Dynamic of Chinas cultivated land and landcover changes of its typical regions based on remote sensing data

Using the multi-temporal Landsat data and survey data of national resources, the authors studied the dynamics of cultivated land and landcover changes of typical ecological regions in China. The results of investigation showed that the whole distribution of the cultivated land shifted to Northeast and Northwest China, and as a result, the ecological quality of cultivated land dropped down. The seacoast and cultivated land in the area of Yellow River Mouth expanded by an increasing rate of 0.73 kma-1, with a depositing rate of 2.1 kma-1. The desertification area of the dynamic of Horqin Sandy Land increased from 60.02% of the total land area in1970s to 64.82% in1980s but decreased to 54.90% in early 1990s. As to the change of North Tibet lakes, the water area of the Namu Lake decreased by 38.58 km2 from year 1970 to 1988, with a decreasing rate of 2.14 km2a-1.

Interactions between Vegetation and Climatic Factors in Typical Arid and Humid Regions of China Based on NDVI

According to the distribution of arid and humid regions in China,the typical arid region (Erjina),the typical semi-arid/semi-humid region (Guanzhong basin/Loess Plateau) and the typical humid region (Poyang Lake basin) were selected as the study areas.Based on NDVI data from 1982 to 2000 and meteorological observing data of three study areas from 1981 to 2000,the interactions between vegetation NDVI and climatic factors (temperature and precipitation) in typical arid and humid regions were discussed in this study.The results showed that in the responses of vegetation to climatic factors,vegetation in the typical arid region (Erjina) was more sensitive to precipitation,while vegetation in the typical semi-arid/semi-humid region (Guanzhong basin/Loess Plateau) was more sensitive to both temperature and precipitation,and vegetation in the typical humid region (Poyang Lake basin) was more sensitive to temperature.As for effects of vegetation on climatic factors,there was a remarkable negative correlation between vegetation NDVI in the past winter and temperature in the present summer,and also a significant positive correlation between vegetation NDVI in the past winter and precipitation in the present summer.However,in the typical semi-arid/semi-humid region (Guanzhong basin/Loess Plateau),there was a significant positive correlation between vegetation NDVI in the present spring and temperature in the present summer.

Trade-off and Synergy of Rural Functions Under County Depopulation in the Typical Black Soil Region of Northeast China

As the population continues to shrink in the black soil region of Northeast China since 2000,it is critical to master the impact of population shrinkage on rural functions to realize rural revitalization and sustainable development.In this study,we focused on the impacts of depopulation on the evolution and interrelationship of rural subfunctions.Based on the rural function indexes system,the TOPSIS(Technique for Order Preference by Similarity to an Ideal Solution)method,spatial analysis method,and mathematical statistics analysis method were used to summarize the spatial and temporal characteristics of rural function development,as well as the effect of population shrinkage in the typical black soil region of Northeast China.The results showed that depopulation varied in the extent and duration between the forested region and plain areas,which both impacted the trajectories of rural subfunctions evolution.For the economic development function and ecological conservation function,the effect of continuous slight depopulation was beneficial,while the effect of rapid depopulation was adverse,which was exactly opposite to the agricultural production function.All forms of population shrinkage were conducive to the development of the social security function.With the deepening population shrinkage,depopulation mainly promoted the collaborative development between subfunctions in this study,except the relationship between agricultural production and social security function.But effects of depopulation on the interrelationship of rural subfunctions varied between the forested region and plain areas in some cases.The results provided evidence for the cognition that population shrinkage had complicated effects on rural subfunctions.

Groundwater quality and land use change in a typical karst agricultural region:a case study of Xiaojiang watershed,Yunnan

Taking the typical karst agricultural region, Xiaojiang watershed in Luxi of Yurman Province as a research unit, utilizing the groundwater quality data in 1982 and 2004, the aerial photos in 1982 and TM images in 2004, supported by the GIS, we probe into the law and the reason of its space-time change of the groundwater quality over the past 22 years in the paper. The results show： （1） There were obvious temporal and spatial changes of groundwater quality during the past 22 years. （2） Concentrations of NH4^＋, SO4^2- , NO3, NO2^-, Cl^- and the pH value, total hardness, total alkalinity increased significantly, in which NH4^2-, NO3, and NO2^- of groundwater exceeded the drinking water standards as a result of non-point pollution caused by the expansion of cultivated land and mass use of the fertilizer and pesticide. （3） Oppositely, Ca^2＋ and HCO3^- showed an obvious decline trend due to forest reduction and degradation and stony desertification. Meantime, there was a dynamic relation between the groundwater quality change and the land use change.

Dynamic influence of Holocene characteristics on vadose water in typical region of central North China Plain

In the typical region of central North China Plain, vadose sediments are Holocene sediment strata. With samples from field drillings, the study analyzes the sedimentary characteristics of vadose zone. The study takes the content of silty sand as the basis for sedimentary environment analysis, and the content of clay and sand as the sensitive indicator for sedimentary characteristics. Combining palynology analysis, the study divides vadose zone from top to bottom into diluvia oxbow lacustrine sediments, lacustrine sediments, lacustrine and swamp sediments, weak palaeohydrodynamic lacustrine sediments and alluvial sediments. Based on the sedimentary characteristics of Holocene strata, it analyzes the changes across depth of vadose zone water potential and matrix potential, obtaining the influence of vadose zone sedimentary characteristics on the migration of water in typical region of central North China Plain.

