Potential distribution of Haloxylon ammodendron in Central Asia under climate change

Understanding the spatial distribution of plant species and their dynamic changes in arid areas is crucial for addressing the challenges posed by climate change.Haloxylon ammodendron shelterbelts are essential for the protection of plant resources and the control of desertification in Central Asia.Thus far,the potential suitable habitats of H.ammodendron in Central Asia are still uncertain in the future under global climate change conditions.This study utilised the maximum entropy(MaxEnt)model to combine the current distribution data of H.ammodendron with its growth-related data to analyze the potential distribution pattern of H.ammodendron across Central Asia.The results show that there are suitable habitats of H.ammodendron in the Aralkum Desert,northern slopes of the Tianshan Mountains,and the upstream of the Tarim River and western edge of the Taklimakan Desert in the Tarim Basin under the current climate conditions.The period from 2021 to 2040 is projected to undergo significant changes in the suitable habitat area of H.ammodendron in Central Asia,with a projected 15.0% decrease in the unsuitable habitat area.Inland areas farther from the ocean,such as the Caspian Sea and Aralkum Desert,will continue to experience a decrease in the suitable habitats of H.ammodendron.Regions exhibiting frequent fluctuations in the habitat suitability levels are primarily found along the axis stretching from Astana to Kazakhskiy Melkosopochnik in Kazakhstan.These regions can transition into suitable habitats under varying climate conditions,requiring the implementation of appropriate human intervention measures to prevent desertification.Future climate conditions are expected to cause an eastward shift in the geometric centre of the potential suitable habitats of H.ammodendron,with the extent of this shift amplifying alongside more greenhouse gas emissions.This study can provide theoretical support for the spatial configuration of H.ammodendron shelterbelts and desertification control in Central Asia,emphasising the importance of proactive measures to adapt to climate change in the future.

Antibacteria Activity of Peganum harmala and Haloxylon salicornicum Leaves Extracts

The use of antibiotics in humans and animals has been marked as a significant step in health due to their effectiveness in controlling and treating bacterial infections. The misuse and overuse of antibiotics have been identified as risk factors for bacterial resistance since microorganisms adapt and develop mechanisms to defend against antibiotics. According to the Centers for Disease Protection and Control (CDC), around 23,000 individuals die every year in the United States due to antibiotic resistance complications. As a result, a demand for alternative treatments has been a goal for scientists as the microbes adapt to selective pressure. The aim of this study is to test the antibacterial activity of leaf extracts of Peganum harmala and Haloxylon salicornicum on both Gram-positive and Gram-negative bacteria on various mediums. The results of the study showed that both P. harmala and H. salicornicum inhibited the bacterial growth in two different media. The results were also compared with different common antibiotics used in both human’s and animal’s fields and showed a promising outcome as alternative antibiotics.

Simulation of Haloxylon Ammodendron Stand Basic Diameter Structure Based on Fuzzy Distribution Function

Based on the investigation data of 12 Haloxylon ammodendron plots in the south edge of Gurbantunggut Desert, Fuzzy distribution was introduced into the study of Haloxylon ammodendron base diameter structure fitting according to the consistency between the characteristics of Fuzzy distribution function and the distribution series of cumulative percentage of stand base diameter, and the fitting precision and effect of Fuzzy distribution function were discussed. The root mean square error RMSE and determination coefficient R2 values showed that Fuzzy-Γ1, Fuzzy-Γ2, Fuzzy-Γ3, Fuzzy-Γ4 had good fitting performance, among which Fuzzy-Γ1 had relatively high fitting precision, and its parameters were closely related to stand age and density, Fuzzy-Γ2 distribution function was the second, and Fuzzy-Γ4 distribution function had the worst fitting effect. By introducing a parameter c from the similarity of four distribution function formulas, a generalized Fuzzy distribution function Fuzzy-Γ5 is obtained. This function shows the highest fitting accuracy. Most of the values of parameter c are near 1 or 2, which shows that the diameter distribution is mainly approximate to Fuzzy-Γ1 and Fuzzy-Γ2.

