Effect of ground cover changes on solar radiation absorption in Three Northeastern Provinces of China

Background,aim,and scope Solar radiation is the main source of energy for terrestrial ecosystems.Small changes in the absorption of solar radiation at the ground surface can have a significant impact on the climatic environment.Natural and anthropogenic changes in ground cover are important factors affecting the absorption of solar radiation at the ground surface.This phenomenon is particularly pronounced in the mid and high latitudes.In order to quantify the inf luence of surface cover change on the absorption of solar radiation at the surface and to provide a scientific basis for changes in the climatic environment,this paper analyzed ground cover change,ground absorbed solar radiation change and the effect of ground cover change on ground absorbed solar radiation in the Three Northeastern Provinces of China from 2001 to 2018.Materials and methods In this study,the Three Northeastern Provinces of China were used as the study area.Firstly,satellite remote sensing data were used to obtain land cover data and albedo data for Aug.1st of each year in 2001,2005,2010,2015 and 2018.The albedo data were further used to calculate the absorbed solar radiation data at the ground surface.Next,the land cover data were used to count the area changes and shifts of different land classes over the five-year period.The land cover data were overlaid with the surface absorbed solar radiation data to obtain the mean and standard deviation of radiation absorption for different ground classes.The surface absorbed solar radiation data were subtracted to obtain the changes in surface absorbed solar radiation for 2001-2005,2005-2010,2010-2015 and 2015-2018.Ultimately,we used a combination of shifted changes in ground classes and changes in surface absorbed solar radiation data,with unchanged ground classes as a baseline and data such as slope orientation as an aid.We analyzed the effect of ground cover change on surface absorbed solar radiation at regional and pixel point scales.Results(1)The area of woodland and waters in the Three Northeastern Provinces of China increased and then decreased from 2001 to 2018,with an overall increase of 3.96%and 10.51%respectively.Cropland decreased and then increased,with a total decrease of 1.22%.Grassland continued to decrease,with an overall decrease of 19.36%.Building sites increased all the time,with a total increase of 11.08%.The main types of ground cover shifted were woodland,cropland and grassland.The main factors for the change in ground cover were China’s woodland protection policy and the saturation of the total woodland stock.(2)The five ground types absorb solar radiation in the order of waters>building sites>woodland>grassland>cropland.The surface absorption of solar radiation in the Songnen Plain,the Sanjiang Plain and the Songhua River Basin flowing through the Songnen Plain and the Sanjiang Plain varies significantly,by more than 25 W·m^(-2).(3)Changes in the ground cover type affected the absorption of solar radiation energy by the ground surface.There was a clear trend of interconversion between waters and cropland/grassland,cropland and woodland/grassland.In particular,the conversion of waters to both cropland and grassland radiation absorption values decreased significantly,while the opposite increased.The absolute difference between waters and cropland was a maximum of -156.66 W·m^(-2)in 2010-2015,and between waters and grassland was a maximum of 102.36 W·m^(-2) in 2005-2010.The radiative absorption values of woodland and grassland reclamation declined and conversely increased.The absolute difference between woodland and cropland was a maximum of-13.94 W·m^(-2) in 2010-2015 when woodland converted to cropland,and between grassland and cropland was a maximum of 22.36 W·m^(-2) in 2001-2005 when cropland converted to grassland,respectively.Discussion Ground cover changes in the Three Northeastern Provinces of China from 2001-2018 were inextricably linked to natural factors and the inf luence of Chinese national policies.The main inf luencing factors were China’s woodland protection policy,restoration of woodland fire sites,saturation of total woodland,optimization of cropland patterns,sanding of grassland,expansion of water conservancy projects,and urbanization expansion.There were differences in the radiation absorption characteristics of different ground cover types.This was due to the nature of the ground type itself and the regional environment.When ground cover types changed,their ability to absorb solar radiation also changed.The degree of change could be inf luenced by different ground types and different environmental factors.Different spatial scales can also produce variability.We need to consider the effects of ground cover change on the absorption of solar radiation at the surface in an integrated and comprehensive way.Conclusions The Three Northeastern Provinces of China had frequent changes in ground cover from 2001-2018,with the area of grassland decreased by almost 20%.These changes were due to natural environmental change and policies issued by China since the 21st century.The extent to which solar radiation was absorbed by different ground cover types was different,with grassland being the strongest and cropland the least.In the past few years,the Songnen Plain and Sanjiang Plain regions were the most significant changes in the absorption of solar radiation by the ground cover.The change in ground cover type led to a change in solar radiation absorption at the ground surface,with the conversion of waters to cropland or grassland and the conversion of cropland to woodland or grassland showing the greatest change in radiation absorption values,and vice versa.Of these,the absolute difference in the conversion of waters to cropland amounts to-156.66 W·m^(-2) in 2010-2015.The variation in the absorption of solar radiation at the ground surface was related to the characteristics of the ground class itself,but was also limited by the regional environment.Recommendations and perspectives This study showed that surface cover change can affect the absorption of solar radiation at the surface to varying degrees.The unchanged land classes were used as a comparative analysis in this paper,and it was clear from the paper that some of the unchanged land classes showed significant changes in radiation absorption that should be of interest in future studies.

