植物功能性状是连接植物与外界环境的重要桥梁,其在不同环境梯度下的变化表现出了对异质环境的适应机制.本文以敦煌西湖国家级自然保护区克隆植物芦苇(Phragmites australis)为研究对象,设置了未退化、轻度退化、中度退化和重度退化4个梯度样地,研究环境异质条件下芦苇叶功能性状特征及其对土壤环境因子的响应.结果 表明:①各环境梯度下,芦苇叶功能性状特征变化显著(P＜0.05),叶长、叶宽、叶面积、叶干重随环境梯度退化呈下降趋势,比叶面积随梯度退化呈上升趋势;②芦苇各叶功能性状间呈协同变化的特征,叶长、叶宽、叶面积、叶干重之间呈极显著正相关(P＜0.01),比叶面积与叶长、叶干重呈显著负相关(P＜0.05);③叶长、叶宽、叶面积、叶干重与土壤表层(0 ～30 cm)、中层(30 ～60 cm)水分呈显著正相关(P＜0.05),而与土壤表层、中层含盐量呈显著负相关(P＜0.05),说明土壤表层与中层的水分与盐分是芦苇叶功能性状最主要的驱动力.研究结果对于旱区内陆河湿地的保护、生态恢复及管理具有重要的指导意义.

空间拓展是克隆植物响应环境的生态适应和权衡维度,以内陆盐沼湿地典型代表敦煌阳关国家级自然保护区内的芦苇(Phragmites australis)为研究对象,基于水库距离远近和芦苇种群的密度与盖度,设置了近水区(500 m)、过渡区(1500 m)、荒漠区(2500 m)3个不同的采样梯度,研究了环境异质条件下芦苇克隆构件空间拓展策略及其对土壤环境因子的响应.结果 表明:(1)芦苇克隆构件在异质环境条件下差异显著,初级根茎条数、根茎节间长、间隔子长、分枝角度呈现“同增同涨”的协同进化关系(P＜0.01),而与分株数呈现“此消彼长”的权衡关系(P＜0.01).(2)且随着种群的密度降低,芦苇在空间拓展过程中呈现从“密集型”转“游击型”的生存策略.(3)冗余分析显示土壤水分、pH值、盐分是克隆构件空间拓展的主要驱动力,其中各层土壤水分、深层土壤pH值和盐分是芦苇空间拓展最重要的环境因子.明晰内陆河湿地芦苇克隆构件空间拓展策略及主要的环境驱动力,能为干旱脆弱敏感区湿地保护和生态恢复提供借鉴意义.

This study were used the methods of climate tendency rate,spatial analysis,Penman-Monteith model,the temporal-spatial variations,cross wavelet and wavelet coherence to analyze the spatial and temporal variations of AI( aridity index),influencing factors,and the relationship of the AI with AO( Arctic Oscillation) and ENSO( El NinoSouthern Oscillation),based on the data of 29 meteorological stations in Qinghai Province during the period of 1961-2013. The results showed that the average of AI was 0. 49 for many years. The trend of AI fluctuantly reduced in the past 53 years. The average of AI linearly decreased at the rate of-0. 03 ·10 a~(-1)( α = 0. 01) over the study area,which means the climate gradually changes to moist in Qinghai Province. The maximum value and minimum value of AI appeared in December and August,respectively,which showed that the average of AI increased firstly then reduced within a year. The maximum of the AI appeared in northwest of Mangai County and north-central of Golmud City and Nuomuhong Town,and the minimum of AI appeared in southern-central of Maqulai County and Jiuzhi County. The average of AI had significantly positive correlation to sunshine time( P 0. 01) and wind velocity( P 0. 05) in Qinghai Province. At the same time,the average of AI has negative correlation with the temperature,precipitation and relative humidity. In addition,the average of AI is multi-scale significant correlation to AO and ENS in this study( a = 0. 05).