Increased Storability of Haloxylon ammodendron Seeds in Ultra-drying Storage

梭梭 (HaloxylonammodendronBge .)的种子为短命种子 ,在自然状态下 ,种子的含水量为 8.5 % ,寿命约为 10个月。将梭梭种子含水量降至 2 .5 %和 1.4% ,其耐贮藏力增强。经过 5 0℃下 5d和 10d的人工加速老化后 ,超干种子表现出较强的抗老化能力。与对照相比 ,超干种子具有较高的萌发率、活力指数及较长的根 。

Effects of water stress on Haloxylon ammodendron seedlings in the desert region of Heihe inland river watershed, Gansu Province, China

The water relation and leaf gas exchange of saxoul (Haloxylon Ammodendron Bge, a C4 shrub) seedlings were studied under water stress in 2001. Saxoul seedlings maintained high transpiration when the soil moisture was above 11%. The seedlings were able to take up water from soil with above 6 % soil water content, which was the threshold level of soil moisture for seedlings. The relationship between transpiration and potential evaporation was linear for well-watered seedlings. The de-crease of soil water availability led to different degrees of down-regulation of stomatal conductance, leaf transpiration and net CO2 assimilation rate. The stomata played a relatively small part in determining the net CO2 assimilation rate for the same seedling. The relationship between net CO2 assimilation rate and transpiration was linear diurnally, and reduction scale of leaf transpiration was much bigger than that of net CO2 assimilation rate by waters tress treatments, therefore intrinsic wa-ter-use-efficiency increased. High evaporative demand increased the leaf transpiration but inhibited net CO2 assimilation rate. Because of the effect of VPD on transpiration in this region, the transpiration of well-watered and mild water stress seedlings becomes responsive to change in stomatal conductance over a wider range.

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.

梭梭(Haloxylon ammodendron)生理与个体用水策略对降水改变的响应

随着全球变化的加剧,降水改变正导致荒漠生态系统中植物用水策略的适应性变化;对降水变化响应的种间差异性影响着荒漠植物群落组成。研究将生理生态与个体形态尺度相结合,调查中亚荒漠关键种梭梭Haloxylon ammodendron对降水变化导致的自然生境中水分条件改变的响应与适应。实验于2005年生长期开展,在古尔班通古特沙漠南缘原始盐生旱生荒漠中设置3个降水梯度(自然、双倍和无降水);观测并比较不同降水条件下光合作用、蒸腾作用、叶水势、水分利用效率、地上生物量累积和根系分布的变化。结果表明,梭梭主要利用降水形成的浅层土壤水维持生存;有效的形态调节和较强的气孔控制是其维持光合能力以及适应降水变化的主要机制;降水增多对其产生正效应,预示着梭梭可能在未来种间竞争和群落演替中占有优势。

塔克拉玛干沙漠腹地梭梭(Haloxylon ammodendron)蒸腾耗水规律

塔里木沙漠公路防护林生长于极端干旱的塔克拉玛干沙漠中，防护林植物的蒸腾耗水和灌溉管理是防护林可持续的核心问题。利用植物茎流计连续测定了塔里木沙漠公路塔中段防护林植物梭梭的茎干液流、蒸腾耗水量。结果表明：梭梭茎干液流具有明显昼夜节律性，液流的高峰值出现在白天10：00～15：00，最小值出现在0：00～03：00，夜间也保持较小的液流；茎干液流受环境因子影响而波动，太阳辐射、气温和风速与茎干液流有较明显的正相关关系，相对湿度和茎干液流呈负相关关系；滴灌条件下，防护林带内土壤含水量充足且在各个月份变化不大，土壤含水量对茎干液流影响不大；依据清晨和午后水势变化，梭梭体内水分在夜间得到了较好的恢复；在一个生长季内，3株直径为2．0、2．8、3．4cm的梭梭总的耗水量分别为295、436、616kg，日平均耗水量分别为1．48、2．18、3．08kg；现行灌溉模式提供了充足的水分供应，梭梭的水分状况良好；在充足水分条件下，梭梭有较大的蒸腾耗水量，干旱的环境条件和较为充足的水分供应是梭梭耗水量大的主要原因；依据梭梭的水分状况，当前水分管理为防护林提供了较充足的水分。

