Regional disparity in the changes of agricultural land use intensity in China during 1980-2002

Based on the cost-benefit data （1980-2002） of farm products and China Agriculture Yearbooks, this paper studies the regional disparity in the changes of the agricultural land use in China during the period 1980-2002 from three aspects such as the degree of intensity, the sown area and the abandoned farmland. The results show that： （1） The degree of intensity of land use in the westena region during 1980-2000 has a strong uptrend, but in the eastern and central regions the degree of intensity descends obviously and has shown a continuous downtrend since 1997. （2） The total sown area shrinks notably in the eastern region, while it enlarges constantly in the western region. （3） The sown area in the eastern, central and western regions has gone through a similar cyclic process： down （1980-1985）-up （1985-1991）-down （1991-1994）-up （1994-1999）-down （1999-2002）. However, there are obvious differences in amplitude variation and tendency among them. The sown area has shrunk in the eastern region and expanded in the central and western regions especially before 1999. （4） The most cases of abandoned farmland are reported in the central region, the second in the eastern region and the least in the western region. The abandonment phenomena chiefly occurred during 1992-1995 in the eastern region, and during 1998-2002 in the central region.

Study of the intensity and driving factors of land use/cover change in the Yarlung Zangbo River, Nyang Qu River, and Lhasa River region, Qinghai-Tibet Plateau of China

Land use/land cover(LULC) is an important part of exploring the interaction between natural environment and human activities and achieving regional sustainable development. Based on the data of LULC types(cropland, forest land, grassland, built-up land, and unused land) from 1990 to 2015, we analysed the intensity and driving factors of land use/cover change(LUCC) in the Yarlung Zangbo River,Nyang Qu River, and Lhasa River(YNL) region, Qinghai-Tibet Plateau of China, using intensity analysis method, cross-linking table method, and spatial econometric model. The results showed that LUCC in the YNL region was nonstationary from 1990 to 2015, showing a change pattern with "fast-slow-fast" and "U-shaped". Built-up land showed a steady increase pattern, while cropland showed a steady decrease pattern. The gain of built-up land mainly came from the loss of cropland. The transition pattern of LUCC in the YNL region was relatively single and stable during 1990–2015. The transition pattern from cropland and forest land to built-up land was a systematic change process of tendency and the transition pattern from grassland and unused land to cropland was a systematic change process of avoidance. The transition process of LUCC was the result of the combined effect of natural environment and social economic development in the YNL region. This study reveals the impact of ecological environment problems caused by human activities on the land resource system and provides scientific support for the study of ecological environment change and sustainable development of the Qinghai-Tibet Plateau.

Land Use Land Cover Dynamics and Farmland Intensity Analysis at Ouahigouya Municipality of Burkina Faso,West Africa

Sahel zone has been reported as one of the most vulnerable regions to climate change, so serious attention must be paid to this zone by researchers and development actors who are interested in environmental-human dynamics and interactions. The aim of this study was to bring more insight into the impact of actions aiming at reducing land degradation, regreening the Sahel, stopping population migration and reducing the pressure on land in the Sahelian zone. The study focused on farmland dynamic in Ouahigouya municipality based on remote sensing data from 1986 to 2016 using intensity analysis. The annual time interval change was 0.77% and 2.46% for 1986-2001 and 2001-2016, respectively. Farmlands gained from mixt vegetation, water bodies and from bar lands. Mixed vegetation and water bodies were both active during both intervals while the other land use such as woodland and bar land were dormant. Combining land use land cover analysis and intensity analysis was found to be effective for assessing the differentiated impact of the various land restoration actions.

