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1.
选择古尔班通古特沙漠的北部(一号点)、中部(二号点)、南部(三号点)3个不同样点的裸沙和藻结皮、地衣结皮与苔藓结皮3种生物结皮类型,对比研究了草本植物多样性的差异性及其主要环境影响因素。结果表明:(1)不同生物结皮类型的土壤理化性质有明显差异,土壤有机质、全氮、全磷、全钾含量以及黏粒、粉粒和细沙的含量随生物结皮演替显著上升,而中沙和粗沙的含量呈显著下降趋势,在沙漠不同区域呈现明显的空间异质性,二号样点中裸沙和藻结皮的养分含量和pH明显低于一号点和三号点。(2)草本植物的物种丰富度和Shannon-Wiener指数随生物结皮发育呈明显上升趋势,草本植物的物种组成、群落结构在不同类型生物结皮和沙漠不同区域均具有显著差异。(3)在土壤理化特征中,有机质、速效P和全K含量,以及pH和粉粒含量是影响草本植物分布的关键因子。(4)不同类型生物结皮之间的微地形和种类组成差异、种子生物学特性以及生物结皮在不同尺度下的土壤环境异质性共同影响草本植物在生物结皮中的物种组成和丰度,最终导致草本植物群落结构在生物结皮中的演替变化。  相似文献   

2.
在北屯绿洲选择了3组不同年限的次生盐渍化弃耕农田,分别计算了样地内每种植物的重要值,采用Shannon-Wiener指数、Pielou指数、Simpson指数测定了生物多样性.结果表明:3组群落组成存在显著差异,优势种更替明显.3组群落构成依次为,一年生草本、一年生草本 多年生小半灌木、多年生草本 灌木.物种多样性表现为2年群落>5年群落>13年群落;群落均匀度表现为2年群落>5年群落,而5年与13年群落相当,但是生态优势度却表现出与物种多样性相反的趋势,即2年群落<5年群落<13年群落.  相似文献   

3.
新疆天山天池风景名胜区旅游开发目前主要集中在以天池为中心的湖滨区,景区已出现旅游吸引力不足、旅游活动内容单调、旅游环境容量有限等一系列问题,着手进行后续旅游开发势在必行。实际上,就资源、客源、交通等条件而言,天池景区的后续开发均有保障,并预期有良好的社会、经济、环境效益。通过实际调查,建议选择开发吉岩坚沟百花园景区,在三个岔沟的冰川和冰湖区建立冰川公园。同时必须关注天池湖面缩小、旅游与牧业、相邻行政区协调、自然保护区区域划分等相关问题,尤其是做好防止天池退缩的环境保护工程。  相似文献   

4.
This study aimed to investigate the interaction between regions with different climatic conditions(arid vs. semi-arid) and management(protected vs. unprotected) on the turnover and nestedness of vegetation in relation to physical, chemical and biological properties of soils in the Ilam Province of Iran. In each of the two regions, we sampled 8 sites(4 managed and 4 unmanaged sites) within each of which we established 4 circular plots(1000 m~2) that were used to investigate woody species, while two micro-plots(1 m×1 m) were established in each 1000-m~2 plot to analyze herbaceous species. In each sample unit, we also extracted three soil samples(0–20 cm depth) for measuring soil properties. The results indicated that the interaction between region and conservational management significantly affected the percent of canopy cover of Persian oak(Quercus brantii Linddl), soil respiration, substrate-induced respiration, as well as beta and gamma diversities and turnover of plant species. The percent of oak canopy cover was positively correlated with soil silt, electrical conductivity, available potassium, and alpha diversity, whereas it was negatively correlated with plant turnover. In addition, plant turnover was positively related to available phosphorus, while nestedness of species was positively related to organic carbon and total nitrogen. According to these results, we concluded that physical, chemical, and biological characteristics of limited ecological niche generally influenced plant diversity. Also, this study demonstrated the major contribution of the beta diversity on gamma diversity, especially in semi-arid region, because of the higher heterogeneity of vegetation in this area.  相似文献   

