喀斯特地区土地利用变化与可持续利用研究——以贵州省贵阳市为例

以贵阳市为研究区域,在分析土地利用变化的基础上,从资源保护性、生态合理性、经济可行性、社会接受性等方面构建土地可持续利用指标体系.通过土地可持续利用综合评价模型和土地可持续利用障碍因素诊断模型,评价贵阳市土地可持续利用水平,分析其土地可持续利用的障碍因素,并提出相应的对策.     

Patterns and processes of pasture to crop conversion in Brazil: Evidence from Mato Grosso State

The rate and location of cropland expansion onto cattle pastures in Brazil could affect global food security, climate change, and economic growth. We combined mapping, statistical modeling, and qualitative methods to investigate patterns and processes of pasture to crop conversion (P2C) in Mato Grosso State (MT), Brazil, a globally important center of agricultural production. P2C land constituted 49% of cropland expansion from 2000 to 2013. For a random sample of ̃250 m pixels in MT, we estimated a regression model skilled at predicting P2C land in the rest of the state as a function of cattle ranching suitability, cropping suitability, and P2C conversion costs. Surprisingly, just 1/7 of pasture agronomically suitable for cultivation had undergone P2C. Hedonic regressions revealed that agronomic characteristics of land were associated with less than 20% of the variation in cropland suitability. Instead, the majority of the variation stemmed from a combination of proximity to agricultural infrastructure, characteristics of neighboring lands, and time fixed effects. The weak relationship between agronomic characteristics of land and P2C location suggests a less certain future for P2C than projections made with agronomic models. Consequentially, complications may arise for greenhouse gas mitigation policies in Brazil predicated on widespread expansion of cropland on pasture vs. natural areas. Our follow-up qualitative research shows that because P2C has often involved land rentals or sales, poorly functioning land institutions may have constrained P2C. Locally poor land quality, omitted from agronomic P2C predictions, can either catalyze or constrain P2C by limiting returns to ranching, farming, or both. Interventions to control rates and locations of P2C should take these insights into account.     

浅析低碳型土地利用规划

世界多个城市政府以及诸多国际组织都在积极推进低碳城市的建设,本文主要从土地利用规划的角度提出如何应对气候变化,发展低碳经济。建议通过科学的计算方法制定各地区不同的碳排放指标,将碳排放量严格控制在各指标范围之内,并从土地利用战略研究、土地利用结构调整、土地利用布局优化及环境影响评价等方面,提出将碳排放量放入规划体系之中,实现碳减排与土地利用规划的一体化,进而达到节约资源能源、绿色可持续发展的目的。     

大连金石滩土地利用时空分异研究

以1992、1998、2004、2009年的金石滩地区土地利用数据为基础,运用GIS软件的叠置分析,空间分析对研究区土地变化时空分异研究。本文通过单一土地利用动态度和综合土地动态度分析研究区内图地类型变化的速度和趋势,同时将土地利用扩展强度指数带入分析土地利用规模的变化,以此探究其土地利用变化的驱动因素。研究表明,土地利用数量变化模式呈现耕地面积大量减少,建设用地迅速增加:1992-2013年各土地利用类型单一动态度中耕地和未利用地减少速度相对较快,分别为-4.36%和-4.37%;城乡建设用地增加最快,为21.37%,其次为交通水利用地,为17.99%;1998-2004年综合土地利用动态度最大,为3.63%,这期间土地利用变化最为迅速,旅游开发活动剧烈。扩展强度指数计算各土地类型得出,耕地的扩展强度指数最低,为-1.48,城乡建设用地的扩展强度指数最高,为1.42%。研究结果可信。     

Land system change in Italy from 1884 to 2007: Analysing the North–South divergence on the basis of an integrated indicator framework

Over the past centuries, land systems in Italy experienced fundamental shifts, owing to the availability of new energy forms, population surges, and technological progress. The 20th century was characterized by massive productivity increases, accompanied by gradual land abandonment and the return of forest land. We here analyze 120 years of land system change in Italy, applying the human appropriation of net primary production (HANPP) framework, a metric for socio-economic pressures on terrestrial ecosystems. HANPP allows integrating ecological with societal perspectives, by systematically quantifying (a) biomass harvest and (b) the difference between potential productivity of ecosystems and current productivity induced by land use processes, such as land conversion, or land degradation. Besides assessing national trends we calculated HANPP separately for the Italian North and South between 1934 and 2007, in order to scrutinize if high regional discrepancies in terms of natural and socio-economic preconditions translate into diverging land system trajectories. Our results show that national HANPP has been declining from 78% of natural productivity before WWII to 56% in 2007, indicating a declining land -use induced pressure on biomass flows over time. Simultaneously, biomass harvest increased by around 26% due to agricultural intensification, despite shrinking croplands. Although we found a significant difference between the Northern and Southern region in the absolute levels of several land use indicators related to biomass appropriation, the overarching trends of land system change were remarkably similar in both regions. This suggests that underlying drivers of land system change, such as policies aimed at land-use intensification and structural change were equally dominating land system trajectories in the North and South of Italy, not withstanding their socio-ecological divergences.     

