Arid and semi-arid desert region in northwest is the typical desert ecosystem in China,and plays a vital role in maintaining bio-diversity eco-service function and stability of desert ecosystem.During the second half of the 20 th century,with the rapid development of population and economy,human activities changed structure and process of water and energy cycle in desert ecosystem,which caused severe shrub deterioration.In order to conserve shrub resources and enhance the recognition of the importance of shrub grassland restoration process,the paper dissertated its special effects on soil improvement,plant diversity,wind breaking and sand fixation.It was suggested that shrub be studied further to exert its greater efficiency in grassland restoration.

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%.

In this paper we investigated and compared the total phosphorus and available phosphorus concentrations in non-rhizosphere and rhizosphere soils of five super-xerophytic shrubs in the Alashan desert. The results from this study indicated that there were consistently higher total phosphorus and available phosphorus concentrations in the rhizosphere soils than in the non-rhizosphere soils of Zygophyllum xanthoxylum、Ceratoides holmgern、Atraphaxis bracteate、Tetraena Mongolica. Reaumuria soongorica showed a higher total phosphorus concentration in rhizosphere than in non-rhizosphere soils, although was shown to have a lower available phosphorus concentration in the rhizophere compared with the non-rhizosphere soils. Regression analyses indicated that there was a significant correlation between the total phosphorus and available phosphorus concentrations in non-rhizosphere soil. In contrast, rhizosphere soils showed no significant relationship between the total phosphorus and available phosphorus concentrations.

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.

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.

Sewage sludge from Qilihe sewage treatment factory,Lanzhou China,was applied for the study of the growth and element content of Lolium perenne L.by use of different quantity level in comparison with chemical fertilizer.The results showed that when the application quantity of sewage sludge was in the range of 0.5～8kg/m 2,the coverage,density,biomass of aboveground and underground of Lolium perenne L.were increased,and the chlorophyll content was increased significantly with the increase of application quantity of sewage sludge.The contents of N, P,Mg,K,Fe,Zn and Cu were increased,but Mn content was decreased,and the contents of Ca and heavy metal elements of Hg,Ni,Pb,As in aboveground biomass of that grass were no significant difference when compared with that of the control treatment.The heavy metal elements contents in he aboveground biomass were not more than the average concentration in whole plant,so the application of sewage sludge did not cause the injury on Lolium perenne L.

Sewage sludge collected from Qilihe Sewage Treatment Factory, Lanzhou, China, was applied to artificial grassland sown with Medicago sativa L. cv. Xingjiang Daye, and effects of sewage sludge on the soil environment were investigated. The results showed that application of sewage sludge improved the physical and chemical characters of the soil--the contents of organic matter, total N and P were increased; unit weight was decreased. While the application dosage of sewage sludge was in the range of 4~8 kg/m2, the contents of Fe, Ca, Cu and Zn were increased significantly, and the contents of K, Mn and heavy metal element of Ni, Pb, As and Hg in soils of 0~20 cm depth were no significant difference compared with that of the control. Also, the above elements had not moved into the lower layer of the soil and the application of sewage sludge did not cause the pollution of the soil environment.

将兰州市七里河污水处理厂生活污泥施用于人工种植的新疆大叶苜蓿草地,探讨了不同施用量对苜蓿生长及各元素含量的影响.研究结果表明,施用1.0～2.0 kg/m2污泥,苜蓿地上生物量显著增加,第一年增产23%～31%,第二年增产15%～31%.施用污泥苜蓿地上和地下部组织中N,P,Ca,Mg和Mn的含量总体呈增加趋势,Fe含量显著增加,而K和重金属元素Ni、Pb、As和Hg的含量与对照无显著差异,Zn和Cu的积累增多.但地上部组织中重金属元素均未超过植物中的平均含量,施用污泥未对新疆大叶苜蓿造成重金属污染.

Sludge is the product of sediment in the process of sewage purification.It contents great organic matter and some nitrogen,phosphorous,potassium and micro elements,which turns into useful resource after reasonal treatment.Seawage sludge from Lanzhou Qilihe sewadge purification factory was applied onto Bromus inermis grassland during 1996 and 1998 with three years monitoring,aboveground yield increase on Bromus grassland with appropriate sludge application was 163～203 percent in 1996,41～120 percent in 1998. Root biomass increase in 1996 was 35～106 percent higher than the control. Through sludge application,soil organic matter, totalnitrogen,phosphorous and potassium in 0～20 depth was increased significantly. Volume weight decreased with sludge increasing.The results indicated that,the nutritional element contents in the sludge from Qilihe sewadge purification factory was high,contents of harmful element was 10 wer than standards. It was usable biological resource.