Niche refers to the space-time position of a population occupied and the functional relationship between it and related population.Niche including the requirements of the species on the environment and the influence of environment on species,it reflects the interaction between species and habitats quantitatively.Density-dependent is one of the important selecting pressure in nature,which makes the ground light competition between the neighborhood.by changing the number of populations within each plant availability of resources.Therefore,niche and density gradient are inseparable.To analyze the dynamic distribution rules of niche of mixed pasture from the density gradient is a significant approach to study the strategy of plant population ecological adaptation.Study sites are located in the HuangCheng town(37°58'26″ N,101°47' 34″ E) which belongs to an upper reaches ShiYang River,SuNan county of alpine region(2530 m) lying in the north of Qilian Mountains.In replacement series experiments,the two species of planting densities were varied but the total density was held constantly.It was used to build mixed-seeding meadow of Avena sativa L.and Vicia vilosa Roth in June 15,2010.This study set up seven grass-legume seeding ratios: KY(1∶0),A(8∶2),B(6∶4),C(5∶5),D(4∶6),E(2∶8),KM(0 ∶1) which maintains about 300 plants total density constantly.There are total of 21 plots(2 m × 5 m) adopted randomized block arrangement with three replications.We recorded the phonological period,plant-height and branch(tiller) number of mixed grasses every 10 days started from July 17,2010 to August 27,2010.The sampling area is 50 cm × 50 cm in every plot,the mixed grasses were separately placed into an oven at 65 ℃ for 8 hours according to the block order until it reached the constant weight,thus the biomass were recorded respectively.Niche breadth is the metric of plants scale on environment and natural resource utilization,niche overlap occurs when two or more species to take possession of or make use of a certain kind of resources(space,nutrient content,food,etc) together.Under density dependant,the niche breadth of Avena sativa L and Vicia vilosa Roth and the niche overlap of the two species transfer occurred to some extent during the growing period of grasses.The results showed that:(1) With the growth of forage,the density of Avena sativa L niche breadth decreases gradually and Vicia vilosa Roth showed a gradually increasing tendency in all group of mixed grassland,niche overlap of Vicia vilosa Roth and Avena sativa L.showed a reducing tendency.(2) In mixed grassland with Avena sativa L relative density decreases and the relative density increase of Vicia vilosa Roth..Avena sativa L niche breadth decreases gradually and Vicia vilosa Roth showed a gradually increasing tendency,the niche overlap of Avena sativa L and Vicia vilosa Roth increases gradually.To sum up,in the course of grass growth,density dependence lead the resource allocation strategies of the two mixed pasture response to intraspecific,interspecific competition adjusted.Mixed pasture competition ability' s change led to its niche in a certain degree of metastasis and differentiation,which made the relationship between species and community structure tend to be stable.To form a mutual stability and mutual influence ecological system,achieve maximum resource utilization.

Plant can adjust its root length density and distribution pattern to optimize its resources utilization pattern.In this study,the mixed-sowing grassland of gramineous grass Avena sativa and leguminous grass Vicia villosa with the density ratio of 0:10(CK1),8:2(Ⅰ),6:4(Ⅱ),5:5(Ⅲ),4:6(Ⅳ),2:8(Ⅴ),and 10:0(CK2) was established in the upper reaches of Shiyang River in Sunan County of Gansu Province,Northwest China in 2010,aimed to study the spatial distribution patterns of root length density of the two mixed-sowing grasses.The root length density(RLD) of the two grasses was greater in mixed culture than in mono-culture.With the decrease of A.sativa density in mixed-sowing grassland,the RLD of the grass had a gradual increase,showing a phenomenon of high A.sativa density and low A.sativa RLD.Spatially,the RLD of A.sativa and V.villosa had obvious difference.A.sativa roots were mainly distributed in 0-25 cm soil layer,while V.villosa roots were concentrated in 0-15 cm soil layer.The hierarchical distribution of the roots changed their competition pattern,and the difference in the vertical distribution gradually changed the root structure and morphology.In the treatments except CK1 and CK2,the taproot growth was restrained,while the lateral root growth was promoted.The spatial hierarchical distribution of the lateral roots in the mixed-sowing grassland changed the resource utilization pattern,and gradually optimized the root length density configuration pattern,which achieved the goal of maximizing the resources utilization from soil.

