Spatial heterogeneity for grain size distribution of eolian sand soil on longitudinal dunes in the southern Gurbantunggut Desert

The grain size composition, distribution characteristics and spatial variation of eolian sand soil on distinct positions across two longitudinal dunes and interdune areas were studied by means of conventional grain size analysis and geostatistical methods. In the study, 184 samples of eolian sand soil from the 0-30cm layer were systemically collected and measured from two longitudinal dunes and interdunes in the southern Gurbantunggut Desert. The results show that the dominant grain sizes are fine and very fine sands, and the differences of grain size compositions between the distinct geomorphologic positions are significant. The contents of clay and silt are highest on the interdune areas and lowest on the crests, and higher on the leeward slopes than on the windward slopes. The contents of very fine and fine sands are highest on the windward slopes and lowest on the crests. The contents of medium, coarse and very coarse sands are lowest on the interdune lands, and highest on the crests, and are identical on the two slopes. The coarser sizes (φ1) and mean sizes (Mz) for eolian sand soil all have a varying tendency from fine to coarse sizes with interdune area → leeward slope → windward slope → crest, and the sorting (σ) are poorly to well sorted. The results of geostatistical analysis reveal that φ1, Mz and σ values are moderately to strongly spatially autocorrelated. The values of the spatially correlated ranges are φ1<σ<Mz. The spatial variation for these grain size parameters is significant across the longitudinal dune landscape. From the crests towards the bottom of the slope, there is a varying gradient of zonal distribution, and the gradient values on the leeward slopes are larger than sites on the windward slopes.

Spatio-temporal variation of soil moisture in a fixed dune at the southern edge of the Gurbantunggut Desert in Xinjiang, China

Soil moisture is critical for vegetation growth in deserts.However,detailed data regarding the soil moisture distribution in space and time in the Gurbantunggut Desert of China have not yet been reported.In this study,we conducted a series of in situ observation experiments in a fixed sand dune at the southern edge of the Gurbantunggut Desert from February 2014 to October 2016,to explore the spatio-temporal variation of soil moisture content,investigate the impact of Haloxylon ammodendron(C.A.Mey.)Bungeon soil moisture content in its root zone,and examine the factors influencing the soil moisture spatial pattern.One-way analysis of variance,least significant difference tests and correlation analysis were used to analyze the data.The results revealed that the soil moisture content exhibited annual periodicity and the temporal variation of soil moisture content throughout a year could be divided into three periods,namely,a moisturegaining period,a moisture-losing period and a moisture-stable period.According to the temporal and spatial variability,the 0–400 cm soil profile could be divided into two layers:an active layer with moderate variability and a stable layer with weak variability.The temporal variability was larger than the spatial variability in the active layer,and the mean profile soil moisture content at different slope positions displayed the trend of decreasing with increasing relative height and mainly followed the order of interdune area>west and east slopes>slope top.The mean profile soil moisture content in the root zone of dead H.ammodendron individuals was significantly higher than that in the root zones of adult and young individuals,while the soil moisture content in the root zone of adult individuals was slightly higher than that in the root zone of young individuals with no significant difference.The spatial pattern of soil moisture was attributable to the combined effects of snowfall,vegetation and soil texture,whereas the effects of rainfall and evaporation were not significant.The findings may offer a foundation for the management of sandy soil moisture and vegetation restoration in arid areas.

Characteristics of soil seed banks at different geomorphic positions within the longitudinal sand dunes of the Gurbantunggut Desert, China

