A New Indicator for Global Food Security Assessment: Harvested Area Rather Than Cropland Area

Cropland area has long been used as a key indicator of food security.However,grain yield is not solely controlled by the area of the cropland.Therefore,we proposed a new indicator to assess food security.Results show that from 1992 to 2004,the global cropland area increased by 840200 km^(2)(99.4%),but the grain yield increased only by 310 million t(29.1%);and from 2004 to 2015,the cropland area decreased by 39000 km^(2)(4.64%),but the grain yield increased by 370 million t(70.84%).This result showed that grain yield was not linearly correlated with cropland area,and delimiting the threshold of cropland protection may not guarantee food security.Combined with further correlation analysis,we found that the increase in the global grain yield was more closely related to the harvested area(R^(2)=0.94),which indicated that the harvested area is a more scientific and accurate indicator than cropland area in terms of guaranteeing food security.Therefore,if governments want to ensure the food security,they should choose a new and more accurate indicator:harvested area rather than cropland area.

Reconstruction of cropland area in the European part of Tsarist Russia from 1696 to 1914 based on historical documents

To evaluate the climatic and ecological impacts of anthropogenic activities in global change research,it is essential to reconstruct historical land use and land cover change on regional and global scales.In this study,we reconstructed cropland areas for 54 provinces within the European part of Tsarist Russia(ETR)over the periods of 1696–1914 using historical data,including cropland area,population,grain consumption,and grain yield per unit area.The main results are as follows.(1)Total cropland areas and fractional cropland areas of ETR for 8 time sections during 1696–1914 were reconstructed,the former increased from 31.98×104 km2 to 147.40×104 km2,and the latter increased from 7.89%to 29.20%.The per capita cropland area decreased from 0.0246 km2 to 0.0113 km2 during 1696–1914.(2)Cropland expanded from the central and southwestern ETR to the black soil region,surrounding area of the Volga River,Ukraine region,the new Russia region,the vicinity of Ural,and north Caucasus region.(3)The expansion of territory,increase and migration of population,policies related to agricultural development and foreign trade,and the impacts of climate change were the reasons for the changes in cropland within ETR from 1696 to 1914.(4)In 1914,the cropland area and fractional cropland area of each province varied from 0.16×104 km2 and 0.76%to 5.65×104 km2 and 76.68%,respectively.(5)The comparisons show that the cropland areas of ETR in this study for 1696–1914 are higher than those in the HYDE 3.2 dataset.The main reason for this finding might be the underestimation of per capita cropland areas in the HYDE 3.2 dataset,which values remained at approximately 0.01 km2 from 1700 to 1920.

Mapping rice-fallow cropland areas for short-season grain legumes intensification in South Asia using MODIS 250 m time-series data

The goal of this study was to map rainfed and irrigated rice-fallow cropland areas across South Asia,using MODIS 250 m time-series data and identify where the farming system may be intensified by the inclusion of a short-season crop during the fallow period.Rice-fallow cropland areas are those areas where rice is grown during the kharif growing season(June–October),followed by a fallow during the rabi season(November–February).These cropland areas are not suitable for growing rabi-season rice due to their high water needs,but are suitable for a short-season(≤3 months),low water-consuming grain legumes such as chickpea(Cicer arietinum L.),black gram,green gram,and lentils.Intensification(double-cropping)in this manner can improve smallholder farmer’s incomes and soil health via rich nitrogen-fixation legume crops as well as address food security challenges of ballooning populations without having to expand croplands.Several grain legumes,primarily chickpea,are increasingly grown across Asia as a source of income for smallholder farmers and at the same time providing rich and cheap source of protein that can improve the nutritional quality of diets in the region.The suitability of rainfed and irrigated rice-fallow croplands for grain legume cultivation across South Asia were defined by these identifiers:(a)rice crop is grown during the primary(kharif)crop growing season or during the north-west monsoon season(June–October);(b)same croplands are left fallow during the second(rabi)season or during the south-east monsoon season(November–February);and(c)ability to support low water-consuming,short-growing season(≤3 months)grain legumes(chickpea,black gram,green gram,and lentils)during rabi season.Existing irrigated or rainfed crops such as rice or wheat that were grown during kharif were not considered suitable for growing during the rabi season,because the moisture/water demand of these crops is too high.The study established cropland classes based on the every 16-day 250 m normalized difference vegetation index(NDVI)time series for one year(June 2010–May 2011)of Moderate Resolution Imaging Spectroradiometer(MODIS)data,using spectral matching techniques(SMTs),and extensive field knowledge.Map accuracy was evaluated based on independent ground survey data as well as compared with available sub-national level statistics.The producers’and users’accuracies of the cropland fallow classes were between 75%and 82%.The overall accuracy and the kappa coefficient estimated for rice classes were 82%and 0.79,respectively.The analysis estimated approximately 22.3 Mha of suitable rice-fallow areas in South Asia,with 88.3%in India,0.5%in Pakistan,1.1%in Sri Lanka,8.7%in Bangladesh,1.4%in Nepal,and 0.02%in Bhutan.Decision-makers can target these areas for sustainable intensification of short-duration grain legumes.