Aims Variations in leaf characteristics can reflect plant acclimation to environments. We aimed to examine the relationship between leaf traits of Melica przewalskyi and slope aspect. Methods In alpine grassland of Qilian Mountains, Gansu Province, China, 80 plots were sampled at intervals of 20 m along eight aspects. Latitude, longitude and altitude of each plot were recorded by GPS. At each plot, 10 individuals of M. przewalskyi were random selected and harvested for measurements of leaf mass, leaf area, and leaf volume. A digital elevation model (DEM) was constructed to extract elevation, aspect, and slope for each plot by ArcGIS. The 80 plots were divided into groups of north, east, west and south aspect. Values for leaf traits were log-transformed. the standardized major axis (SMA) estimation method, was used to examine the covariation among leaf traits. Important findings Leaf area and leaf volume decreased significantly as aspect turns from north to east, from east to west, and from west to south, but not so for leaf mass, suggesting that leaf thickness increased as slope aspect changes, and thus led to the smaller and thicker leaves on the south-facing slope than that on north-facing slope. A clear allometric relationship between leaf mass and leaf area was found only on the south-facing slope where increase in leaf mass was greater than that in leaf area. While on other slope aspects, an isometric relationships between them was observed. The allometric relationship between leaf mass and leaf volume was found on all four aspects, with the growing speed of leaf volume greater than that of leaf mass, and a rising SMA slope. We can conclude that variations in leaf traits of M. przewalskyi with slope aspect could reflect plant acclimation.

•NPP was used to assess the relative role of the driving factors in desertification.•Desertification expanded in 55.8% of the entire study area.•Human activities promote desertification expansion, climate benefits the reversion.•Contributions of the two factors varied greatly in six provinces.•Environmental protect programs are beneficial to the desertification control.

The relationship between flower size and leaf size and number reflects the plant adaptation strategies in external morphology during the long-term interaction of plants with different environments,and the variation of the relationship reflects plant adaptation to heterogeneous environments. In this study,an investigation was carried out to examine the relationship between flower size and leaf size and number of Stellera chamaejasme along four different altitude gradients in an alpine grassland in the northern slope of Qilian Mountains. The results showed that,with increasing elevation,the height,density,and aboveground biomass of the plant communities displayed a pattern of initial increase and then a decline. The aboveground biomass,plant height and leaf biomass of S. chamaejasme declined gradually,while reproductive allocation,flower size and leaf number both increased gradually. Flower size of S. chamaejasme was significantly positively correlated with leaf number( P 0. 05). Therefore,habitat had a significant influence on the dependency among size of flower and leaf size and number. The plant size would be decreased by the environmental stress at high altitude,and both flower size and leaf number are increased while the leaf size is declined to ensure the reproductive success of S. chamaejasme.

Heterogeneity of plant population response to soil moisture is the environmental basis of their pattern's formation and evolution. According to the pattern of soil water decreasing gradually from the wetland center to the edge,we set up five sampling plots to study the spatial distribution and spatial association of Kobresia tibetica and K. humilis under different soil moistures in north Qilian Mountain by using the point pattern analysis. The results showed that with the decrease of alpine wetland moisture content,the coverage,plant height and aboveground biomass of K. tibetica population were continuously increased,while the main biological features of K. humilis increased firstly then reduced. The distribution pattern of K. tibetica was clumped—regular—clumped and that of K. humilis gradually shifted from aggregation to regularity at small scale.Along with the decrease of soil moisture,the spatial association between K. tibetica and K. humilis population at small scale was positively correlated,then changed into no significant correlation and negative correlation finally. In the alpine wetland,the main biological features and spatial pattern of K. tibetica and K. humilis populations showed regular changes,which reflected the adaptability of the two species in response to habitat heterogeneity under different soil moistures.

