The isotope composition in precipitation has been widely considered as a tracer of monsoon activity.Compared with the coastal region,the monsoon margin usually has limited precipitation with large fluctuation and is u...The isotope composition in precipitation has been widely considered as a tracer of monsoon activity.Compared with the coastal region,the monsoon margin usually has limited precipitation with large fluctuation and is usually sensitive to climate change.The water resource management in the monsoon margin should be better planned by understanding the composition of precipitation isotope and its influencing factors.In this study,the precipitation samples were collected at five sampling sites(Baiyin City,Kongtong District,Maqu County,Wudu District,and Yinchuan City)of the monsoon margin in the northwest of China in 2022 to analyze the characteristics of stable hydrogen(δD)and oxygen(δ18O)isotopes.We analyzed the impact of meteorological factors(temperature,precipitation,and relative humidity)on the composition of precipitation isotope at daily level by regression analysis,utilized the Hybrid Single-Particle Lagrangian Integrated Trajectory(HYSPLIT)-based backward trajectory model to simulate the air mass trajectory of precipitation events,and adopted the potential source contribution function(PSCF)and concentration weighted trajectory(CWT)to analyze the water vapor sources.The results showed that compared with the global meteoric water line(GMWL),the slope of the local meteoric water line(LMWL;δD=7.34δ^(18)O-1.16)was lower,indicating the existence of strong regional evaporation in the study area.Temperature significantly contributed toδ18O value,while relative humidity had a significant negative effect onδ18O value.Through the backward trajectory analysis,we found eight primary locations that were responsible for the water vapor sources of precipitation in the study area,of which moisture from the Indian Ocean to South China Sea(ITSC)and the western continental(CW)had the greatest influence on precipitation in the study area.The hydrogen and oxygen isotopes in precipitation are significantly influenced by the sources and transportation paths of air mass.In addition,the results of PSCF and CWT analysis showed that the water vapor source areas were primarily distributed in the south and northwest direction of the study area.展开更多
Understanding the hydrogen and oxygen stable isotope composition and characteristics of different water bodies in soil-plant-atmosphere continuum is of significance for revealing regional hydrological processes and wa...Understanding the hydrogen and oxygen stable isotope composition and characteristics of different water bodies in soil-plant-atmosphere continuum is of significance for revealing regional hydrological processes and water cycle mechanisms.In this study,we analyzed the stable isotopic composition,relationship and indicative significance of precipitation,soil water(0~100 cm depth)and xylem water of Qinghai spruce(Picea crassifolia)forest in the eastern Qilian Mountains,and explored the circulation process among different water bodies.The results show that the stable isotopes of precipitation vary greatly during the entire observation period.The values ofδ2H andδ^(18)O in the precipitation in the warm season are richer than those in the cold season,and the slope and intercept of local meteoric water line(LMWL,δ2H=6.79δ18O+7.13)are both smaller than global meteoric water line(GMWL,δ2H=8.17δ18O+10.56).The stable isotopes of soil water at different depths underwent different degrees of evaporative fractionation,and theδ18O andδ2H of shallow soil water varied greatly,while the deep soil water tended to be similar.The topsoil(0~10 cm)can respond quickly to precipitation,and the response of the deep soil has a time lag.In the whole growing season,0~30 cm and 60~100 cm soil water are the main water sources of Qinghai spruce.The water source of Qinghai spruce was from all soil layers in May and September,mainly from the shallow soil layer(0~30 cm)in August and October,and mainly from the deep soil layer(60~100 cm)in June and July.展开更多
Desert rhizoliths are generally found as weathered,broken and scattered samples on dune field surface,but rarely insitu in their initial states buried under the soil of desert in the Badain Jaran Desert,northwest Chin...Desert rhizoliths are generally found as weathered,broken and scattered samples on dune field surface,but rarely insitu in their initial states buried under the soil of desert in the Badain Jaran Desert,northwest China.This study off ers an assessment of the morphological,mineralogical,and chemical properties of intact and in-situ rhizoliths found in soils of swales and depressions among dune chains.The characteristics of these rare and precious objects were assessed using optical polarizing microscopy,cathodoluminescence,scanning electronic microscopy,radiocarbon dating,and stable isotopic analyses,providing the opportunity for discussion of the rhizolith formation mechanisms and associated environmental conditions.Field and laboratory investigations showed that the in-situ intact rhizoliths were formed only in the places where Artemisia shrubs are living,and the remaining root relicts within rhizoliths belong to this species.The spatial distribution of rhizoliths also suggested that low topographic positions on a landscape provided soil moisture,and redox environments favored rhizolith formation.A semi-closed redox environment in the subsoil at swales and depressions,where water is always present,along with the sandy soil texture,facilitated fast water percolation to deeper depths and condensation.Such a soil environment not only provides water for Artemisia growth,but also for the weathering of minerals such as felspars and calcite from primary carbonates,and for the decomposition of root relicts.Furthermore,harsh climatic conditions,such as strong winds and solar radiation,led to water evaporation through dead root channels and triggered the calcification along the root relicts.The entrapped lithogenic carbonates and to a lesser extent the decomposition of Artemisia roots provided the carbon sources for the rhizoliths formation,while the weathering of soil minerals,particularly feldspars and carbonates,was the main source of Ca.Rhizoliths in the Badain Jaran desert formed relatively quickly,probably over a few soil drying episodes.This led to the entrapment of a large quantity of lithogenic carbonates(more than 90%of carbon)within rhizolith cement.The re-dissolution of the entrapped lithogenic carbonates in rhizolith tubes should be taken into account in the paleoenvironmental interpretation ofC ages,the latter suggesting that rhizoliths formed during the Holocene(~2053 years cal BP,based on root organic relicts).展开更多
Climate change is the dominant factor affecting the hydrological process, it is of great significance to simulate and predict its influence on water resources management, socio-economic activities, and sustainable dev...Climate change is the dominant factor affecting the hydrological process, it is of great significance to simulate and predict its influence on water resources management, socio-economic activities, and sustainable development in the future. In this paper, the Xiying River Basin was taken as the study area, China Atmospheric Assimilation Driven Data Set(CMADS) and observation data from the Jiutiaoling station were used to simulate runoff of the SWAT model and calibrate and verify model parameters. On this basis, runoff change of the basin under the future climate scenario of CMIP6 was predicted. Our research shows that:(1) The contribution rates of climate change and human activities to runoff increase of the Xiying River are 89.17% and 10.83%, respectively. Climate change is the most important factor affecting runoff change of the Xiying River.(2) In these three different emission scenarios of SSP1-2.6, SSP2-4.5 and SSP5-8.5 in CMIP6 climate model, the average temperature increased by0.61, 1.09 and 1.74 C, respectively, in the Xiying River Basin from 2017 to 2050. Average precipitation increased by 14.36, 66.88, and 142.73 mm, respectively, and runoff increased by 15, 24, and 35 million m3, respectively.The effect of climate change on runoff will continue to deepen in the future.展开更多