5.
Ecological patterns and processes in dune ecosystems have been a research focus in recent years, however the information on how dune stabilization influences the spatial scale dependence of plant diversity is still lacking. In this study, we measured the plant species richness, soil properties and altitude across four spatial scales(1, 10, 100 and 1,000 m2) at three different dune stabilization stages(mobile dune, semi-fixed dune and fixed dune) in Horqin Sandy Land, Northern China. We also examined the relationships between plant species richness, community composition and environmental factors along the gradient of dune stabilization. Our results showed that plant species richness increased with the increase of spatial scales in each dune stabilization stage, as well as with the increase of dune stabilization degrees. Canonical correspondence analysis(CCA) showed that plant distribu- tions in the processes of dune stabilization were determined by the combined environmental gradient in relation to soil organic carbon(SOC), total nitrogen(TN), carbon/nitrogen(C/N), pH, electrical conductivity(EC), soil water content(SWC), fine sand(FS), very fine sand(VFS), silt and clay(SC), and altitude. Plant species richness was significantly and positively correlated to SOC and TN in mobile dune, and significantly and positively correlated to SOC, TN, C/N, VFS and SC in semi-fixed dune. However, no significant correlation between plant species richness and environmental factors was observed in fixed dune. In addition, plant species richness in different dune stabili- zation stages was also determined by the combined gradient of soil properties and altitude. These results suggest that plant species richness has obvious scale dependence along the gradient of dune stabilization. Soil resources depending on dune habitats and environmental gradients caused by dune stabilization are important factors to de- termine the scale dependence of species diversity in sand dune ecosystems.  相似文献   

6.
Altitude is a useful indicator to examine patterns of forest structure and species diversity in relation to environmental factors.In this study,the altitude patterns of forest stand structure and species diversity were analyzed across 20 plots in the Tianchi Nature Reserve,Northwest China.The results showed that mean stem height(Hm),maximum stem height(Hmax) and mean stem diameter at breast height(Dm) of Picea schrenkiana trees all decreased significantly with increasing altitude.Potential tree height(H*) decreased while stem taper increased significantly as altitude increased,suggesting remarkable altitudinal changes in biomass allocation between the diameter and height growth of Picea schrenkiana.Understory herbaceous richness increased significantly with increasing altitude,or with decreasing total basal area(TBA),Hm and stand volume(Volume).High light availability for understory herbs might account for the higher species richness at high altitude.Sorensen Index decreased significantly with the increase in altitude intervals,while the Cody Index demonstrated a converse pattern,suggesting greater differences in species composition with larger distances.  相似文献   

7.
The influence of edaphic factors on plant distribution is essential to community ecology and important for vegetation restoration and management in arid ecosystems. In this study, desert plant distribution and diversity as well as soil water, salinity, and nutrients were measured in the Ebinur Lake Wetland Nature Reserve (ELWNR) in arid Northwest China. We determined relationships between plant distribution and soil factors along a transect with increasing distance from the river and created optimal models using soil factors to explain variations in plant diversity. In general, soil factors decreased with increasing distance from the river. Soil volumetric water content (SVWC), electrical conductivity (EC), pH, nitrogen (N), phosphorus (P), and sulfur (S) were closely related to plant distribution. According to canonical correspondence analysis, plants along the transect were divided into three groups: saline–alkaline tolerant, drought tolerant, and high P-demanding. SVWC, pH, soil organic carbon (C), N, P, and S account for 93.8% of the variations in plant diversity in the ELWNR. Compared with other soil factors, S explained the largest percentage of variations in diversity when single soil variables were considered in generalized additive models (R2?=?38.9%). Our results suggest increases in soil pH, P, N, and S would improve plant diversity significantly. We found differences among species groups in preference for habitat, and N and S content had a significant positive effect of on plant diversity, providing a scientific reference for plant restoration and saline soil remediation in desert ecosystems.  相似文献   

