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.     

水热因子对塔里木河下游胡杨年轮指数和植被指数的影响

【目的】探索塔里木河流域树木年轮与植被遥感间的关系。【方法】借助树木年轮学的方法和技术手段,利用塔里木河下游10个采样点的胡杨样芯数据和长时间序列中国植被指数(GIMMS NDVI)数据及水热因子数据,在分析该区胡杨年轮指数和植被指数变化特征基础上,重点探讨水热因子、胡杨年轮指数及归一化植被指数(NDVI)三者间的相关性。【结果】胡杨年轮指数和年际NDVI变化在1980—2001年间均呈下降趋势,区内植被在该时间段内退化较为严重。年内NDVI变化呈单峰状,5—8月为植被生长季,1—4月和9—12月为植被非生长季。【结论】该区胡杨年轮生长受5月(P<0.01, 显著负相关)地下水埋深和6月(P<0.01,显著负相关)温度影响显著,而NDVI主要与5—7月(P<0.01, 显著负相关)和10月(P<0.01, 显著负相关)的地下水埋深及7月(P<0.01, 显著负相关)温度有关,且影响NDVI和胡杨年轮指数的主要因子是水热因子中的地下水埋深因子。胡杨年轮指数与NDVI间的相关性差,未能通过0.05水平检验。     

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

Science Bulletin - 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...     

Daily variation of carbon flux in soils of Populus euphratica forests in the middle and lower reaches of the Tarim River

In order to lucubrate the daily variation of respiration in soils of Populus euphratica forests and analyze its relationship with environmental factors in the middle and lower reaches of the Tarim River, the LI-8100 instrument of soil CO2 flux system was used to measure the parameters of soil carbon flux and air temperature 10 cm above ground surface along the profiles of Usyman, Archy River, Yengisu and Karday, and the relationships between the soil carbon flux and the soil moisture content were analyzed. The nonlinear regression analysis was carried out with the software SPSS13.0. We observed that: (1) soil respiration began to be restrained when the air temperature was up to 30℃ 10 cm above the ground surface; (2) the rates of soil respiration under the forests of Populus euphratica were significantly different at various moisture contents, the soil carbon flux was high along the Usyman profile,which has a high soil moisture content, and it was low along the profiles of Archy River, Yengisu and Karday, which has a low soil moisture content; (3) the exponential model can be used to explain the relationship between soil respiration and air temperature 10 cm above the ground surface. The average Q10 values along the profiles of Usyman, Archy River, Yengisu and Karday are 0.61, 0.16, 0.22 and 0.35 respectively, much lower than the average of the world; (4) there is a positive correlation between the soil carbon flux and the soil moisture content     

Daily variation of carbon flux in soils of Populus euphratica forests in the middle and lower reaches of the Tarim River

In order to lucubrate the daily variation of respiration in soils of Populus euphratica forests and analyze its relationship with environmental factors in the middle and lower reaches of the Tarim River, the LI-8100 instrument of soil CO2 flux system was used to measure the parameters of soil carbon flux and air temperature 10 cm above ground surface along the profiles of Usyman, Archy River, Yengisu and Karday, and the relationships between the soil carbon flux and the soil moisture content were analyzed. The nonlinear regression analysis was carried out with the software SPSS13.0. We observed that: (1) soil respiration began to be restrained when the air temperature was up to 30℃10 cm above the ground surface; (2) the rates of soil respiration under the forests of Populus euphratica were significantly different at various moisture contents, the soil carbon flux was high along the Usyman profile, which has a high soil moisture content, and it was low along the profiles of Archy River, Yengisu and Karday, which has a low soil moisture content; (3) the exponential model can be used to explain the relationship between soil respiration and air temperature 10 cm above the ground surface. The average Q10 values along the profiles of Usyman, Archy River, Yengisu and Karday are 0. 61, 0.16, 0. 22 and 0. 35 respectively, much lower than the average of the world; (4) there is a positive correlation between the soil carbon flux and the soil moisture content.     