Understanding the characteristics of soil seed banks in sand dunes is crucial to stabilize the dune systems and maintain the plant populations in deserts. In this study, we conducted a survey investigation in the field and a seed germination experiment in the laboratory to explore the characteristics of soil seed banks at various geomorphic positions of longitudinal sand dunes in the Gurbantunggut Desert, China. Totally, 17 plant species belonging to 17 genera and 9 families were identified in soil seed banks, and 35 plant species belonging to 34 genera and 17 families were identified in aboveground vegetation. Plant species richness in soil seed banks decreased with increasing soil depth. The highest species richness was presented in the upper slope of the windward slope and the lowest species richness was presented in the base of the windward slope. There was no significant difference in seed density of soil seed banks among the examined seven geomorphic positions. The highest seed density occurred in the lower slope of the leeward slope while the lowest occurred in the crest. Moreover, seed density decreased with increasing soil depth, being the highest in the upper soil layer(0–2 cm). For both soil seed banks and aboveground vegetation, there was no significant difference in Simpson's diversity index among the seven geomorphic positions; however, Shannon-Wiener diversity index and Pielou's evenness index showed significant differences among the seven geomorphic positions. Those results showed that although there was no significant difference in seed density of soil seed banks among the seven geomorphic positions, the geomorphic positions significantly affected the species richness, diversity and distribution of soil seed banks. Therefore, understanding the characteristics of soil seed banks at different geomorphic positions of sand dunes is essential to vegetation restoration or reestablishment. Furthermore, the Jaccard's similarity coefficients of plant species between soil seed banks and aboveground vegetation at the seven geomorphic positions were low, suggesting that vegetation restoration or reestablishment processes should be promoted through adding seeds to surface layers.

Competition,spatial pattern,and regeneration of Haloxylon ammodendron and Haloxylon persicum communities in the Gurbantunggut Desert,Northwest China

Competition,spatial pattern,and regeneration are important factors affecting community composition,structure,and dynamics.In this study,we surveyed 300 quadrats from three dunes(i.e.,fixed dunes,semifixed dunes,and mobile dunes)in the Gurbantunggut Desert,Northwest China,from late May to early June in 2021.The intraspecific and interspecific competition,spatial pattern,and regeneration of Haloxylon ammodendron and Haloxylon persicum were studied using the Hegyi competition index and point pattern analysis methods.The results showed that the optimal competition distance of the objective tree in the H.ammodendron and H.persicum communities was 6 m.The intraspecific and interspecific competition of H.ammodendron was the greatest in fixed dunes,while the competition intensity of H.persicum in semifixed dunes and mobile dunes was greater than that in fixed dunes.The order of competition intensity of the two populations was seedlings>saplings>adults,and the competition intensity gradually decreased with the increase in plant diameter.The spatial distribution pattern of the three life stages of H.ammodendron and H.persicum was random,and there were no correlations between seedlings and saplings,adults and saplings,and seedlings and adults.The density of regenerated seedlings and saplings of H.ammodendron in the three dunes followed the order of fixed dunes>semifixed dunes>mobile dunes,and that of H.persicum in the three dunes followed the order of mobile dunes>semifixed dunes>fixed dunes.Therefore,when artificially planting H.ammodendron and H.persicum for sand control,the planting interval should be 6 m,and seedlings should be planted next to adults to minimize the competition between plants,which can promote the renewal of H.ammodendron and H.persicum and the stabilization of the ecosystem.

Study on the Land Reclamation of Oilfield of Gurbantunggut Desert in Junggar Basin

The exploration and development of oilfield results in damages to land resources. Along with the further development of petroleum in the Gurbantunggut Desert, the fragile ecological environment and land resource was suffering much more damage. Vegetation degradation and desertification become more prominent. In response to the damage to the fragile ecological environment and oilfield in the Gurbantunggut Desert, limit condition method was used to evaluate the suitability of land reclamation suitability. Results suggested that the main restraining factors for land reclamation were soil condition and water resources. Based on the effect and shortage of oilfield in the Gurbantunggut Desert Oilfield, the reclamation of oilfield in the Gurbantunggut desert was discussed.

Distribution of ephemeral plants and their significance in dune stabilization in Gurbantunggut Desert

Based on systematically monitoring plants on dune ridges in the southern part of the Gurbantunggut Desert in 2002, this paper, from the angle of dune stabilization by vegetation, describes the temporal and spatial distribution patterns of ephemeral plants on isolated sand dunes, analyses the natural invasion processes of ephemeral plants on human-disturbed sand surface and expounds the importance of ephemeral plants in stabilizing sand dune surface. A total of 45 plant species were identified in the study area, 29 of which are ephemeral plants. Ephemeral plants sprouted in early April and completed their life-circle within about two months. Just as aeolian sand activities came to the strongest stage from April to June in desert regions of northern Xinjiang, the total coverage of trees, shrubs and herbs of long vegetational period on most dune ridges was less than 10%, while the mean coverage of ephemeral plants reached 13.9% in April, 40.2% in May and 14.1% in June. Therefore ephemeral plants acted as the major contributor to dune surface stabilization in the Gurbantunggut Desert. Investigations of vegetation restoration on engineering-disturbed dune surface show that ephemeral plants first recolonized the disturbed dune surface.

Dynamics of arbuscular mycorrhizal fungi associated with desert ephemeral plants in Gurbantunggut Desert

Previous studies documented that most desert plants can be colonized by arbuscular mycorrhizal (AM) fungi,however,little is known about how the dynamics of AM fungi are related to ephemerals in desert ecosystems.The dynamics of AM fungi with desert ephemerals were examined to determine the effects of host plant life stages on the development of AM fungi.Mean colonization of ephemeral annual plants was 45% lower than that of ephemeral perennial plants.The colonizations were much higher in the early part of the growing season than in later parts,peaking at flowering times.The phenology of AM fungi in root systems varied among different ephemerals.The density of AM fungal spores increased with the development of ephemeral annual plants,reached its maximum at flowering times,and then plateaued about 20 days after the aboveground senescence.A significant positive correlation was found between AM fungi spore density and biomass of ephemeral annual plants.The life cycles of AM fungi associated with desert ephemerals were very short,being about 60-70 days.Soil temperature and water content had no direct influence on the development of AM fungal spores.We concluded that the development of AM fungi was in response to desert ephemeral phenology and life history strategy.

古尔班通古特沙漠生物土壤结皮下土壤有机碳垂直分布特征及影响因素

为了探究沙漠不同生物土壤结皮类型覆盖下土壤有机碳(SOC)垂直分布特征及与土壤理化因素的关系,解析影响因素,以古尔班通古特沙漠腹地藻类、藓类生物土壤结皮和裸沙三种不同地被覆盖类型为研究对象,通过野外采集不同类型结皮样品及其下层0—2 cm、2—5 cm、5—10 cm、10—20 cm、20—30 cm、30—50 cm、50—70 cm以及70—100 cm土层土壤(裸沙对照),测定不同土层的SOC含量及土壤理化指标,开展相关研究。结果表明:(1)不同地被类型下0—100 cm SOC含量随着土壤深度增加呈减小的趋势,在10—30 cm土层存在SOC含量升高的现象,藓类、藻类和裸沙三种地被类型0—100 cm土层SOC含量范围分别在:1.61—2.70、1.41—2.56、1.21—1.92 g/kg;(2)不同地被类型下同一土层SOC含量在0—5 cm土层存在显著差异,5—100 cm土层SOC整体无显著差异,同层SOC含量均表现为:藓类>藻类>裸沙对照;(3)Pearson法分析结果表明不同地被覆盖下SOC含量与养分(全氮、全磷)呈现正相关关系,与pH和电导率(EC)呈现负相关关系。通过结构方程模型结果表明,土壤养分和粒径(砂粒占比)是影响垂直分布的主要因子,其中粒径是裸沙和藻类的最主要影响因子,藓类最重要的影响因子是养分(全磷)。生物土壤结皮的发育会逐步提高土壤碳的积累,改变SOC的垂直分布特征,对SOC的影响主要集中在5 cm以上土层,土壤理化特征对垂直分布特征具有调控作用。

