贵州喀斯特山地主要造林树种生长耗水量研究

针对我省喀斯特山地临时性干旱影响造林成活率和保存率的问题，分别测定了花椒、香椿等24个主要造林树种水分耗损量，根据不同树种3、4、5、6月份生长所需水量，为喀斯特山地造林树种和造林季节选择提供参考。     

喀斯特生态经济技术开发与示范

石漠化是喀斯特脆弱生态环境下,人类不合婵的社会经济活动而造成植被破坏、水土流失、土地生产力衰退丧失,地表呈现类似荒漠景观的岩石逐渐裸露的演变过程。石漠化具有易发生、退化快、恢复难、危害大等特点。清镇市作为贵州省喀斯特石漠化治理的重点县（市、区）之一,通过多年研究实践,完成了喀斯特生态经济植被恢复技术开发与示范项目,其主要任务是培育适生的经济林木树种或筛选当地适生优良树种在示范基地阳．呻植,并配套研究出喀斯特石漠化山地植被恢复的技术,形成喀斯特石漠化山地植被恢复技术标准。     

喀斯特困难地段退耕还林工程布局与模式

本文针对织金渔塘村喀斯特困难地段退耕还林的难点，按照系统工程的原理，以生态学理论作为其理论基础，在因地制宜、适地适树，可持续发展原则、政策引导和农民自愿相结合的原则指导下，把整个喀斯特小集水区分耕作区、经济林区、水土流失拦截区和生态治理区，并提出了相应的退耕还林模式。在造林实践的基础上，提出了5点认识与体会。     

迁安市退耕还林十佳种植模式

为了贯彻国务院《退耕还林条例》 ,规范退耕还林活动 ,坚持生态优先原则 ,优化结构 ,增加农民收入 ,提高生态、经济、社会综合效益 ,根据我市实际情况 ,总结推广了退耕还林十佳种植模式。1　针阔混交模式该模式的特点是针叶树与阔叶树带状或块状混交 ,形成多树种、多层次的针阔混交林 ,使得林分结构更复杂 ,生态功能更完备 ,生态群落更稳定 ,防护作用更显著 ,生物产量与经济效益更高。该模式适宜的立地条件是 :高山、远山、石质裸岩山地不便种植经济林树种但可营造水源涵养林、水土保持林的山地。适宜种植的针叶树种有 :油松、侧柏 ,阔叶树…     

顶坛喀斯特峰丛干热河谷山地林草建植技术

针对顶坛喀斯特峰丛干热河谷山地的特点，介绍了花椒、石榴、翅荚木等树种的造林技术，皇竹草、菊苣等牧草的种植技术。     

乌江流域喀斯特石质山地人工造林配套技术

本文提出喀斯特石质山地人工造林措施制订应以围绕树种水分平衡，即解决土壤与苗木间水分供需矛盾为核心，在基础研究和试验研究结果基础 ，制订出适宜喀斯特石质山地人工造林的配套技术，包括树种选择，育苗，整地，造林方法，林分结构和幼林抚育等。按此配套技术实施，可取得较高的造林保存率。     

河池市石山区农林经营开发的几种模式

我国是世界三大喀斯特岩溶地貌集中分布区之一，全国有喀斯特总面积约10000多万hm^2，主要集中分布在西南地区，其中贵州、广西、云南3省(区)总面积3280万hm^2，石漠化总面积达670．8万hm^2。广西有200多万hm^2石漠化山地，占石山面积29％，石漠化地区遍布79个县(市、区)，涉及贫困人     

湖南省退耕还林优化造林模式选择

参考湖南省林业建设总体区划,将项目区划分为洞庭湖区、湘中丘陵区、雪峰山区、南岭山区和武陵山区五个区域。把生态建设摆在第一位的前提下,根据退耕还林地域地形地貌特点,分别优化选择造林树种和造林模式。     

对迪庆州因地制宜实施退耕还林的探讨

分析了迪庆州自然地理和社会经济情况，根据迪庆州的区域、气候特点提出了退耕还林布局、树种选择和造林模式，并对迪庆州退耕还林的成效进行了分析。     

香椿山地造林技术初探

香椿是贵州乡土树种,普遍受到老百姓的喜爱,是优良的用材和生态树种.文章结合贵州山区特点,简要介绍了山地香椿人工造林生产实践经验并加以概括总结,以供借鉴.     

