摘要:

Open‐pollinated families from 21Pinus sylvestrisL. clones from a seed orchard in central Sweden were cultivated in growth chambers in mineral wool for two growth periods. Two nitrogen treatments were applied: high N availability, free access to all nutrient elements and low N availability aimed at 1/3 of the potential requirement under prevailing external conditions. The second treatment was realized by daily additions of nutrient solution containing nitrogen in amounts adjusted to plant size and actual growth rate. Two types of nitrogen productivity were estimated for plants from the low‐N treatment‐one called nitrogen productivity, expressed per day and based only on the period of the intensive growth during the second growth period, the other, called nitrogen productivity per growth period, based on growth increment during the entire second growth period. Nitrogen productivity varied between 7.8 and 10.3 mg plant DW (mg needle‐N)−1day−1, whereas the nitrogen productivity per growth period varied between 247 and 327 mg plant DW (mg needle‐N)−1(second growth period)−1, and both types showed significant differences between families, with estimated heritabilities of 0.24 and 0.47, respectively. Generally, high N availability resulted in less biomass partitioned to roots, compared with low N availability. There were family differences in growth response to the high N availability. Nitrogen productivity showed moderate and positive genetic correlations with most of the biomass traits, although it was not correlated with the duration of the period of most intensive growth. The results indicate the possibility of maximizing biomas production by breeding for genotypes combining high nitrogen productivity and long growth period.

ISSN:0282-7581    

DOI:10.1080/02827589709355377

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

First‐year seedlings of five latitudinal populations ofAcer platanoideswere subjected to decreasing photoperiod treatment under three different temperature regimes. The depth of the induced dormancy was quantified as the number of days to bud burst (DBB) under defined conditions favourable to growth. The results suggested a close relationship between autumn temperature and the strength of the induced dormancy, with high temperatures combined with short days leading to a deeper stage of dormancy. Northern and continental populations generally had bud burst earlier than southern. The results are discussed in relation to hypotheses for dormancy induction and release.

ISSN:0282-7581    

DOI:10.1080/02827589709355378

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Effects of harvest intensity in thinnings on the productivity of the remaining stands were studied in two Scots pine(Pinus sylvestrisL.) and two Norway spruce(Picea abies(L.) Karst.) stands in Sweden. Treatments were: conventional stem wood harvest with short‐wood system (CH); whole‐tree harvest (WTH); whole‐tree harvest + compensation fertilization with NPK (WTH + F). No significant treatment differences in basal area increment could be detected during the first 10 yrs after harvest. However, in all four stands mean basal area increment was lower on WTH plots than on CH plots. The effects of WTH + F were inconsistent. The results indicate that WTH could be practiced in thinnings without significant short‐term production losses in Scots pine and Norway spruce stands in Sweden. However, it is to early to draw any definite conclusion on long‐term effects of WTH on site productivity.

ISSN:0282-7581    

DOI:10.1080/02827589709355379

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Understorey scarification methods are used to enhance regeneration ofPicea glauca;however, understorey shrubs have been identified as major competitors for regenerating tree species. To investigate the resprouting potential of rhizomes of four boreal forest shrub species in the understorey, rhizome segments (30, 15, and 10 cm in length) ofCorylus cornuta, Cornus stolonifera, Rosa acicularis, andViburnum edulewere planted in five boreal mixed‐wood sites in northern Alberta at four times during the 1994 growing season. Sugar and starch concentrations in rhizome and stem pieces of these shrubs andEpilobium angustifoliumwere determined for each date. The segments and their regrowth were excavated in the autumn of 1995. Rhizome length had no effect on regrowth but there was a marked increase in regrowth for segments planted late in the growing season. The cryptophyte,E. angustifoUum, accumulated large amounts of carbohydrates during the growing season, i.e. 28% of dry weight compared with 6–14% of dry weight for the phanerophytic shrubs. All four shrubs had lowest regrowth when total non‐structural carbohydrate concentrations were at their lowest levels.

ISSN:0282-7581    

DOI:10.1080/02827589709355380

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The moose choice of birch clones was studied by offering nine clones of European white birch plantlets to free‐ranging moose in a field cafeteria experiment. Twig quality, especially the defensive chemical content, affected moose feeding preference. Moose took a bite of larger diameter but tended to consume less from clones with a high phenol content. Moose preferred clones with small current annual shoots and few resin droplets.