Aims The relationship between stem and leaf growth is a strategy that plant canopy enhances photosynthetic efficiency and competitiveness through configuration adjustments; this relationship indicates the ratio between xylem and photosynthetic area in a heterogeneous environment.Our objective was to examine how Melica przewalskyi modulated leaf and stem traits in adaptation to changes in slope.Methods In the alpine grassland of Qilian Mountains,Gansu Province,China,80 plots were set up along four transects corresponding to contrasting aspects with 20 m distance between adjacent plots.A GPS was used to record latitude,longitude and altitude of each plot and ArcGIS software was used for constructing a digital elevation model (DEM) and extracting information on elevation,aspect,and slope.Community characteristics were investigated and 10 random individuals of M.przewalskyi were cut at the soil surface in each plot,and leaf mass,leaf area and stem mass were measured in laboratory.The 80 plots were grouped into 0°-10°,10°-20°,20°-30° slope gradients.Stem and leaf traits were log-transformed and then standardized major axis (SMA) estimation method was used to examine the allometric relationships of stem mass with leaf area or leaf mass.Important findings The stem mass,leaf mass and leaf area ofM.przewalskyi gradually decreased,but the leaf number increased,with slope gradient.An isometric relationship was found between stem mass and leaf area in plots within each slope gradient,whereas an allometric relationship was found between stem mass and leaf mass.Melica przewalskyi grown on steeper slopes tended to have smaller leaf area and greater leaf number at a given stem mass,and leaves with greater stem mass had greater leaf mass.A significant difference in the SMA slope among the three slope gradients of the plots suggested that the slope of the growth site constrained leaf area and leaf mass by stem mass,reflecting plant adaptation to heterogeneous environment.

Spatial pattern of aboveground biomass of grassland community reflects spatial hetero- geneity of resource allocation caused by terrain difference. Community survey method and gener- alized additive model( GAM) were used to study the response characteristics of community's aboveground biomass spatial pattern at hill and hillslope scales in natural grassland of the north- ern slope of Qilian Mountains. The results showed that at the hill scale,terrain factors had defi- nite effects on the aboveground biomass of community,with the sequence of elevation slope of aspect( SOA) ≈ slope of slope( SOS) ≈ slope. When reducing hill scale to hillslope scale by aspect,the aboveground biomass of grassland community would be most affected by SOA in east and west aspects,and by elevation and SOS in south and north aspects. On east slope,communi- ty's aboveground biomass firstly decreased then increased in SOA gradient,and vice versa in west slope. On south slope,it increased with elevation. On north slope,it firstly kept stable then decreased in SOS gradient. Our study suggested that the spatial pattern of aboveground biomass of grassland community was obviously scale-dependent at hill and hillslope scales.

Aims The growth relationship between twig and leaf is a strategy that plant canopy structure employs to space resources and enhance photosynthetic efficiency and competitiveness through configuration adjustments.Our objective was to examine how Stellara chamaejasme exploited twig and leaf configuration to explore the effects of slope change.Methods In the upper reaches of Shiyang river,Gansu Province,China,80 plots were set up at intervals of 20 m from the foot of a mountain along eight aspects.GPS was used to record latitude,longitude and altitude of each plot.Community traits were investigated and five S.chamaejasme were cut randomly on each plot for measurement of twig length,twig number,leaf area and leaf number.ArcGIS was used to set up digital elevation model(DEM) and abstract slope data of the study site.The 80 plots were divided into 0°-10°,10°-20° and 20°-30° slope gradients.Values for twig and leaf traits were logarithmically converted,and then the standardized major axis(SMA) estimation method was used to examine the allometric relationship between twig number,twig length,leaf number and leaf length.Important findings Twig length,twig number and leaf area of S.chamaejasme gradually decreased along the slope gradient.Significant allometric relationships between leaf number and twig length and between twig number and twig length were found to be consistent in all three slope gradients.Growing speed of twig length was greater than the speed of leaf number,and the growing speed of twig number was greater than the speed of twig length.However,there were significant differences in SMA slope in the three slope gradients,suggesting that slope constrains the leaf number and twig number that can be supported by a given twig length.

