Chen Yapeng

Analysis on the ecological benefits of the stream water conveyance to the dried-up river of the lower reaches of Tarim River, China

This paper analyzes the monitored data of the 4 times of stream water conveyances to the river section where the stream flow was cut-off, of 9 groundwater-monitoring sections and 18 vegetation plots in the lower reaches of Tarim River. The results show that the groundwater depth in the lower reaches of Tarim River rose from 9.87 m before the conveyances to 7.74 m and 3.79 m after the first and second conveyances, 3.61 and 3.16 m after the 2 phases of the third conveyance, and 2.66 m after the fourth conveyance. The transverse response scope of groundwater level was gradually enlarged along both sides of the channel of conveyances, i.e., from 450 m in width after the first conveyance to 1050 m after the fourth conveyance, but the response degree of groundwater level was reduced with the increase of the distance away from the channel of conveyances. The composition, distribution and growth status of the natural vegetation are directly related to the groundwater depth. The indexes of Simpson’s biodiversity, McIntosh’s evenness and Margalef’s richness, which reflect the change of the quantity of species and the degree of biodiversity, are reduced from 0.70, 0.48 and 0.90 to 0.26, 0.17 and 0.37 respectively along with the drawdown of groundwater level from the upper reaches to the lower reaches. After the stream water conveyances, the natural vegetation in the lower reaches is saved and restored along with the rise of groundwater level, the response scope of vegetation is gradually enlarged, i.e., from 200-250 m in width after the first conveyance to 800 m after the fourth conveyance. However, there is still a great disparity to the objective of protecting the “Green Corridor” in the lower reaches of Tarim River. Thus, it is suggested to convey the stream water in double-channel way, combine the conveyance with water supply in surface scope, or construct the modern pipe-conveyance network systems so as to save the natural vegetation in an intensive way, achieve the efficient water consumption and speed up the restoration and regeneration of the damaged ecosystems in the lower reaches of Tarim River.

Climate change and hydrologic process response in the Tarim River Basin over the past 50 years

Climate change and hydrologic process response in the Tarim River Basin over the past 50 years are the focus of more and more researchers’ attention. In this paper, both temperature and precipitation time series were found to present a monotonic increasing trend using nonparametric tests. Noticeably, a significant step change in both temperature and precipitation time series occurred in 1986. By contrasting the trends of natural water process in headstream and mainstream, we found that it was anthropogenic activities not climate change that caused the river dried up and vegetation degenerated in the lower reaches of Tarim River. The results of gray correlation analysis show that the runoff of higher latitude distributing river is more closely associated with winter snow stocking, while that of lower latitude is more closely related to summer temperature. Runoff in the headstream is more sensitive to precipitation, while that in the mainstream is more sensitive to evaporation. The strong evaporation caused by increasing temperature weakened runoff to some extent in spite of the fact that precipitation increased over the past 50 years.

Rational groundwater table indicated by the eco-physiological parameters of the vegetation: A case study of ecological restoration in the lower reaches of the Tarim River

The eco-physiological response and adaptation of Populus euphratica Oliv and Tamarix ramosissima Ldb during water release period were investigated. Nine typical areas and forty-five tran-sects were selected along the lower reaches of Tarim River. The groundwater table as well as plant performance and the contents of proline, soluble sugars, and plant endogenous hormone (ABA, CTK) in leaves were monitored and analyzed. The groundwater table was raised in different areas and tran-sects by water release program. The physiological stress to P. euphratica and T. ramosissima had been reduced after water release. Our results suggested that the groundwater table in the studied region remained at −3.15 to −4.12 m, the proline content from 9.28 to 11.06 (mmol/L), the soluble sugar content from 224.71 to 252.16 (mmol/L), the ABA content from 3.59 to 5.01 (ng/g FW), and the CK content from 4.01 to 4.56 (ng/g FW), for the optimum growth and restoration of P. euphratica indicated by the plant performance parameters and the efficiency of water application was the highest. The groundwater table in the studied region remained at −2.16 to −3.38 m, the proline content from 12.15 to 14.17 (mmol/L), the soluble sugar content from 154.71 to 183.16 (mmol/L), the ABA content from 2.78 to 4.86 (ng/g FW), and the CK content from 3.78 to 4.22 (ng/g FW), for the optimum growth and restoration of T. ramosissima indicated by the plant performance parameters and the efficiency of water application was the highest. The rational groundwater table for the restoration of vegetation in the studied region was at −3.15 to −3.38 m.

Response of snow cover to climate change in the periphery mountains of Tarim river basin, China, over the past four decades

Abstract Data of annual mean temperature, annual total precipitation and snow-cover area (SCA) in the winter season from 1982 to 2001 have been analyzed to examine the response of SCA to climate change in the Tarim basin, western China. The results show that over the entire basin SCA exhibits a slowly decreasing trend. The responses of SCA to temperature and precipitation in the northern, western and southern parts of the basin show a stronger effect of precipitation change on SCA than that of temperature. SCA has slowly increased below 2500ma.s.l., but has decreased at higher altitudes. The lowest-altitude zone was apt to be affected by precipitation, while the highest-altitude zone seems to have been influenced mainly by temperature. The middle zone from 2500 to 5000 m was the most sensitive to climate change. Snowfall and melt rates were higher in the 1990s than in the 1980s. In the winter season, SCA change was positively correlated with precipitation change but not with temperature change.

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°C 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 Karda...