古尔班通古特沙漠西南缘多枝柽柳生理特性对沙堆不同堆积阶段的响应

多枝柽柳作为干旱荒漠区重要的防风固沙灌木,其长期与风沙作用过程中形成了柽柳灌丛沙堆,在维持区域生态环境稳定及遏制沙漠蔓延方面发挥着重要作用。以古尔班通古特沙漠西南缘地区不同发育阶段沙堆上生长的多枝柽柳(Tamarix ramosissima)为研究对象,以空间序列代替时间序列的方法模拟沙堆堆积发育过程,揭示多枝柽柳生理特征对沙堆不同堆积发育阶段的响应及适应机制。结果表明:(1)在沙堆堆积发育过程中,多枝柽柳叶片相对含水量(RWC)及自由水/束缚水(Vs/Va)均呈先上升后下降的变化,其中,在增长阶段沙堆上最高,衰退阶段沙堆上最低,水分饱和亏(WSD)则呈相反趋势;组织含水量(TWC)呈逐渐上升的变化,清晨水势(Ψ_(PD))及正午水势(Ψ_(MD))呈逐渐降低的变化。(2)在沙堆堆积发育过程中,多枝柽柳的光合有效辐射(PAR)、叶片温度(TL)、光合电子传递速率(ETR)以及调节性能量耗散[Y_((NPQ))]日变化均呈先上升后下降的变化,衰退阶段沙堆上多枝柽柳各参数的日均值最大;各发育阶段沙堆上多枝柽柳的非调节性能量耗散[Y_((NO))]日变化均呈先下降后上升的变化,实际光化学效率[Y_((II))]日变化均呈“N”型,且Y_((II))日均值大小依次为增长阶段沙堆(0.489)>稳定阶段沙堆(0.463)>雏形阶段沙堆(0.455)>衰退阶段沙堆(0.439)。(3)气温(TEMP)和PAR与叶片Y_((II))均呈显著负相关,与ETR均呈显著正相关;Y_((II))与ETR、Y_((NO))与Y_((NPQ))均呈现显著负相关;PAR、TEMP是影响不同堆积阶段沙堆上多枝柽柳生理特性的主要环境因子。综合分析表明,在沙堆堆积发育过程中,多枝柽柳可通过调节光合作用和水分利用之间的协同关系来响应微环境的变化,从而减少其脱水风险以实现最大程度资源利用。

温带荒漠灌丛和藓类结皮对土壤养分的贡献

灌丛与生物土壤结皮镶嵌分布是温带荒漠常见的地表景观之一,二者的发育均显著影响了地表土壤养分的空间分布特征及循环过程。然而,灌丛和生物土壤结皮对荒漠土壤表层养分的影响存在怎样的差异,二者对养分变化的贡献度如何尚不清楚。因此,选择中国北方典型温带荒漠古尔班通古特沙漠为研究区,以荒漠中的优势灌丛膜果麻黄(Ephedra przewalskii)灌丛和生物土壤结皮发育高级阶段的藓类结皮的结皮层及结皮下层土壤为研究对象,采集不同微生境(裸露地、灌丛下)的裸沙与藓类结皮的土壤样品。为探究不同微生境下不同土层碳、氮、磷和钾养分变化特征,测定了不同土层土壤有机碳(SOC)、全氮(TN)、全磷(TP)、全钾(TK)、速效氮(AN)、速效磷(AP)和速效钾(AK)含量。结果表明:(1)相较于裸露地,灌丛显著提高了藓类结皮不同土层有机碳、全氮和全钾的含量和裸沙全磷的含量,降低了灌丛下藓类结皮土壤全磷的含量。(2)对于速效养分而言,与裸沙相比,裸露地藓类结皮覆盖降低了土壤速效氮含量,增加了速效磷和速效钾含量;而灌丛下藓类结皮覆盖提高了土壤速效氮和速效钾的含量,但降低了速效磷的含量。(3)相关性分析显示,在0—2 cm土壤中速效磷与速效氮呈现显著负相关,而在2—6 cm速效磷与速效氮呈现显著正相关(P<0.01)。(4)贡献度分析表明,土壤中灌丛效应对养分的贡献(42.54%)要远大于藓类结皮的贡献(2.43%),但二者交互作用却降低了除速效氮以外的其他土壤养分含量。综上,灌丛、藓类结皮覆盖和土层深度变化对土壤碳、氮、磷和钾养分均具有显著影响(P<0.05),但三者间的交互效应对养分的影响不显著(P>0.05)。相对于裸露地,灌丛与藓类结皮的覆盖均对表层土壤碳、氮、磷和钾养分具有促进作用,且随着土层深度的下降,土壤养分含量呈现显著的下降趋势(P<0.05)。因此,在荒漠生态系统中耐旱灌丛与生物土壤结皮这两个最重要的斑块单元联合调控了微尺度土壤养分的空间异质性变化。

Loess in the Tian Shan and its implications for the development of the Gurbantunggut Desert and drying of northern Xinjiang