Taking the Xihu wetland in Dunhuang of Gansu Province for an example,we selected 4 type wetlands as the plots: Meadow bog,Reed swamp,Salt marsh and Saline land,and used the ways of field investigation and laboratory analysis and studied on the composition and species diversity of herb plants Xihu wetland in Dunhuang.The results show that: a total of 43 species belonging to 17 families are found in the 4 type wetlands,of which,Gramineae and Compositae species making up to 46.5%.Meadow bog has the largest number of species in the 4 type wetlands.It has 29 species,but Salt marsh only has 8 species.Meadow bog is an equal dominant community,so the Shannon-Wiener diversity index and Pielou evenness index are high and Simpson index is low.Reed swamp is a single structure community,reed(Phragmites australis)is the dominant species,Shannon-Wiener diversity index and Pielou evenness index are low,while Simpson index was high.Salt marsh and Saline land growth halophyte and xerophyte plants,these plants are dominant species in the community,Pielou evenness index is high and Simpson index is low.Meadow bog,Reed swamp,Salt marsh and Saline land plots distribute as step because of the different elevation,this distribution pattern can effect the flow direction and hydrops,so it is one of main reasons for the 4 type wetlands form significant difference on composition and species diversity.

In order to study the degradation process and community dynamics of alfalfa(Medicago sailva) grassland in the alpine areas of NW China,we surveyed alfalfa grassland communities in the Hanquangou valley in the upstream area of the Shiyang River from 2003~2009.The results showed that,the community coverage decreased,the community density increased,the aboveground biomass varied with the single peak curve during planting the alfalfa.With the weeds invading grassland communities,the number of species increased from 7~17 during 7 years,and the Compositae species took dominant proportion.Alfalfa showed natural thinning after 5 years,the grassland quality declined,so parts of the alfalfa grasslands lost utilization value,and Leymus secalinus become the dominant species.The degradation process of alfalfa grassland could be divided into three stages,i.e.,alfalfa grassland stage(2003~2004),transitional stage from alfalfa grassland to natural grassland(2005~2007),and secondary natural grassland stage dominated by grasses(2008~2009),they indicated early phase,medium phase and late phase,respectively.

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.

Soil erosion is a major threat to global economic and environmental sustainability. Based on the theory of Universal Soil Loss Equation and the related research resuhs on soil erosion at home and abroad, the paper analysed overlapping function with ArcGis. Furthermore, we analysed distribution characteristics and spatial difference of soil erosion sensitivity of Longnan. The results showed that the overall sensitivity of soil erosion was higher in Longnan. The high sensitivity and extreme sensitivity regions were 13107.51 km2, which amounting to t 46.94 percentage of total areas, and mainly distributed in Wudu and the Midwest of Wen county and Li county. And the areas of slight sensitivity and no sensitivity were small, which amounting to 17.85% and 3.14% of total areas, respectively. Finally, based on the comprehensive evaluation of spatial difference of soil erosion sensitivity, we advanced some countermeasures for the land-use planning to different sensitivity grades of Longnan.

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.

稳定的群落结构是退耕地生态系统恢复的主要标志之一。以祁连山东段旱泉沟流域退耕区为例,采用野外调查和室内分析相结合的方法,研究了建植6 a的人工草地群落稳定性,结果表明:人工草地在短期内形成了不同于撂荒地的植被格局,草地群落盖度、高度和地上生物量特性明显优于撂荒地和天然草地,部分人工草地物种丰富度和多样性高于撂荒地,功能群结构仍以多年生禾草占优势,无芒雀麦+紫花苜蓿混播草地多样性指数低,处于高产和稳定阶段;各草地根系主要分布在0～10 cm土层,不同草地类型0～20 cm土壤含水量变化最大,4种人工草地对土壤水分的影响表现为提高30～50 cm土层的水分含量,在水分涵蓄方面优于撂荒地。但与天然草地相比未形成密丛型禾草,群落稳定性差,草地群落的演替方向具有不确定性。

