Search

Warming of the climate system is unequivocal, and the change of climate variables will eventually have a great impact on vegetation cover and agricultural practices, especially in the arid area Xinjiang in China, whose agriculture and ecosystems are heavily vulnerable to climate change. In this paper, normalized difference vegetation index (NDVI) was used to study the vegetation growth and its response to climate change in Xinjiang. Firstly, two NDVI datasets (Global Inventory Modeling and Mapping Studies (GIMMS) and Moderate Resolution Imaging Spectroradiometer (MODIS)) were merged through a pixel-wise regression analysis to obtain a long time series of NDVI data, and then, relationships between yearly NDVI and yearly climate variables, and monthly NDVI and monthly climate variables were extensively investigated for grassland and cropland in northern and southern Xinjiang, respectively. Results show the following: (1) there was an increasing trend in NDVI for both grassland and cropland in both northern and southern Xinjiang over the past decades and trends were significant except that for grassland in northern Xinjiang; (2) precipitation and evaporation were more important than temperature for grassland in northern Xinjiang, while precipitation and temperature were more important than evaporation for grassland in southern Xinjiang and cropland in both northern and southern Xinjiang; (3) NDVI was highly correlated with accumulated monthly precipitation instead of monthly precipitation, and there was a lagged effect of precipitation, temperature, and evaporation on NDVI change. However, lagged effects were only significant in specific months. The results could be helpful to agricultural practices; e.g., based on lagged effect of precipitation, irrigation in July is very important for crop growth. [ABSTRACT FROM AUTHOR]

Based on the features of environment and the fact of successful artificial afforestation, the paper points out that the restoration of vegetation in Arid-hot valleys along the Jinshajiang River should be implemented mainly by planting sparse — arbor/ shrub/ tussock Combination. Four ways to restore vegetation in the area are given in the paper. [ABSTRACT FROM AUTHOR]

Abstract: An oasis is defined here as an efficient eco-geographical landscape that allows flourishing vegetation or human settlement due to a stable water supply in an arid region. The water resource is the major limiting factor impacting the oasis scale in arid regions. For discussion of the suitable scale of an oasis supported by a specific quantity of water resource, the Manas River Basin, a typical continental river basin in the arid region of China, was taken as the study object. Based on the remote sensing images and socio-economic data, the stability and suitable scale of oasis in 1976, 1987, 1998, 2010, and 2020 were analyzed using an oasis water-heat balance model. The results indicated that (1) the respective stability index (H 0) of 1976, 1987, 1998, and 2010 was 0.10, 0.15, 0.40, and 0.38, respectively, changing from an unstable level into a metastable level. (2) Under the guarantee of natural oasis ecosystem stability, the suitable scales of natural oasis in 1976, 1987, 1998, and 2010 were 697.2–1045.7 km2, 942.2–1413.3 km2, 2042.0–3063.0 km2, and 1428.2–2142.3 km2, respectively. The suitable scales of the total oases were 3681.3–4030.3 km2, 5259.1–5730.2 km2, 7654.5–8675.5 km2, and 8130.3–8844.4 km2, respectively. (3) If the artificial oasis scale remained unchanged from 2010, the suitable scale of the natural oasis in the Manas River Basin in 2020 would be 1695.8–2543.8 km2, and the suitable scale of the total oases would be 8398–9246 km2. With a reasonable proportion between natural and artificial oases, the suitable scales of each would be 3400.3–5100.5 km2 and 2266.9–3400.4 km2. This paper not only provides data for reasonable oasis planning of the Manas River Basin, but also provides a new direction for studies on the suitable scale of oases in arid regions. [Copyright &y& Elsevier]

Abstract: In the Tarim River Basin, the desert riparian forest vegetation is under high-temperature and aridity stress. However, the vegetation can grow continuously because of deep rooting that can reach groundwater, which can thus redistribute water into the upper soil profile. This paper describes patterns of hydraulic lift by Populus euphratica Oliv. and discusses its ecological effects. Our results show that the tap root sap velocity of P. euphratica Oliv. is positive during the day and night. However, a reverse sap flow was observed in the lateral roots during the night. The soil water content of the subsoil was higher than that of the topsoil at depths of 0–120cm. When the sap flow of the lateral roots was reversed at night, the soil water content clearly increased. In particular, at depths of 60–120cm, the soil water content at 4:00 was 28–38% greater than that at 16:00. The vapor pressure deficit was a factor that predominantly affected the root sap velocity, and the smaller vapor pressure deficit often facilitated a reverse sap flow in the lateral roots. Our findings demonstrate the hydraulic lift characteristics and ecological effects that occur in the desert riparian forest in extremely arid regions of middle Asia [Copyright &y& Elsevier]