Vitality variation and population structure of a riparian forest in the lower reaches of the Tarim River,NW China

Since 2000, the Chinese government has implemented emergency water diversion measures to restore the damaged riparian forest ecosystem with dominant tree species Euphrat poplar(Populus euphratica Oliv.)at the lower reaches of the Tarim River. In the present study, comparative analysis of variations in the vitality of P. euphratica trees were made using 2005 and 2010 data to illustrate the revitalization process of riparian forest. Poplar trees within 300 m of the riverbed were positively revitalized, while the vitality of trees farther than 300 m from the river decreased. Population structure was studied to demonstrate the development of poplar community. In the first belt, the class structure for the diameter at breast height(DBH) of P. euphratica fit a logistic model, and the 2nd, 3rd and 4th belt curve fittings were close to a Gaussian model; in other plots they were bimodal. Cluster analysis of the composition of the DBH class of poplar trees demonstrated that those within 16–36 cm DBH were the most abundant(58.49% of total) in study area, under 16 cm of DBH were second(31.36%), and trees >40 cm DBH were the least abundant(10.15%). More than 80% of the trees were young and medium-sized, which means that the poplar forest community in the vicinity of the lower Tarim River is at a stable developmental stage. The abundance of juvenile trees of P. euphratica in the first and second measuring belts was 12.13% in 2005 and increased to 25.52% in 2010, which means that the emergency water transfer had a positive impact on the generation of young P. euphratica trees in the vicinity of the river.

Changes in groundwater levels and the response of natural vegetation to transfer of water to the lower reaches of the Tarim River

Restoration and reconstruction of the degraded Tarim River ecosystem is an important challenge. A goal of an ecological water conveyance project is to protect and restore the natural vegetation in the lower reaches of Tadm River by transferring water from Bosten Lake, through the river channel, to the lower reaches. This study describes the changes in groundwater depth during the water transfer and the respondence of riparian vegetation to alterations in groundwater levels. The results indicate that groundwater depth along the Tarim River channel has a significant spatial-temporal component. Groundwater levels closest to the river channel show the most immediate and pronounced changes as a response to water transfer while those further away respond more slowly, although the observed change appears to be longer in duration. With a rise in the groundwater level, natural vegetation responded with higher growth rates, biomass and biodiversity. These favorable changes show that it is feasible to protect and restore the degraded natural vegetation by raising the groundwater depth. Plant communities are likely to reflect the hysteresis phenomenon, requiting higher water levels to initiate and stimulate desired growth than what may be needed to maintain the plant community. Because different species have different ecologies, including different root depths and densities and water needs, their response to increasing water availability will be spatially and temporally heterogenous. The response of vegetation is also influenced by microtopography and watering style. This paper discusses strategies for the protection and restoration of the degraded vegetation in the lower reaches of the Tarim River and provides information to complement ongoing theoretical research into ecological restoration in add or semi-arid ecosystems.

Evaluation of oasis stability in the lower reaches of the Tarim River

Oasis stability in the lower reaches of the Tarim River was assessed at the landscape scale（including changes in landscape pattern and land use in the oasis） and at the regional scale（including the cold-island effect and NDVI of the oasis） based on the methods of landscape ecology,GIS and Remote Sensing（RS）.Thematic Mapping（TM） remote sensing images from 1990,2000 and 2009 were employed along with the related meteorological and hydrological data pertaining to the reclamation area of the oasis in the lower reaches of the Tarim River.The results indicated that landscape heterogeneity and oasis complexity increased between 1990 and 2000.The comprehensive index of the degree of land use,the average index of the cold-island effect,NDVI value and oasis stability all decreased.However,the change trends in the indices referred to above were opposite between 2000 and 2009,and oasis stability was enhanced to some extent.

