首页 | 官方网站   微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 46 毫秒
1.
灰色局势决策在林下间作作物组合优化中的应用   总被引:9,自引:0,他引:9  
一、前言混农林业是遵循生态学原理,按照人们的经营目的,将组成系统的各单元有机地结合起来,以协调系统的总体功能,最大限度地发挥系统的综合效益而建立的复合系统。近年来,尤其在发展中国家,由于人口急增,粮食短缺,环境恶化,滥伐森林,耕地锐减,水土流失,农、林业争地矛盾突出。为了充分、合理利用自然资源,提高土地利用率和光能利用率,农、林业科学工作者总结了传统的混农林  相似文献   

2.
根据灰色局势决策原理,利用目标赋权获得加权局势决策方法,对1996—1997年山东省大豆新品种区域试验结果进行分析,综合14个主要性状指标,排出各个品种的优劣,结果与生产实际一致。认为这是一种较全面、较合理的综合评价大豆品种优劣的方法。  相似文献   

3.
根据灰色局势决策原理,利用目标赋权获得加权局势决策方法,对1996—1997年山东省大豆新品种区域试验结果进行分析,综合14个主要性状指标,排出各个品种的优劣,结果与生产实际一致。认为这是一种较全面、较合理的综合评价大豆品种优劣的方法。  相似文献   

4.
基于2007年Landsat TM遥感影像和影响防护林的主导环境因子,对三峡库区的森林立地进行分类,并通过选取水源涵养量、生物量和林分生产力3个指标,利用多目标灰色局势决策模型对库区现有的针叶林、阔叶林、针阔混交林和灌木林4种防护林类型进行空间优化配置.结果表明: 2007年,三峡库区森林立地可划分为40种类型;空间配置优化后,研究区针叶林、阔叶林、针阔混交林和灌木林的面积比例分别为32.55%、29.43%、34.95%和3.07%.与优化前相比,优化后针叶林和灌木林的面积比例分别减少了8.79%和28.55%,阔叶林和针阔混交林分别增加了10.23%和27.11%.通过防护林类型的空间优化,三峡库区整体的水源涵养能力、生物量和林分生产力分别增加14.09×108 m3、0.35×108 t和1.08×106 t.  相似文献   

5.
多目标决策在小豆种质资源评价中的应用   总被引:3,自引:0,他引:3  
基于熵权的多目标决策分析模型,结合模糊数学和熵的思想,运用多属性决策分析中的双基点法,对小豆种质进行定量评价.经综合评价,8个小豆种质材料从优到劣的顺序为B00766、B01805、B00091、B00651、B01670、B00655、B00388、B00774,避免了由单一性状指标来判断参试材料优劣所造成的偏差,可为育种亲本优选提供理论依据.结果表明,多目标决策评价模型在少量小豆种质资源的评价中运算简便,易于掌握.  相似文献   

6.
桔园植保协调管理的多目标群决策研究   总被引:1,自引:0,他引:1  
植保系统工程是植保工作科学化的必然趋势,有关系统工程与具体植保工作相结合的理论研究较为丰富,然而,在更高的层次上,植保系统是多决策者、多目标的复杂系统,这就要求植保工作者必须学会用系统工程理论解决植保系统的协调管理问题。迄今这方面的研究  相似文献   

7.
辽宁省清原县森林资源结构及其空间优化配置   总被引:2,自引:0,他引:2  
利用RS、GIS技术和多目标灰色局势决策方法,综合森林的经济效益指标(生物量、林分生产力)和生态效益指标(涵养水源量、固土量),对清原县现有森林类型进行空间优化配置.结果表明: 经优化配置后,清原县森林类型的结构比例发生了明显的变化,其中针叶林和阔叶林面积由43%、51%减少到23%、31%,针阔混交林面积由3%增加到43%,灌木林面积保持不变;森林生态系统生物量、林分生产力分别增加0.6%、2.1%,而涵养水源功能增加31.7%,固土功能基本保持不变,在保留较高木材生产效益的同时,可充分发挥涵养水源功能,实现森林生态系统经济效益和生态效益的最大化.  相似文献   

8.
农作物花粉高温胁迫研究进展   总被引:6,自引:0,他引:6  
高温现已成为农作物生产不可忽视的环境因素,而花粉是农作物对高温最敏感的器官.本文从细胞学、生理学和分子生物学等方面对近年来国内外有关农作物花粉高温胁迫的研究进行了综述,以期为保持农作物在高温胁迫下的高生产力提供思路.高温对农作物花粉的细胞学影响表现在绒毡层粗糙型内质网排列方式改变、药隔维管束鞘细胞形状异常、花粉管高尔基体小泡产生减少等方面;生理学影响表现在Ca2+动态平衡无法及时恢复、生长调节物质含量改变以及糖代谢减慢等方面;分子生物学影响表现在热激蛋白诱导表达不足和其他花粉功能基因表达被抑制等方面.  相似文献   

9.
10.
早熟桃最佳采收期的多目标决策模型研究   总被引:1,自引:0,他引:1  
本文在拟合出早熟桃品种早花露品质诸项指标变化曲线的基础上,结合市场价格变化,以经济效益作为目标函数,建立了适时采收的多目标决策模型,并由此求出该品种在合肥地区最佳采收期是5月24日,为早熟桃生产取得最佳经济效益提供理论指导.  相似文献   

11.
The target rate of afforestation in Ireland over the next 30 years is 20,000 ha per year, which would result in an increase of the forest cover from the current 10% to 17%. In order to promote sustainable forest management practices, it is essential to know the composition and conservation value of habitats where afforestation is planned and the effects of subsequent planting upon biodiversity. The objectives of this study were to investigate changes in vegetation composition and diversity of grasslands 5 years after afforestation with Sitka spruce (Picea sitchensis) and determine the primary ecological and management factors responsible for these changes. Species cover, environmental and management data were collected from 16 afforested and unplanted improved and wet grassland site pairs in Ireland. Our results indicate that 5 years after tree planting, there were significant changes in richness, composition, and abundance of species. Competitive and vigorous grasses were more abundant in planted than in unplanted sites, as were generalist species found in both open and wooded habitats, while small-stature shade-sensitive species were less abundant. Vascular plant species richness and Shannon’s diversity index were higher in unplanted wet grassland, than in the planted sites. Bryophyte species richness was higher in planted improved grassland than in unplanted sites. The differences were primarily the result of the exclusion of grazing, ground preparation, changes in nutrient management and drainage for afforestation. Drainage ditches provided a temporary habitat for less competitive species, but the overall effect of drainage was to reduce the diversity of species dependent on wet conditions. Variance partitioning showed differences in the relative influences of environmental and management variables on biodiversity in the two habitats, probably due to the greater pre-afforestation grazing pressure and fertilisation levels in improved grasslands. The differences in biodiversity between planted and unplanted grasslands indicate that afforestation represents a threat to semi-natural habitats where distinctive and highly localised plant communities could potentially occur.  相似文献   

12.
This work examines the influence of different post-planting treatments in the development of afforested Holm oak, Quercus ilex L. subsp. ballota (Desf.) Samp., in an abandoned agricultural field in SE Spain. A total of nine post-planting treatments were carried out: tilling spring and autumn in different years, spreading of organic and inorganic mulch, irrigation in different periods. Soil preparation prior to planting consisted of digging of a hole with a backhoe excavator of 80 HP and homogenized the profile characteristics. Survival, nutrient concentrations in both leaves and soil, and foliage surface have been studied. Dry-season irrigation every 2 weeks provided the best survival rate (98.3%), while mulching with solid urban wastes caused the worst results (6.6%). The supply of forest debris increased the N, K, and Mn concentrations at all depths with respect to the other treatments, and the solid urban waste had the same effect in N, P, K, Na, Cu, Fe, and Zn. All the foliar nutrients decreased in 2005 with respect to the 2004 sampling, except in N, Cu, and Zn. The use of foliar nutrient concentrations, together with the increase in leaf surface is proposed as a non-destructive index of development and of forestation stands in the first stages of growth. The application of forest debris, and particularly the placement of boulders in the beds of individual trees proved most effective in sapling development.  相似文献   

13.
Climatic ecoconditions were analysed ofPanax quinquefolium (P.q.) growing indigenously and as introductions. Four climatic indices, namely annual precipitation, annual mean relative humidity, and mean monthly temperature in July and January, respectively were selected as the judge index for introducing P.q. Through applying the methods of grey gather and grey relative analysis in grey system theory, the four climatic indices of 43 counties for typical classification in the Qinba Mountain Regions (QMR), and climatic similarity was calculated of about 43 counties with that of the state of Wisconsin, USA. According to the results and conditions of topography, geomorphology, vegetation, soil etc. in the QMR, a map was drawn of climatic regions suitable for introducing P.q., and the climatic features of each region are discussed.  相似文献   

14.
王益人 《人类学学报》2018,37(4):590-601
晋西南古称河东,位于汾渭地堑中部,包括临汾盆地、运城盆地以及中条山南麓黄河沿岸。这里自古就是中华民族文明重要发祥地,也是研究人类起源、发展、演化的重要地区。20世纪50年代以来,考古工作者在山西地堑发现了300余处旧石器时代遗址和地点。这些发现业已证明晋西南的临汾、运城以及中条山南麓黄河沿岸,从早更新世初期直到更新世结束一直有人类在这片土地上繁衍生息。其中西侯度遗址、匼河遗址群、丁村遗址群、下川遗址群、柿子滩遗址群,代表了东亚旧石器时代人类200万年以来从能人→直立人→早期智人→晚期智人各个不同发展阶段一个完整的演化历程。因此,这里成为中国大陆一个非常重要的远古人类演化场。本文试图通过对这一区域旧石器考古的回顾,找出我们工作中的不足以及需要努力的方向,并向本地区考古学研究的开拓者贾兰坡、王建、王择义等老一辈考古学家致敬。  相似文献   

15.
山西野生有毒植物组成   总被引:4,自引:1,他引:4  
有毒植物是能引起人类或其它生物中毒死亡或有机体长期或暂时性伤害的植物。但是,有毒植物也有积极有益的一面.在人类生活、生产中起着很大作用。本文中重点介绍了山西有毒植物的组成.计47科、105属、150种.其中草本植物126种,木本植物24种.并对有毒部位与毒性作了说明.最后对有毒植物应用前景作了简要分析。  相似文献   

16.
Summary Maturing axolotl oocytes which are treated with protein synthesis inhibitors or which are heat-shocked can be induced to reorganize their cytoplasm and to form an early grey crescent. The maturing axolotl oocyte has been used as a model system to study the role of the cytoskeleton in dorsoventral polarization as visualized by grey crescent formation. Results presented here provide evidence for the involvement of microtubules in the formation of the early grey crescent. Whereas inhibitors of microtubule polymerization and antibodies against tubulin both elicit early grey crescent formation, the effect of taxol shows that microtubule polymerization is required at a late stage in this event. The nucleus furnishes important factors required for early grey crescent formation and might play a role in microtubule polymerization.  相似文献   

17.
Aim, Scope and Background  When materials are recycled they are made available for use for several future life cycles and can therefore replace virgin material more than just once. In order to analyse the optimal waste management system for a given material, the authors have analysed the material flows in a life cycle perspective. It is important to distinguish this approach for material flow analysis for a given material from life cycle analysis of products. A product life cycle analysis analyses the product system from cradle to grave, but uses some form of allocation in order to separate the life cycle of one product from another in cases where component materials are recycled. This paper does not address allocation of burdens between different product systems, but rather focuses on methodology for decision making for waste management systems where the optimal waste management system for a given material is analysed. The focus here is the flow of the given material from cradle (raw material extraction) to grave (the material, or its inherent energy, is no longer available for use). The limitation on the number of times materials can be recycled is set by either the recycling rate, or the technical properties of the recycled material. Main Features  This article describes a mathematical geometric progression approach that can be used to expand the system boundaries and allow for recycling a given number of times. Case studies for polyethylene and paperboard are used to illustrate the importance of including these aspects when part of the Goal and Scope for the LCA study is to identify which waste management treatment options are best for a given material. The results and discussion examine the different conclusions that can be reached about which waste management option is most environmentally beneficial when the higher burdens and benefits of recycling several times are taken into account. Results  In order to assess the complete picture of the burdens and benefits arising from recycling the system boundaries must be expanded to allow for recycling many times. A mathematical geometric progression approach manages to take into account the higher burdens and benefits arising from recycling several times. If one compares different waste management systems, e.g. energy recovery with recycling, without expanding the system to include the complete effects of material recycling one can reach a different conclusion about which waste management option is preferred. Conclusions  When the purpose of the study is to compare different waste management options, it is important that the system boundaries are expanded in order to include several recycling loops where this is a physical reality. The equations given in this article can be used to include these recycling loops. The error introduced by not expanding the system boundaries can be significant. This error can be large enough to change the conclusions of a comparative study, such that material recycling followed by incineration is a much better option than waste incineration directly. Recommendations and Outlook  When comparing waste management solutions, where material recycling is a feasible option, it is important to include the relevant number of recycling loops to ensure that the benefits of material recycling are not underestimated. The methodology presented in this article should be used in future comparative studies for strategic decision-making for waste management. The approach should not be used for LCAs for product systems without due care, as this could lead to double counting of the benefits of recycling (depending on the goal and scope of the analysis). For materials where the material cycle is more of a closed loop and one cannot truly say that recycled materials replace virgin materials, a more sophisticated approach will be required, taking into account the fact that recycled materials will only replace a certain proportion of virgin materials.  相似文献   

18.
山西省金藻植物新纪录   总被引:1,自引:0,他引:1  
冯佳  谢树莲 《植物研究》2010,30(6):651-659
通过对山西所采集的金藻植物标本的鉴定和统计整理,共报道山西省金藻植物新纪录34种1变种,隶属于6科15属。对这些藻类植物的形态、生境和地理分布做了简要描述,凭证标本存放于山西大学生命科学学院标本室(SXU)。  相似文献   

19.
晋东南山地种子植物区系研究   总被引:3,自引:0,他引:3  
晋东南山地有野生种子植物974种,隶属于456属125科,其中裸子植物7科11属15种,被子植物118科445属959种(其中双子叶植物104科396属833种,单子叶植物14科,49属126种)。种子植物属的区系成分复杂多样,以温带成分占绝对优势(温带属250属,占总属数的60.98%)。种子植物种的区系成分中,中国特有种占绝对优势,共有383种,占总种数的39.32%,它们是构成晋东南山地森林植被和灌丛植被的建群种和优势种的主要成分。  相似文献   

20.
山西植被空间格局及演替   总被引:1,自引:0,他引:1  
在ArcGIS软件中采集1984年和2005年山西植被类型的图形,得到山西群系、森林、灌丛、草本植被及栽培植被的图形及面积,用叠置分析和景观格局分析方法研究植被的空间分布及其演替、空间格局及其变化。森林在西南部相对集中分布,在西北角增加明显,它在山西植被中所占面积及比重都最小,最为破碎。油松林在山西森林中占优势,恢复森林主要是油松林、小叶杨林、辽东栎林。1984年灌丛的面积在植被中最大,所占比例也最高,超过50%,集中连片分布面积较大,但灌丛缩减迅速,主要在中南部,在山西植被中遭破坏最为严重。沙棘、虎榛子灌丛和黄栌、连翘灌丛对灌丛的影响最大。草本植被主要在北部减少,在中南部分散增加,更加破碎。白羊草草丛在山西草本植被中占优势,蒿、禾草草原和百里香、禾草草原变化最大。栽培植被明显增加,在植被中所占比重急剧增加,成为山西优势植被。森林、栽培植被分别增加24.3%、71.5%,而灌丛、草本植被却分别减少70.3%,15.6%,演替主要是人为因素造成的。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司    京ICP备09084417号-23

京公网安备 11010802026262号