Geochemical Anomalies Identified by Multifractal Modeling: Implications for Mineral Exploration in the Ziyoutun Cu-Au District, Jilin Province, China

The Ziyoutun Cu-Au district is located in the Jizhong–Yanbian Metallogenic Belt and possesses excellent prospects. However, the thick regolith and complex tectonic settings present challenges in terms of detecting and decomposition of weak geochemical anomalies. To address this challenge, we initially conducted a comprehensive analysis of 1:10,000-scale soil geochemical data. This analysis included multivariate statistical techniques, such as correlation analysis, R-mode cluster analysis, Q–Q plots and factor analysis. Subsequently, we decomposed the geochemical anomalies, identifying weak anomalies using spectrum-area modeling and local singularity analysis. The results indicate that the assemblage of Au-Cu-Bi-As-Sb represents the mineralization at Ziyoutun. In comparison to conventional methods, spectrumarea modeling and local singularity analysis outperform in terms of identification of anomalies. Ultimately, we considered four specific target areas(AP01, AP02, AP03 and AP04) for future exploration, based on geochemical anomalies and favorable geological factors. Within AP01 and AP02, the geochemical anomalies suggest potential mineralization at depth, whereas in AP03 and AP04 the surface anomalies require additional geological investigation. Consequently, we recommend conducting drilling, following more extensive surface fieldwork, at the first two targets and verifying surface anomalies in the last two targets. We anticipate these findings will significantly enhance future exploration in Ziyoutun.

Spatiotemporal Changes of Snow Depth in Western Jilin,China from 1987 to 2018

Seasonal snow cover is a key global climate and hydrological system component drawing considerable attention due to glob-al warming conditions.However,the spatiotemporal snow cover patterns are challenging in western Jilin,China due to natural condi-tions and sparse observation.Hence,this study investigated the spatiotemporal patterns of snow cover using fine-resolution passive mi-crowave(PMW)snow depth(SD)data from 1987 to 2018,and revealed the potential influence of climate factors on SD variations.The results indicated that the interannual range of SD was between 2.90 cm and 9.60 cm during the snowy winter seasons and the annual mean SD showed a slightly increasing trend(P>0.05)at a rate of 0.009 cm/yr.In snowmelt periods,the snow cover contributed to an increase in volumetric soil water,and the change in SD was significantly affected by air temperature.The correlation between SD and air temperature was negative,while the correlation between SD and precipitation was positive during December and March.In March,the correlation coefficient exceeded 0.5 in Zhenlai,Da’an,Qianan,and Qianguo counties.However,the SD and precipitation were neg-atively correlated over western Jilin in October,and several subregions presented a negative correlation between SD and precipitation in November and April.