Identifying geochemical characteristics of aeolian sands on the Qinghai-Tibet Plateau(QTP)is essential for understanding the relationship between earth surface processes and paleoclimatic fluctuations in the region.He...Identifying geochemical characteristics of aeolian sands on the Qinghai-Tibet Plateau(QTP)is essential for understanding the relationship between earth surface processes and paleoclimatic fluctuations in the region.Here,we present new geochemical data which provides insight to the sedimentary environment of aeolian sands in the Dinggye region,southern Tibet.We sampled aeolian dune sands in a variety of settings,and determined grain size and concentration of major oxides and trace elements in the fine and coarse fractions.Results show that aeolian sediments are dominated by fine and medium sands,with a single-peaked frequency curve and a 3-stage probability cumulative curve.The fine and coarse fractions exhibit considerable heterogeneity in elemental concentrations and ratios and upper continental crust-normalized(UCC)distribution.The geochemical evidence indicates that wind dynamic sorting is responsible for the differentiation between fine and coarse fractions in different types of aeolian sand,rather than sediment provenance.Additionally,fine-fraction sediments are well dispersed and can be differentiated from the coarse fraction,suggesting that they contain more environmental information.Multidimensional scale(MDS)and principal component analysis(PCA)of commonly used tracer elements show that flood plain sediments are the sand source for mobile dunes and nebkhas,and lakeshore sediments are the sand source for climbing sand sheets.展开更多
In order to cope with drought and water shortages,the working people in the arid areas of Northwest China have developed a drought-resistant planting method,namely,gravel-sand mulching,after long-term agricultural pra...In order to cope with drought and water shortages,the working people in the arid areas of Northwest China have developed a drought-resistant planting method,namely,gravel-sand mulching,after long-term agricultural practices.To understand the effects of gravel-sand mulching on soil water evaporation,we selected Baifeng peach(Amygdalus persica L.)orchards in Northwest China as the experimental field in 2021.Based on continuously collected soil water stable isotopes data,we evaluated the soil evaporation loss rate in a gravel-sand mulching environment using the line-conditioned excess(lc-excess)coupled Rayleigh fractionation model and Craig-Gordon model.The results show that the average soil water content in the plots with gravel-sand mulching is 1.86%higher than that without gravel-sand mulching.The monthly variation of the soil water content is smaller in the plots with gravel-sand mulching than that without gravel-sand mulching.Moreover,the average lc-excess value in the plots without gravel-sand mulching is smaller.In addition,the soil evaporation loss rate in the plots with gravel-sand mulching is lower than that in the plots without gravel-sand mulching.The lc-excess value was negative for both the plots with and without gravel-sand mulching,and it has good correlation with relative humidity,average temperature,input water content,and soil water content.The effect of gravel-sand mulching on soil evaporation is most prominent in August.Compared with the evaporation data of similar environments in the literature,the lc-excess coupled Rayleigh fractionation model is better.Stable isotopes evidence shows that gravel-sand mulching can effectively reduce soil water evaporation,which provides a theoretical basis for agricultural water management and optimization of water-saving methods in arid areas.展开更多
Caragana korshinskii Kom.and Tamarix ramosissima Ledeb.are pioneer shrubs for water and soil conservation,and for windbreak and sand fixation in arid and semi-arid areas.Understanding the water use characteristics of ...Caragana korshinskii Kom.and Tamarix ramosissima Ledeb.are pioneer shrubs for water and soil conservation,and for windbreak and sand fixation in arid and semi-arid areas.Understanding the water use characteristics of different pioneer shrubs at different ages is of great importance for their survival when extreme rainfall occurs.In recent years,the stable isotope tracing technique has been used in exploring the water use strategies of plants.However,the widespreadδ^(2)H offsets of stem water from its potential sources result in conflicting interpretations of water utilization of plants in arid and semi-arid areas.In this study,we used three sets of hydrogen and oxygen stable isotope data(δ^(2)H andδ^(18)O,correctedδ^(2)H_c1 based on SW-excess andδ^(18)O,and correctedδ^(2)H_c2 based on−8.1‰andδ^(18)O)as inputs for the MixSIAR model to explore the water use characteristics of C.korshinskii and T.ramosissima at different ages and in response to rainfall.The results showed thatδ^(2)H_c1 andδ^(18)O have the best performance,and the contribution rate of deep soil water was underestimated because ofδ^(2)H offset.During the dry periods,C.korshinskii and T.ramosissima at different ages both obtained mostly water from deeper soil layers.After rainfall,the proportions of surface(0-10 cm)and shallow(10-40 cm)soil water for C.korshinskii and T.ramosissima at different ages both increased.Nevertheless,there were different response mechanisms of these two plants for rainfall.In addition,C.korshinskii absorbed various potential water sources,while T.ramosissima only used deep water.These flexible water use characteristics of C.korshinskii and T.ramosissima might facilitate the coexistence of plants once extreme rainfall occurs.Thus,reasonable allocation of different plants may be a good vegetation restoration program in western Chinese Loess Plateau.展开更多
Altitude affects leaf stoichiometry by regulating temperature and precipitation,and influencing soil properties in mountain ecosystems.Leaf carbon concentration(C),leaf nitrogen concentration(N),leaf phosphorous conce...Altitude affects leaf stoichiometry by regulating temperature and precipitation,and influencing soil properties in mountain ecosystems.Leaf carbon concentration(C),leaf nitrogen concentration(N),leaf phosphorous concentration(P),and their stoichiometric ratios of Leontopodium lentopodioides(Willd.)Beauv.,a widespread species in degraded grasslands,were investigated to explore its response and adaptation strategy to environmental changes along four altitude gradients(2500,3000,3500,and 3800 m a.s.l.)on the northeastern Qinghai-Tibetan Plateau(QTP),China.The leaf C significantly varied but without any clear trend with increasing altitude.Leaf N showed an increasing trend,and leaf P showed a little change with increasing altitude,with a lower value of leaf P at 3500 m than those at other altitudes.Similarity,leaf C:P and N:P exhibited a little change with increasing altitude,which both had greater values at 3500 m than those at other altitudes.However,leaf C:N exhibited a decreasing trend with increasing altitude.Soil NH^(+)_(4)-N,soil pH,soil total phosphorus(STP),mean annual temperature(MAT),and mean annual precipitation(MAP)were identified as the main factors driving the variations in leaf stoichiometry of L.lentopodioides across all altitudes,with NH^(+)_(4)-N alone accounting for 50.8%of its total variation.Specifically,leaf C and N were mainly controlled by MAT,soil pH,and NH^(+)_(4)-N,while leaf P by MAP and STP.In the study area,it seems that the growth of L.lentopodioides may be mainly limited by STP.The results could help to strengthen our understanding of the plasticity of plant growth to environmental changes and provide new information on global grassland management and restoration.展开更多
Variations of precipitation have great impacts on soil carbon cycle and decomposition of soil organic matter.Soil bacteria are crucial participants in regulating these ecological processes and vulnerable to altered pr...Variations of precipitation have great impacts on soil carbon cycle and decomposition of soil organic matter.Soil bacteria are crucial participants in regulating these ecological processes and vulnerable to altered precipitation.Studying the impacts of altered precipitation on soil bacterial community structure can provide a novel insight into the potential impacts of altered precipitation on soil carbon cycle and carbon storage of grassland.Therefore,soil bacterial community structure under a precipitation manipulation experiment was researched in a semi-arid desert grassland in Chinese Loess Plateau.Five precipitation levels,i.e.,control,reduced and increased precipitation by 40%and 20%,respectively(referred here as CK,DP40,DP20,IP40,and IP20)were set.The results showed that soil bacterial alpha diversity and rare bacteria significantly changed with altered precipitation,but the dominant bacteria and soil bacterial beta diversity did not change,which may be ascribed to the ecological strategy of soil bacteria.The linear discriminate analysis(LDA)effect size(LEfSe)method found that major response patterns of soil bacteria to altered precipitation were resource-limited and drought-tolerant populations.In addition,increasing precipitation greatly promoted inter-species competition,while decreasing precipitation highly facilitated inter-species cooperation.These changes in species interaction can promote different distribution ratios of bacterial populations under different precipitation conditions.In structural equation model(SEM)analysis,with changes in precipitation,plant growth characteristics were found to be drivers of soil bacterial community composition,while soil properties were not.In conclusion,our results indicated that in desert grassland ecosystem,the sensitive of soil rare bacteria to altered precipitation was stronger than that of dominant taxa,which may be related to the ecological strategy of bacteria,species interaction,and precipitation-induced variations of plant growth characteristics.展开更多