Spatial-Temporal Analysis of Territorial Transformations in the State of Sinaloa Mexico Using Geographic Information Systems

In the last years the whole planet has been suffering remarkable changes, including the land use and cover, and that this is one of the many components of the global change. The present study has as main objective described the changes of land use and cover occurred in the State of Sinaloa during the period 1976-2011. For this, we used 4 maps of land use and vegetation of 1976, 1993, 2007 and 2011. This analysis was carried out applying statistical techniques and Geographic Information Systems (GIS). The methodology is based on the analysis of the cross-tabulation matrix or change matrix, from which it is possible to obtain indicators of change for each time interval analyzed (1976-1993, 1993-2007 and 2007-2011), as well as the gain and loss of each of the 10 categories contained in the maps. To raise the level of details in the analysis were studied the annual changes considering for this the intensity of the gains and annual losses. Also we elaborated graphs and maps that allow us describing and identifying the magnitude and spatial distribution of the changes. The results obtained show a deterioration in the rainforest, important changes in the irrigated and seasonal agriculture and the spatial exchanges in the forest areas, as well as a considerable increase in the urban areas.

Subsidence associated with land use changes in urban aquifers with intensive extraction

Land use change is a major factor in alterations in natural processes and cycles. Remote sensing has become an excellent tool to evaluate technological changes in land cover and land use changes over large areas, such as those occurring in the Valley of San Luis Potosi (VSLP). Here, such changes have impacted a system which is 95% dependent on the aquifer. The methodology for the present study is based on the use of satellite images for the years 1976, 1986, 1995 and 2000. To asses land use change, a supervised classification process was used with a decision tree technique and ENVI 4.3 software. The evolution of groundwater levels for the years 1977, 1986, 1995, 1998 and 2007 was also analyzed, as well as problems of subsidence and fissuring in the urban area of the valley in 2006. With the support of remote sensing, it was possible to analyze the dynamic changes in land use over large areas and highlight their impact on the environment.

Spatiotemporal influences of land use/cover changes on the heat island effect in rapid urbanization area

Rapid urban sprawl and growth led to substantial urban thermal environment changes and influenced the local climate, environment, and quality of life of residents. Taking the Chang-Zhu-Tan urban agglomeration in China as a case, this study firstly identified the spatiotemporal patterns of surface urban heat island intensity (SUHII) and the land use/cover changes (LUCC) based on multi-temporal Landsat TM satellite data over 21 years, and then investigated the relationship between LUCC and SUHII by methods of logistic regression model and centroid shift analysis. The results showed that green spaces (e.g., cropland, forestland) of 899.13 km2 had been converted to built-up land during the 1994—2015 period, which caused significant urban expansion. The SUHII was the highest for built-up land, high for unused land, low for cropland and grassland, and the lowest for forestland and open water. Many areas experienced extensive rapid urbanization because of the emergence of the urban agglomeration, which resulted in the loss of green spaces and increased SUHI effects over the 21-year study period. In addition, the results of centroid shift analysis found that the growth of SUHII and the expansion of high SUHII areas are closely related to the expansion of an existing urban area in Xiangtan, while the increases of building density and height in Changsha resulted in the decrease of SUHII and spatiotemporal change of high SUHII areas. The analysis of the effects of land use/cover types on the SUHII in this study will contribute to future urban land use allocation for the mitigation of SUHI formation.

Exploring the spatio-temporal impacts of farmland reforestation on ecological connectivity using circuit theory:A case study in the agro-pastoral ecotone of North China

Farmland reforestation can contribute substantially to ecological restoration.Previous studies have extensively examined the ecological effects of farmland reforestation,but few of them have investigated the spatiotemporal responses of broad-scale landscape connectivity to reforestation.By using a typical agro-pastoral ecotone in northern China as a case study,we addressed this issue based on an innovative integration of circuit theory approach and counterfactual analysis.The forest connectivity through multiple dispersal pathways was measured using the circuit theory approach,and its spatiotemporal changes after reforestation were evaluated by counterfactual analysis.The results showed that from 2000–2015,the reforested farmland occupied 2095 km^2,and 12.5% was on steeply sloped land.Farmland reforestation caused a greater increase in ecological connectivity by adding new ecological corridors and stepping stones in scattered forest areas rather than in areas with dense forest distributions.The newly added corridors and stepping stones were fragmented,short and narrow and thus deserve powerful protection.Future reforestation to improve landscape connectivity should highlight pinch point protection and obstacle removal as well as the tradeoff between farmland loss and farmer survival.Our findings are expected to inform the optimization of the Grain for Green policy from the perspective of broad-scale biodiversity conservation.

