盐渍化沙地土壤旱化过程中植被的变化

利用地下水位高低不同地区所形成的不同立地类型水平空间上的分布来代表盐渍化土壤沙化旱化过程时间分布上的发展,分5种立地类型探讨盐渍化土壤干旱沙化过程中植被的演变特征。随着地下水位的降低,各立地类型土壤上植物种类减少,植被盖度降低,相邻植物群落中共有种逐渐增加,变异性减少,植被演变趋势从湿生—中生耐盐—沙生旱生植物过渡。

干旱区盐渍化沙地梨的定植技术初探

该项研究 ,探讨了干旱区盐渍化沙地上 ,苗木类型、定植方式、生存环境等对梨树定植成活率的影响。杜梨苗经耐盐性锻炼后再定植于土壤含盐量≥0.55 %的沙地上 ,其成活率可达88.3 %～93.0 % ,定植的平均有效成本降低16.40元/666.7m2。杜梨苗直接定植比杜梨砧木成品苗的成活率高17.0 %。沟植的树行内土壤全盐量比穴植的低0.62 % ,二者苗木成活率差异明显。梨园行间种植甜菜的苹果梨年生长量为行间土地休闲的1.3倍。在干旱沙区 ,果园行间以种植夏季作物为宜。树行内覆草增加了0～30cm土层的有机质含量 ,促进土壤脱盐。砧木建园、炼苗、沟植、地表覆盖、施有机肥等技术措施是提高干旱区盐渍化沙地苗木成活率的有效措施。

Effects of Vegetation Restoration in Different Types on Soil Nutrients in Southern Edge of Mu Us Sandy Land

In order to explore effects of vegetation on nutrients in soils, nutrients characters of soils under natural grass, closed grass, abandoned lands, forest lands returned from farmlands and fixed sandy areas in Mu Us Desert were researched. The results indicated that vegetations in varied types have different effects on organic matter, total N, available N and available P, among which the first three were all higher in soils under closed grass, forest lands returned from farmlands, and fixed sandy lands than those under natural grass and abandoned lands. This was totally contrary with contents of available P in soil. In addition, nutrients in soils at 0-20 cm were more influenced by vegetation, than those at 20-60 cm, and Caragana Korshinskii proved better in improving nutrients in soils.

Effects of Artificial Vegetation Restoration on Soil Physicochemical Properties in Southern Edge of Mu Us Sandy Land

[Objective] This study aimed to investigate the artificial vegetations on soil physicochemical properties of sandy land. [Method] The soil physicochemical proper- ties in five representative lands respectively covered by Artemisia ordosica, Salix cheilophila, Hedysarum scoparium, Populus simonii and Amorpha fruticosa, all of which were planted artificially at the same year were measured in the present study, using a bare soil as the control. [Result] Artificial vegetation improved the soil physicochemical properties by different extents in the lands covered by different plants. The soil physicochemical properties such as bulk density under A. Fruticosa and H. Scoparium were improved greatly. The frequency distribution of soil particle size under artificial vegetations exhibited a bimodal curve. The average soil particle size under A. fruticosa was the smallest, and the soil was very poorly sorted. The soil nutrients in the sandy land were not significantly improved by artificial vegeta- tion. [Conclusion] Artificial vegetation has a certain impact on soil properties in sandy land, as it greatly improves the soil physical properties but not the chemical properties.

Analysis and assessment of land desertification in Xinjiang based on RS and GIS

The land desertification in Xinjiang was monitored and analyzed based on RS and GIS techniques. Satellite data interpretation was adopted to obtain the general situation of Xinjiang’s land desertification in assistance with the sampling method and on-the-spot investigations. Related monitoring and investigations showed that Xinjiang was facing with severe wide range land desertification, and its desertified area made up 77.08% of the total monitoring area. As for land types, the desertified farmland accounted for 1.92% of the total monitoring area, desertified woodland 4%, desertified grassland 45%, and unused land 49%. Accordingly, as for desertification degrees, non-desertified land occupied 22.92%, weak desertified land 5.69%, medium-degree desertified land 16.58%, severe desertified land 33.19% and super severe desertified land 21.61%. Finally, as for inducing factors, wind-eroded desertification made up 58.23%, water-eroded desertification 8.69%, salinization desertification 6.52% and frozen-melt eroded desertification 3.64%. Xinjiang’s land desertification tended to get worse and the harnessing mission remained hard.

THE DYNAMIC MONITORING OF HORQIN SAND LAND USING REMOTE SENSING

Horqin Sand Land is regarded as the typical region for studying the problemof desertification. The integration of 3S(GIS, GPS and RS) techniques offer a roost helpful methodto study and monitor the dynamics of desertification. Based on the data derived from 3 periods'multitemporal Landsat TM imagery of the 1990s, the regional land use and dynamics of desertificationin Horqin Sand Land were studied. The main results revealed that: 1) as long as the general changetendency was concerned, the desertification of Horqin Sand Land would continue to spread; 2) therewas a gradual decrease in the area of both moving sand dunes and semi-stabilized ones, which meantthat fruitful progress had been made to control the desertification during the 1990s; 3) as a resultof unreasonable cultivation, the total area of stabilized sand dunes and grassland in the middleand western region decreased obviously. It suggested that the increasing damage caused by human wasleading to the hazard of further desertification. So in the future, it is necessary to take moreeffective measures to control the spread of desertification and restore the degraded ecosystems forthe purpose of optimizing the global eco-environment in Horqin Sand Land.

Eco-economic control mode and benefit analysis of rock desertification region in Huajiang Karst Valley of Guizhou Province

It is difficult to afforest in rock desertification region and is the key area for eco-environment treatment. To speed up the comprehensive treatment of rock desertification, several anti-rock desertification modes implemented in Dingtan region, located on the right bank of Huajiang Grand Valley in Beipanjiang Town, are introduced as examples. This paper first analyzes the natural and environmental conditions, the development of rock desertification in the Dingtan region, then the detail of the treatment modes, such as “Chinese wingleaf pricklyash – pig breeding – marsh gas” (Mode One), “amomum villosum – pig breeding – marsh gas” mode (Mode Two), “traditional grain and economic crop (corn, peanut) – amomum villosum or Chinese wingleaf pricklyash” (Mode Three), etc. The eco-economic effects, potential and shortcomings of the above mentioned modes are analyzed and compared. It is proved that Mode One and Mode Two are of good economic effect, but Mode Three of better ecological effect. Solutions to the shortcomings of the modes are also put forward.

Biological Characteristics of Carex brunnescens for Sand Fixation in the Source Region of the Yellow River

Carex brunnescens, a pioneer plant that has an excellent ability to fix sand in the source region of the Yellow River （Maqu）, plays an important role in maintaining the ecosystem stability of alpine grassland in Maqu. In this study, the biological characteristics （phonological characters, the growth process of overground and underground organs, and the morphological characters of underground organs） of C. brunnescens were studied by a field observation experiment. The results showed that C. brunnescens had the characteristics of turning green earlier than other plants, a long growth period, and two flowering and fruiting cycles. The leaf width, length and number of a single plant, and the density, coverage and leaf density of community increased significantly from the leaf extension period to the fruit mature period and then tended to be stable in the withering period, while the plant height and leaf area of a single plant and the leaf area of community rose significantly at first and then decreased. Underground stems （horizontal and vertical stems） and roots of C. brunnescens could survive in sand at a depth of 0-60 cm. The number of middle roots （0.2-0.5 mm in diameter） was the largest in all soil layers （0-20, 20-40 and 40-60 cm）, and the total length of fine roots （〈0.2 mm） were the maximum in the sand at a depth of 20-40 cm, while the total length of middle roots was the maximum in the sand layer at a depth of 0-20 cm. The length, fresh weight and dry weight of the main root, horizontal and vertical stems was the maximum in the sand layer at a depth of 10-30 cm and was the minimum in the sand layer at a depth of 40-50 cm. It is concluded that C. brunnescens can well adapt to the alpine sand habitat of Maqu, can be used as the constructive species for ecological restoration in the alpine desertified grassland of Maqu, and has good popularization and application prospects.

Effects of adding water on seasonal variation of soil nitrogen availability under sandy grasslands in semi-arid region

Water is usally thought of a limiting factor for the restoration of semi-arid ecosystem. In the growing season of 2006, a study was conducted to determine the effects of modeling precipitation on seasonal patterns in concentrations of soil-available nitrogen and to describe the seasonal patterns in soil nitrogen availability and seasonal variation in the rates of net nitrogen mineralization of topsoil at Daqinggou ecological station in Keerqin sand lands, Inner Mongolia Autonomous Region, China. Manipulation of water （80 mm） was designed to be added to experiment plots of sandy grasslands in dry season. Water addition （W） treatment and control （CK） treatment were separately taken in six replications and randomly assigned in 12 plots （4 m×4 m for each） with 2-m buffers betweens. Results showed that the content of soil inorganic nitrogen and net nitrogen mineralization rate were not affected by adding water in sandy grassland of Keerqin sand lands. Net ni- trogen mineralization rates ranged from 0.5μg·g^-1,month^-1 to 4 μg.g^-1.month^-1. The highest values of soil inorganic nitrogen and net nitrogen mineralization occurred on October 15 in control plots. The seasonal changes of soil inorganic nitrogen contents exhibited ＂V＂ shape pattern that was related to seasonal patterns of soil ammonium-N （ascending trend） and nitrate-N transformation （descending trend）.

Diagnostic model construction and example analysis of habitat degradation in enclosed bay: II. spatiotemporal variations in habitat degradation in Sansha Bay

The process of habitat degradation varies in habitat type and driving force which shows certain spatial and temporal heterogeneity on regional scales. In the present study, a new diagnostic model for enclosed bay habitat degradation was established, with which the spatial and temporal variation patterns of habitat degradation during 1991–2012 in Sansha Bay, Fujian, China was investigated. The results show that anthropogenic disturbance is the major controlling factor for the habitat degradation in large temporal heterogeneity in the bay. On the other hand, the habitat degradation experienced signifi cant spatial variations among six sub-bays. Under the joint action of temporal and spatial heterogeneity, the degradation trend in growing scale shows a more signifi cant correlation with the distribution of local leading industries along shorelines. Therefore, we quantifi ed the main characters of habitat degradation in Sansha Bay, and have understood the relationship between the status of habitats spatio-temporal variation value and the main controlling factor leading to the changes. However, a defi ciency of this research is the lack of or inaccessible to the detailed data, which shall be better solved in the future study for accessing more data from more sources.

A STUDY ON DESERTIFICATION OF WEST JILIN PROVINCE BASED ON REMOTE SENSING AND GIS TECHNIQUES

'West Jilin Province' in this paper means Zhenlai, Baicheng, Taonan, Da'an,Tongyu, Fuyu, Songyuan, Qian'an, Changling, also includes Gongzhuling, Shuangliao, Lishu, Siping andNong' an which have been suffered from desertification. In west Jilin Province there are three sandzones passing through, they are Xiang (Xianghai) -Wu (Ulan Tug) sand zone, Hai-Feng sand zone, andTao'er River right bank sand zone. The desertification area of west Jilin Province is 819 100 ha,making up 12. 5% of the total land area. Among desertification types, in Jilin Province lightdesertification is the major, then is medium decertification, hevey desertification is the least.According to the comparison of the interpretation results of the Landsat images of the 1980s and the1990s by remote sensing and GIS techniques, it can be seen that the desertification area in westJilin Province basically didn't change on the whole, only increased 6130 ha, making up 0. 8% of thedesertification area, change scale is less than 1%. Evidently, desertification is controlled mostly,but some areas are continuing deterioration. The desertification process of China can be dividedinto three types according to origin nature, they are sandy steppe desertification, fixed sandarea(sand land) activation and dunes transfer invasion. Reasons of desertification of West JilinProvince are analyzed, they include natural factors (such as material source factors, chimatefactors) and artificial factors (such as destroying grass to reclaim, steppe decreasing greatly,illegally feeling shelter forest stands, constructing reservoir to influence eco-environment etc. ).Some suggestions are put forward as follows: establishing the social project for ecologicalreconstruction of degenerated land; intensifying planning and management of land use, revertingfarmland into forestland or pasture in a planned way. The key desertification control is to dependmainly on policy and management, then control techniques.