Competition is a common phenomenon among plant communities, especially among natural communities. It is an important factor in biology and plant–plant interactions has inspired an increasing concern in recent years. The investigation of inter-specific competition is useful to reveal the mechanism in plant growth and reproduction of organisms. Plant root systems play an important role in uptake of water and nutrients from soil for plant growth. However, it is still a divergent topic about the regulating mechanism between root morphological variations and competition. The spatial distribution, morphology of plant roots and above-ground growth can be influenced by inter-specific interactions. Their morphology characteristics and structure distribution were studied to reveal the adaptive mechanism of roots system in the soil environment. The deWit series experiments were conducted to study the relationship between relative competitive ability immixture and monoculture along seven levels of density at the experiment station of Shiyang river in Sunan country of Gansu province in 2010 (latitude 37°58′26′′N, longitude 101°47′ 34′′E). It was carried out to analyze inter-specific interaction between Avena sativa L. and Vicia villosa Roth. Taking the roots both A. sativa L. and V. villosa Roth as the research object, the WinRHZO was used to measure the changes of root length, diameter, surface area and so on. To evaluate the competitive responses and the competitive effects of target plants, the plant combinations with A. sativa L. and V. villosa Roth were established in plots in seven replacement grass–legume combinations (monoculture of A. sativa L. and V. villosa Roth, and mixed culture of A. sativa L. and V. villosa Roth with the ratios: 8:2, 6:4, 5:5, 4:6, 2:8).

The copolymerization of MMA with ethylene was promoted by metallocene complex in the presence of initiator tetra(2,3-epoxy propoxy)silane (I-s), reducing agent Zn and cocatalyst MAO, combining free radical polymerization with coordination polymerization via sequential monomer addition strategy in one-pot to produce 4-arms hydroxy-functionalized PMMA-b-PE. The effects of polymerization conditions such as temperature, time, ethylene pressure and Al/Ti molar ratio on the polymerization performance were investigated. 4-Arms hydroxy-functionalized PMMA-b-PE was obtained by solvent extraction and determined by GPC, MALLS, DSC, FT-IR, WAXD and H-1(C-13) NMR. The DSC result indicated that the 4-arms hydroxy-functionalized PMMA-b-PE had one T-g at 87.0 degrees C and one T-m at 117.0 degrees C which attributed to T-g of PMMA segment and T-m, of PE segment, respectively. The microstructure of 4-arms hydroxy-functionalized PMMA-b-PE was further confirmed by WAXD, FT-IR, and C-13 NMR analysis. These results demonstrated that the obtained 4-arms block copolymer consisted of PMMA segment and crystalline PE segment. (C) 2013 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

蝗虫空间分布格局是物种长期适应自然的结果,是蝗虫与环境、蝗虫之间关系的反映,有助于理解蝗虫发生学的环境背景。采用地统计学方法,在黑河上游山区天然草地研究了微生境影响下的蝗虫空间格局与异质性。结果表明:该区域5种优势种蝗虫的半变异函数模型均为非线性模型,表现为聚集分布;不同种类蝗虫样点之间空间依赖的范围为2.29—24.59 m;在蝗虫种群总异质性中随机部分引起的空间异质性占15.77%—88.64%。受食性和栖息地选择的影响,蝗虫种群形成了片状和斑块状的分布格局;尺度依赖性使蝗虫分布格局趋于多元化和繁杂化的特点,不同蝗虫种群之间相互交错嵌插,同种蝗虫高低值呈非均匀扩散,整体上形成了均衡性与互补性的斑块镶嵌结构,这种分布格局反映了蝗虫对生境和气候变化的多元适应性结构。

The intensity and transformation of intra-and inter-specific competitions in mixed sowing grassland is affected by the relative density of mixed sowing grass species.From June to September 2010,a replacement series experiment was conducted to establish an Avena sativaVicia villosa mixed sowing grassland in the upper reaches of Shiyang River.Seven treatments with the relative density of A.sativa and V.villosa being 1:0(KY),8:2(A),6:4(B),5:5(C),4:6(D),2:8(E),and 0:1(KM) were designed to study the changes of the interspecific competition between annual grass species in mixed sowing grassland under effects of the grasses densities.Affected by the relative density of A.sativa and V.villosa,the intra-and interspecific competitions of the grass species in different phonological periods were transformed in different degrees.In all mixed sowing treatments,the relative yield of A.sativa(RYy) increased with its growth,while the relative yield of V.villosa(RYm) decreased with its growth in treatments A,B,and C but increased in treatments D and E.At the seeding and tillering stages of A.sativa,the two grass species were in a hostile relationship(RYT 1) in all mixed sowing treatments except A,but at later growth stages of A.sativa,the relationship transformed to symbiotic(RYT1) in all mixed sowing treatments,and the competition of A.sativa was stronger than that of V.villosa(RCCy1,RCCm1).The competition in all mixed sowing treatments was beneficial to A.sativa(AG 1) in its whole growth period.It was suggested that the intra-and inter-specific competitions in mixed sowing grassland in each phonological period showed an obvious density-dependent phenomenon,realizing the cooperative use of resources between the mixed sowing grass species.

