高寒金露梅灌丛草甸植被反射率特征     

李英年  赵亮  赵新全  王勤学  杜明远  张法伟 《山地学报》2009,27(3)

根据祁连山海北高寒金露梅灌丛草甸2004年观测的太阳总辐射和反射辐射资料,分析了高寒金露梅灌丛草甸植被反射率（A）的变化特征。结果表明,金露梅灌丛草甸A在日间或一年间均表现出＂U＂型变化规律,晴天、昙天和阴云天气状况下的早晚略有差异,中午前后的A值三者无明显差异。季节不同下垫面性质不同的影响,A的分布不同。海北高寒金露梅灌丛草甸A的月平均在植物生长季内5～9月为0.15,植物非生长季的10月～翌年4月为0.20,年平均A为0.18。  相似文献   

地基激光雷达灌丛化草原小叶锦鸡儿生物量估算     

刘晓亮  隋立春  白永飞  赵旦  赵玉金  刘艳书  翟秋萍 《遥感学报》2020,24(7):894-903

小叶锦鸡儿是内蒙古灌丛化草原中最具代表性的景观植物,准确估算小叶锦鸡儿灌丛的地上生物量对研究灌丛化草原生态系统、监测草原灌丛化程度具有重要意义。地基激光雷达TLS(Terrestrial Laser Scanning)可通过获取高密度点云数据准确估算灌木体积,被广泛应用于反演灌木生物量,但在灌丛化草原中尚未得到有效应用。本研究首先在中国科学院灌丛化草地植被恢复试验区获取了5个样方(10 m×10 m)共42株灌丛的TLS点云数据及实测生物量信息;然后分别使用整体凸包法、切片凸包法、切片分割法、体积表面差分法、体素法5种方法计算灌丛体积并与实测生物量进行回归分析;最后,通过留一交叉验证对5种方法建立的生物量估算模型精度进行对比分析。结果表明：TLS可在不破坏植被的情况下实现快速、准确地小叶锦鸡儿灌丛生物量反演,是传统野外调查方法的可靠替代技术。研究中采用的5种方法均能较好地估算灌丛生物量,其中：（1）相比于整体凸包法（R ²=0.87, p<0.001, RMSE=30.50 g）,切片凸包法（R ²=0.89, p<0.001, RMSE=28.01 g）与切片分割法（R ²=0.88, p<0.001, RMSE=29.03 g）可有效减弱离群点造成的体积高估,生物量估算精度有所提升;（2）格网大小为3 cm、高度统计变量选取标准差时,体积表面差分法计算的体积与实测生物量拟合度最好(R ²=0.89, p<0.001, RMSE=28.89 g),表明高度标准差是估算小叶锦鸡儿灌丛生物量的强预测因子;（3）体素法解释了生物量估计值90%的变化(R ²=0.90, p<0.001, RMSE=26.28 g),是适合小叶锦鸡儿灌丛生物量反演的最优模型。  相似文献   

Transpiration from three dominant shrub species in a desert‐oasis ecotone of arid regions of Northwestern China          下载免费PDF全文

Xibin Ji  Wenzhi Zhao  Ersi Kang  Bowen Jin  Shiqin Xu 《水文研究》2016,30(25):4841-4854

Conservation management for the water dependent desert‐oasis ecotone in arid northwest China requires information on the water use of the dominant species. However, no studies have quantified their combined water use or linked species composition to ecotone transpiration. Here, the water use of three dominant shelterbelt shrubs (Haloxylon ammodendron, Nitraria tangutorum, and Calligonum mongolicum) within an ecotone was measured throughout the full leaf‐out period for three shrub species from 30 May to 16 October 2014, with sap flow gauges using the stem heat balance approach. Species‐specific transpiration was estimated by scaling up sap flow velocities measured in individual stems, to stand area level, using the frequency distribution of stem diameter and assuming a constant proportionality between sap flow velocity and basal cross‐sectional area for all stems. The mean peak sap flux densities (J_sn) for H. ammodendron, N. tangutorum, and C. mongolicum, were 40.12 g cm^?2 h^?1, 71.33 g cm^?2 h^?1, and 60.34 g cm^?2 h^?1, respectively, and the mean estimated daily area‐averaged transpiration rates (T_daily) for the same species were 0.56 mm day^?1, 0.34 mm day^?1, and 0.11 mm day^?1. The accumulative stand transpiration was approximately 140.8 mm throughout the measurement period, exceeding precipitation by as much as 42.1 mm. Furthermore, T_daily of these shrubs appeared to be much less sensitive to soil moisture as compared to atmospheric drivers, and the relationship between J_sn and atmospheric drivers was likely uninfluenced by soil moisture regimes in the whole profile (to 1‐m depth), especially for H. ammodendron and C. mongolicum. Results indicate that these shrubs may use deep soil water recharged by capillary rise, or may directly access shallow groundwater. This study provides quantitative data offering important implications for ecotone conservation and water and land resource management. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

基于遥感数据的内蒙古草原灌丛物候变化研究   总被引：1，自引：0，他引：1  

范瑛  李小雁  李广泳 《干旱气象》2014,32(6):902-908

植被物候研究是全球气候变化研究的重要内容,但国际上有关干旱半干旱区灌丛物候变化的研究还很缺乏。为了探讨气候变化对内蒙古草原灌丛物候的影响,利用2000~2011年的MODIS EVI时间序列影像,采用动态阈值法得到6种灌丛12 a物候年际变化情况,结合样点附近气象站的气温和降水数据,分析了灌丛物候与气候变化的动态关系。结果表明：（1）内蒙古中西部草原灌丛返青期、枯黄期都呈现提前的趋势,生长季长度缩短;（2）春季均温升高和前一年秋冬降水增加可以提前灌丛返青期,是影响返青期的主要因素;（3）秋季降水减少和夏秋均温上升都利于枯黄期提前,夏季降水的作用则因灌丛种类不同而略有差异;（4）夏秋均温上升缩短了生长季长度,夏秋降水量、春季均温则多与生长季长度呈正相关。  相似文献   

青海玉树地区主要灌丛类型地上生物量及其影响因素   总被引：1，自引：0，他引：1  

钟泽兵  杨路存  刘何春  宋文珠  李璠  周国英 《山地学报》2014,32(6)

以青海玉树地区主要灌丛鲜卑花群系、百里香杜鹃群系、细枝绣线菊群系和山生柳群系为研究对象,采用样方收获法研究其地上生物量分配特征。结果表明:5种类型的灌丛地上生物量在21.6~34.33 t/hm2之间,地上生物量最大的是细枝绣线菊群系,最小的是金露梅群系,5种灌丛群落地上生物量平均是29.64 t/hm2,不同层次生物量大小顺序是:灌木层草本层凋落物层,各自生物量占地上生物量的比例分别是73.35%、14.27%、12.35%。5种灌丛类型建群种生物量大小依次是:细枝绣线菊群系金露梅群系百里香杜鹃群系鲜卑花群系山生柳群系。影响玉树地区灌丛地上生物量的主要因素是海拔、群落盖度、灌丛高度及放牧。灌丛地上生物量随着海拔的上升而下降,随着群落盖度和灌木高度的增加而增加。放牧对灌木地上生物量的影响机制尚不明确。  相似文献   

The effects of the identity of shrub species on the distribution and diversity of ground arthropods in a sandy desert ecosystem of northwestern China     

JiLiang Liu  WenZhi Zhao  FengRui Li 《寒旱区科学》2014,6(6):0587-0596

Shrub is an important factor on structuring ground arthropod communities in desert ecosystems. In this study, in order to determine how shrubs and their species influence ground arthropod distribution patterns in a sandy desert scrubland dominated by two different shrub species, Calligonum mongolicum and Nitraria sphaerocarpa, the ground arthropods were sampled with pitfall traps during spring, summer and autumn. At the community level, total arthropod abundance was shown to be significantly higher under shrubs than in intershrub bare areas in spring; similar patterns occurred in terms of the richness of arthropod groups in the spring and over three seasons, suggesting season-specific shrub presence effects on arthropod activity. In addition, more arthropods were found under N. sphaerocarpa shrubs than under C. rnongolicum shrubs in autumn, suggesting season-specific effects of shrub species of arthropod activity, whereas more arthropods taxa were captured under C. mongoIicum than N. sphaerocarpa. At the trophic group level, the abundances of predator and herbivore arthropods were significantly greater under shrubs than in intershrub bare habitats, whereas herbivore arthropods were more abundant under N. sphaerocarpa than C. rnongolicum, and an opposite rule was detected for predator arthropods At the family level, the mean abundances of Carabidae, Curculionidae, Gnaphosidae and Lycosidae were significantly higher in the shrub microhabitats than in the intershrub bare habitat, there was no significant difference between habitats on the mean abundances of Formicidae and Tenebrionidae. The study results suggested that shrub presence and shrub species variation are important determinants of ground arthropod assemblages in this desert ecosystem, but the responses of ar- thropods differed among trophic and taxonomic groups.  相似文献   

Factors controlling the spatial variability of surface soil moisture within revegetated‐stabilized desert ecosystems of the Tengger Desert,Northern China     

Yan‐Xia Pan  Xin‐Ping Wang 《水文研究》2009,23(11):1591-1601

The spatial structure of surface soil moisture was investigated at a grid scale with 10 × 10 m intervals on a plot of 4500 m² in a re‐vegetated desert area in Shapotou, the Tengger Desert. The site topography varies from dune crest to dune hollow, and again to dune crest. Volumetric soil moisture contents were measured 21 times over 6 months in 2006 by using Delta‐T Theta‐Probes in the 0–6 cm surface soil layer before and after rainfall. At the same time, soil texture, relative elevation, and plant coverage were measured, to examine (i) the spatial variability of surface soil moisture; (ii) the main factors controlling the spatial variability patterns; and (iii) how the importance of these factors varies with the seasonal variations in soil moisture content. The results indicated that the normal distribution of surface soil moisture was more obvious in wet conditions than in dry conditions; the spatial variability of surface soil moisture was inherent and decreased with increased soil moisture content; and precipitation increased the spatial dependence of surface soil moisture. The relative elevation of the landscape, the shrub coverage of the community, and the soil texture were the main factors influencing surface soil moisture variability, while the effect of soil texture strengthened gradually following the heavy precipitation events. The correlation between the spatial variability of surface soil moisture and the environmental factors, such as, the dry and wet conditions, the landscape coverage and the relative elevation suggests that increasing stability of the soil moisture resulted in a significant increase of soil moisture. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Is the analysis of plant community structure better than common species-diversity indices for assessing the effects of livestock grazing on a Mediterranean arid ecosystem?     

Y. Pueyo  C.L. Alados  C. Ferrer-Benimeli 《Journal of Arid Environments》2006,64(4):698-712

Grazing in arid Mediterranean ecosystems brings about changes in species diversity, but the best way to measure such changes is unclear. In this study we compared various methods in order to identify indicators that might be useful for the management and conservation of grazed arid Mediterranean ecosystems.Changes in community structure and composition were compared along a previously studied grazing gradient in Cabo de Gata-Nijar Natural Park. Plant diversity was measured by calculating diversity (Shannon information index), evenness (Pielou index) and richness (species number). Rarefaction curves were used to measure plant species richness and the results were compared with traditional richness values. Community structure was measured as the percentage of bare ground and the coverage of overall perennial grasses, Stipa tenacissima L., perennial shrubs and annual plants. Our results showed that the proportion of bare ground, the cover of perennial shrubs and the relative abundance of S. tenacissima are good indicators of grazing effects on vegetation. Overall plant community structure was more sensitive to the grazing gradient than were the diversity indices. Finally, the adequacy of standardized methods for comparing species richness (i.e. rarefaction curves) along a grazing gradient are discussed.  相似文献   

中国北方典型灌丛群落表土花粉组合特征   总被引：14，自引：0，他引：14       下载免费PDF全文

许清海  李月丛  赵登海  阳小兰  郑振华  郝明亮 《古地理学报》2006,8(2):157-164

来自中国北方20个典型灌丛群落的54个表土样品的花粉组合特征研究表明除蒿及沙棘灌丛外,其它灌丛中的优势植物种类在表土花粉组合中的百分比多数低于20%。阔叶林区灌丛与荒漠区和草原区灌丛表土花粉组合差别较大。阔叶林区灌丛中常有一定量的中华卷柏,蒿属和藜科百分比之和低于40%,花粉类型多样性指数多高于2.0;而草原区及荒漠区中华卷柏很少出现,蒿藜百分比高于50%,花粉类型多样性指数多低于2.0。落叶阔叶林区灌丛花粉组合中,松蒿比(P/A)大于0.1,而草原及荒漠区灌丛则小于0.1,但草原区灌丛蒿藜比(A/C)大于1,荒漠区则小于1。将松蒿比(P/A)与蒿藜比(A/C)、花粉类型多样性指数联合起来可较好地将荒漠、草原及落叶阔叶林区灌丛分开。  相似文献   

Characterizing CO2 fluxes for growing and non-growing seasons in a shrub ecosystem on the Qinghai-Tibet Plateau   总被引：2，自引：0，他引：2  

XU Shixiao  ZHAO Xinquan  FU Yuling  ZHAO Liang  LI Yingnian  CAO Guangmin  GU Song  WANG Qinxue  DU Mingyuan 《中国科学D辑(英文版)》2005,48(Z1)

To assess carbon budget for shrub ecosystems on the Qinghai-Tibet Plateau, CO2flux was measured with an open-path eddy covariance system for an alpine shrub ecosystem during growing and non-growing seasons. CO2 flux dynamics was distinct between the two seasons. During the growing season from May to September, the ecosystem exhibited net CO2uptake from 08:00 to 19:00 (Beijing Standard Time), but net CO2 emission from 19:00 to 08:00.Maximum CO2 uptake appeared around 12:00 with values of 0.71, 1.19, 1.46 and 0.67 g CO2m-2 h-1 for June, July, August and September, respectively. Diurnal fluctuation of CO2 flux showed higher correlation with photosynthetic photon flux density than temperature. The maximum net CO2 influx occurred in August with a value of 247 g CO2 m-2. The total CO2 uptake by the ecosystem was up to 583 g CO2 m-2 for the growing season. During the non-growing season from January to April and from October to December, CO2 flux showed small fluctuation with the largest net CO2 efflux of 0.30 g CO2 m-2 h-1 in April. The diurnal CO2 flux was close to zero during most time of the day, but showed a small net CO2 efflux from 11:00 to 18:00. Diurnal CO2 flux, is significantly correlated to diurnal temperature in the non-growing season. The maximum monthly net CO2 efflux appeared in April, with a value of 105 g CO2 m-2. The total net CO2 efflux for the whole non-growing season was 356 g CO2 m-2.  相似文献