摘要:

Today the internal structure of a log can be detected using X‐ray scanning technology. The objective of this study was to investigate the potential of grading a log by visual inspection of its longitudinal radiograph image (LRI). The grading accuracy of the LRI method was compared with the accuracy of a conventional manual log grading method. The grading accuracy was expressed as the ability to predict the grade of the centre planks of a log before the log was sawn. The grading results of the LRI method were determined by interviewing respondents connected with the wood and sawmill industry. The statistics of the conventional log grading method originate from the Swedish Stem Bank. The evaluation of the results was based on conventional statistical methods, unpaired significance tests and confidence intervals for means. This study shows that it is possible to grade logs by using LRIs. The grading accuracy is equal to, or better than, conventional log grading done by skilled graders from the Measurement Society of Sweden.

ISSN:0282-7581    

DOI:10.1080/02827589809382965

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This review attempts, from a critical perspective, to put 25 years of satellite remote sensing research into the context of forestry planning. It is limited to temperate and boreal regions and to remote sensing in the visible and near infra‐red spectra. It is structured as follows: firstly, the forestry planning problem is defined and information requirements are identified; secondly, the attempts to use satellite remote sensing as an information source for forestry planning are reviewed, divided into the topics inventory and monitoring; and, finally, the methods for extracting forest information from satellite images are re‐examined, and their inherent limitations and methodological weaknesses are discussed.

ISSN:0282-7581    

DOI:10.1080/02827589809382966

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

It is well known that ozone is detrimental to plants, due to its action as a strong oxidant. Polyamines have been suggested as protecting against oxidative stress, and have been reported as being induced by ozone in plants. However, there is a paucity of data on tree species exposed to ozone for an extended period under field‐like conditions. In the present investigation, mature spruce clones were exposed to ozone (200 or 400 μg m−3air) in open‐top chambers for an entire growth season at two localities in Norway, and levels of the polyamines, putrescine, spermidine and spermine were measured. No consistent effects of ozone fumigation were found on levels of any of the polyamines; not for two clones showing visible injury (yellow needles), and not for four apparently healthy clones. Thus, there was no correlation between sensitivity or tolerance to ozone and polyamine content. However, there were significant differences in polyamine contents between clones and the two localities of exposure.

ISSN:0282-7581    

DOI:10.1080/02827589809382967

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

>Changes in carbon (C) after fire were measured in seven southern boreal upland forest stands during the five immediate post‐fire years and 23 years after the fire. Pre‐fire above‐ground C mass of the stands was estimated. Combustion losses were 19% of the pre‐fire above‐ground C mass (8.4 kg m−2), and an additional 4% of that C mass was lost in the following 3–4 years. After 23 years, neither C mass of understory (0.1 kg m−2) nor standing snags (0.3 kg m−2) differed from that estimated before the fire; tree C was less (2.4 vs. 6.0 kg C m−2), and forest floor (2.5 vs. 1.4 kg C m−2) and coarse woody debris (1.7 vs. 0.7 kg C m−2) C were higher. Above‐ground C mass was 84% of pre‐fire mass. There were no measured changes in surface soil C following the fire (2.9 kg C m−2). Total C mass, including surface soil, was 10.2 kg m−2at 23 years or 91% of the estimated pre‐fire C. Although gross fluxes of C followed the fire, massive net losses of C did not occur either immediately or in the two decades after fire. Dynamics of C differed among the stands. Data from either a single stand or a chronosequence in space can lead to different conclusions than those derived from multiple stands through time.

ISSN:0282-7581    

DOI:10.1080/02827589809382968

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The influence of temperature regime on forest production in the northern boreal forest was studied by analysing the variation in site index for 20 provenance tests of lodgepole pine (Pinus contortaDougl. var.latifoliaEngelm.) in Finland and Sweden with respect to temperature. The site indices were regressed with several different temperature variables, which were obtained from interpolated monthly averages over 30 years from permanent meteorological stations nearby. There were strong correlations between all tested temperature variables and site index (r= 0.80–0.94). Site fertility influenced site index to some extent but the slope of the test sites did not. An increase in temperature sum from 600 to 1200 degree days (corresponding to an increase of the mean temperature in July from 13 to 15°C) was associated with an increase in site index of Scots pine (Pinus sylvestrisL.) from 12.2 to 21.6 m (77%). Such an increase in site index can be assumed to correspond to an increase of 6.5 m3ha−1wood (183%) in mean annual increment. The effect of temperature was greater on poor sites than on fertile sites, and in harsh temperature regimes than in mild.

