草原化荒漠植被草本层片植物对人工施加氮素的响应

水分是干旱区生态过程的第一非生物限制因子,土壤氮由于直接影响着生物生产力和土壤生态过程而被认为是仅次于水分的限制因子。利用人工施加氮肥的控制试验研究了荒漠植被草本层片植物在多度、物种丰富度、高生长以及地上部分生物量等群落学特征对不同施肥处理的响应。结果表明,在施肥量分别为12.5、25、50 g·m-2时,样方植物多度和物种丰富度在施肥当年和第二年较对照均有不同程度的降低,且施肥量越高,降低越明显,这一结果支持来自典型草地和森林植被生物多样性对氮素增加或氮降沉增加响应的结论,即氮素的增加会使生物多样性减少。地上部分生物量对施氮肥的响应在施肥当年(年降水量为多年平均值的1.4倍)和第二年(年降水量为多年平均值的0.7倍)表现出相反的规律,即施肥当年随着施肥量的增加生物量显著增加,而在第二年则显著减小,说明水肥耦合同样有利于荒漠生态系统生物生产力的提高。氮素对植物高生长的影响不明显,各施肥梯度与对照相比均无显著性差异(P>0.05),这可能主要取决于荒漠草本植物本身固有的生物学特性。     

草原生态系统生态补偿机制研究:中德案例研究比较(英文)

目前,草地生态系统退化成为全球关注的问题。生态补偿机制(PES)是为了草地生态系统的恢复/保护,采取补贴或支付费用的方式,改变使用者资源利用方式的制度安排。科学、合理的生态补偿制度需要全面地考虑可能出现的风险和挑战:如环境效益的滞后性,不可预见的监督、管理成本和社会经济目标(足额补偿标准、公平)的实现。本文的目标是通过中德两国生态补偿措施的对比(选取中国内蒙古锡林郭勒盟,德国勃兰登堡州为案例区域进行研究),为今后中德两国的生态补偿理论和实践提供依据。研究着重以下四个方面进行分析:中德两国生态补偿的实施框架,目标人群,实施效果评估等。研究结果表明,由于缺乏有效的激励机制,农户作为最基层的执行单位和实施者,其参与的主动性不够,中德两国生态补偿措施实施的成效有待提高。基于研究结果,提出了今后生态补偿项目设计中,中国应侧重于项目实施的监控和管理制度;而德国应在空间目标规划和具体管理措施和方式等方面进行完善。     

中国草原旅游研究的进展与展望

草原旅游发展在我国逐渐成为热点,研究文献不断出现。20世纪90年代以来的研究主要集中在旅游发展战略、旅游经济研究、地方旅游资源开发、旅游地管理、旅游环境影响、旅游资源一般理论、旅游产品研究、旅游美学研究、旅游文化研究、目的地营销、旅游纪念品和旅游法规等领域。研究具有明显的时段性,作者所在地域与研究区域具有高度一致性,研究内容过于集中,研究方法以定性描述为主。今后要注意规范旅游研究方法,注重多学科交叉相融,细化研究领域,拓展研究方向。     

Turbulent intensity and its similarity function over an Inner Mongolian grassland during spring

Macroscopic reason for the development of turbulences in fluid is the conjunction action of velocity and temperature shears. We use the 2008 spring flux observations in the surface layer over Inner Mongolian grassland, obtain the similarity functions of turbulent intensity under different stratification stability conditions, and calculate the clear day turbulent intensity in the spring, which is then analyzed and compared with the observed values of turbulent intensity. The results show that in the Inner Mo...     

祁连山中部亚高山草地土壤呼吸及其组分研究

草地碳通量组分的区分及其与环境因子的关系是了解生态系统碳循环的重要环节。于2013年6-8月在祁连山中部亚高山草地开展了土壤呼吸及其组分研究,利用根去除法区分根系自养呼吸和土壤微生物异养呼吸。采用LI-8100土壤碳通量系统测定生态系统呼吸、土壤呼吸及土壤微生物呼吸速率,同时测定10cm处土壤温度和5cm处土壤湿度。分析呼吸速率和环境因子的昼夜变化动态,自养呼吸和异养呼吸速率占土壤呼吸速率的比例,呼吸速率与土壤温湿度及与生物量的关系。结果表明：生态系统呼吸、土壤呼吸和土壤微生物呼吸速率的日变化趋势均呈单峰型曲线,具体表现为生态系统呼吸（11.07μmol · m^-2 ·s^-1）>土壤呼吸（6.31μmol·m^-2·s^-1）>异养呼吸（4.92μmol·m^-2 ·s^-1）>自养呼吸（1.39μmol·m^-2·s^-1）;自养和异养呼吸速率分别占土壤呼吸速率的22.03%和77.97%;呼吸速率与10cm处土壤温度呈指数相关,Q₁₀值排序为：土壤微生物呼吸（Q₁₀=3.74）>土壤呼吸（Q₁₀=2.76）>生态系统呼吸（Q₁₀=2.49）,呼吸速率与5cm处土壤湿度呈显著线性负相关关系,双因素模型明显提高了呼吸速率与温湿度的相关性,能够分别解释土壤微生物呼吸,土壤呼吸和生态系统呼吸速率变异的89%,79%和62%;地上生物量和呼吸速率之间存在显著线性正相关关系,地下生物量与呼吸速率之间呈二次回归关系（P=0.01）,未刈割草地呼吸速率大于刈割草地土壤呼吸速率,刈割一年的土壤呼吸速率大于刈割两年的土壤呼吸速率。     

Strip Transect Sampling to Estimate Object Abundance in Homogeneous and Non-homogeneous Poisson Fields: a Simulation Study of the Effects of Changing Transect Width and Number

This paper investigates the use of strip transect sampling to estimate object abundance when the underlying spatial distribution is assumed to be Poisson. A design-based rather than model-based approach to estimation is investigated through computer simulation, with both homogeneous and non-homogeneous fields representing individual realizations of spatial point processes being considered. Of particular interest are the effects of changing the number of transects and transect width (or alternatively, coverage percent or fraction) on the quality of the estimate. A specific application to the characterization of unexploded ordnance (UXO) in the subsurface at former military firing ranges is discussed. The results may be extended to the investigation of outcrop characteristics as well as subsurface geological features.     

Sources of water used by natural mesquite vegetation in a semi-arid region of northern Mexico

Abstract

Vegetation structure in semi-arid regions of northern Mexico and the southwestern USA has changed dramatically over the last century; shrubs such as mesquite (Prosopis sp.) have expanded into, and have become dominant in, ecosystems that once supported semi-arid grassland. The upper San Pedro River watershed, which extends from northern Sonora (Mexico) to southeastern Arizona (USA), highlights these changes. Between 1973 and 1992, grasslands decreased by 18% and the total area dominated by mesquite increased during the same period by 412%. In the areas where the density of mesquite shrub is medium to high, grass has completely disappeared under the shrub canopy and has been replaced by bare soil. Undoubtedly these cover changes have affected surface—atmosphere interactions by introducing a different partitioning of net available energy into sensible and latent heat flux. At the same time, different root system and root density and plant physiology have introduced a change to the surface water balance, reducing inflitration and increasing runoff. Our study addressed the sources of water used by mesquite (Prosopis velutina) along a natural gradient from an area of high mesquite cover with no herbaceous grass cover, to open savanna with high grass cover and widely spaced mesquite. The presented results from the SALSA 1997 monsoon-season campaign (July—October) show that mesquite shrubs that have access to both ground-water and surface water use surface water when available, potentially competing with grass for surface water and out-competing grass during successive periods of drought when only groundwater is available.     

Dynamics in land-surface conditions on the Tibetan Plateau observed by Advanced Synthetic Aperture Radar (ASAR)

Abstract

A time series analysis of 152 VV-polarized Advanced Synthetic Aperture Radar (ASAR) Wide Swath Mode (WSM) images collected over the central part of the Tibetan Plateau is presented for the period from April 2005 to September 2007. The signatures of a grassland and a wetland are studied to identify the impact of three land-surface states on the backscatter (σ°). The considered land-surface states are soil moisture, soil temperature and vegetation biomass represented by Système Pour l'Observation de la Terre (SPOT) Normalized Difference Vegetation Index (NDVI). Comparison of the σ° time series with these land-surface states via a multivariate regression shows that the grassland σ° are well represented by the soil moisture dynamics, while the wetland σ° also has a strong correlation with soil temperature. Further, we found that the contribution of the NDVI to the explanation of the temporal σ° variability is limited for both the grassland and wetland.     

黄河源高寒草原下垫面土壤冻融过程中陆-气间的水热交换特征分析

高寒草原水热交换的季节性特征显著,土壤冻融过程对地-气水热交换有着重要的影响.本文利用黄河源区汤岔玛小流域2014年5月至2015年5月陆面过程观测数据,将土壤冻融过程划分为完全融化(TT)和完全冻结(FF)两种状态与融冻(T-F)和冻融(F-T)两个过程,并分析了期间高寒草原下垫面净辐射、感热通量、潜热通量和地表热通...     

祁连山南麓退耕地主要植物群落植冠层的截留性能

退耕地人工群落植冠层的截留能力,是群落生态效益的重要组成部分,这一研究不仅可以掌握退耕还林还草工程作用的机理,还可以更好地指导工程实践,促进工程建设步伐。通过“简易吸水法”,可以快速掌握退耕地植冠层的最大截留潜力。青海省大通县退耕较早、平均年龄约10a以上的青海云杉、华北落叶松等几种人工群落,它们的林冠截留量较高,平均达1．93mm,为当地3种截留量最高、林龄50a之上天然群落的61％。青海云杉、华北落叶松、白桦、青杨、中国沙棘等退耕地人工群落的截留量,基本上显示出与林龄之间呈线性或Cubic、Quadratic正相关关系。在植物群落分层截留、消化吸收降雨的这一空间垂直序列中,植冠层截留量虽然较低,平均仅1．29mm(0．25～2．38mm),但植冠层的主要作用还在于减轻、缓冲雨水直接打击地面,改变降水的侵蚀性危害,而这些作用要远远高于截留量自身的区区数量。