1990-2010年中国耕地变化对粮食生产潜力的影响

1990年以来,在国家生态环境保护工程实施、经济快速增长等因素的影响下,中国耕地数量与空间格局发生了巨大变化,对粮食生产潜力造成了巨大影响。本文采用GAEZ模型,结合中国气象、地形、土壤等因素,定量分析了中国耕地粮食生产潜力空间特征以及1990-2010年中国耕地变化对粮食生产潜力的影响。主要结论如下：① 2010年全国耕地粮食生产潜力总量为10.55亿t,全国耕地平均粮食生产潜力为7614 kg/hm²。中国耕地粮食生产潜力存在显著的空间差异,总体表现为东部高而西北部较低的趋势,并且高值区主要分布在长江中下游地区和华南区。② 1990-2010年的20年间,中国耕地粮食生产潜力变化表现出明显的时空差异,总体呈现南减北增、总量减少的基本特征。新增耕地粮食生产潜力的重心逐步由东北向西北转移。耕地粮食生产潜力总量净减少297万t,占2010年全国实际粮食总产量的0.29%。③ 在1990-2000年与2000-2010年两个时期,耕地变化对耕地粮食生产潜力影响差异明显。前10年,耕地粮食生产潜力总量净增加1011万t,主要集中在东北平原区和北方干旱半干旱区;后10年,耕地粮食生产潜力总量净减少1308万t,主要集中在长江中下游地区和黄淮海平原区。从总体看,近20年来耕地粮食生产潜力总量增加主要是由林、草地和未利用土地开垦所导致,而耕地粮食生产潜力总量减少主要是由城市扩展和退耕还林还草所导致。     

近50年气候驱动下东北地区玉米生产潜力时空演变分析

利用GAEZ模型,综合考虑气象、土壤、地形等因素,估算1961-2010年东北玉米生产潜力,分析50年来气候变化导致的东北玉米生产潜力时空格局演变特征。研究发现：① 1961-2010年,东北玉米平均生产潜力波动较大,整体上以每10年80 kg/hm²的线性倾向率增加;② 由于气候变化,20世纪末、21世纪初玉米生产潜力变化较为频繁;③ 玉米生产潜力总值黑龙江省始终处于最高,近50年间增长幅度黑龙江省>吉林省>辽宁省;④ 近50年来,黑龙江省玉米生产潜力的波动较为剧烈,吉林省和辽宁省相对稳定;⑤ 近50年东北玉米适宜种植区有所增加,主要集中在黑龙江省西北地区,高生产潜力区域增加明显,呈现北移趋势。研究可为东北地区高效利用气候和土地资源,优化玉米生产布局提供依据。     

1951—2000年中国气候生产潜力时空动态特征

气候生产潜力时空动态一直是国内外全球变化研究的热点,基于1951-2000年全国范围气象栅格数据计算气候生产潜力,在此基础上,利用GIS空间分析技术和小波分析方法探讨全国以及9大土地潜力区气候生产潜力的空间格局特征与多时间尺度特征.结果表明:50年间中国气候生产潜力单产平均值为770 g·m-2·a-1,折算为总量达73.12×108t/a;全国及9大土地潜力区气候生产潜力的多时间尺度特征比较复杂,3～5年周期的年际变化和30年左右周期的年代际变化均较显著,而10～11年周期的变化则仅在部分区域有所表现;总的来说,1951-2000年,华北地区、黄土高原、内蒙古中部及辽河平原等是我国气候生产潜力时空动态特征最突出的区域.     

黄淮海平原气候变化及其对耕地生产潜力的影响

利用1991年和2000年黄淮海平原气象台站的历史观测资料,分析该地区气温、降水的变化趋势,并利用农业生态地带(AEZ)模型估算黄淮海平原各农业生态区的耕地生产潜力。通过分析气温、降水与耕地生产潜力的关系,评价气候变化对耕地生产潜力的影响。研究发现,黄淮海平原耕地生产潜力与降水量、气温呈显著正相关。对各农业生态区的回归分析表明,如果气温或降水量提高10%,耕地生产潜力将分别提高3.2%与0.3%。该研究对制订应对气候变化、保护耕地与提高耕地生产潜力方面的决策具有参考价值。     

60年来中国农业水热气候条件的时空变化

根据1951-2010年中国824个气象站点逐日观测数据选取与农作物生长密切相关的农业气候指标,按照年代将各指标站点数据空间化,求取前后期数据变化差值,分析中国农业水热气候条件的时空变化;进而对农业水热气候条件进行线性拟合,分析农业气候变化倾向。研究发现:60年来全国年平均气温、0℃积温和最冷月平均气温等值线均在不同程度上向北迁移,三者在全国大部分区域表现为显著增加趋势;全国最热月平均气温分成明显的下降和上升区,显著上升区集中在东北地区、内蒙古高原与东南沿海,黄河与长江中下游地区成为下降区;全国年降水量的增加趋势并没有通过显著检验。虽然对中国农业分布格局至关重要的400 mm等降水量线南段和800 mm等降水量线在整体上相对稳定,但是黄河与长江中下游地区最热月平均气温的下降趋势和最冷月平均气温等值线尤其是0℃等值线逐渐从秦岭—淮河一带北移到黄河一线,这对中国作物的分布、耕作制度等会产生重要影响。因此,高温、低温与农作物生长期热量供应以及水分的复杂变化对农业的影响将因区域差异与作物种类而变化,后续的研究可以考虑更多因素来分析农作物的适宜种植范围及区域农业对气候变化的适应。     

长江中下游地区湿地开垦及土壤有机碳含量变化

概述了历史时期至今,尤其是20世纪下半叶50 a来长江中下游地区湿地的开垦状况;总结了研究区湿地土壤及其开垦为农田后土壤有机碳含量的变化特征.长江中下游地区湿地分布广, 存在着湿地开垦强度大、土壤碳密度较低和土壤有机碳损失严重等土壤碳库变化问题.与原湿地土壤相比,湿地被开垦为农田后,土壤有机碳含量总体上在降低,而且随着湿地开发利用年限的增加,其土壤有机碳含量减少的幅度也在增加.     

河北省人口分布地域格局时空演变分析

基于分县数据,在分析人口空间分布地域格局的基础上,利用人口数量增减变化和人口稳定度对近30年来河北省人口分布格局时空变化进行了研究。结果表明:河北省人口密度分布呈"西北山地丘陵区密度低—东南平原区密度高"的模式,且呈现出人口密度"高密度—高密度"相邻和"低密度—低密度"相邻的分布模式;随着地区发展差异的显现以及城市化进程的明显加快,近30年来河北省各县域人口数量由普遍增加趋于人口增减频繁,人口集散进一步强化,集散程度明显提高,且在空间分布上人口减少或人口疏散地区多围绕人口显著增加或人口强集聚地区呈环状分布。     

近50年基于农作物种植结构的新疆绿洲农田蒸散发时空变化分析

基于农作物种植结构准确估算绿洲农田蒸散发,对中国西北干旱区水土资源优化配置和生态环境可持续发展有重要意义。利用1960-2010年县级农业统计数据和基于遥感提取的绿洲耕地分布数据,产生逐年的新疆绿洲三种农作物(棉花、小麦、玉米)种植比例时空分布数据集,并在此基础上利用Penman-Monteith单作物系数法估算农作物蒸散发。结果表明:1960-2010年全疆绿洲耕地面积持续增加,粮食作物占优势的单一种植结构类型已被经济作物替代,形成南疆棉花快速增加、北疆小麦快速减少的种植格局。近50年全疆三种农作物总蒸散发量增加了47.85%,棉花贡献率最高,其次为玉米,小麦最低。耕地面积和结构变化对绿洲农作物蒸散发时空分布和组成结构变化具有重要影响。     

