摘要:

The growth and yield of silver birch (Betula pendulaRoth.), up to the first thinning stage and partly beyond, were studied in four planting design experiments. Stands were established using densities of 400–5000 trees ha−1with even planting and row‐to‐row distances of 3.5 and 5.0 m. The tree quality was not studied but a subsequent study addresses this topic. In the densest birch stands, having 4000 live trees ha−1at a dominant height of 15 m, height and volume increments were observed to begin to slow down. At the age of 20 yrs the highest increment of stem wood was observed at two densities, i.e. 2500 and 5000 trees ha−1. The yield of pulpwood was 20 m3ha−1less with initial spacing of 1600 trees ha‐1 compared with the denser stands. The diameter growth of the dominant trees was reduced when the stem number exceeded 1000 trees ha−1. At the lowest density of 400 trees ha‐1, birch height increment was redued. The skewness value of the diameter distribution was mostly negative. At the first thinning age, the normality of this distribution was reduced by wider spacing. Increasing the row‐to‐row distance did not influence the height growth of silver birch. Using a row‐to‐row distance of 5.0 m, mortality was about twice that found for even spacing at the same density. If the row‐to‐row distance was at least three times that of the plant‐to‐plant distance, the diameter and volume increments were slightly reduced. Extending the row‐to‐row distance hastened the differentiation into distinct canopy layers and the diameter growth of dominant trees suffered less from dense spacing than in even planting. Consequently, the first thinning may be postponed and thereby made economically feasible.

ISSN:0282-7581    

DOI:10.1080/02827589509382890

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The role of stand and site characteristics in a 50‐year‐old, sowed Scots pine(Pinus sylvestrisL.) stand on the decline of Scots pine caused byGremmeniella abietinawas studied. Treewise damage of Scots pine was modelled using stand and site variables and stepwise regression analysis. The significant variables included in the model were stand elevation from the main cold air centre and the pH of the humus layer, while the other less significant variables were the number of stems per hectare of Scots pine and Norway spruce, content of Cu and Ni in the humus layer, and the thickness of the humus layer and the A2horizon. The studied variables excluded from the model were the number of broad‐leaved trees per hectare, Al and Pb contents in the humus layer, and Al, Cu, Pb and Ni contents in the A2horizon. The results strongly suggest that the vicinity of water as well as local depressions act as vulnerable sites for Scots pine and the said vulnerability is enhanced by increased pH of the humus layer.

ISSN:0282-7581    

DOI:10.1080/02827589509382891

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Three field teams undertook a survey of crown transparency in Switzerland in 1993. A fourth team (control) also visited a subset of the trees that had already been visited by the field teams and reported estimates for the same. The problem of estimating the proportion(Pc)of trees with total crown transparency at least equal to a (fixed) levelcis addressed. The method assumes that the control team estimate is an unbiased estimate ofPcand therefore if the expected difference between a field team estimate and the control team estimate is non‐zero then the field team estimate is biased. This assumption is most likely to be met in those countries or areas where the control team consists of the instructors. When this assumption cannot be met, as long as the bias of the control team remains the same over the years, the estimates ofPcfrom different years can still be used to study, for example, whether there is any temporal trend inPc. A weighted average of the bias‐corrected field team estimates is used to determine the confidence limits. The method is applied to the Swiss national forest damage inventory data from the year 1993. The same approach can also be taken for estimating the proportion of cases where a random variableX,qualitative (such as the social position of a tree) or quantitative (such as the diameter of a tree at breast height), assumes values in a particular set.

ISSN:0282-7581    

DOI:10.1080/02827589509382892

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The effect of stump treatment with three different agents (creosote, 10% aqueous solution of sodium nitrite and 20% aqueous solution of urea) on the spread rate of butt rot in Danish permanent forest yield research plots of pure Norway spruce(Picea abies(L.) Karst.) was evaluated. In total, 59 000 stumps from 622 thinnings were used in the calculations. Each thinning was regarded as one observation. To calculate the spread rate of butt rot, the butt rot incidence and possible stump treatment in previous thinnings were used as variables in the subsequent thinnings. If the previous thinning was carried out with urea as the stump treatment agent, the spread rate of butt rot (% year"1) was less than half that of the spread rate if the previous thinning had been carried out without stump treatment, and if the thinning prior to the previous thinning was carried out with urea, the spread rate was less than one‐third. Sodium nitrite also reduced the spread rate of butt rot but was not as effective as urea. Creosote had no effect on the spread rate. Plots on old hardwood forest sites showed a faster development of butt rot than either plots on old field sites or plots on old coniferous forest or old heathland sites.

ISSN:0282-7581    

DOI:10.1080/02827589509382893

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Lepidoptera larvae are important prey for capercaillie chicks{Tetrao urogallus),but utilization varies among habitats. This field experiment investigates the effects of larval feeding behaviour, abundance and the density of bilberry (Vacciniwn myrtillus)on utilization of larvae by a group of four capercaille chicks and also tests whether chick utilization differs between wet and dry coniferous forest. In fenced plots, four hand‐raised chicks were released for a 15 min feeding period. Reduction of geometrid larvae was correlated positively with their abundance but correlated negatively with bilberry density. Geometrids had a much higher predation risk than pyralids and tortricids, probably because they are exposed while feeding, in contrast to pyralids and tortricids. Total reduction of lepidoptera was higher in wet than dry forest, probably due to a higher proportion of geometrid larvae, and lower density of bilberry in the wet forest. The manner of insect feeding and habitat type (e.g. wet and dry forest), which influence bilberry density, therefore may be important factors to consider when assessing or managing habitat quality for capercaillie chicks.

