干旱荒漠区植被恢复与重建的探讨

西北干旱荒漠区生境严酷，物种贫乏，植被稀疏低矮，加上不合理的开发利用，致生境恶化。利用当地有限的水源来实现干旱荒漠区的植被恢复，防止流沙蔓延，可以从以下两方面入手：一方面，以裸地为立地条件，利用当地的关键种(keystone specics)或优势种(dominant species)，选择合适的生境，采用人工种子库和幼苗移植等方法，促使已缺失的植物种在目的地重新定居；另一方面，利用灌丛效应选择合适物种加以配合，提高干旱荒漠区的植被盖度。研究表明：以上两种途径对实现干旱荒漠区的植被恢复和重建是可行的。     

塔克拉玛干绿洲外围胡杨林的水分特征研究

塔克拉玛干沙漠南缘地区年均降水量不足50mm,胡杨在这一地区绿洲外围自然植被中占有重要地位.对塔克拉玛干沙漠绿洲外围胡杨林水分特征的研究表明,在生境地下水含量较稳定的条件下,胡杨林受到的水分胁迫程度不大,干旱胁迫未对胡杨林的持续存在构成主要威胁.胡杨的水分生理特点显示植物更加依靠稳定的水分供应来应对极端干旱的环境条件,并且在蒸腾作用中形成了细胞水平上的生理适应策略.因此,保持地下水的稳定是维持绿洲前沿天然胡杨林持续存在的关键因素.     

UNCCD与《中华人民共和国防沙治沙法》比较研究

文章选取了《联合国防治荒漠化公约》和《中华人民共和国防沙治沙法》作为比较对象,从立法背景、性质、基本结构、基本内容等角度对二者进行了比较,并指出了二者的特有之处。从而分析国内法律和国际法律的不同,并提供了我国防治沙漠化中如何借鉴好的做法,并结合自身的实际情况加以吸收的途径。     

Investigating incorporation and distribution of radionuclides in trinitite

Most of the surface explosions in nuclear tests have released radioactivity to the environment in the form of bulk glassy materials originating from the melting of sandy soil in the neighbourhood of ground zero. In view of clarifying issues concerning the mechanism of formation and the radiological impact of these materials, we investigated incorporation and volume distribution of radionuclides in a typical fragment of trinitite, the glassy substance generated following the first nuclear test (Trinity Site, New Mexico, 1945). Specific activities were determined by γ-spectrometry for the most significant fission and activation products. In particular, ¹⁵²Eu activity was used to estimate the original point of collection of the sample with respect to ground zero. After embedding in an epoxy resin, the sample was then sliced to perform cross-sectional β- and α-autoradiograph. α-spectrometry was also carried out on a fine powder obtained by surface abrasion. In the β-autoradiography, hot spots were distinguishable in the proximity of the blast side, over a 1000 times less intense background of sand activation products. Also α-contamination (from ^239+240Pu and ²⁴¹Am) was mostly concentrated within the superficial layer, in a fraction of only 20% of the overall volume of the sample, exhibiting a discontinuous, droplet-like distribution. This evidence would partially support a recent hypothesis on trinitite formation according to which most of the glass layer was formed not on the ground but by a rain of material injected into the fireball that melted, fell back, and collected on a bed of already fused sand.     

Effects of Artificial Sand Fixing on Community Characteristics of a Rare Desert Shrub

Eremosparton songoricum (Fabaceae) is a rare, native, clonal small shrub of the deserts of central Asia. Although human activities have greatly fragmented the distribution of E. songoricum, it occurs in areas where artificial sand fixing (AS) has been implemented. We sought to explore whether AS promotes survival and growth of E. songoricum. In the Gurbantunggut Desert of northwestern China in June 2010, we established 10 plots in an area where sand fixing occurred (5–10 years previously) and 11 plots on original sand substrate on which some plants had settled without fixing sand. Sand fixing changed soil properties and biological characteristics in sand‐fixed plots. The soil surface where sand fixing occurred was covered by algal crusts and some lichen, but not bare sand (BS). Soil nutrients; water content of deep soil (30–150 cm); overall plant and herbaceous species richness, diversity, abundance, and cover; above‐ and belowground biomass; and cover, biomass, and height of E. songoricum in the sand‐fixed plots were significantly greater than in plots of BS. However, distribution of E. songoricum individuals in the 2 types of plots did not differ. Our results indicate AS may enhance survival of E. songoricum and increase the overall diversity and stability of the desert plant community. We suggest AS as a way to protect this rare desert plant in situ. Efectos de la Fijación Artificial de Arena sobre las Características de la Comunidad de un Arbusto Desértico Raro     

Isolated Spring Wetlands in the Great Basin and Mojave Deserts,USA: Potential Response of Vegetation to Groundwater Withdrawal

Desert springs, often the sole sources of water for wildlife and cattle, support wetland and wetland/upland transition ecosystems including rare and endemic species. In the basin and range province in Nevada, USA, springs in the Great Basin and Mojave deserts are sustained by interconnected deep carbonate and shallow basin-fill aquifers which are threatened by proposed groundwater withdrawal to sustain rapidly expanding urban areas, a common problem in arid regions worldwide. This paper draws on historic groundwater data, groundwater modeling, and studies of environmental controls of spring ecosystems to speculate on the potential effects of groundwater withdrawal and water table decline on spring-supported vegetation. The focus is on springs in the Great Basin and Mojave deserts representative of those that may be affected by future, planned groundwater withdrawal. Groundwater withdrawal is expected to reduce spring discharge directly through reduced flows from the shallow basin-fill aquifer or through reduction of the hydraulic head of the deep carbonate aquifer. This flow reduction will truncate the outflow stream, reducing the areal cover of wetland and wetland/upland transition vegetation. Lowering the local water table may also reduce the amount of upland phreatophytic vegetation by causing water levels to drop below plant rooting depths. Percolation of salts to surface soils may be reduced, eventually altering desert shrub cover from halophytes to nonhalophytes. The extent of these effects will vary among springs, based on their distance from extraction sites and location relative to regional groundwater flow paths. On-site monitoring of biotic variables (including cover of selected hygrophytes and phreatophytes) should be a necessary complement to the planned monitoring of local hydrologic conditions.     

Land Management in the American Southwest: A State-and-Transition Approach to Ecosystem Complexity

State-and-transition models are increasingly being used to guide rangeland management. These models provide a relatively simple, management-oriented way to classify land condition (state) and to describe the factors that might cause a shift to another state (a transition). There are many formulations of state-and-transition models in the literature. The version we endorse does not adhere to any particular generalities about ecosystem dynamics, but it includes consideration of several kinds of dynamics and management response to them. In contrast to previous uses of state-and-transition models, we propose that models can, at present, be most effectively used to specify and qualitatively compare the relative benefits and potential risks of different management actions (e.g., fire and grazing) and other factors (e.g., invasive species and climate change) on specified areas of land. High spatial and temporal variability and complex interactions preclude the meaningful use of general quantitative models. Forecasts can be made on a case-by-case basis by interpreting qualitative and quantitative indicators, historical data, and spatially structured monitoring data based on conceptual models. We illustrate how science- based conceptual models are created using several rangeland examples that vary in complexity. In doing so, we illustrate the implications of designating plant communities and states in models, accounting for varying scales of pattern in vegetation and soils, interpreting the presence of plant communities on different soils and dealing with our uncertainty about how those communities were assembled and how they will change in the future. We conclude with observations about how models have helped to improve management decision-making.     

DESERT HOUSE: A DEMONSTRATION/EXPERIMENT IN EFFICIENT DOMESTIC WATER AND ENERGY USE1

ABSTRACT: In May 1993, a single-family home and adjoining information center opened to the public at the Desert Botanical Garden in Phoenix, Arizona. Desert House is designed as an example of what can be achieved today using available technology to improve residential water and energy efficiency. The home is expected to reduce water and energy use by 40 percent compared with that for the typical three-bedroom, single-family residence in the Phoenix area. Water-conserving features include: landscape design employing low-water use plants, minimum turf area, mulch around plants to reduce evaporation, and drip irrigation system; spa cover for evaporation reduction; rainwater harvesting; low-flow shower heads, faucets, and toilets; and graywater reuse system. The home will be occupied by a family and monitored for water and energy use by computer. Visitors are able to access real time water and energy use data about the home, as well as tour the information center, technical exhibits, surrounding landscape, and the home when it is open (one afternoon a week).     

荒漠生态系统监测研究指标体系

新疆环境保护科学研究所自1984年接受“荒漠生态系统监测指标体系的观测研究”课题,在乌鲁木齐北部90km处的沙漠边缘建立了“准噶尔沙漠生态系统定位研究站”,自1987年正式开展了“荒漠生态系统定位观测研究”工作,从古尔班通沙漠中部至天山博格达峰中山带选定了沙漠、沙漠边缘、山前洪冲积扇、前山和中山带五个观测场,沙漠四季进行定位观测,同时,在站内进行多项目的连续观测,现集五年观测研究经验,结合中国科学院及国外研究站的先进经验,建立了荒漠生态系统指标体系。