Urban Heat Island and Land Use/Cover Dynamics Evaluation in Enugu Urban, Nigeria

This study specifically estimated the effect of land use/cover change (LULC) processes on land surface temperature (LST) in Enugu urban and its suburbs. With Landsat images and supervised classification technique, four LULC classes comprising built-up areas, vegetation, rock outcrop, bare ground/farmland areas were delineated. The LST was extracted from the thermal bands of the images. The rate of change in land cover classes between 2009 and 2018 showed that from 2009 to 2013, built-up areas increased from 31.65% to about 47.5%, while vegetation cover decreased from 18.43% to 11.23%. Also, the periods witnessed about 8.69 km2 of vegetation being converted to other land surfaces. The trend in the LST in Enugu urban showed the highest mean temperatures of 34.5°C in 2018 and 32.26°C in 2015. However, in 2013 there was a slight decrease in mean LST to 31.65°C which further decreased to 31.26°C in 2009. This change in temperature suggests that urbanisation could have significant effect on the micro-climate of Enugu city. Result also revealed weak relationships between LULC classes and the LST throughout the years. The results of the surface heat intensity for the urban and rural areas showed general increase over the years and this suggests that rural areas are also experiencing high temperature which could be due to the loss of vegetation, increase in artificial surfaces and urban encroachment. Findings from this study could be useful for effective urban land-use planning, policy development and management in Nigeria, and elsewhere.

Thermal performance of a lightweight building with phase change material under a humid subtropical climate

The use of phase change materials(PCMs)in building enclosures is an efficient way to reduce the heat gain and/or loss in summer and winter.It was evident that the thermal performance of buildings with PCMs was affected by the outdoor air temperature significantly.However,the influence of humidity,which was serious in the humid subtropical climate was unclear.To explore the effect of PCMs under a humid subtropical climate,the thermal performance of a lightweight building outfitted with PCMs with a melting temperature of 25°C was investigated.The actual outdoor air temperature with a humidity of 40-90 RH%and wind velocity of 2-6 m/s blowing from the east,west,south,and north was assumed for the performance assessment.A simulated model was developed using EnergyPlus and verified against experimental data.The energy savings by using PCMs was reduced from 3.9%to 2.6%when the outdoor humidity increased from 40 to 90 RH%in summer.However,the savings was not obvious in winter.Annual energy savings decreased from 1.64%to 1.32%with humidity increasing from 40 to 90 RH%.For annual condition,the average energy savings was reduced from 1.43%to 0.92%when the wind speed increased from 2 m/s to 6 m/s.From an economic point of view,the investment payback period was less than 10 years when the PCM price was lower than 18.0 Yuan/kg.

湖南省耕地变化与城市土地集约使用分析

文章以湖南省为研究区域,分析了最近5年来湖南省推进"三化"建设背景下耕地减少的时空特征,特别是建设占用耕地的变化特征。并通过分析城市使用土地(特别是耕地)的情况来探讨城乡一体化下,城市化与区域耕地减少的关系。研究表明:城市化建设有利于提高土地利用率,随着城市化进程的不断加快,只有集约利用土地,挖掘城市土地潜力,才能实现区域耕地动态平衡的目标,协调城市化推进与耕地保护的关系。

