模拟降雨条件下玉米植株对降雨再分配过程的影响

为系统测定玉米(Zea mays)不同生长阶段的穿透雨、茎秆流和冠层截留,采用室内模拟降雨法测定了不同降雨强度、不同叶面积指数玉米冠下穿透雨和茎秆流,采用喷雾法测定了玉米不同生长阶段的冠层截留。对其进行了量化分析,并探讨了三者与玉米叶面积指数和降雨强度的关系,阐明了玉米冠下穿透雨的空间分布特征。结果表明:玉米冠下穿透雨量占冠上总降雨量比例为30.97%—94.02%,平均为63.92%;茎秆流量占降雨量比例的变化范围为5.68%—75.70%,平均为35.28%;冠层截留量在其全生育期内变化范围为0.02—0.43 mm,平均为0.16 mm,所占总降雨量比例最大仅为1%。随玉米生长,穿透雨量逐渐降低,茎秆流量和冠层截留量逐渐增加。穿透雨与茎秆流呈现此消彼长的关系,其中穿透雨率平均由93.55%降至36.23%;茎秆流率平均由5.98%增加至70.42%。降雨强度与穿透雨量和茎秆流量呈正相关关系,但是二者占总降雨量的比例与降雨强度关系不显著(P0.05)。随着玉米生长,穿透雨冠下空间分布由均匀逐渐趋向于不均匀,使降雨经过冠层后趋于向行中汇集,但在玉米生长后期,集中于行中的穿透雨量也因叶片衰败而随之降低。揭示了玉米对降雨的再分配作用特征,可为农田水分有效利用、农田生态水文过程机理和坡耕地土壤侵蚀防治提供理论依据。     

Estimation of the migration potential of diesel fuel constituents from soil to ground water: A case study

A methodology for estimating the migration potential of diesel fuel constituents from soil to ground water was developed for a large commercial property impacted by diesel fuel. The diesel fuel impacts are associated with former railyard practices that occurred prior to 1970. The site is being redeveloped for commercial use. The proposed improvements for the site include an asphalt‐paved parking lot over the location of the diesel fuel‐impacted soils. The methodology is based on the composition of weathered diesel fuel and the migration characteristics and toxicity data of the diesel fuel constituents. Based on these considerations, the two elements of the methodology are (1) an evaluation of the migration potential of diesel fuel constituents in soil using the soil synthetic rainwater leachate laboratory analysis; and (2) a health‐risk assessment of the diesel fuel ground water impacts. This approach provided sufficient site‐specific data to support a regulatory agency decision allowing development to continue without active remediation of the site soils. If the methodology had not been applied to the site, a remedial method based on a 100 mg/kg to 1000 mg/kg TPH underground storage tank (UST) program soil cleanup level would have likely been required. Considering the project's time constraints and financial requirements, remedial options such as offsite disposal or onsite thermal treatment would have been used resulting in cleanup costs likely exceeding $500, 000. The potential value of this methodology can be best appreciated considering that, based on EPA estimates, there are approximately 295, 000 contaminated UST sites and a significant portion of these sites are contaminated with diesel fuel. These sites could benefit considerably from this approach.     

西双版纳热带季节雨林内雾特征研究

 利用4年（1999～2002）的雾观测资料,对西双版纳热带季节雨林内雾特征进行了观测研究。结果表明,雾首先形成于最上林冠层,林下雾是由上层雾变浓、下沉而来。夜间,雾形成前,气温高于叶表温;雾形成后,气温则低于叶表温。热带雨林内各季节雾日数和雾日频率均高于无林地。热带雨林内平均全年雾日数可达258 d,其中雾季和干热季共占154 d（59.6%）,而雾季的雾日频率高达90%。雾日数的季节变化与各季节雨量呈明显的负相关。雾季,雾在23∶00左右生成,比干热季、雨季分别提前0.7、2.3 h,而消散时间则分别推迟0.8、2.2 h。雾生成和消散时间呈现出较明显的负相关。雾季雾的持续时间达12.2 h·d-1,比干热季、雨季分别长1.5、4.6 h·d-1。全年雾总持续时间占全年时间的39.7%,而雾季的相应值为50.8%。雾的形成不仅凝结了水汽进入森林（全年89.4 mm）,同时也对森林起到了一定的保温作用,这对热带雨林的生存和发展具有至关重要的作用。     