The practice and research of ecological civilization is a focus of current planning and design,as well as a scientific strategy under the current situation of resource constraint,environmental degradation and ecosyste...The practice and research of ecological civilization is a focus of current planning and design,as well as a scientific strategy under the current situation of resource constraint,environmental degradation and ecosystem degradation.Urban elements such as buildings,green land,farmland,water systems and mountains can be connected by ecological corridors into a green ecological system design.At present,many ecological and environmental problems,such as urban heat island effect,fog and haze,automobile exhaust have a negative effect on the construction of social ecological environment.In order to build a new modern city with prosperous economy,beautiful environment and social civilization,scientific and efficient ecological corridors should be designed to improve the environmental quality of the eco-city,and promote the construction and development of ecological civilization and green cities.Based on the relevant research and specific practices of ecological corridors at home and abroad,combine the needs of the planning and construction of the Yuzhong Ecological Innovation City,and discuss on the connotation and characteristics of ecological corridors,and discuss the key elements of ecological corridor planning.This article will take the ecological corridor planning of Yuzhong Eco-Innovation City as an example.We design ecological corridor based on field investigation,literature and geographic information system..The planning and design of the ecological corridor in the planning area proposed in this paper can provide positive suggestion on the planning and design of the ecological corridor in other ecological innovation cities.展开更多
Current ecosystem models used to simulate global terrestrial carbon balance generally suggest that terrestrial landscapes are stable and mature,but terrestrial net primary productivity(NPP)data estimated without accou...Current ecosystem models used to simulate global terrestrial carbon balance generally suggest that terrestrial landscapes are stable and mature,but terrestrial net primary productivity(NPP)data estimated without accounting for disturbances in species composition,environment,structure,and ecological characteristics will reduce the accuracy of the global carbon budget.Therefore,the steady-state assumption and neglect of elevation-related changes in forest NPP is a concern.The Qilian Mountains are located in continental climate zone,and vegetation is highly sensitive to climate change.We quantified aboveground biomass(AGB)and aboveground net primary productivity(ANPP)sequences at three elevations using field-collected tree rings of Picea crassifolia in Qilian Mountains of Northwest China.The results showed that(1)There were significant differences between AGB and ANPP at the three elevations,and the growth rate of AGB was the highest at the low elevation(55.99 t ha^(–1)10a^(–1)).(2)There are differences in the response relationship between the ANPP and climate factors at the three elevations,and drought stress is the main climate signal affecting the change of ANPP.(3)Under the future climate scenario,drought stress intensifies,and the predicted decline trend of ANPP at the three elevations from mid-century to the end of this century is–0.025 t ha^(–1)10a^(–1),respectively;–0.022 t ha^(–1)10a^(–1);At–0.246 t ha^(–1)10a^(–1),the level of forest productivity was significantly degraded.The results reveal the elevation gradient differences in forest productivity levels and provide key information for studying the carbon sink potential of boreal forests.展开更多
Short-circuiting flow is an important secondary flow in gas cyclones, which has a negative impact on the separation performance. To improve the understanding of the short-circuiting flow and guide the optimization of ...Short-circuiting flow is an important secondary flow in gas cyclones, which has a negative impact on the separation performance. To improve the understanding of the short-circuiting flow and guide the optimization of gas cyclones, this paper presents a numerical study of a cyclone using computational fluid dynamics. Based on the steady flow field, three methods were adopted to investigate the formation mechanism and characteristics of the short-circuiting flow and particles. The temporal variation of the tracer species concentration distribution reveals that the formation mechanism of the short-circuiting flow is the squeeze between the airflows entering the annular space of the gas cyclone at different times. The short-circuiting flow region, distinguished through the spatial distribution of the moments of age, is characterized by a small mean age and a large coefficient of variation. The proportion of the short-circuiting particles increases with the increase of the inlet velocity only for small particles. But with the increase of particle size, the proportion of the short-circuiting particles decreases faster at higher inlet velocities, resulting in significant differences in collection efficiency curves.展开更多
Most terrestrial models synchronously calculate net primary productivity(NPP)using the input climate variable,without the consideration of time-lag effects,which may increase the uncertainty of NPP simulation.Based on...Most terrestrial models synchronously calculate net primary productivity(NPP)using the input climate variable,without the consideration of time-lag effects,which may increase the uncertainty of NPP simulation.Based on Normalized Difference Vegetation Index(NDVI)and climate data,we used the time lag cross-correlation method to investigate the time-lag effects of temperature,precipitation,and solar radiation in different seasons on NDVI values.Then,we selected the Carnegie-Ames-Stanford approach(CASA)model to estimate the NPP of China from 2002 to 2017.The results showed that the response of vegetation growth to climate factors had an obvious lag effect,with the longest time lag in solar radiation and the shortest time lag in temperature.The time lag of vegetation to the climate variable showed great tempo-spatial heterogeneities among vegetation types,climate types,and vegetation growth periods.Based on the validation using eddy covariance data,the results showed that the simulation accuracy of the CASA model considering the time-lag effects was effectively improved.By considering the time-lag effects,the average total amount of NPP modeled by CASA during 2001-2017 in China was 3.977 PgC a^(−1),which is 11.37%higher than that of the original model.This study highlights the importance of considering the time lag for the simulation of vegetation growth,and provides a useful tool for the improvement of the vegetation productivity model.展开更多
The rural social space quality is an important indicator to measure the living standard and thinking ideas and so forth of rural residents in a certain region.In this paper,213 administrative villages in Longxi County...The rural social space quality is an important indicator to measure the living standard and thinking ideas and so forth of rural residents in a certain region.In this paper,213 administrative villages in Longxi County of the Loess Hilly Area,China are taken as evaluation units to construct the evaluation model of the rural social space quality.This paper deeply analyzed the variation patterns and their formation mechanism of the rural social space quality at a village scale,and proposed a governance model based on the rural social space quality.The results show that:(1)the social space quality levels of individual administrative villages show a gradually decreasing trend from the township seats to outward.The eastern part of Longxi County has a relatively high education level and living standard,and the western part has a relatively high population stability level and income level.(2)The rural social space quality is mainly in a ring structure,supplemented by the interlaced structure.The core area is the towns and their surrounding areas,while the transition area,marginal area,and other areas are expanded around the core area.(3)Social forces and spatial effects jointly shape the variation of the rural social space quality.Social organizations provide a driving force for the allocation of elements,and interweaving with the spatial effects lead to the differences in the social space quality.(4)The governance models of the rural social space quality are constructed based on the principles of retaining the rural“people”,optimizing the rural“land”,and developing the rural“industry”,so as to improve the rural centripetal force,core force,inner thrust,and source power.展开更多
The satellite-based water vapor stable isotope measurements have been widely used in modern hydrological and atmospheric studies.Their use is important for arid areas where the precipitation events are limited,and bel...The satellite-based water vapor stable isotope measurements have been widely used in modern hydrological and atmospheric studies.Their use is important for arid areas where the precipitation events are limited,and below-cloud evaporation is strong.This study presents the spatial and temporal characteristics of water vapor isotopologue across the Tianshan Mountains in arid central Asia using the NASAAura Tropospheric Emission Spectrometer(TES).The near-surface water vapor stable isotopes are enriched in summer and depleted in winter,consistent with the seasonality of precipitation isotopes.From the surface to 200 hPa,the isotope values in water vapor show a decreasing trend as the atmospheric pressure decreases and elevation rises.The vapor isotope values in the lower atmosphere in the southern basin of the Tianshan Mountains are usually higher than that in the northern basin,and the seasonal difference in vapor isotopes is slightly more significant in the southern basin.In addition,bottom vapor isotopologue in summer shows a depletion trend from west to east,consistent with the rainout effect of the westerly moisture path in central Asia.The isotopic signature provided by the TES is helpful to understand the moisture transport and below-cloud processes influencing stable water isotopes in meteoric water.展开更多
The loess accumulation process has great potential to record patterns of atmospheric circulation change,paleoclimate,and paleoenvironmental evolution.South-eastern Xizang is a climatically sensitive region and here,we...The loess accumulation process has great potential to record patterns of atmospheric circulation change,paleoclimate,and paleoenvironmental evolution.South-eastern Xizang is a climatically sensitive region and here,we analyze a loess profile at Ranwu in order to explore the processes and interactions of dust transport and paleoclimate evolution in the region.Based on parametric grain size end-member analysis,optically stimulated luminescence(OSL)dating,and environmental proxies we show that the Ranwu loess profile comprises five end members(EMs).EM1 represents the fine silt fraction transported by high-altitude westerly winds over long distances;EM2 represents the medium silt fraction accumulated by glacier winds;EM3 is the coarse silt fraction transported by local dust storms under the action of strong glacier winds;EM4 represents the very fine sand fraction transported by strong local dust storms,different wind strengths controls the relative proportion of EM3 and EM4 over time.EM5 is the coarse sand fraction formed from the product of strong weathering of gravels.OSL dating shows loess sedimentation at Ranwu started around 11.16 ka.The prevailing climate was generally warm and wet between 11.6 and 4.2 ka,with four cooling events at 10.50,9.18,7.85,and 6.37 ka.Extensive paleosol development between 8.2 and 4.2 ka,a change to dry and cold climate conditions was favorable for loess formation after 4.2 ka.The palaeoenvironmental changes and abrupt climate events recorded in the Ranwu loess sequence are consistent with Holocene global environmental changes.展开更多
Due to rapid socio-economic development and urban-rural integration,the rural population is increasingly moving away from the primary industry,leading to a noticeable transformation of rural farmland use.This paper an...Due to rapid socio-economic development and urban-rural integration,the rural population is increasingly moving away from the primary industry,leading to a noticeable transformation of rural farmland use.This paper analyzed the changes in farmland use and the mechanisms in 213 villages of Longxi county,China in 2020,using multiple linear regression models,based on the aforementioned situation.Analysis revealed main findings:(1)Male and young and middle-aged emigration levels are concentrated in areas with higher and lower values,the emigration of talent is more evenly distributed.Overall,male emigration rates were high in all directions and low in the central area,whereas the young and middle-aged emigration rates exhibited a pattern of high loss in the north and south extremes,and low loss in the central area.The emigration of talent demonstrated a pattern of low losses to the east and high losses to the west of the G30 national highway.(2)Primary farmland use behavior was self-cultivation,then abandonment and finally transfer,with over 60%of the total area in 179 villages used for self-cultivation compared to less than 5%in 164 villages allocated for transfer,while less than 30%of the area in 179 villages was abandoned.(3)Significant differences were observed in the factors that influenced various farmland use behaviors,emigration of male,young and middle-aged and talent were the common influencing factors observed among all three types of farmland uses.The loss of males,young and middle-aged had a significant association with reduced self-cultivation while the emigration of talent led to an increase in self-cultivation use.Increased emigration of all three population constituencies significantly increased farmland transfer and abandonment.The conclusions carry significant theoretical and practical implications for enhancing the coordination of rural human-land relationships and improvement of the understanding of the relationship between population migration and farmland use.展开更多
The construction of rural life circle has an essential impact on the change of rural social space.Analyzing the adaptation relationship between the two can be a new content in the study of “physical-social” space.Us...The construction of rural life circle has an essential impact on the change of rural social space.Analyzing the adaptation relationship between the two can be a new content in the study of “physical-social” space.Using social behavior as a link,we construct a logical relationship framework between rural life circle and social space.Based on the survey data of Baijia village in the loess hilly region,this paper analyzes the characteristics and adaptability of the two and discusses preliminary ideas of life circle reorganization and social space reconstruction.The study results are as follows:(1) Based on the location of four types of service facilities and the travel mode of villagers,two life circles of 15 min and 25 min have been formed in Baijia village.The rural social spaces such as communicative behavior space,health seeking behavior space,leisure behavior space,and consumption behavior space show a specific concentric circle structure and unique hierarchical structure.(2) The analysis of the adaptation between them shows that the 15 min life circle in Baijia village has a high level of adaptation to communicative and leisure behavior spaces.It plays a positive feedback role in the construction of social space.However,it has a low level of adaptability to the space of health seeking and consumption behavior spaces and has a negative feedback effect on the construction of social space.The 25 min life circle is the opposite.(3) The reorganization of facility layout,hierarchical structure,and service functions in the village life circle will lead to changes in the range,frequency,and purpose of villagers’ behavioral activities,resulting in a new social spatial pattern.These findings are important for formulating village development and construction plans,improving the settlement habitat,and reconstructing the order of social life.展开更多
Quantitative assessments of the impacts of climate change and anthropogenic activities on runoff help us to better understand the mechanisms of hydrological processes.This study analyzed the dynamics of mountainous ru...Quantitative assessments of the impacts of climate change and anthropogenic activities on runoff help us to better understand the mechanisms of hydrological processes.This study analyzed the dynamics of mountainous runoff in the upper reaches of the Shiyang River Basin(USRB)and its sub-catchments,and quantified the impacts of climate change and human activities on runoff using the improved double mass curve(IDMC)method,which comprehensively considers the effects of precipitation and evapotranspiration on runoff,instead of only considering precipitation as before.The results indicated that the annual runoff depth in the USRB showed a slightly increased trend from 1961 to 2018,and sub-catchments were increased in the west and decreased in the east.The seasonal distribution pattern of runoff depth in the USRB and its eight sub-catchments all showed the largest in summer,followed by autumn and spring,and the smallest in winter with an increasing trend.Quantitative assessment results using the IDMC method showed that the runoff change in the USRB is more significantly affected by climate change,however,considerable differences are evident in sub-catchments.This study further developed and improved the method of runoff attribution analysis conducted at watershed scale,and these results will contribute to the ecological protection and sustainable utilization of water resources in the USRB and similar regions.展开更多
基金supported by the National Natural Science Foundation of China(42161007)the Scientific Research Program for Higher Education Institutions of Gansu Province(2021B-081)the Natural Science Foundation of Gansu Province(22JR5RA074).
文摘The isotope composition in precipitation has been widely considered as a tracer of monsoon activity.Compared with the coastal region,the monsoon margin usually has limited precipitation with large fluctuation and is usually sensitive to climate change.The water resource management in the monsoon margin should be better planned by understanding the composition of precipitation isotope and its influencing factors.In this study,the precipitation samples were collected at five sampling sites(Baiyin City,Kongtong District,Maqu County,Wudu District,and Yinchuan City)of the monsoon margin in the northwest of China in 2022 to analyze the characteristics of stable hydrogen(δD)and oxygen(δ18O)isotopes.We analyzed the impact of meteorological factors(temperature,precipitation,and relative humidity)on the composition of precipitation isotope at daily level by regression analysis,utilized the Hybrid Single-Particle Lagrangian Integrated Trajectory(HYSPLIT)-based backward trajectory model to simulate the air mass trajectory of precipitation events,and adopted the potential source contribution function(PSCF)and concentration weighted trajectory(CWT)to analyze the water vapor sources.The results showed that compared with the global meteoric water line(GMWL),the slope of the local meteoric water line(LMWL;δD=7.34δ^(18)O-1.16)was lower,indicating the existence of strong regional evaporation in the study area.Temperature significantly contributed toδ18O value,while relative humidity had a significant negative effect onδ18O value.Through the backward trajectory analysis,we found eight primary locations that were responsible for the water vapor sources of precipitation in the study area,of which moisture from the Indian Ocean to South China Sea(ITSC)and the western continental(CW)had the greatest influence on precipitation in the study area.The hydrogen and oxygen isotopes in precipitation are significantly influenced by the sources and transportation paths of air mass.In addition,the results of PSCF and CWT analysis showed that the water vapor source areas were primarily distributed in the south and northwest direction of the study area.
基金supported by the National Natural Science Foundation of China(Grant Nos.41761047,41861040 and 41861034).
文摘Understanding the hydrogen and oxygen stable isotope composition and characteristics of different water bodies in soil-plant-atmosphere continuum is of significance for revealing regional hydrological processes and water cycle mechanisms.In this study,we analyzed the stable isotopic composition,relationship and indicative significance of precipitation,soil water(0~100 cm depth)and xylem water of Qinghai spruce(Picea crassifolia)forest in the eastern Qilian Mountains,and explored the circulation process among different water bodies.The results show that the stable isotopes of precipitation vary greatly during the entire observation period.The values ofδ2H andδ^(18)O in the precipitation in the warm season are richer than those in the cold season,and the slope and intercept of local meteoric water line(LMWL,δ2H=6.79δ18O+7.13)are both smaller than global meteoric water line(GMWL,δ2H=8.17δ18O+10.56).The stable isotopes of soil water at different depths underwent different degrees of evaporative fractionation,and theδ18O andδ2H of shallow soil water varied greatly,while the deep soil water tended to be similar.The topsoil(0~10 cm)can respond quickly to precipitation,and the response of the deep soil has a time lag.In the whole growing season,0~30 cm and 60~100 cm soil water are the main water sources of Qinghai spruce.The water source of Qinghai spruce was from all soil layers in May and September,mainly from the shallow soil layer(0~30 cm)in August and October,and mainly from the deep soil layer(60~100 cm)in June and July.
基金the Natural Science Foundation of China(41561046)Chinese-German Centre(Sino-German Mobility M-0069)the German Research Foundation(DFG)(ZA 1068/4-1)。
文摘Desert rhizoliths are generally found as weathered,broken and scattered samples on dune field surface,but rarely insitu in their initial states buried under the soil of desert in the Badain Jaran Desert,northwest China.This study off ers an assessment of the morphological,mineralogical,and chemical properties of intact and in-situ rhizoliths found in soils of swales and depressions among dune chains.The characteristics of these rare and precious objects were assessed using optical polarizing microscopy,cathodoluminescence,scanning electronic microscopy,radiocarbon dating,and stable isotopic analyses,providing the opportunity for discussion of the rhizolith formation mechanisms and associated environmental conditions.Field and laboratory investigations showed that the in-situ intact rhizoliths were formed only in the places where Artemisia shrubs are living,and the remaining root relicts within rhizoliths belong to this species.The spatial distribution of rhizoliths also suggested that low topographic positions on a landscape provided soil moisture,and redox environments favored rhizolith formation.A semi-closed redox environment in the subsoil at swales and depressions,where water is always present,along with the sandy soil texture,facilitated fast water percolation to deeper depths and condensation.Such a soil environment not only provides water for Artemisia growth,but also for the weathering of minerals such as felspars and calcite from primary carbonates,and for the decomposition of root relicts.Furthermore,harsh climatic conditions,such as strong winds and solar radiation,led to water evaporation through dead root channels and triggered the calcification along the root relicts.The entrapped lithogenic carbonates and to a lesser extent the decomposition of Artemisia roots provided the carbon sources for the rhizoliths formation,while the weathering of soil minerals,particularly feldspars and carbonates,was the main source of Ca.Rhizoliths in the Badain Jaran desert formed relatively quickly,probably over a few soil drying episodes.This led to the entrapment of a large quantity of lithogenic carbonates(more than 90%of carbon)within rhizolith cement.The re-dissolution of the entrapped lithogenic carbonates in rhizolith tubes should be taken into account in the paleoenvironmental interpretation ofC ages,the latter suggesting that rhizoliths formed during the Holocene(~2053 years cal BP,based on root organic relicts).
基金the National Natural Science Foundation of China(41867030,41971036)the key Natural Science Foundation of Gansu Province(23JRRA698)+2 种基金the key Research and Development Program of Gansu Province(22YF7NA122)the Oasis Scientific Research achievements Breakthrough Action Plan Project of Northwest normal University(NWNU-LZKX-202302)the cultivation Plan Project of the Major(key)Project of Northwest normal University.
文摘Climate change is the dominant factor affecting the hydrological process, it is of great significance to simulate and predict its influence on water resources management, socio-economic activities, and sustainable development in the future. In this paper, the Xiying River Basin was taken as the study area, China Atmospheric Assimilation Driven Data Set(CMADS) and observation data from the Jiutiaoling station were used to simulate runoff of the SWAT model and calibrate and verify model parameters. On this basis, runoff change of the basin under the future climate scenario of CMIP6 was predicted. Our research shows that:(1) The contribution rates of climate change and human activities to runoff increase of the Xiying River are 89.17% and 10.83%, respectively. Climate change is the most important factor affecting runoff change of the Xiying River.(2) In these three different emission scenarios of SSP1-2.6, SSP2-4.5 and SSP5-8.5 in CMIP6 climate model, the average temperature increased by0.61, 1.09 and 1.74 C, respectively, in the Xiying River Basin from 2017 to 2050. Average precipitation increased by 14.36, 66.88, and 142.73 mm, respectively, and runoff increased by 15, 24, and 35 million m3, respectively.The effect of climate change on runoff will continue to deepen in the future.
