土壤酸碱度(pH)是判断土壤理化性质最重要的指标之一,影响着土壤的肥力和土壤养分的形态及有效性.选取5种草地类型土壤,分别采用国际和国内标准测定其pH值并探讨了影响测定结果的因素及两种标准之间的差异,结果表明:pH值测定主要受静置时间和水土比的影响,振荡时间对测定结果无显著影响;两种标准之间具有较好的相关性,其中国际标准测定结果稳定性高且具有可比性.基于以上研究,建议使用国际标准测定我国草地土壤pH值.

The best experiment conditions,accuracy and precision for determining the microamounts of lead content in plant by microwave-heating GF-AAS approach were studied.Results indicated that the best acid system is 5 mL HNO3-3 mL H2O2-2 mL HF,the best microwave-heating condition is under the state of power 600 W、temperature 180 ℃ and microwave-heating 15 min.The optimal working condition of Graphite Furnace is the dried 45 s under 90 ℃,cineration 20 s under 900 ℃,atomized temperature 1 400 ℃ and cleaned temperature 2 500 ℃.The limit of detection of this method was found to be 0.068 4 mg/kg,the relative standard deviation error were in the range of 1.2%-5.6%,and recoveries were in the range of 95.81%-100.09%.

The amount of available silicon in soil was determined by flow injection analysis approach in this paper.The determination coefficient(R2) of this standardized work curve was found to be above 0.9999.The detection limit of this method was 0.012 μg/mL,the relative standard deviation was in the range of 0.04%-0.06%,and the spike recoveries ranged from 97.89% to 99.93%.The experimentation has proved that this approach is characterized by simple operation and pretty good linear correlation,the precision,accuracy and sensitivity could meet the analytical requirements.

This paper summarized the component and role of root exudates,as well as the effects of vegetation types,nutrition stress and rhizosphere microorganisms on the types and quantity of root exudates.In general,under stress condition,the quantity of root exudates increase significantly,it ameliorates plant's growing situation under lacking of nutrition or metal contaminated condition.Some of phenolic acids in root exudates is harmful to plants at high concentration;at the same time it restrains plants'growth.Further research on the generation mechanism of the root exudates and their reflections in physiology and ecology,will help to further understand the physiologic and ecological course on root and soil interface and the mechanism of control and regulation.

根据近20余年来学科的发展,笔者提出通过调整实验教学模式,对"草原生态化学"实验课课程体系、实验课内容和教学手段进行改革,旨在培养学生综合分析问题的能力和创新能力.

根据近20余年来学科的发展,笔者提出通过调整实验教学模式,对"草原生态化学"实验课课程体系、实验课内容和教学手段进行改革,旨在培养学生综合分析问题的能力和创新能力。

The characteristics and water depletion of plant community dominated by Calligonum alaschanicum in Alaxan desert were researched in this paper.The results showed that depleted water by C.alaschanicum community depended on the precipitation.Biomass of C.alaschanicum community increased with the increase of precipitation.Utilization rate of water was from 0.15% to 0.15%,while soil water was depleted from 630 to 648 gram as per gram dry matter being produced.The optimum utilization rate of C.alaschanicum was from 30%-50%.

Zygophyllum xanthoxylum is a kind of shrub which has the strong ability of combating drought.It is the main species at the grassland in the arid desert and it can become a stable community.Z.xanthoxylum flowers first,then grows leaf.It buds in the middle ten days of April,blossoms in the last-ten days of April and seeds mature in the last-ten days of June.The budding rate is 90%.In drought areas,the seedling grows fast and it doesn't easily die.The plant's life span is more than 20 years.When Z.xanthoxylum grows 3 or 4 years it is able-bodied period and begins seeding more.The branches can sprout new buds at the basal part after being covered with sand,and still produce some indefinite roots.75% roots mainly centralize at the 0-40 cm soil.When the roots of Z.xanthoxylum grow downwards and arrive at the soil layer where water was used out,the roots grow upwards.This research shows Z.xanthoxylum mostly depends on assimilating surface water to survive.These excellent characteristics of Z.xanthoxylum create good ecological environment of water,so it can resist drought and cold;can stand poor soil;has better adaptability;grows fast.It has plenty of nutrition(the content of coarse protein is from 10.49% to 12.68%),and the livestock likes eating it. Therefore,it is a kind of small shrub that deserves extending and planting.

Nitraria sphaerocarpa seedlings were placed under different degrees of water stress simulated with PEG-6000 to investigate their variations in plant weights,and K~(+), Na~(+), MDA, free proline and soluble sugar contents.It was shown that under the water stress simulated with PEG-6000 at 15% Nitraria sphaerocarpa seedlings presented the highest biomass and the lowest MDA content and significantly differed from those under control in these two respects;as water stress was intensified,the seedlings gradually decreased their K~(+) content and significantly differed from those under control in this respect, and they decreased their Na~(+) content at the beginning and then increased the content but did not change their total Na~(+) accumulation; and they significantly increased their free proline and soluble sugar contents as water became intensified. It follows that light water stress is favorable for Nitraria sphaerocarpa seedlings to grow, and free proline and soluble sugar are the major osmosis-regulating substances of Nitraria sphaerocarpa adapting to droughty environments among organic substances.

The significance expressed by important values of Artemisia sphaerocephala,Psammochloa villosa and calligonum alaschanicum in A.sphaerocephala + C.mongolicum community were(49.85%),29.34% and 13.33% respectively after 6 years open utilization.The biomass of the community was 92.73 and 83.59 g/m~2 in the first and second experimental year respectively.The water depletion of the community was 687.28 and 918.17 gram per gram dry matter being produced in the first and second experimental year respectively.The sustainable productivity of the community depended on the utilization.The results indicated that the optimum defoliation rate of A.sphaerocephala population was 30 percent on the bases of the largest 30 percent significance expressed by important values.

At the southeastern edge of Tengger Desert in Inner Mongolia of northern China, grassland degradation usually occurs primarily due to improper management regimes in fragile environmental conditions. Over the last several decades, most sandy grasslands in this region have turned into shifting, semi-shifting and semi-fixed sandy lands, corresponding to severe, moderate and light degradation. To curb degradation and alleviate the impacts of degradation on environment and human life in this region, the central and local governments have implemented a variety of measures to restore vegetation on degraded grasslands since the mid 1990s. One of these measures is revegetation by planting indigenous shrubs and semi-shrubs (e.g. Artemisia sphaerocephala) through air seedling on severely degraded areas. As a result, artificial communities of A. sphaerocephala have been established in many parts of the Tengger desert.

A study was carried out on the seasonal change in content as well as relationships between organic nutrients such as protein, fat, cellulose, and nitrogen-free extract, and inorganic nutrients including Ca, P, and ash in the aboveground edible spray of the strong xerophils Zygophyllum xanthoxylum and Reaumuria Soorgorica in the Alashan desert area. In the early stage of growth, the cellulose content was relatively low, and the content of other nutrients all showed increasing trends. In entering the last growth stage, the different nutrient contents showed decreasing trends, but the cellulose content reached its highest value. For the entire growth and development period, there were significant negative correlations between crude protein and crude fibre, and between crude fibre and crude ash, and significant positive correlations between crude protein and crude ash, crude protein and P, and Ca and crude ash.

以阿拉善极度退化的草原化荒漠区为研究对象,对放牧与围封条件下退化群落的物种多样性、生产力和群落演替及其生态机制进行了初步研究,结果表明:1)荒漠植物群落物种多样性指数在时间尺度上的变化表现为随着自由放牧时间的延长逐渐降低,随着围封时间的延续逐渐增加,而生态优势度变化趋势则相反.2)围封导致荒漠群落物种多样性指数增加的主导因子是物种丰富度的增加;围封使荒漠群落恢复的生态机制在于消除牧压后不同种群繁殖对策的实现,拓殖能力的增强和剩余资源的充分利用.3)围封第3年草原化荒漠群落优势种发生变化,短花针茅大量生长,群落发生恢复演替的结果使群落生产力得到大幅度提高.

Soil physical and chemical properties of desert grassland with different grazing management systems were studied at Alxa Prefecture, Inner Mongolian Autonomous Region. The results showed that started from the similar grassland conditions soil bulk density of medium grazed paddocks at 0～20 cm depth was higher than those of light and heavy grazed paddocks six years after grazed with different stock rates. As grazing intensity increased the proportions of extremely coarse, coarse and medium size sandy particles were increased, while the contents of fine and extremely fine sandy particles, silt particle and clay particle were decreased. This indicated that overgrazing accelerated the process of soil wind erosion and desertification. The contents of organic matter, total P and C/N at 0 ～ 20 cm depth decreased as the grazing intensity increased. No significantly differences in the contents of total N, total K and pH were detected among the paddocks with different grazing intensity. However, the contents of available N and available K in the soil of heavy grazed paddocks were higher than those in the light and medium grazed paddocks. On the other hand, the contents of available P in the light grazed paddock is the highest, which is followed by the medium and heavy grazed paddocks. Significantly positive correlations were found between soil organic matter and contents of total P, available P, and between contents of total P and available P. Significantly negative correlations were existed between the contents of total P and available N, and available K., respectively.