六盘山华北落叶松林和红桦林枯落物持水特征及其截持降雨过程

在六盘山南坡野外调查了华北落叶松(Larix principis-rupprechtii)和红桦(Betula albo-sinensis)两个林分的枯落物数量特征,其厚度分别是3.6cm和4.0cm,储量为16.83 t/hm2和9.04 t/hm2.浸泡测定了单位重量(1.0kg/m2)枯落物的持水能力,华北落叶松林和红桦林的最大持水深分别是1.8 mm和2.7 mm.在六盘山地区自然雨强范围内(<30 mm/h),利用模拟降雨研究了枯落物的截持降雨过程,表明枯落物持水能力随雨强增大而提高;在雨强为30 mm/h时,华北落叶松林和红桦林枯落物(1.0kg/m2)的最大截持雨量为1.5mm和2.6mm,分别是浸泡测定持水能力的83.3%和96.2%,两种实验吸持水分的过程基本一致.分析表明,枯落物截持过程的吸水速率受其本身含水量大小的影响,同时构建了具有较好截持机制的枯落物截持降雨过程模型,并基于枯落物浸泡实验和模拟降雨截持实验的数据拟合了模型参数.     

半干旱黄土高原退化生态系统的修复与生态农业发展

首先分析了半干旱黄土高原区域生态系统的特点,指出：这里地带性植被极度退化,土壤质量严重恶化,治理难度大,可持续发展受到严重威胁。然后,进行生态系统退化关键驱动力的分析,认为,在不同时期,农民的利益驱动始终是土地利用格局和生态系统演化／退化的关键驱动力。在寻求分析退化生态系统修复的突破口时,认为提高作物产量和经济效益,解决农民的需求是具有可操作性的途径。而实现这一途径必须提高单产,以减轻更广大土地面积上的生产力需求压力。通过集水、覆盖等措施改善农田水分条件,再配合地膜、化肥,在对农田进行合理管理的情况下,粮食单产可获得持续大幅度的提高。在此基础上,提出了实现区域可持续发展的途径——集水型生态农业及其景观配置模式。在这一模式中,经济作物、粮食作物、人工草地和天然草地在一个完整的景观单元内合理配置,形成完整的景观复合生态系统。对这一模式的深人研究和正确实施将推动半干旱黄土高原退化生态系统的修复,并为西部开发中经济建设和生态建设并举提供理论与实践指导。     

巴布亚新几内亚原木上截获锥象的鉴定

江苏口岸从巴布亚新几内亚原木上共截获了9属11种锥象,本文给出了这9属的检索表和11个种的区别特征及原色图。其中的Cyphagogus能取食材小蠹和长小蠹;而Cerobates、Trachelizus、Baryrrhynchus等为害习性与长小蠹相似。也对锥象的检疫方法也作了探讨。     

从泰国进口椰色果中截获南方凹头臭蚁

依据形态学特征,对截获自泰国进口椰色果上的凹头臭蚁进行种类鉴定。经鉴定,该批凹头臭蚁为南方凹头臭蚁Philidris notiala ZhouZheng,经中国检验检疫科学研究院动植物检疫信息资源共享服务平台查询,系全国口岸首次截获。南方凹头臭蚁由周善义等人于1998年描述,此前仅知分布于中国广西的北流市,本次从来自泰国的椰色果上检出,是其在泰国分布的首次报道,是泰国新记录种。通过记述南方凹头臭蚁工蚁的形态特征,首次描述了该种雌蚁形态特征,给出了其与近缘种的区别,列出了世界凹头臭蚁属名录及分布信息,拍摄了工蚁和雌蚁成虫整体图,为该种的检疫鉴定、分布调查及防治提供参考。     

Measuring leaf area index in rubber plantations − a challenge

In order to estimate water use, water requirements and carbon sequestration of tropical plantation systems such as rubber it is adamant to have accurate information on leaf area development of the plantation as the main determinant of evapotranspiration. Literature commonly suggests a number of different methods on how to obtain leaf area index (LAI) information from tree plantation systems. Methods include destructive measurements of leaf area at peak LAI, indirect methods such as gap fraction methods (i.e. Hemiview and LAI 2000) and radiation interception methods (i.e. SunScan) or litter fall traps. Published values for peak LAI in rubber plantation differ widely and show no clear trend to be explained by management practices or the influence of local climate patterns. This study compares four methods for determining LAI of rubber plantations of different ages in Xishuangbanna, Yunnan, PR China. We have tested indirect measurement techniques such as light absorption and gap fraction measurements and hemispherical image analysis against litter fall data in order to obtain insights into the reliability of these measuring techniques for the use in tropical tree plantation systems. In addition, we have included data from destructive harvesting as a comparison. The results presented here clearly showed that there was no consistent agreement between the different measurements. Site, time of the day and incoming radiation all had a significant effect on the results depending on the devices used. This leaves us with the conclusion that the integration of published data on LAI in rubber into broad ranging assessments is very difficult to accomplish as the accuracy of the measurements seems to be very sensitive to a number of factors. This diminishes the usefulness of literature data in estimating evapotranspiration from rubber plantations and the induced environmental effects, both on local as well as regional levels.     

Assessing the effects of architectural variations on light partitioning within virtual wheat–pea mixtures

Background and Aims

Predicting light partitioning in crop mixtures is a critical step in improving the productivity of such complex systems, and light interception has been shown to be closely linked to plant architecture. The aim of the present work was to analyse the relationships between plant architecture and light partitioning within wheat–pea (Triticum aestivum–Pisum sativum) mixtures. An existing model for wheat was utilized and a new model for pea morphogenesis was developed. Both models were then used to assess the effects of architectural variations in light partitioning.

Methods

First, a deterministic model (L-Pea) was developed in order to obtain dynamic reconstructions of pea architecture. The L-Pea model is based on L-systems formalism and consists of modules for ‘vegetative development’ and ‘organ extension’. A tripartite simulator was then built up from pea and wheat models interfaced with a radiative transfer model. Architectural parameters from both plant models, selected on the basis of their contribution to leaf area index (LAI), height and leaf geometry, were then modified in order to generate contrasting architectures of wheat and pea.

Key results

By scaling down the analysis to the organ level, it could be shown that the number of branches/tillers and length of internodes significantly determined the partitioning of light within mixtures. Temporal relationships between light partitioning and the LAI and height of the different species showed that light capture was mainly related to the architectural traits involved in plant LAI during the early stages of development, and in plant height during the onset of interspecific competition.

Conclusions

In silico experiments enabled the study of the intrinsic effects of architectural parameters on the partitioning of light in crop mixtures of wheat and pea. The findings show that plant architecture is an important criterion for the identification/breeding of plant ideotypes, particularly with respect to light partitioning.     

从东南亚进口水果截获桔小实蝇复合种五近缘种的鉴别(双翅目:实蝇科)

介绍了近年从进口东南亚水果中经常截获的、最具经济重要性的桔小实蝇复合种5个近缘种:杨桃实蝇B.carambolae、桔小实蝇B.dorsalis、芒果实蝇B.occipitalis、木瓜实蝇B.papayae及菲律宾实蝇B.philippinensis,分别记述了翅、胸、足、腹及雌虫产卵器主要鉴别特征,并列出桔小实蝇复合种5近缘种鉴别特征检索表。