8.
Frequent periods of drought conditions are known to limit plant performance,primary production,and ecosystem stability in arid and semi-arid desert steppe environments.Plants often avoid competition by shifting their water use seasonally,which affects the water-use patterns of dominant species as well as the composition and structure of plant communities.However,the water-use strategies of dominant herbaceous species,which grow under natural field conditions in the desert steppe region of Ningxia Hui Autonomous Region,China,are poorly known.Here,we explored the possible sources of water uptake and water-use efficiency(WUE)of three dominant herbaceous plant species(Stipa breviflora,Agropyron mongolicum,and Glycyrrhiza uralensis)in a native desert steppe in the semi-arid area of Ningxia through an analysis of multiple parameters,including(1)the stable isotopic oxygen and hydrogen(δ18O andδ2H)compositions of precipitation,soil water,and stem water,(2)the carbon isotope(13C)composition of leaves,and(3)the soil water contents,based on field sampling across varying water conditions from June to September,2017.Frequent small precipitation events replenished shallow soil water,whereas large events only percolated down to the deep soil layers.Changes in soil water availability affected the water-use patterns of plants.Generally,during light precipitation periods,the deep root system of G.uralensis accessed deeper(>80 cm)soil water,whereas S.breviflora and A.mongolicum,which only have shallow roots,primarily absorbed water from the shallow and middle soil layers.As precipitation increased,all three plant species primarily obtained water from the shallow soil layers.Variation in soil water uptake between the dry and wet seasons enabled plants to make better use of existing satoil water.In addition,theδ13C values of G.uralensis and S.breviflora were higher than those of A.mongolicum.Theδ13C values of the three plant species were significantly negatively correlated with soil water content.Therefore,G.uralensis and S.breviflora maintained a higher WUE through their conservative and water-saving strategies across the entire growing season.In contrast,A.mongolicum,with a relatively low WUE in the wet season but a high WUE in the dry season,exhibited a more flexible water-use strategy.The different water-use strategies of these dominant plant species demonstrated the mechanisms by which plant communities can respond to drought.  相似文献   

9.
Great gerbil(Rhombomys opimus) colonies, with bare soil and herbaceous plants, are conspicuous to the background environment throughout their range area. In order to quantify the engineer role of great gerbils, we investigated the plant communities of 20 active colonies in the Junggar Basin, Xinjiang, China. In areas without disturbance, desert plant communities were dominated by the shrubs with low level species richness. In burrow areas and surrounding intermediate areas, which were disturbed by great gerbils, the shrubs were suppressed with the decrease of vegetation cover and aboveground biomass. As a result, "niche gaps" were created in disturbed areas and worked as a refuge for herbaceous annuals and perennials. So the existence of great gerbils increased the overall species richness of the desert. Furthermore, herbaceous annuals and perennials are the major food source for great gerbils in spring, indicating that great gerbils have a mutually beneficial relationship with herbaceous plants.  相似文献   

10.
Knowledge about plant diversity along disturbance gradients is essential for conservation and management of fragmented coastal habitats.This study examined the effects of human disturbance intensity in coastal habitats of Kuwait on diversity,composition,identity and assemblage of vascular plant species.Plant survey data from 113 plots (5m×5m each) were randomly selected in 51 sites at coastal fragmented habitats at three levels of disturbance intensities (high,moderate and low) and were statistically analyzed.The results revealed that about 76% of the recorded species are considered threatened species in Kuwait,most of which are being lost in high disturbed habitats.Disturbance led to the dominance of Zygophyllum qatarense,Cornulaca aucheri and Salsola imbricata,which are species of disturbance indicators.Richness,total plant cover and species diversity were higher in moderate and low disturbed habitats than in high disturbed habitats.Beta diversity between high and low disturbed habitats was higher than either between high and moderate,or between moderate and low disturbed habitats.Cluster analyses showed statistically significant differences in composition of plant assemblages,which indicate high beta diversity between the habitat types.Intensive urbanization and industrialization are among the most serious threats that contribute to declines in biological diversity and rapid fragmentation of coastal habitats in Kuwait.Establishing protective enclosures in the disturbed habitats,planting endangered and vulnerable species,and establishing a natural reserve at Nuwaiseeb are recommended conservation actions to avoid loss of the fragmented coastal habitats and to facilitate restoration of native plants.  相似文献   