柽柳(Tamarix spp.)和梭梭(Haloxylon ammodendron)的“肥岛”效应

灌丛"肥岛"是全球干旱生态系统中的普遍现象,其发生和发展对干旱灌木、草原生态系统的结构和功能都具有重要影响,但其物种效应容易得到忽视。对准噶尔盆地南缘柽柳(Tamarix spp.)和梭梭(Haloxylon ammodendron)这两种不同地表形态灌木的冠下、冠缘和灌丛间地3种生境的土壤进行了采样、分析,结果表明:(1)柽柳和梭梭都存在"肥岛"现象,主要表现在土壤表层,其土壤性状与"岛"外土壤的差异随土壤深度增加而减弱;(2)生物性限制土壤养分由"岛"内向外梯度递减,而非生物性限制土壤要素可能高于、也可能低于"岛"外土壤,或者两者无显著差异;(3)从"肥岛"的空间尺度来看,柽柳"肥岛"的水平范围可能超出了本身冠幅覆盖区,而梭梭"肥岛"要小于本身冠幅覆盖区,其深度亦小于柽柳"肥岛";(4)相对于不同土壤要素而言,即使是同一物种,其"肥岛"也具有不同的空间范围。总的来看,研究区灌丛"肥岛"的发育具有明显的物种效应,相对梭梭而言,柽柳"肥岛"发育更广、更深,养分聚集更明显,其原因主要是柽柳的半球型树冠更利于保护和捕获凋落物,而较多的凋落物输入与土壤结构和土壤养分间的正反馈机制使柽柳冠下加速的生物地球化学循环能达到更广、更深的范围。灌丛"肥岛"的发育是干旱景观中生物过程与物理过程交互作用的产物,全面揭示其形成机理,探讨其对干旱生态系统结构、功能与动态的影响,需要更系统的研究。

梭梭(Haloxylon ammodendron(C.A.Mey.)Bunge)物候期的观察

梭梭是我国西北荒漠半荒漠地区的珍稀植物。通过对生长在内蒙古自治区阿拉善盟的天然梭梭林连续三年的观察测定 ,将其物候期划分为萌动期、营养枝扩展期、开花期、果实成熟期和营养枝脱落期五个主要物候期。对各个时期梭梭的形态特征进行了较为详尽的描述 。

荒漠区固沙植物梭梭(Haloxylon ammodendron)耗水特征

利用SF-300热脉冲树干液流仪,连续观测了生长季节荒漠区固沙植物梭梭树干液流速率,研究了荒漠区固沙植物梭梭林木的耗水量及其与气象因子的关系。结果表明:在生长季节,梭梭树干液流速率昼夜变化小;不同的生长日,梭梭树干液流速率介于(5.9±0.7)～(14.5±3.6)gcm-2h-1;观测期间,梭梭平均日耗水量为(0.3±0.2)mm,生长季节单株木耗水量达49·4mm。树干液流速率对气象因子均有一定程度的响应,且在不同时间的影响程度不同。日耗水量与林冠投影面积、基径、基径的平方乘以树高的积、边材厚度和边材面积呈线性关系。

荒漠灌木梭梭(Haloxylon ammodendron)周围土壤微生物的空间分布

以古尔班通古特沙漠荒漠生态系统中主要优势种——梭梭(Haloxylon ammodendron)冠幅内外的土壤为研究对象,通过分析从树干基部向外水分和养分变化下土壤微生物生物量、多样性和群落组成的变化规律,试图揭示荒漠生态系统中土壤微生物空间分布的基本特征。微生物生物量和多样性采用磷脂脂肪酸进行测定。结果表明:从树干基部向外,土壤微生物总生物量、多样性以及不同微生物类群的生物量均随土壤水分和养分含量降低而逐渐降低,指示了土壤微生物从裸地向内集聚分布的特征。另外,在微生物群落组成中,不同类群微生物的生物量从树干基部向外的减少程度有所不同,例如,从树干基部附近5 cm处到冠外裸地200 cm处,真菌、细菌、革兰氏阳性菌、革兰氏阴性菌的生物量分别减少了50.25%、84.06%、82.70%、92.57%,指示了细菌从裸地向内集聚分布的程度强于真菌,革兰氏阴性菌从裸地向内集聚分布的程度也较强于革兰氏阳性菌。研究表明,在资源稀缺的荒漠生态系统中,土壤微生物倾向于分布在冠内资源丰富的区域。土壤微生物的空间分布不仅与资源的丰富度有关,而且与微生物自身对环境变化的忍耐性或敏感性有关。

