Abstract The Manas River Basin is located in the inland arid area of China. It has a unique natural environment that contains a mountain, oasis, and desert complex ecosystem. Changes in land use type have had significant impacts on the social, economic, and ecological environment in the basin. Based on the remote sensing interpretation data of land use types from 1980 to 2020 in the Manas River Basin, using ArcGIS 10.2 and Fragstats 4.2 and other software to study the temporal and spatial evolution of land use, landscape pattern, and ecological service value (ESV) in the Manas River Basin, several key results were obtained. (1) Unused land accounted for the largest proportion of the total area at about 44%, and the smallest proportion was construction land at 1%, the construction land and farmland areas increased significantly to 82.16 and 34.87%, while the woodland and grassland area decreased to 15.06 and 14.34%, respectively. (2) Between 1980 and 2020, the inflows and outflows of the quantitative transfer tracks for farmland, grassland, and unused land were highly dominant, but the frequent conversion among various types of land led to the transfer tracks becoming more diversified. (3) From 1980 to 2020 the complexity and fragmentation of landscape in the basin decreased, and the heterogeneity, differences, and connectivity of the landscape increased. (4) The ESV of the Manas River Basin had a tendency to initially decrease and then increase, which increased from 237.27 × 10 8 yuan in 1980 to 238.10 × 10 8 yuan in 2020. The above research results can not only provide a basis for the ecological improvement of the Manas River Basin but also provide a reference for the study of other basins/regions in arid areas.
Humid subtropical China is an “oasis” relative to other dry subtropics of the world due to the prevailing of the East Asian summer monsoon (EASM). Although many long climate sensitive tree-rings have been published to understand the historical climate change over various regions in China, long tree-ring chronologies in humid subtropical China are rare due to the difficulty to find old growth trees. This study established a tree-ring chronology spanning from 1776 to 2016 from Cryptomeria fortunei Hooibrenk ex Otto et Dietr in Liancheng area of humid subtropical China, which is also currently the longest chronology in Fujian province. Similar to the climate-growth relationships in neighboring regions, our tree-ring chronology is limited by cold temperature in winter and spring and drought in summer. In addition, a drought stress before the growing season also played a role in limiting the growth of our tree rings. Our climate sensitive tree rings showed different correlations with the Pacific Decadal Oscillation (PDO) in different periods, possibly via modulation of the EASM.
Clarifying the water uptake patterns and competition among riparian plants under different ecological water conveyance conditions is crucial for the stability of the riparian ecosystem in arid areas. Here, we have utilized the Bayesian isotope mixing model to quantify the plant water sources for two typical riparian plants (Tamarix ramosissima and Phragmites australis) along the Manas River in Xinjiang, Northwest China. The water competition relationship between these two typical riparian plants is evaluated using the proportional similarity index (PSI). Our findings demonstrated the following: (1) The climate in the study area is dry and strongly evaporative, and the slope and intercept of the local meteoric water line are smaller than the global meteoric water line. The interconversion between surface water and groundwater occurred mainly in the upper reaches of the river. (2) At the sample site with the long-term ecological water conveyance, the water uptake pattern for typical riparian plants is predominantly shallow soil water or the uniform use of potential water sources. Among them, the utilization rate of shallow soil water reached 30.7 ± 12.6%. At sample sites with intermittent ecological water conveyance and the non-ecological water conveyance sample site, the growth of T. ramosissima and P. australis primarily uses deep soil water and groundwater, with mean values of 34.5 ± 5.1% and 32.2 ± 1.9%, respectively. (3) The water competition between plants at the intermittent ecological water conveyance and non-ecological water conveyance sample sites was more intense. However, the long-term ecological water conveyance effectively reduced water competition among plants. Our results will provide basic theoretical support for maintaining the stability of the Manas River riparian ecosystem and determining environmental flows.
Abstract Peanut (Arachis hypogaea L.) fruits absorb Ca directly from the soil solution; therefore, the concentration of soil solution Ca in the fruiting zone (0–8 cm) is important in determining the availability of adequate Ca during fruit development. Since the critical period for Ca requirement for peanut fruit may extend from 25–65 d after flowering, a measure of extractable Ca (Quantity factor) is also important in determining the replenishment of soil solution Ca over the fruiting period. A laboratory study was conducted to evaluate the effects of varying soil moisture regimes on soil solution and extractable Ca in gypsumamended Bonifay sand (loamy, siliceous, thermic, grossarenic, Plinthic Paleudult) and Greenville sandy loam (clayey, kaolinitic, thermic, Rhodic Kandiudult) soils over a 70‐d period. Soil solution Ca increased in both soils with increasing soil moisture, 14 d after incubation of gypsum‐amended soils. Subsequently, the soil solution Ca decreased for all moisture regimes in the Bonifay soil, but only in the driest regime in the Greenville soil. Soil solution Ca concentrations were 1.0 and 3.2 cmolc/L in the Bonifay soil and 2.7 and 1.6 cmolc/L in the Greenville soil for the wettest and driest regimes, respectively, 70 d after incubation. Gypsum amendment also increased the concentrations of K and Mg in soil solution in both soils; therefore, leaching of excess K and Mg below the fruiting zone may be facilitated in field situations.