Reconstruction of Lu-level cropland areas in the Northern Song Dynasty （AD976-1078）

Based on data on taxed-cropland area and on the number of households in historical documents, a probabilistic model of cropland distribution and a cropland area allocation model were designed and validated. Cropland areas for the years AD976, 997, 1066, and 1078 were estimated at the level of Lu（an administrative region of the Northern Song Dynasty）. The results indicated that（1） the cropland area of the whole study region for AD976, 997, 1066, and 1078 was about 468.27 million mu（a Chinese unit of area, with1 mu=666.7m2）, 495.53 million mu, 697.65 million mu, and 731.94 million mu, respectively. The fractional cropland area（FCA） increased from 10.7% to 16.8%, and the per capita cropland area decreased from 15.7 mu to 8.4 mu.（2） With regard to the cropland spatial pattern, the FCA of the southeast, north, and southwest regions of the Northern Song territory increased by 12.0%, 5.2%, and 1.2%, respectively. The FCA of some regions in the Yangtze River Plain increased to greater than 40%, and the FCA of the North China Plain increased to greater than 20%. However, the FCA of the southwest region（except for the Chengdu Plain） in the Northern Song territory was less than 6%.（3） There were 84.2% Lus whose absolute relative error was smaller than 20% in the mid Northern Song Dynasty. The validation results indicate that our models are reasonable and that the results of reconstruction are credible.

Evaluation of global land cover maps for cropland area estimation in the conterminous United States

Global land cover data could provide continuously updated cropland acreage and distribution information,which is essential to a wide range of applications over large geographical regions.Cropland area estimates were evaluated in the conterminous USA from four recent global land cover products:MODIS land cover(MODISLC)at 500-m resolution in 2010,GlobCover at 300-m resolution in 2009,FROM-GLC and FROM-GLC-agg at 30-m resolution based on Landsat imagery circa 2010 against the US Department of Agriculture survey data.Ratio estimators derived from the 30-m resolution Cropland Data Layer were applied to MODIS and GlobCover land cover products,which greatly improved the estimation accuracy of MODISLC by enhancing the correlation and decreasing mean deviation(MDev)and RMSE,but were less effective on GlobCover product.We found that,in the USA,the CDL adjusted MODISLC was more suitable for applications that concern about the aggregated county cropland acreage,while FROM-GLC-agg gave the least deviation from the survey at the state level.Correlation between land cover map estimates and survey estimates is significant,but stronger at the state level than at the county level.In regions where most mismatches happen at the county level,MODIS tends to underestimate,whereas MERIS and Landsat images incline to overestimate.Those uncertainties should be taken into consideration in relevant applications.Excluding interannual and seasonal effects,R 2 of the FROM-GLC regression model increased from 0.1 to 0.4,and the slope is much closer to one.Our analysis shows that images acquired in growing season are most suitable for Landsat-based cropland mapping in the conterminous USA.