PotentiUa acaulis is considered as a green barrier to prevent grasslands from further degradation, it has important significance on the direction and improvement of vegetation succession on grasslands, the community deg-radation mechanism of the soil seed bank can be used to direct grasslands ecology renewing. With field vegetation surveying and laboratory test ,the paper chose and identified the seeds from 270 soil samples by adopting physical method, seedling germination and TTC, and then analyzed the soil seed bank of arid grassland's Potentilla acaulis community in upstream of Shiyang River. The results showed as follows:a total of 19 plants belonging to 14 families were found in the soil seed bank ,3 species were annual herb and 16 species were perennial herb. There was a sig-nificant decreasing tendency of the density of grasses and an increasing tendency of non-edible grass with the in-crease of Potentilla acaulis's coverage. The number of plant species and the seed density in the shallow soil layer were larger than that in the deep one. The vertical distribution of seed bank's density was presented as the following precedence order: 0 -5 cm's > 10 - 15 cm's > 5 - 10 cm 's, the seeds of different functional groups also showed the same distribution pattern. The soil seed bank of Potentilla acaulis is very small, which is accounted for only 2.93% of the total seed bank, its regeneration pathway is inclined to vegetative propagation. The changes of species diversity index and evenness index tend to be uniform. However, the dominance index of the soil seed bank is opposite to the evenness index and diversity index in vegetation gradients. The average similarity index of seed bank and standing vegetation is 0.392. The similarity of species composition of the soil seed bank and vegetation species composition of the surface belongs to a moderate dissimilar level. There is no finding at the seeds of dominant population of pri-mary zonal vegetation, which reflects the irreversibility of degradation mechanism of grassland community. The change of plant species and functional group composition in the study area basically reflects a series of degradation trend of Potentilla acaulis Community, such as community structural simplification and environmental matrix stabili-ty weakening.

The two-way indicator species analysis and the detrended correspondence analysis are adopted to classify and rank the quadrats of the secondary plant in the Hanquangou valley in Gansu province.The flora can be divided into different community types,and demonstrate the distributed pattern of the vegetation community in this region.Based on this result,the species richness index,the Simpson dominance index,the Shannon-Wiener diversity index and the Pielou evenness index are used to study the species diversity of different vegetation community types.The results shows that there are 7 community types,which represents the different restoration stages.The primary limiting factors are water and heat in specific region,Chashugou valley.From restora-tion stage Ⅰt oⅦ,as for the Simpson dominance index,tree layer,shrub layer and herb layer are approximately equal,the Shan-non-Wiener diversity index manifests as tree layer shrub layer herb layer,the Pielou evenness index manifests as tree layer herb layer shrub layer,and the species richness increase gradually.The species composition and the spatial structure of the community become complication gradually,and tend to be stable.

Based on the survey of community plots,The two-way indicator species analysis and the Detrended correspondence analysis were adopted to classify and rank the quadrats of the secondary forest in the eastern Qilian mountains in gansu province. To study the spatial distribution pattern of plant populations from the species structure and the ecological relationship of plant species,plant communities and environment in this region,and so as to obtained the forest secondary succession in different stages. The results show that there were 7 community types,the primary limiting factors were water and heat. The result of DCA ordination showed that dieffrent plant communities and their distributing area varied along the environmental gradients in the ordination grpah.The first axis of DCA denoted humidity gradient and the second axis of DCA denoted change of altiutde and temperature gradient. The results indicate that the succession law of the secondary forest was from aspen,however,with the passage of time,serclimax finally became the Qinghai Spruce.

Using 6 years of continuous location observation,we studied the degradation features of Medicago saliva grassland in the Hanquangou valley of eastern Qilian mountains.The results showed that in growing the Medicago sailva,the community coverage decreased,the community density increased and the community height showed a fluctuation change.Aboveground biomass varied with the single peak curve and the maximum value appeared in 2005.The species in the grasslands increased from 7 to 16 during 6 years.The inter-annual species replacement rate varied from 2.5 to 5.5.Shannon-Wiener diversity index showed an ascendant trend, Pielou evenness index showed a fluctuation change and Simpson index showed a declining trend.Medicago sailva species showed natural thinning in 2007,and the hay yield decreased to 129.8 g/m~2.The vacant land of grassland community increased and the quality declined,so part of the Medicago saliva grasslands lost utilization value.The grassland community went through three successive stages from 2003 to 2008,i.e. the advantage stage of Medicago sailva species,the perennial weeds stage and the perennial grasses stage. The grasslands exhibited a serious degradation and loss of function.The succession pattern of community structure and function concerning artificial grasslands had changed into abandoned arable lands succession pattern.