Photosynthesis of Populus euphratica and its response to elevated CO2 concentration in an arid environment

The photosynthetic characterization of Populus euphratica and its response to the elevated carbon dioxide concentration ([CO2]) were analyzed based on its net photosynthetic rate (Pn), stomatal conductance (gs), intercellular CO2 concentration (Ci), transpiration rate (Tr), and water use efficiency (WUE) at different groundwater depths measured by a portable gas exchange system (LI-6400) in the lower reaches of the Tarim River. The results showed that the elevation of [CO2] decreased the gs, and increased the Pn, Ci and WUE of P. euphratica. However, the effects of the elevated [CO2] on gs, Pn, Ci and WUE varied considerably with groundwater depth. The response of photosynthesis to rising [CO2] was stronger at the greater groundwater depth (more than 6 m) than that at the shallower groundwater depth (less than 6 m). The critical groundwater depth required to maintain the normal survival of P. euphratica was less than 6 m. When the groundwater depth increased to more than 6 m, P. euphratica encountered moderate water stress, and the plant suffered severe water stress when the groundwater depth increased to more than 7 m.     

Assessment of waterrecharging based on ecological features of riparian forest in the lower reaches of Tarim River

The occurrence and development of riparian forests which are mainly dominated by mesophytes species relate closely with surface water. Since there is no water discharge to the lower reaches of Tarim River in past 5 decade years, the riparian forests degrade severely. Based on the analyses of the monitored data of Yingsu, Argan and Luobuzhuang in 2002 and 2003, the effect of water-recharging is discussed. The water-recharging project neglects the fact that that it is flooding that controls the process of Populus euphratica colonizing on the bare surface, but focuses on groundwater influence on vegetation. The flooding control deviates Inherent laws of riparian forests development, so the natural regeneration of riparian forests is checked. The response scope of riparian plants on groundwater uplift is extremely narrow, and most riparian communities have not been optimized. No seedlings of dominant species are found in flooding areas because their physio-ecological characteristics are ignored. The vegetation changes in vicinities of stream only reflect the demand of mesophytes species on the shallow groundwater, however, the water-recharging fails to provide suitable habitats for the seedlings establishment of riparian plants. The present water-recharging scheme is difficult to realize vegetation restoration.     

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

The occurrence and development of riparian forests which are mainly dominated by mesophytes species relate closely with surface water. Since there is no water discharge to the lower reaches of Tarim River in past 5 decade years, the riparian forests degrade severely. Based on the analyses of the monitored data of Yingsu, Argan and Luobuzhuang in 2002 and 2003, the effect of water-recharging is discussed. The water-recharging project neglects the fact that that it is flooding that controls the process of Populus euphratica colonizing on the bare surface, but focuses on groundwater influence on vegetation. The flooding control deviates Inherent laws of riparian forests development, so the natural regeneration of riparian forests is checked. The response scope of riparian plants on groundwater uplift is extremely narrow, and most riparian communities have not been optimized. No seedlings of dominant species are found in flooding areas because their physio-ecological characteristics are ignored. The vegetation changes in vicinities of stream only reflect the demand of mesophytes species on the shallow groundwater, however, the water-recharging fails to provide suitable habitats for the seedlings establishment of riparian plants. The present water-recharging scheme is difficult to realize vegetation restoration.     

Response of the accumulation of proline in the bodies of<Emphasis Type="Italic">Populus euphratica</Emphasis> to the change of groundwater level at the lower reaches of Tarim River

The content of proline in the plant bodies is closely related to the converse-succession-resistant capability of plants. Under the drought stress, the proline accumulates rapidly in the plant bodies for maintaining a certain mois-ture content and an expanding-pressure momentum in cells through the osmoregulation, thus the drought-resis- tant capability and the converse-succession-resistant ca-pability of plants are increased[1,2]. Many researches on the relationship between the proline and the…     

Physiological response of natural plants to the change of groundwater level in the lower reaches of Tarim River, Xinjiang

Based on the analysis of the three-year (2000-2002) monitoring data of the four times intermittent stream water conveyance to the lower reaches of Tarim River where the stream flow was dried up for more than 30 years and the measurement of PRO, SOD and POD in plants collected from 24 vegetation plots, it is concluded that the stream water conveyance plays an important role in lifting groundwater level. The groundwater nearby the watercourse was raised from 5～8 m in depth before the stream water conveyance to 2.5～5 m after stream water conveyance. The physiological response of Phragmites communis, Tamarix spp. And Populus euphratica to the change of groundwater is sensitive and represents a grads change obviously. The growth of the plants in the lower reaches of Tarim River is stressed by drought to various degrees. Lengthways, the drought stress exposed to the plants increases with groundwater depth from the upper sections to the lower sections; and breadthwise, the drought stress exposed to the plants is increased with the increase of distance away from the river channel of stream intermittent water releases and of the groundwater depth. Combining the field investigation and the analysis of the plots, it is considered that the stress groundwater depths for the Phragmites communis, Tamarix spp. And Populus euphratica are 3.5 m, 5 m and 4.5 m respectively.     