淮河流域典型农田区气溶胶散射特性的日变化和季节变化研究

利用2019年寿县国家气候观象台气溶胶散射系数、气溶胶质量浓度及相关气象观测数据,统计分析了淮河流域农田区域的气溶胶散射特征及其成因,为该区域气溶胶污染辐射强迫及其对农业生产影响方面的研究提供了定量观测证据。研究表明:该地区气溶胶散射系数具有显著的季节变化规律,冬季最高,夏季最低;三个波长(450、525、635 nm)气溶胶日平均散射系数分别为329.8±180.0、270.2±153.7、214.4±128.4 Mm^(-1),并且散射系数日变化与天气要素和大气层结日变化规律具有很好的相关性,且冬季日振幅远小于其他三季;?ngstr?m指数年平均值为1.32,后向散射比年平均值为0.15,气溶胶质量散射系数年平均值为4.83 m^(2)/g,表明淮河流域农田区域的气溶胶以细颗粒为主;气溶胶散射系数大小主要受偏西风调控,散射系数与能见度具有高度的负相关幂函数关系;污染日的气溶胶散射系数远大于清洁日,污染物很大程度上影响了光辐射在大气中的传输能力,污染程度高,大气的散射作用就越强。

黑河中游耕地变化与节水灌溉对地表耗水与地下水的影响

为探究黑河中游耕地面积变化与节水灌溉影响下地表水耗水及地下水动态演变特征,基于1985—2022年黑河莺落峡、正义峡水文站实测径流量月数据和中游地区49眼地下水观测井埋深月数据,结合对节水灌溉的实地调研结果,利用统计分析等方法,分析了地表水耗水和地下水埋深对耕地面积变化与节水灌溉的响应。结果表明:耕地面积变化、节水灌溉和水量统一调度多重影响下,黑河中游地表水耗水量略有下降;黑河中游地下水埋深总体呈增大趋势,扩耕较大的大满灌区东南部与东北部及友联灌区中部地下水埋深明显增大;不同灌溉方式对地下水埋深也有较大影响,河灌区地下水埋深随地表水入渗补给量变化,井灌区和混灌区地下水埋深随地下水开采量变化。

平原煤粮主产复合区煤矿开采和耕地保护协同发展研究现状及对策

耕地是粮食安全的基础,煤炭是能源安全的保障。我国煤炭和耕地资源分布重合的煤粮复合区面积约占耕地总面积的42.7%,煤炭开采与耕地保护之间的矛盾十分突出。如何实现煤矿开采与耕地保护协同发展是我国煤粮复合区亟待解决的瓶颈难题。从平原煤粮复合区采动耕地损毁机理、采动耕地破坏程度评价、开采沉陷控制技术等3个方面分析了煤矿开采和耕地保护协同发展的研究现状与存在问题。在此基础上结合耕地保护面积大、变形耐忍度高等特点,提出了一种面向煤矿开采和耕地保护协同发展的源头控制与修复治理有机结合的绿色开采区域性岩层及地表变形控制技术途径,建立了相应的地表变形预测及控制设计方法,并指出了平原煤粮复合区煤矿开采和耕地保护协同发展的重点研究方向:平原煤粮复合区耕地采损驱动机制、采煤沉陷耕地防护阈值体系、面向耕地保护的煤矿绿色开采区域沉陷协调控制理论与方法,以期推动煤粮主产复合区煤矿绿色开采与耕地保护协同发展。

农田生境对大熊猫国家公园鸟类多样性的维持作用

农田生境被认为保护价值低,常被排除在自然保护地外。保护地内农田生境对生物多样性维持的价值和作用,现尚缺乏科学评估。2022年6月——2023年7月,对大熊猫国家公园成都片区农田生境的鸟类资源进行了调查,共调查记录鸟类12目44科151种4025只,国家重点保护野生鸟类19种,中国特有鸟类9种。鸟类物种丰富度和多度均以林鸟最为丰富,其次为广布型鸟。在不同食性鸟类组成中,以食虫鸟类物种丰富度和多度最丰富,其后依次为杂食性食植性。结果表明大熊猫国家公园成都片区农田生境鸟类多样性较高,同时对食虫鸟类和杂食性鸟类多样性的维持具有重要作用。建议在保护地建设和管理时合理保留其内的农田及传统自然村落,以示范人与自然和谐和传承当地的传统耕作文化。