11.
草本层是古尔班通古特沙漠植被的重要组成部分,在维持沙漠稳定、养分循环等方面具有重要意义。水分通常以积雪和降雨形式输入到土壤,输入方式及数量变化对荒漠植物的存活和生长有重要影响。本文以古尔班通古特沙漠南缘草本层为研究对象,利用人工增减积雪的方法,共设置4个积雪处理(0,50%,100%,200%积雪,其中100%积雪为对照),于2009—2016年春季调查草本植物的数量特征和物种丰富度,分析草本植物数量特征对水分变化的响应;同时结合气象数据,分析不同年份一年生荒漠草本植物数量特征与主要气象因子的关系。结果表明:表层土壤含水量与积雪厚度成正比,相应的草本植物的幼苗密度与积雪水当量、表层土壤含水量成正比关系;2009—2016年,年内积雪量的变化对物种丰富度没有显著影响,各积雪处理间物种丰富度差异不显著;2009—2016年自然处理下年际间物种丰富度差异显著,2015年物种丰富度显著小于其余年份。结合气象数据分析发现,物种丰富度年际变化主要受幼苗建成期的降雨调控,并且干旱年份过后的湿润年份物种丰富度不受前一年降水的影响,说明荒漠草本植物层片具有较强的自我调节能力;自然处理下,不同年份草本植物旺盛期的存活数量与大气干旱程度(空气饱和差)呈显著负相关关系(R2值为0.611,P<0.05),与生长季的降雨量呈正相关关系(R2值为0.162, P>0.05),说明大气干旱程度更能表征荒漠草本植物生长峰值期的存活情况。  相似文献   

12.
以内蒙古荒漠区短脚锦鸡儿灌木为研究对象,采用野外调查法分析灌丛对植物群落的影响,采用传统培养法,结合分子鉴定法分析灌丛对土壤微生物群落的影响。结果表明:(1)灌丛内植物群落多度和总生物量显著大于灌丛外,但是物种丰度和Shannon-Wiener指数灌丛内外无显著差异;(2)随土壤深度的增加,表层土与深层土的土壤可培养细菌丰度和真菌多度差异不显著,其余土壤微生物群落多样性特征均表现为:表层土显著大于深层土;(3)灌丛对土壤微生物群落具有正效应,且表层土正效应最大;(4)灌丛对植物群落的促进作用大于对土壤微生物群落的作用。  相似文献   

13.
Grazing exclusion is one of the most efficient approaches to restore degraded grassland but may negatively affects the recovery of species diversity. Changes in plant species diversity should be a consequence of the ecological assembly process. Local community assembly is influenced by environmental filtering, biotic interactions, and dispersal. However, how these factors potentially contribute to changes to species diversity is poorly understood, especially in harsh environments. In this study, two management sites within a Stipa breviflora desert steppe community(typical natural steppe) were selected in northern China. In one of the two management sites, grazing has been excluded since 2010 and in the other with open grazing by sheep. In August 2016, three plots were established and 100 sampling units were created within each plot in a 5 m×5 m area at the two management sites. To assess the effects of grazing exclusion on S. breviflora steppe, we analyzed the vegetation biomass, species diversity,soil organic carbon, and soil particle size distribution using paired T-tests. In addition, variation partitioning was applied to determine the relative importance of environmental filtering and dispersal limitation. Null mode analysis was used to quantify the influence of biotic interactions in conjunction with Eco Sim niche overlap and co-occurrence values. Our results demonstrated that(1) species diversity significantly decreased and the main improvements in soil quality occurred in the topsoil 0–10 cm after the grazing exclusion;(2) environmental filtering was important for community assembly between grazed and fenced grassland and this appears particularly true for soil particle size distribution, which may be well correlated with soil hydrological processes; and(3) however, competitive exclusion may play a significant role within the exclusion. The multiple pathways of assembly may collectively determine negative effects on the restoration of species diversity. Therefore, designers should be aware of the risk of reducing grazing exclusion-induced species diversity and account for manipulating processes. This in turn will reduce dominant species and promote environmental heterogeneity to maximize species diversity in semi-arid regions.  相似文献   

14.
利用5种β多样性指数,研究了五台山旅游活动对草甸植物群落β多样性的影响。结果表明:①草甸群落的β多样性主要受到旅游干扰和种间竞争的共同影响,在不同群落类型之间β多样性的变化幅度较大,而在同一群落类型之间β多样性的变化幅度较小;②随着距离差的增加,5种β多样性指数的变化趋势均说明距离差越大,群落之间的共有种越少,相异程度...  相似文献   

