Cold tolerance of Acacia karroo and A. nilotica, two tree species from South Africa, in Beijing

Fynbos plant communities developed under geographic and climatic conditions unique to South Africa. Acacia karroo is the most widespread tree species, well known for its drought tolerance. A. nilotica exudes a good quality gum which is edible and suitable for confectionery. The two species have been introduced to China but little is known about their adaptability under the new environmental conditions. For our present study, the growth potential and physiological and biochemical parameters of the two species in response to cold stress were investigated. The results, measured as seed qualities (purity, thousand seed weights, germination, etc.) show differences between A. karroo and A. nilotica. The seed germination rate was between 10% and 60%. Seedlings were established in fields, pots and plugs. Those in the field grew well during the growing season but completely died in the winter. Those in pots or plugs were moved to and managed in the greenhouse. The plants were green in winter. The electrical conductivity of cells, the contents of water soluble sugars, proteins, malondialdehyde (MDA) increased during eight hours of low temperature treatment at 4℃. The activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) decreased markedly during the eight hours of 4℃treatment. We conclude that A. karroo and A. nilotica have little adaptability to the cold winter weather and cannot survive in the outdoors in the Beijing area, but could grow well indoors as ornamentals.     

Effect of alley cropping on soil aggregate stability of a tropical Alfisol

The beneficial effect of organic matter on soil aggregate stability is well documented. Alley cropping has been suggested as a possible alternative to maintain soil organic matter content in cropping systems without fallowing the land. The objective of this study was to asses the effect of alley cropping on dry and wet soil aggregate stability on land degraded by shifting cultivation. The aggregate size distribution by dry sieving, aggregate stability by wet sieving, soil organic Carbon content and soil bulk density were measured following two and three years of alley cropping with Gliricedia (Gliricidia sepium) and Pigeon pea (Cajanas cajan) in a tropical Rhodustalf. Alley cropping increased the mean aggregate diameter and water stability of soil aggregates. The mean aggregate diameter obtained from dry sieving increased from 1.3 mm of the control to 2.68 and 3.11 mm after three years in Pigeon pea and Gliricidia alley cropped plots, respectively. This is an indication of resistance to wind erosion in alley cropped plots. The wet aggregate stability which shows the resistance to erosion by water also increased in alley cropped plots. These increases were significant after three years of hedge row establishment. The increase in soil organic C in alley cropped plots contributed to the higher dry and wet aggregate stability, and decreased soil bulk density. The improvement was higher in plots alley cropped with Gliricidia than Pigeon pea. This study shows the importance of ally cropping in increasing aggregate stability of degraded sandy soils which in return reduce erosion by wind and water.     

落叶松人工林间伐技术优化研究*

本文以林分生长模型为基础，将林分的经营指数作为状态变量，将主伐时林分平均直径作为目标，将达到这一目标时林分总收获蓄积量作为指标函数，建立了离散确定性动态规划模型，编制了计算机模拟系统。利用此系统即可对落叶松不同培育目标下的最佳间伐时间、间伐强度和主伐年龄等进行决策。结果表明，优化决策方法在保留株数、间伐次数和总收获蓄积量上都优于一般决策方法，它既可对落叶松林分进行生长预测，也可为制定经营单位的经营     

赤松毛虫防治指标的研究

赤松毛虫(Dendrolimus spectabilis Butler)是山东省松树的主要害虫,常将成片的松树吃光,危害十分严重。目前在治虫工作中,往往只根据经验性“指标”决定防治与否,盲目性很大。因此,研究和提出一个准确有效的防治指标,具有非常重要的意义。我们于1986～1987年在山东省新泰市土门林场,对赤松毛虫防治指标进行了初步研究,现将结果整理报告如下。     

城市交通可持续发展探讨

面对城市化和城市机动化的双重压力,我国城市交通发展挑战与机遇并存.根据城市交通直接为城市服务的性质和特点,提出了城市交通建设要＂以人为本＂,全面规划,综合治理的指导思想;论述了城市道路建设要强调功能划分并发挥多功能作用,城市交通发展要与能源的合理利用和开发相协调,城市交通治理要注重生态环境的保护,城市交通管理要把安全意识和安全设施摆在首位等可持续发展模式.可供城市交通规划和建设参考.     

京津风沙源治理工程省级管理系统的分析与设计

对京津风沙源治理工程省级管理系统的分析、设计、功能等进行简单论述。     

广西田林县森林分类经营的探讨

田林县是广西重点林区县之一。在当前实施分类经营的新形势下 ,对需要确定的生态公益林和商品林的比例、范围、布局、经营方针、目标、林产业结构调整等问题进行了论述。森林分类区划界定的总面积为4 35 5 32 9hm2 ,其中生态公益林 16 2 94 2hm2 ,占 37 4 % ;商品林 2 72 5 90 9hm2 ,占 6 2 6 %。并提出了实施建议。     

内蒙古水土流失现状与治理对策

本文详述了内蒙古自治区水土流失类型、程度、面积和治理现状 ,总结了水土流失治理经验 ,并提出了新时期水土流失防治战略思想和治理对策     

生态经济林经营模式

在我国丘陵山区开展以经济林为骨干项目的多种经营,是繁荣农村经济的一项战略措施。生态经济林业就是遵循自然规律和经济规律,按照生态学和生态经济学的原理,运用系统理论与系统工程的方法,组织经济林生产建设事业。它的任务是为制定经济林生产发展战略规划:为经济林栽培经营提供指导理论和方法。生态经济林的实施主要是通过区划和规划。生态经济林经营模式,有网络结构模式和立体经营模式之分。前者是一个地域生态系统的整体结构中,经济林作为一个子系统的位置,后者是具体林分结构的立体经营模式,两者是相关联的。     

论森林工程与森林可持续经营

从森林工程与森林可持续经营关系入手，分析了森工作业对森林生态系统中生产者、消费者、分解者、非生物环境等因素的影响，提出了保证森林可持续经营的“生态森林工程”概念、模式和技术体系。