基金supported by the National Natural Science Foundation of China(Project No.41807448)。
文摘Identifying geochemical characteristics of aeolian sands on the Qinghai-Tibet Plateau(QTP)is essential for understanding the relationship between earth surface processes and paleoclimatic fluctuations in the region.Here,we present new geochemical data which provides insight to the sedimentary environment of aeolian sands in the Dinggye region,southern Tibet.We sampled aeolian dune sands in a variety of settings,and determined grain size and concentration of major oxides and trace elements in the fine and coarse fractions.Results show that aeolian sediments are dominated by fine and medium sands,with a single-peaked frequency curve and a 3-stage probability cumulative curve.The fine and coarse fractions exhibit considerable heterogeneity in elemental concentrations and ratios and upper continental crust-normalized(UCC)distribution.The geochemical evidence indicates that wind dynamic sorting is responsible for the differentiation between fine and coarse fractions in different types of aeolian sand,rather than sediment provenance.Additionally,fine-fraction sediments are well dispersed and can be differentiated from the coarse fraction,suggesting that they contain more environmental information.Multidimensional scale(MDS)and principal component analysis(PCA)of commonly used tracer elements show that flood plain sediments are the sand source for mobile dunes and nebkhas,and lakeshore sediments are the sand source for climbing sand sheets.
基金supportedby the National Natural Science Foundation of China(41771035,42071047)。
文摘In order to cope with drought and water shortages,the working people in the arid areas of Northwest China have developed a drought-resistant planting method,namely,gravel-sand mulching,after long-term agricultural practices.To understand the effects of gravel-sand mulching on soil water evaporation,we selected Baifeng peach(Amygdalus persica L.)orchards in Northwest China as the experimental field in 2021.Based on continuously collected soil water stable isotopes data,we evaluated the soil evaporation loss rate in a gravel-sand mulching environment using the line-conditioned excess(lc-excess)coupled Rayleigh fractionation model and Craig-Gordon model.The results show that the average soil water content in the plots with gravel-sand mulching is 1.86%higher than that without gravel-sand mulching.The monthly variation of the soil water content is smaller in the plots with gravel-sand mulching than that without gravel-sand mulching.Moreover,the average lc-excess value in the plots without gravel-sand mulching is smaller.In addition,the soil evaporation loss rate in the plots with gravel-sand mulching is lower than that in the plots without gravel-sand mulching.The lc-excess value was negative for both the plots with and without gravel-sand mulching,and it has good correlation with relative humidity,average temperature,input water content,and soil water content.The effect of gravel-sand mulching on soil evaporation is most prominent in August.Compared with the evaporation data of similar environments in the literature,the lc-excess coupled Rayleigh fractionation model is better.Stable isotopes evidence shows that gravel-sand mulching can effectively reduce soil water evaporation,which provides a theoretical basis for agricultural water management and optimization of water-saving methods in arid areas.
基金This study was funded by the National Natural Science Foundation of China(41771035,42071047)the Foundation for Distinguished Young Scholars of Gansu Province(20JR10RA112)+1 种基金the Northwest Normal University(NWNU-LKZD2021-04)the Department of Education of Gansu Province:"Innovation Star"Program of Excellent Postgraduates(2021CXZX-217).
文摘Caragana korshinskii Kom.and Tamarix ramosissima Ledeb.are pioneer shrubs for water and soil conservation,and for windbreak and sand fixation in arid and semi-arid areas.Understanding the water use characteristics of different pioneer shrubs at different ages is of great importance for their survival when extreme rainfall occurs.In recent years,the stable isotope tracing technique has been used in exploring the water use strategies of plants.However,the widespreadδ^(2)H offsets of stem water from its potential sources result in conflicting interpretations of water utilization of plants in arid and semi-arid areas.In this study,we used three sets of hydrogen and oxygen stable isotope data(δ^(2)H andδ^(18)O,correctedδ^(2)H_c1 based on SW-excess andδ^(18)O,and correctedδ^(2)H_c2 based on−8.1‰andδ^(18)O)as inputs for the MixSIAR model to explore the water use characteristics of C.korshinskii and T.ramosissima at different ages and in response to rainfall.The results showed thatδ^(2)H_c1 andδ^(18)O have the best performance,and the contribution rate of deep soil water was underestimated because ofδ^(2)H offset.During the dry periods,C.korshinskii and T.ramosissima at different ages both obtained mostly water from deeper soil layers.After rainfall,the proportions of surface(0-10 cm)and shallow(10-40 cm)soil water for C.korshinskii and T.ramosissima at different ages both increased.Nevertheless,there were different response mechanisms of these two plants for rainfall.In addition,C.korshinskii absorbed various potential water sources,while T.ramosissima only used deep water.These flexible water use characteristics of C.korshinskii and T.ramosissima might facilitate the coexistence of plants once extreme rainfall occurs.Thus,reasonable allocation of different plants may be a good vegetation restoration program in western Chinese Loess Plateau.
基金the Science and Technology Planning Project of Gansu Province,China(18JR4RA002)the Qilian Mountains Eco-Environment Research Center in Gansu Province,Northwest Institute of Eco-Environment and Resources,Chinese Academy of Sciences(QLS202002).
文摘Altitude affects leaf stoichiometry by regulating temperature and precipitation,and influencing soil properties in mountain ecosystems.Leaf carbon concentration(C),leaf nitrogen concentration(N),leaf phosphorous concentration(P),and their stoichiometric ratios of Leontopodium lentopodioides(Willd.)Beauv.,a widespread species in degraded grasslands,were investigated to explore its response and adaptation strategy to environmental changes along four altitude gradients(2500,3000,3500,and 3800 m a.s.l.)on the northeastern Qinghai-Tibetan Plateau(QTP),China.The leaf C significantly varied but without any clear trend with increasing altitude.Leaf N showed an increasing trend,and leaf P showed a little change with increasing altitude,with a lower value of leaf P at 3500 m than those at other altitudes.Similarity,leaf C:P and N:P exhibited a little change with increasing altitude,which both had greater values at 3500 m than those at other altitudes.However,leaf C:N exhibited a decreasing trend with increasing altitude.Soil NH^(+)_(4)-N,soil pH,soil total phosphorus(STP),mean annual temperature(MAT),and mean annual precipitation(MAP)were identified as the main factors driving the variations in leaf stoichiometry of L.lentopodioides across all altitudes,with NH^(+)_(4)-N alone accounting for 50.8%of its total variation.Specifically,leaf C and N were mainly controlled by MAT,soil pH,and NH^(+)_(4)-N,while leaf P by MAP and STP.In the study area,it seems that the growth of L.lentopodioides may be mainly limited by STP.The results could help to strengthen our understanding of the plasticity of plant growth to environmental changes and provide new information on global grassland management and restoration.
基金supported by the National Natural Science Foundation of China (41761043, 41201196)the Youth Teacher Scientific Capability Promoting Project of Northwest Normal University, China (NWNU-LKQN2020-06, NWNU-LKQN-17-7)the Key Research and Development Program of Gansu Province, China (20YF3FA042)
文摘Variations of precipitation have great impacts on soil carbon cycle and decomposition of soil organic matter.Soil bacteria are crucial participants in regulating these ecological processes and vulnerable to altered precipitation.Studying the impacts of altered precipitation on soil bacterial community structure can provide a novel insight into the potential impacts of altered precipitation on soil carbon cycle and carbon storage of grassland.Therefore,soil bacterial community structure under a precipitation manipulation experiment was researched in a semi-arid desert grassland in Chinese Loess Plateau.Five precipitation levels,i.e.,control,reduced and increased precipitation by 40%and 20%,respectively(referred here as CK,DP40,DP20,IP40,and IP20)were set.The results showed that soil bacterial alpha diversity and rare bacteria significantly changed with altered precipitation,but the dominant bacteria and soil bacterial beta diversity did not change,which may be ascribed to the ecological strategy of soil bacteria.The linear discriminate analysis(LDA)effect size(LEfSe)method found that major response patterns of soil bacteria to altered precipitation were resource-limited and drought-tolerant populations.In addition,increasing precipitation greatly promoted inter-species competition,while decreasing precipitation highly facilitated inter-species cooperation.These changes in species interaction can promote different distribution ratios of bacterial populations under different precipitation conditions.In structural equation model(SEM)analysis,with changes in precipitation,plant growth characteristics were found to be drivers of soil bacterial community composition,while soil properties were not.In conclusion,our results indicated that in desert grassland ecosystem,the sensitive of soil rare bacteria to altered precipitation was stronger than that of dominant taxa,which may be related to the ecological strategy of bacteria,species interaction,and precipitation-induced variations of plant growth characteristics.