一种改进的机动目标拦截算法

机动目标的拦截问题可以用"追逃游戏"模型描述,考虑追击者的惯性、控制量有限等动力学特征时,拦截位置和控制量的确定是非常困难的.针对平面机动目标的拦截问题,以机器人拦截足球为模型,提出了一种改进的拦截算法——改进的"预测-规划-执行"法,通过预测机动目标的运动轨迹,提出了一种快速简便地确定粗略拦截位置的试探方法,在此基础上,再确定机器人的控制速度和精确拦截位置,控制机器人朝拦截位置运动.最后,给出了仿真计算结果,并应用于机器人足球比赛,仿真计算表明,算法可以准确有效地拦截运动目标.     

浅析公园景观的空间设计手法——以深圳市人民公园为例

公园是为人们提供游览观赏景观和休闲活动空间的地方。景观空间的设计显得尤其重要。而如何创建优美的空间,营造怡人的环境．是景观设计师要面临的问题。通过深圳市人民公园的实例,对其实地调查以及所营造的各类怡人空间进行分析,总结其园林空间艺术特色,探究其处理方法,以期对公园空间环境处理有借鉴意义。     

现代林学、森林与林业

论述了林学、森林与林业近两个多世纪以来的发展和变化.林学经历了由传统林学向现代林学的转变.现代林学是以森林生态系统的营建、经营管理和利用为研究对象，以发挥森林生态系统的生态环境功能为核心，全面发挥森林的多种效益和多种功能为目的的学科.对森林的认识也经历了由单株树木到树木群体到森林生态系统的变化.由于对林学及森林认识的深刻变化，人们对林业的认识也就从长期形成的以木材利用为中心，转变到以发挥森林生态系统的生态环境作用为核心和重点，全面发挥森林的生态、经济和社会功能作为林业的指导思想和目标，以实现林业的可持续发展.     

不同林龄光皮桦生物量分布初探

对3个不同年龄的光皮桦生物量分布规律的研究结果表明:在2～4年内,光皮桦单株生物量随年龄的增大而迅速增大,表现出良好的速生性,4年生时单株生物量是3年生的238.0%,是2年生生物量的363.4%。从单株生物量的组成来看,干所占比例随年龄增大而增大,从2年生时的45.8%,增加到3年生时的56.4%和4年生的58.2%,枝、叶所占比例则随年龄增加而下降,其中枝的比例从2年生时的26.7%下降到3年生时的20.5%和4年生时的21.6%,叶的比例从2年生时的3.6%下降到3年生时的2.3%和4年生时的2.2%。而不同年龄根系的生物量均表现为主根>侧根>细根。随着林龄的增加,光皮桦单株根冠比在下降,即从2年生时的0.31下降到4年生时的0.22。     

现代林学、森林与林业(英文)

文章论述了林学、森林与林业近两个多世纪以来的发展和变化 .林学经历了由传统林学向现代林学的转变 ,现代林学是以森林生态系统的营建、经营管理和利用为研究对象 ,以发挥森林生态系统的生态环境功能为核心 ,全面发挥森林的多种效益和多种功能为目的的学科 .对森林的认识也经历了从认识单株树木、树木群体到森林生态系统的变化 .由于人们对林学及森林认识的变化 ,使人们对林业的认识也从长期形成的以木材利用为中心 ,转变为发挥森林生态系统的生态环境作用为核心和重点 ,全面发挥森林的生态、经济和社会功能作为林业的指导思想和目标 ,以实现林业的可持续发展     

Twist of wood studs: dependence on spiral grain gradient

Distortions due to moisture changes during drying or in service are a major problem for construction timber. Twist, caused mainly by the cylindrical geometry, the orthotropic nature of the wood material, and the tendency of the wood fibers to grow in a spiral around the stem, is often regarded as the most detrimental distortion of sawn timber. There is a need for a basic mechanical understanding of how the twist distortion arises and also a need for a simple formula to predict the amount of twist distortion. In this article such a formula is proposed, and theory and experimental data that indicate the validity of the formula are shown. The first term in the formula is a modification of a traditional expression which is proportional to the mean value of the spiral grain angle in the cross section in question. The second term in the formula is new and is proportional to the gradient of the spiral grain angle, and this term normally counteracts the first term so that a stud with a left-handed spiral grain might achieve a right-handed twist. Linear elastic finite element method (FEM) results and comparisons with experimental data show that the formula works well and that linear FEM calculations exaggerate the twist, which is probably partly due to nonlinear effects. The formula could be used to predict the twist of sawn timber from measured spiral grain angles on the log surface.     

