不同土壤水盐条件下多枝柽柳(Tamarix ramosissima)对胡杨(Populus euphratica)幼苗的影响

目前胡杨更新困难,种群处于退化阶段,而与其生态位高度重叠的多枝柽柳却在扩张。为探讨多枝柽柳对胡杨生长的影响,本研究设置了3个水平的水分、盐分梯度,对胡杨进行了单种和混种的盆栽控制实验,通过测定胡杨幼苗的生长和存活状况,分析不同水、盐梯度下多枝柽柳如何影响胡杨生长。结果表明:(1)多枝柽柳伴生降低当年生胡杨幼苗的存活率,随着水分条件改善,胡杨存活率提高,而盐分对存活率没有显著的影响。(2)水分、盐分和伴生模式几个因子对胡杨的生长特征的影响存在显著的交互作用(P<0.05)。各水盐条件下,多枝柽柳会不同程度降低胡杨幼苗的株高、主根长和地上地下生物量,而根冠比增大。混种条件下,胡杨幼苗对水盐的响应更为敏感。(3)相对竞争强度对水盐环境有明显的响应(P<0.05),随水分条件改善,地上、地下相对竞争强度降低。多枝柽柳对胡杨的生长产生不良影响的机制是通过快速消耗土壤的水分,从而导致胡杨幼苗水分亏缺。土壤水分条件是胡杨和多枝柽柳幼苗共存的关键因素,在水分供给不足的情况下,对水分偏好的差异导致胡杨无法通过实生苗进行有效的更新从而加剧胡杨种群的衰退,而多枝柽柳更为耐旱的特性使其逐步占据河岸的生境。我们的研究结果强调了两个树种对环境因子的适应性差异决定了河岸带植被发育过程中植物-土壤的相互作用导致胡杨在演替过程中表现出的衰退现象。

Patterns,magnitude,and controlling factors of hydraulic redistribution of soil water by Tamarix ramosissima roots

Tamarix spp. （Saltcedar） is a facultative phreatophyte that can tolerate drought when groundwater is not accessed. In addition to deep water uptake, hydraulic redistribution （HR） is another factor contributing to the drought tolerance of Tarnarix spp. In this study, data on soil volumetric moisture content （0）, lateral root sap flow, and relevant climate variables were used to investigate the patterns, magnitude, and controlling factors of HR of soil water by roots of Tamarix ramosissima Ledeb. in an extremely arid land in Northwest China. Results showed evident diurnal fluctuations in 0 at the depths of 30 and 50 cm, indicating ＂hydraulic lift＂ （HL）. 0 increased remarkably at 10 and 140 cm but decreased at 30 and 50 cm and slightly changed at 80 cm after rainfall, suggesting a possible ＂hydraulic descent＂ （HD）. However, no direct evidence was observed in the negative flow of lateral roots, supporting HR （including HL and HD） of T. ramosissima. The HR pathway unlikely occurred via lateral roots; instead, HR possibly occurred through adventitious roots with a diameter of 2-5 mm and a length of 60-100 cm. HR at depths of 20-60 cm ranged from 0.01-1.77 mm/d with an average of 0.43 mm/d, which accounted for an average of 22% of the estimated seasonal total water depletion at 0-160 cm during the growing season. The climate factors, particularly vapor pressure deficit and soil water potential gradient, accounted for at least 33% and 45% of HR variations with depths and years, respectively. In summary, T. ramosissima can be added to the wide list of existing species involved in HR. High levels of HR may represent a considerable fraction of daily soil water depletion and substantially improve plant water status. HR could vary tremendously in terms of years and depths, and this variation could be attributed to climate factors and soil water potential gradient.

Intra-annual stem diameter growth of Tamarix ramosissima and association with hydroclimatic factors in the lower reaches of China's Heihe River