CHARACTERISTICS OF CHANGE IN TEMPERATURE DURING THE PAST 50 YEARS IN JILIN PROVINCE OF CHINA

Based on the monthly mean temperatu re,the changing processes and tendencies of temperature during1951-2000in Jilin Province,which i s in Northeast China,are analyzed.A nd the spatial characteristics of th e change are submitted.In the past 50years the te mperature of Jilin Province was increasing just like the other areas in th e world.Since 1990,the increasing of temperature has been more obvious th an that in the previous 40a.From the west to the east,the province has larger tem perature rising.According to Principal Component Analysis(PCA)of temperature field,Jilin Province is divided int o 3regions and the degree of becoming warmer is different from region to re gion.During the period of 1951to 2000,the annual temperature in Jilin Province has been rising,so has the temperature in winter and summer.The average temperature in t he 1990s was 0.5-2.0℃higher than that in the 1950s.From the west to the east,the increasing of temperature becam e smaller.

Dynamic Change of Landscape Pattern at Jilin Province from 1980 to 2000

By using remote sensing images from three periods (1980, 1995, 2000) and with the support of GIS and RS, the spatial information of landscape elements of Jilin Province from 1980 to 2000 was interpreted and extracted. Using models of landscape indices such as diversity, fragmentation, and mean patch fractal dimension, dynamic spatio-temporal changes of landscape patterns of the province were analyzed. The results: ① cropland and forestland were the main landscape types, and forestland became a landscape matrix; ② in the study area, landscapes were distributed unevenly, and there was low heterogeneity, a simple ecosystem structure and a tendency of irrational landscape patterns. There were also simple spatial shapes of patches and strong self-similarities, and in terms of dynamic change analysis, patch shapes tended to be more simple; ③ from 1980 to 2000, holistic landscape fragmentation was low and changed slightly. As far as landscape elements were concerned, the fragmentation of grassland, water area, land for residential area and factory facilities was relatively low; land distribution for residential areas and factory facilities was dispersed; and cropland and forestland were most concentrated-an indication that the trend will continue. Comprehensive effects among human activity, local policy, regional climate and environmental change led to the results.

RESPONSES OF WETLAND ECO SECURITY TO LAND USE CHANGE IN WESTERN JILIN PROVINCE, CHINA

By the use of the software of ARCGIS, dynamic changes of the landscape elements, landscape structure, conversion processes of the landscape gradients and the responses of wetland eco-security to land use/cover changes (LUCC) in the western Jilin Province were studied from 1930 to 2000. The results show that the landscape elements of grassland, wetland, forestland and water area shrank rapidly, and wetlands underwent huge losses in the study period due to the conversion from wetland into arable land and grassland in large quantities. The responses of wetland eco-security to LUCC were inverse evolvement of wetland vegetation, loss of biodiversity, water deficiency in wetland ecosystem, the changes of the heterogeneity of wetlands and the fragmentation of the wetland habitats. Suggestions were given for protection of wetlands and the regional sustainable development.

Surface Water Resources' Response to Climate Changes in Jilin Province

[Objective] The response of surface water resources on climate changes was studied.[Method] By dint of monthly average temperature and precipitation in 45 meteorological stations in Jilin Province from 1960 to 2000,monthly runoff in 56 hydrological stations in Songhuajiang and Liaohe region,the surface runoff change and the response of surface water resources to climate change in 41 years were expounded.[Result] The runoff of Songliao region was limited during 1960s and 1970s.It began to increase slowly in the early 1980s.Since 1990s,there were distinct fluctuation of annual runoff and it was decreasing in general.EOF analysis suggested that the runoff of Songliao region was decreasing gradually from south to the north.The central gradient was small and runoff was evenly distributed.MK test result showed that the annual runoff in Songliao region had large fluctuation before 1980s and after 1990s.The response of surface runoff on climate and precipitation changes in Jilin Province was distinct and had strong relevance as well as certain lagging.Based on the analysis of the relation of rivers runoff and meteorological elements changes,statistics forecast model between river surface runoff and meteorological elements was constructed.Runoff prediction value and measured value had good relation.The corresponding river surface runoff changes can be assessed based on the changes of meteorological elements.[Conclusion] The study provided theoretical basis for the development and utilization of surface water resources in Jilin.

