year. And the annual soil conservation value of Neimenggu Temperate Grassland was far bigger, 7 times as much as that of Haibei Alpine Meadow. The soil conservation service of grasslands was distributed differently in each season. The potential and actual soil erosion and the soil conservation in Neimenggu Temperate Grassland mainly happened in spring and autumn, while in Haibei Alpine Meadow the potential and actual soil erosion mainly occurred during December to April in the next year and the soil conservation in spring and summer. It was concluded that the soil conservation value of grassland has a clear changing pattern during a year with wind velocity and vegetation coverage. The high soil conservation value of grasslands under wind, especially in the sandy areas, calls upon us to take efforts to save grassland from destruction and keep grassland healthy.

海北高寒草地生態系研究ステーション( 野外研究サイトから(17))

海北高寒草地生態系研究ステーション( 野外研究サイトから(17))

Male reproductive success in plateau pikas ( Ochotona curzoniae): A microsatellite analysis

In many social species, competition and cooperation between group members may lead to a large variance in reproductive success among individuals, especially for adult male. From April to August 2002, we studied the adult male reproductive success of plateau pikas in Haibei Alpine Meadow Ecosystem Research Station, Chinese Academy of Science, using microsatellite analysis of paternity, mark-recapture and behavioral observations. Our result indicated that the reproductive success of adult males had a large variance. Its average was 6 individuals and range was from 0 to 13 individuals. One-third of males sired 63.22% offspring. There was a hierarchy system in polygynandrous families. Although the reproductive success of dominant males was higher than that of subordinate males, subordinate males still play an important role in the reproductive success of the population.

Study on the UV-A and UV-B Changes and Their Correlations with Meteorological Factors in the Haibei Alpine Meadow in the Qilian Mountains

Based on the one-year data observed in the Haibei alpine meadow in the Qilian Mountains located in northeast of the Qinghai-Tibetan Plateau,in this study the UV-A and UV-B changes and their correlations with meteorological factors are analyzed,and the UV-A and UV-B are modeled using the data of some meteorological factors.The results reveal that the UV-A and UV-B changes are significant,their maximum and minimum values occur in June and December,and their accumulative sums are 138.11 MJ/m2 and 35.14 MJ/m2,respectively.There are also the significant daily and annual changes of the ratios of UV-A and UV-B in DR(direct radiation).In daily change,their ratios are the highest at noon and decrease to their minimum values in early morning and at night.In annual change,their maximum and minimum values occur in summer and winter,and their annual mean values are 2.17% and 0.54%,respectively.There are the significant correlations between the UV-A and UV-B and many meteorological factors,but it can not be considered that these factors affect directly the UV-A and UV-B.According to the factors affecting DR,soil temperature at 5 cm in depth can be regarded as a prediction factor to develop the ten-day correlative simulation equation affecting UV-A and UV-B,which is very significant at the level of dual linear regression.

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 importance of species composition, species richness, the type of different growth forms, and plant biomass 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, herbaceous 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 decrease from 13196.96+/-719.69 g/m(2) in the sedge-dominated K. tibetica swamp to 2869.58+/-147.52 g/m(2) in the forb and sedge dominated K. pygmaea meadow, and to 2153.08+/-141.95 g/m(2) in the forbs and grasses dominated K. humilis along with the increase of altitude. The vertical distribution of belowground 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 positively correlated to soil organic matter and soil total nitrogen (P<0.05). This suggests that the distribution of biomass coincided with soil moisture and edaphic gradient in alpine meadows.

Independence of alpine meadow plants from soil organic matter for nitrogen supply: evidence from stable nitrogen isotopes

Stable nitrogen isotope signatures of major sources of mineral nitrogen (mineralization of soil organic nitrogen, biological N2 fixation by legumes, annual precipitation and plant litter decomposition) were measured to relatively define their individual contribution to grass assimilation at the Haibei Alpine Meadow Ecosystem, Qinghai, China. The results indicated that δ15N values (−2.40 ‰ to 0.97 ‰) of all grasses were much lower than those of soil organic matter (3.4±0.18 ‰) and mineral nitrogen (ammonium and nitrate together, 7.8±0.57 ‰). Based on the patterns of stable nitrogen isotopes, soil organic matter (3.4±0.18 ‰), biological N2 fixation (0 ‰), and precipitation (−6.34±0.24 ‰) only contributed to a small fraction of nitrogen requirements of grasses, but plant litter decomposition (−1.31±1.01 ‰) accounted for 67 %.

