检索结果-南通市图书馆

A Study on Mechanisms of Drought Tolerance in Tree Species

在线全文

学校读者我要写书评

暂无评论

北京林业大学学报 1993年第S3期 1-9页

作者： li Jiyue Forest resources college,beijing forestry university

According to ways of responding to drought stress,two primary types of drought resistance intree species have been identified: (1)drought escape; (2)drought tolerance (including dehydration postponementwith high tissu... 详细信息

关键词： drought drought tolerance water stress water potential turgor pressure osmotic adjustment

Viscoelastic Characteristics and Creep Prediction for Laminated Veneer Lumber

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

北京林业大学学报 1992年第S2期14卷 117-129页

作者： Sun li’eDepartment of Forest Products and Engineering , beijing forestry university

The viscoelastic characteristics of Aspen laminated veneer lumber (LVD were investigated with results revealing the dynamic creep behaviour under asymmetrical cyclic loading, which is analogous to solid wood under a static load. Curves for the creep indicated that after 10s cycles, the multiple correlation coefficient R2 for the 4-element, is more than 0. 98 in any instance, overwhelmingly well fitted to the data obtained. The mean square error of the 3-element viscoelastic model was 1 - 5 times higher than of the 4-ele-ment model under various cyclic loadings within a relative large loading range. The viscoelastic curves for LVL samples are nonlinear. They were linearized at some stress levels below 60% of their limited intensities. As loading was sustained for a longer period, the viscous flow was found to have a tendency of attenuation. The work absorbed by a specimen before the occurrence of creep failure, could be estimated in terms of failure appearance. Consequently, we could calculate the

关键词： viscoelastic characteristics creep prediction laminatedveneer lumber

Relation of Mineralizable N to Organic N Components in Dark Loessial Soils

在线全文

学校读者我要写书评

暂无评论

Pedosphere 2003年第3期13卷 279-288页

作者： li JUMEI and li SHENGXIUcollege of Natural resources and Environmental Sciences, Northwestern Science and Technology university of Agriculture and forestry, Yangling, Shaanxi 712100 (China) college of Natural resources and Environmental Sciences Northwestern Science and Technology University of Agriculture and Forestry Yangling Shaanxi 712100 (China)

Mineralizable N and organic N components in different layers (0～15, 15～30,30～45, 45～60, 60～80 and 80～100 cm) of six soils with different fertilities sampled from YongshouCounty, Shaanxi Province, China, were determined by the aerobic incubation method and the Bremnerprocedure, respectively. Correlation, multiple regression and path analyses were performed to studythe relation of mineralizable N to organic N components. Results of correlation and regressionanalyses showed that the amounts of the N mineralized were parallel to, and significantly correlatedwith, the total acid hydrolyzable N, but was not so with the acid-insoluble N. Of the hydrolyzableN, the amino acid N and the ammonia N had a highly consistent significant correlation with themineralized N, and their partial regression coefficients were significant in the regressionequations, showing their importance in contribution to the mineralizable N. The amino sugar N, onthe other hand, had a relatively high correlation with the mineralized N, but their partialregression coefficients were not significant in the regression equations. In contrast, thehydrolyzable unknown N had no such relations. Path analysis further indicated that the amino acid Nand ammonia N made great direct contributions to the mineralized N, but the contributions of theamino sugar N were very low. These strongly suggested that the mineralized N in the soils tested wasmainly from the hydrolyzable N, particularly the amino acid N and ammonia N which are the majorsources for its production.

关键词： acid-insoluble N hydrolyzable N mineralizable N organic N component

Study on Community Diversity of Coastal Shelter Forest in Jiaonan

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Population,resources and Environment 2005年第3期3卷 42-47页

作者： Xu Jingwei 1,2, li Chuanrong 3, li Qi 4, Zheng li 3, & Wang Weidong 1 1 beijing forestry university,beijing 100871,China 2 Shandong Acdemy of forestry, Jinan 250014, China 3 college of forestry, Shandong Agricultural university, Taian 271018, China 4 Shandong Normal university, Jinan 250014, China beijing forestry university Beijing 100871 China Shandong Acdemy of forestry Jinan 250014 China college of forestry Shandong Agricultural University Tatan 271018 China Shandong Normal university Jinan 250014 China

Based on the research of the plots in coastal areas in Jiaonan city, Shandong Province, the indices of richness, evenness and diversity of different community types are analyzed. The results show that: The richness indices indicates that arbor layers are close to shrub layers, and both are lower than herbage layers; the ranges among communities vary a little except those of the arbor ones. Mostly the biodiversity indices reveal that herbage, the arbor, the shrub; Biodiversity of communities has great influences on microclimate to a certain extent and is under the control of regional environment.

关键词： coastalshelterforest richness biodiversity index microclimate

STUDY ON THE TEN MAJOR TREE SPECIES OCCUPYING GEOGRAPHICAL SPACE IN NATURAL SECONDARY FOREST USING SPACE ANALYSIS

在线全文

学校读者我要写书评

暂无评论

Journal of Northeast forestry university 1993年第2期4卷 51-56页

作者： li RuxiuNortheast forestry university 1. Northeast forestry university China

The paper studies ten major tree species occupying the space in naturalsecondary forests in Mao Er mountain *** space is divided into horizon,elevation,slope,aspect and topographic position *** features of the species of trees areexamined using the concept of distribution width and the method of space *** of analysis indicate that Aspen and Asian White Birch community of forests inthe area would become failing,and the distribution of Mongolian Oak and Mongolian lidenand Manchurian Walnut are limited by the slope and aspect and topographic ***,Maple,Manchurian Ash would become the major species constituting naturalsecondary forests in future in this area.

关键词： Species of tree Geographic space Distribution Space analysis

Thresholds of geographic environmental elements in sediment yield of drainage basins

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2005年第2期48卷 230-240页

作者： CHEN Hao, ZHOU Jinxing, CAI Qiangguo, LU Zhongchen & li Zhongyan Institute of Geographic Sciences and Natural resources Research, Chinese Academy of Sciences, beijing 100101, China Institute of forestry Science, Chinese Academy of forestry Science, beijing 100091, China Research Center for Eco-Environment Sciences, Chinese Academy of Sciences, beijing 100085, China Computing Institute of Science and Engineering, North China Electric Power university, beijing 102206, China 1. Institute of Geographic Sciences and Natural resources Research Chinese Academy of Sciences 100101 Beijing China 2. Institute of forestry Science Chinese Academy of Forestry Science 100091 Beijing China 3. Research Center for Eco-Environment Sciences Chinese Academy of Sciences 100085 Beijing China 4. Computing Institute of Science and Engineering North China Electric Power University 102206 Beijing China

Threshold of environmental elements in drainage basin sediment yield refers to, under effect of climate, underlying surface and human activity, a turning point of abrupt changes in drainage sediment yield related to environmental element characteristics. Previous studies on threshold of sediment yield of relevant drainage basins were mainly concentrated on impact of natural zones with a few researches on impact of other environmental elements. Particularly studies on compound environmental element threshold in drainage basin sediment yield remain blank today. Studies indicate that sediment yield in drainage basins is affected by compound interactions and complex actions. Based on single element analysis, the present paper gives quantitatively compound threshold of environmental elements affecting sediment yield of the drainage basin between Hekouzhen and Tongguan in the middle Yellow River by the method of multi-variant, polynomial formula regression analysis.

关键词： middle Yellow River, environmental element, sediment, sediment delivery mudule, threshold.

Phosphorylated cellulose nanofibers establishing reliable ion-sieving barriers for durable lithium-sulfur batteries

在线全文

学校读者我要写书评

暂无评论

Journal of Energy Chemistry 2024年第5期92卷 619-628页

作者： Zihao li Pengsen Qian Hongyang li He Xiao Jun Chen Gaoran li School of Materials Science and Engineering Nanjing University of Science and TechnologyNanjing 210094JiangsuChina National forestry and Grassland Administration Key Laboratory of Plant Fiber Functional Materials Fuzhou 350108FujianChina

The shuttle effect is among the most characteristic and formidable challenges in the pursuit of high-performance lithium-sulfur(li-S)***,phosphorylated cellulose nanofibers(pCNF)are intentionally engineered to establish an ion-sieving barrier against polysulfide shuttling and thereby improve battery *** phosphorylation,involving the grafting of phosphate groups onto the cellulose backbone,imparts an exceptional electronegativity that repels the polysulfide anions from penetrating through the ***,the electrolyte wettability and li^(+)transfer can be significantly promoted by the polar nature of pCNF and the facile li^(+)*** such,rational ion management is realized,contributing to enhanced reversibility in both sulfur and lithium *** a result,li-S cells equipped with the self-standing pCNF separator demonstrate outstanding long-term cyclability with a minimum fading rate of 0.013%per cycle over 1000 cycles at 1 C,and a decent areal capacity of 5.37 mA h cm^(-2) even under elevated sulfur loading of 5.0 mg cm^(-2) and limited electrolyte of 6.0 mL g^(-1).This work provides a facile and effective pathway toward the well-tamed shuttle effect and highly durable li-S batteries.

关键词： lithium-sulfur batteries Cellulose Phosphorylation Ion-sieving Shuttle effect

Dendroclimatological study of Sabina saltuaria and Abies faxoniana in the mixed forests of the Qionglai Mountains,eastern Tibetan Plateau

在线全文

学校读者我要写书评

暂无评论

Journal of forestry Research 2024年第1期35卷 72-82页

作者： Teng li Jianfeng Peng Tsun Fung Au Jingru li Jinbao li Yue Zhang School of Geography and Remote Sensing Guangzhou UniversityGuangzhou 510006People’s Republic of China college of Geography and Environmental Science Henan UniversityKaifeng 475004People’s Republic of China Institute for Global Change Biology School for Environment and SustainabilityUniversity of MichiganAnn ArborMIUSA Department of Ecology and Evolutionary Biology University of MichiganAnn ArborMIUSA Department of Geography University of Hong KongHong Kong SARPeople’s Republic of China HKU Shenzhen Institute of Research and Innovation Shenzhen 518057People’s Republic of China

Tree-ring chronologies were developed for Sabina saltuaria and Abies faxoniana in mixed forests in the Qionglai Mountains of the eastern Tibetan ***-growth relationship analysis indicated that the two co-exist-ing species reponded similarly to climate factors,although *** was more sensitive than *** strong-est correlation was between *** chronology and regional mean temperatures from June to *** on this relationship,a regional mean temperature from June to November for the period 1605-2016 was *** explained 37.3%of the temperature variance during th period *** major warm periods and five major cold periods were *** analysis detected significant interannual and multi-decadal *** also revealed the influence of the Atlantic Multi-decadal Oscillation,confirming its importance on climate change on the eastern Tibetan Plateau.

关键词： Tree-ring analysis Mixed forests Dendroclimatology Qionglai Mountains

A density-dependent matrix model and its applications in optimizing harvest schemes

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2006年第z1期49卷 108-117页

作者： Guofan Shao, WANG Fei, DAI limin, BAI Jianwei & li Yingshan Department of forestry and Natural resources, Purdue university, West Lafayette, IN 47907, USA Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China Inner Mongolia Agriculture university, Hohhot 010019, China Academy of Forest Inventory and Planning, State forestry Administration, beijing 100714, China 1. Department of forestry and Natural resources Purdue University West Lafayette IN 47907 USA 2. Institute of Applied Ecology Chinese Academy of Sciences Shenyang 110016 China 3. Inner Mongolia Agriculture university Hohhot 010019 China 4. Academy of Forest Inventory and Planning State Forestry Administration Beijing 100714 China

Based on temporal data collected from 36 re-measured plots, transition probabilities of trees from a diameter class to a higher class were analyzed for the broad-leaved-Korean pine forest in the Changbai Mountains. It was found that the transition probabilities were related not only to diameter size but also to the total basal area of trees with the diameter class. This paper demonstrates the development of a density-dependent matrix model, DM2, and a series of simulations with it for forest stands with different conditions under different harvest schemes. After validations with independent field data, this model proved a suitable tool for optimization analysis of harvest schemes on computers. The optimum harvest scheme(s) can be determined by referring to stand growth, total timbers harvested, and size diversity changes over time. Three user-friendly interfaces were built with a forest management decision support system FORESTAR?for easy operations of DM2 by forest managers. This paper also summarizes the advantages and disadvantages of DM2.

关键词： uneven-aged forestry, diameter transition model, harvesting intensity, diameter limit, sustainable forest management.