Study on the Change Character of Double Rice Cold Damage in Hunan and Hubei Province during the Past 50 Years

Based on the meteorological data of representative meteorological stations in Hunan and Hubei from 1961 to 2008 years,the change character of double rice cold damage under the background of climate change were analyzed adopting 30 years glide accumulation method.The analysis showed that the 30 years sliding cumulative days of mild low-temperature during spring sowing in Hunan and Hubei were decreased in the recent 50 years,as well as the 30 years sliding cumulative days of moderate low-temperature in central south Hubei,northern and western Hunan.However,there was an increase in southern Hunan,so was the 30 years sliding cumulative days of severe low-temperature.The 30 years sliding cumulative days of mild low-temperature in May reduced in Hunan and Hubei.Instead,that of moderate low-temperature in May in central south Hubei was on the rise,and it was opposite in northern and southern Hunan,but there was no obvious change in western Hunan.The 30 years sliding cumulative days of severe low-temperature showed a decreasing tendency in May in central south Hubei,northern and western Hunan,and southern Hunan showed a contrary tendency.The 30 years sliding cumulative days of mild cold dew wind in Hunan and Hubei were decreased,that of moderate cold dew wind in central south Hubei,northern and western Hunan had the same tendency,but there was a contrary tendency in southern Hunan.The 30 years sliding cumulative days of severe cold dew wind was decreased in central south Hubei and increased in western Hunan,without cold dew wind in northern and southern Hunan.

Effect of Irrigation on Groundwater Dynamic Change in the Typical Irrigated Area of Qinghai Province

Under the influence of the natural and human factors, water table of irri- gated area Changes frequently, but it is mainly affected by irrigation water infiltration replenishment during the irrigation. 5 groundwater observation wells were constructed in experimental plot of the Daxia irrigated area to carry out the experiment of the effect of irrigation on groundwater dynamic change in this research. The results showed that the groundwater stage dynarnic change rule of spring and seedling irri- gation stage in the typical plot was fit to the hydrological geology condition of grade- I terrace of Huangshui river valley. On the whole, lateral canal water direction formed a line effect. The No. 1 and No. 2 observation well were the closest to the lateral canal, which received more supplies, and the water level was the highest; the No, 3 observation well took the second place; The No. 4 and No. 5 observation well accepted least supplies, and the water level was the lowest. The rangeability of water table of spring irrigation period was significantly higher than that of seedling irrigation period, this is mainly due to the difference value of intake water volume and drainage water volume of spring irrigation phase was significantly higher than the seedling irrigation phase.

Pattern Change and Regional Disparity Tendency of Cultivated Land Use in Jiangsu Province

The study has examined the tempo-spatial patterns of cultivated land use change in Jiangsu province. A principal component analysis （PCA） of 18 selected indicators of cultivated land use during the period 1970-2010 identified 2 main pat- terns of change in planting productivity and economic efficiency. A major shift from production-centered pattern to profit-oriented one occurred in 1984, the time of grain yield surplus and the mitigation of population pressure. In response to the impending Opened Market System, there was a notable tendency of higher efficiency and less productivity since 1997, as well as remarkable regional disparity of cultivated land use change spatially. It revealed a relative decrease in grain cropping share, crop- ping scale and cultivation intensity in South Jiangsu, especially in Tai-Lake region, and the reverse in North Jiangsu. Some suggestions for the future were finally dis- cussed from the above findings.