High-resolution observations of cambial phenology and intra-annual growth dynamics are useful approaches for understanding the response of tree growth to climate and environmental change. During the past two decades, rapid socioeconomic development has increased the demand for water resources in the oases of the middle reaches of the Heihe River in northwestern China, and the lower reaches of the Heihe River have changed from a perennial river to an ephemeral stream with a decreased and degraded riparian zone. Tamarisk（Tamarix ramosissima） is the dominant shrub species of the desert riparian forest. In this study, the daily and seasonal patterns of tamarisk stem diameter growth, including the main period of tree ring formation, were examined. Observations concerning the driving forces of growth changes, along with implications for the ecology of the dendrohydrological area and management of desert riparian forests in similar arid regions, are also presented. The diurnal-seasonal activity of stem diameter and the dynamics of growth ring formation were studied using a point dendrometer and micro-coring methods during the 2012 growing season in shrub tamarisk in a desert riparian forest stand in the lower reaches of the Heihe River in Ejin Banner, Inner Mongolia of northwestern China. Generally, the variation in diurnal diameter of tamarisk was characterized by an unstable multi-peak pattern, with the cumulative stem diameter growth over the growing season following an S-shaped curve. The period from late May to early August was the main period of stem diameter growth and growth-ring formation. Among all of the hydroclimatic factors considered in this study, only groundwater depth was significantly correlated with stem diameter increment during this period. Therefore, for the dendrochronological study, the annual rings of the tamarisk can be used to reconstruct processes that determine the regional water regime, such as river runoff and fluctuations in groundwater depth. For the management of desert riparian forests, suitable groundwater depths must be maintained in the spring and summer to sustain tree health and a suitable stand structure.

Water use measurement by non-irrigated Tamarix ramosissima in arid regions of Northwest China

Tamarix ramosissima Ledeb. is a typical hardy desert plant growing in arid regions of Northwest China. Sap flow in stems of Z ramosissima plants were measured continuously to determine the diurnal and seasonal variations of sap flow and to understand the water requirements of this species and the response of sap flow to meteorological factors. This article compared the sap flow rate measured by the heat balance method with the transpiration rate measured by rapid weighing, and validated that heat balance sap flow gauges were reliable for monitoring transpiration. The influence of meteorological factors on stem sap flow during the growing season was： solar radiation 〉 vapor pressure deficit 〉 air temperature 〉 rela- tive humidity 〉 wind speed. Bidirectional sap flows occurred at night, and negative sap flow generally corresponded to high atmospheric humidity. The average error in predicted sap flow rate ranged from -0.78% to 14.00% from June to September and for transpiration the average error was 8.19%. Therefore, based on the functional equations between sap flow and meteorological factors as well as sapwood area, transpiration of an individual plant, and even the stand-level transpiration, can be estimated accurately through extrapolation.

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。

基于网络药理学和分子对接技术初探红柳治疗酒精性肝损伤的作用机制及实验验证

目的 基于网络药理学和分子对接技术,研究天然植物红柳治疗小鼠酒精性肝损伤(ALI)的作用机制。方法 使用TCMSP平台,以口服利用度≥30%和类药性≥0.18分别作为预设条件,对红柳活性化学成分进行筛选;使用GeneCards、DrugBank等数据库,筛选ALI相关靶点;通过VennDiagram软件获得交集靶点(红柳和ALI);根据疾病-活性成分-交集靶点网络数据,最终遴选出主要活性成分和致病的关键靶点进行分子对接。动物实验采用慢性酒精喂养加急性灌胃法建立C57BL/6J小鼠ALI模型。通过丙二醛(MDA)、谷草转氨酶(AST)、谷丙转氨酶(ALT)、肝脏指数、HE染色、NF-κB p65蛋白表达水平等指标验证红柳对ALI的作用机制。结果 通过网络药理学从红柳中筛选获得活性成分12个,与ALI交集靶点共151个。推测红柳的主要活性成分为槲皮素、山柰酚、异鼠李素等,通过RELA/NF-κB p65、JUN、MAPK1、AKT1等关键靶点调节脂质-动脉粥样硬化、糖尿病并发症AGE-RAGE以及流体剪切应力-动脉粥样硬化等信号通路来发挥抗ALI作用。分子对接显示红柳主要活性成分与通路关键靶点蛋白结合能量均≤-28.8696 kJ·mol^(-1)。动物实验结果显示,与模型组相比,红柳组肝脏指数、MDA、ALT、AST和NF-κB p65水平均有所下降,HE染色显示肝组织变性情况减轻。结论 本研究初步揭示了红柳可通过多化学成分、多靶点、多通路对ALI起一定的保护作用,为天然药用植物的开发和利用提供了理论参考。