By substituting spatial difference for time change,seven major natural communities representing the succession series of degraded woodland from herbage community to tree community at altitudes from 2468 to 2761 m on the northern slope of Qilian Mountains were selected to measure the species diversity in shrub layer by multiple indices,and the species overall interspecific association and dominant species interspecific association in the shrub layer of the communities at different succession stages were analyzed by variance analysis and χ2 test.Up to 19 shrub species belonging to 10 families and 16 genera were investigated.The results showed that in shrub layer,the species number and Gleason index were the greatest in Picea-Betula community,the Simpson index and Shannon-Wiener index were the greatest in Betula community,the evenness index was the greatest in Potentilla glabra community,and the dominance index was the greatest in Picea crassifolia community.Except for Betula-Populus community,all the other communities had a larger number of shrub species pairs with negative association than with positive association,reflecting the interspecific competition relationship of shrub species in the succession series.With the succession of the communities,the interspecific association of most shrub species pairs changed with succession stage,i.e.,insignificant at early stage,significant or very significant at middle stage,and null or insignificant at late stage.The species overall interspecific association was negative in the restored shrub community at early stage and in the broadleaved forest dominated by heliophytes,positive in the mixed coniferous forest dominated by heliophytes,negative in the mixed coniferous and broadleaved forest,and positive in the coniferous forest dominated by mesophytes.The changes in the species diversity and interspecific association among the shrub species pairs in the succession series could be related to the niche separation or niche overlapping caused by the stratification of community structure from the ground to the community's top crest.

Plant functional types(PFTs) are important in understanding the dynamics and the functions of an ecosystems,which provide also useful information for ecosystem management.In 28 observation plots of a naturally recovered poplarbirch woodland on the north slope of Qilian Mountains,China,81 plant species were classified into 18 plant functional types(PFTs),according to their life forms(including arbors,lianas,subshrub,shrub,perennial grasses,perennial forbs and annual or biennial grass) and ecotypes(including xerophyte,xerophytic and mesophytic,mesophyte and hygrophyte).The relationships between PFTs and environmental factors were studied using Canonical Correspondence Analysis(CCA).The results showed that the dominant PFTs were PFTs16(mesophytic perennial forbs),PFTs23(hygrophytic perennial forbs),PFTs9(xerophytic and mesophytic perennial forbs) and PFTs18(mesophytic shrub) on the poplar-birch restoration woodland.The stratified structure with wood,shrub and herb layers indicated the plant life forms had a tendency of complication and structurization,and the emerging mesophyte plants reflected changes of the micro-environments.The distribution patterns of PFTs were controlled by the soil physical and chemical properties in that soil bulk density,soil organic carbon and content of nitrogen determined the characteristics of the plant life forms,while the soil water moisture and canopy cover were the main ecological factors that affected the distribution of ecotypes.The slope position and slope aspect controlled the plant distribution pattern and formation of the community.Fig 1,Tab 3,Ref 31

We studied the species composition and dynamics of diversity in the process of vegetation restoration of degraded forest that was under artificial rearing during 2001-2008 on the Northern Slope of Qilian Mountains, using long-term observation methods. The results showed that: After removing human interference, the degraded forest experienced five restoration stages, such as mountain meadow, herbaceous-shrub, shrub-herbaceous forest, shrub-tree mixed forest and tree-shrub mixed forest. With the restoration time going, the  diversity index showed supraterraneous stratification. On the prophase of restoration, the  diversity index of herb community was highest; so the turnover rate of species was quickly. However, resource heterogeneity of shrub and tree community strengthened at the middle and final stages of restoration, the turnover rate of species become slowly. As a whole, with the progress of vegetation restoration, community species composition and diversity keep on increasing and tend to complex, the difference of species composition increase, so the ecological function of community get preliminary recovery.