Spatial Distribution of Different Types of Villages for Rural Revitalization Strategy and Their Influencing Factors:A Case of Jilin Province,China

Village classification is the first step to implementing China’s rural revitalization(RR)strategy,and understanding the geographic differences in the distribution of village types helps to grasp the pathway of their unique development.This study spatialized9250 villages in Jilin Province(divided into six types)of China,and their distribution characteristics and influencing factors were examined using methods such as kernel density estimation,Ripley’s K function,the co-location quotient,and Geodetector.The results indicate that the spatial distribution balance and density of village types are different.All types of villages show an agglomeration distribution pattern,but the scale and intensity vary.There is a strong spatial association between agglomerative promotion(AP)and stable improvement(SIm)villages,as well as between characteristic protection(CP)and prospering frontier and enriching people(PE)villages.The factors affecting their distribution include terrain undulation,the percentage of arable land,the distance to the county town,road network density,population density,gross domestic product(GDP),and industrial enterprise density.The influencing factors for the distribution of village types are closely related to the function of each village.Based on the differences in the spatial distribution and influencing factors of different village types,policy suggestions are given for classified development.

Analysis of Landscape Changes in the Karst Areas of Puding County in Guizhou Province

Based on GIS,RS and the landscape analysis software,landscape changes in the middle and lower reaches of Houzhai River in Puding County of Guizhou Province from 1973 to 2004 were analyzed.The results indicated that paddy fields and dry fields held a dominant status.In the change of landscape types,forest land reduced continually,dry fields changed complicatedly,and the mutual transformation among grass land,shrub land and forest land was obvious.The area of bare rock increased remarkably in the slope range between 10° and 35°.Artificially 'returning cultivation land into forests and pastures','reclamation by damaging forests and pastures',and natural ecosystem converse succession existed at the same time.Therefore,the whole landscape was in an unstable state.

Land Suitability Assessment and Land Use Change in Fujian Province,China

To present the current status of land quality and distribution and the trends in land use change, the physical suitability of cropland and forestland and the associated changes in Fujian Province were evaluated and analyzed using data obtained from geographical information systems (GIS) and remote sensing (RS).Of the total land area of Fujian Province,first class suitable cropland accounted for only 4.21%, whereas unsuitable cropland accounted for 84.78%. The percentage of first class suitable cropland in the southeastern region (5.32%) was much higher than that in the northwestern area (2.91%).Only 13.63% of the existing cropland area consisted of first class cropland and 70.08% was classified as unsuitable for cultivation.Of the total land area of Fujian Province,the first class forestland comprised 55.25% and the unsuitable forestland (including third class) comprised 21.2%.The percentage of unsuitable forest area in the existing forestland was only 5.5%.From 1996 to 2001, cropland and unused land decreased significantly, whereas forestland and land used for urban and transport increased rapidly.Therefore,the major tasks ahead will be the land development for full grain production potential,the better coordination of allocating land to different uses, and the regulation inappropriate activities that damage agricultural ecosystems.

Using ORYZA2000 to model cold rice yield response to climate change in the Heilongjiang province, China

Rice(Oryza sativa L.) is one of the most important staple crops in China. Increasing atmospheric greenhouse gas concentrations and associated climate change may greatly affect rice production. We assessed the potential impacts of climate change on cold rice production in the Heilongjiang province, one of China's most important rice production regions. Data for a baseline period(1961–1990) and the period 2010–2050 in A2 and B2 scenarios were used as input to drive the rice model ORYZA2000 with and without accounting for the effects of increasing atmospheric CO2 concentration. The results indicate that mean,maximum, and minimum temperature during the rice growing season, in the future period considered, would increase by 1.8 °C under the A2 scenario and by 2.2 °C under the B2 scenario compared with those in the baseline. The rate of change in average maximum and minimum temperatures would increase by 0.6 °C per 10-year period under the A2 scenario and by 0.4 °C per 10-year period under the B2 scenario. Precipitation would increase slightly in the rice growing season over the next 40 years. The rice growing season would be shortened and the yield would increase in most areas in the Heilongjiang province. Without accounting for CO2 effect, the rice growing season in the period 2010–2050 would be shortened by 4.7 and 5.8 days,and rice yields would increase by 11.9% and 7.9%, under the A2 and B2 scenarios, respectively.Areas with simulated rice yield increases greater than 30.0% were in the Xiaoxing'an Mountain region. The simulation indicated a decrease in yield of less than 15% in the southwestern Songnen Plain. The rate of change in simulated rice yield was 5.0% and 2.5% per 10 years under the A2 and B2 scenarios, respectively. When CO2 effect was accounted for, rice yield increased by 44.5% and 31.3% under the A2 and B2 scenarios, respectively. The areas of increasing yield were sharply expanded. The area of decreasing yield in the western region of Songnen Plains disappeared when increasing CO2 concentration was considered. The stability of rice yield would increase from 2010 to 2050. Overall, the simulation indicates that rice production will be affected positively by climate change in the next 40 years in the Heilongjiang province, China.