中南半岛农田/森林活跃火与人口密度的相关性动态特征

人类活动是活跃火发生发展的重要诱因,明确人-火关系对火情规律揭示、碳排放估算与公共健康管理等具有重要意义。利用2003—2019年MODIS Collection 6(MODIS C6)活跃火和LandScan人口密度数据产品,基于GIS公里渔网、双变量空间相关性等分析方法,定量揭示了中南半岛农田/森林活跃火发生强度与人口分布的时空关联特征及其动态发展特征。结果表明:1)中南半岛约八成“有火区”的活跃火发生强度与人口密度存在空间正相关,且中等正相关及以上(r>0.4)格网近占3/4,主要分布在泰国中/东部、缅甸东/西部、老挝北部和柬埔寨东北部等。2)中南半岛年内“农火区”人口多于“林火区”,且前者超九成格网、后者近3/4格网与人口分布存在空间正相关性。3)“农火区”强正相关格网主要分布在缅甸南部、泰国中/东部等人口密度为25~100人/km^(2)的区域,而“林火区”相应格网多分布于缅甸东/西部、老挝北部、柬埔寨东北部等人口密度<25人/km^(2)的区域。4)受人口增长影响,2003—2010年农火和林火发生强度与人口分布相关性虽均明显高于2011—2019年,但后期“农火区”与“林火区”年均人口均有明显增幅。

土壤污染研究领域进展的中文文献调研

为了对我国农田土壤污染的研究现状以及研究趋势和热点聚焦有更深刻的了解,本文对1991—2021年CNKI中国期刊全文数据库收录的中文文献进行检索,使用可视化工具CiteSpace进行可视化分析并用Excel进行统计分析,梳理我国农田土壤污染研究的现状。结果表明:(1)我国农田土壤污染研究分为3个阶段:起步期(1991—2001)、逐步发展期(2002—2013)、成熟期(2014—2021)。目前,我国农田土壤污染研究处于快速发展期,总发文量逐年上升,但核心期刊发文量占比在30%~40%波动,整体呈下降趋势;(2)我国农田土壤污染研究已经形成了一批以骆永明、滕应、吴龙华等为核心作者的研究团队,但各个研究团体之间的联系不深、合作性较低;(3)重金属污染是我国农田土壤污染研究的主要方面;(4)该领域的研究前沿为源解析、镉污染、生态风险和钝化等方面;(5)我国农田土壤污染研究具有区域差异性,主要表现为南方农田土壤污染研究的数量多于北方,主要的粮食产区如长江三角洲和珠江三角洲的农田土壤污染研究也较多。

混合U-Net模型下南方丘陵地区耕地识别

针对南方丘陵地区耕地零散、破碎、不规则导致的山垅田识别难度大、准确率低等问题,本文在U-Net网络基础上,引入高效通道注意力(ECA)和注意力门(AG)双注意力机制,提出了混合U-Net模型,并应用于福建省南安市2021年WorldView-2卫星影像的耕地提取。试验表明:混合U-Net模型识别的耕地取得了较好精度,总体精度达到93.42%,优于单一注意力机制模型ECA U-Net和U-Net模型,分别提升了9.75%和19%;混合U-Net模型在山区、半丘陵、平原3个不同地形的测试区域,耕地F1分数平均值分别为0.9212、0.9025、0.9322,特别是在山区、半丘陵地区较ECA U-Net和U-Net模型结果提升明显。在此基础上,对南安市耕地空间分布进行了分析,为山垅田撂荒复耕种粮、合理调整25°以上坡耕地、耕地数量管控提供了有效技术支持。

基于氮磷养分管理的畜禽场粪便匹配农田面积

该文基于种养平衡的生态模式,根据上海地区单位饲养规模畜禽场粪便产生量及其氮磷含量和各类农作物氮磷需求量,研究分析了基于氮磷养分管理的单位养殖规模畜禽场产生的粪便还田利用需匹配的三大类农作物种植面积。结果表明:在畜禽粪便作为农作物氮磷养分的来源和满足农作物氮养分需求的前提下,根据农作物对氮磷养分需求的木桶效应,各类畜禽粪便提供的磷养分总体上超过各类农作物对磷养分的需求量,具有流失污染环境的隐患。因此,提出了畜禽场粪便还田利用农田面积匹配应基于农作物磷养分需求,不足的氮养分可通过化肥氮给予补充,从而达到种养结合、环境友好的畜禽生态养殖。