Abstract It is essential to analyze the dynamic characteristics of regional groundwater levels and their driving factors for the rational development of groundwater in irrigated areas. This article explores the spatial distribution characteristics of the amplitude of groundwater level change in the Shihezi irrigated area by using the ArcGIS interpolation method and contrast coefficient variance method and analyzes the influence factors of dynamic change of groundwater levels by integrating the grey relational degree and path analysis methods and obtaining the sensitivity of each influencing factor to changes in groundwater levels and the relative importance of the influencing factors. The following results are obtained: (1) the groundwater level of the Shihezi irrigated area showed an overall increasing trend from 2012 to 2019, with a fluctuation range of 12.26–14.14 m. The groundwater level in the southeast of the irrigated area showed an upward trend, while the groundwater level in the northwest area showed a downward trend. (2) The groundwater level in the irrigated area first increased, then decreased, and then increased again. The variance of the contrast coefficient in the irrigated area ranged from 0.04 to 11.31, and the fluctuation range of the groundwater level in the central area was higher than that in the northern and southern areas. (3) The irrigated area of cultivated land and evaporation are the main factors affecting groundwater level change in the Shihezi irrigated area. The grey relation analysis shows that the irrigated area of cultivated land has the highest grey correlation degree with the evolution of the groundwater level, which is 0.947, and the average grey correlation index is between 0.74 and 0.95. Path analysis showed that the irrigated area of cultivated land, surface water usage, and evaporation were the main factors affecting groundwater levels. Human activities are one of the main driving forces of groundwater level change, and the research results provide a theoretical basis for the rational utilization and sustainable development of groundwater resources in the Shihezi irrigation area.
Abstract The Manas River Basin (MRB), Northwest China, is an arid basin dependent on irrigation for agriculture, and human activities are believed to be the primary factor affecting the groundwater level fluctuations in this basin. Such fluctuations can have a significant adverse impact on the social economy, agricultural development, and natural environment of that region. This raises concerns regarding the sustainability of groundwater use. In this study, we used ArcGIS spatial interpolation and contrast coefficient variance analysis to analyse groundwater level, land-use change, and water resource consumption patterns from 2012 to 2019 in the plains of the MRB. The aim was to determine the main factors influencing the groundwater level and to provide a scientific basis for the rational development, utilisation, and management of water resources in this area. During the study period, the groundwater level decreased, increased, and then fluctuated with a gradually slowing downward trend; the decline ranged from −17.82 to −11.67 m during 2012–2019. Within a given year, groundwater levels declined from March/April to August/September, then rose from August/September to March/April, within a range of 0.29–19.05 m. Primary factors influencing the groundwater level included human activities (e.g., changes in land use, river regulation, irrigation, and groundwater exploitation) and natural causes (e.g., climate and weather anomalies). Human activities were the primary factors affecting groundwater level, especially land-use change and water resource consumption. These results provide a theoretical basis for the rational exploitation of groundwater and the optimisation of water resource management in this region.
Understanding contributions of climate change and human activities to changes in streamflow is important for sustainable management of water resources in an arid area. This study presents quantitative analysis of climatic and anthropogenic factors to streamflow alteration in the Tarim River Basin (TRB) using the double mass curve method (DMC) and the Budyko methods. The time series (1960~2015) are divided into three periods: the prior impacted period (1960~1972) and the two post impacted periods, 1973~1986 and 1987~2015 with trend analysis. Our results suggest that human activities played a dominant role in deduction in the streamflow in TRB with contribution of 144.6% to 120.68% during the post impacted period I and 228.68% to 140.38% during the post impacted period II. Climatic variables accounted for 20.68%~44.6% of the decrease during the post impacted period I and 40.38% ~128.68% during the post impacted period II. Sensitivity analysis indicates that the streamflow alteration was most sensitive to changes in landscape parameters. The aridity index and all the elasticities showed an obvious increasing trend from the upstream to the downstream in the TRB. Our study suggests that it is important to take effective measures for sustainable development of eco-hydrological and socio-economic systems in the TRB.
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