坝上地区土地利用与覆被变化对土壤养分的影响

坝上地区是典型的农牧交错带 ,生态环境十分脆弱。研究表明 ,解放后 ,该区土地利用与土地覆被状况经历了多次反复的变动。 2 0世纪 80年代以前 ,草地大规模改变为旱地 ,部分改为林地 ;90年代初 ,旱地又逐步被改为草地、林地和水田使用。土地利用与土地覆被的变化引起土壤中有机质、全N、全P、全K、碱解N以及有效态P、K、B、Mo、Mn、Zn、Cu和Fe等养分呈有规律的改变。当土地由草地变为林地、旱地变为林地、旱地变为水田时 ,总体养分增多。但也有例外 ,尤其是碱解N、速效P和速效K以及微量元素 ,有时出现与上述规律不一致的情况。     

Soil Quality Evolution After Land Use Change From Paddy Soil to Vegetable Land

A survey was done in 15 typical villages, 150 soil and 86 vegetable plant samples were taken in Jiaxin prefecture of the Taihu Lake region, northern Zhejian province. Results indicate that after 15–20 years land use changed from the paddy rice–wheat (or oilseed rape) double cropping system, to a continuous vegetable land has caused soil quality dramatic change. (1) Acidification: average soil pH was 5.4; about 61% of total samples were pH < 5.5. It was 0.9 units lower than 10 years ago with same upland vegetable cultivation and was 1.2 units lower than soil pH of paddy rice–wheat (or oilseed rape) rotation. (2) Fertilizer salt accumulation: the average salt content was 0.28%, among these about 36.2% of the total samples contained more than 0.3%. (3) Nitrate N and available phosphorus (P) over accumulation: on average it was 279 mg NO₃-N/kg, and 45–115 mg P/kg. Nitrate N four times higher and available P 4–10 times more than it is in present paddy rice–wheat rotation soils respectively. This has caused wide concern because of possible groundwater and well drinking water pollution by leached nitrate N and the P losses to water by runoff from vegetable lands induce surface water eutrophication.     

失地农民土地权益流失的经济学分析

城市扩张速度的加快带来越来越多的农民丧失土地,从而引发的农民土地权益流失．这与我国“一切与农业为本,一切为农民着想”的扶农政策想违背,为解决这一问题,笔者从经济学角度探讨失地农民土地权益流失的原因,图1,参5．     

甘肃省耕地资源转变为建设用地的价值损失评估

依据耕地资源具有的社会保障功能、生态系统服务功能和经济产出功能,初步建立耕地资源的价值评估体系,综合运用市场价值法、替代法、机会成本法和影子价格法等评价方法,估算了甘肃省12个市(州)2007年耕地转变为建设用地所导致的正面效应价值损失。结果表明,由于建设用地占用耕地造成的价值损失相当巨大,2007年全省建设所占用耕地的总面积为1 564.66 hm2,造成的价值损失多达95 904.09万元,各市(州)1 hm2土地的损失都超过了45万元。从价值损失的构成来看,损失的直接使用价值为45 712.77万元,间接使用价值达50 191.32万元。可以看出,耕地资源除为社会提供直接产品价值外,还有巨大的间接使用价值,而且这种价值对人类的贡献比农产品的产出价值更为显著。     

土地资源可持续利用的生态经济系统分析

论述了土地生态经济系统的特点和实现土地可持续利用的生态经济条件。土地生态经济系统是土地生态系统与土地经济系统耦合而成的复合系统 ,土地可持续利用与生态经济平衡存在着内在联系 ,生态经济平衡是实现土地可持续利用的前提条件 ;土地可持续利用目标是在土地开发利用过程中 ,实现生态、经济和社会三效益的协调统一 ;遵循生态经济规律是实现土地资源可持续利用的必要条件     

土地整理与农村生态环境

在对土地整理的产生与内涵进行简要介绍的基础上 ,阐述了土地整理的生态环境效益 ,提出了土地整理中应注意的几个生态环境建设问题     

生态型城市用地布局的优化

城市生态环境已经成为影响城市发展的重要因子。当今城市空间拓展与结构转型步伐加快，但由于经济的快速增长和城市的蔓延扩展，城市生态变得异常脆弱，人地矛盾、经济发展和环境保护的矛盾相当突出。经济发达城市无锡市的生态环境问题相当突出，借鉴国外先进经验，研究自身的特点，无锡生态城市建设必须强化城市生态规划的作用，优化城市用地布局，发挥其丰富的河流、道路和湖边山体的绿色优势，营造网络型开敞式的生态空间，环境与经济才能协调发展。     

Effects of Land Use on Threatened Species

Abstract:  There is widespread agreement that biodiversity loss must be reduced, yet to alleviate threats to plant and animal species, the forces driving these losses need to be better understood. We searched for explanatory variables for threatened-species data at the country level through land-use information instead of previously used socioeconomic and demographic variables. To explain the number of threatened species in one country, we used information on land-use patterns in all neighboring countries and on the extent of the country's sea border. We carried out multiple regressions of the numbers of threatened species as a function of land-use patterns, and we tested various specifications of this function, including spatial autocorrelation. Most cross-border land-use patterns had a significant influence on the number of threatened species, and land-use patterns explained the number of threatened species better than less proximate socioeconomic variables. More specifically, our overall results showed a highly adverse influence of plantations and permanent cropland, a weaker negative influence of permanent pasture, and, for the most part, a beneficial influence of nonarable lands and natural forest. Surprisingly, built-up land also showed a conserving influence on threatened species. The adverse influences extended to distances between about 250 km (plants) and 2000 km (birds and mammals) away from where the species threat was recorded, depending on the species. Our results highlight that legislation affecting biodiversity should look beyond national boundaries.     

Enhancement of Farmland Biodiversity within Set-Aside Land

Abstract:  The efficacy of agricultural set-aside policies for protecting farmland biodiversity is widely debated. Based on a meta-analysis of 127 published studies, we found that land withdrawn from conventional production unequivocally enhances biodiversity in North America and Europe. The number of species of birds, insects, spiders, and plants is 1–1.5 standard deviation units higher on set-aside land, and population densities increase by 0.5–1 standard deviation units. Set-aside land may be especially beneficial for desirable taxa because North American bird species that have exhibited population declines react most positively to set-aside agricultural land. Larger and older plots protect more species and higher densities, and set-aside land is more effective in countries with less-intensive agricultural practices and higher fractions of land removed from production. Although policies specifically designed to protect biodiversity might work even better, current incentives clearly improve the standing of plants and animals in farmland.     

生态用地分类初步研究

中国现有的土地利用分类体系对土地的生态属性考虑不足,导致生态用地分类缺乏统一的标准,生态用地难以得到有效保护。基于此,该文尝试对生态用地分类体系进行初步研究,以期为生态用地的科学管护,国土空间格局的优化和生态文明建设的推进提供科技支撑。在总结借鉴国内外学者有关生态用地研究成果的基础上,首先对生态用地概念进行了界定,在剔除《第二次全国土地调查技术规程-土地利用现状分类》中的非生态用地基础上,采用“逆向递推”方法将生态用地合并归类：根据生态用地的概念、内涵和划分依据,将剔除非生态用地后的土地利用现状分类中的二级地类归为35个生态用地三级地类;根据人类活动对生态用地影响范围和程度的不同而导致发挥的生态功能强弱的差异,将生态用地三级地类合并归类为14个二级地类;基于“人类活动-生态用地”影响反馈机理,将生态用地分为原生生态用地、半人工生态用地和人工生态用地3个一级地类。随后,为使生态用地分类系统在生态用地管理与生态建设实践中发挥应有的作用,将土地利用现状分类与生态用地分类实现了有效衔接。最后,作者建议借鉴国内外对于生态系统服务功能的相关研究,考虑从生态系统服务价值等视角来建立相关定量化的系统科学的生态用地分类体系。     

城市交通用地的研究

首先介绍了当前城市交通规划与土地规划之间所存在的一些不协调之处，然后研究了城市交通规划与土地利用之间的关系，进而提出了城市交通与土地利用之间的相互促进模式，最后，根据一些假设条件建立了城市最佳交通用地量的概念模型，从而为制定科学而合理的交通规划与土地规划提供了一种参考。     

中国土地退化的分类与分级

在参照国际上土地退化评价指标体系的基础上,结合中国实际,从代表性、普遍性和可操作性原则出发,提出了中国土地退化的初步分类与分级标准。中国土地退化可划分为风蚀作用下的土地退化、水蚀作用下的土地退化、物理退化和化学退化4类,土地退化程度分为轻度、中度、强度和极强度退化4级,并拟定4类土地退化的评价标准。