Adoption of improved fallow technology for soil fertility management in Zambia: Empirical studies and emerging issues

In the subsistence-agricultural region of eastern Zambia, less than 10% of the households have adequate supply of maize (Zea mays L.), the staple food, throughout the year. A major constraint to increasing crop production in the region is poor fertility status of the soil. In order to address this problem, improved fallow has been introduced as a technology for improving soil fertility within a short span of two to three years. Farmers have been testing the technology and a number of empirical studies have been undertaken over the years to identify the factors influencing farmers' decision to adopt the technology. This paper presents a synthesis of the results of adoption studies and highlights generic issues on the adoption of improved fallows in Zambia. The synthesis indicates that farmers' decision on technology adoption does not have a simple directed relationship of some technological characteristics only, but constitutes a matrix of factors including household characteristics, community level factors, socioeconomic constraints and incentives that farmers face, access to information, local institutional arrangements and macro policies on agriculture. The adoption of improved fallows is not strictly speaking a binary choice problem but a continuous process in which farmers occupy a position along a continuum in the adoption path. Further, adoption of improved fallows may not take place in a policy vacuum but needs to be facilitated by appropriate and conducive policy and institutional incentives. Several questions and issues that require further study emerge from the synthesis. These include determination of the relative importance of the factors in the adoption matrix, identification of the conditions under which farmers use a combination of inputs and their profitability under changing price scenarios, exact definition to delineate between `non-adopters', `testers' and `adopters' of agroforestry technologies, and understanding the impact of cash crop farming in farmers' adoption decisions of improved fallows (where off farm opportunities exist). Further, there is a need to determine the inter-relationship between household poverty, labor availability and the adoption of improved fallows and, to evaluate a combination of policy interventions at both national and local level to promote the adoption of agroforestry-based soil fertility management. This revised version was published online in June 2006 with corrections to the Cover Date.     

Improving cross drain systems to minimize sediment delivery using GIS

A well developed network of roads must exist as a necessary infrastructure system in modern forestry to facilitate forest operations. But forest roads have the potential to disrupt the drainage characteristics of watersheds and lead to negative impacts on the environment with increased erosion and sediment yields. Numerous factors affect surface erosion of roads and sediment production potential; determining and ranking them could be a guide for management decisions to erosion control. In this study, the CULSED model (as an extension of ArcGIS) was used to estimate sediment delivery and the distribution of a road network, given the existing culverts. Using the model, some culverts were added to the road network around places with high sediment delivery in order to minimize it. After a correlation analysis and adjustment between sediment production and the factors, i.e., road width, road gradient, age of road and vegetation cover, the trend of changes in sediment delivery with model changes in the input was investigated with a sensitivity analysis of the model. The results show that adding new culverts to the road resulted in a significant reduction of sediment delivery. The most important factor affecting sediment delivery was road width, followed by road gradient, vegetation cover and age of road. Road width and gradient were positively correlated with sediment delivery, while vegetation cover and age of road were negatively correlated. The best model to show the relation between sediment delivery and road width as well as with road gradient was a linear model, for vegetation cover a cubic equation and for road age a power model. The results of sensitivity analysis showed that sediment delivery had the greatest sensitivity to changes of road width and was least sensitive to changes in the age of the road. This model can help to estimate sediment delivery with its spatial distribution, which can be used for optimization of cross drain systems and strategies of sediment control. Application of the model requires field trials to acquire the necessary input data. The reliability of our results is a function of the accuracy of inputs, especially digital elevation model.     

Improving the flow of scientific information across the interface of forest science and policy

The ever-expanding knowledge base of forest science is a challenge for scientists, the public and decision-makers to incorporate into forest policy and management. Scientific assessments have been used as a process to synthesize information on a variety of resource issues, including climatic change. As a process of communication, three attributes of assessments, assessment capacity, stakeholder participation, and articulation of uncertainty, can strongly influence the ability of the assessments to communicate scientific information. The institutional structure of the USDA Forest Service to conduct resource assessments has allowed a sustained effort to conduct periodic synthesis of scientific information and to address new policy issues, such as climate change. The US National Assessment on Climate Variability and Change engaged diverse stakeholders, such as public and private decision-makers, resource and environmental managers, the general public and scientific experts in a broad national and regional dialogue about changes in climate, their impacts, and what can be done to adapt to an uncertain and continuously changing climate. Both the National Assessment and the Third Assessment Report of the International Panel on Climate Change incorporated a language of uncertainty to describe consensus of the scientific community on the report's conclusions. These attributes are important elements of improving the flow of information across the science–policy interface.