On arable land changes in Shandong Province and their driving forces

The decrease of total cultivated area and the lower per capita available arable land resource are now serious problems in Shandong Province, a major agricultural province in China. These problems will become more serious along with the further development of economy. In this paper, based on the statistical information at provincial and county levels, the changes of arable land in Shandong Province and their driving forces during the last 50 years are analyzed. The general changing trends of arable land and per capita available arable land are reducing, and the trends of decrease will continue when the economy is developing. The result of GIS spatial analysis shows that the change of the arable land use in Shandong Province has a regional difference. Eight variables having influences on cultivated land change are analyzed by principal component analysis. The results show that the dynamic development of economy, pressure of social system and progress of scientific techniques in agriculture are the main causes for cultivated land reduction. The principal factors which can be considered as driving forces for arable land change include per capita net living space, total population and per ha grain yield. By using regressive equation, along with analysis on population growth and economic development, cultivated areas in Shandong Province in 2005 and 2010 are predicted respectively. The predicted cultivated areas in Shandong will be 6435.47 thousand hain 2005 and 6336.23 thousand ha in 2010 respectively.

Regional agricultural landscape pattern changes along the Yellow River in Henan Province from 1987 to 2002

Agricultural landscape along the riparian zones is designated as important landscape components for partly controlling water quality, biodiversity, as well as for their aesthetic role in landscapes. Therefore, the change of agricultural landscape along the riparian zones is at the top of the agenda for many policy makers and landscape planners. As a basis for conservation management, sufficient information about landscape structure should be provided. In the present study, we reconstructed the former landscape structure and elucidated the changes in landscape patterns during a period of about 15 years. Two sets of maps were used： a landsat-5 TM image （1987） and landsat-7 ETM image （2002）. The frequency index, landscape diversity index and landscape fragmentation index were calculated for analyses. The results showed that： （1） the areas of the irrigated land, river, forest and beach landscape classes presented a decreasing trend while the areas of landscape classes of pool, paddy fields, dry land and construction land increased. （2） Disturbed by human activity, landscape diversity index increased but landscape fragmentation index decreased. In short, Human activities have had important influences on agricultural landscape of the riparian zones along the Yellow River in Henan Province.

Changing Rural Development Inequality in Jilin Province, Northeast China

Rural development inequality is an important practical issue during the course of full establishment of a ′moderately well-off society′ in modern China,and the objective understanding and evaluation of the status and regional inequality of rural development can provide scientific basis for ′building a new countryside′ and coordination development of rural-urban regions.Based on the county-level data of 2000,2005 and 2009,this paper examines the rural development inequality of Jilin Province in Northeast China by establishing a rural development index.The spatio-temporal dynamic patterns and domain factors are discussed by using the method of exploratory spatial data analysis and multi-regression model.The results are shown as follows.Firstly,most of the counties were in lower development level,which accounted for 58.3%,62.5% and 66.7% of the total counties in 2000,2005 and 2009,respectively.The characteristics of spatial inequality were very obvious at county level.For example,rural development level of Changchun Proper and the proper of seven prefecture-level cities were much higher than that of the surrounding regions.The counties in the eastern and northern Jilin Province were the lowest regions of rural development level,while the middle counties were the rapid growth areas in rural economy.Secondly,Moran′s I of rural development index(RDI) was 0.01,–0.16 and –0.06 in 2000,2005 and 2009,respectively,which indicated that spatial agglomeration of RDI was not obvious in Jilin Province,and took on the characteristic of random distribution.The counties of both the units and its adjacent units have higher development level(HH) were transferred from the western areas to the eastern areas,while the countries of both the units and its adjacent units have lower development level(LL) were diffused from the eastern to middle and western Jilin Province.Finally,the result of multi-regression analysis showed that the improvement of agricultural production condition,development of agricultural economics and the adjustment of industrial structure were the domain factors affecting rural development inequality of Jilin Province in the later ten years.