Spatial distribution pattern,spatial association has a strong dependence on the scale,population in different scales often shows a variety of spatial pattern and spatial association.Stellera chamaejasme widely distributed in northen grassland in China,and the population has assumed a spreading tendency,so understanding the relation inside population as well as intra plant,inquiring the coexist mechanism of Stellera chamaejasme population and improving the diffusion principle which were siginficant to understand diffusion mechanism of poisonous weed in aird area.In Auguest,2009,station a 4 m×4 m plot in Kangle grassland(38°47′15.8″ N,99° 43′ 35.9″ E) Sunan Country in the upper reaches of Heihe,Gansu Province,China.We recorded every one's specific location,at last,323 Stellera chamaejasme plants were been counted in the plot.In our eexperiment,four grades were divided by shoot number of Stellera chamaejasme cluster,i.g: cluster gradeⅠ,Ⅱ,Ⅲ and Ⅳ,among which 244 individual plants was on Ⅰ level and accounted for 75.5% of the total,50 individual plants was on Ⅱ level and accounted for 15.5% of the total,20 individual plants was on Ⅲ level and accounted for 6.2% of the total,9 individual plants was on Ⅳ level accounted for 2.8% of the total.Calculating the measured value L(d) and the value of upper and lower envelopes by the Visual Fortran 6.5 based on the coordinate getting by GetData Graph Digitizer 2.22,the plot software was Origin 7.5.The results showed as follows: with the development of population,the spatial distribution pattern transfered from clumped to random gradually at fine-scale,theⅠgrade population showed clumped pattern at 0-1.35 m scale,it was clumped pattern at the 1.35-1.68 m scale and it was regular pattern at 1.68-2 m scale,Ⅱ grade population showed two spatial distribution patterns,it showed clumped pattern between 1.48 and 1.52,it was random pattern at other scale,Ⅲ and Ⅳ grades population showed random at all scale.The spatial association between plants will turn from positive to negative if their size differences are enlarged increasing,with the growth of population,the spatial association gradually transferred to non-significant.Then spatial association tended to complex at more bigger scale.So a clearer recognition be acquired by researching the distributing process of Stellera chamaejasme population,the population experienced six stage: form patchs-patchs disintegrate-form new patchs-merge patchs-patchs disintegrate-individuals died,the shelter among individuals promoted the increasing of population quantity,at the same time,which enlarged the patch by intracompetition,so the Stellera chamaejasme population has beening occupied more space and resources,finally the transformation between cooperation and competition completed population diffusion.

The research of the performance of resource management,basing on resident perception,can evaluate roundly the response of resident to the participatory wetland management.The authors studied the deviations and loopholes in the process of management,which is convenient for improving the operability,effectiveness and sustainability of control measures.Taking Liu Fen wetlands in the middle reach of the Heihe River as example,the authors evaluate the management performance from perception views,using the methods of factor analysis and semi-construct interview sample investigation,from 5 dimensions which are community image,ecological benefit,economical benefit,scientific culture and industrial structure.The results show that perceived value of each dimension is all above 3.4,the mean of total perceived value is 3.71.The mode of participatory resource management was suitable for social ecological and environment development of research area and the management performance is significant.Judged from different dimensions,the mean of social image dimensions is the highest(M1=3.95),which shows that the effective integration of different cultures,community management mode of wetlands and realization of democratic rights enhanced the internal community image,the construction of wetland protection facilities and community infrastructure increased community external image.The evaluation of resource management based on residents' perception,respects the value judgments of stakeholders,focuses on the regional cultural,environmental background and comprehensive needs of the residents,and evaluates integrally resource management performance in quantitative methods.