气候变暖下东北地区春玉米生产潜力变化分析

在气候变暖的背景下,依据中国东北地区101个气象站点多年逐日气象数据,利用数理统计分析方法,研究了东北地区1971~2007年春玉米生长季气候变化趋势,包括春玉米生长季平均气温、太阳辐射总量和降水量的变化趋势;利用GIS技术分析了东北地区春玉米光温生产潜力及气候生产潜力的时空变化。结果表明,东北地区春玉米生长季气温呈波动上升趋势,其幅度超过全国平均值,太阳辐射呈减少趋势,降水量年际变化较大,有波动下降趋势。在气温不断升高的情形下,东北地区春玉米的光温生产潜力有所增加,但由于各地区间降水的差异,东北地区春玉米的气候生产潜力在各地区变化差异较大,21世纪以来相对于20世纪70年代,南部地区气候生产潜力减少,而中部地区增加。为此,就如何利用东北地区春玉米生产潜力的特点,以及提高春玉米的实际产量提出了一系列建议措施。     

中国区域陆地生态系统土壤呼吸碳排放及其空间格局——基于通量观测的地学统计评估

土壤呼吸是陆地生态系统通过根系呼吸和微生物呼吸向大气中释放CO2的过程。研究土壤呼吸的时空格局,将有助于构建区域尺度土壤呼吸定量评价模型,也可提高预测未来气候变化情境下的典型生态系统、区域以及全球尺度碳平衡状况的能力。本文整合了中国区域土壤呼吸的主要研究成果,分析了温度敏感性（Q10）和土壤呼吸（Rs）的统计特征和区域差异,定量评价了中国区域Rs的时空格局及其在中国和全球碳平衡中的作用。通过以上分析本文得出以下主要结论：①不同生态系统类型的土壤呼吸的Q10表现为森林〉农田〉草地,气候越寒冷,土壤呼吸Q10越大,并且中国区域的Q10值相对于其他国家偏低;②Rs具有明显的季节变异,不同生态系统类型的Rs表现为森林〉农田〉草地,并且,中国区域Rs低于全球Rs;③月尺度上Rs随着经纬度发生明显的季节变异,随着经度的增加,Rs的季节变幅也逐渐增加;④1995-2004年中国区域Rs的年总量的平均值为3.84 PgC,占全球土壤CO2排放的比例4.78%。     

关中-天水经济区土地利用变化模拟预测及景观格局动态变化

利用2000年和2010年两期TM影像,应用遥感和GIS技术获取关中-天水经济区2000-2010年土地利用变化数据,对研究区土地利用时空状态进行分析,并借助CA-Markov模型对该地区土地利用变化趋势进行情景模拟,深入分析了10 a来和2020年研究区土地利用变化的数量和空间特征以及由此所引起的一系列生态环境效应,主要表现在：过去10 a来城镇建设用地面积增加迅速,耕地和草地面积则减少,城镇建设用地的扩展是通过占用大量城郊的农田来实现的,通过这10 a间的快速城市化进程看出,研究区的城市扩张和基本农田保护之间已经开始产生矛盾;研究区土地利用实际变迁面积约占全区总面积的24.39%,也就是说全区约1/4的土地在这10 a间都发生了变化,从而反映出人类活动之强烈;未来10 a耕地和草地面积将持续下降,耕地面积的减少速度变快,城镇建设用地面积仍然迅速增加,且主要有耕地和草地转化而来,未来10 a研究区土地利用实际变迁面积约占全区总面积的11.43%。景观指数的分析结果表明了研究区内的景观趋向破碎化、复杂化和均匀化发展,景观的稳定性和抗干扰性减小。     