ISSN:0282-7581    

DOI:10.1080/02827589709355381

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The colonization of Sitka spruce stumps byHeterobasidion annosum, and the population structure of colonies, was determined 2–3 yrs after inoculation with a 10‐fold dilution series of basidiospore suspensions. Artificially inoculated stumps were infected more frequently than the controls, which received only natural inoculum. The extent of colonization tended to increase with increasing dilution and reached a maximum at the penultimate dilution, but differences were not significant because of large within‐treatment variation. At the higher dilutions stumps fell into poorly‐colonized and heavily‐colonized groups suggesting that some stumps are inhibitory to infection whereas others are extremely susceptible. Colonized areas resulting from the higher dilution treatments tended to comprise fewer larger genets than those from more highly concentrated spore treatments. The results suggest that the success of establishment byH. annosumin basidiospore‐colonized stumps represents the outcome principally of intraspecific competition and the constraints on colonization operating within stumps.

ISSN:0282-7581    

DOI:10.1080/02827589709355382

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

In an attempt to develop a better understanding of the effect of knottiness on the yield of logs for sawn timber products, the present study examines the position and geometrical characteristics of 429 knots found in seven Norway spruce (Picea abies(L.) Karst) middle logs from southern Finland. The raw data used in this study were in the form of coordinates of points located on the knot surface recorded in a cylindrical(R, L, T)reference frame. The data were smoothed using a non linear three‐dimensional model. A curvature analysis of the knot pith was used to differentiate the curved and straight portions of the knots. This analysis made possible calculation of knot angles, symmetry, ovality and volume. The major finding of this study is the uneven distribution of knots around the log circumference. Nearly 50% of the total knot volume was concentrated in one‐third of the log facing the south‐east. Knots were also more prominent in higher portions of the logs studied. These observations support the argument that the uneven distribution of knots offers potential for improving the grade yield of timber sawn from trees harvested in high‐latitude countries.

ISSN:0282-7581    

DOI:10.1080/02827589709355383

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The objective of this investigation was to determine the relationship between potential evaporation, according to the Penman‐Monteith evaporation formula, and measured evaporation in saw timber piles of Scots pine(Pinus sylvestrisL.). The local climate and the water balance of a timber pile were investigated at two geographically different experimental sites, one in southern Norway and one in central Sweden. The results showed that the relationship was significant at both experimental sites, showing a correlation coefficient of 0.71 in Norway and 0.52 in Sweden. At both experimental sites, the potential evaporation had higher average values and between‐day variations than measured evaporation, probably because the Pen‐man‐Monteith formula is too sensitive to variation in meteorological variables. The formula overestimated the evaporation during periods with high evaporation demand, which might be explained by the stronger feed‐back between evaporation and cooling of the air at saw timber piles than at the position of the climate station. A seasonal variation of standard residuals between potential and measured values was observed at both experimental sites. The Penman‐Monteith evaporation formula estimated the evaporation well during July and August, whereas overestimation occurred during June and September.

ISSN:0282-7581    

DOI:10.1080/02827589709355384

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The basic density of pulp wood can be used to convert green volume to dry weight, and as an indicator of the fibre quality. Because the methods for measuring basic density are cumbersome, a practical, on‐line method for sorting Norway spruce pulp wood with respect to basic density was developed. The relationship between mean annual ring width and basic density was used to sort the pulp wood. Brief visual inspection could separate piles of logs with different mean annual ring widths from each other with an acceptable precision. The resulting classes had significantly different mean basic densities (380, 400 and 434 kg m−3). Means of other properties, such as juvenile wood content, heartwood content, and dry matter content, also differed among classes.

ISSN:0282-7581    

DOI:10.1080/02827589709355385

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Today sawmills have started to use automatic methods for log grading. The methods used are either optical or gamma‐ray scanners. However, the signals from these scanners are too coarse for accurate log grading and for good control of the sawing process at the single log level. The objective of the present study was to determine the grading accuracy of a log‐scanner with two industrial X‐ray sources. The grading accuracy was compared with the accuracy of manual grading. The results showed that the manual grading of logs and boards is difficult. The accuracy of manual grading was low and the automatic grading systems were more reliable than manual ones. Possibilities for improving the automatic grading systems are discussed.

ISSN:0282-7581    

DOI:10.1080/02827589709355386

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor