Spatiotemporal landscape pattern changes and their effects on land surface temperature in greenbelt with semi-arid climate:A case study of the Erbil City,Iraq

Urban expansion of cities has caused changes in land use and land cover(LULC)in addition to transformations in the spatial characteristics of landscape structure.These alterations have generated heat islands and rise of land surface temperature(LST),which consequently have caused a variety of environmental issues and threated the sustainable development of urban areas.Greenbelts are employed as an urban planning containment policy to regulate urban expansion,safeguard natural open spaces,and serve adaptation and mitigation functions.And they are regarded as a powerful measure for enhancing urban environmental sustainability.Despite the fact that,the relation between landscape structure change and variation of LST has been examined thoroughly in many studies,but there is a limitation concerning this relation in semi-arid climate and in greenbelts as well,with the lacking of comprehensive research combing both aspects.Accordingly,this study investigated the spatiotemporal changes of landscape pattern of LULC and their relationship with variation of LST within an inner greenbelt in the semi-arid Erbil City of northern Iraq.The study utilized remote sensing data to retrieve LST,classified LULC,and calculated landscape metrics for analyzing spatial changes during the study period.The results indicated that both composition and configuration of LULC had an impact on the variation of LST in the study area.The Pearson's correlation showed the significant effect of Vegetation 1 type(VH),cultivated land(CU),and bare soil(BS)on LST,as increase of LST was related to the decrease of VH and the increases of CU and BS,while,neither Vegetation 2 type(VL)nor built-up(BU)had any effects.Additionally,the spatial distribution of LULC also exhibited significant effects on LST,as LST was strongly correlated with landscape indices for VH,CU,and BS.However,for BU,only aggregation index metric affected LST,while none of VL metrics had a relation.The study provides insights for landscape planners and policymakers to not only develop more green spaces in greenbelt but also optimize the spatial landscape patterns to reduce the influence of LST on the urban environment,and further promote sustainable development and enhance well-being in the cities with semi-arid climate.

Landscape ecological risk assessment and its driving factors in the Weihe River basin,China

Weihe River basin is of great significance to analyze the changes of land use pattern and landscape ecological risk and to improve the ecological basis of regional development.Based on land use data of the Weihe River basin in 2000,2010,and 2020,with the support of Aeronautical Reconnaissance Coverage Geographic Information System(ArcGIS),GeoDa,and other technologies,this study analyzed the spatial-temporal characteristics and driving factors of land use pattern and landscape ecological risk.Results showed that land use structure of the Weihe River basin has changed significantly,with the decrease of cropland and the increase of forest land and construction land.In the past 20 a,cropland has decreased by 7347.70 km2,and cropland was mainly converted into forest land,grassland,and construction land.The fragmentation and dispersion of ecological landscape pattern in the Weihe River basin were improved,and land use pattern became more concentrated.Meanwhile,landscape ecological risk of the Weihe River basin has been improved.Severe landscape ecological risk area decreased by 19,177.87 km2,high landscape ecological risk area decreased by 3904.35 km2,and moderate and low landscape ecological risk areas continued to increase.It is worth noting that landscape ecological risks in the upper reaches of the Weihe River basin are still relatively serious,especially in the contiguous areas of high ecological risk,such as Tianshui,Pingliang,Dingxi areas and some areas of Ningxia Hui Autonomous Region.Landscape ecological risk showed obvious spatial dependence,and high ecological risk area was concentrated.Among the driving factors,population density,precipitation,normalized difference vegetation index(NDVI),and their interactions are the most important factors affecting the landscape ecological risk of the Weihe River basin.The findings significantly contribute to our understanding of the ecological dynamics in the Weihe River basin,providing crucial insights for sustainable management in the region.

Characteristics and drivers of the soil multifunctionality under different land use and land cover types in the drylands of China

The drylands of China cover approximately 6.6×106 km2 and are home to approximately 5.8×10^(8)people,providing important ecosystem services for human survival and development.However,dryland ecosystems are extremely fragile and sensitive to external environmental changes.Land use and land cover(LULC)changes significantly impact soil structure and function,thus affecting the soil multifunctionality(SMF).However,the effect of LULC changes on the SMF in the drylands of China has rarely been reported.In this study,we investigated the characteristics of the SMF changes based on soil data in the 1980s from the National Tibetan Plateau Data Center.We explored the drivers of the SMF changes under different LULC types(including forest,grassland,shrubland,and desert)and used structural equation modeling to explore the main driver of the SMF changes.The results showed that the SMF under the four LULC types decreased in the following descending order:forest,grassland,shrubland,and desert.The main driver of the SMF changes under different LULC types was mean annual temperature(MAT).In addition to MAT,pH in forest,soil moisture(SM)and soil biodiversity index in grassland,SM in shrubland,and aridity index in desert are crucial factors for the SMF changes.Therefore,the SMF in the drylands of China is regulated mainly by MAT and pH,and comprehensive assessments of the SMF in drylands need to be performed regarding LULC changes.The results are beneficial for evaluating the SMF among different LULC types and predicting the SMF under global climate change.

Extensive identification of landslide boundaries using remote sensing images and deep learning method

The frequent occurrence of extreme weather events has rendered numerous landslides to a global natural disaster issue.It is crucial to rapidly and accurately determine the boundaries of landslides for geohazards evaluation and emergency response.Therefore,the Skip Connection DeepLab neural network(SCDnn),a deep learning model based on 770 optical remote sensing images of landslide,is proposed to improve the accuracy of landslide boundary detection.The SCDnn model is optimized for the over-segmentation issue which occurs in conventional deep learning models when there is a significant degree of similarity between topographical geomorphic features.SCDnn exhibits notable improvements in landslide feature extraction and semantic segmentation by combining an enhanced Atrous Spatial Pyramid Convolutional Block(ASPC)with a coding structure that reduces model complexity.The experimental results demonstrate that SCDnn can identify landslide boundaries in 119 images with MIoU values between 0.8and 0.9;while 52 images with MIoU values exceeding 0.9,which exceeds the identification accuracy of existing techniques.This work can offer a novel technique for the automatic extensive identification of landslide boundaries in remote sensing images in addition to establishing the groundwork for future inve stigations and applications in related domains.

Assessing Spatio-Temporal Land Cover Changes in Dhund River Basin, Eastern Rajasthan (India), Using Multi-Temporal Landsat Data

Land cover is an impression of natural cover on surface of earth such as bare soil, river, grass etc. and utilization of these natural covers for various human needs and purposes by mankind is defined as land use. Land cover identification, delineation and mapping is important for planning activities, resource management and global monitoring studies while baseline mapping and subsequent monitoring is done by application of land use to get timely information about quantity of land that has been used. The present study has been carried out in Dhund river watershed of Jaipur, Rajasthan which covers an area of about 1828 sq∙km. The minimum and maximum elevation of the area is found to be 214 m and 603 m respectively. Land use and land cover changes of three decades from 1991 to 2021 have been interpreted by using remotes sensing and GIS techniques. ArcGIS software (Arc map 10.2), SOI topographic map, Cartosat-1 DEM and satellite data of Landsat 5 and Landsat 8 have been used for interpretation of eleven classes. The study shows an increase in cultivated land, settlement, waterbody, open forest, plantation and mining due to urbanization because of increasing demands of food, shelter and water while a decrease in dense forest, river, open scrub, wasteland and uncultivated land has also been marked due to destruction of aforementioned by anthropogenic activities such as industrialization resulting in environmental degradation that leads to air, soil and water pollution.

Rainfall Dynamics and Landslides in Urban Areas of Gabon: The Case of Libreville-Est (Gabon)

Due to its abundant rainfall, the city of Libreville, which concentrates more than half of Gabon’s population, is frequently confronted with the impacts of natural disasters such as floods and landslides. This study attempts to identify the complex relationships between the dynamics of land use and the role of rainfall in the occurrence of landslides. On the one hand, it uses statistics on landslides compiled from information taken from general news bulletins and, on the other, daily rainfall data obtained from the National Meteorological Department. The study revealed that the Libreville East sector, dominated by Mount Nkol Ogoum, one of Libreville’s most prominent landforms, is affected by a land-use dynamic in which human settlement has been progressing for some thirty years, to the detriment of the original vegetation which, among other things, helped to stabilise the soil on the hillsides and the marshy areas at the foot of the slopes. The result is not only an uncontrolled occupation of the land, but also a major landslide every two years in this part of the city, causing significant loss of life and property. However, an analysis of the time series shows little rainfall variability, marked in particular by a predominance of negative anomalies, and the occurrence of a few exceptional daily rainfall peaks. Similarly, the period from 20 October to 20 November, which receives the most rainfall, also appears to be the most conducive to landslides.

Spatiotemporal detection of land use/land cover changes and land surface temperature using Landsat and MODIS data across the coastal Kanyakumari district, India

This study assesses the changes in land use/land cover(LULC) and land surface temperature(LST) to identify their impacts from 2000 to 2020 along the coast of Kanyakumari district, India using remote sensing techniques. Landsat images are used to estimate the LULC changes and the MODIS data for LST.The Maximum Likelihood Classification(MLC) method is used, and the LULC is classified into six categories: Agriculture Land, Barren Land, Salt Pan, Sandy Beach, Settlement, and Waterbody. Within the two decades of the present change detection study, upheave in the Settlement area of 49.89% is noticed, and the Agriculture Land is exploited by 20.09%. Salt Pan emits a high LST of 31.57°C, and the Waterbodies are noticed with a low LST of 28.9°C. However, the overall rate of LST decreased by 0.56°C during this period. This study will help policymakers make appropriate planning and management to overcome the impact of LULC and LST in the forthcoming years.

Thunderstorm and Lightning Activities over Western Pacific,Northern Indian Ocean and South China Sea Along with Their Adjacent Lands

The Lightning Imaging Sensor(LIS)and Radar Precipitation Feature(RPF)data are used to investigate the activities and properties of lightning and thunderstorms over a region including the Western Pacific,northern Indian Ocean and the South China Sea along with their adjacent lands.The lands feature significantly more frequent lightning flashes and thunderstorms than the oceans,especially the open oceans.The highest densities of lightning and thunderstorm occur over the Strait of Malacca and the southern foothills of the Himalayas.Over the ocean regions,the Bay of Bengal and the South China Sea are characterized by relatively frequent lightning and thunderstorm activities.Larger average spatiotemporal size and optical radiance of flashes can be found over the oceans;specifically,the offshore area features the most significant flash duration,and the open ocean area is characterized by the greatest flash length and optical radiance.The smallest average values of flash properties can be found over and around the Tibetan Plateau(TP).The oceanic thunderstorms tend to have a significantly larger horizontal extent than the continental thunderstorms,with the former and latter having the average area of the regions with radar reflectivity larger than 20 dBZ,generally over 7000 km^(2) and commonly below 6000 km^(2),respectively.The TP thunderstorms show the smallest horizontal extent.Meanwhile,the oceanic thunderstorms exhibit greater 20 dBZ but smaller 40 dBZ top heights than the continental thunderstorms.The average flash frequency and density of the oceanic thunderstorms are typically less than 5 fl min^(-1) and 0.3 fl 100 km^(-2) min^(-1),respectively;in contrast,the corresponding values of continental thunderstorms are greater.It is explored that the regions associated with strong convective thunderstorms are more likely to feature small-horizontal-extent and low-radiance flashes.

Estimating Ecological Characteristics and Carbon Stock in Uneven-Aged Plantations of Acacia senegal L. in the Savannah Woodlands of Sudan

The aim of this study was to assess Acacia senegal trees’ characteristics as well as evaluate the carbon stock under a variety of ages in the El Demokeya forest in Sudan, where the Gum Arabic belt is located. 12 sample plots, in 2021 were randomly distributed to represent the entire area of the forest prior to the required measurements. The sample was designed as squire plots with one hectare. In each sample plot, all trees were counted, their height (m), and Diameters Breast Height (DBH in cm), respectively. The results showed the highest number of trees per ha at age 20 years old and the lowest number at age 47 years, while the highest values of DBH and volume were found at age 47 years old. As a result, the maximum and minimum values of the aboveground biomass were found in the age 47 years old and 16 years, accounting for 19.87 tons and 1.9 tons respectively. Thus, the amount of carbon stock was 11.92 tons/ha in the 35-years-old and 1.19 tons/ha in the 21-year stands. Furthermore, the average carbon stock in all plots was estimated as 18.70 tons/ha and hence the total carbon stock in the El Demokeya forest is equal to 620.11 tons. Conclusively, the characteristics of trees, amount of aboveground biomass and carbon stock in the El Demokeya forest varied among the uneven-aged plantation groups. The study recommends and encourages the protection of A. senegal in order to increase the carbon sink as well as protect the environment in the era of climatic changes.

Hydrologic Thresholds of Ecosystem Resiliency:Have Wetlands on the Anoka Sand Plain Changed over Time?

Wetlands have long been used as environmental indicators for changes in climate and land use because they are sensitive to hydrologic change;however,wetlands set in transmissive groundwater can be more resilient to climate and land use change.In Anoka County,Minnesota,USA,a monitoring network was established in 1997 and maintained by the Anoka Conservation District to the present day to assess wetland hydrologic response over time.We examined a combination of data including water level(stage)from these wetlands,precipitation from local gages,pan evaporation data,and historical land use,including a measure of runoff flashiness,using regression and k-mean analysis.Results did not detect any clear trends over a 25-year time period,though some p-values showed potential.A clear statistical trend in the measured hydrologic parameters would suggest exceedance beyond historical thresholds of natural hydrologic variation and alert the need to better protect wetlands and groundwater from anthropogenic stress.Study results may provide useful information to management and regulatory decisions for wetland systems set in sandy soils.This is particularly important for Anoka County because most wetlands are intrinsically connected to the surficial ASP(Anoka Sand Plain)Aquifer,which overlay vulnerable deeper aquifers used for domestic water supply.

Carbon Storage and Environmental Determinants in a Tropical Rainforest Landscape

Tropical ecosystems sequester vast amounts of carbon but remain much varied across different landscapes. In order to provide estimates on carbon storage for the ecosystem and show the role of forest structure and environmental factors in determining aboveground and soil carbon of a rainforest landscape, forest inventory was conducted across 30 forest plots. Each of the plots measured 50 m × 50 m and was used to identify and measure tree species ≥ 10 cm diameter at breast height (DBH measured at 130cm). Soil samples were collected for up to 30 cm deep at the four edges and then the middle of each plot, bulked for analysis and tested in the laboratory. Aboveground carbon estimates ranged from 8.18 - 91.29 t/ha across the ecosystem and were similar with carbon storage in tropical landscapes. With variations in stem density, basal area and structure across the region, much of the carbon capacity across the ecosystem was much varied (F (29, 2127) = 3.794, p = 0.000). Environmental variables (mainly edaphic variables) were not positively correlated with soil carbon and did not largely determine its storage and variation. The need to reduce disturbances (which are a main driver of disparity in biomass carbon storage) across the region and across tropical ecosystems was advocated as a pathway to enhancing higher carbon sequestration.

Land Surface Temperature Change in Hangzhou Urban Area in Recent 20 Years Based on Landsat Image

Since the reform and opening-up in 1978, the urbanization level of our country has been continuously improved and the urban development has made great progress. However, with the rapid expansion of urban construction land, the population density and building density have been greatly increased, resulting in the urban heat island effect, which has negative impact on the urban thermal environment and restricts the high-quality development of urbanization. This paper focuses on how the urban surface thermal environment of Hangzhou changes in 20 years. In this paper, the characteristics of land surface temperature (LST) in Hangzhou urban area from 2000 to 2020 were studied by using Landsat images. The radiative transfer equation method is used to retrieve the land surface temperature, and the retrieval results are analyzed. The results show that: 1) the land surface temperature in Hangzhou city area has a slight upward trend in the past 20 years;2) the area of high temperature area is expanding;3) the land surface temperature in the city center area has decreased significantly in the past 20 years, while the ground temperature in other areas around the city center has increased significantly.

基于长时间序列Landsat影像的南方人工林干扰与恢复制图分析

基于1986年到2011年的Landsat影像,以南方人工林分布区域广东省佛冈县为例,运用Landsat生态系统自适应处理系统(LEDAPS)预处理生成标准的地面反射率数据构建Landsat时间序列堆栈(LTSS)用于Land Trendr算法监测人工林森林干扰与恢复的长时间序列变化,分析了连续24a森林干扰的年份变化、干扰量以及干扰持续的时间,验证了算法识别干扰的精度,并探讨了人工林干扰的驱动力。结果表明佛冈县的森林干扰较为剧烈,一般都在1000 hm^2。而1987、2002、2004、2005、2006、2007和2009年的干扰面积均超过2000 hm^2,其中1987、2007年两年的干扰面积达到6000 hm^2以上。相比森林干扰的变化,佛冈县的森林恢复面积随时间的变化相对平稳。通过对佛冈县森林干扰和恢复面积的趋势分析,发现20世纪80年代末到90年代森林干扰和恢复的面积基本少于2000年以后的变化面积,变化趋势比2000年以后的显得平缓;从2000年开始,森林干扰面积逐渐上升,总体面积变化趋势高于森林的恢复,但森林的恢复面积仍有所提升。其中,佛冈县的森林干扰持续1a时间的面积比例约38%,持续2a时间约28%,持续3a时间约25%,持续4a时间约7%,主要为短期急剧的干扰事件。另外,持续时间为4a以上的森林干扰和恢复的面积在佛冈县不超过100hm^2。2000年之前持续干扰和急剧干扰面积相当,变化比较平缓;到2000年之后,急剧干扰的面积远大于持续干扰,最高约达2800 hm^2,但两者都呈现波动上升的变化趋势。在选取的两个4km^2的样方中,基于影像光谱识别以及通过比对干扰资料的可视化验证方法表明算法结果与真实地表的解译信息较吻合,误差约为0.1km^2。利用长时间序列遥感影像进行森林干扰的自动化监测十分必要,导出的定性、定位与定量信息,一方面为可持续的森林经营奠定基础,另一方面为评价森林生产力与森林碳储量提供有效的数据支撑。

基于Landsat长时间序列的森林扰动参数提取与树高估算

【目的】研究基于遥感影像的森林扰动信息定量提取及其对树高估算的影响,为遥感反演森林参数(树高、生物量)提供参考和借鉴。【方法】选取黑龙江省凉水国家级自然保护区为研究区,以1984—2006年33期Landsat TM/ETM+多光谱遥感影像为数据源,对其进行缨帽变换提取缨帽角(TCA)和缨帽距离(TCD)2个扰动监测指数,采用时间轨迹分析方法(LandTrendr)对TCA与TCD指数进行时间序列重构,分别提取扰动发生的前一年(DBYEA)、扰动发生前的光谱值(DBVAL)、扰动持续时间(DDUR)、扰动量级(DMAG)、扰动后开始修复的时间(RBYEAR)、扰动后开始修复的光谱值(RBVAL)、修复量级(RMAG)和修复持续时间(RDUR)8个时间序列扰动参数。基于单时相Landsat影像光谱信息与单时相Landsat影像光谱信息+森林扰动参数2组变量分别采用随机森林(RF)算法估算树高。【结果】采用单时相Landsat影像光谱信息结合基于TCA和TCD提取的16个时间序列扰动参数建立的树高反演模型预估精度比采用单时相Landsat影像光谱信息建立的树高反演模型预估精度提高6.34%,均方根误差(RMSE)降低0.50 m。树高反演模型中基于TCA提取的时间序列扰动参数变量重要性高于基于TCD提取的时间序列扰动参数变量重要性。【结论】基于LandTrendr提取的森林时间序列扰动参数能够增强反射率与树高之间的相关性,提高遥感树高模型的反演精度,基于TCA提取的森林时间序列扰动参数对树高的解释能力高于基于TCD提取的森林时间序列扰动参数。

Influence of Irregular Coastlines on a Tornadic Mesovortex in the Pearl River Delta during the Monsoon Season. Part Ⅰ:Pre-storm Environment and Storm Evolution

The Pearl River Delta(PRD),a tornado hotspot,forms a distinct trumpet-shaped coastline that concaves toward the South China Sea.During the summer monsoon season,low-level southwesterlies over the PRD’s sea surface tend to be turned toward the west coast,constituting a convergent wind field along with the landward-side southwesterlies,which influences regional convective weather.This two-part study explores the roles of this unique land–sea contrast of the trumpet-shaped coastline in the formation of a tornadic mesovortex within monsoonal flows in this region.Part I primarily presents observational analyses of pre-storm environments and storm evolutions.The rotating storm developed in a lowshear environment(not ideal for a supercell)under the interactions of three air masses under the influence of the land–sea contrast,monsoon,and storm cold outflows.This intersection zone(or“triple point”)is typically characterized by local enhancements of ambient vertical vorticity and convergence.Based on a rapid-scan X-band phased-array radar,finger-like echoes were recognized shortly after the gust front intruded on the triple point.Developed over the triple point,they rapidly wrapped up with a well-defined low-level mesovortex.It is thus presumed that the triple point may have played roles in the mesovortex genesis,which will be demonstrated in Part II with multiple sensitivity numerical simulations.The findings also suggest that when storms pass over the boundary intersection zone in the PRD,the expected possibility of a rotating storm occurring is relatively high,even in a low-shear environment.Improved knowledge of such environments provides additional guidance to assess the regional tornado risk.

Understanding the Relationship Between Shrinking Cities and Land Prices:Spatial Pattern,Effectiveness,and Policy Implications

Urban shrinkage has emerged as a widespread phenomenon globally and has a significant impact on land,particularly in terms of land use and price.This study focuses on 2851 county-level cities in China in 2005–2018(excluding Hong Kong,Macao,Taiwan,and‘no data’areas in Qinhai-Tibet Plateau)as the fundamental units of analysis.By employing nighttime light(NTL)data to identify shrinking cities,the propensity score matching(PSM)model was used to quantitatively examine the impact of shrinking cities on land prices,and evaluate the magnitude of this influence.The findings demonstrate the following:1)there were 613 shrinking cities in China,with moderate shrinkage being the most prevalent and severe shrinkage being the least.2)Regional disparities are evident in the spatial distribution of shrinking cities,especially in areas with diverse terrain.3)The spatial pattern of land price exhibits a significant correlated to the economic and administrative levels.4)Shrinking cities significantly negatively impact on the overall land price(ATT=–0.1241,P<0.05).However,the extent of the effect varies significantly among different spatial regions.This study contributes novel insights into the investigation of land prices and shrinking cities,ultimately serving as a foundation for government efforts to promote the sustainable development of urban areas.

Thermo-hydro-mechanical (THM) coupled simulation of the land subsidence due to aquifer thermal energy storage (ATES) system in soft soils

Aquifer thermal energy storage(ATES)system has received attention for heating or cooling buildings.However,it is well known that land subsidence becomes a major environmental concern for ATES projects.Yet,the effect of temperature on land subsidence has received practically no attention in the past.This paper presents a thermo-hydro-mechanical(THM)coupled numerical study on an ATES system in Shanghai,China.Four water wells were installed for seasonal heating and cooling of an agriculture greenhouse.The target aquifer at a depth of 74e104.5 m consisted of alternating layers of sand and silty sand and was covered with clay.Groundwater level,temperature,and land subsidence data from 2015 to 2017 were collected using field monitoring instruments.Constrained by data,we constructed a field scale three-dimensional(3D)model using TOUGH(Transport of Unsaturated Groundwater and Heat)and FLAC3D(Fast Lagrangian Analysis of Continua)equipped with a thermo-elastoplastic constitutive model.The effectiveness of the numerical model was validated by field data.The model was used to reproduce groundwater flow,heat transfer,and mechanical responses in porous media over three years and capture the thermo-and pressure-induced land subsidence.The results show that the maximum thermoinduced land subsidence accounts for about 60%of the total subsidence.The thermo-induced subsidence is slightly greater in winter than that in summer,and more pronounced near the cold well area than the hot well area.This study provides some valuable guidelines for controlling land subsidence caused by ATES systems installed in soft soils.

Studies of Soil Physical Property on Different Abandoned Lands in the Minqin Oasis,Downstream of the Shiyang River

The vast area of farmland was abandoned at downstream of the Shiyang River because of decreased water recourse. To ensure the ecological safety of Minqin Oasis and to provide management basis for the abandoned land, soil physical properties were observed and studied. The authors analyzed land with abandonment time of 1 year, 2 years, 3 years, 4 years, 5 years, 8 years, 15 years, 24 years and 31 years. Samples were took at the 0-40 cm layer of soil to measure the bulk density, porosity and grain composition of soil in the different abandoned lands. Results showed that the tendency of clay content was decreasing, conversely, the fine sand increased at the layer of 0-10 cm of different abandoned lands.The changes of grain content reached a peak at the fourth year after the land was abandoned, then varied slightly. The variation of grain content of abandoned land was obvious with the extension of the abandonment year. The soil bulk density decreased and porosity increased with the extension of the abandonment year. The difference of porosity and soil bulk density at the range of 0-40 cm of different abandoned land decreased after the land abandoned for 3 years. The quality of soil was decreased, while the soil permeability was improved. The soil physical properties changed obviously in 3 to 4 years after abandonment, so it is the key time for land management.

Spatiotemporal characteristics of cultivated land use eco-efficiency and its influencing factors in China from 2000 to 2020

Improving cultivated land use eco-efficiency(CLUE)can effectively promote agricultural sustainability,particularly in developing countries where CLUE is generally low.This study used provincial-level data from China to evaluate the spatiotemporal evolution of CLUE from 2000 to 2020 and identified the influencing factors of CLUE by using a panel Tobit model.In addition,given the undesirable outputs of agricultural production,we incorporated carbon emissions and nonpoint source pollution into the global benchmark-undesirable output-super efficiency-slacks-based measure(GB-US-SBM)model,which combines global benchmark technology,undesirable output,super efficiency,and slacks-based measure.The results indicated that there was an upward trend in CLUE in China from 2000 to 2020,with an increase rate of 2.62%.The temporal evolution of CLUE in China could be classified into three distinct stages:a period of fluctuating decrease(2000-2007),a phase of gradual increase(2008-2014),and a period of rapid growth(2015-2020).The major grain-producing areas(MPAs)had a lower CLUE than their counterparts,namely,non-major grain-production areas(non-MPAs).The spatial agglomeration effect followed a northeast-southwest strip distribution;and the movement path of barycentre revealed a"P"shape,with Luoyang City,Henan Province,as the centre.In terms of influencing factors of CLUE,investment in science and technology played the most vital role in improving CLUE,while irrigation index had the most negative effect.It should be noted that these two influencing factors had different impacts on MPAs and non-MPAs.Therefore,relevant departments should formulate policies to enhance the level of science and technology,improve irrigation condition,and promote sustainable utilization of cultivated land.

Study on Dynamic Changes of Land Utilization and Landscape Layout in Pearl River Estuary

Taking advantage of remote sensing(RS) technology and geographic information system(GIS) technology to interpret the four periods' data of remote sensing images of Pearl River Estuary in the years of 1990,1995,2000,and 2005,the changes in land utilization and landscape layout of Pearl River Estuary have been analyzed with reference to land utilization dynamic model and quantitative method in landscape ecology.Results indicate several points as followings.①Located in the region typical of high-speed economic development,Pearl River Estuary shows noticeable changes in land types and evident spatial temporal difference.During these 15 years,the areas of cultivated land and forests have experienced dramatic decline while the land for construction purposes shows the trend of powerful increase.②On the prospect of variation,landscape metrics have indicated great differences among other landscape pattern indices except for Area-Weighted Mean Patch Fractal Dimension(AWMPFD) especially during the period from 1990 to 1995 which experiences the most obvious changes.③On the prospect of landscape,landscape pattern indices also indicate great changes in the landscape layout of Pearl River Estuary from 1990 to 2005 as well as noticeable increase in the number of patches,and various landscape pattern indices show the increase in the degree of regional landscape fragmentation and increase in diversity.