多枝柽柳内生真菌Talaromyces stollii的次级代谢产物研究

通过硅胶柱色谱、Sephadex LH-20凝胶柱色谱和反相高效液相色谱等多种分离和纯化方法,从多枝柽柳内生真菌Talaromycesstollii的大米发酵培养物中分离得到了7个次级代谢产物,经ESI-MS、^(1)HNMR、^(13)CNMR和旋光比较等多种波谱技术,分别鉴定为penipyridone D(1),penipyridone E(2),penipyridone F(3),berkeleyamide C(4),chrodrimanin A(5),(S)-pestalasin A(6),peniazaphilin B(7),化合物1~4为少有的苄基吡啶酮类生物碱,首次从蓝状菌属真菌中分离得到。化合物5和6对KLF2具有一定的上调活性。

多枝柽柳叶片响应NaCl胁迫的转录组分析

在转录组层面解析盐生植物多枝柽柳响应盐胁迫的分子机制,为进一步挖掘耐盐关键基因提供参考。用200 mmol/L NaCl处理多枝柽柳0 h、48 h、168 h后,采集叶片进行转录组测序,分析差异表达基因(DEGs)并进行qRT-PCR验证。转录组测序原始数据拼接出Unigenes 105702个,同时在KEGG、KOG、NR和SwissProt 4大功能数据库中检索到注释的Unigenes为27670个。NaCl胁迫处理48 h后,多枝柽柳叶片中6374个基因的表达水平上调,5380个基因的表达水平下调;NaCl胁迫处理168 h后,叶片中有3837个基因的表达水平上调,7808个基因的表达水平下调。根据注释到KEGG通路中的DEGs,筛选获得8个表达差异极其显著的DEGs,主要编码WRKY和bZIP家族转录因子。此外,由KEGG通路分析可知,MAPK信号转导途径可能参与多枝柽柳生长发育及其对NaCl胁迫的应答反应。本研究通过测定和解析在高盐胁迫下多枝柽柳叶片转录组信息,揭示了盐胁迫激活MAPK信号转导途径以及WRKY、MYB和bZIP等转录因子参与耐盐调控过程,为进一步研究多枝柽柳耐盐分子机制奠定了基础。

Water use characteristics of different pioneer shrubs at different ages in western Chinese Loess Plateau:Evidence from δ^(2)H offset correction

Caragana korshinskii Kom.and Tamarix ramosissima Ledeb.are pioneer shrubs for water and soil conservation,and for windbreak and sand fixation in arid and semi-arid areas.Understanding the water use characteristics of different pioneer shrubs at different ages is of great importance for their survival when extreme rainfall occurs.In recent years,the stable isotope tracing technique has been used in exploring the water use strategies of plants.However,the widespreadδ^(2)H offsets of stem water from its potential sources result in conflicting interpretations of water utilization of plants in arid and semi-arid areas.In this study,we used three sets of hydrogen and oxygen stable isotope data(δ^(2)H andδ^(18)O,correctedδ^(2)H_c1 based on SW-excess andδ^(18)O,and correctedδ^(2)H_c2 based on−8.1‰andδ^(18)O)as inputs for the MixSIAR model to explore the water use characteristics of C.korshinskii and T.ramosissima at different ages and in response to rainfall.The results showed thatδ^(2)H_c1 andδ^(18)O have the best performance,and the contribution rate of deep soil water was underestimated because ofδ^(2)H offset.During the dry periods,C.korshinskii and T.ramosissima at different ages both obtained mostly water from deeper soil layers.After rainfall,the proportions of surface(0-10 cm)and shallow(10-40 cm)soil water for C.korshinskii and T.ramosissima at different ages both increased.Nevertheless,there were different response mechanisms of these two plants for rainfall.In addition,C.korshinskii absorbed various potential water sources,while T.ramosissima only used deep water.These flexible water use characteristics of C.korshinskii and T.ramosissima might facilitate the coexistence of plants once extreme rainfall occurs.Thus,reasonable allocation of different plants may be a good vegetation restoration program in western Chinese Loess Plateau.