Impacts of climate change and LULC change on runoff in the Jinsha River Basin

The climate change and Land Use/Land Cover(LULC) change both have an important impact on the rainfall-runoff processes. How to quantitatively distinguish and predict the impacts of the above two factors has been a hot spot and frontier issue in the field of hydrology and water resources. In this research, the SWAT(Soil and Water Assessment Tool) model was established for the Jinsha River Basin, and the method of scenarios simulation was used to study the runoff response to climate change and LULC change. Furthermore, the climate variables exported from 7 typical General Circulation Models(GCMs) under RCP4.5 and RCP8.5 emission scenarios were bias corrected and input into the SWAT model to predict runoff in 2017–2050. Results showed that:(1) During the past 57 years, the annual average precipitation and temperature in the Jinsha River Basin both increased significantly while the rising trend of runoff was far from obvious.(2) Compared with the significant increase of temperature in the Jinsha River Basin, the LULC change was very small.(3) During the historical period, the LULC change had little effect on the hydrological processes in the basin, and climate change was one of the main factors affecting runoff.(4) In the context of global climate change, the precipitation, temperature and runoff in the Jinsha River Basin will rise in 2017–2050 compared with the historical period. This study provides significant references to the planning and management of large-scale hydroelectric bases at the source of the Yangtze River.     

Possible change on the runoff in the upper Yellow River basin under global climate change

In this study,the characteristics and changing trends of temperature,precipitation,and runoff in the upper Yellow River basin up Tangnag station are analyzed by using hydrological and meteorological data in the past 50 years from observation stations in the basin.Further,in this study,the evolving trend of runoff in the future decades is forecasted in the basin based on the method of suppositional climate scenes combination.The results indicate temperature variation in the basin has an evident positive relation with global warming,and the precipitation variations are quite complicated in the basin because of differences of located geographic positions during the past 50 years.Runoff in the basin has been decreasing continually since the end of the 1980s because the mean temperature in the basin has been rising and precipitation in the main areas of runoff formation in the basin has been decreasing.Runoff will largely decrease if precipitation decreases and temperature rises continuously,whereas runoff will increase if temperature is invariable and precipitation increases largely;the increase magnitude of runoff may be more than that of precipitation because of the synchronously increasing supply of meltwater from snow,glacier,and frozen soils in future several decades.     

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.     

Vegetation change and fragmentation in the mega city of Delhi: Mapping 25 years of change

Delhi, the worlds' second most populous city, has experienced rapid, planned and unplanned expansion at the cost of its green cover in recent decades. In this study, we use satellite images from 1986, 1999 and 2010 to map changes in urban and green cover, assess the fragmentation of green spaces, and identify the drivers of change. We find that urban patterns of development have shaped the distribution and fragmentation of green spaces, with the city center containing more green spaces with less fragmentation compared to intermediate areas and the peri-urban periphery. Yet, the city core has also experienced the greatest degree of vegetation clearing and fragmentation over time due to infrastructural expansion, while the peri-urban periphery has shown an increase in vegetation and a decrease in fragmentation due to recent compensatory plantation in these peripheral areas. Forests, archaeological sites, and military and academic campuses have played a major role in protecting green cover and limiting fragmentation in the core and intermediate areas of the city. This research helps in advancing our understanding of the pattern–process relationship between urbanization and land cover change/fragmentation in India's largest city.     

Imaging vulnerability: the iconography of climate change

This paper explores the iconography of climate change in contemporary climate action campaigns in the UK. I aim to show how sample images are simultaneously scientific denotations of global warming and cultural connotations of danger and vulnerability. I further demonstrate that while similar images are associated with different agendas and geographical visions, they attach to a shared discourse of vulnerability that has Western (colonial) roots. The paper concludes with an overview of possible ways for climate action campaigns to effectively convey their political messages without recycling colonial visions of the world.     

Ethics of large-scale change

Geografisk Tidsskrift, Danish Journal of Geography 106(2): 131–144, 2006

The subject of this paper is long-term large-scale changes in human society. Some very significant examples of large-scale change are presented: human population growth, human appropriation of land and primary production, the human use of fossil fuels, and climate change. The question is posed, which kind of attitude is appropriate when dealing with large-scale changes like these from an ethical point of view. Three kinds of approaches are discussed: Aldo Leopold's mountain thinking, the neoclassical economists' approach, and finally the so-called Concentric Circle Theories approach. It is argued that the last of these three approaches must be preferred, even though further interpretation will be needed in relation to specific decision-making.