Variation in sapwood thickness of Picea abies in Estonia depending on the tree age

Variation of sapwood thickness in terms of a linear measurement and a growth ring count with reference to the age was studied in dominant and suppressed Norway spruce trees. In the trees of both dominance classes the sapwood thickness increased in absolute terms, while its relative portion decreased with the age of the trees growing. Great differences were found in sapwood thickness between dominant and suppressed trees in linear measurements but not in the number of sapwood rings or the rate of the heartwood formation. The number of sapwood growth rings reached 40 in old trees. The index of vigour differed considerably in dominant and suppressed trees.     

Toxicity index and the time taken to incapacitate mice under combustion gases of burning wooden materials

The purpose of this study was to investigate the toxicity of combustion gases from burning wooden materials. The toxicant index and mice exposure experiment were used to evaluate the toxicity index. The time taken to incapacitate mice under the impact of burning 19 solid wood species and 7 kinds of plywood were investigated. The results showed that the toxicity index of burning solid wood ranged from 1.5 to 2.5, and its main toxicant was CO₂. The toxicant index of burning plywood was higher, ranging from 3.0 to 6.0, and its main toxicity was NO_x. A good correlation was observed between the time taken to incapacitate mice (Xs) and the weight loss rate of burning solid wood. When the concentration of CO was higher than 1% in the exposure chamber, the mice stopped their activity within 2min. The time taken to incapacitate mice (Xs) and the minimum concentration of O₂ in the exposure chamber could be represented by a positive linear regression formula. The concentrations of O₂ and CO₂ exhibited a positive effect and the concentration of CO had a negative effect on the Xs values of mice.Part of this paper was presented at the 52nd Annual Meeting of the Japan Wood Research Society, Gifu, April 2002     

次生低产林改造是森林资源持续发展的有效措施

以可持续发展的理论为依据,分析了山西省低产林改造现状、存在的问题及更新方式,并对低产林改造的效益作了分析。     

湖南省森林火灾应急资源规模测度指标体系研究

从影响森林火灾应急资源建设规模的因素入手,分析其与应急资源规模之间的关系,并采用统计学的变异系数法和相关系数法对指标进行筛选,从而构建起确定森林火灾应急资源规模的指标体系.结果表明,湖南省森林火灾应急资源的建设规模与当地的经济、交通、人口密度、森林资源分布、火灾频度等密切相关.     

Manual recording of minirhizotron data and its application to study the effect of herbicide and nitrogen fertiliser on tree and pasture root growth in a silvopastoral system

The use of a simple counting method using a borescope and minirhizotron system to study the interaction of roots of wild cherry trees (Prunus avium L) and pasture in an upland silvopastoral system is described. Operator variation was greatest when distinguishing different tree root categories (e.g. white, brown, woody) but was not significant in relation to total tree or grass root counts or species differences. Analysis of covariance was used to take these differences into account in a field trial using several operators. The seasonal patterns of tree and pasture root growth were different. Tree roots peaked in May before maximal shoot growth. The peak in pasture roots occurred two weeks earlier. Tree height growth was increased by the use of herbicides to control grass growth but this effect was only apparent during August when the soil was dry and when pasture root counts were reduced.     

Development of the IRGA enclosed-chamber system for soil CO<Subscript>2</Subscript> efflux measurement and its application to a spatial variation measurement

A new system was developed for measuring soil CO₂ efflux. The chamber in this system contains a small infrared CO₂ gas analyzer. This system does not need air tubes or pumps for circulating air, so it is expected to offer the advantages of mobility and durability. This system was verified by a comparison with measurements made by using a closed-dynamic-chamber (CDC) system. The spatial variation in the soil CO₂ efflux in a broadleaved deciduous forest was measured using the new system. The soil CO₂ efflux at sampling locations 50–70cm apart varied within a range of 60%–150%. This variation was smaller than the variation due to differences in soil characteristic reflected in different moisture conditions, etc.