Effects of Different Grazing Intensities on Vegetation Characteristics of Cultivated Pastures in Southern China

[Objective]The paper was to study the effect of different grazing intensities on vegetation characteristics of artificial pasture by plot rota- tion grazing experiment. [Method]Grazing intensity was divided into 2 treatments of heavy grazing and light grazing,and each treatment contained 6 plots,with randomized complete block design. A blank control was set near test plot. Ninety disease-free and healthy 2-year-old Yunling Black Goats with consistent body condition were selected and divided into 2 groups： heavy grazing （ 55） and light grazing （ 35） . The goats were conduc- ted rotation grazing in 6 plots,and the average stocking rates were 12. 6 and 8 goat /hm 2 . The plant height,coverage,underground biomass and pasture plant nutrition of 2 treatments were measured,respectively. [Result]The cocksfoot height had significant difference with control under graz- ing conditions （ P 〈0. 05） ,while the heights of ryegrass and white clover in control plot had no significant difference with that in grazing plot （ P 〉 0. 05） . Grazing intensity had different effects on coverage of different plants; grazing utilization reduced the coverage of cocksfoot and ryegrass, which had little impact on coverage of white clover; viewed from the whole plant communities,the coverage in control plot was greater than that in grazing plot. The underground biomass in 0 -20 cm soil depth in grazing plot accounted for about 90%; with the increase of grazing intensity,un- derground biomass was decreased. The crude protein （ CP） and crude fat （ EE） content of forage decreased,while acid detergent fiber （ ADF） and neutral detergent fiber （ NDF） increased. [Conclusion]The research provided scientific basis for determination of suitable grazing system and sus- tainable utilization of pasture resources.

Study on Vegetation Characteristics & Soil Properties of Secondary Grassland in Farmland Areas Abandoned for Different Years in Minqin Oasis

[Objectives]This study was conducted to investigate the vegetation community characteristics and soil properties of secondary grassland in abandoned farmland areas of different years in Minqin Oasis. [Methods] By the method of space-for-time substitution, the changes of vegetation community characteristics(species composition, structural characteristics and important values) and soil microbial and enzyme activity were determined, and the correlation between various soil factors was analyzed. [Results](1) There were 39 species belonging to 32 genera of 15 families in the research area, including 8 shrub plants, 15 perennial herbs and 16 annual herbs.(2) Soil microbial biomass carbon, nitrogen and phosphorus contents were higher in the upper layer than in the lower layer, and the phenomenon of “surface aggregation” was obvious. The differences were different with the change of abandoned years.(3) Soil catalase content was the highest among different plots, and soil phosphatase, sucrase and urease all showed a trend of fluctuating decline with the increase in abandoned years. Soil enzyme changes were different in different soil layers. [Conclusions] This study can provide a theoretical basis for the restoration, reconstruction and rational protection and utilization of secondary grassland in abandoned farmland.

Formation and ecological response of sand patches in the protection system of Shapotou section of the Baotou-Lanzhou railway,China

The development of bare patches typically signifies a process of ecosystem degradation.Within the protection system of Shapotou section of the Baotou-Lanzhou railway,the extensive emergence of bare sand patches poses a threat to both stability and sustainability.However,there is limited knowledge regarding the morphology,dynamic changes,and ecological responses associated with these sand patches.Therefore,we analyzed the formation and development process of sand patches within the protection system and its effects on herbaceous vegetation growth and soil nutrients through field observation,survey,and indoor analysis methods.The results showed that sand patch development can be divided into three stages,i.e.,formation,expansion,and stabilization,which correspond to the initial,actively developing,and semi-fixed sand patches,respectively.The average dimensions of all sand patch erosional areas were found to be 7.72 m in length,3.91 m in width,and 0.32 m in depth.The actively developing sand patches were the largest,and the initial sand patches were the smallest.Throughout the stage of formation and expansion,the herbaceous community composition changed,and the plant density decreased by more than 50.95%.Moreover,the coverage and height of herbaceous plants decreased in the erosional area and slightly increased in the depositional lobe;and the fine particles and nutrients of soils in the erosional area and depositional lobe showed a decreasing trend.In the stabilization phases of sand patches,the area from the inlet to the bottom of sand patches becomes initially covered with crusts.Vegetation and 0-2 cm surface soil condition improved in the erosional area,but this improvement was not yet evident in the depositional lobe.Factors such as disturbance,climate change,and surface resistance to erosion exert notable influences on the formation and dynamics of sand patches.The results can provide evidence for the future treatment of sand patches and the management of the protection system of Shapotou section of the Baotou-Lanzhou railway.

Investigation on biological activities for combating desertification in the western shores of Lake Urmia,Northwest Iran

Lake Urmia,Northwest Iran,has confronted a drying procedure in recent years with losing 90%of its water body.The authorities concerned about desertification processes and possible dust events throughout the region.In this regard,the Iranian Natural Resources and Watershed Management Organization has taken ecological measures to plant vegetation using salt cedar(Tamarix ramosissima Ledeb.)shrubs to combat desertification.This study aimed to investigate the vegetation and soil characteristics of natural and plantation stands of salt cedar on the western shores of Lake Urmia.To this end,7 transects were randomly selected with 15 shrubs in natural stands,and 7 transects were randomly selected with 15 shrubs in the plantation parts along the planting rows.Then,vegetative characteristics were examined.Also,soil samples were taken from the vicinity of the shrubs.The results indicated that there was no significant difference between the mean diameter at breast height(DBH)of salt cedar in natural sites.There was a significant difference between the mean number of sprouts per sprout-clumps,mean crown diameter,collar diameter,total height,and also between mean crown diameter and freshness of shrubs among different sites(P<0.05).It was also found that soil variables,such as clay content,organic matter,electrical conductivity(EC),Na^(+),specific absorption rate(SAR),Cl^(-),SO_(4)^(2-),Na^(+),K^(+),and PO_(4)^(2-) are the most significant variable parameters between studied sites.As the results shown,the values of EC,SAR,Na^(+),and Cl^(-)are 6 times higher in the planted stands than in the natural stands of T.ramosissima.Also,the colonization of T.ramosissima in the planted stands is unsuccessful by dramatic drop in the total height and average diameter.Considering the role of soil characteristics in explaining the variance of data and site separation,it seems that these indicators can be applied in executive plans as important indicators to identify suitable planting sites for combating desertification.

Remote Sensing Study of Gold Biogeochemical Effects in the Western Guangdong-Hainan Region——A Case Study of the Hetai Gold Deposit

The vegetation has been poisoned by gold in the western Guangdong-Hainan region. The gold content ofthe leaves there is as high as 10-1961 times the abundance, the chlorophyll content is 10%-30% lower thanthat of the vegetation in metamorphic terrains and 10%-20% higher than that in granite terrains, and thecarotenoid content is 10%-44% lower than the background value. The water content of leaves is 10% to 20%lower than the background value. The cells of leaves are deformed and broken. The leaf surface shows colourspots and becomes yellow or dark green. The spectral reflectance of the leaf surface is 5%-30% higher than thebackground value: the spectral shape has shifted 5-15 nm to the short wavelength. The gray scales of eanopyon images of Landsat TM and airborne imaging scanner (AIS) are 10%-100% higher than the backgroundvalues. On Landsat TM and AIS false colour images, plants poisoned by gold display a yellow color, whichdisinguishes them from background plants. According to the spectral and image features of goldbiogeochemical effects, the author has constructed a gold information system and expert prediction system,and thus two gold target areas and two gold prospect areas have been identified rapidly, economically andaccurately in the western Guangdong-Hainan region which is extensively covered by vegetation.

Quantifying the characteristics of particulate matters captured by urban plants using an automatic approach

It is widely accepted that urban plant leaves can capture airborne particles. Previous studies on the particle capture capacity of plant leaves have mostly focused on particle mass and/or size distribution. Fewer studies, however, have examined the particle density, and the size and shape characteristics of particles, which may have important implications for evaluating the particle capture efficiency of plants, and identifying the particle sources. In addition, the role of different vegetation types is as yet unclear. Here, we chose three species of different vegetation types, and firstly applied an object-based classification approach to automatically identify the particles from scanning electron microscope（SEM）micrographs. We then quantified the particle capture efficiency, and the major sources of particles were identified. We found（1） Rosa xanthina Lindl（shrub species） had greater retention efficiency than Broussonetia papyrifera（broadleaf species） and Pinus bungeana Zucc.（coniferous species）, in terms of particle number and particle area cover.（2） 97.9% of the identified particles had diameter ≤10 μm, and 67.1% of them had diameter ≤2.5 μm. 89.8% of the particles had smooth boundaries, with 23.4% of them being nearly spherical.（3） 32.4%–74.1% of the particles were generated from bare soil and construction activities, and 15.5%–23.0% were mainly from vehicle exhaust and cooking fumes.

Use of ciliate communities for monitoring ecological restoration of grain for the green in north-western China

A 1-year baseline survey was conducted in north-western China to evaluate the ecological restoration quality of grain for green(GFG)using soil ciliate communities.The aims of this study were focused on analyzing the changes of soil ciliate communities in four plots(A,GFG for 15 years;B,GFG for 13 years;C,layland;D,cultivated land)for GFG environmental assessment.Simultaneously we studied the effects of vegetation communities and physical-chemical variables with GFG changes on soil ciliates.A total of 114 species of ciliates were identified among the four sample sites,representing 9 classes,14 orders,22 families and 37 genera.The community patterns of the soil ciliates were significantly correlated with the individual abundance of aboveground plants,soil water content,and soil porosity.The contents of total nitrogen were the main factor affecting the soil ciliate community composition.The species number,individual abundance,and diversity index of the ciliates were each in the order A>B>C>D;that is,the community composition of ciliates was complicated with the implementation of the GFG.It was shown that the succession of ciliate community shifts toward promoting the complexity with the progress of GFG.These findings demonstrate that soil ciliate communities may be used as a useful indicator to evaluate the effects of the ecological restoration quality of GFG.