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

The river corridor areas in the middle and lower reaches of the Tarim River are dominated by the traditional green corridors along the river section from the Qara Reservoir in Yuli County to the Taitema Lake in Ruoqiang County, which plays an important role in the social and economic development in the Tarim River Watershed with a extremely significant ecological functions. The buffer zones perpendicular to the watercourse were defined along both riversides at a 5-km interval beginning from the watercourse (10 km wider) using the method of the buffer zone analysis. The landscape pattern indexes of each buffer zone were calculated, and the indexes of the main landscape patterns were analyzed so as to reveal the radiative effect and the characteristics of the river corridors on landscape and patch levels. The results show that the radiative width is generally 30 km in the study area, and can be up to 50-70 km in sub- region FG1 because the study area is located in two drainage basins, with an ecological interstitial zone between them. The landscapes of woodlands and wetlands are generally distributed within the 10 km buffer zone (it means that the buffer zone is 5 km away from the watercourse; the same hereafter) along both riversides. Moreover, the closer the buffer zone is to the watercourse, the higher the patch density and the largest patch index are. In the ecological and environmental regeneration for the study area, the extent of ecological effect of the river corridors must be fully considered, and the projects must be scientifically and rationally planned and designed.     

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

Tarim River within the boundaries of Xinjiang is the longest inland river in China and its overall length is 2300 km (the main stream is 1321 km). Because of the increasing population in the region and large-scale ex- ploitation of water and soil resource…     

水温变化影响下金沙江下游典型鱼类繁殖期研究

为分析金沙江向家坝建成前后坝下江段水温变化对典型鱼类繁殖期的影响,基于实测数据分析研究了金沙江下游年际水温变化趋势与近年水温变幅,进而将14种典型鱼类历史产卵期适宜水温范围投影至现阶段水温历时变化曲线,得出各典型鱼类的繁殖期变化情况,并通过提出时间重叠度指标定量评价了水温变化对鱼类的影响。结果表明,建坝前金沙江下游水体升温期为2—6月,水温年内变化范围为11.8～23.2℃;建坝后则推迟至4—7月,水温年内变化范围为14.0～23.1℃,水温变幅趋于减小;在建坝后的水温条件下,金沙江下游典型鱼类主要繁殖时段可能由3月上旬—7月下旬后移至3月下旬—8月上旬。     

Effects of water treatments on the activation of soil seed banks - A case study on the lower reaches of the Tarim River

Evaluation of seedling emergence is a common method used to investigate the vegetation restoration potential of soil seed banks. Previous studies have primarily been conducted in the laboratory using a single water treatment. However, when this method is used, it is difficult to optimize the water conditions for the needs of the individual species of seeds. Additionally, the germination conditions for seedlings in the laboratory are different from those in nature. To avoid these issues, we conducted experiments to activate soil seed banks in the field using different water treatments. The results revealed that: (1) generally, the number of species and quantity of seedlings decrease gradually as the water supply decreases, but that for several species most seedlings did not appear when they were provided with the greatest amount of water, and (2) different species present different germination characteristics. According to the rate of seedling emergence, the species were classified into two germination types: fast and slow. In addition, each species also had a unique climax period of emergence, which was delayed with a decrease in water supply. Therefore, the amount of water provided is vital to seedling emergence, and various water treatments should be evaluated when studying the characteristics of different species in soil seed banks. For the lower reaches of the Tarim River, the optimal soil moisture for seedling emergence ranged from 23% to 28%, and seedling conservation should be strengthened during the climax period of emergence (9-15 days from the day when water became available). These results highlight the importance of the use of an optimal water treatment and demonstrate the danger of using a single treatment method. Our results also emphasize the need for a preliminary study prior to conducting studies to evaluate seed banks.     