Evapotranspiration and its main controlling mechanism over the desert riparian forests in the lower Tarim River Basin

Evapotranspiration(ET) and its controlling mechanism over the desert riparian forests in arid regions are the important scientific basis for the water resources managements of the lower reaches of the inland rivers of China. Nearly three years of continuous measurements of surface ET, soil water content at different depths and groundwater table over a typical Tamarix spp. stand and a typical Populus euphratica stand were conducted in the lower reach of the Tarim River. The ET seasonal trends in the growing season were controlled by plant phenology, and ET in non-growing season was weak. The diurnal variations of ET resulting from the comprehensive effects of all atmospheric factors were significantly related with reference ET. The spatial pattern of ET was determined by vegetation LAI, more vegetation coverage, more ET amount. Groundwater is the water source of surface ET, and the soil water in shallow layers hardly took part in the water exchange in the groundwatersoil-plant-air system. The temporal processes of ET over the Tamarix stand and the Populus stand were similar, but the water consumption of the well-grown Populus euphratica was higher than that of the well-grown Tamarix spp. Further analysis indicates that plant transpiration accounts for most of the surface ET, with soil evaporation weak and negligible; groundwater table is a crucial factor influencing ET over the desert riparian forests, groundwater influences the processes and amounts of ET by controlling the growth and spatial distribution of desert riparian forests; quantifying the water stress of desert riparian forests using groundwater table is more appropriate, rather than soil water content. Based on the understanding of ET and water movements in the groundwater-soil-plant-air system, a generalized framework expressing the water cycling and its key controlling mechanism in the lower reaches of the inland rivers of China is described, and a simple model to estimate water requirements of the desert riparian forests is presented.

A quantitative assessment on groundwater salinization in the Tarim River lower reaches,Northwest China

Based on monitored data from 840 samples, we assessed the spatial and temporal variability of groundwater salinization in the Tarim River lower reaches combining classical statistics and geostatistics. Results show that total dissolved solids （TDS） is significantly correlated with other related ions, such as Na＋, Mg2＋, Ca2-, C1- and K＋. TDS and underground water level have characteristics of spatial autocorrelation, both of which present the isotropic characteristic and con- form to the spherical model in each year from 2001-2009. TDS is basically greater than 1 g/L but less than 2 g/L in the Tarim River lower reaches, which indicates that salt stagnation pollution is more serious. The most serious salinization （3 g/L 〈 TDS _〈 35 g/L） contaminated area is mainly in the middle and lower part of the study area.

塔里木河下游植被覆盖度图谱分析

基于GEE(google earth engine)平台结合像元二分模型估算了植被覆盖度,并以此构建了地学信息图谱体系。应用该体系对塔里木河下游进行植被覆盖度时空变化特征分析。得出以下结论:塔里木河下游植被覆盖结构以极低植被覆盖为主,占研究区总面积的80%以上;植被覆盖变化图谱中最明显的是极低植被覆盖与其他植被覆盖类型之间的转换,其次是低植被覆盖与其他植被覆盖类型之间的转换;植被覆盖涨落势图谱中涨势最大的分别是低植被覆盖和中植被覆盖,落势最大的是极低植被覆盖;植被覆盖变化模式图谱以稳定不变型为主,后期变化型占比大于前期变化型。整体来看,2000—2022年塔里木河下游生态环境逐渐改善,植被变化情况越来越好。

间歇性输水条件下塔里木河下游地下水时空变化模拟

为确定适宜的输水策略以实现塔里木河下游地下水位的快速抬升,提高生态系统的恢复力,运用GMS软件构建了塔里木河下游地下水动态模拟模型,设计单阶段、双阶段和多阶段输水情景模拟预测了地下水对不同输水情景的时空响应特征。结果表明:制定输水策略时应保证年输水量大于有效水量,当输水总量一定时,延长输水时间、扩大输水间隔有助于地下水位的快速抬升;最佳输水策略是以1月和3—11月为输水期分两个阶段输水4 500万m^(3);地下水埋深和水位变化量沿河道对称分布,地下水埋深与距河道两侧距离成正比,地下水位变化量和抬升量与时间成反比。

塔里木河下游输水模式改进研究——以英苏断面为例

[目的]针对塔里木河下游现状间歇性河道输水中存在补给不均衡,无效蒸发过大,补水范围有限等问题,从空间和时间维度上提出生育期汊河输水、非生育期输水的方式,研究输水模式的改进对地下水位的影响,进一步完善轮渗灌溉生态修复体系,为塔里木河下游生态恢复提供理论依据。[方法]以塔里木河下游英苏监测断面为例,以2012—2021年10次生态输水期间地下水埋深监测资料为依据,运用Modflow模型建立英苏断面地下水剖面二维流运动的数值模拟,并分析英苏断面10次间歇性生态输水的响应过程,并预测和分析了生育期汊河、非生育期以及非生育期汊河输水的地下水位演变及水量变化的过程。[结果](1)生育期汊河、非生育期、非生育期汊河方案下人工汊河两侧地下水位较现状输水分别抬升了2.5,0.7,3.2 m。(2)3种改进方案较现状输水研究区小于8 m的埋深面积分别增加了10.89%,19.33%,26.17%。(3)地下水存储量较现状输水分别增加了10.97%,11.88%,14.39%。[结论]非生育期汊河输水结合了生育期汊河和非生育期输水两者的优势,提高了下泄水量的利用率,解决了现状主河道输水模式下河间地下水位难以恢复的问题,为河间地块生态系统的恢复并使其成为下游生物多样性的安全带创造了条件。

塔里木河下游植被非生长季火灾风险等级遥感评估

以塔里木河下游地区为例,利用已知火灾发生点前后时段卫星遥感数据,计算干枯燃料指数(dead fuel index,DFI)和2种燃烧指数,即归一化燃烧指数(normalized burn ratio,NBR)和燃烧面积指数(burn area index,BAI),分析干枯燃料指数和燃烧指数的相关性,并评估研究区的火灾风险等级。结果表明:燃烧指数可以较为准确地得到过火区域的位置;干枯燃料指数(DFI)与燃烧指数存在一定的相关性,R分别为0.53(NBR)、0.51(BAI);2021年2月发生的火灾处于高风险区域,说明干枯燃料指数可以作为火灾风险等级评估指标,并利用2020—2021年秋冬季分析,得到火灾风险等级图。

Analysis on water potential of Populus euphratica oliv and its meaning in the lower reaches of Tarim River,Xinjiang

Combined with materials measured on leaves water potential of Populus euphratica oliv in the process of ecological water delivery in the lower reaches of Tarim River, the influence of ground-water depths and soil salinity on leaves water potential of P. euphratica was analyzed. We found that there was evident negative correlation between the leaves water potential of P. euphratica and ground-water depths. The deeper the ground-water depths were, the lower the leaves water potential of P. euphratica was, the more serious drought stress P. euphratica suffered from. Besides, there was evident negative correlation between the soil salinity and the leaves water potential of P. euphratica. The bigger the soil salinity was, the lower the leaves water potential of P euphratica was, the more serious drought stress was indicated from which P. euphratica suffered. For sections rather distant for Daxihaizi Reservoir as well as for those places of wells rather distant from the river course, ground-water depths and the soil salinity were high; the leaves water potential of P. euphratica was low. The leaves water potential of P. euphratica can reflect the degree at which P. euphratica suffers from drought and salt stress, and has an important reference meaning in analyzing proper ground-water depths for the survival and growth of P. euphratic in the lower reaches of Tarim River.

塔里木河下游地下水及土壤对胡杨林长势的影响

胡杨(Populus euphratica)是塔里木河重要的物种之一,也是抑制荒漠化进程的“绿色守卫者”。采用样方调查结合取样测试的方法,获取了塔里木河下游恰拉水库至英苏段16个样方的林分因子及水土理化参数。利用单因素方差分析、聚类分级、相关分析的方法研究了地下水及土壤因子对胡杨长势的影响。结果表明:塔里木河下游不同长势胡杨的林分因子差异显著,长势良好的胡杨平均胸径22.51 cm、树高7.26 m、冠幅3.44 m,均明显高于长势极差、较差的样方。受塔里木河影响,林分因子随河道距离增加呈波浪递减的趋势。古河道附近的胡杨通常拥有较大的树高及冠幅,但长势较差,若不加以治理将很快枯萎。地下水理化性质对胡杨长势的影响均显著高于土壤化学性质,其中地下水埋深、距河道的距离对胡杨长势的影响最为显著,相关系数分别为0.922、0.898,80 cm<h≤120 cm土层土壤全盐量对胡杨长势的影响次之,相关系数为0.871。

Corridor effect of the spatial changes of landscape patterns in arid areas:A case study of the river corridor areas in the middle and lower reaches of Tarim River

在 Tarim Riverare 的中间、更低的活动范围的河走廊区域在 Ruoqiang 从 Qara 水库 inYuli 县沿着河节由传统的绿走廊统治了到泰泰马·莱克县，它在 Tarim 河分水岭在社会、经济的发展起一个重要作用与一极其重要的生态的功能。对水路垂直的缓冲区地区从水路在 5-kminterval 开始沿着两个河边被定义(10 km 更宽) 用缓冲区地区分析的方法。每个缓冲区地区的风景模式索引被计算，并且主要风景模式的索引被分析以便在风景和补丁层次上揭示放射的效果和河走廊的特征。放射的宽度通常是在学习区域的 30 km 的结果表演，和罐头直到在潜水艇的 50-70 km -- 区域 FG1 因为学习区域位于二排水盆，与在他们之间的一个生态的空隙的地区。树林和沼泽地的 Thelandscapes 通常在 10 km 缓冲区地区以内被散布(它意味着缓冲区地区是离开水路的 5 km；一样此后) 沿着两个河边。而且，缓冲区地区越靠近到水路，补丁密度和最大的补丁索引是越多 higher。在为学习区域的生态、环境的新生，河走廊的生态的效果的程度必须充分被考虑，并且工程必须科学地并且讲道理地被计划并且设计。

Assessment of water-recharging based on ecological features of riparian forest in the lower reaches of Tarim River

被 mesophytes 种类主要统治的河边的森林的出现和发展与表面水仔细联系。因为到过去的 5 十年年里的 Tarim 河的更低的活动范围没有水分泌物，河边的森林严重地降级。在 2002 和 2003 的 Yingsu， Argan 和 Luobuzhuang 的监视数据的基于的在分析，效果再装 ofwater 被讨论。再装水的工程忽视事实控制在露面，而是对植被的地下水影响的焦点上开拓殖民地于的 Populus euphratica 的过程，这正在泛滥。泛滥的控制背离河边的森林开发的固有的法律，河边的森林的自然新生因此被检查。地下水上的河边的植物的反应范围高举极其狭窄、很河边的社区没被优化。因为 theirphysio 生态的特征被忽略，主导的种类的幼苗都没在充满区域被发现。然而，在溪流的附近的植被变化仅仅在浅地下水上反映 mesophytes 种类的需求为河边的植物的幼苗建立提供合适的产地的 water-re-chargingfails。再装 presentwater 计划是困难的认识到植被恢复。

地下水数值模拟中的参数灵敏度分析

将局部灵敏度分析和全局灵敏度分析引入地下水数值模型的参数灵敏度分析中,并以塔里木河下游为例,选取含水层渗透系数、给水度、河床沉积物渗透特性系数及模型输入项的河流水位进行地下水数值模拟中的参数灵敏度分析.分析结果表明,河流水位对地下水数值模型的影响最为显著,而其他参数的影响则相对较小,全局灵敏度分析计算出的参数总灵敏度较小.这说明地下水数值模型比较稳定,可以用于模拟塔里木河下游地下水水位变化情况.