Stability of alpine meadow ecosystem on the Qinghai-Tibetan Plateau

The meadow ecosystem on the Qinghai-Tibetan Plateau is considered to be sensitive to climate change. An understanding of the alpine meadow ecosystem is therefore important for predicting the response of ecosystems to climate change. In this study, we use the coefficients of variation (Cv) and stability (E) obtained from the Haibei Alpine Meadow Ecosystem Research Station to characterize the ecosystem stability. The results suggest that the net primary production of the alpine meadow ecosystem was more stable (Cv = 13.18%) than annual precipitation (Cv = 16.55%) and annual mean air temperature (Cv = 28.82%). The net primary production was insensitive to either the precipitation (E = 0.0782) or air temperature (E = 0.1113). In summary, the alpine meadow ecosystem on the Qinghai-Tibetan Plateau is much stable. Comparison of alpine meadow ecosystem stability with other five natural grassland ecosystems in Israel and southern African indicates that the alpine meadow ecosystem on the Qinghai-Tibetan Plateau is the most stable ecosystem. The alpine meadow ecosystem with relatively simple structure has high stability, which indicates that community stability is not only correlated with biodiversity and community complicity but also with environmental stability. An average oscillation cycles of 3–4 years existed in annual precipitation, annual mean air temperature, net primary production and the population size of consumers at the Haibei natural ecosystem. The high stability of the alpine meadow ecosystem may be resulting also from the adaptation of the ecosystem to the alpine environment.

A stable carbon isotopic approach for understanding the CO 2 flux at the Haibei Alpine Meadow Ecosystem—A simple model

Although respiration of organisms and biomass as well as fossil fuel burning industrial production are identified as the major sources, the CO 2 flux is still unclear due to the lack of proper measurements. A mass-balance approach that exploits differences in the carbon isotopic signature ( δ 13C) of CO 2 sources and sinks was introduced and may provide a means of reducing uncertainties in the atmospheric budget. δ 13C measurements of atmospheric CO 2 yielded an average of −10.3‰ relative to the Peedee Belemnite standard; soil and plants had a narrow range from −25.09‰ to −26.51‰ and averaged at −25.80‰. Based on the fact of steady fractionation and enrichment during respiration of mitochondria, we obtained the emission of CO 2 of 35.451 mol m −2 a −1 and CO 2 flux of 0.2149 μmol m −2 s −1. The positive CO 2 flux indicated the Haibei Alpine Meadow Ecosystem a source rather than a sink. The mass-balance model can be applied for other ecosystem even global carbon cycles because it neglects the complicated process of carbon metabolism, however just focuses on stable carbon isotopic compositions in any of compartments of carbon sources and sinks.

Observation and modeling for terrestrial processes in alpine meadow

The water-heat transfer process between land and atmosphere in Haibei alpine meadow area has been systematically observed. A multi-layer coupling model for land-atmosphere interaction was presented with special attention paid to the moisture transfer in leaf stomata under unsaturated condition. A profound investigation on the physical process of turbulent transfer inside the vegetation has been performed with a revised formula of water absorption for root system. The present model facilitates the study of vertically distributed physical variables in detail. Numerical simulation was conducted according to the transfer process of Kinesia humility meadow in the area of Haibei Alpine Meadow Ecosystem Station, CAS. The calculated results agree well with observation.

Photosynthesis of Saussurea superba and Gentiana straminea is not reduced after long-term enhancement of UV-B radiation

Experiments were conducted in an alpine Kobresia humilis meadow near Haibei Alpine Meadow Ecosystem Research Station (37°29′–37°45′N, 101°12′–101°33′E; altitude 3200 m). Effects of enhanced ultraviolet-B (UV-B) radiation on photosynthesis of the alpine plants of Saussurea superba and Gentiana straminea were investigated. Both species were exposed to a UV-B BE density at 15.80 kJ m −2 per day, simulating nearly 14% ozone (O 3) reduction during the plant growing season. Neither photosynthetic CO 2 uptake rate nor photosynthetic O 2 evolution rate were decreased after a long period of enhanced UV-B radiation treatment. On the contrary, there was a tendency to increase of both parameters in both species. The photosynthetic pigments were also increased, when expressed on a leaf area basis. UV-B absorbing compounds, detected by the absorbance values at 300 mm, had a tendency to increase in both species after enhanced UV-B radiation. After long-term exposure of plants to enhanced UV-B radiation, leaf morphology was also affected. Leaf thickness in both S. superba and G. straminea were increased significantly ( P<0.001). This supports our hypothesis that the increase of leaf thickness in both species after long-term exposure of enhanced UV-B radiation could compensate for the photodestruction of photosynthetic pigments when light passes through the leaf. Therefore, photosynthesis is not reduced in either species when expressed on leaf area basis.