Do indicators of nitrogen retention and leaching differ between coniferous and broadleaved forests in Denmark?

The area of broadleaved forests is projected to increase in Denmark as well as in the rest of Europe. However, studies of the N leaching response to elevated N deposition have focused on coniferous stands and considerable uncertainty still remains on whether broadleaved and coniferous forests respond differently to elevated N. We studied N input–output relations for eight stands intensively monitored during 2002–2005 and literature data for 37 additional stands which together formed a comprehensive dataset on Danish forests including 26 broadleaved stands and 19 coniferous stands. Nitrate leaching was significantly higher in first generation stands on former arable land with mineral soil C/N ratios 10–15, but both low and high rates were observed independent of the N input. A net N loss was observed in some of these stands even though they are in the aggrading phase and accumulate N in the biomass. Broadleaved stands had significantly lower throughfall N deposition than coniferous stands and this seems to be the main process where forest type exerts an influence on the N cycle. Lower soil C/N ratios offset the effect of throughfall N deposition and thus N leaching did not differ between the two forest types. The best regression models for prediction of nitrate leaching included throughfall N deposition and C/N ratio, but only a minor part of the variability was explained. The C/N ratio of the upper mineral soil was more generally applicable than that of the organic layer. The N retention of the soil was reasonably well predicted above a C/N ratio of 25, but below this threshold the importance is not known. We suggest focusing future efforts on quantifying the relative retention functions (sink strength) of the vegetation and the soil organic matter to improve the predictions of N retention and N leaching.     

Identifying cost-effective indicators to assess the conservation status of forested habitats in Natura 2000 sites

The Natura 2000 (N2000) network represents one of the most important actions for biodiversity conservation in Europe; its main aim is to assure the favourable conservation status of Europe's natural habitats and wild species. Monitoring of N2000 sites is required under the Habitats Directive, and Member States are required to report monitoring results to the European Commission. However, there is a widespread lack of understanding about precisely what should be monitored and which methods should be used. This research aimed to identify potential indicators and evaluate their suitability for evaluating the conservation status of forested habitats in N2000 sites. In addition, the cost-effectiveness of monitoring methods was assessed. Three monitoring methods were assessed in two N2000 sites, the Foresta del Cansiglio (IT) and the New Forest (UK): (i) sample plots, (ii) a point-transect method and (iii) a visual assessment method. Indicators were selected on the basis of a literature review, and related to forest structure and composition, dead wood volume, tree regeneration and ground flora composition. Results suggested that mean values of indicators did not differ between the plot and the point-transect-based methods (P > 0.05; paired t-test and Wilcoxon signed rank test). However, the survey method employed influenced the extent of variation within the indicators (as indicated by Z scores), a measure of their sensitivity. Correlations between indicators differed between the two sites. Of the three methods considered, the point-transect method was the most efficient in terms of set-up and total time required, but required the longest time per indicator and surveyed the smallest area (P < 0.001, Kruskal–Wallis test). The visual assessment method assessed the largest forest area; however, total scores of the reference values obtained from the plot-based and point-transect methods were poorly correlated with those obtained from this subjective approach. The contrasting results obtained between different methods and between different sites suggest that a general approach to monitoring N2000 sites may be difficult to develop; rather, a framework that can be adapted to the specific needs and characteristics of individual sites may be required.     

毕节地区新一轮土地利用规划数据转换与指标分解方法探索

掌握＂规划基数＂分类体系与土地现状分类（二调）分类体系对应关系,按分类释义和转换对应关系,对毕节地区土地现状分类（二调）进行转换,运用信息系统管理学原理、采用＂自上而下＂与＂自下而上＂相结合的方法,对规划年各类用地各项指标按比例法、权重法和综合分析法进行分解。     

繁奶康对奶牛泌乳早期泌乳性能及血液指标的影响

选择20头荷斯坦高产牛,采用配对分组设计分为对照组和试验组,每组各10头。对照组使用原日粮,试验组产前21d每天在日粮中添加繁奶康125g,于分娩当天添加量增至300g直到试验结束,以探讨日粮添加繁奶康对奶牛泌乳早期产奶性能(产奶量及乳品质)的影响。结果表明,补充繁奶康,产奶量、乳脂校正乳产量试验组明显高于对照组(P0.05);奶牛采食量、乳脂率、乳蛋白率、乳糖率及乳干物质含量两组间差异不显著(P0.05)。血液指标谷草转氨酶、谷丙转氨酶活性两组间无显著差异(P0.05),高产奶牛补充繁奶康对泌乳早期产奶性能有较好的改善作用。     

可持续农业评价研究进展

简析了国内外可持续农业评价指标体系和方法的研究现状以及存在问题,并指出未来可持续农业评价研究应强化与完善可持续农业的动态监测和尺度效应研究、评价主体多元化以及评价模型研究等方面     

农业水资源可持续利用评价指标体系构建及其应用

指标体系（Indicators System,IS）评价法已在各研究领域得以广泛应用,但存在IS的通用性与区域适用性、全面性与可操作性难于兼顾等问题.以东北三省2001年农业水资源可持续利用（Sustainable Utilization of Agricultural Water Resources,SUAWR）评价为例,依据研究区水资源利用状况分析选取指标保证了指标的区域适用性;采用频度统计法、专家咨询法、谱系聚类法之分裂法、理论分析法等多种方法相结合构建IS,充分借鉴、吸收了已有指标研究成果、IS构建思想及同行专家意见,保证了所选指标的通用性.体现动静结合的运行层和框架层耦合的IS结构则解决了农业水资源系统可持续内涵评价的科学性和全面性与IS的可操作性难于兼顾的矛盾.评价结果表明,按本研究构建的IS适合东北区SUAWR现状评价.     

农业可持续性评价指标体系的现状分析与构建

 在分析农业可持续性评价指标体系研究现状的基础上，对国内外研究的不同特点进行了比较。指出国内的研究方法与国际不接轨，尚缺乏严谨的科学方法。总结分析了已有的指标体系在指标的选择、计算等方面的经验教训和对生产实践的启示。最后提出了一种新形势下的农业可持续性评价指标体系以及相应的计算和评价方法。考虑到以人为本的发展观，在其中设计了农民发展指数指标；为了反映指标数值变化对可持续性影响的不同重要程度，提出了动态权重的计算方法；同时对指标的综合方法也进行了探讨。     

基于主成分分析法的茶叶特征性指标分类

在对常见茶叶进行调查统计的基础上,运用主成分分析的方法,对样本的特征性指标进行分类分析。分析结果表明,茶叶的特征性指标主要由钾、钙、磷、蛋白质组成;钾与钙为同一类指标,磷为一类指标,蛋白质也是一类指标。该特征性指标分类基本合理,对茶叶的质量控制及其质量检验部门的初步检测等都具有一定的指导作用,可减少检测步骤、提高检测效率、节约检测成本,为选用步骤少、效率高、低成本的检测对象来反映茶叶质量提供了理论依据。     

Water scarcity: Fact or fiction?

It is surprisingly difficult to determine whether water is truly scarce in the physical sense at a global scale (a supply problem) or whether it is available but should be used better (a demand problem). The paper reviews water scarcity indicators and global assessments based on these indicators. The most widely used indicator, the Falkenmark indicator, is popular because it is easy to apply and understand but it does not help to explain the true nature of water scarcity. The more complex indicators are not widely applied because data are lacking to apply them and the definitions are not intuitive. Water is definitely physically scarce in densely populated arid areas, Central and West Asia, and North Africa, with projected availabilities of less than 1000 m³/capita/year. This scarcity relates to water for food production, however, and not to water for domestic purposes that are minute at this scale. In most of the rest of the world water scarcity at a national scale has as much to do with the development of the demand as the availability of the supply. Accounting for water for environmental requirements shows that abstraction of water for domestic, food and industrial uses already have a major impact on ecosystems in many parts of the world, even those not considered “water scarce”. Water will be a major constraint for agriculture in coming decades and particularly in Asia and Africa this will require major institutional adjustments. A “soft path” to address water scarcity, focusing on increasing overall water productivity, is recommended.     

紫花苜蓿品种的TWINSPAN分类与筛选

应用"康乃尔生态学"程序(Cornell ecological program,CEP)中的二歧指示种分析TWINSPAN(Two-Way Indica-tors Species Analysis)数量分析方法,以不同紫花苜蓿品种的生理生态特性值和牧草产量值为指标,对24个紫花苜蓿品种进行分类。结果表明:用TWINSPAN可将24个苜蓿品种划分为8类,并且根据试验站所在地区的干旱半干旱的气候特征,筛选出高产、高水分利用效率、高光能利用效率的4个优良品种—超级阿波罗、胜利者、WL232、中苜1号。