Eolian loess is widely distributed on the various geomorphic surfaces between 700-2400 m a.s.l. on the northern slope of the Tian Shan. It is formed in a synchronous manner with dust transported from the Gurbantunggut Desert in the Junggar Basin. The thickest section of loess was found in the Shawan and Shihezi regions. Paleomagnetic and climatic proxy analyses of over 71 m of a loess-paleosol sequence on the highest terrace of the Qingshui He (River) in the Shawan show that the paleomagnetic Bruhues/Matuy-ama (B/M) boundary lies at the bottom of paleosol S8, at a depth of 69.5 m, and the bottom of the sequence was estimated to be -0.8 Ma. This implies that the extremely dry climatic conditions in the Junggar Basin and the initial Gurbantunggut Desert were present at least by 0.8 Ma. High-resolution grain size series demonstrate that this area and desert expansion experienced two dramatic periods of desert expansions that occurred at -0.65 Ma and 0.5 Ma, respectively; and the subsequent continuous

Respondence and feedback of modern sand deserts to climate change ——A case study in Gurbantunggut Desert

The research on the respondence and feedback of modern sand deserts to the climate change is an important component part in the studies on the global climate change. Deserts respond to the climate change, meanwhile, they affect the climate with their feedback of peculiar environment during the respondence. Many researches on desert climate have been carried out at home and abroad. However, there is little research on the respondence and feedback of modern fixed, semi-fixed and mobile deserts in arid areas to the climate change, in which the factor analysis as well as the parameter changing effects is especially the difficult problem all along. In this note, the parameters of the respondence and feedback of Gurbantunggut Desert to the climate change are measured and analyzed, some variable parameters of water-heat exchange are obtained, and a numerical model of desertification is developed according to a series of climate change of about 40 years and the variable relations of meteorological and physical

Responses of ephemeral plant germination and growth to water and heat conditions in the southern part of Gurbantunggut Desert

在 Gurbantunggut 沙漠的南部的部分的短暂植物系统地从 2002 ～ 2004 被监视，气象学的数据和土壤潮湿在一样的时期期间被分析。结果证明短暂植物萌芽和生长对水和热状况的变化敏感。超过 0 的每日的温度的时间 ?????????

Arbuscular mycorrhizal associations in the Gurbantunggut Desert

在位于 Xinjiang 的 Gurbantunggut 沙漠的植物，中国是改编的干旱种类并且在通常滋养穷人的土壤成长。调查在沙漠被进行决定与合适的荒芜的植物联系的 arbuscular mycorrhizal (AM ) 地位从 annuals 和 perennials 的 11 个家庭的 to23 种类。从所有植物的根为决定 mycorrhizal 殖民的地位和程度的内部、外部的 hyphae，泡和 coils/arbuscules 的存在被检验。调查的植物种类，(61%) 14 被发现形成 AMassociations，(22%) 5 是可能的 AM 开拓殖民地于种类，并且 4 是 non-my-corrhizal 植物。形成 AM 的 annuals 和灌木的 Theproportions 分别地是比 perennials 和植物的那些显著地低的。孢子密度在根地区的土壤每 20 g 从 5 ～ 21 变化了。在 3 个类的上午 14 点 fungaltaxa 被孤立并且识别了其 10 属于血管球， 3 到 Acaulospora， and1 到 Archaeospora。血管球是在识别的所有类的主导的类。G。deser-ticola 和 G.etunicatum 是最普通的税一孤立与 77.4% 和 74.8% 的出现频率，并且相对许多 14.4% 和 15.5% 分别地。

Temporal-spatial dynamics of distribution patterns of microorganism relating to biological soil crusts in the Gurbantunggut Desert