NaCl处理对多枝柽柳(Tamarix ramosissima)生长及生理的影响

以1年生多枝柽柳(Tamarix ramosissima)幼株为材料,采用盆栽试验研究不同浓度(0、50、100、200、400mmol·L–1)NaCl处理对多枝柽柳生长状况及叶片过氧化氢(H2O2)、丙二醛(MDA)含量,超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)、抗坏血酸过氧化物酶(APX)活性,水势,可溶性糖和脯氨酸含量的影响。结果表明:低浓度(≤100mmol·L-1)的NaCl处理对多枝柽柳株高、冠幅面积、分枝数和叶、枝干重具有促进效应;高浓度(≥200mmol·L-1)的NaCl处理抑制了多枝柽柳生长,对侧根干重的抑制作用大于对冠幅面积、分枝数、叶干重、枝干重及株高的抑制。H2O2和MDA含量在低浓度(≤100mmol·L-1)NaCl处理下较对照未出现积累现象,随NaCl浓度升高(≥200mmol·L-1)二者含量较对照出现显著积累。低浓度(≤100mmol·L-1)NaCl处理下,多枝柽柳叶片SOD、POD、CAT和APX活性较对照均有所提高,高浓度的NaCl处理下SOD和POD活性开始降低。多枝柽柳叶片水势随NaCl处理浓度升高呈显著下降趋势。低浓度(≤100mmol·L-1)NaCl处理下脯氨酸和可溶性糖含量较对照呈上升趋势。

塔里木河上游胡杨(Populus euphratica、柽柳(Tamarix ramosissima)水分来源的稳定同位素示踪

通过分析塔里木河上游胡杨(Populus euphratica)、柽柳(Tamarix ramosissima)茎干水和各潜在水源(河水、土壤水、地下水)的δD、δ^(18)O同位素组成,应用多水源混合模型(IsoSource模型)研究了胡杨、柽柳的水分来源和对各潜在水源的利用比例。结果表明:0~100cm土壤水受蒸发影响大,土壤水δ^(18)O值偏大;100~300cm土壤水和地下水δ^(18)O值偏小且各点不存在显著差异。柽柳茎干水的δ^(18)O值小于胡杨,且均随河岸距离增加而减小;在河岸,胡杨最多能利用14.2%的河水,柽柳对河水的利用比例最大达到35.3%,二者对浅层0~100cm土壤水的利用比例较高;远离河岸,胡杨主要利用大于120cm的土壤水和地下水,对地下水的利用比例40%~50%,柽柳以地下水作为其主要水源,最大利用比例达到94.5%。胡杨生长需要适宜的地下水埋深条件(350~420cm),柽柳在浅地下水埋深和大于450cm的深地下水埋深条件下均能良好生长,对不同水分条件的适应能力优于胡杨。

极端干旱区多枝柽柳叶片功能性状及其与土壤理化因子的关系

叶片是植物获取资源的重要器官,研究其功能性状与环境因子的关系,有助于更好地了解植物对环境要素变化的生态适应性。以塔里木盆地北缘不同生境下(绿洲、过渡带、荒漠)典型荒漠植物多枝柽柳(Tamarix ramosissima)为研究对象,分析其叶片结构和生理性状在不同生境间的差异,建立叶片性状与土壤理化因子的相关关系,解析荒漠植物的生态适应性并揭示影响荒漠植物叶片功能性状的关键环境因子。结果表明:(1)多枝柽柳叶片功能性状具有不同程度的变异,其中叶片面积变异幅度最大(40%),比叶面积、可溶性蛋白含量等变异幅度最小(均为15%)。(2)多枝柽柳叶片厚度和叶片面积等结构性状以及叶片可溶性蛋白、脯氨酸、淀粉含量等生理性状在不同生境中均具有显著差异(P<0.05),其中可溶性蛋白、脯氨酸含量均在荒漠生境中达到最高。(3)多枝柽柳叶片部分功能性状之间存在显著的相关关系,其中叶片厚度、淀粉含量等与叶组织密度呈显著负相关关系(P<0.05),而叶片厚度与淀粉含量之间、可溶性糖含量与非结构性碳水化合物含量之间均呈极显著正相关关系(P<0.01)。(4)通过RDA排序分析发现,土壤速效磷含量、土壤含水量、pH、容重等土壤环境因子影响较大,对多枝柽柳叶片功能性状有较好的解释。研究表明多枝柽柳通过叶片功能性状变化以及性状之间协同-权衡的生态对策来适应极端干旱环境,土壤水分和速效磷含量是影响其叶片功能性状最关键的土壤环境因子,研究可为极端干旱区荒漠植被的科学管理、保护和恢复提供理论依据。

四翅滨藜和多枝柽柳对土壤干旱的响应差异

在干旱区防护林建设中,选择抗逆性和适应力强的植物树种是关键。通过模拟不同干旱梯度的盆栽控水试验来比较塔里木盆地引种植物四翅滨藜和乡土植物多枝柽柳对干旱胁迫生态适应性差异。结果表明:(1)随着干旱程度增加,四翅滨藜和多枝柽柳叶片含水量均逐渐降低,保水力、脯氨酸含量、相对电导率逐渐增大。四翅滨藜和多枝柽柳的可溶性糖含量、丙二醛含量分别在轻度、重度干旱下达最大值,多枝柽柳的增幅更大。(2)四翅滨藜和多枝柽柳POD活性逐渐增大,重度干旱下,多枝柽柳较对照增加的百分比约为四翅滨藜的3倍;在中度干旱下SOD活性最大,多枝柽柳较对照增加的百分比约为四翅滨藜的5倍。多枝柽柳2种酶活性变化均大于四翅滨藜。(3)四翅滨藜和多枝柽柳叶绿素含量均为:轻度干旱>对照>中度干旱>重度干旱,多枝柽柳的净光合速率、蒸腾速率、气孔导度和胞间二氧化碳浓度均逐渐降低,轻度干旱对四翅滨藜叶绿素和光合能力有略微促进作用。(4)相关性和主成分分析结果显示,干旱胁迫下多枝柽柳各性状间的联系更紧密,四翅滨藜不易改变性状和性状之间的联系,相对保守。四翅滨藜受到干旱胁迫的影响较小,其干旱适应性略强于多枝柽柳。

额济纳绿洲不同土壤水盐条件多枝柽柳对胡杨种群分布的影响

【目的】生态输水工程实施后,胡杨种群得到了一定的恢复,但恢复效果远不如与其生态位高度重叠的多枝柽柳显著。本研究拟探讨不同土壤水盐环境下,胡杨种群的适应优势是否受到多枝柽柳伴生的影响,以期为胡杨林的保护管理和绿洲生态输水方案制定提供科学参考。【方法】本研究以西北干旱区河岸林群落的关键建群种胡杨和多枝柽柳为研究对象,选取目前野外常见的两种土壤水盐生境(相对高水高盐和水盐适中),分析两个物种种群空间分布及其与水盐的相互关系。【结果】(1)在相对高水高盐的环境中,胡杨种群呈现衰退趋势,幼龄木极少且更新受限,而多枝柽柳则表现稳定状态。水盐适中的环境中,胡杨种群结构稳定,各龄级相差不大,多枝柽柳种群则表现为增长趋势。(2)不同土壤水盐条件下,两个物种主要以聚集分布为主以抵抗不良环境的胁迫,胡杨幼苗的生长还会受多枝柽柳伴生抑制。(3)不同的土壤水盐条件会造成两物种多度的差异。多枝柽柳与胡杨种群个体数的比值均与盐分呈正相关,但在盐分含量不高时,随水分的增加,多枝柽柳种群个体数量减少,胡杨种群个体数量则增多。【结论】本研究结果进一步验证:除环境过滤作用外,多枝柽柳的竞争也是目前胡杨在演替过程中表现出衰退现象的一个重要因素。在高盐环境中多枝柽柳会逐渐取代胡杨,水分条件的改善可以减缓这种趋势的发生。

干旱胁迫下丛枝菌根真菌对疏叶骆驼刺和多枝柽柳生长及生理的影响

多枝柽柳(Tamarix ramosissima)与疏叶骆驼刺(Alhagi sparsifolia)是塔里木河下游优势种,也是重要的丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)共生植物,二者常相伴而生且均受水分严重限制。研究采用盆栽试验法,以疏叶骆驼刺和多枝柽柳幼苗为试验材料,设定正常水分[土壤相对含水量(70±5)%,D0]、中度水分胁迫[土壤相对含水量(40±5)%,D1]和重度水分胁迫[土壤相对含水量(20±5)%,D2]3个水分梯度,设置接种(AMF+)和不接种(AMF-)2种处理,以及供体植物疏叶骆驼刺和受体植物多枝柽柳之间2种菌丝传递距离(长菌丝传递距离30 cm,L;短菌丝传递距离15 cm,S),探究了干旱胁迫下丛枝菌根真菌菌丝传递距离对2种不同生活型的植物生长和生理的影响。结果表明,(1)供体植物接种AMF后在供、受体间形成丛枝菌根菌丝网络(arbuscular mycorrhizal networks,AMNs),其中与正常水分(D0)处理下的侵染率相比,重度水分(D2)处理下长距离处理受体侵染率的降幅为73.22%。(2)在中度水分处理下,AMF对长、短距离处理受体均有促进作用,而在重度水分处理下对长距离处理受体株高、基径相对增长率和生物量无促进作用。(3)各水分处理下AMF对受体植物根系生长指标具有显著促进作用(P<0.05),且S处理优于L处理,但在重度水分及长距离处理下的受体表现出显著较低的水平。(4)在中度水分处理下,AMF对长、短距离处理受体抗氧化酶活性、渗透调节物质含量、叶绿素含量和叶片相对含水量均有促进作用,且不同距离处理间差异不显著,而在重度水分处理下对长距离处理幼苗无促进作用。因此,在正常水分和中度水分处理下,接种AMF可显著促进长距离端受体植物的表观生长、生物量积累、抗氧化酶活性、渗透调节物质和叶绿素的含量,提高受体植物的抗旱性,在重度水分胁迫下AMF对长距离端受体植物的促进作用不显著。

胡杨(Populus euphratica)与柽柳(Tamarix ramosissima)径向生长特征对比

基于对额济纳旗胡杨(Populus euphratica)和柽柳(Tamarix ramosissima)生长季树干的径向生长变化监测,以及气温、空气相对湿度和地下水位等环境因子的同步监测,利用突变检验和相关分析方法,对两树种日-季节尺度径向生长时间节点、阶段等特征及其环境因子响应模式进行了对比研究。结果显示:在两树种径向生长变化特征方面,日尺度上,胡杨每日径向生长最大值点出现和结束时间均比柽柳早3h左右;季节尺度上,胡杨进入快速生长阶段的时间迟于柽柳,并且比柽柳结束要早,持续时间短于柽柳。在环境响应机制方面,胡杨日收缩极值(eMDV)、日膨胀极值(iMDV)和日净生长量(ΔR)阶段变化平均值为柽柳的3倍以上,变化幅度也相对较大;两树种上述径向生长参数与气温和地下水埋深等因子日-季节尺度的响应模式基本一致,快速生长期的地下水位变化影响更为显著,尤其对于柽柳。研究结果对于荒漠河岸林可持续发展及内陆河流域水资源管理具有重要意义。

盐胁迫对AMF介导下两种荒漠植物生长和生理特性的影响

本试验以疏叶骆驼刺(Alhagi sparsifolia)和多枝柽柳(Tamarix ramosissima)分别为供、受体植物,探讨在盐胁迫下不同丛枝菌根真菌(Arbuscular mycorrhizal fungi, AMF)菌丝传递距离处理对其幼苗的影响。研究通过盆栽试验,对不同盐浓度(0,0.4%和0.8%)及丛菌丝传递距离(15 cm和30 cm)处理下供、受体植物的AMF侵染率、株高基径、叶绿素荧光参数、抗氧化酶活性和渗透调节物质含量进行测定。结果表明:在受体植物中,AMF对S1水平下L1和L2处理的Fo, Fm和Fv/Fm值、MDA和渗透调节物质含量及抗氧化酶活性均具有明显的促进作用,且不同距离受体间差异不显著,但对S2水平L2处理下幼苗的生长和生理指标无促进作用。综上所述,AMF在低盐胁迫长距离下能通过显著提高叶绿素荧光参数、抗氧化和渗透调节能力缓解盐胁迫对受体植物的伤害;但高盐胁迫下,长距离不利于菌根定殖和植物生长,导致AMF无法对受体植物产生促进作用。

Influence of moisture on the growth and biomass allocation in Haloxylon ammodendron and Tamarix ramosissima seedlings in the shelterbelt along the Tarim Desert Highway, Xinjiang, China

The authors studied the effects using three different levels of irrigation on the growth and biomass allocation in H. ammodendron and T. ramosissima seedlings in the shelterbelt along the Tarim Desert Highway. The three irrigation amounts were 35 (CK), 24.5 (treatment 1), and 14 (treatment 2) kg·ind. plant-1·once-1, respectively. The results show that (1) the vertical depth of the two seedlings’ root increased with lower levels of irrigation showing that the two species adapted to decreased irrigation by root elongation in the hinterland of the Taklimakan Desert, and the vertical root depth of H. ammodendron under treatment 2 was notably higher than CK. (2) Compared with CK, the belowground biomass of treatment 1 and 2 both showed a significant increase as follows: H. ammodendron seedlings in- creased by 14.51% and 37.03% under treatment 1 and 2, respectively, while T. ramosissima seedlings increased by 68.19% and 25.78% under treatment 1 and 2, respectively. This means that H. ammoden- dron seedlings were more adapted to the conditions in treatment 2 while T. ramosissima seedlings were better adapted to treatment 1 conditions. (3) When compared with CK, the fine root bomass of these two species all exhibited some increase under both treatments, and ANOVA analysis showed that the biomass of deep layer root of the two species under treatment 2 was notably higher than CK and treatment 1. This should help seedlings to more effectively absorb soil water from deep layers during dry conditions. (4) The root-shoot ratio was different for these two species. For H. ammodendron seed- lings, the root-shoot ratio was less than 1, while for T. ramosissim seedlings it was larger than 1. The root-shoot ratio of H. ammodendron seedlings increased with decreasing levels of irrigation, and that of T. ramosissim seedlings also increased under treatment 2. (5) With decreasing levels of irrigation, due to the difference of species, the growth variation of aboveground indexes was also different, while compared with CK, it was not significant.

Physiological response of Tamarix ramosissima under water stress along the lower reaches of Tarim River

Tamarix ramosissima is one of the con- structive species growing on both sides of Tarim River which is favorable to constituting a natural bar- rier containing local deserts and protecting the oasis. By analyzing characteristics of the main physiological indexes, such as chlorophyll, soluble sugar, proline (Pro), malondialdehyde (MDA), superoxide dismu- tase (SOD), peroxidase (POD), indole-3-acetic acid (IAA), C3-gibberellins (GA3) and abscisic acid (ABA), at different sections with different water tables in the lower reaches of Tarim River, it has been found that these physiological indexes have close correlations with water tables. In addition, the rational ecological, coercing and critical water tables of T. ramosissima are 2-4 m, 6 m and 10 m, respectively, which pro- vides an important theoretical basis for the ecological conservation of extremely arid regions.

Impacts of predictor variables and species models on simulating Tamarix ramosissima distribution in Tarim Basin, northwestern China

Aims Preserving and restoring Tamarix ramosissima is urgently required in the Tarim Basin,Northwest China.Using species distribution models to predict the biogeographical distribution of species is regularly used in conservation and other management activities.However,the uncertainty in the data and models inevitably reduces their prediction power.The major purpose of this study is to assess the impacts of predictor variables and species distribution models on simulating T.ramosissima distribution,to explore the relationships between predictor variables and species distribution models and to model the potential distribution of T.ramosissima in this basin.Methods Three models—the generalized linear model(GLM),classification and regression tree(CART)and Random Forests—were selected and were processed on the BIOMOD platform.The presence/absence data of T.ramosissima in the Tarim Basin,which were calculated from vegetation maps,were used as response variables.Climate,soil and digital elevation model(DEM)data variables were divided into four datasets and then used as predictors.The four datasets were(i)climate variables,(ii)soil,climate and DEM variables,(iii)principal component analysis(PCA)-based climate variables and(iv)PCA-based soil,climate and DEM variables.Important Findings The results indicate that predictive variables for species distribution models should be chosen carefully,because too many predictors can reduce the prediction power.The effectiveness of using PCA to reduce the correlation among predictors and enhance the modelling power depends on the chosen predictor variables and models.Our results implied that it is better to reduce the correlating predictors before model processing.The Random Forests model was more precise than the GLM and CART models.The best model for T.ramosissima was the Random Forests model with climate predictors alone.Soil variables considered in this study could not significantly improve the model’s prediction accuracy for T.ramosissima.The potential distribution area of T.ramosissima in the Tarim Basin is;3.57310^(4) km^(2),which has the potential to mitigate global warming and produce bioenergy through restoring T.ramosissima in the Tarim Basin.