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We developed a tree ring-width chronology of Abies georgei at the timber line in the Big Snow Mountain Scenic Area in northwestern Yunnan, China. The climate-tree growth response analysis indicated that temperature was the predominant regulator of A. georgei growth in this region. An annual mean minimum temperature (AMMT) reconstruction spanning A.D. 1837–2016 was developed with a linear regression model (y = 1.0x − 6e − 5) that accounted for 50.7% of the actual temperature variance during the common period (1960–2016). Based on the reconstructed temperature series, the warmer periods were 1840–1845, 1855–1865, 1880–1895, 1945–1965, and from 1995 until the present day, and the cold periods were 1870–1880, 1900–1930, and 1966–1980. By comparing our results with other regional tree ring records from surrounding areas, a distinctive amount of common warm and cold periods were found, indicating the reliability of our temperature reconstruction and suggesting that the climate in the study area was part of a large-scale climate system.

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.

Soil toxic metal pollution is one of the most prominent environmental problems in the rapid industrialization of societies because of the considerable harm caused to human existence and the surrounding environments. Soil samples from 80 sampling sites around the coal-mining region of northwestern China were collected, and the geo-accumulation index (Igeo), pollution index (PI), and potential ecological risk index (PRI) were calculated, with the objective of assessing the soil toxic metal pollution level. The results showed that the average concentrations of Cr, Hg, and As exceeded the regional background values and the national soil environmental quality standards of China, while those of Zn, Cu, and Pb were below both soil-quality standards. The Igeo of toxic metals was ranked as Hg > As > Cr > Pb > Cu > Zn. The Igeo of Zn, Cu, and Pb indicated low pollution; the soils were moderately polluted by Hg and slightly moderately polluted by As, while other elements presented low pollution levels. The PI values of both As and Hg were higher than 3, indicating heavy pollution of these two metals. Zn and Cu originated from parent material, while Cr, As, and Hg originated from human activities such as coal burning, chemical industry, and traffic. Pb was influenced by both natural factors and human activities. The results of ecological risk assessment in the region showed that Zn, Cu, Cr, and Pb in all sample sites presented a low ecological risk, while Hg presented a high ecological risk. Therefore, Hg is the most hazardous toxic metals in the region. The spatial distribution trends revealed that the high-risk regions were found to be the industrial region of the study area. The research results provide a scientific basis and technical support for monitoring and early warning of soil pollution in arid regions.

The aim of this study is to estimate the water consumption of a Populus euphratica forest. Findings provide a scientific basis for water allocation to the lower reaches of the Tarim River, in Northwest China. In this paper, several different methods were used to gather data. The heat-pulse technique was applied to determine the stem sap flow of P. euphratica sample trees from May to September of 2015. Then, the P. euphratica sapwood area estimation model was established based on the correlation between the sapwood area and the tree biometric parameters. Finally, the water consumption of P. euphratica (n = 3000) trees was calculated. The results showed that the estimated sapwood area of P. euphratica (n = 3000) was 677,000 cm2, and the total water consumed by these trees during the measurement period was 23,000,000 L. The P. euphratica sap flow varies due to changing environmental factors. The average daily sap flow velocities were 814.3, 1461.75, 1907.27, 1657.51 and 1173.65 mL h−1 from May to September, respectively. The average daily accumulated sap flow was 22.44, 34.76, 46.98, 40.59 and 32.90 L from May to September, respectively. Pearson correlation analysis showed that variation of sap flow was positively related to solar radiation (R s) (R 2 = 0.715), air temperature (T a) (R 2 = 0.744), soil temperature (T s) (R 2 = 0.806), wind speed (W s) (R 2 = 0.104). At the same time, sap flow was negatively related to air humidity (H) (R 2 = −0.305). Stepwise regression analysis showed that solar radiation, air temperature, soil temperature and air humidity are the main factors influencing the P. euphratica sap flow variation.

The Tarim River is about 1,320 km long and is one of the longest continental inland waterways in the world. In an undisturbed state, it is accompanied on both sides by floodplain forests of Euphrates poplar (Populus euphratica Oliv.). The rising water consumption in the upper and middle reaches, and massive hydro-technical interventions in the development of uncultivated land for cotton farming, especially during the last decades, have led to a widespread destruction of the natural ecosystems. This is the case particularly in the lower reaches of the river, where 320 km of the floodplain forests are either highly degraded or dead. Since the year 2000, the Chinese government has made efforts to restore these ecosystems and conducted man-made water diversion project into the affected area. The starting phase of recovering measures needs an efficient and extensive long-term monitoring. A combined approach of remote sensing and terrestrial samples can meet these demands. This study is based on the data from a small-scale ecological monitoring in the past 7 years and combination of QuickBird image information of the floodplain forests along the lower reaches of the Tarim River within the purview of the man-made restoration project. The effects of the artificial water diversion on the dynamics of the groundwater layer and the revitalization of P. euphratica floodplain forests have been analysed in the Arghan transect. The results showed that the groundwater level has risen from 12.6 to 5.5–6.2 m below the surface in the vicinity of the river beds. Some eco-morphological parameters of the P. euphratica trees have different levels of response to the ecological water diversion. To specify, in the vertical direction, the farther the trees are from the river, the weaker the response of ecological indicators. These parameters include tree vitality level, crown diameter, under branch height as well as newly developed crown types of P. euphratica trees. Generally, the floodplain forests within 200 m to the riverbed recovered remarkably, and those between 200 and 800 m from the river showed a medium response to the water transfer, while forests further away than 800 m from the river bed showed less sign of recovery.