Effects of water treatments on the activation of soil seed banks – A case study on the lower reaches of the Tarim River

Evaluation of seedling emergence is a common method used to investigate the vegetation restoration potential of soil seed banks. Previous studies have primarily been conducted in the laboratory using a single water treatment. However, when this method is used, it is difficult to optimize the water conditions for the needs of the individual species of seeds. Additionally, the germination conditions for seedlings in the laboratory are different from those in nature. To avoid these issues, we conducted experiments to activate soil seed banks in the field using different water treatments. The results revealed that: (1) generally, the number of species and quantity of seedlings decrease gradually as the water supply decreases, but that for several species most seedlings did not appear when they were provided with the greatest amount of water, and (2) different species present different germination characteristics. According to the rate of seedling emergence, the species were classified into two germination types: fast and slow. In addition, each species also had a unique climax period of emergence, which was delayed with a decrease in water supply. Therefore, the amount of water provided is vital to seedling emergence, and various water treatments should be evaluated when studying the characteristics of different species in soil seed banks. For the lower reaches of the Tarim River, the optimal soil moisture for seedling emergence ranged from 23% to 28%, and seedling conservation should be strengthened during the climax period of emergence (9–15 days from the day when water became available). These results highlight the importance of the use of an optimal water treatment and demonstrate the danger of using a single treatment method. Our results also emphasize the need for a preliminary study prior to conducting studies to evaluate seed banks.     

长江中下游河流沉积物磁性特征初探

通过多参数磁性测量分析,探讨长江中下游干、支流河流沉积物的磁性特征,为研究长江水沙环境积累基础资料.研究结果表明,长江中下游干、支流河流沉积物中,磁性矿物类别均以磁铁矿为主,晶粒均以假单畴-多畴为主.与干流相比,支流沉积物中不完整反铁磁性物质含量较多,晶粒较细,Χ值仅是干流的1/10.随着支流泥沙的汇入,入江口以下江段沉积物的磁性特征相应发生变化.支流泥沙物源贡献的研究是探讨长江中下游干流沉积物环境特征的主要因子.     

塔里木河下游植被覆盖动态变化遥感分析

目的 基于遥感等信息化技术,对塔里木河下游地区应急输水前后的植被覆盖度状况进行动态监测及定性定量分析.方法 选取塔里木河下游地区1999年TM、2002年ETM~+和2004年的ASTER等3期夏季遥感影像和基础地理数据,基于RS,GPS及GIS等技术,通过分类体系划分、遥感信息提取、野外验证等方法,完成了研究区植被覆盖度的动态变化分析.结果 应急输水工程实施后,研究区河道两侧较大范围内的中、高盖度植被覆盖面积明显增加,劣、低盖度植被覆盖面积持续下降,部分地区还出现了较为明显的逆转,生态环境逐步趋于好转.结论 基于RS,GPS及GIS等信息技术,建立植被覆盖度动态监测体系,是研究生态环境动态变化的重要手段和发展趋势.     

断流河道间断输水两岸地下水的运动模型及其解法--以塔里木河下游断流河段生态输水为例

以塔里木河下游断流河段生态输水为背景,根据间断性输水河道充水和停水2个阶段周期性交替重复出现的特征,建立了断流河道间断输水两岸地下水运动的一维非稳定流模型,并通过水位与流量边界条件相互转换的一种方法实现模型的求解,最后应用该模型分析了塔里木河下游断流河段生态输水两岸地下水位恢复状况,其结果比较满意,表明了模型的实用性。     

长江中下游的河床纵剖面演变分析及预测

为预测长江中下游河床纵剖面的演变趋势,利用最小能耗率理论计算了该江段的平衡河床纵剖面,研究了这些河段河床演变规律及其未来的变化。分析了长江水库拦沙、河道采砂、近期水沙变化、未来引水及需水量增长等因素。结果表明,长江中下游河床纵剖面还未达到动态平衡,大部分江段以淤积为主。在没有人类活动影响下,达到动态平衡还需要很长一段时间。由于引水和需水量的增长,未来长江中下游达到动态平衡需要淤积更多的泥沙。     

汉江中下游地区粮食安全问题与对策

分析了我国重要粮仓之一汉江中下游地区的粮食安全状况,讨论了粮食生产所面临的机遇和挑战,针对粮食安全发展所面临的问题,从5个方面提出了汉江中下游地区未来粮食安全保障的对策：保护耕地资源与农业环境;加强水利现代化建设;推进科技兴农;调整粮食作物品种;调整农业的产业结构．