15.
Fractal geometry is an important method in soil science,and many studies have used fractal theory to examine soil properties and the relationships with other eco-environmental factors.However,there have been few studies examining soil particle volume fractal dimension in alpine grasslands.To study the volume fractal dimension of soil particles(D) and its relationships with soil salt,soil nutrient and plant species diversity,we conducted an experiment on an alpine grassland under different disturbance degrees:non-disturbance(N 0),light disturbance(L),moderate disturbance(M) and heavy disturbance(H).The results showed that(1) Ds varied from 2.573 to 2.635 among the different disturbance degrees and increased with increasing degrees of disturbance.(2) Shannon-Wiener diversity index,Pielou's evenness index and Margalef richness index reached their highest values at the M degree,indicating that moderate disturbance is beneficial to the increase of plant species diversity.(3) In the L and M degrees,there was a significant positive correlation between D and clay content and a significant negative correlation between D and soil organic matter(SOM).In the H degree,D was significantly and positively correlated with total salt(TS).The results suggested that to a certain extent,D can be used to characterize the uniformity of soil texture in addition to soil fertility characteristics.(4) For the L degree,there was a significant negative correlation between D and the Shannon-Wiener diversity index;while for the M degree,there was a significant negative correlation between D and Pielou's evenness index.  相似文献   

16.
荒漠化防治的另一途径——C4植物   总被引:3,自引:0,他引:3  
张经炜 《干旱区研究》2006,23(3):384-387
荒漠化和沙尘暴不仅影响西北地区,同时也影响到相邻地区的国民经济的发展和人民生活的改善.虽然,我国政府历年来都十分重视西北地区的生态条件的改善和环境的建设,但我国沙尘暴的频次和强度在未来几年仍有增加之势.C4(碳四)植物具有高光饱和点、高光合速率和高光合生产效率的生理特性.比C3(碳三)植物耗水少,而光合效率高.对土壤的适应性广,具有较强的竞争力.它应是优先考虑的干旱区水土保持植物.从美国选育的C4纤维禾草可以看出,多年生的C4纤维禾草具有:①光合效率高,而水耗低;②多年生可节省每年播种所需的种、肥和耕作费用,节省生产成本;③强大的根系可使植物体内的氮元素储存起来,提高了土壤养分的利用率等特点.它是干旱区中一种既节水,又是水土保持最有成效的植物资源,对缓解西北地区的荒漠化问题将会发挥巨大的作用.我国温带地区的草本植物资源丰富,其中有不少的C4植物.建议开展C4草本植物和木本植物的选育、引种和推广研究,以在半荒漠地区营造一个环境良好、人与自然和谐的家园.  相似文献   

17.
选择甘家湖梭梭林自然保护区湿地边缘地带作为研究区域,研究荒漠鼠类活动对土壤的扰动效应及对梭梭生长的影响。在甘家湖湿地边缘进行隔月分季定期采样,对样品进行测试和分析研究。结果表明:(1)荒漠鼠类活动对土壤容重、含水量、总孔隙度以及pH值均有明显影响;(2)鼠类活动对土壤酶活性有影响,鼠害区脲酶、蛋白酶、过氧化氢酶和蔗糖酶的活性变化,在整个观测期均较对照区低;(3)鼠类活动对梭梭生长的影响显著,鼠害严重区植株高度、冠幅偏低,植株死亡数目相对较高。  相似文献   

18.
Disturbance by rodents alters the morphologies and nutrients of plants as well as the physical-chemical properties of the soils. Changes in plants are considered to be mechanisms of defense against the disturbance by rodents. Rodents gnaw on the assimilating branches of Haloxylon ammodendron(CA Mey.) Bunge and burrow under the bushes in the desert ecosystems of Xinjiang, China. However, eco-physiological responses of different age groups of H. ammodendron to the disturbance by rodents are not well understood. In this study, soil physical-chemical properties under the shrubs and the above-ground morphological, physiological and biochemical features of assimilating branches of H. ammodendron of different age groups(i.e., young, 30-100 cm; middle-aged, 100-200 cm; and mature, 200 cm) in burrowed and non-burrowed(control) areas were studied in 2018. We found that disturbance by rodents significantly increased the crown width and total branching rates of young and middle-aged H. ammodendron. Photosynthetic pigment contents of assimilating branches of H. ammodendron were significantly reduced under the disturbance by rodents. In term of plant nutrients, the main differences among different age groups of H. ammodendron under the disturbance by rodents occurred in the total soluble sugar and reducing sugar contents that decreased in young plants, increased in middle-aged plants, and did not affect in mature plants. Crude protein and phosphorus contents significantly increased, while crude fiber and calcium contents significantly decreased in young plants. Crude fat and calcium contents significantly decreased in middle-aged plants. Soil organic matter(SOM), total nitrogen(TN), available nitrogen(AN) and available potassium(AK) contents in the topsoil(0–20 cm), which are conducive to forming 'fertile islands' ', also increased under the disturbance by rodents. In particular, soil AN and AK were the major factors affecting the above-ground morphological characteristics of H. ammodendron in burrowed areas. Overall, the response and defense strategies of H. ammodendron to the disturbance by rodents differed among different age groups, and the effect of the disturbance by rodents on H. ammodendron gradually weakened with the increasing plant age.  相似文献   