近10年来甘肃省粮食生产现状及增产途径分析

明确甘肃省粮食生产能力及其进一步提高的途径,对未来保障区域粮食安全具有重要意义。通过调查近10年来甘肃省耕地面积、粮食播种面积、粮食总产量、粮食单产等数据资料,探讨耕地面积、粮食播种面积、粮食总产量和粮食单产之间的相互关系,以阐明甘肃省粮食生产的潜力及其主要影响因素。结果表明,甘肃省耕地面积和粮食播种面积在近10年间呈先下降后上升的趋势,二者呈显著线性相关(P<0.01);粮食总产量和单产波动上升,但粮食播种面积的变化对粮食总产量无显著影响,单产提高是引起粮食总产量增加的主要因素。分析认为提高单位面积的粮食生产能力是保障甘肃省粮食安全的主要出路,而提高旱地粮食单产则是实现甘肃省新增25亿kg粮食的主要突破口。

西藏主要农区农田土壤肥力状况研究

西藏由于其特殊的地理位置、气候类型和地质历史以及耕作习惯,使其具有特殊的土壤特征.在2002～2004年间,我们对西藏主要农业区的林芝、拉萨、日喀则、山南等4地(市)的农田土壤进行了采样分析,分析结果显示:4地(市)农田土壤酸碱性由弱酸性至弱碱性(pH 6.5～9.0);养分的基本状况是有机质含量在5～50 g/kg之间,变幅较大,N素少(全N 0.2～2 g/kg,速效N 20～80 mg/kg),P素缺(全P 0.22～1.42 g/kg,速效P1～133 mg/kg),K素(全K 1.9～12.2 g/kg,速效K 80～1290 mg/kg)和微量元素比较丰富(Cu10～443mg/kg,Zn47～266mg/kg,Fe 1880～7550mg/kg,Mo0.2～6.6mg/kg,Mn 196～736mg/kg,B 0.5～138mg/kg).

广西耕地资源变化与粮食安全分析

在详细分析2000—2008年广西耕地变化趋势及造成耕地减少原因的基础上,采用最小人均耕地面积及耕地压力指数等方法,对粮食安全状况进行了研究,同时详细分析了工业化发展所处阶段及经济发展与耕地资源变化之间的关系,并结合广西新一轮土地利用总体规划预测的社会经济发展目标,运用统计分析方法预测了2020年耕地保有量。结果表明,广西2000-2008年粮食生产处于供不足需的状态,且处于工业化初期阶段,其工业化发展及城镇化的提高是建立在耕地资源的占用之上。

干旱半干旱区农田土壤碳垂直剖面分布特征研究

以中国干旱半干旱区农田土壤为研究对象,通过收集自然农田和长期定位站点（178个剖面,0~100 cm土层）农田土壤碳的数据并对其进行整合,分析了农田土壤有机碳和无机碳含量的垂直剖面分布特征及其影响因素。结果表明,随土层深度增加,农田土壤有机碳呈下降趋势,表层含量高于底层;不同地区农田土壤无机碳含量变化趋势不一,随土壤深度增加整体呈现升高的趋势,但是也有一些地区呈现下降趋势。土壤剖面深度为100 cm的农田土壤有机碳和无机碳密度平均值分别为8.33和15.83 kg m-2,农田土壤无机碳储量大约是土壤有机碳的2倍。土壤深度为0~30 cm的有机碳占100 cm总有机碳含量的45%,无机碳仅占100 cm总无机碳含量的29%;土壤无机碳主要集中在30~100 cm土层,占100 cm总无机碳含量的71%,远高于有机碳在此土层占100 cm总有机碳含量的百分比（55%）。综合自然农田和长期定位站点农田土壤碳的数据,土壤容重与土壤p H是影响农田土壤有机碳和无机碳分布特征的重要因素：自然农田土壤有机碳与土壤p H（R2=0.61,p〈0.01）和土壤容重（R2=0.64,p〈0.01）呈显著负相关;长期定位站点土壤无机碳与土壤p H（R2=0.56,p〈0.01）和土壤容重（R2=0.63,p〈0.01）呈显著正相关。中国干旱半干旱区农田土壤有机碳和无机碳的分布特征与影响因素,将为陆地生态系统碳储量估算提供数据基础与理论支撑。