文摘The practice and research of ecological civilization is a focus of current planning and design,as well as a scientific strategy under the current situation of resource constraint,environmental degradation and ecosystem degradation.Urban elements such as buildings,green land,farmland,water systems and mountains can be connected by ecological corridors into a green ecological system design.At present,many ecological and environmental problems,such as urban heat island effect,fog and haze,automobile exhaust have a negative effect on the construction of social ecological environment.In order to build a new modern city with prosperous economy,beautiful environment and social civilization,scientific and efficient ecological corridors should be designed to improve the environmental quality of the eco-city,and promote the construction and development of ecological civilization and green cities.Based on the relevant research and specific practices of ecological corridors at home and abroad,combine the needs of the planning and construction of the Yuzhong Ecological Innovation City,and discuss on the connotation and characteristics of ecological corridors,and discuss the key elements of ecological corridor planning.This article will take the ecological corridor planning of Yuzhong Eco-Innovation City as an example.We design ecological corridor based on field investigation,literature and geographic information system..The planning and design of the ecological corridor in the planning area proposed in this paper can provide positive suggestion on the planning and design of the ecological corridor in other ecological innovation cities.
基金The CAS“Light of West China”Program,No.2020XBZG-XBQNXZ-ACultivation Program of 2022 Major Scientific Research Project of Northwest Normal University,No.WNU-LKZD2022-04National Natural Science Foundation of Gansu,No.20JR10RA093。
文摘Current ecosystem models used to simulate global terrestrial carbon balance generally suggest that terrestrial landscapes are stable and mature,but terrestrial net primary productivity(NPP)data estimated without accounting for disturbances in species composition,environment,structure,and ecological characteristics will reduce the accuracy of the global carbon budget.Therefore,the steady-state assumption and neglect of elevation-related changes in forest NPP is a concern.The Qilian Mountains are located in continental climate zone,and vegetation is highly sensitive to climate change.We quantified aboveground biomass(AGB)and aboveground net primary productivity(ANPP)sequences at three elevations using field-collected tree rings of Picea crassifolia in Qilian Mountains of Northwest China.The results showed that(1)There were significant differences between AGB and ANPP at the three elevations,and the growth rate of AGB was the highest at the low elevation(55.99 t ha^(–1)10a^(–1)).(2)There are differences in the response relationship between the ANPP and climate factors at the three elevations,and drought stress is the main climate signal affecting the change of ANPP.(3)Under the future climate scenario,drought stress intensifies,and the predicted decline trend of ANPP at the three elevations from mid-century to the end of this century is–0.025 t ha^(–1)10a^(–1),respectively;–0.022 t ha^(–1)10a^(–1);At–0.246 t ha^(–1)10a^(–1),the level of forest productivity was significantly degraded.The results reveal the elevation gradient differences in forest productivity levels and provide key information for studying the carbon sink potential of boreal forests.
基金supported by the National Key Research and Development Project,China(Grant No.2018YFC1903701)the Key Consulting Research Projects of the Chinese Academy of Engineer-ing(Grant No.2021-XZ-7)Fundamental Research Funds for the Central Universities(Grant No.lzujbky-2021-71).
文摘Short-circuiting flow is an important secondary flow in gas cyclones, which has a negative impact on the separation performance. To improve the understanding of the short-circuiting flow and guide the optimization of gas cyclones, this paper presents a numerical study of a cyclone using computational fluid dynamics. Based on the steady flow field, three methods were adopted to investigate the formation mechanism and characteristics of the short-circuiting flow and particles. The temporal variation of the tracer species concentration distribution reveals that the formation mechanism of the short-circuiting flow is the squeeze between the airflows entering the annular space of the gas cyclone at different times. The short-circuiting flow region, distinguished through the spatial distribution of the moments of age, is characterized by a small mean age and a large coefficient of variation. The proportion of the short-circuiting particles increases with the increase of the inlet velocity only for small particles. But with the increase of particle size, the proportion of the short-circuiting particles decreases faster at higher inlet velocities, resulting in significant differences in collection efficiency curves.
基金National Natural Science Foundation of China,No.42161058The State Key Laboratory of Cryospheric Science,No.SKLCS-ZZ-2022The West Light Foundation of the Chinese Academy of Sciences。
文摘Most terrestrial models synchronously calculate net primary productivity(NPP)using the input climate variable,without the consideration of time-lag effects,which may increase the uncertainty of NPP simulation.Based on Normalized Difference Vegetation Index(NDVI)and climate data,we used the time lag cross-correlation method to investigate the time-lag effects of temperature,precipitation,and solar radiation in different seasons on NDVI values.Then,we selected the Carnegie-Ames-Stanford approach(CASA)model to estimate the NPP of China from 2002 to 2017.The results showed that the response of vegetation growth to climate factors had an obvious lag effect,with the longest time lag in solar radiation and the shortest time lag in temperature.The time lag of vegetation to the climate variable showed great tempo-spatial heterogeneities among vegetation types,climate types,and vegetation growth periods.Based on the validation using eddy covariance data,the results showed that the simulation accuracy of the CASA model considering the time-lag effects was effectively improved.By considering the time-lag effects,the average total amount of NPP modeled by CASA during 2001-2017 in China was 3.977 PgC a^(−1),which is 11.37%higher than that of the original model.This study highlights the importance of considering the time lag for the simulation of vegetation growth,and provides a useful tool for the improvement of the vegetation productivity model.
基金National Natural Science Foundation of China,No.41961033Natural Science Foundation of Gansu Province,No.20JR5RA519The Graduate Research Funding Project of Northwest Normal University in 2021,No.2021KYZZ01039。
文摘The rural social space quality is an important indicator to measure the living standard and thinking ideas and so forth of rural residents in a certain region.In this paper,213 administrative villages in Longxi County of the Loess Hilly Area,China are taken as evaluation units to construct the evaluation model of the rural social space quality.This paper deeply analyzed the variation patterns and their formation mechanism of the rural social space quality at a village scale,and proposed a governance model based on the rural social space quality.The results show that:(1)the social space quality levels of individual administrative villages show a gradually decreasing trend from the township seats to outward.The eastern part of Longxi County has a relatively high education level and living standard,and the western part has a relatively high population stability level and income level.(2)The rural social space quality is mainly in a ring structure,supplemented by the interlaced structure.The core area is the towns and their surrounding areas,while the transition area,marginal area,and other areas are expanded around the core area.(3)Social forces and spatial effects jointly shape the variation of the rural social space quality.Social organizations provide a driving force for the allocation of elements,and interweaving with the spatial effects lead to the differences in the social space quality.(4)The governance models of the rural social space quality are constructed based on the principles of retaining the rural“people”,optimizing the rural“land”,and developing the rural“industry”,so as to improve the rural centripetal force,core force,inner thrust,and source power.