Quantitative analysis of the dynamic change and spatial differences of the ecological security: a case study of Loess Plateau in northern Shaanxi Province

Using the theory and method of the ecological footprint, and combining the changes of regional land use, resource environment, population, society and economy, this paper calculated the ecological footprint, ecological carrying capacity and ecological surplus/loss in 1986-2002 on the Loess Plateau in northern Shaanxi Province. What is more, this paper has put forward the concept of ecological pressure index, set up ecological pressure index models, and ecological security grading systems, and the prediction models of different ecological footprints, ecological carrying capacity, ecological surplus and ecological safety change, and also has assessed the ecological footprint demands of 10,000 yuan GDE The results of this study are as follows： （1） the ecological carrying capacity in northern Shaanxi shows a decreasing trend, the difference of reducing range is the fastest; （2） the ecological footprint appears an increasing trend; （3） ecological pressure index rose to 0.91 from 0.44 during 1986-2002 on the Loess Plateau of northern Shaanxi with an increase of 47%; and （4） the ecological security in the study area is in a critical state, and the ecological oressure index has been increasing rapidlv.

Process and mechanism of arable land change in Hebei Province during the past 50 years

Hebei Province is one of the regions with most densely population, fastest economic growth and most intensive land use in China. The contradiction of land shortage sharpened by high-speed economic development with population growth has become a serious problem, which has restricted regional sustainable development.This paper revealed the basic process, regional differences of change and the gravity center of arable land area according to the long-series statistical data of arable land during the past 50 years. On the basis of the above mentioned, the major driving forces that influence the changes of the arable land are discussed. The research results indicate that there is a trend of obvious fluctuating decrease in arable land area during the last 50 years. The changes of arable land area undergo the process from increase to sharp decrease to gently decrease. The regional disparity of change in arable land area is very notable and the gravity center of arable land area moves to the northeast 49.22 km. Regarding the decrease in arable land, the direct driving forces include adjustments of agricultural structure and reclamation, and indirect driving forces include advance in technology, economic interest and population growth etc.

Changes of crop climate risk degree:a case study on cotton in Henan Province

The agricultural climate risk in the geographical transitional zones is very sensitive to climate change. Based on previous researches, this article established the cotton climate suitability model and the risk index to analyze the cotton climate risk degree in Henan Province. The result shows that, in the last 40 years, the cotton climate risk degree has a gradual increasing trend in which the precipitation plays a very important role, and the climate suitability and its deviation have different performances in the influence on the risk change in different phases; the increase rate of risk degree has significant regional and transitional characteristics, for example, from the eastern plain to the western mountains, the risk change rate becomes slower and slower, so the contrast between the central-southern Huang-Huai plain and the Funiu mountains is the most remarkable; and in the north-south direction, the contrast between the fast increase belt from the central-southern Huang-Huai plain to the middle Yellow River and the slow increase belt near the Yellow River is particularly remarkable, which is possibly the results of topographic and climatic transitional belt; and the risk change process also has obvious regional difference. For instance, abrupt change is an important characteristic in eastern Henan where this sudden change type has notable latitudinal difference, while in the western mountainous area it is very rare. Although the temperature change over the 40 years is still increasing in this area, the trend has reduced gradually since the end of the 1980s.