陕西省采矿业污染农田土壤中Cd、Pb的释放特征

【目的】研究陕西省采矿业污染农田土壤中Cd、Pb的分布及其释放特征。【方法】以采自陕西凤县、潼关、洛南某铅锌矿区污染农田土壤（FX、TG、LN）为研究对象，测定不同粒径土壤中Cd、Pb的总量和有效态量，并对不同农田土壤中Cd、Pb的化学形态进行了探讨，采用批处理法对FX、TG、LN土壤中Cd和Pb的释放动力学特征进行了分析。【结果】3个矿区污染农田土壤Cd总量均严重超标，TG和LN土壤Pb总量也达超标水平，FX、TG和LN土壤中Cd、Pb总量分别达到了107．84，218．62，179．29mg／kg及208．93，2216．61，1046．24mg／kg。3种土壤不同粒径土样中Cd、Pb总量均随着土壤粒径减小而增加，3种土壤Cd、Pb有效态量从大到小依次为TG〉LN〉FX。FX、TG、LN土壤中Cd有效态量分别为11．59～16．73，21．10～23．07，16．01～16．73mg／kg；Pb有效态量分别为18．30～25．05，140．22～210．59，25．81～44．06mg／kg。化学形态分析表明，在3种土壤中Cd、Pb均以碳酸盐结合态和硫化物态为主，水溶态所占比例较小；在FX土壤中未检测到水溶态Cd和Pb，在LN土壤中未检测到水溶态Pb。在污染土壤中水溶态cd、Pb的释放基本在12h以后达到平衡，其释放过程分为快速释放、慢速释放和动态平衡3个阶段，其释放规律符合准二级动力学过程。【结论】陕西省采矿业已经造成严重的农田土壤重金属污染，FX、TG和LN3种污染土壤中Cd、Pb的释放与土壤粒径以及重金属污染物的来源密切相关，水溶态Cd、Pb的释放过程是复杂的非均相扩散过程。

我国粮食主产区耕地复种指数变化特征与潜力分析

为了解粮食主产区耕地复种指数变化特征与潜力,进一步挖掘粮食主产区的生产能力,稳定全国粮食安全大局,利用1979-2008年统计资料,对我国粮食主产区耕地面积、农作物总播种面积、粮食播种面积进行分析,并采用最大复种指数与热量、水资源之间的定量化关系模型,分析粮食主产区的复种指数理论潜力和可挖掘潜力。结果表明:1979-2008年期间我国粮食主产区耕地面积减少,农作物播种面积增加,粮食总产量与单产攀升,粮食总产量占全国比重升高,耕地复种指数东北区、黄淮海区上升,长江中下游地区下降。以2008年的耕地复种指数为参照,东北区、黄淮海区、长江中下游区理论可挖掘潜力分别为28%、48%、94%。

长江三角洲耕地数量变化趋势及总量动态平衡前景分析

论文利用长江三角洲地区近50年长序列耕地统计、近10多年土地利用调查数据及相关社会经济资料,重点从长江三角洲耕地数量变化的阶段性及与经济发展水平之间关系宏观分析的角度,探讨该区未来10～15年耕地变化趋势及实施区域耕地总量动态平衡的可能性。分析表明,长江三角洲耕地面积随人均GDP的增长呈良好的指数减少关系,人均GDP低于12000元/人,经济增长占用耕地的压力较大;人均GDP超过30000元/人时,这种压力将开始显著减缓。现阶段长江三角洲仍处于经济发展对耕地的压力较大的发展阶段,但已较1995年前明显减轻,估计至2004年前后,该区经济增长对耕地的压力将开始得到缓解。按现有的土地复垦整理补充耕地的投资力度,至2010年耕地面积仍将比1998年减少5.5×104hm2左右,若加大复垦整理的投资力度至现状水平的2倍,则保持耕地数量不减少也是可能实现的。