ISSN:0282-7581    

DOI:10.1080/02827589509382894

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The purpose of this study was to compare beta and Weibull distributions in describing basal area diameter distributions in stands dominated by Scots pine and Norway spruce. The material of the study consisted of 535 stands located in eastern Finland. Parameters for both two‐ and three‐parameter approaches of the Weibull distribution were estimated using the method of maximum likelihood. Models for these parameters were derived using regression analysis. For the beta distribution, regression models were formed for the minimum, maximum and standard deviation of diameters within individual stands. These models were used when the exponents of the beta distribution were calculated analytically. Also, some parameter models for beta and Weibull distributions from previous studies were compared with the measured diameter distributions. The distributions obtained were compared using diameter sums and an estimate of the proportion of sawtimber. The results did not reveal any major differences between the suitability of the beta and two‐parameter Weibull distributions. There are appropriate models available for both of the distributions and the more similar the original data is to the data of an application, the better are the results. The two‐parameter approach of the Weibull distribution gave better results than the three‐parameter approach. The poorest results for all the predicted distributions were obtained at the extremes of the distributions.

ISSN:0282-7581    

DOI:10.1080/02827589509382895

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Mean diameter by basal area(dg)is an important stand variable for long‐term economic forecasts of forest holdings. In order to use stand‐by‐stand surveys based on aerial photo interpretation as the data basis for forecasts,dghas to be determined. The objective was to develop and test a regression function fordgin mature stands of Norway spruce(Picea abies(L.) Karst.) and Scots pine(Pinus sylvestrisL.) applicable in southeastern Norway. A study of 700 plots was used to estimate a function fordg. An additive model was found to be most suitable. The independent variables were potential yield capacity, Lorey's mean tree height, crown closure determined by ocular estimation by means of aerial photographs, and the product of potential yield capacity and crown closure. TheR2value was 0.604 and the coefficient of variation was 10.8%. The regression fitted most parts of the calibration data quite well, but it may overestimate the mean diameter in pure spruce stands by 1–2%, and underestimate the diameter in pure pine stands by 3%. For mixed coniferous stands the regression seems satisfactory. Testing by means of an independent data set showed systematic errors of 3–23%. The systematic errors were due partly to calibration problems in connection with the ocular crown closure estimation.

ISSN:0282-7581    

DOI:10.1080/02827589509382896

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Biomass dynamics were studied in isolated relict stands of Scots pine(Pinus sylvestrisL.) on the dry steppe of Kazakhstan (53–54° N), where potential evaporation is 500–600 mm yr−1and the rainfall is 250–260 mm yr−1. Samples were taken from seven plots in natural stands on sandy forest soils (aged 13–110 yrs) and ten plots in plantations on dark‐chestnut‐coloured soils (aged 5–50 yrs). Nine or ten sample trees were taken from each plot, giving a total of 68 and 96 sample trees in natural and plantation stands respectively. Root systems were excavated and fractionated in 11 plots.

ISSN:0282-7581    

DOI:10.1080/02827589509382897

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Seedling seed orchards were established in Sweden with 1112 open pollinated progenies ofPinus contortaDouglasexLoudon plus‐trees, selected from 88 wild stands in western Canada. The progenies were also grown in Swedish test plantations. Breeding values (best linear unbiased predictors) were calculated for tree condition, height, and ramicorn whorl frequency, assessed at ages ranging between 8 and 12 yrs. On the harshest sites, damage caused by weather and fungi, e.g.Gremmeniella abietina,were also evaluated. Categorical data were transformed into values on a normal score scale to improve the efficiency of the evaluation. Breeding values for all assessed traits were combined to form total‐value indices. These indices were then used to guide the genetic thinning of the seed orchards, where single trees were selected from groups of four. The genetic gains resulting from the thinning operations on 1010 of the progenies were estimated to range from 2% for the milder utilization areas to 6% for the harshest. It should be possible to double or triple gains by harvesting seed selectively from the five superior families.

ISSN:0282-7581    

DOI:10.1080/02827589509382898

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Change of stem shape as a result of increased and/or decreased availability of water and mineral nutrients was studied in a Norway spruce(Picea abies(L.) Karst.) stand in southern Sweden. Water availability was correlated inversely with average taper, defined as the ratio between diameter at breast height and height of the tree. When moving from drought via control to irrigation, average taper gradually decreased. Fertilization without irrigation had no influence on average taper. Stem form measurements indicated a decrease in diameter in the upper half of the stems following irrigation, whereas ammonium sulphate application resulted in increased diameter in the upper half of the stems, compared with the control. The results emphasize the necessity of creating stand‐ and treatment‐specific allometric relationships when estimating production in terms of volume or biomass, and of interpreting growth based on basal area with caution.

ISSN:0282-7581    

DOI:10.1080/02827589509382899

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor