期刊文献+
共找到1,641篇文章
< 1 2 83 >
每页显示 20 50 100
Aging Mongolian pine plantations face high risks of drought-induced growth decline:evidence from both individual tree and forest stand measurements
1
作者 Mingyong Li Leilei Yang +2 位作者 Yu Cao Dedong Wu Guangyou Hao 《Journal of Forestry Research》 SCIE EI CAS CSCD 2024年第2期109-120,共12页
Discerning vulnerability differences among different aged trees to drought-driven growth decline or to mortality is critical to implement age-specific countermeasures for forest management in water-limited areas.An im... Discerning vulnerability differences among different aged trees to drought-driven growth decline or to mortality is critical to implement age-specific countermeasures for forest management in water-limited areas.An important species for afforestation in dry environments of northern China,Mongolian pine(Pinus sylvestris var.mongolica Litv.)has recently exhibited growth decline and dieback on many sites,particularly pronounced in old-growth plantations.However,changes in response to drought stress by this species with age as well as the underlying mechanisms are poorly understood.In this study,tree-ring data and remotely sensed vegetation data were combined to investigate variations in growth at individual tree and stand scales for young(9-13 years)and aging(35-52 years)plantations of Mongolian pine in a water-limited area of northern China.A recent decline in tree-ring width in the older plantation also had lower values in satellited-derived normalized difference vegetation indices and normalized difference water indices relative to the younger plantations.In addition,all measured growth-related metrics were strongly correlated with the self-calibrating Palmer drought severity index during the growing season in the older plantation.Sensitivity of growth to drought of the older plantation might be attributed to more severe hydraulic limitations,as reflected by their lower sapwood-and leaf-specific hydraulic conductivities.Our study presents a comprehensive view on changes of growth with age by integrating multiple methods and provides an explanation from the perspective of plant hydraulics for growth decline with age.The results indicate that old-growth Mongolian pine plantations in water-limited environments may face increased growth declines under the context of climate warming and drying. 展开更多
关键词 tree age Drought stress Mongolian pine plantation tree rings Remote sensing plant hydraulics
下载PDF
Tree species identity and interaction determine vertical forest structure in young planted forests measured by terrestrial laser scanning
2
作者 Mengxi Wang Lander Baeten +7 位作者 Frieke Van Coillie Kim Calders Kris Verheyen Quentin Ponette Haben Blondeel Bart Muys John Armston Hans Verbeeck 《Forest Ecosystems》 SCIE CSCD 2024年第3期266-275,共10页
Vertical forest structure is closely linked to multiple ecosystem characteristics,such as biodiversity,habitat,and productivity.Mixing tree species in planted forests has the potential to create diverse vertical fores... Vertical forest structure is closely linked to multiple ecosystem characteristics,such as biodiversity,habitat,and productivity.Mixing tree species in planted forests has the potential to create diverse vertical forest structures due to the different physiological and morphological traits of the composing tree species.However,the relative importance of species richness,species identity and species interactions for the variation in vertical forest structure remains unclear,mainly because traditional forest inventories do not observe vertical stand structure in detail.Terrestrial laser scanning(TLS),however,allows to study vertical forest structure in an unprecedented way.Therefore,we used TLS single scan data from 126 plots across three experimental planted forests of a largescale tree diversity experiment in Belgium to study the drivers of vertical forest structure.These plots were 9–11years old young pure and mixed forests,characterized by four levels of tree species richness ranging from monocultures to four-species mixtures,across twenty composition levels.We generated vertical plant profiles from the TLS data and derived six stand structural variables.Linear mixed models were used to test the effect of species richness on structural variables.Employing a hierarchical diversity interaction modelling framework,we further assessed species identity effect and various species interaction effects on the six stand structural variables.Our results showed that species richness did not significantly influence most of the stand structure variables,except for canopy height and foliage height diversity.Species identity on the other hand exhibited a significant impact on vertical forest structure across all sites.Species interaction effects were observed to be site-dependent due to varying site conditions and species pools,and rapidly growing tree species tend to dominate these interactions.Overall,our results highlighted the importance of considering both species identity and interaction effects in choosing suitable species combinations for forest management practices aimed at enhancing vertical forest structure. 展开更多
关键词 treeDivNet FORBIO Stand structural complexity Terrestrial laser scanning Vertical forest structure tree diversity planted forests
下载PDF
Studies on Rubber (<i>Hevea brasiliensis</i>) Trees Exist Plant Type after Planting and Available Tapping Tree of Rubber Plantation in China
3
作者 Dongling Qi Jiannan Zhou +1 位作者 Guishui Xie Zhixiang Wu 《American Journal of Plant Sciences》 2014年第20期3017-3021,共5页
Existing plant types of rubber tree after planting and available tapping tree were investigated, and there were about 28 rubber plantations with different tapping years of 8 varieties “CATAS7-33-97”, “CATAS8-79”, ... Existing plant types of rubber tree after planting and available tapping tree were investigated, and there were about 28 rubber plantations with different tapping years of 8 varieties “CATAS7-33-97”, “CATAS8-79”, “CATAS7-20-59”, “PR107”, “RRIM600”, “GT1”, “INA873”, “93-114”in South China. The results showed that there were six kinds of existing plant types of rubber tree after planting of rubber plantations, which were available tapping trees, wind damaged trees, cold damaged trees, tapping panel dryness trees, absent trees and weak trees, respectively. These data investigated also showed rubber trees under available tapping, stoppage due to tapping panel dryness, absence, wind damage, cold damage and weakness were counted and calculated and made up for 72.21%, 14.75%, 5.61%, 3.86%, 2.68% and 1.89%. Tapping panel dryness trees, wind damage and absent trees are major factors for the loss of tapping rubber trees in the rubber plantations. Of these investigated varieties, available tapping trees per 100 trees of rubber plantation of “PR107”at the 1st, 12th, 14th, 16th, 20th, 24th tapping year were 96, 67, 70, 75, 66, 46 trees in Hainan planting zone, respectively. Available tapping trees per 100 trees of rubber plantation of “RRIM600”at the 9th, 15th, 20th, 22nd tapping year were 88, 62, 55, 36 trees in Yunnan planting zone, respectively. Available tapping trees per 100 trees of rubber plantation of “93-114” at the 10th, 19th, tapping year were 94, 62 trees in Guangdong planting zone. These results showed that available tapping trees of rubber plantation decreased with increasing tapping age under different planting zones in China. 展开更多
关键词 RUBBER tree (Hevea brasiliensis) Exist plant Type Available TAPPING tree RUBBER plantations Different TAPPING Years China
下载PDF
Unit 11 Planting trees
4
作者 邱世才 《中学文科(初中语政外)》 2004年第7期48-49,共2页
关键词 UNIT11 planting trees 初中 英语 词汇 用法
下载PDF
Assessing Adaptability of Planted Trees Using Leaf Traits: A Case Study with Robinia pseudoacacia L. in the Loess Plateau, China 被引量:3
5
作者 JIN Tiantian LIU Guohua +2 位作者 FU Bojie DING Xiaohui YANG Lei 《Chinese Geographical Science》 SCIE CSCD 2011年第3期290-303,共14页
Leaf trait patterns and their variations with climate are interpreted as an adaptive adjustment to environment.This study assessed the adaptability of planted black locust (Robinia pseudoacacia L.) based on the analys... Leaf trait patterns and their variations with climate are interpreted as an adaptive adjustment to environment.This study assessed the adaptability of planted black locust (Robinia pseudoacacia L.) based on the analysis of leaf traits and the comparison of its leaf traits with inter-specific ones existing in the same area.We measured some water and N use related leaf traits: leaf dry mass per unit area (LMA) and N,P and K concentrations based on both leaf area (Narea,Parea and Karea) and leaf mass (Nmass,Pmass and Kmass) of R.pseudoacacia at 31 sites along a water stress gradient in North Shaanxi Province,China.The results show that leaves of R.pseudoacacia have high Nmass and low LMA in the study area.High Nmass and low LMA are usually representative of luxurious resource use,and will advance plant resource competitiveness in high-resource conditions.As a whole,LMA-nutrient relationships of R.pseudoacacia display patterns that are fairly similar to the inter-specific relationships in both direction and intensity.The tendency for LMA and Narea to increase with decreasing water availability and the positive correlation between LMA and Narea reflect the trend for R.pseudoacacia to enhance water use efficiency (WUE) at the expense of down-regulated photosynthetic N use efficiency (PNUE) and high construction cost in dry conditions.However,the positive relationship between LMA and Narea in high mean annual precipitation (MAP) area is either unremarkable or reversed with decreasing water availability.This implies a lower photosynthetic capacity and a higher construction cost for high-LMA leaves.The inter-specific relationship between LMA and Narea is positive and does not change with water availability.This difference between inter-species and intra-species may be due to more diversified anatomies and more specialised structures for inter-species than intra-species.The failure of R.pseudoacacia adaption to dry conditions reflected by LMA-Narea relationship may be partially responsible for the emergence of rampike and dwarf forms found frequently in dry conditions.Incorporating intrinsic characteristics of planted trees into vegetation restoration project will be instructive and meaningful for species selection. 展开更多
关键词 适应性评估 适应性种植 叶片性状 刺槐 黄土高原 树木 中国 单位面积
下载PDF
Group planting of cherry (Prunus avium L.) fosters growth and tree quality is superior to conventional row planting in Germany
6
作者 Somidh Saha 《Journal of Forestry Research》 SCIE CAS CSCD 2018年第4期1088-1099,共12页
Wild cherry trees produce high-quality timber and provide multiple ecosystem services. However, planting and tending cherry stands in conventional rows are too costly. Therefore, low density group planting was trialle... Wild cherry trees produce high-quality timber and provide multiple ecosystem services. However, planting and tending cherry stands in conventional rows are too costly. Therefore, low density group planting was trialled as an alternative to row planting. The mortality, growth, and quality of planted cherry trees were compared between the group and row planting. The influence of neighbourhood competition and light availability on growth and quality was studied. The group and row planting of cherry trees were established at a wind-thrown site in southwestern Germany in the year 2000. In group planting, five cherry seedlings and seven lime seedlings (Tilia cordata Mill.) were planted with a 1 x 1 m spacing. In total, 60 groups were planted per hectare with a 13 × 13 m spacing. In contrast, 3300 seedlings (2475 cherries and 825 limes) were planted per hectare in row planting with a 3 × 1 m spacing. Ten groups and plots (10 × 10 m) were randomly established in group and row planting stand, respectively. The survival rate, stability (height to diameter ratio), diameter, and height growth were significantly higher in group planting. In the group plantings,40.5% of cherry trees had straight stems and 13.5% had a monopodial crown compared with 15% with straight stems and 2% with a monopodial crown in row planting. The proportion of dominant cherry trees in canopy was 49% in groups compared with 22% in rows. The length of branch free bole was significantly higher in cherries planted in groups than those grown in rows. Intra- and interspecific competition reduced the growth and stability of cherry trees in row planting, but not in group planting. Light availability did not cause any significant effects on growth and quality between group and row planting. This first study on cherry group planting indicates that the survival rate, growth, and tree quality were higher in groups than in rows at this early development stage. The competition by naturally born seedlings was an important reason for the difference in performance between group and row planting. This study will encourage forest practitioners to establish more cherry group planting trials on multiple sites to test the effectiveness of this alternative technique as a tool of regeneration and restoration silviculture. 展开更多
关键词 Group planting tree growth tree quality Interspecific competition Intraspecific competition Photosynthetically active photon flux density Total sitefactor
下载PDF
Tree Planting:How Fast Can It Accelerate Post-fire Forest Restoration?——A Case Study in Northern Da Hinggan Mountains,China 被引量:1
7
作者 LI Xiuzhen HE Hong S +3 位作者 WANG Xugao XIE Fuju HU Yuanman LI Yuehui 《Chinese Geographical Science》 SCIE CSCD 2010年第6期481-490,共10页
In 1987,a catastrophic fire burned over 1330000 ha in the densely forested area of the Da Hinggan Mountains in the northeastern China.After the fire,intensive management including burned trunk harvesting and coniferou... In 1987,a catastrophic fire burned over 1330000 ha in the densely forested area of the Da Hinggan Mountains in the northeastern China.After the fire,intensive management including burned trunk harvesting and coniferous tree planting had been conducted to accelerate forest restoration.To study the long term effect of these activities on forest recovery,we used a simulation modeling approach to study long-term(300 years) forest dynamics under current planting and natural regeneration scenarios.Results indicate that under tree planting scenario in the severely burned area,the dominant species Dahurian larch(Larix gmelinii) can reach pre-fire level(60% of the area) within 20 years and the maximum abundance can reach nearly 90% within 100 years.While under natural regeneration scenario,it needs about 250 years to reach its pre-fire level.From the perspective of timber production,tree planting can bring twice as much timber volume as that under natural regeneration within 300 years,which is the average longevity of L.gmelinii.It needs about 70 years to reach the timber volume of pre-fire level under the planting scenario,whereas it requires at least 250 years to reach the timber volume of pre-fire level under natural regeneration scenario.Another dominant species Asian White birch(Betula platyphylla) responded negatively to the planting of coniferous species.In general,tree planting of coniferous species after fire can greatly accelerate forest restoration in terms of species abundance and target timber volume,with desirable ecological and economic returns. 展开更多
关键词 中国东北地区 森林恢复 特大火灾 大兴安岭 植树 兴安落叶松 种植面积 速度
下载PDF
Effect of the seeds provenance and treatment on the germination rate and plants growth of four forest trees species of Cote d’Ivoire
8
作者 Sélastique Doff ou Akaff ou AiméKouassi Kouame +5 位作者 Nestor Bi Boh Gore Georges Yao Abessika Henri Kouadio Kouassi Perla Hamon Sylvie Sabatier Jerome Duminil 《Journal of Forestry Research》 SCIE CAS CSCD 2021年第1期161-169,共9页
The rapid rate of deforestation in Cote d’Ivoire has led to loss of plant species diversity and also threatens some commercial tree species with extinction.Some reforestation and aff orestation has been completed.How... The rapid rate of deforestation in Cote d’Ivoire has led to loss of plant species diversity and also threatens some commercial tree species with extinction.Some reforestation and aff orestation has been completed.However,for some species,the numbers of surviving transplants has declined.Hence,it is necessary to develop properly adapted and resilient genotypes that can eff ectively support the programs of forest restoration.In this context we evaluated the eff ects of the provenances of seeds and of various treatments on the germination rates and on plant growth of four commercial trees species(Pycnanthus angolensis,Terminalia superba,Mansonia altissima and Pterygota macrocarpa).We analyzed these parameters for seeds of three provenances(Daloa,Akoupéand Daoukro)of four species and for thirty plants aged 6 months per provenance.Time to begin germination and time to reach maximum germination were similar among species,and were not infl uenced by either treatment or provenance.Untreated seeds and those soaked for 24 and 48 h in water at room temperature yielded the highest germination rates,irrespective of species or provenance.The one exception was P.angolensis,for which no germination was recorded.Within species,some provenances produced higher germination percentages than did others.No clear relationship was computed between the germination rate and the morphometric characteristics of the seeds which varied signifi cantly between provenances.Plant growth and morphological variability also depended greatly on provenance.Genetic factors might be implicated,therefore provenance trials should be undertaken and evaluated.Furthermore,molecular analysis should be undertaken to confi rm the implications of genetic factors and allow for genetic selection. 展开更多
关键词 Forest trees Seed germination plant growth PROVENANCE Cote d’Ivoire
下载PDF
The Technology and Application of the Tree Planting Baseplate in Bare Rock Area
9
作者 Xiaohan Zhou Hongkai Chen Hongmei Tang 《World Journal of Engineering and Technology》 2016年第3期1-7,共7页
The ecological greening technology of the bare rock area of the arbor governance be-longs to the field of ecological environment restoration, selection of suitable arbors for vegetation restoration in bare rock area, ... The ecological greening technology of the bare rock area of the arbor governance be-longs to the field of ecological environment restoration, selection of suitable arbors for vegetation restoration in bare rock area, vegetation recovery is the primary approach to governance the ecological environment of bare rock area. The reconstruction of bare rock area arbor-shrub-grass ecosystems is a global environmental science problem. Paying attention to Geological conditions with rich rock fissures and abundant groundwater in these fissures, following the idea to reconstruct ecosystem from arbor to shrub and grass and the principle one tree in a baseplate, authors develop a baseplate technique for tree planting in bare rock area. The baseplate includes the parent body, the root, and the cover to prevent evaporation. Especially, there are filled in nutritional soil for the parent body and the root, and the composition of nutritional soil are selected by test in laboratory, while optimal mix ratio of the composition is obtained. Then, application method in field is put forward. The technique can guarantee survival at early stage and growth in the later for tree planting in the baseplate. In particular, the root provides a good channel to guide tree roots into fissure rock and absorb groundwater in rock. Test in field shows that the baseplate technique has strong practicality in vegetation recovery of bare rock area. Test in field shows that the baseplate technique has strong practicality in vegetation recovery of bare rock area in the world. 展开更多
关键词 Bare Rock Area tree planting The Baseplate Technique Test in Field
下载PDF
Ecological stoichiometric comparison of plant-litter-soil system in mixed-species and monoculture plantations of Robinia pseudoacacia,Amygdalus davidiana,and Armeniaca sibirica in the Loess Hilly Region of China 被引量:1
10
作者 Senbao Lu Yunming Chen +1 位作者 Jordi Sardans Josep Penuelas 《Forest Ecosystems》 SCIE CSCD 2023年第3期411-424,共14页
We examined how afforestation patterns impact carbon(C),nitrogen(N),and phosphorus(P)stoichiometry in the plant-litter-soil system.Plant leaf,branch,stem,and root,litter,and soil samples were collected from mixedspeci... We examined how afforestation patterns impact carbon(C),nitrogen(N),and phosphorus(P)stoichiometry in the plant-litter-soil system.Plant leaf,branch,stem,and root,litter,and soil samples were collected from mixedspecies plantations of Robinia pseudoacacia with Amygdalus davidiana(RPAD),R.pseudoacacia with Armeniaca sibirica(RPAS),and monocultures of R.pseudoacacia(RP),A.davidiana(AD),and A.sibirica(AS)in the Loess Hilly Region.The results showed that in mixed-species plantations,R.pseudoacacia had lower leaf N and P concentrations than in monocultures,while both A.davidiana and A.sibirica had higher leaf N and P concentrations.Soil P limited tree growth in both afforestation models.Mixing R.pseudoacacia with A.davidiana or A.sibirica reduced N-limitation during litter decomposition.Average soil total N and P concentrations were higher in RPAS than in RPAD,and both were higher than the corresponding monocultures.The average soil C:N ratio was the smallest in RPAS,while the average soil C:P ratio was larger in RPAS than in RP.A positive correlation between N and P concentrations,and between C:N and C:P ratios,was found in litter and all plant organs of mono-and mixedstands.Alternatively,for N concentration and C:N ratio,the correlations between plant(i.e.,leaf,branch,root)and litter and between plant and soil were inverse between plantation types.RPAD has an increased litter decomposition rate to release N and P,while RPAS has a faster rate of soil N mineralization.RPAD was the best plantation(mixed)to improve biogeochemical cycling,as soil nutrient restrictions,particularly for P-limitation,on trees growth were alleviated.This study thus provides insights into suitable tree selection and management by revealing C:N:P stoichiometry in the plant-litter-soil system under different afforestation patterns. 展开更多
关键词 Stoichiometry plant LITTER Soil tree mixture Loess Plateau
下载PDF
The Safe Distance Between Road Lighting Fixtures and Street Trees
11
作者 PENG Yu ZHANG Haiyang +2 位作者 GUO Kaikai DING Yibo WANG Xudong 《Journal of Landscape Research》 2019年第2期41-43,共3页
The road lighting system and the road greening system, which are mutually interrelated and independent, are two important parts in the urban road environment. Unreasonable road lighting is easy to induce light polluti... The road lighting system and the road greening system, which are mutually interrelated and independent, are two important parts in the urban road environment. Unreasonable road lighting is easy to induce light pollution and has a great negative impact on the physiology and growth of garden plants in the urban green space. In this paper, 21 kinds of common tree species in the urban green space of Zhengzhou were selected as the research object, and the photosynthetic physiological parameters of landscape trees under the LED light source were observed using LI-6400 Photosynthesis System. This paper attempted to find the critical point for initiating photosynthesis of different types of tree species under a certain light source and then calculated the safe distance between lighting fixtures and landscape trees. The results showed that road lighting interfered with the photosynthetic physiological activities of the surveyed trees, affecting the normal dormancy of the plants at night; the sensitivity of different tree species to night lighting was different, and there were some differences in the light compensation points, so the corresponding safe distance was also different. It is hoped that this study can provide a valuable reference and scientific basis for urban road greening and lighting design. 展开更多
关键词 LANDSCAPE plants ROAD trees ROAD LIGHTING ROAD GREENING SAFE distance
下载PDF
Response of plant,litter,and soil C:N:P stoichiometry to growth stages in Quercus secondary forests on the Loess Plateau,China
12
作者 Juanjuan Zhang Xinyang Li +4 位作者 Meng Chen Linjia Huang Ming Li Xu Zhang Yang Cao 《Journal of Forestry Research》 SCIE CAS CSCD 2023年第3期595-607,共13页
Ecological stoichiometry is an important indicator of biogeochemical cycles and nutrient limitations in terrestrial ecosystems.However,little is known about the response of ecological stoichiometry to plant growth.In ... Ecological stoichiometry is an important indicator of biogeochemical cycles and nutrient limitations in terrestrial ecosystems.However,little is known about the response of ecological stoichiometry to plant growth.In this study,carbon(C),nitrogen(N),and phosphorus(P)concentrations were evaluated in plant tissues(trees,shrubs,and herbs),litter,and soil of young(≤40-year-old),middle-aged(41–60-year-old),near-mature(61–80-year-old),and mature(81–120-year-old)Quercus secondary forests on the Loess Plateau,China.Vegetation composition,plant biomass,and C stock were determined to illustrate their interaction with stoichiometry.Only tree biomass C signifi cantly increased with stand development.Leaf N and trunk P concentrationsgenerally increased,but branch P decreased with growth stage.Fine roots had the highest C and P concentrations at the middle-aged stage.In contrast,shrubs,herbs,litter,and soil C:N:P stoichiometry did not change signifi cantly during stand development.Leaf N and P were positively correlated with soil C,N,P,and their ratios.However,there was no signifi cant correlation between litter and leaves in terms of C:N:P stoichiometry.A redundancy analysis showed that soil N best explained leaf N and P variance,and tree biomass and C stock were related to biotic factors such as tree age and shrub biomass.Hierarchical partitioning analysis indicated that,compared with soil or litter variables,stand age only accounted for a relatively small proportion of leaf C,N,and P variation.Thus,secondary Quercus ecosystems might have inherent ability to maintain sensitive responses of metabolically active organs to environmental factors during stand aging.The results of this work help to elucidate the biogeochemical cycling of secondary forest ecosystems in tree development,provide novel insights into the adaptation strategies of plants in diff erent organs and growth stages,and could be used to guide fertilization programs and optimize forest structure. 展开更多
关键词 Ecological stoichiometry tree biomass C stock Understory plant Age Stand development
下载PDF
Evaluation of land suitability for Moringa oleifera tree cultivation by using Geospatial technology:The case of Dhidhessa Catchment,Abay Basin,Ethiopia
13
作者 Mitiku Badasa Moisa Muleta Ebissa Feyissa +5 位作者 Indale Niguse Dejene Firdissa Sadeta Tiye Kiros Tsegay Deribew Zenebe Reta Roba Mengistu Muleta Gurmessa Dessalegn Obsi Gemeda 《Oil Crop Science》 CSCD 2023年第1期45-55,共11页
Land suitability analysis of Moringa oleifera tree cultivation is important to enhance its product,as the demand forthis tree for medicinal values and food sources is increasing worldwide.Therefore,this study aimed to... Land suitability analysis of Moringa oleifera tree cultivation is important to enhance its product,as the demand forthis tree for medicinal values and food sources is increasing worldwide.Therefore,this study aimed to assess suitableland for Moringa oleifera tree cultivation by using the integration of multi-criteria evaluation with geospatialtechnologies in the Dhidhessa catchment,western Ethiopia.Five parameters,namely:slope,land use and landcover(LULC),soil texture,land surface temperature,and rainfall data,were used in this study.The land suitabilityevaluation of Moringa oleifera is classified into three classes as highly suitable,moderately suitable,and notsuitable.The results revealed that,about 344.4 km2(12.2%)of the area is categorized into highly suitable,and2343.7 km2(83%)is moderately suitable for Moringa tree,whereas,137.2 km2(4.9%)is categorized as notsuitable for Moringa oleifera tree cultivation.Hence,based on the finding of the study,we suggested that farmers andother stakeholders can cultivate Moringa oleifera trees in the Dhidhessa catchment. 展开更多
关键词 Moringa tree Medicinal plant Overlay analysis AHP MCE
下载PDF
基于有限元模型的上海市常见园林树种抗风性研究
14
作者 张德顺 姚鳗卿 +2 位作者 陈陆琪瑶 张振 陈莹莹 《中国园林》 CSCD 北大核心 2024年第5期125-131,共7页
风害是园林植物受到的主要自然灾害之一,每年由于台风导致的园林树木断枝倒伏等现象频频发生,严重威胁了城市的生态安全。树木形态差异是影响树木稳定性的主要因子,以15种上海市常见园林树木为研究对象,探究不同冠层特征对树木稳定性影... 风害是园林植物受到的主要自然灾害之一,每年由于台风导致的园林树木断枝倒伏等现象频频发生,严重威胁了城市的生态安全。树木形态差异是影响树木稳定性的主要因子,以15种上海市常见园林树木为研究对象,探究不同冠层特征对树木稳定性影响及不同树形对分枝特征变化的敏感性。通过对研究树种的有限元建模进行树木自振和风致破坏模拟,计算得到树木的力学响应特征值,然后结合树木断裂的失效弯矩和树木弯矩在不同风速条件下的变化规律,预测树木断裂的临界风速,结合灾后实地调研结果,综合比较不同树种的抗风能力。 展开更多
关键词 园林植物 有限元 抗风性 园林树木 树木形态
下载PDF
多边形沙地挖坑植树机设计与转动性能分析
15
作者 孟兆新 贾鑫宇 +2 位作者 崔立松 殷乐乐 乔际冰 《林业机械与木工设备》 2024年第2期18-21,共4页
为了改善土地荒漠化的问题,降低植树造林对人力的依赖性,提高造林的效率和质量,设计一台用于沙地的多边形挖坑植树机。基于三维建模软件UG软件设计出一种适用于沙地的多边形挖坑植树机的几何模型,通过动力学分析推导出拉动旋转框架所需... 为了改善土地荒漠化的问题,降低植树造林对人力的依赖性,提高造林的效率和质量,设计一台用于沙地的多边形挖坑植树机。基于三维建模软件UG软件设计出一种适用于沙地的多边形挖坑植树机的几何模型,通过动力学分析推导出拉动旋转框架所需的拉力,并导入动力学仿真软件ADAMS进行了动力学仿真分析,得到旋转框架转动过程中质心位移曲线、绕转动轴力矩变化曲线和质心速度变化曲线,从而为旋转框架转动过程提供了分析的依据并验证方案的可行性。 展开更多
关键词 多边形 植树机 动力学分析 动力学仿真
下载PDF
不同混交模式和种植密度对桉树混交林生长的影响 被引量:2
16
作者 向旺 韦振道 +5 位作者 伍琪 朱慧 莫云善 李秋荔 罗伟 任世奇 《桉树科技》 2024年第1期34-40,共7页
通过分析混交模式和种植密度对桉树混交林生长特征的影响,为桉树人工林高效、可持续经营提供科学依据。分别设置尾巨桉与红锥、黑木相思、白千层、香樟(B1),与灰木莲、大花序桉、米老排、柠檬桉(B2)2种混交模式和4种种植密度(A1:1.5 m&#... 通过分析混交模式和种植密度对桉树混交林生长特征的影响,为桉树人工林高效、可持续经营提供科学依据。分别设置尾巨桉与红锥、黑木相思、白千层、香樟(B1),与灰木莲、大花序桉、米老排、柠檬桉(B2)2种混交模式和4种种植密度(A1:1.5 m×2.0 m;A2:2.0 m×2.8 m;A3:2.5 m×3.5 m;A4:3.0 m×4.2 m),比较混交模式和种植密度对混交树种树高、胸径、材积和保存率的影响。结果表明:(1)混交模式对尾巨桉生长影响较小,但A3、A4显著增加尾巨桉胸径和单株材积;(2)种植密度对混交树种树高生长影响不显著,但黑木相思和灰木莲在A1种植密度处理下的胸径和单株材积显著低于其他密度处理;(3)大花序桉和米老排A1种植密度处理保存率显著低于A3和A4密度处理,混交树种不同种植密度之间保存率没有显著差异。综合分析,认为A3是较好的种植密度。 展开更多
关键词 桉树 混交树种 种植密度 生长量
下载PDF
基于故障树和产生式规则的故障诊断专家系统设计 被引量:2
17
作者 宋龙飞 陈玉清 金振俊 《中国舰船研究》 CSCD 北大核心 2024年第S01期84-92,共9页
[目的]为充分运用核动力装置的运行管理经验辅助核动力操纵人员进行故障诊断,设计一种船用核动力装置故障诊断专家系统。[方法]首先,根据故障树与产生式规则之间的逻辑一致性,提出一种将故障树知识转化为产生式规则的方法;然后,对采用... [目的]为充分运用核动力装置的运行管理经验辅助核动力操纵人员进行故障诊断,设计一种船用核动力装置故障诊断专家系统。[方法]首先,根据故障树与产生式规则之间的逻辑一致性,提出一种将故障树知识转化为产生式规则的方法;然后,对采用正、反向混合推理方法的专家系统知识库和推理机进行优化设计,并依据故障树最小割集和重要度分析结果设计正向推理策略以简化推理流程;最后,根据人工对故障状态判断的思路设计状态监测模块,实时采集关键设备参数以转化为专家系统可识别的设备信息。[结果]结果显示,采用所提方法可解决专家系统知识获取困难的问题,能在保证推理准确度的前提下提升推理效率,实现了专家系统的在线故障诊断功能。[结论]研究表明采用所提方法可提升专家系统获取知识的能力和推理效率,对保障核动力装置的运行管理安全具有重要意义。 展开更多
关键词 核动力装置 故障树 专家系统 产生式规则 故障诊断
下载PDF
覆膜方式对盆栽牡丹基质水热效应与植株生长的影响
18
作者 赵明君 史帅营 +5 位作者 史田 高双成 周爽 王占超 周文斌 史国安 《山东农业科学》 北大核心 2024年第4期46-55,共10页
探索不同覆膜方式对盆栽牡丹基质水热效应与植株生长的影响,以期寻找轻简高效的盆栽牡丹管理方式,对盆栽花卉工程苗的推广应用具有重要意义。覆膜是应对农业生产中降水少、热量不足的重要农艺措施,有助于改善根际微生态环境,提高农作物... 探索不同覆膜方式对盆栽牡丹基质水热效应与植株生长的影响,以期寻找轻简高效的盆栽牡丹管理方式,对盆栽花卉工程苗的推广应用具有重要意义。覆膜是应对农业生产中降水少、热量不足的重要农艺措施,有助于改善根际微生态环境,提高农作物产量和品质。本试验以盆栽不覆膜为对照(T0),设置5种覆膜方式:盆口上覆白膜(T1)、盆口上覆黑膜(T2)、盆口上覆白膜加盆底下覆黑膜(T3)、塑料盆上下均覆黑膜(T4)和塑料盆上下均覆白膜(T5),研究不同覆膜方式下盆栽牡丹基质的水热环境变化及其对植株发育和光合性能的影响。结果表明,与T0相比,冬春季T1和T5处理基质日最高温度均提高5.0℃以上,春季T1和T516天每盆分别累积节水1.065 kg和1.195 kg,说明覆膜方式显著影响盆栽牡丹基质的水热效应,改善盆栽牡丹基质的微生态环境。春夏季盆口覆白膜加快植株叶色由红转绿,增强植株的光合性能与生理代谢,有利于秋季落叶期各部分生物量的积累。各覆膜方式下牡丹秋季壮苗指数表现为:T1>T5>T3>T2>T4>T0,说明上覆白膜对植株生长发育最有利。相关分析表明,根系发育状况与植株壮苗指数呈显著或极显著正相关。进一步通径分析表明,提高植株生物量及叶片光合性能是实现壮苗的基础。基于盆栽牡丹植株生长状况进行聚类分析,将6个处理组合聚为三类,其中T1和T5聚为一类,为优势处理。鉴于仅盆口覆白膜不仅苗体长势最优,而且劳动生产成本低,符合轻简高效栽培原则,建议盆栽牡丹生产上优先选择盆口上覆白膜的管理方式。 展开更多
关键词 覆膜方式 牡丹 栽培基质 温度 水分 壮苗指数 工程苗
下载PDF
湖北省巴东县古树资源组成及其空间分布特征研究
19
作者 王沛然 游桂璇 +2 位作者 诸葛名名 达良俊 胡远东 《中国园林》 CSCD 北大核心 2024年第5期138-144,共7页
古树是全球生物多样性的重要组成部分,也是地方文化的重要载体。在全球生物多样性不断丧失尤其是古树资源持续减少的背景下,研究现存古树资源的组成和空间分布特征对古树的保育和生物多样性维持具有重要意义,同时为地区发展规划提供物... 古树是全球生物多样性的重要组成部分,也是地方文化的重要载体。在全球生物多样性不断丧失尤其是古树资源持续减少的背景下,研究现存古树资源的组成和空间分布特征对古树的保育和生物多样性维持具有重要意义,同时为地区发展规划提供物种资源。以中国典型少数民族聚居地湖北省巴东县的古树资源为研究对象,结合野外调查和历史文献查阅,分析了巴东县古树的物种多样性、空间分布格局及其影响因素,探讨了巴东县古树保护面临的挑战与策略。结果表明,共记录古树2192株,隶属41科85属121种,所含物种数量较多的是壳斗科、松科、蔷薇科、木兰科和樟科,地理分布区系整体呈现由热带向温带过渡的特点;优势物种包括核桃、银杏和油杉;包含国家级保护物种17种;三级古树的个体数和物种数均超过一级和二级古树;古树胸径主要介于40~100cm,冠幅集中于10~17m,树高大多为15~25m;不同乡镇内分布的古树数量和物种数的差异显著,且大多分布在林地、耕地和未利用土地内。巴东县古树保护总体较好,95%以上的古树长势良好;海拔高度、坡度、人口密度、土地利用方式和文化习俗是影响巴东县古树资源组成和分布的主要因素;分级保护、分类保护、环境保护教育和差异性保护性有利于古树资源的留存和合理利用。 展开更多
关键词 园林植物 古树资源 物种多样性 分布格局 留存机制 巴东县
下载PDF
果树木屑黑木耳袋栽基质研究
20
作者 司豆豆 李德毓 +2 位作者 彭浩 王梦姣 兰阿峰 《陕西农业科学》 2024年第4期23-27,31,共6页
黑木耳产业对栎木资源的依赖是该产业发展和生态文明建设不相适应的突出表现,因而选取果树替代传统栎木是促进黑木耳产业绿色生态发展的潜在途径。本文选取苹果树木屑、桃树木屑、桔树木屑和核桃树木屑为黑木耳主要栽培基质,通过菌丝生... 黑木耳产业对栎木资源的依赖是该产业发展和生态文明建设不相适应的突出表现,因而选取果树替代传统栎木是促进黑木耳产业绿色生态发展的潜在途径。本文选取苹果树木屑、桃树木屑、桔树木屑和核桃树木屑为黑木耳主要栽培基质,通过菌丝生长速度、菌丝密度、菌丝色泽以及锁状联合数目等指标考核最佳果木木屑袋栽基质。结果表明,黑木耳菌丝在桃树木屑袋料基质上生长最好,生长速度(5.62 mm/d)比对照组(5.24 mm/d)提高了7.25%;菌丝生长势较好,边缘整齐、浓密、色泽洁白且锁状联合数目较多;选取78%、82%、86%和90%等4个不同桃树木屑配比,通过不同袋料基质对桃树木屑黑木耳袋栽基质进行优化研究,最佳果木黑木耳袋栽基质配方为:桃树木屑78%、米糠19%、红糖1.5%、石膏粉1%、石灰粉0.5%,此时黑木耳菌丝的生长速度(10.06 mm/d)比对照组的生长速度(5.88 mm/d)提高了71.09%,且锁状联合数目最多。本研究结果表明,桃树可替代栎木进行黑木耳袋料栽培,为黑木耳产业的绿色高质量发展奠定基础。 展开更多
关键词 黑木耳 袋栽基质 果木枝条 桃树木屑 锁状联合
下载PDF
上一页 1 2 83 下一页 到第
使用帮助 返回顶部