ISSN:0282-7581    

DOI:10.1080/02827589809382969

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The study reports on the growth of Scots pine (Pinus sylvestrisL.) following the first commercial thinning. The study material consisted of 10 plots, each 1200 m2in area, which were subjected to low‐thinning resulting in varying retention‐stand densities. The post‐thinning diameter growth of the trees correlated positively with the harvested competition and negatively with the retained competition. However, the variables describing removal were not useful model predictors in distance‐dependent single‐tree growth models; the models based on the retained competition only were equally good as models including removal as an additional predictor. In the study thinning response is defined as the change in growth rate as a result of the thinning. The 5‐yr thinning response correlated positively with the harvested competition and negatively with the retained competition, but the correlations were weak. The 5‐yr thinning response did not depend on relative or absolute tree size. Analysis of the temporal distribution of the thinning response revealed that the response was different in different size classes and in different classes of retained and harvested competition. The absolute and relative increase in diameter growth was at its highest among co‐dominant and medium‐sized trees, while the smallest trees were the quickest to respond but demonstrated the lowest total response. The relative change in diameter growth was at its smallest among the largest trees.

ISSN:0282-7581    

DOI:10.1080/02827589809382970

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The effect of the number ofPinus sylvestristrees in seed spots on the growth and external quality of the dominant trees was studied. The trees were monitored during the period between release cutting and the first commercial thinning. The treatments were one, two and four of the tallest seedlings retained per seed spot, and a control. The mean height of the dominant trees was highest in the one‐tree and two‐tree treatments. Diameter at breast height (DBH) increased with increasing spacing. On average, the stump diameter was 1.5–4.7 cm greater in the one‐tree treatment than in the control. Slenderness (height/DBH) was highest in the control treatments. The average living crown limit of the dominant trees was 4.6 m, and was at its highest in the two‐tree treatment. The results indicate that the competition in seed spots decreases the height growth of the dominant trees.

ISSN:0282-7581    

DOI:10.1080/02827589809382971

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The effects on seedling survival and growth of a new scarification method, inverting, were evaluated over 10‐yrs after planting lodgepole pine and Norway spruce on a 2‐yr‐oId clear‐cut in northern Sweden. Inverting, which provides planting spots containing humus turves covered in loose mineral soil without making mounds or ridges, was compared with ploughing, mounding, disc trenching, and no scarification. Subplots with high or low planting positions were used to assess small‐scale topographical effects. For both species, the treatment ranking according to stem volume production after 10‐yrs was inverting>ploughing ≥ mounding = disc trenching > no scarification. Inverting improved seedling height growth by approximately 35% compared with mounding or disc trenching and by more than 100% compared with no scarification. High survival rates were also found following inverting, but only the no‐scarification treatment resulted in a statistically significant reduction in survival rates (ca. 25%) for both species. Further development of the inverting technique might give environmental advantages compared with conventional mechanical site preparation.

ISSN:0282-7581    

DOI:10.1080/02827589809382972

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The spread of discoloration in planted silver birch (Betula pendulaRoth.) stems was investigated in 137 stands in Finland and the role of microbes was investigated in 71 stands. The colour changes noted in the pith of planted silver birches (18–65 years old) were very common but restricted and did not show unacceptable quality or reduction in veneer yield over 30 years. The horizontal spread of discoloration was generally less than 4 cm. The mean vertical spread of pith discoloration in planted silver birch trees was 3.2 m to 5.3 m in 30‐year‐old and younger stems, respectively. Dead and broken branches seem to be the main reason for harmful stem discoloration. The most common microbial community found in discoloured xylem includes primary invaders such as the non‐decaying fungi,Phialophora fastigiata, Phialemonium‐spp. and yeast‐like fungi andEnterobacter‐andPseudomonas‐type bacteria.

ISSN:0282-7581    

DOI:10.1080/02827589809382973

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The impact of plant stress on the occurrence and performance of the gall‐making aphidSacchiphantes abietis(Homoptera: Adelgidae) was investigated by estimating the density and size of galls on experimentally stressed Norway spruce (Picea abies) trees. Plots with 25‐yr‐old spruce trees were treated so as to create a range of stress. Trees were exposed to an untreated control or one of the following five treatments: drought, irrigation, ammonium sulphate addition, nitrogen‐free ("vitality") fertilization and optimum fertilization with irrigation. The occurrence of galls was higher on drought‐stressed trees than on trees in other treatments. Gall size varied continuously among treatments, with the largest galls being found on “vitality"‐fertilized trees and the smallest on drought‐stressed trees. Mechanisms that might explain the inconsistent effects of stress on aphids are discussed. I conclude that plant stress has opposite effects on different life‐stages of this galling insect and possibly on other species of gall‐makers as well.

ISSN:0282-7581    

DOI:10.1080/02827589809382974

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor