Gridding cropland data reconstruction over the agricultural region of China in 1820

Recent studies have demonstrated the importance of LUCC change with climate and ecosystem simulation, but the result could only be determined precisely if a high-resolution underlying land cover map is used. While the efforts based satellites have provided a good baseline for present land cover, what the next advancement in the research about LUCC change required is the development of reconstruction of historical LUCC change especially spatially-explicit historical dataset. Being different from other similar studies, this study is based on the analysis of historical land use patterns in the traditional cultivated region of China. Taking no account of the less important factors, altitude, slope and population patterns are selected as the major drivers of reclamation in ancient China, and used to design the HCGM （Historical Cropland Gridding Model, at a 60 km×60 km resolution）, which is an empirical model for allocating the historical cropland inventory data spatially to grid cells in each political unit. Then we use this model to reconstruct cropland distribution of the study area in 1820, and verify the result by prefectural cropland data of 1820, which is from the historical documents. The statistical analyzing result shows that the model can simulate the patterns of the cropland distribution in the historical period in the traditional cultivated region efficiently.

Land Use Regionalization of Rural Settlements in China

This paper compartmentalizes regional land use of rural settlements in China by employing a hierarchical clustering method.The statistic data are sourced from the National Bureau of Statistics of China(NBSC) and the data of land use change from the Ministry of Land and Resources of China(MLRC).The population of rural settlement decreases from the southeast to the northwest of China and the density of rural settlement decreases from the east to the west of China.Land-use scale of rural settlement,the proportion of one-storey houses and the average household area decrease from the north to the south of China.The ratio of area of cultivated land to rural settlement is high in the northeast and southwest of China but low in the southeast of China.The land use regionalization of rural settlement can be divided into four regions,namely:the northern region of China,Qinghai-Tibet,Yunnan-Guizhou,and the middle and eastern region of China.The northern region of China and the middle and eastern region of China can be further divided into nine sub-regions:Xinjiang,Northeast China,Ningxia and Inner Mongolia,North China,the south of the Changjiang(Yantze) River and Sichuan Basin,Jiangsu-Shanghai,South China,the Loess Plateau,and Guangxi.In consideration of the significant regional differences,it is proposed that different policies should be implemented regarding the utilization and management of rural settlements.

Establishment of Rural Housing Land Standard in China

On the basis of rural household survey in 12 provinces of China in 2005,this research built an econometrical model to find the area standard for rural housing land.This standard is expected to facilitate rural housing land administration,efficient and intensive housing land use and policy making.This research concludes:1) according to the household survey data,the average area for rural housing land in China is about 235.26 m 2,and the rural housing land mainly includes unused land(42.89%) and house construction land(37.76%) with the average floor-area ratio of 0.42;2) the indexes in the standard concern the factors such as location,landform,house form,household population and cultivated land area per farmer,which all have significant effects on rural housing land use;3) the reasonable area for rural housing land may be 150 m 2 in average before 2020,and the referential standards in different provinces are 120 m 2,130 m 2,140m 2,150 m 2,160 m 2,170 m 2,190 m 2,200 m 2,210 m 2,220 m 2,230 m 2 and 250 m 2 respectively;and 4) if there are less than two persons or more than five persons in a family,these standards need to be decreased or increased by 7%.When the cultivated land area per farmer is lower than the provincial average,the standards have to reduce by 3.5%.

Preliminary Analysis of Population Genetic Diversity of Cultivated Laminaria japonica Sporophyte via AFLP Technique

The amplified fragment length polymorphic DNA (AFLP) technique was adopted to estimate the population genetic polymorphism among 30 sporophytes of Laminaria japonica collected from a cultivating farm in Rongcheng,China.Three methods were used for genomic DNA extraction from Laminaria japonica sporophyte and only the products obtained using the improved genomic DNA extraction kit method proved qualified for AFLP analysis.The parameters of the method were optimized.Samples of forty milligrams and the cell lysis time of 120 min were suggested to replace the parameters recommended by the manufacturer.Thirty individuals of Laminaria japonica from the same cultivating site were investigated using one pair of selective primers.A total of 21 loci were obtained and 17 of them were polymorphic.The mean percent age of polymorphic loci of this population was 80.95%.The Nei's gene diversity (H) within this population was 0.3028 and the average Shannon's Information index (I) was 0.4498.A genetic distance matrix among different individuals was constructed as well.Through this study,an applicable AFLP genetic analysis working system for Laminaria japonica sporophyte was established.The results of this research also revealed a high level of genetic diversity within the studied population.

Reconstructing Spatial Distribution of Historical Cropland in China′s Traditional Cultivated Region: Methods and Case Study

As an important part of land use/cover change(LUCC), historical LUCC in long time series attracts much more attention from scholars. Currently, based on the view of combining the overall control of cropland area and ′top-down′ decision-making behaviors, here are two global historical land-use datasets, generally referred as the Sustainability and the Global Environment datasets(SAGE datasets) and History Database of the Global Environment datasets(HYDE datasets). However, at the regional level, these global datasets have coarse resolutions and inevitable errors. Considering various factors that influenced cropland distribution, including cropland connectivity and the limitation of natural and human factors, this study developed a reconstruction model of historical cropland based on constrained Cellular Automaton(CA) of ′bottom-up′. Then, an available labor force index is used as a proxy for the amount of cropland to inspect and calibrate these spatial patterns. Applied the reconstruction model to Shandong Province, we reconstructed its spatial distribution of cropland during 8 periods. The reconstructed results show that: 1) it is properly suitable for constrained CA to simulate and reconstruct the spatial distribution of cropland in traditional cultivated region of China; 2) compared with ′SAGE datasets′ and ′HYDE datasets′, this study have formed higher-resolution Boolean spatial distribution datasets of historical cropland with a more definitive concept of spatial pattern in terms of fractional format.

Changes in Land Use and Agricultural Production Structure Before and After the Implementation of Grain for Green Program in Western China–Taking Two Typical Counties as Examples

Soil erosion becomes a serious environmental problem in the world, especially in western China. An effective management practice called the Grain for Green Program(GGP), which was launched in 1999, aims to reduce soil and water loss and alleviate the ecological environment problem in western China. Two typical counties in western China, the Zhongxian(in Chongqing Municipality) and Ansai(in Shaanxi Province) were chosen to evaluate the dynamic changes of land use and agricultural production structure before and after the implementation of the Program in this paper. The results showed that the cultivated land area was reduced by 7.08% from 1989 to 2003. The cultivated land per person was decreased by 8.42% during 1999-2003. Moreover, the stability index of the secondary sector of the economy was increased from 0.91 in the period 1990-1999 to 0.94 in the following ten years. In addition, the stability index of tertiary economic sector increased from 0.88 to 0.92 in Zhongxian county. Meanwhile, the cultivated land area was reduced by 15.48% from 1990 to 1999. The soil erosion modulus was decreased by 33.33% from 1999 to 2006. Also, the stability index of secondary and tertiary economic sectors was 0.86 in the period 1998-2002. However, it decreased by 77% during 2002 to 2007 in Ansai County. These results imply that the Grain for Green Program had different impact on the two regions. Several effective strategies of soil and water conservation have been carried out to ameliorate the sustainable development of ecological environment and economy in these two counties of western China.

Grain Production Driven by Variations in Farmland Use in China:An Analysis of Security Patterns

自从1978年改革开放以来,随着经济的迅速发展,中国的耕地利用格局发生了很大的变化。耕地数量和质量的变化直接导致粮食生产的变动。本文利用来自政府部门的农业统计数据,分析了1978-2004年间中国耕地利用水平的时空动态格局,并通过构建"粮耕弹性系数"来反映耕地利用变化与粮食生产的互动关系。研究结果表明:耕地投入的增加和质量的提升在一定程度上缓解了1978年以来我国耕地资源严重流失给粮食生产安全带来的压力;自改革开放以来,中国耕地利用水平呈现由经济快速发展带来的普遍性提升局面,并随着经济发展程度由东南沿海向内陆递减,耕地利用水平的提升速率也呈现由东南沿海向内陆梯级递减态势。然而,耕地集约利用程度的不断提升,并不一定会带来粮食产量的持续稳定增长。耕地集约利用增长的边际效用递减特性,使得中国粮食生产安全的保障已逐步由耕地集约利用水平的提升转向了耕地面积的保护,由此导致耕地资源的数量成为了左右粮食生产安全的关键,这也为当今中国制定严格的耕地保护目标和战略提供了现实的科学依据。

Chinese Cropland Quality and Its Temporal and Spatial Changes due to Urbanization in 2000–2015

The acceleration of urbanization has led to the occupation of more cropland, especially higher quality cropland, which could pose a huge threat to food security and have other implications for the inadequate cropland resource supply in China. Though the spatial status of Chinese cropland quality has been assessed, its temporal changes since 2000 to 2015 are still not clear. An accumulated probability distribution method was used to determine the criteria of cropland quality using the net primary production data product(MOD17) from Moderate Resolution Imaging Spectroradiometer(MODIS). Then the cropland quality of higher, median and lower production was spatially mapped and its changes due to occupation by urbanization were analyzed through the land use changes(LUCC) data primarily from Landsat TM images in the three periods of 2000–2005, 2005–2010, and 2010–2015.The results showed that of the total cropland reduction area the proportion taken by urbanization increased from47.29% in the early stage to 77.46% in the recent period. The quality of Chinese cropland was dominated by lowand medium-yield fields, accounting for 40.81% and 48.74%, respectively, with high-yield fields accounting for only 10.44% of the total cropland in the country in 2000. The high-yield areas have been seriously threatened by the expansion of construction land fields, with the ratio of high-yield area to total area occupied by urbanization increasing from 9.71% in 2000–2005 to 15.63% in 2010–2015. Spatially, this phenomenon has been moving from eastern and southern China to central and western China, especially in Northwest China where the ratio has arrived at the highest proportion, with 52.97% of high-yield cropland in the total land taken by the expansion by 2015. This study not only provides a method to assess cropland quality but also reveals the threatening trend from the expansion of urbanization on high-quality cropland. More attention should be paid to the latter in land use planning and policies made to prevent threats to food security from declines in both cropland quantity and quality.

Progress on quantitative assessment of the impacts of climate change and human activities on cropland change

It is important to study the contributions of climate change and human activities to cropland changes in the fields of both climate change and land use change. Relationships between cropland changes and driving forces were qualitatively studied in most of the previous researches. However, the quantitative assessments of the contributions of climate change and human activities to cropland changes are needed to be explored for a better understanding of the dynamics of land use changes. We systematically reviewed the methods of identifying the contributions of climate change and human activities to cropland changes at quantitative aspects, including model analysis, mathematical statistical method, framework analysis, index assessment and difference comparison. Progress of the previous researches on quantitative evaluation of the contributions was introduced. Then we discussed four defects in the assessment of the contributions of climate change and human activities. For example, the methods were lack of comprehensiveness, and the data need to be more accurate and abundant. In addition, the scale was single and the explanations were biased. Moreover, we concluded a clue about quantitative approach to assess the contributions from synthetically aspect to specific driving forces. Finally, the solutions of the future researches on data, scale and explanation were proposed.