Application of Remote Sensing and GIS Technology to the Study of Desertification of Arable Lands in North Shaanxi, China

The policy of the Chinese government concerning the horizontal expansion of the cultivated land through the reclamation of desert soils result in a total increase of 665.985 km 2 during the period 1987\|1999 in North Shaanxi. This increase is less than the loss in arable land by urbanization. The accelerated rate of change in agricultural areas calls for more rapid surveys of urbanization and loss of arable land. Remote sensing has a number of advantages over ground\|based methods for such surveys. The multi\|scale concept of remote sensing data help us study the problem in four towns. Several maps were produced to analyze the situation of urban coverage in different times. The evaluation of the status, rate and risk of urbanization are based on an accepted average of urban increase as 2% of population growth per year.

Sedimentation effects of the Dongting Lake Area

According to a long series of measured sediment data, the sedimentation effects of the Dongting Lake Area （DIP,） were studied in light of the relationship between sedimentation characteristics and resources and environment. The result shows that the long-term deposition and the impact of human activities have led to a cycle of the evolution of sedimentation pattern, resulting in sediment disaster effects and resources effects in the DLA. The main features are as follows： 1） The water beach, silt beach, lake marsh beach, reed beach and other types of beach shaped by sedimentation effects constitute the main body of the giant lake system. 2） The disaster chains are induced, i.e., sedimentation → marshland expansion and reclamation → flood function decline, fish resource depletion, biodiversity reduction dis- aster chain, sedimentation → marshland expansion → floods, water pollution disaster chain, sedimentation → marshland floating vegetation rising → schistosomiasis, rodents virulence disaster chain, sedimentation → flood embankment bursting → land desertification disaster chain. 3） Sedimentation has created about 98.13×10^4 hm^2 of land in the past 55 years. Rational development and utilization of marshland resources have produced tremendous economic benefits.

Geochemistry of Soil Formation in Sonth China SeaIslands

The soils in the South China Sea Islands (SCSI) were divided into three types, namely, phospho-calc soils,skeletisols and coastic solonchaks, which were derived from bio-clastic and strongly calcareous sediments. Incomparison with their parent materials, the phospho-calc soils have higher contents of P, Zn, Cu, Ba, and Cd,which tend to increase gradually with time, and lower contents of Mg, Ca, Sr, B, V, Pb, and Mo, which tendto decrease by degrees with time. The above-mentioned constitnents in skeletisols and coastic solonchaks aresimilar to those in their parent materials except for P and Na. The factors atfecting element distribution aremainly special bioclimate and parent material, meanwhile, resulting in the remarkable iulluence on elementdistribution through soil-forming time.

Diagnostic model construction and example analysis of habitat degradation in enclosed bay:Ⅲ. Sansha Bay habitat restoration strategy

Unbalanced inputs and outputs of material are the root cause of habitat degradation in Sansha Bay,Fujian Province,China. However,the cumulative pollution varies in different geographic locations and natural conditions in the enclosed bay. In this study,hydrodynamic conditions,sediment characteristics,and aquaculture methods were recognized as the underlying causes of spatial heterogeneity in the distribution of nitrogen and phosphorous pollutants,the two major controlling factors of habitat degradation in the bay area. In order to achieve the goal of balancing nutrient inputs and outputs in Sansha Bay,we developed a feasible and practical zone restoration strategy for reasonable adjustment and arrangement of aquaculture species and production scale in accordance with varying hydrodynamic conditions and sediment characteristics in six sub-bay areas(sub-systems). The proposed zone restoration strategy lays a solid foundation for habitat restoration and management in Sansha Bay.

Sandy Desertification Status and its Driving Mechanism in North Tibet Plateau

As the main body of Qinghai-Tibetan Plateau, North Tibet Plateau is one of three major sandy desertification regions in China and also a representative sandy desertification zone of Qinghai-Tibet Plateau. Accordingly, it is an important region for the study of recent sandy desertification processes and formation mechanism. From such aspects as desertified land types, areas and distributions etc., this paper analyses in detail the sandy desertification status on North Tibet Plateau, and qualitatively and quantitatively deals with the main factors that affect recent sandy desertification processes and the driving mechanism. Research results show that North Tibet Plateau is an important sandy desertification region in China characterized with large desertified land areas, diversified types, high severity, extensive distributions and serious damages. Sandy desertification occurrence and development resulted from combined effects of natural factors, anthropogenic factors, natural processes and man-made processes, of which climatic change is the main driving force.

Chronology and Nutrients Change in Recent Sediment of Taihu Lake,Lower Changjiang River Basin,East China

Two short sediment cores named ZS and THS dated by the 210Pb or 137Cs method were collected from the northwest and southwest of Taihu Lake respectivly,and total organic carbon(TOC) and nutrients including total nitrogen(TN) and total phosphorus(TP) were determined to analyze the chronology and nutrients change in recent sediment.The results show that 137Cs activities are low(less than 15 Bq/kg) in the two cores,attributed to the 137Cs migration.Based on 210Pb constant rate of supply(CRS) model,the sedimentation accumulation rates range from 0.13 g/(cm2·yr) to 0.76 g/(cm2·yr) in the ZS core,and from 0.10 g/(cm2·yr) to 0.56 g/(cm2·yr) in the THS core.A remarkable increase in organic matter and nutrients has occurred in the two dated cores since the mid-1980s.The historical changes of organic matter and nutrients in the two cores are consisitent with the monitoring data for surface sediment after the 1960s.The TP accumulation rates after the early 1980s are 0.97 and 0.92 times higher than those from the 1950s to the 1980s in ZS and THS cores,respectively.Higher TP concentrations in the past two-decade deposits of Taihu Lake are due to both diagenetic factors and human activities.

Impacts of land-use change on ecosystem service value in Changsha,China

Changsha,a typical city in central China,was selected as the study area to assess the variations of ecosystem service value on the basis of land-use change. The analysis not only included the whole city but also the urban district where the landscape changed more rapidly in the center of the city. Two LANDSAT TM data sets in 1986 and 2000 and land use data of five urban districts from 1995 to 2005 were used to estimate the changes in the size of six land use categories. Meanwhile,previously published value coefficients were used to detect the changes in the value of ecosystem services delivered by each land category. The result shows that the total value of ecosystem services in Changsha declines from $1 009.28 million per year in 1986 to $938.11 million per year in 2000. This decline is largely attributable to the increase of construction land,and the conversion from woodland and water body to cropland to keep the crop production. In the five districts,there is $6.19 million decline in ecosystem service value between 1995 and 2005. Yuelu District has the highest unit ecosystem service value while Yuhua District has the lowest one. This may be attributed to the greater conversion from cropland and grassland to woodland and water body with the increase of construction land in Yuelu District. It is suggested that the increase rate of construction land should be controlled rigorously and the area of woodland and water body should be increased or at least retained in the study area.

Impact of Land-Use Practices on Sediment Yield in the Dhrabi Watershed of Pakistan

Soil erosion by water is one of the most important land degradation processes in the sloping rainfed lands in Pakistan. A study was conducted in the Dhrabi watershed of Pakistan to evaluate sediment yield associated with rainfall-runoff under various land-use practices. Five sub-catchments with sizes varying from 1.5 to 350 ha were selected for measurement of rainfall, runoff and sediment yield. Soil conservation techniques were also introduced to reduce the soil erosion. All runoff events occurred in the summer especially during monsoon season （July-September）. Sediment yield of two small gully catchments ranged from 4.79 to 8.34 t/ha/yr in 2009, a relatively dry year. In 2010, the annual sediment yield was 8.15 to 12.31 t/ha. Terraced catchment with arable crops produced annual 4.1 t/ha of sediment as compared to 12.31 t/ha by the adjacent gully catchment showing high potential of terraces in reducing erosion. Runoff coefficients calculated for these catchments vary from 0.09 to 0.75. The macro and micro nutrients present in the sediment indicate that these nutrients are being depleted due to soil erosion.