19.
CHEN Juan 《干旱区科学》2022,14(9):1038-1054
Water is a limiting factor in the restoration and construction of desert steppe. Exploring plant water sources is necessary to understand soil-plant interactions and species coexistence; however, water sources of major plant communities within the desert steppe of Ningxia Hui Autonomous Region, China remain poorly understood. In this study, we analyzed the water uptake of plants in four typical communities: Agropyron mongolicum Keng.; Sophora alopecuroids Linn.; Stipa breviflora Griseb., and Achnatherum splendens (Trin.) Nevski communities. Stable isotopes δD and δ18O in the xylem of plant and soil water at different soil depths were analyzed. An IsoSource model was used to determine the soil depths from which plants obtained water. Results showed that A. mongolicum community obtained water predominantly from 0-20 and 40-80 cm depth, S. alopecuroids community from 0-20 cm depth, S. breviflora community from 0-40 cm depth, and A. splendens community from 0-20 and 80-140 cm depths. S. alopecuroides had a wider range of soil depths for water extraction, i.e., utilizing different water sources depending on habitat, and the plasticity of its water uptake pattern determined its role in different communities. Water source of plants relayed heavily on the distribution of their roots. Competition for soil water exists between different plant life forms in the sierozem habitat (A. mongolicum, S. alopecuroids, and S. breviflora communities), and in the sandy soil habitat (A. splendens community). The use of soil water by A. splendens community is more spatially differentiated, and shrubs and herbs can coexist stably. Under the pattern of extended drought period in the future, sierozem habitat may be more favorable for the formation of a dominant monoculture community type of perennial fibrous plants. In aeolian sandy soil habitat, A. splendens had a strong competitive advantage, and the growth of shallow-rooted plants was easily suppressed.  相似文献   

20.
Ecological restoration by Tamarix plants on semi-arid saline lands affects the accumulation, distribution patterns and related mechanisms of soil water content and salinity. In this study, spatio-temporal variations of soil water content and salinity around natural individual Tamarix ramosissima Ledeb. were invetigated in a semi-arid saline region of the upper Yellow River, Northwest China. Specifically, soil water content, electrical conductivity(EC_e), sodium adsorption ratio(SAR_e), and salt ions(including Na~+, K~+, Ca~(2+), Mg~(2+) and SO_4~(2–)) were measured at different soil depths and at different distances from the trunk of T. ramosissima in May, July, and September 2016. The soil water content at the 20–80 cm depth was significantly lower in July and September than in May, indicating that T. ramosissima plants absorb a large amount of water through the roots during the growing period, leading to the decreasing of soil water content in the deep soil layer. At the 0–20 cm depth, there was a salt island effect around individual T. ramosissima, and the EC_e differed significantly inside and outside the canopy of T. ramosissima in May and July. Salt bioaccumulation and stemflow were two major contributing factors to this difference. The SAR_e at the 0–20 cm depth was significantly different inside and outside the canopy of T. ramosissima in the three sampling months. The values of SAR_e at the 60–80 cm depth in May and July were significantly higher than those at the 0–60 cm depth and higher than that at the corresponding depth in September. The distribution of Na~+ in the soil was similar to that of the SAR_e, while the concentrations of K~+, Ca~(2+), and Mg~(2+) showed significant differences among the sampling months and soil depths. Both season and soil depth had highly significant effects on soil water content, EC_e and SAR_e, whereas distance from the trunk of T. ramosissima only significantly affected EC_e. Based on these results, we recommend co-planting of shallow-rooted salt-tolerant species near the Tamarix plants and avoiding planting herbaceous plants inside the canopy of T. ramosissima for afforestation in this semi-arid saline region. The results of this study may provide a reference for appropriate restoration in the semi-arid saline regions of the upper Yellow River.  相似文献   

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