生物土壤外壳用作贡献沙固定的一个重要生物因素。这研究被进行在关于地点的外壳中调查微生物的时间空间的可变性，沙沙丘和季节的土壤层。在苔藓主导的内部沙丘的区域，更高的土壤营养素和水集中是可能的维持微生物引起的活动。细菌显示出解决和生长的最高的能力在在春天和秋天内部沙丘。土壤水内容在内部沙丘的区域在土壤外壳中到达了最高的价值，特别在春天。放线菌和真菌的数量的变化基本上在沙沙丘的不同地点显示出一致趋势。与加深土壤层，因为环境因素在春天和秋天波动，每个微生物组的数量的垂直分发显示出不同特征。在不同微生物组之中，细菌是占优势的，在在所有的春天和秋天的放线菌下一个和真菌最少玷污层(020 厘米) 。细菌和土壤水内容的比例比在在所有土壤层(020 厘米) 的秋天的那些在春天是更高的。没有一致趋势在放线菌和真菌被发现。结果证明微生物的数量是显著地积极的与有机物内容相关，土壤水满意的、全部的 N，全部的 P，可得到的 P，可得到的 K， pH，电的传导性，全部的盐内容，过氧化氢酶， urease，磷酸酶和碱的磷酸酶。

古尔班通古特沙漠东南部不同类型沙丘土壤水分与地形-植被因子关系

[目的]揭示古尔班通古特沙漠土壤水分的分布规律及其与地形—植被因子的关系,对制定相应的防风固沙措施以及建立科学合理的植物固沙模式有积极的指导作用。[方法]以古尔班通古特沙漠东南部地区3种不同类型沙丘(固定、半固定和流动沙丘)为研究对象,利用方差分析和冗余分析等方法对3种不同类型沙丘上4种微地貌类型(迎风坡、背风坡、丘顶、丘底)不同深度土壤水分(0—40 cm, 40—200 cm, 200—300 cm)分布特征及其与地形—植被因子之间的关系进行综合分析。[结果](1)所有类型沙丘上0—300 cm土壤水分的波动程度随深度的增加逐渐减小,表层土壤水分的波动程度大于中层和深层。(2)所有类型沙丘不同深度的土壤水分有显著的差异,且背风坡、丘底和迎风坡3种微地貌类型上土壤水分相对较为集中。(3)地形—植被因子对研究区绝大多数(半)固定沙丘的土壤水分呈负相关关系,对(半)固定沙丘不同深度土壤水分影响较流动沙丘更为明显。[结论]所有类型沙丘上的土壤水分受地形因子的影响较植被因子强,而且影响不同类型沙丘土壤水分的主要地形—植被因子也不同。

Damage and recovery of the Gurbantunggut Desert vegetation following engineering activities

The fragile ecological environment of the Gurbantunggut Desert is damaged/disturbedby human activities relating to the development of oil-gas resources and the constructions of de-sert road and great engineering in the Jungger Basin. It was mainly represented: soil compaction,vegetation cleaning, burial of vegetation, oil polluting, and soil disturbance. With investigation andexperiment, we found that when the way and intensity of engineering activities disturbing theeco-environment does not make its ecological stability disintegrated, the desert vegetation has acapacity of natural recovery. To speed and strengthen the process of vegetation recovery efficientassistant measurements, including stabilizing mobile sands promptly and sowing seeds of shruband herb plants in good time will be needed.

Chlorophytes of biological soil crusts in Gurbantunggut Desert,Xinjiang Autonomous Region,China

In this paper,chlorophytes collected from 253 biological soil crust samples in Gurbantunggut Desert in Xinjiang Autonomous Region,China were studied by field investigation and microscopical observation in lab.The flora composition,ecological distribution of chlorophytes in the desert and dynamic changes of species composition of chlorophytes in different developing stages of biological soil crusts are preliminarily analyzed.Results showed that there were 26 species belonging to 14 genera and 10 families,in which unicellular chlorophytes were dominant.There existed some differences in distribution of varied sand dune positions.The taxa of chlorophytes in leeward of sand dunes are most abundant,but the taxa in windward,interdune and the top of sand dunes reduced gradually.Chlorophytes were mainly distributed within the crust and the taxa of chlorophytes decrease obviously under the crust.In the devel-oping stages of the biological soil crust,species diversity of chlorophytes changed a little,but species composition pre-sented some differences.Chlorococcum humicola,Chlorella vulgaris,Chlamydomonas ovalis and Chlamydomonas sp.nearly existed in all developing stages of biological crusts.In several former stages of the biological soil crust there were spherical chlorophytes and filamentous ones.When moss crust formed,filamentous chlorophytes disappeared,such as Microspora and Ulothrix.

Distribution of plant species and species-soil relationship in the east central Gurbantunggut Desert, China

在在东方的种类和土壤因素之间的植物种类和关系的分发 Gurbantunggut 沙漠的中央部分被学习提供更多的卓见进植物群并且越过沙漠的各种各样的部分在植被决定差别。双向簇分析证明在区域的植被能被划分成三个组，第一个组被灌木种类， Ephedra przewalskii 和草种类统治，主要在扁平的根据和轻轻的斜坡的区域的 Carex physodes；第二个组被 C 统治。physodes， Artemisia songorica 和 A。主要沙沙丘和第三个组的斜坡上的 xerophytica 被灌木种类统治，主要沙沙丘的顶上的 Haloxylon persicum。在植物密度在之间没有差别组织 1 和 2，但是在组 3 有重要减少。不到植被组 3 的土壤水比在其它，二个组根本玷污深度的低得多。EC，有机物，全部的 P 和可溶的 Na， Ca 和 Mg 与土壤水很同样变化了。正规通讯分析(CCA ) 令人满意地在区域估计了种类土壤关系。植物种类的分发强烈与水内容，有机物， EC 和营养素的土壤因素被相关。在三把 CCA 斧子解释的种类出现的变化是大约 70% ，显示一些解释地点变量可以在我们的学习参数外面存在。土壤质地被建议在未来研究被包括改进 CCA 的解释。

Effects of drought treatment on photosystemⅡactivity in the ephemeral plant Erodium oxyrhinchum

Drought is a critical limiting factor affecting the growth and development of plants in arid and semi-arid areas.Photosynthesis,one of the most important physiological processes of plants,can be significantly inhibited by drought.PhotosystemⅡ(PSⅡ)is considered the main attack target when photosynthesis is affected by drought.To clarify how PSⅡcomponents of the ephemeral plant Erodium oxyrhinchum(grown in the Gurbantunggut Desert,China)respond to drought treatment,we evaluated the functional activity of PSII by determining chlorophyll fluorescence and gas exchange parameters under different drought treatment levels(control(400 mL),moderate drought(200 mL),and severe drought(100 m L)).Under moderate drought treatment,significant decreases were found in net photosynthetic rate(Pn),effective quantum yield of PSII(Y(Ⅱ)),relative electron transfer rate of PSII(rETR(Ⅱ)),oxygen-releasing complex,probability of an absorbed exciton moving an electron into the electron transport chain beyond primary quinone receptor Q_(A)-(Φ(E_(o))),probability of a trapped exciton moving an electron into the electron transport chain beyond primary quinone receptor Q_(A)-(ψ(E_(o))),and performance index of PSⅡ(PI_(abs)).Compared to control treatment,marked increases were observed in water use efficiency(WUE),relative variable fluorescence at the J step(V_(J)),initial fluorescence(F_(o)),and dissipated energy per active reaction center(DI_(o)/RC)under moderate drought treatment,but there were no substantial changes in semi-saturated light intensity(I_(K)),active reaction centers per cross-section(RC/CS),and total performance index of PSII and PSI(PI_(total),where PSI is the photosystemⅠ).The changes of the above parameters under severe drought treatment were more significant than those under moderate drought treatment.In addition,severe drought treatment significantly increased the absorbed energy per active reaction center(ABS/RC)and trapping energy per active reaction center(TR_(o)/RC)but decreased the energy transmission connectivity of PSⅡcomponents,RC/CS,and PI_(total),compared to moderate drought and control treatments.Principle component analysis(PCA)revealed similar information according to the grouping of parameters.Moderate drought treatment was obviously characterized by RC/CS parameter,and the values of F_(o),V_(J),ABS/RC,DI_(o)/RC,and TR_(o)/RC showed specific reactions to severe drought treatment.These results demonstrated that moderate drought treatment reduced the photochemical activity of PSII to a certain extent but E.oxyrhinchum still showed strong adaptation against drought treatment,while severe drought treatment seriously damaged the structure of PSⅡ.The results of this study are useful for further understanding the adaptations of ephemeral plants to different water conditions and can provide a reference for the selection of relevant parameters for photosynthesis measurements of large samples in the field.