古尔班通古特沙漠南缘非灌溉条件下梭梭(Haloxylon ammodendron)蒸腾耗水特征

利用热平衡包裹式茎流计连续测定了古尔班通古特沙漠南缘原生梭梭2010年5月6日～10月12日的茎干液流及气象因子数据,探究了非灌溉条件下不同直径梭梭在其蒸腾耗水特性及与气象因子相关性之间的差异。结果表明:(1)茎干液流昼夜变化规律明显,蒸腾日变化呈双峰或多峰趋势,夜间保持较小液流;午休现象多出现于14∶00～16∶00。相同环境因子影响下,直径越大,茎干液流速率越大,午休现象也越明显;(2)在生长季,不同直径梭梭液流的启动和停止时间存在差异,6～8月,直径越大,液流启动时间越早,停止时间越晚。同一植株液流在不同月份的启动和停止时间差异较大,生长初期,液流启动早,停止迟;生长季末期,液流启动迟,停止早;(3)5～8月,液流日累积过程呈明显的"S"型趋势;9～10月,呈斜率一致的一条直线。直径越大,日累积量和累积速率越大,第一拐点到达时刻越早,第二拐点到达时刻越晚;(4)液流速率与太阳辐射的相关性最好,其次为气温和相对湿度,风速最小;相关性在7月份最大,6月和8月次之,10月最小。相同环境条件下,直径越大,其液流速率对气象因子的响应越明显;(5)观测时段内,7月耗水最多,6月、8月、9月次之,5月和10月最少。直径越大耗水量越多,直径9.9、13.4、22.9 cm日均耗水量为0.570、0.595、0.694 mm,总耗水量为92.904、96.923、113.052 mm,液流通量为0.263、0.284、0.346 L.cm-2.d-1。与干旱区不同生境的梭梭相比,古尔班通古特沙漠原生梭梭的液流通量相对较小。不同地点和生境的梭梭在耗水数量、耗水日过程特性等方面差异明显,这为天然荒漠植被防护林的管理及沙漠区人工灌溉植物的水资源合理配置提供了一定的决策支持。

盐胁迫对梭梭(HaloxylonammodendzonBge.)幼苗体内保护酶系统活性的影响

分别用０、１％、２％、３％和４％ＮａＣｌ盐溶液处理梭梭幼苗１２ｈ．测定体内ＳＯＤ、ＣＡＴ和ＰＯＤ活性，ＭＤＡ和蛋白质含量，电导率．结果表明：梭梭幼苗在适当的ＮａＣｌ胁迫下，体内能维持较高的保护酶活性；较低的膜脂过氧化作用和细胞膜透性．说明梭梭具有较强的耐盐性．

果翅对梭梭属(Haloxylon)种子萌发行为的调控

种子萌发行为的受控机制是生殖生态学的重要研究内容。通过果翅存留实验研究了在不同贮藏时期果翅对梭梭和白梭梭种子萌发的影响。结果表明:①新成熟的梭梭种子具有高的萌发率(>90%)。梭梭果翅对秋天新成熟的种子萌发有显著的抑制作用(萌发率<50%),使种子处于强迫休眠状态;果翅对种子萌发的抑制作用随着贮藏时间的推移逐渐降低,到翌年春天(4月)这种抑制作用已完全解除,果翅对梭梭种子的抑制主要是化学抑制。果翅对梭梭种子萌发行为的调控作用确保了种子在合适的时间萌发与种群的成功定居,也正是梭梭在荒漠地区广泛分布的主要原因。②新成熟的白梭梭种子萌发率为59.5%,贮藏1个月后达到80%,表明种子存在短时期的生理后熟现象。白梭梭果翅在每一贮藏时期对其种子的萌发都具有显著的抑制作用,翅+种子(将果翅与种子剥离,一起放入培养皿中)也部分地抑制种子的萌发,因此,果翅对白梭梭种子萌发的抑制既有化学抑制也存在机械抑制。果翅对种子萌发的抑制,限制了白梭梭的分布。

梭梭(Haloxylon ammodendron)愈伤组织诱导及植株再生

以梭梭(Haloxylon ammodendron)无菌苗的茎尖、子叶、下胚轴为材料进行愈伤组织诱导,培养基中单独添加1～3mg/L的2,4-D或与0.5mg/L的6-BA配合使用,均能成功诱导出愈伤组织,但在愈伤组织诱导起始阶段,用含2,4-D 2.0mg/L、BA 0.5mg/L的培养基效果较好;在2,4-D1.0mg/L、BA 0.5mg/L的分化培养基上经过两次连续继代培养后,在含BA 0.5mg/L、IAA 1.0mg/L的培养基上愈伤组织生长状态最好,并从茎尖诱导的愈伤组织上获得了再生植株.

Soil properties and herbaceous characteristics in an age sequence of Haloxylon ammodendron plantations in an oasis-desert ecotone of northwestern China

Haloxylon ammodendron, a typical desert shrub with C4 pathway of photosynthesis, possessing a strong ability to adapt to an extreme drought environment, has a rapid growth rate in sandy lands and is widely used in sand-fixing shelter-forest systems in oasis-desert ecotones. To assess the effects of H. ammodendron plantation on the soil, we measured soil properties and herbaceous characteristics along a nearly 40-year chronosequence after H. ammodendron was planted in shifting sand dunes in an oasis-desert ecotone. Results showed that silt and clay fractions increased significantly in the topsoil. The accumulation rates of soil organic carbon （SOC）, total nitrogen （TN） and total phosphorus （TP） were faster in the early stages （0-9 years） and slower in the late stages （9-39 years）. The soil pH and electrical conductivity （EC） were higher than those in the non-vegetation dunes. Moreover, the soil properties in the topsoil （0-5 cm） showed larger variation scope than those in the deeper soil layers （5-20 cm）. The significant relationships of the soil silt＋clay content with the chemical properties mainly appeared in the topsoil. The wind erosion susceptibility of the soil, evaluated by erodible fraction （EF）, decreased significantly with increasing H. ammodendron plantation age. Additionally, the annual pioneer herb, Agriophyllum squarrosum, was gradually substituted by the annual salt-tolerant herb, Bassia dasyphylla, with increasing plantation age. These results showed beneficial effects of H. ammodendron plantation on improving soil conditions. However, the dynamics of the herbaceous species also reminded us that the long- term effects of H. ammodendron plantation, especially on changes in vegetation composition, still need further evaluation.

梭梭(Haloxylon ammodendron)组织培养和快繁技术

为了优化梭梭分化苗生根的培养基配方和培养条件,以剪去幼根的梭梭无菌苗茎、叶部分作为外植体,通过芽生芽途径获得了梭梭再生苗,重点对生根培养基和培养条件进行了系统的研究,根据试验结果得出结论:梭梭腋芽诱导培养基为MS+6-BA 2 mg.L-1,壮苗培养基为MS+6-BA 1.5 mg.L-1+GA3 1.0 mg.L-1,生根培养基为1/4MS+5%蔗糖+IBA0.2 mg.L-1+NAA 0.8 mg.L-1,生根率为74%。

What makes Haloxylon persicum grow on sand dunes while H. ammodendron grow on interdune lowlands: a proof from reciprocal transplant experiments

Determining the mechanisms underlying the spatial distribution of plant species is one of the central themes in biogeography and ecology. However, we are still far from gaining a full understanding of the autecological processes needed to unravel species distribution patterns. In the current study, by comparing seedling recruitment, seedling morphological performance and biomass allocation of two Haloxylon species, we try to identify the causes of the dune/interdune distribution pattern of these two species. Our results show the soil on the dune had less nutrients but was less saline than that of the interdune; with prolonged summer drought, soil water availability was lower on the dune than on the interdune. Both species had higher densities of seedlings at every stage of recruitment in their native habitat than the adjacent habitat. The contrasting different adaptation to nutrients, salinity and soil water conditions in the seedling recruitment stage strongly determined the distribution patterns of the two species on the dune/interdune. Haloxylon persicum on the dunes had lower total dry biomass, shoot and root dry biomass, but allocated a higher percentage of its biomass to roots and possessed a higher specific root length and specific root area by phenotypic traits specialization than that of Haloxylon ammodendron on the interdune. All of these allowed H. persicum to be more adapted to water stress and nutrient shortage. The differences in morphology and allocation facilitated the ability of these two species to persist in their own environments.

The establishment and development of Haloxylon ammodendron promotes salt accumulation in surface soil of arid sandy land

Haloxylon ammodendron, a representative C_4 succulent xerophyte and salt-secreting plant, is widely used in vegetation reestablishment programs to stabilize shifting sand, and is one of the dominant shrubs in the shelter belt used to control desertification in the desert-oasis ecotone in northwestern China. In this study, we collected soil samples in an age sequence of 0-, 2-, 5-, 13-, 16-, 31-, and 39-year-old H. ammodendron plantations to assess the effects of the shrub on soil fertility and salinity. Results show that SOC and total N concentrations increased significantly with increasing plantation age and increased 5.95-(in the interspaces) to 9.05-fold(under the canopy) and 6.15-to 8.46-fold at the 0-5 cm depth at the 39-year-old plantation compared with non-vegetated sandy land. Simultaneously, H. ammodendron establishment and development resulted in significant salt accumulation in the surface layer. On average, total soil salt content at the 0-5 cm and 5-20 cm depth increased 16.8-fold and 4.4-fold, respectively, compared with non-vegetated sandy land. The increase of total salt derived mostly from the accumulation of SO_4^(2-), Ca^(2+) and Na^+ with H. ammodendron development. The accumulation in salinity was more significant than the increase in fertility, suggesting that improved soil fertility did not limit the impact of salinization. The adverse effect of salt accumulation may result in H. ammodendron plantation degradation and impact community stability in the long run.