Spatial distribution pattern is important in plant ecology as it affected the dynamics of plant populations,communities and ecosystem processes,which can reveal the dynamic and stability of population and community structure.Stipa krylovii,the zonal vegetation in alpine degraded grassland,has a great significance for understanding ecological processes and sustainable utilization of grassland resources with studies on population patterns of S.krylovii.Study sites locates in the MaChangtan grassland in SuNan country of the north Qilian Mountain(38°47′22.1″—38°52′11″ N,99°45′11.7″—99°57′41.2″ E).with the altitude of 2610—2632 m,the annual temperature of the region is 1—2 ℃,the annual precipitation varies within a range of 270—350 mm,the soil is mainly consisted of mountain chestnut soil,the dominant native vegetation in the region is consisted of perennial grasses and forbs.In July 2010,we recorded fine-scale(0—100 cm) spatial patterns of S.krylovii from 2 m × 2 m grids(2 cm × 2 cm quadrats) in four plots under four kinds of degradation gradients according to community characteristics,population characteristics of S.krylovii,and grassland stocking rate for nearly 10 years: no degradation(90%),light degradation(105%—125%),moderate degradation(123%—138%) and heavy degradation(135%—150%).The point pattern analysis and Monte Carlo stochastic simulation method were used to quantitatively analyze S.krylovii population patterns by the software of GetData Graph Digitizer 2.22,VisualFortran 6.5 and Origin 7.5.Based on life history traits,bunch structure,patch characteristics and strategies of ecological adaptation in the community,the mechanisms generating and maintaining these patterns were discussed.The results showed that: First,there were significant effects on patch characteristics of S.krylovii population under the different degradation gradient.The density and population territory area of S.krylovii population in heavy degradation was significantly lower than no degradation,but its total area of hole in heavy degradation was greater than no degradation,and territory density increased firstly and then reduced.Second,the bunch structure of S.krylovii population existed complicated relationships.The small bunch of 0.1—1.0 cm in heavy degradation was greater than no degradation.At the same time,the proportion of big bunch was significantly higher than others in no degradation.Third,there was a difference at different scales.Under no degradation conditions,the spatial patterns of S.krylovii were regular at 0—64 cm scales,but aggregated at 64—100 cm scales;under light degradation conditions they were random at 0—100 cm scales;under moderate degradation conditions,the spatial distributions were random at 0—70 cm scales,but aggregated at 70—100 cm scales;under heavy degradation conditions,there was random as a whole and the scale ranges was from 0 cm to 100 cm.In contrast,the population patch is the basic functional unit of S.krylovii,which can decide the status and role of S.krylovii in the community.Under the role of grazing and interspecies competition,population patches may crumble from center to the edges gradually,and it lead to the spatial patterns changed.Finally,S.krylovii declined in alpine degraded grassland along with population patch broken and mattic epipedon disappeared.

Heterogeneity for response of plant populations to soil moisture is the environmental basis of their pattern formation and evolution.Melica przewalskyi is rhizomatous clonal grass with strange taste and not edible for grazing animals.With the infuluence of climate change and overgrazing,in the northern slope of Qilian Mountains,the Melica przewalskyi gradually formed a great number of single dominant species patches due to their biological characteristics and the adaptbility to adversity.Therefore,it is very important to understand their biologic characteristic of population distribution,distribution patterns and the soil moisture,and study the change of their population characteristic and soil moisture and the mechanism in the process of patch formation and recession.It is critical for revealing the plasticity mechanism of soil moisture and understanding the conspiracy relationship between the plant and the environment.The experiments were conducted in Yue ya ai grassland(38°47′15.8″N,99° 43′ 35.9″E)which is located in the upper reaches of Shiyang river in Sunan country Gansu province,China.In early August,2010,three different patches in the different stage,such as formation stage,diffusion stage,stable stage and recession stage respectively were selected in the study area.Square quad rat was made using red chopstick and sample line,the patches were places into quad rat,the quadrats center was founded by diagonal of 4 fixed vertice,thus red chopsticks were used to state the quadrat center position.sampling points were set from centre to four directions,thesampling point on each direction was selected at least 50 cm,adjacency grid sample in each point was used,the coverage was measured using the needle puncturing method in 50 cm × 50 cm sample box and tested the density of Melica przewalskyi in the same sample box by counting,measuring the natural height by tape repeat six,recording the relative position of each plant and determine the moisture content of 0—20 cm by oven drying method.the measured value L(d) and the value of upper and lower envelopes were calculated by the VisualFortran6.5 based on the coordinate getting by GetData Graph Digitizer2.22,Origin7.5 was used as the plot software,this plot in the lower left corner coordinate origin to the intersection,using the step of 5 cm,the number of Monte_Carlo stochastic simulation is 20 times,dashed line are the 95% confidence envelops for the same process.The results showed that:Melica przewalskyi population spatial pattern transitted from clumped to random distribution at four stages,soil moisture tended to increase from center to edge of patch;Melica przewalskyi patch diffused to the high soil moisture with concentric circles way during the formation stage,diffused stage and stable stage,and the radius of patch expand from 0.5 m to 1.5 m,the population height,density and coverage were decreased from center to edge of patch;And then the center of patch appeared naked at recessionary stage,the height,density and coverage increased progressively from center to edge of patch in concentric circles way.The spatial pattern and main biological characteristics showed different correspondence relationship with soil moiture at different stages.