徐州市土地利用变化及驱动因素研究

以徐州市1990-2000年统计年鉴和徐州市国土资源局的土地利用现状调查和土地利用变更调查的数据为依据,分析了徐州市近10年土地利用变化的基本特征,并在统计软件SPSS的支持下,对徐州市农用地利用变化的驱动因素进行了主成分分析。研究表明:经济、人口、农业结构调整是徐州市农用地利用变化的主要原因。据此,提出了土地资源可持续利用的建议。

Disturbance impacts of land use change on biodiversity conservation priority areas across China： 1990-2010

Land use change is one of the main drivers of biodiversity loss. In the last 20 years, China＇s land use pattern has undergone profound changes. This study constructs an Eco- system Comprehensive Anthropogenic Disturbance Index （ECADI） to assess disturbance impacts of land use change between 1990 and 2010 on biodiversity conservation priority areas at national and regional scales. Four levels of biodiversity conservation areas were categorized： generally important areas, moderately important areas, important areas, and very important areas. The results indicated a higher ECADI value in 2010 in Central and Eastern China than in Western China, and the values of the moderately important, important and very important regions were lower than the average value of the whole country at all levels. Notably, in recent 20 years, the change extent of ECADI values in Central and Eastern China were much greater compared with that in Western China, and ECADI values in the moderately important, important and very important biodiversity conservation areas all showed increasing trends, with the increasing extent lower than that of whole China at all levels. Due to human activities such as urbanization in Eastern China and cropland reclama- tion in Northeast China and Xinjiang, ECADI values showed a medium increase trend （the change rate was about 1%-5% in 10 years）, which indicated the need for more conservation efforts in those regions. However, ECADI values in the Loess Plateau presented a low decline trend （the change rate was about-1% to -0.1% in 10 years） after 2000 because of the ob- vious effectiveness of Green for Grain Project. Furthermore, the variation was negligible in the Tibetan Plateau.

Experiments and analysis of gold disk targets irradiated by smoothing beams of Xingguang Ⅱ facilities with 350 nm wavelength

Gold disk targets were irradiated using focusing and beam smoothing methods on Xingguang (XG-Ⅱ) laser facilities with 350 nm wavelength,0.6 ns pulse width and 20-80 Joules energies. Laser absorption,light scattering and X-ray conversion were experimentally investigated. The experimental results showed that laser ab-sorption and scattered light were about 90% and 10%,respectively,under focusing irradiation,but the laser absorption increased 5%-10% and the scattered light about 1% under the condition of beam smoothing. Compared with the case of fo-cusing irradiation,the laser absorption was effectively improved and the scattered light remarkably dropped under uniform irradiation; then due to the decrease in laser intensity,X-ray conversion increased. This is highly advantageous to the in-ertial confinement fusion. However,X-ray conversion mechanism basically did not change and X-ray conversion efficiency under beam smoothing and focusing irra-diation was basically the same.

青藏高原东部典型区的劳动力析出与粮食产量增长——2005和2010年的跟踪调查及其解释（英文）

Although there has been rapid rural-urban migration in rural China since the 1980s, the total grain production of China saw a continuous increase. As of today, the relationship between labor migration and grain output growth remains partial and contradictory. The main aim of this empirical study is to examine some specific measures adopted by peasants to deal with labor shortage and maintain grain output growth. Using tracking survey, participatory rural appraisal methods, and land plot investigation, we investigate 274 households and 1405 arable land plots in four villages in two stages in Jinchuan county, southwestern China. The results show that continuous emigration of labor from the four villages caused the abandon- ment of a small amount of land, decreased labor intensity, and reduced multiple cropping index, shifting from ＂corn-wheat＂ multiple cropping pattern to the ＂corn＂ cropping pattern, which means labor shortage in some households. At the same time, owing to surplus labor in the villages, the peasants utilize a series of means to offset the negative impacts of labor migration on grain output, such as cropland transfer, labor exchange in the busy seasons, and the substitution of capital and technology for labor. The econometric analysis also shows that labor migration boosts grain production. This study provides a reasonable explanation of grain output growth under rural-urban migration.