Jinyi Fu

Effects of ecological water conveyance on the ring increments of Populus euphratica in the lower reaches of Tarim River

Because of long-term drying of the lower reaches of the Tarim River, oasis ecosystems are facing serious threats and have started to degenerate. An ecological water conveyance project has been started in the lower reaches of the Tarim River to save the degenerated ecosystem. The effects of ecological water conveyance on the ring width increments of Populus euphratica were studied by use of the trend analysis method, the moving t test technique, and a regression equation based on ring increment data from the past 40xa0years in the lower reaches of the Tarim River. Results showed that the ring increments of Populus euphratica in four monitoring transects along the river can be divided into two parts, 1970–2001 and 2002–2008. This division implies that ecological water conveyance had a positive effect on the increase of ring increments. The ring increments of Populus euphratica in Yinsu, Kardayii, Alagan, and Yiganbjma increased by 79.37, 174.5, 75.61, and 71.81% after ecological water conveyance. The years 2002, 2001, 2001, and 2002 were the transition years in the Yinsu, Alagan, Kardayi, and Yiganbjma transects, respectively. The ring width increments in Yinsu, Kardayi, Alagan, and Yiganbjma as a result of ecological water conveyance were 1.41, 0.987, 0.265, and 0.671xa0mm, respectively. The main cause of the changes in ring width increments was the rise of groundwater level. The results from this study should contribute to improved management of the ecosystems in the lower reaches of the Tarim River, and can also provide a scientific basis for implementing similar projects in other arid and semiarid areas.

Temporal and Spatial Variation in Regional Climate and its Impact on Runoff in Xinjiang, China

Based on the meteorological and surface runoff data from Xinjiang for the past 50xa0years, this study examined the temporal-spatial variation characteristics of the air temperature, precipitation and runoff in Xinjiang using nonparametric tests and wavelet analysis. The results indicate that the air temperature declined slightly in Kuche (KC). There were slight increasing trends in Bayinbluk (BYBLK), Alar (ALR) and Yutian (YT). The rest of the meteorological stations all had significant increasing trends. The precipitation showed significant increasing trends in the Altai Mountains, Alashankou (ALSK) and Jinghe (JH) in northern Xinjiang and a slight decreasing trend in Tuoli (TL). The other stations showed slight increasing trends. The annual rate of change of precipitation was greater in the northern mountain area than in the southern plains area. In the Tianshan Mountains, the decreasing trend of precipitation at BYBLK was not statistically significant, while the precipitation in the other stations increased to the high-precipitation areas from two low-precipitation centers, Zhaosu (ZS) and BYBLK. In the Tarim Basin of southern Xinjiang, the increasing trend and increasing rate of precipitation were more significant on the northern margin than they were on the southern margin. With regard to the surface runoff, significant uptrends appeared in Kenswat (KSWT), Dashankou (DSK), Shiliguilank (SLGLK), Xiehela (XHL) and Yzmeilek (YZMLK). Kaqun (KQ) and Wuluwat (WLWT) had slight increases, and Tongguzlek (TGZLK) showed a slight downtrend. The variations in air temperature and precipitation in Xinjiang had significant periods of 4–9xa0years and 3–10xa0years, respectively. The periods for the annual runoff were 5–9xa0years.

Impact of long-term zero-flow and ecological water conveyance on the radial increment of Populus euphratica in the lower reaches of the Tarim River, Xinjiang, China

Based on the dendro-hydrology theory, we studied the impacts of two significant environmental occurrences (long-term zero-flow and ecological water conveyance) on the radial increment of Populus euphratica in the lower reaches of the Tarim River, Xinjiang, China. We also studied the relationships between radial increment and groundwater table as a function of the distance from the river channel. We found that the radial increment of P. euphratica respond significantly to both zero-flow and water conveyance, and these responses differed among four transects and they weakened with increasing distance from the Daxihaizi Reservoir. The depth to the groundwater table is a key factor that restricts P. euphratica growth in extremely arid regions, and the relationship between radial increment and the groundwater table was significant. The radial increment decreased remarkably with increasing duration of the zero-flow period. The influence of long-term zero-flows on P. euphratica growth was a long-term and slow process. The response of P. euphratica showed a delayed response to the groundwater changes after ecological water conveyance. This lag response differed among the monitoring transects and different distances away from river channel.

Impact of Implementation of Large-Scale Drip Irrigation in Arid and Semi-arid Areas: Case Study of Manas River Valley

With the large-scale application of drip irrigation under mulching, drip-irrigated areas have experienced significant changes in the past 10 years in the Manas River valley. Based on long-term monitoring data of soil salt content and groundwater depth and the investigation of shelter forest growth and seedling emergence, this article analyzed the distribution characteristics of soil salt content in different drip-irrigated soil layers and their effect on the environment. The main conclusions are as follows: (1) Two obvious soil layers of salt accumulation are 40–80 cm deep after drip irrigation and 0–5 cm deep before drip irrigation. (2) Salt accumulated in different soil layers after drip irrigation for several years: 0–40 cm and 40–100 cm deep after drip irrigation for 3 and 7 years respectively. (3) Extension of the drip-irrigated area has caused a number of environmental problems in the study area, and countermeasures for agricultural development in arid and semi-arid areas are proposed.

Evaluation of oasis land use security and sustainable utilization strategies in a typical watershed in the arid regions of China

Land supports the survival and development of humans. To safeguard the land use security of continental river watersheds in arid regions, the oasis of the Manas River Watershed was investigated using 15 evaluation indexes from three subsystems, including land use suitability, land use vulnerability and water security to provide a comprehensive evaluation based on the methods of analytic hierarchy process and fuzzy synthetic evaluation model, social economy and land use/cover data from remote sensing images for 1976, 1987, 1998 and 2010. The above-mentioned indexes were classified into four levels, which were regarded as security (v1), relative security (v2), security threshold (v3) and insecurity (v4). The results showed that land use securities of oasis in the Manas River Watershed were at the insecure level of v4, and that the synthetic graded values were 0.6150, 0.5772, 0.5617 and 0.5640, respectively. For the three subsystems, indexes of land use suitability were all at the security level of v1, and the indexes of land use vulnerability were at the levels of v1, v2, v4 and v4 in the 4xa0years investigated, respectively. Furthermore, indexes of water security in the 4xa0years were all classified as insecure levels. Ultimately, it is important to determine the leading factors that restrict land use security and then put forward corresponding solutions. The objects of this study were to achieve sustainable land use in the Manas River Watershed, as well as provide scientific references for evaluation of land use security in the continental river watershed of arid regions.