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In this paper, detrended canonical correspondence analysis was performed to analyze the relationships between diversity indices and environmental gradients, generalized additive model was employed to modal the response curves of diversity indices to the elevation, based on data from field investigation in the mountainous region of the Ili River Valley and a survey of 94 sample plots. Two hundred fifty-nine plant species were recorded in the 94 sample plots investigated, up to 235 species all appeared in the herb layer, and the species of woody plants were very limited. The communities with a complicated vertical structure presented higher values of indices. The distribution pattern of plant species diversity on the northern slope was affected by such factors as elevation, slope aspect, slope gradient, total nitrogen, total potassium, soil water content, organic matter, and that on the southern slope was mainly affected by such factors as slope gradient, elevation, available phosphorus, and soil water content. On the northern slope, Patrick index and Shannon-Wiener index of the plant communities presented a bimodality pattern along altitude; Simpson index and Pielou index showed a partially unimodal pattern. On the southern slope all the distribution pattern of species diversity indices showed two peaks, though Patrick index's bimodality pattern was not an obvious one. These altitudinal patterns were formed by the synthetic action of a variety of environmental factors with elevation playing an important role. [ABSTRACT FROM AUTHOR]

Changes of stomatal conductance ( g), net photosynthetic rates ( P) and water use efficiency (WUE) were investigated in Populus euphratica grown on sites with different groundwater depths (GDs) under two CO concentrations in the lower reaches of Tarim River, Xinjiang, northwestern China. P in P. euphratica only slightly decreased when the groundwater depth increased from 4.12 to 7.74 m below the ground surface. P values significantly increased in response to an elevated CO concentration at all GDs except at GD of 4.12 m for its good availability of groundwater. WUE values decreased with an initial increase in the groundwater depth, but increased when the groundwater depth reached 7.74 m especially under the elevated CO concentration. The g values measured at 4.12 and 4.74 m both decreased indistinctively by only 3% due to CO enrichment; however, when GDs increased to 5.54 and 7.74 m, the g values decreased significantly by about 10%. It shows that the response of g in P. euphratica to elevated CO is weaker under lower groundwater depth (mild drought stress) but stronger under deeper groundwater depth (moderate drought stress). Results from this study suggest that groundwater depth could determine the response of photosynthesis to future CO enrichment in P. euphratica in arid desert areas. [ABSTRACT FROM AUTHOR]

The article presents a study on the ecological water conveyance and its effect groundwater dynamics and riparian vegetation in nine transects that crosses the Tarim River in Xinjiang, China. It indicates that water recharges has lifted the level of groundwater and that the six to eight meter depth groundwater rose to two to four meter after recharges. It concludes that overbank flows and recharge of streams will benefit more the vegetation.

The article discusses the study of spatio-temporal variation of snow depth in Tarim River basin in Northwestern China. The study uses the empirical orthogonal function (EOF) based on the collected data by special sensor microwave /imager (SSM/I) and scanning mutichannel microwave radiometer (SMMR) from 1979 to 2005. In addition, the Mann-Kendall non-parametric test presented the long-term trend of snow depth and runoff.

The article analyzes the periodic properties of the annual runoff series for the last 40 years in Tarim River Basin in Xinjiang, China which were collected at hydrological gauging stations in its three main branches. It notes that analysis of variance and extrapolation method were employed to identify the annual runoff periods and predicted the future changes in the watershed using simulation methods. It also mentions that the Global Climate Model (GCM) has predicted the basin's long term trend of runoff because of the global increase in air temperature and precipitation in 1990.

Two data sets, annual temperature and precipitation time series from 19 observation stations in the Tarim River basin covering 1958 through 2002, were investigated by non-parametric tests to detect the trend and features of climate change and variability. Based on these data, the snow cover area (SCA) in situ for the period 1982–2001 was further analyzed to examine the effect of climate change on snow. The results showed that both the temperature and precipitation had a jump in the mid 1980s and significantly increased in winter and summer, respectively. The SCA of the entire basin showed a slowly increasing trend. Responses of the SCA to temperature and precipitation in the northern, western and southern regions showed that the effect of precipitation on SCA is larger than that of temperature. In vertical direction, the SCA in the zone below 2,500 m a.s.l. kept a slow increase, but that in the zone above 2,500 m a.s.l. was inching down. Comparatively, the lower altitude zone was apt to be affected by precipitation, while the higher altitude zone tended to be influenced by temperature. The mid zone from 2,500 to 5,000 m was the area most sensitive to and affected by climate change. Compared with that in the 1980s, both the snowing and melting rates were higher in the 1990s. Correlation analysis implied that the SCA change in the cold season was positively correlated with the contemporary precipitation change, but had no strong correlation with the contemporary temperature change. [ABSTRACT FROM AUTHOR]

The hydrological response to climate change in the Tarim River Basin was investigated by analysing the hydrological, temperature and precipitation data of the past 50 years. The long-term trend of the hydrological time-series, including air temperature, precipitation, and streamflow, was examined by using both parametric and non-parametric techniques and the plausible association between streamflow and climate change by the method of grey correlation analysis. The results show that the study area became warmer in the last few decades. The air temperature experienced a significant monotonic increase by 5%; the precipitation showed a significant decrease in the 1970s and then a major increase in the 1980s and 1990s, with average annual precipitation up by 6-8 mm per decade. A step change occurred in both temperature and precipitation around 1986, with mean temperature and precipitation increasing from 67°C and 146 mm before 1986 to 7.3°C and 180 mm respectively after 1986. The temperature has risen by nearly 1 °C over the past 50 years, possibly resulting from the impact of global climate change. Streamflows in the Aksu River and the Yarkant River have shown a significant (P < 0.05) tendency of increase. This is particularly the case for the Aksu River. The coefficients of streamflow increase in the Aksu and Yarkant Rivers are 0.41 and 0.13 respectively. The results of grey correlation analysis show that in the Aksu River, which is located in the northwest of the basin, the impact of precipitation on streamflow is much greater than that of temperature. However, in the Hotan River, which is located in the southwest of the basin, the impact of temperature on streamflow is much greater than that of precipitation. This is likely to be related to the geographic distribution of the headstreams of the rivers. [ABSTRACT FROM AUTHOR]

Abstract: Based on the hydrologic and meteorological data in the Tarim River basin from 1958 to 2004, the trend, characteristics and spatial variation of climate change in the upper reaches of the Tarim River were examined in the study. The long-term trend of climate change and hydrological variations were determined by using both Mann–Kendall and Mann–Whitney nonparametric tests. The results showed that the temperature and precipitation had significantly increased in the drainage basin in the mid-1980s. The climate was the warmest in 1990s among the recent 50 years. The increase of temperature in the tributaries of the Aksu River and Kaidu-Kongque River is higher than that in the tributaries of the Yarkand River and Hotan River. The streamflow at Aksu River showed a significant increasing monotonic trend. The annual runoff in the Aksu River had increased by 10.9% since 1990. The independence test of temperature and precipitation with of the El Nino event reveals that there is no significant effect of the El Nino and La Nina events on the annual temperature and annual precipitation in the drainage basin. [Copyright &y& Elsevier]