Effect of climatic change on surface environments in the typical region of Horqin Sandy Land

The town of Agura,a typical region in Horqin Sandy Land,was selected as the study area in this paper.Using 12 remote sensing images and climatic data from the past 20 years,the effects of climate change on surface environments were analyzed.The impact indices of climatic factors,along with their corresponding ranks,were used to characterize the responses of different types of surface environments to climate change.Results show that in the past 20 years,the surface environments of the study area have been deteriorating.Furthermore,there is a positive relationship between the changes in surface environments and those in climatic factors.Various climatic factors influence surface environments in different ways and at different levels.The most sensitive factor is relative humidity,followed by precipitation and evaporation.Overall,moisture is the key factor that affects the changes in surface environments of arid and semi-arid areas.

Changes of spring wind erosion based on wind erosion climate factor in the black soil region of Northeast China

The dry and windy climate and low ground cover in spring in the black soil region of Northeast China make the soil strongly affected by wind erosion,which seriously threatens the food security and ecological security of this region.In this paper,based on the daily observation data of 124 meteorological stations in study area from 1961 to 2020,seasonal and monthly wind erosion climate factor(C)in spring(March to May)were calculated by using the method proposed by the Food and Agriculture Organization of the United Nations(FAO),the wind erosion characterization in spring were systematically analyzed based on C by various statistical analysis methods.The results showed that in the past 60 years,spring wind erosion climate factor(CSp)and monthly C of the whole region and each province(region)all showed highly significant decreasing trend,but they began to show rebounded trend in the middle or late 2000s.CSp of the study area showed a significant upward trend since 2008 with an increase of 4.59(10a)^(-1).The main contributors to this upward trend are the changes of C in March and in April.For the four provinces(regions),CSp in Heilongjiang,Jilin,Liaoning and eastern Inner Mongolia all showed rebounded since 2008,2011,2008 and 2009,respectively.The rebounded trend of CSp in eastern Inner Mongolia was the most obvious with a tendency rate of 11.27(10a)^(-1),and its mutation occurred after 1984.The rebound trend of CSp in Heilongjiang Province takes the second place,with a trend rate of 4.72(10a)^(-1),but there’s no obvious time mutation characteristics.The spatial characteristics of CSpand monthly C are similar,showing decreasing characteristics centered on the typical black soil belt of Northeast China.Compared with 1961-1990,in the period from 1991 to 2020,the proportion of high value areas(CSp>35,monthly C>10)has decreased to varying degrees,while the proportion of low value areas(CSp≤10,monthly C≤4)has increased.The trends of seasonal and monthly C in 82.2%~87.7%of the stations show significant decreases at 95%confidence level.CSp is closely related to wind speed at 2m height,temperature difference,minimum temperature and precipitation in the same period,of which the correlation between CSp and wind speed is the strongest,indicating that the main control factor for CSp in the study area is wind speed,but the impact of the change of temperature and precipitation on CSp cannot be ignored.

Synergetic pathways of water-energy-carbon in ecologically vulnerable regions aiming for carbon neutrality:a case study of Shaanxi,China

Synergetic energy-water-carbon pathways are key issues to be tackled under carbon-neutral target and high-quality development worldwide,especially in ecologically vulnerable regions(EVRs).In this study,to explore the synergistic pathways in an EVR,a water-energy-carbon assessment(WECA)model was built,and the synergistic effects of water-energy-carbon were comprehensively and quantitatively analyzed under various scenarios of regional transition.Shaanxi Province was chosen as the representative EVR,and Lower challenge(LEC)and Greater challenge(GER)scenarios of zerocarbon transition were set considering the technological maturity and regional energy characteristics.The results showed that there were limited effects under the zero-carbon transition of the entire region on reducing water withdrawals and improving the water quality.In the LEC scenario,the energy demand and CO2 emissions of Shaanxi in 2060 will decrease by 70.9%and 99.4%,respectively,whereas the water withdrawal and freshwater aquatic ecotoxicity potential(FAETP)will only decrease by 8.9%and 1.6%,respectively.This could be attributed to the stronger demand for electricity in the energy demand sector caused by industrial transition measures.The GER scenario showed significant growth in water withdrawals(16.0%)and FAETP(36.0%)because of additional biomass demand.To promote the synergetic development of regional transition,EVRs should urgently promote zero-carbon technologies(especially solar and wind power technologies)between 2020 and 2060 and dry cooling technology for power generation before 2030.In particular,a cautious attitude toward the biomass energy with carbon capture and storage technology in EVRs is strongly recommended.

Changes in climate extremes in a typical glacierized region in central Eastern Tianshan Mountains and their relationship with observed glacier mass balance

As an icon of anthropogenic climate change,alpine glaciers are highly sensitive to climate change.However,there remain research gaps regarding trends in climate extremes in glacierized regions and their relationship with local glacier mass balance.In this study,these relationships and their underlying links were explored in a typical glacierized region in the Eastern Tianshan Mountains,China,from 1959 to 2018.All warm extremes exhibited increasing trends that intensified dramatically from the 1990s.Meanwhile,decreasing trends were found for all cold extremes except for the temperatures of the coldest days and coldest nights.All of the precipitation extremes demonstrated increasing trends,except for consecutive dry days and consecutive wet days.Statistically significant positive/negative correlations were detected between glacier mass balance and six warm extremes(TN90p,TX90p,SU99p,TR95p,TXx,and TNx)/four cold extremes(TN10p,TX10p,FD0,and ID0).Simulation results showed that the impact of the intensity/frequency of the warm extremes(TN90p,TX90p,SU99p,and TR95p)on glacier ablation was remarkable and the effect of the cold extremes(FD0 and ID0)on accumulation was also significant.Additionally,the increases in the intensity and frequency of most climate extremes seemed more remarkable in glacierized regions than in non-glacierized regions.Hence,studies on glacier-climate interactions should focus greater attention on the impacts of climate extremes on glacier evolution.