The big-scalespatial heterogeneity of grasshopper nymps from the first to the fifth age in natural grass of various elevations in the upper reaches of Heihe river basin was analyzed with geographical statistic methods, indicating an aggregated spatial arrangement and horizontal distribution.The results showed that the spatial pattern of different ages was of aggregated distribution,with age,aggregation degree turning into old dispersive larva from young aggregated larva and the scope of spatial dependence expanding gradually.The features of spatial autocorrelation tended to be in an inverted U-shape whose peak was the fourth age.The trend of spatial distribution focused in northeast-southeast and northwest-southeast and continuously increased with the age; the trend of spatial distribution strengthened in northwest-southeast,while it weakened gradually in northeast-southwest. Vertical differentiation was obvious at intermediate elevations.The distribution pattern formed an interlace structure just like strips that were balanced and complementary,so the process of aggregation and spatial heterogeneity reflected the order of nymphs' coming out of ground and their adaptability to the climate.

The star-shaped polymethylmethacrylate (PMMA) was synthesized via radical polymerization promoted by metallocene complexes in the presence of initiator of tetra(2,3-epoxy propoxy)silane (Is) and reducing agent Zn. The effect of temperature, time, molar ratio of monomer to initiator, and the structure of metallocene complexes on the polymerization performance was investigated. The structure and properties of the obtained polymer were characterized by gel permeation chromatography, multiangle laser light scattering, H-1 NMR, C-13 NMR, and WAXD. The results indicated that the obtained polymer was atacticspecific and featured narrow molecular weight distribution (1.30-1.57). Star-shaped organosiloxane-functionalized PMMA was produced. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 1652-1658, 2011

By the methods of point pattern analysis and spatial sequence instead of time series,this paper studied the fine-scale spatial pattern of Stellera chamaejasme population in the degraded alpine grassland in northern slope of Qilian Mountains.With the increasing coverage of S.chamaejasme,its individual number decreased after an initial increase,young plants transited from random distribution to clumped distribution,aggregation intensity weakened after an initial strengthening,and elder plants showed a random distribution.When the coverage was lower,the S.chamaejasme population had a random distribution at 0-100 cm scale;when the coverage was higher,the distribution pattern transited from clumped to random with the development of the population.The spatial pattern had close correlation with the dispersion stage of the population.The dispersion of S.chamaejasme population was realized through the combination and annexation of patches,and the inter-conversion of competition and synergy.

The natural restoration of woodland is important to explain the ecological process in forest ecosystem.It is significant implications to assess degraded woodland dynamics and ecological effects under artificial fostering approach in theoretically and practical for forest biodiversity conservation and sustainable management in semiarid mountains. Study site was located in the Han Quangou basin forest distribution zone in the Qilian Mountains of northwestern China.In this area,the wood of Picea crassifolia has been depleted after logging or grazing disturbance.The wood vegetation had been degraded and changed to shrub,grassland and scattered Betula-Populus secondary forests.In 2001 year,we have established 4 fixed observation plots(10m×10m) along the elevation 50m interval range from 2468m to 2736m.In each plot,we have chose 3 grids(4m×4m) for shrubs,6 grids(1m×1m) for grasses,2 grids(1m×1m) for soil.In August,we have investigated vegetation community characteristics including species number,community coverage,plant density,community height,species frequency and wood diameter at breast height(DBH1cm) in different years woodland(from 2001 to 2008).The soil physical-chemical properties of investigated plot including soil bulk density,soil water content,soil organic carbon and total nitrogen were determined in indoor laboratory.In the study,changes in the species composition and relative important value(IV) of main species,community structure,species diversity and soil properties were analyzed by methods of variance analysis. The results showed that after human disturbance was forbidden,the habitation of woodland became well gradually within 8 years.From 2001 to 2008,the number of family,genus and species of plant community increased apparently.In the process of community succession,former species was replaced by the subsequent species frequently.The Betula platyphylla and Populus davidiana gradually become the constructive species.With shrubs and trees growing up,the vertical height increased,and community structure divided different layer from ground to community′s top crest.From 2001 to 2008,biodiversity index of community increased.Patrick,Shannon-Wiener and Simpson indexes were different at different layer of community,and the order of three index among different layers(from high to low) was herb layer(HL),shrub layer(SL),and tree layer(TL).However,the order of Pielou index was tree layer(TL),shrub layer(SL) and herb layer(HL).Soil bulk density(SBD) decreased from(1.21±0.06)g/cm3 to(0.73±0.04)g/cm3.Soil water content(SWC),soil organic carbon(SOC) and total nitrogen(TN) increased with the woodland restoring. Fencing and forest ban can restore the degraded woodland vegetation in northern slope of Qilian Mountains.Beside the vegetative form,the key species(B.platyphylla and P.davidiana) and the improving of soil moisture and nutrient,which were the main factors of succession process of degraded woodland from herbage community to trees community.When the community was at the stage of mixed vegetation,the species composition,community structure,and diversity were more complex than those in other stages.At the same time the soil quality was improved by vegetation restoration ecological.Therefore,adaptation ability of vegetation was high in the mixed vegetation stage of shrub and trees,which showed a good restoring effect.