基金This research was supported by the National Natural Science Foundation of China(Nos.41971034 and 41701028)the Foundation for Distinguished Young Scholars of Gansu Province(No.20JR10RA112)the Northwest Normal University(No.NWNU LKZD2021-04)。
文摘The satellite-based water vapor stable isotope measurements have been widely used in modern hydrological and atmospheric studies.Their use is important for arid areas where the precipitation events are limited,and below-cloud evaporation is strong.This study presents the spatial and temporal characteristics of water vapor isotopologue across the Tianshan Mountains in arid central Asia using the NASAAura Tropospheric Emission Spectrometer(TES).The near-surface water vapor stable isotopes are enriched in summer and depleted in winter,consistent with the seasonality of precipitation isotopes.From the surface to 200 hPa,the isotope values in water vapor show a decreasing trend as the atmospheric pressure decreases and elevation rises.The vapor isotope values in the lower atmosphere in the southern basin of the Tianshan Mountains are usually higher than that in the northern basin,and the seasonal difference in vapor isotopes is slightly more significant in the southern basin.In addition,bottom vapor isotopologue in summer shows a depletion trend from west to east,consistent with the rainout effect of the westerly moisture path in central Asia.The isotopic signature provided by the TES is helpful to understand the moisture transport and below-cloud processes influencing stable water isotopes in meteoric water.
基金supported by the National Natural Science Foundation of China(Grant No.41807448).
文摘The loess accumulation process has great potential to record patterns of atmospheric circulation change,paleoclimate,and paleoenvironmental evolution.South-eastern Xizang is a climatically sensitive region and here,we analyze a loess profile at Ranwu in order to explore the processes and interactions of dust transport and paleoclimate evolution in the region.Based on parametric grain size end-member analysis,optically stimulated luminescence(OSL)dating,and environmental proxies we show that the Ranwu loess profile comprises five end members(EMs).EM1 represents the fine silt fraction transported by high-altitude westerly winds over long distances;EM2 represents the medium silt fraction accumulated by glacier winds;EM3 is the coarse silt fraction transported by local dust storms under the action of strong glacier winds;EM4 represents the very fine sand fraction transported by strong local dust storms,different wind strengths controls the relative proportion of EM3 and EM4 over time.EM5 is the coarse sand fraction formed from the product of strong weathering of gravels.OSL dating shows loess sedimentation at Ranwu started around 11.16 ka.The prevailing climate was generally warm and wet between 11.6 and 4.2 ka,with four cooling events at 10.50,9.18,7.85,and 6.37 ka.Extensive paleosol development between 8.2 and 4.2 ka,a change to dry and cold climate conditions was favorable for loess formation after 4.2 ka.The palaeoenvironmental changes and abrupt climate events recorded in the Ranwu loess sequence are consistent with Holocene global environmental changes.
基金National Natural Science Foundation of China,No.42271222Natural Science Foundation of Gansu Province,No.22JR5RA130Science and Technology Program of Gansu Province,No.22JR5RA136。
文摘Due to rapid socio-economic development and urban-rural integration,the rural population is increasingly moving away from the primary industry,leading to a noticeable transformation of rural farmland use.This paper analyzed the changes in farmland use and the mechanisms in 213 villages of Longxi county,China in 2020,using multiple linear regression models,based on the aforementioned situation.Analysis revealed main findings:(1)Male and young and middle-aged emigration levels are concentrated in areas with higher and lower values,the emigration of talent is more evenly distributed.Overall,male emigration rates were high in all directions and low in the central area,whereas the young and middle-aged emigration rates exhibited a pattern of high loss in the north and south extremes,and low loss in the central area.The emigration of talent demonstrated a pattern of low losses to the east and high losses to the west of the G30 national highway.(2)Primary farmland use behavior was self-cultivation,then abandonment and finally transfer,with over 60%of the total area in 179 villages used for self-cultivation compared to less than 5%in 164 villages allocated for transfer,while less than 30%of the area in 179 villages was abandoned.(3)Significant differences were observed in the factors that influenced various farmland use behaviors,emigration of male,young and middle-aged and talent were the common influencing factors observed among all three types of farmland uses.The loss of males,young and middle-aged had a significant association with reduced self-cultivation while the emigration of talent led to an increase in self-cultivation use.Increased emigration of all three population constituencies significantly increased farmland transfer and abandonment.The conclusions carry significant theoretical and practical implications for enhancing the coordination of rural human-land relationships and improvement of the understanding of the relationship between population migration and farmland use.
基金National Natural Science Foundation of China,No.42271222,No.42201261Natural Science Foundation of Gansu Province,No.22JR5RA130+1 种基金Major Science&Technology Project of Gansu Province,No.22ZD6WA057Young Doctoral Fund of Department of Education of Gansu Province,No.2022QB-040。
文摘The construction of rural life circle has an essential impact on the change of rural social space.Analyzing the adaptation relationship between the two can be a new content in the study of “physical-social” space.Using social behavior as a link,we construct a logical relationship framework between rural life circle and social space.Based on the survey data of Baijia village in the loess hilly region,this paper analyzes the characteristics and adaptability of the two and discusses preliminary ideas of life circle reorganization and social space reconstruction.The study results are as follows:(1) Based on the location of four types of service facilities and the travel mode of villagers,two life circles of 15 min and 25 min have been formed in Baijia village.The rural social spaces such as communicative behavior space,health seeking behavior space,leisure behavior space,and consumption behavior space show a specific concentric circle structure and unique hierarchical structure.(2) The analysis of the adaptation between them shows that the 15 min life circle in Baijia village has a high level of adaptation to communicative and leisure behavior spaces.It plays a positive feedback role in the construction of social space.However,it has a low level of adaptability to the space of health seeking and consumption behavior spaces and has a negative feedback effect on the construction of social space.The 25 min life circle is the opposite.(3) The reorganization of facility layout,hierarchical structure,and service functions in the village life circle will lead to changes in the range,frequency,and purpose of villagers’ behavioral activities,resulting in a new social spatial pattern.These findings are important for formulating village development and construction plans,improving the settlement habitat,and reconstructing the order of social life.
基金National Natural Science Foundation of China,No.42361005,No.41861034,No.41661040,No.32060373。
文摘Quantitative assessments of the impacts of climate change and anthropogenic activities on runoff help us to better understand the mechanisms of hydrological processes.This study analyzed the dynamics of mountainous runoff in the upper reaches of the Shiyang River Basin(USRB)and its sub-catchments,and quantified the impacts of climate change and human activities on runoff using the improved double mass curve(IDMC)method,which comprehensively considers the effects of precipitation and evapotranspiration on runoff,instead of only considering precipitation as before.The results indicated that the annual runoff depth in the USRB showed a slightly increased trend from 1961 to 2018,and sub-catchments were increased in the west and decreased in the east.The seasonal distribution pattern of runoff depth in the USRB and its eight sub-catchments all showed the largest in summer,followed by autumn and spring,and the smallest in winter with an increasing trend.Quantitative assessment results using the IDMC method showed that the runoff change in the USRB is more significantly affected by climate change,however,considerable differences are evident in sub-catchments.This study further developed and improved the method of runoff attribution analysis conducted at watershed scale,and these results will contribute to the ecological protection and sustainable utilization of water resources in the USRB and similar regions.