基于能值分析的沈阳市耕地利用可持续集约化时空分异特征研究

研究目的：测度2000—2019年沈阳市耕地利用可持续集约化水平的时空格局,为理解耕地利用可持续集约化的过程规律及响应机制,优化沈阳市耕地利用模式提供参考。研究方法：能值分析法。研究结果：（1）2000—2019年沈阳市耕地生态经济系统能值投入减少17.53%,能值输出增加89.19%。（2）2000—2019年,沈阳市耕地生态经济系统能值生产率（EPR）和能值产出率（EYR）分别增加129.40%、140.76%,各行政区均呈现波动上升的趋势,南高北低的空间差异逐渐缩小;环境负载率（ELR）呈“M”型波动增长,总体增加48.69%,北高南低的空间差异逐渐缩小;环境经济效率（EE）呈“W”型变化,总体下降15.38%,南高北低的空间格局没有发生明显变化。研究结论：2000—2019年,沈阳市耕地利用可持续集约化水平得到提高,自西北向东南先下降后上升的空间格局没有发生明显变化,应重点关注水稻种植对耕地利用可持续集约化的影响,合理调适社会经济系统的能值投入,促进耕地生态经济系统的科学利用和保护。     

Cultivated land conversion and potential agricultural productivity in China

In China there is a growing debate on the role of cultivated land conversion on food security. This paper uses satellite images to examine the changes of the area of cultivated land and its potential agricultural productivity in China. We find that between 1986 and 2000 China recorded a net increase of cultivated land (+1.9%), which almost offset the decrease in average potential productivity, or bioproductivity (−2.2%). Therefore, we conclude that conversion of cultivated land has not hurt China's national food security. We also argue that more recent change in cultivated area likely has had little adverse effect on food security.     

Can soil-less crop production be a sustainable option for soil conservation and future agriculture?

Agriculture faces huge challenges regarding sustainable use of soils and its sustainability performance in general. There are three different approaches to sustainable agricultural production commonly proposed, namely intensification, agro-ecological approaches and high-tech industrial approaches. Often, some propose that only agro-ecological approaches are truly sustainable options, with particular benefits for soil protection, while others argue that intensification or high-tech performs better through land sparing. In this viewpoint, we scrutinize the notion of “sustainable agricultural production” and the role these approaches may play for such, in particular addressing the controversy of “naturalness” versus “artificiality” in production systems. Consumers often perceive agriculture as “natural”, but agriculture today thrives always on strong human intervention. We posit that agriculture is linked to soils and natural processes, but that this provides little guidance on what sustainable agriculture should be. Being “natural” need not be an aspect of being sustainable. If it is, arguments for this need to be provided. Furthermore, revealed consumer preferences may much less frequently posit being “natural” as a central criterion for food consumed than usually assumed. By all this, we do not want to promote any of those three approaches uncritically. We rather argue for enlarging the option space for sustainable agriculture in an unprejudiced way.     

Sustainable crop intensification through surface water irrigation in Bangladesh? A geospatial assessment of landscape-scale production potential

Changing dietary preferences and population growth in South Asia have resulted in increasing demand for wheat and maize, along side high and sustained demand for rice. In the highly productive northwestern Indo-Gangetic Plains of South Asia, farmers utilize groundwater irrigation to assure that at least two of these crops are sequenced on the same field within the same year. Such double cropping has had a significant and positive influence on regional agricultural productivity. But in the risk-prone and food insecure lower Eastern Indo-Gangetic Plains (EIGP), cropping is less intensive. During the dryer winter months, arable land is frequently fallowed or devoted to lower yielding rainfed legumes. Seeing opportunity to boost cereals production, particularly for rice, donors and land use policy makers have consequently reprioritized agricultural development investments in this impoverished region. Tapping groundwater for irrigation and intensified double cropping, however, is unlikely to be economically viable or environmentally sound in the EIGP. Constraints include saline shallow water tables and the prohibitively high installation and energetic extraction costs from deeper freshwater aquifers. The network of largely underutilized rivers and natural canals in the EIGP could conversely be tapped to provide less energetically and economically costly surface water irrigation (SWI). This approach is now championed by the Government of Bangladesh, which has requested USD 500 million from donors to implement land and water use policies to facilitate SWI and double cropping. Precise geospatial assessment of where freshwater flows are most prominent, or where viable fallow or low production intensity cropland is most common, however remains lacking. In response, we used remotely sensed data to identify agricultural land, detect the temporal availability of freshwater in rivers and canals, and assess crop production intensity over a three-year study period in a 33,750 km² case study area in southwestern Bangladesh. We combined these data with georeferenced and temporally explicitly soil and water salinity information, in addition to relative elevation classifications, in order to examine the extent of winter fallows and low productivity rainfed cropland that could be irrigated by small-scale surface water pumps. Applying observations of irrigated crop sowing dates and yields from 510 wheat, 550 maize, and 553 rice farmers, we also modeled crop intensification production scenarios within the case study area. We conservatively estimate that at least 20,800 and 103,000 ha of fallow and rainfed cropland, respectively, could be brought into intensified double cropping using SWI. Scenario analysis indicates that if 25%–75% of the fallow or low-intensity land were converted to irrigated maize, national aggregate production could increase by 10–14% or 29–42%, respectively. Conversion to wheat would conversely boost national production by 9–10% or 26–31%. Irrigated rice is however unlikely to contribute >3%. In aggregate, these actions could generate between USD 36–108 million of revenue annually among farmers. Intensification therefore has important land use policy and food and income security implications, helping to rationalizei SWI investments. Crop choice, water resource allocation, and water governance will however remain crucial considerations for irrigation planners.     

违法用地对土地可持续集约利用的影响机制及效应研究

研究目的:研究土地违法对土地可持续集约利用的影响机制及效应。研究方法:基于2006—2015年中国省级面板数据,建立土地违法对土地可持续集约利用影响的理论分析框架,并进行实证检验和区域差异分析。研究结果:(1)违法用地对土地可持续集约利用具有正向影响,并且这种影响效应在东部地区最为显著;(2)引入土地市场化因素后,东部地区和中部地区违法用地对土地可持续集约利用的负向影响加剧,且中部地区高于东部地区,而西部地区的影响作用相反,加入土地市场化因素后违法用地对土地可持续集约利用的影响显著为正;(3)违法用地对土地可持续集约利用的影响在空间上具有溢出效应。研究结论:中国需进一步深化土地市场化改革,建立土地出让全过程的监督管理体系,抑制违法用地;创新土地出让方式,提高土地周转效率;实施分区域差异化管理的对策建议。     

中国蔬菜生产“以水定地”优化布局研究

[目的]文章以中国蔬菜产业布局为研究对象,通过分析蔬菜生产重心演变路径、蔬菜布局地域集中度以及蔬菜生产空间布局与水资源禀赋的拟合度,为优化我国蔬菜生产空间布局、促进农业节水、保障农业用水安全提供参考依据。[方法]采用1995—2018年我国蔬菜产业的相关数据,运用重心模型、集中度指数等方法,对蔬菜生产的区位特征进行研究,并构建蔬菜生产空间布局与水资源禀赋拟合度指标,对蔬菜生产空间布局与水资源禀赋拟合度进行分析。[结果]我国蔬菜生产重心呈现出整体上向西南方向移动的新趋势,蔬菜生产的地域集中度已经达到较高水平,但蔬菜空间布局与水资源禀赋的匹配度不高,导致蔬菜生产过度依赖人工灌溉,消耗甚至是浪费了大量的水资源。[结论]遵循“以水定地”原则,提出蔬菜产业空间布局与水资源禀赋条件优化匹配的政策建议：推进大宗蔬菜生产重心“西南移”,充分利用南方水资源优势,节约北方水资源;推进耐储运蔬菜的“南菜北运”,解决北方消费市场的蔬菜供给问题;推进北方蔬菜生产“转型升级”,转型生产精细时鲜特菜和节水型蔬菜,升级采用微灌、精灌技术,保持北方蔬菜基地经济水平。     

新型城镇化与土地集约利用的时空演变及关系

［目的］分析新型城镇化与土地集约利用的时空演变特征,在此基础上探索新型城镇化与土地集约利用的关系。［方法］基于数据可获取性及科学性等原则,选取新型城镇化与土地集约利用的指标,利用熵权TOPSIS法测算2007—2016年重庆市新型城镇化与土地集约利用的指数,并利用GIS软件制作空间分布图,引入空间计量模型分析新型城镇化与土地集约利用的空间关系。［结果］（1）在时间特征方面,重庆市新型城镇化及土地集约利用水平均呈现平稳提高趋势; 在空间特征方面,重庆市新型城镇化与土地集约利用空间变化显著。（2）新型城镇化与土地集约利用的时空变化规律较为相似,新型城镇化对土地集约利用确实存在促进作用。［结论］在重庆市土地资源需求急剧增长的前提下,加快推进新型城镇化建设,以改善土地低效利用,制定切合实际的土地利用规划、优化产业布局、促进城镇合理建设,侧向推动土地集约利用。     

京津冀地区蔬菜生产空间集聚演变分析

[目的]通过分析蔬菜生产集聚特征及空间相关性,为优化京津冀地区蔬菜生产布局、有效保障蔬菜供给提供参考。[方法]文章利用2011—2016年京津冀13个市、168个县域单元的面板数据,对区域内蔬菜生产变动进行了空间统计与计量分析,揭示京津冀地区蔬菜生产格局的时空分异特征。基于集中度指数、基尼系数分析了京津冀地区蔬菜生产的变动态势、空间集中水平;构建空间权重矩阵,利用莫兰指数和莫兰散点图对京津冀地区蔬菜生产空间相关性进行实证研究。[结果]得到了京津冀地区蔬菜生产的空间分布格局,并对蔬菜生产集中程度和空间相关性进行了检验。[结论]京津冀蔬菜生产水平存在空间负相关性,且相关性呈现减弱趋势。地理相近的市域之间在蔬菜生产上也具有相互依赖性,但依赖程度较低。县域层面上蔬菜生产已经有较高的专业化程度。建议京津冀地区深入推进蔬菜生产区域化和专业化发展。