Plants can adapt to interspecific competition by adjusting their growth behaviors and morphological characteristics at their different growth stages.In this study,a grassland with mixed sowing Avena sativa and Vicia vilosa was established in Qilian mountainous region,aimed to understand the interspecific competitive relationships of the two annual species at their different phonological phases.To evaluate the competitive relationships,the relative yield(RY),relative density(RD),and relative yield total(RYT) of the two species were measured.It was observed that the interspecfic relationships of the two species changed with phenological phase.At seeding stage,there was a strong competition between the two species,manifesting in the mutual limitation of relative number and the slow increase of plant height and leaf number;at tillering stage,the interspecfic competition transformed into interspecfic collaboration,manifesting in the rapid increase of tiller number and leaf number and the increasing RYT;at jointing stage,V.vilosa started to increase its relative number,which limited the development of A.sativa and caused strong intraspecfic competition;at grain-filling stage,the intraspecfic competition transformed into interspecific competition again.Through the adjustment of morphological plasticity at different phonological phases,the two species better responded the transformation of their interspecfic relationship.

Comb-like hydroxyl functionalized atactic polystyrene was synthesized using the catalytic system ( n-BuCp )2TiCl2/Sn/I8 via living radical polymerization with Sn as the reducing agent and poly- [ ( phenylglycidyl ether)-co-formaldehyde] (I8) as the initiator. The effect of polymerization conditions, such as temperature, time, as well as the ratio of initiator to monomer on the polymerization performance was investigated. The catalytic active center was stable at the temperature range of 65 ∼95°C ,and the propagation rate increased with temperature. The structure and the properties of the obtained polymer were characterized by GPC ,13 C-NMR, WAXD and1 H-NMR. The GPC result indicated that a linear dependence of Mn on the monomer conversion was observed in each case,and the resulting polymer exhibited a rather low polydispersity (Mw/Mn = 1.6∼1.9) even the polymerization time (6,8,12,16,18 h) or the ratio of initiator to monomer ([I8]/ [St] = 1/250, 1/500, 1/750) had been changed, which confirmed that living radical polymerization characters prevailed in the polymerization process. The results of 13 C-NMR and WAXD suggested that the polymer is featured by an atactic structure. The 1H-NMR results showed that the polymer molecules possessed hydroxyl groups,and the number of arms in each polymer molecule was in good agreement with the number of epoxy functional groups in the initiator (I8) ,which indicated the radicals derived from ring opening reaction of epoxide were the active species for living radical polymerization of styrene.

Aims The formation and changes of patches has an important effect on population patterns.Our objectives are to determine 1) how patches are formed during the process of Stellera chamaejasme population dispersion,2) what is the effect on pattern during forming and changing of the patch and 3) what roles the formation and changes of the patches play in population dispersion.Methods We studied five 2 m × 2 m plots of different S.chamaejasme cover in the upper reaches of Heihe,China,using the point pattern method to analyze population pattern,size and density.Important findings With increasing cover,the population density and territory density tended to increase,decrease,and then increase and the number of the S.chamaejasme population tended to increase and decrease in turn.In the study area,the pattern under 31%–40% cover at all scales was a random distribution.Under the cover of 41%–50%,51%–60%,61%–70% and 71%–80%,the distribution pattern was random—clumped—random or regular—random—clumped—random and the clumped density was different.It formed patches during the process of S.chamaejasme population dispersion,which was clumped for external and random or regular for internal S.chamaejasme population dispersion through which patches combine and annex.