桉树人工林生态量化评价指标体系的建立

随着桉树人工林经营水平的提高,桉树人工林不仅满足木材的需求,还发挥生态效益等其他功能。本文通过专家咨询法对桉树人工林生态目标量化评价指标进行筛选,采用层次分析法和德尔菲法确定指标的权重,最终形成5个一级指标、18个二级指标、36个三级指标的指标体系。一级指标中,碳汇权重最大,达0.2944,体现了碳汇在现今生态系统中的重要程度。第二是生物多样性,达0.2715,生物多样性是评价生态系统的核心指标。第三是生态系统健康,权重为0.2363,生态系统健康是生态系统的基础,生态系统其他功能的发挥程度取决于生态系统健康的程度。生态系统水环境和生态系统土壤环境的权重分别是0.1029和0.0949。     

NaCl与Na2CO3胁迫对光果甘草幼苗叶片叶绿体色素含量的影响

以水培光果甘草幼苗作为试验材料,分别进行不同浓度NaCl[0.2%,0.5%,0.8%(w/v)]与Na2CO3[0.01%,0.05%(w/v)]胁迫处理,以完全营养液培养作为对照,在处理第5天后测定各处理叶片中叶绿素a,叶绿素b,类胡萝卜素含量并计算叶绿素a与叶绿素b的比值。结果表明:在NaCl胁迫处理下,甘草叶片chla、chab、car含量均以0.2%NaCl为最高,之后随盐浓度升高而下降,而cha/chlb值则随盐浓度的升高而升高,在Na2CO3处理下,甘草叶片chla、chlb、car含量随Na2CO3胁迫处理浓度的升高而升高,而cha/chlb值则呈现下降的变化趋势。无论是NaCl处理还是Na2CO3处理各处理浓度间上述指标差异均达显著或极显著水平。     

干旱胁迫对不同大豆品种苗期叶片渗透调节物质含量和细胞膜透性的影响

研究了苗期大豆在干旱胁迫下叶片渗透调节能力与大豆抗旱性的关系.结果表明:随着干旱胁迫的加强,渗透调节物质中可溶性糖(WSS)、游离脯氨酸(Pro)含量累积显著增加,质膜透性也不断增大.且耐旱性强的品种可溶性糖(WSS)和游离脯氨酸(Pro)含量增加的幅度大于耐旱性弱的品种,而MDA含量和相对电导率则是耐旱性强的品种增幅小于耐旱性弱的品种.     

温度逆境锻炼对低温胁迫下番茄幼苗细胞膜脂质过氧化产物及抗氧化酶活性的影响

为了探索番茄植物交叉适应现象及其生理机制,以番茄品种东农704为材料,研究了低温和高温锻炼后番茄幼苗在2℃低温下叶片中丙二醛(MDA)和抗氧化酶活性的变化。结果显示,番茄幼苗经过适宜的低温和高温锻炼均可提高幼苗的抗冷性,并且高温锻炼在提高番茄幼苗抗冷性方面明显优于低温锻炼。2℃低温胁迫1d,未经锻炼幼苗与锻炼幼苗相比,其MDA含量明显升高,超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性大幅度下降,即使在恢复生长2d后,MDA仍维持在较高的水平,SOD、POD和CAT活性水平也较低。番茄幼苗在低温和高温锻炼后、低温胁迫后和恢复2d后,MDA含量和酶保护系统变化各有异同。上述研究结果表明番茄植物具温度逆境交叉适应性,低温和高温锻炼诱导的番茄抗寒机制存在着差异性。     

Performance Assessment in the Management of ``Canal de Provence', France

This case study presents the performanceassessment scheme of the network of canalsand pressurised pipes of the public andprivate company: ``Societé du Canal deProvence' (SCP).According to a State Concession decree,this company is due to provide apre-established level of service to itscustomers, and be financially sustainable.Its technical and maintenance services haveinstalled a network of measurements anddata collection devices and defined aspecific set of performance indicators toverify achievement of these two goals.     

牧草在高密度压捆时的应力松弛研究

牧草的应力松弛特性对牧草的压缩工艺、压缩设备以及压缩后牧草产品的质量等均有很大影响。利用高密度捆草机对其进行试验研究，后根据积分理论并借助计算机对试验结果进行分析计算，获得了有关流变参数和本构方程，这对牧草压缩理论的发展及压缩设备的开发以及提高压缩后牧草产品的质量等均有重要的指导作用。     

Are seedlings reasonable surrogates for trees? An analysis of ozone impacts on Quercus rubra

The appropriateness of using seedling responses to predict mature tree responses to ozone is questionable considering the long life span of trees. To determine if northern red oak (Quercus rubra L.) seedlings and mature trees respond similarly to ozone, 30-year-old trees and two-year-old seedlings were fumigated with subambient, ambient, and twice ambient concentrations of ozone for three growing seasons using an open-top chamber facility. Ozone reduced leaf physiological function of mature trees. However, stem diameter growth and leaf mass of mature trees were not significantly reduced by ozone. Photosynthesis in seedling leaves was slightly reduced by ozone, but seedling growth and biomass were unaffected. Mature tree fine-root biomass responded negatively to increasing ozone, while seedlings exhibited increases in biomass. Carbon retention was enhanced in leaves and branches of mature trees by ozone treatment, while seedlings were unresponsive. Differences in ozone uptake, recurrent flushing and carbon dynamics rather than microclimate may explain differences in ozone sensitivity between seedlings and mature trees. These results indicate that seedlings may not reflect the ozone sensitivity of larger more physiologically mature trees.     

Effect of air-drying treatment on enzymatic activities of soils affected by anthropogenic activities

The influence of air-drying on dehydrogenase, invertase, -glucosidase, urease, phosphatase, arylsulphatase and phenoloxidase activities was measured in three soils affected by anthropogenic activities and in control soils sampled from neighbouring areas. The air-drying changed enzyme activity, but the behaviour was neither site-specific nor enzyme-sensitive. Canonical discriminant analysis of enzymatic activities of both moist fresh and air-dried samples was able to discriminate between altered and unaltered soils irrespective of the site. Numerical alteration indices were developed as a linear function of the seven enzyme activities and the one obtained from fresh sample data was more successful. Air-drying apparently alters in unpredictable ways enzyme activities of soils, which could lead to misinterpretation of results.     

Stress relaxation of five different soil samples when uniaxially compacted at different water contents

The average size of rainfed and irrigated agricultural farms in Spain has grown steadily over the past two decades. This has called for the use of machinery of higher field capacity and greater weight that in turn requires a high drawbar power. All this has resulted in soil changes such as an increased compaction and compactibility. The confined uniaxial compression test was used to assess compaction and viscoelastic behavior of five soil samples from different agricultural areas of Spain. The bulk density–compression stress line was fitted to a three-parameter multiplicative compaction model and viscoelastic behavior was evaluated by means of stress-relaxation tests. The objectives were to determine to what extent the parameter coefficients of the compaction model equation and the relaxation of the stress induced in the compacted soil were influenced by the type of soil, its water content and the compression stress applied. Gravimetric water contents of 5, 10, 15, 20 and 25% were considered, and maximum normal stresses of 50, 100, 200 and 400 kPa were applied to the soils in a universal testing machine. The soil samples considered differed in texture, sandy loam (SL), sandy clay loam (SCL), loam (L), clay (C) and silt-loam (SiL), and organic matter content.

The slope of the bulk density-compression stress line at zero normal stress was strongly dependent on soil water content and plasticity index; whereas the slope of the curve at high applied normal stresses was influenced by soil moisture but not by soil plasticity. The viscoelastic behavior of the soils compared was dictated by their water content and plasticity index, as well as by the compression stress applied. The stress relaxation rate at time t=0 was scarcely influenced by water content. In fact, the rate remained constant over the water content range from 10 to 20% (w/w) at values that were higher than those obtained at 5 and 25% (w/w), which in turn were identical to each other. The stress-relaxation rate was also found to increase linearly with the logarithm of the compression stress. On the other hand, the residual stress decreased linearly with increasing water content. However, the latter increased linearly with compression stress. Increasing soil plasticity resulted in decreasing relaxation rate and increasing residual stress. Therefore, the more plastic the soil was the lower was the rate at which stress relaxation started and the smaller was the amount of stress dissipated.     

Complementary Hotspot Inventory - A method for identification of important areas for biodiversity at the forest stand level

Forest stands are the basic planning units of managed forest landscapes, and the structural composition of these units is important for conservation of biodiversity. We present a methodological approach for identification and mapping of important structural and environmental features of forest stands. Based on an analysis of habitats of red-listed species and a synthesis of results from research on spatial distribution of forest species, we developed a habitat inventory approach (Complementary Hotspot Inventory, CHI) that is currently used in forestry planning in Norway. The CHI maps fine-scale hotspots for 12 habitat types that are further classified according to positions along main environmental gradients (productivity and humidity). Consisting of different substrates in different environments, these habitats to a large degree support different species assemblages. By incorporating both the hotspot and the complementary approach, the CHI produces data tuned for later conservation measures. The high spatial resolution of data facilitates the use of conservation measures at different spatial scales, from single-tree retention to forest reserves. A validation test of habitats identified by CHI showed that the density of red-listed species was four times that of randomly selected old forests.