干旱荒漠区草地植物群落地上生物量时空分布对地下水的响应

分析了塔里木河下游以芦苇为优势种群的草地植物群落地上生物量时空分布特征及其对物种多样性和地下水的响应。结果表明,1)在时间上,2007年群落地上生物量最高,达741.75g/m2;在空间上,群落地上生物量随垂直河道距离的增加显著减少。2)物种多样性与群落地上生物量呈显著正相关。3)地上生物量在地下水埋深<3m时较高,且地上生物量对地下水中的Mg-Cl盐含量最为敏感,群落耐盐上限在5.0g/L左右。

塔里木河下游漫溢干扰频次和持续时间对河岸植被和土壤的影响差异

在塔里木河下游选取不同频次和持续时间的漫溢样地进行地表植被和表层土壤调查,以分析漫溢干扰的频次和持续时间差异对于植物群落特征和土壤性质的影响。结果表明,1)漫溢干扰使得一年生草本和多年生草本在植物群落中的重要值有所增加,其中多年生草本在2个漫溢频次样地和3个漫溢持续时间样地中占据优势,说明漫溢干扰后多年生草本逐渐替代乔灌木成为主要的群落组成物种。2)漫溢频次样地中以"多年多次"漫溢样地的多样性指数值最大,其Simpson指数,Shannon-Wiener指数和Margalef指数与对照样地相比均具有极显著差异,指数值分别为:0.523,0.979和1.023。3)漫溢持续时间样地中以"10～20d"和"20～30d"两个漫溢样地具有最大多样性指数,其中"20～30d"漫溢样地的Simpson指数和Shannon-Wiener指数及"10～20d"漫溢样地的Margalef指数与对照样地之间的差异均为极显著,指数值分别为0.451,0.777和0.863。4)漫溢干扰使得表层土壤电导率极显著减小,最小值出现在"一年1～2次"漫溢样地(1.148ms/cm)和"10～20d"漫溢样地(1.155ms/cm)。"多年多次"漫溢样地和"5～10d"漫溢样地的表层土壤有机质明显增加,有机质含量分别为11.577和8.770g/kg;其余漫溢样地的表层土壤有机质均小于对照样地。综合分析认为,频次为多年多次且持续时间在10～30d的漫溢干扰对塔里木河下游植被恢复最为有利。

3S技术在新疆塔里木河下游生态环境动态研究中的应用

塔里木河下游多年来水量不断减少 ,造成了该地区地下水位普遍下降 ,导致了植被衰败 ,风沙频繁 ,土地沙漠化普遍发生。在 3S技术支持下 ,通过 1 959年、1 983年、1 992年及1 996年航空及航天遥感信息的对比分析发现 ,下游地区生态环境的变化与自然及人为因素密切相关 。

干旱胁迫下的胡杨脯氨酸累积特点分析

以塔里木河下游的主要乔木—胡杨为研究样本 ,结合野外地下水位监测资料 ,详细分析了塔里木河下游干旱胁迫环境下胡杨体内脯氨酸的累积与变化。分析研究表明 ,胡杨体内的脯氨酸含量与塔里木河下游地下水位变化存在密切 ,脯氨酸含量随地下水位降低而增加 ,二者相关系数达 0 .913;在不同地下水位埋深条件下 ,脯氨酸含量的增加幅度有差异 ;胡杨体内的脯氨酸含量随干旱胁迫的加深而积累 ,是胡杨对干旱逆境的一种反应 。

塔里木河下游断流河道应急输水与地表植被响应

通过对塔里木河下游5个断面、30个植物样地的调查和对天然植物当年生小枝的长度、当年生小枝上胡杨的叶数、50片以上叶长、宽及叶重、芦苇的高度和叶长、宽、重量等的测试分析,揭示了塔里木河下游断流河道输水后地表植被的响应范围。研究表明,随着输水后地下水位的抬升,地表植被产生了明显变化。在横向上,芦苇的反应敏感区范围在100～150m区间;对胡杨的横向影响范围在200～250m之间;在纵向上,平均叶数从下游上段至下游下段,分别较末端断面增加57%、22 2%、9 2%;河道两岸地下水位较下游下段抬升幅度大,横向上对植被的影响范围也较下游下段宽。输水历时的长短和输水量对塔里木河下游植被恢复密切相关。