摘要:

The temporal dynamics and extent of additive genetic control of the ability to produce secondary leader growth (SLG) were examined in aPinus pinaster(Ait.) progeny trial and the benefits of including this binary “trait”; (presence/absence) in a selection scheme for improved height growth were assessed. Trees with SLG had superior height growth, especially at younger ages (< 11 years). An average of 39% of the trees had SLG, but differences between years and families were manifest. The ability to form SLG was under fairly strong additive genetic control(h2= 0.38) compared with the annual height increment (AHI)(h2= 0.17). Trees with SLG in one year were more likely to produce SLG in later years. However, the consistency of producing SLG deteriorated rapidly with time and became nonsignificant after 4–6 years. In young trees (<10 years of age), the frequency of SLG and mean AHI were positively correlated at the family level. In older trees (> 14 years of age), the same correlations were mostly negative. Including occurrence of SLG as an auxiliary selection trait (with zero economic value) in an index with total annual height growth improved overall gain expectations for age 2 to age 22 height growth. However, according to a stochastic risk analysis, the benefit of using occurrence of SLG as an auxiliary trait was more than offset by an unacceptable increase in the standard error of the gain predictions as compared to the gain and associated errors of predicting gain from height growth alone. Stochastically, 10 years of age appears to be the most efficient age for family selections for height growth.

ISSN:0282-7581    

DOI:10.1080/02827589409382836

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Natural regeneration was registered on 97 clear‐felled and scarified sites in northeastern Sweden ten growing seasons after planting. On each site, three fix plots were laid out at planting and the planted seedlings were mapped. Ten years later all healthy non‐planted seedlings were registered in an anulus of size 15.7 m2. Non‐planted seedlings were also observed in four 4 m2squares on each fix‐plot to estimate the zero‐square frequency. Species were classified asPinus sylvestris,L.,Picea abies(L) Karst. and deciduous species(Betula pendulajpubescensRoth./Ehrh.,Populus tremulaL.,Alnus incana(L) Moench.). On average, 7 133 non‐planted seedlings ha‐1were found, of which 29% were conifers. Among the conifers, 71% wereP. abies.More than 2 500 conifer non‐planted seedlings ha‐1were found on 27% of the plots. The number of non‐planted seedlings was correlated to the presence of neighbouring seed‐producing stands within 100 m and decreased with rising altitude.Pinus sylvestrisseedlings were more frequent on dry soils while the deciduous seedlings were more frequent on wet sites. In the 4 m2squares, the zero‐square frequency was 29% if both conifers were and deciduous seedlings were considered and 63% if only conifers were considered. Mean height of the tallest seedling per species and square was 62 cm forP. sylvestris,42 cm forP. abiesand 107 cm for the deciduous seedlings. Key words:Alnus incana, Betula, broad‐leaves, deciduous, Norway spruce, Picea abies, Pinus sylvestris, Populus tremula, reforestation, Scots pine.

ISSN:0282-7581    

DOI:10.1080/02827589409382837

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Nitrogen and phosphorus concentrations were determined for surface peat samples for 78 sites on both undrained and drained pine mires. The oldest areas had been drained 55 years earlier. Generally, the N and P stores in a 0–50 cm peat layer increased with increasing drainage age in oligo‐ombrotrophic sites, and remained unchanged in meso‐oligotrophic sites, even if large quantities were bound up in the increasing tree stand biomasses. This was mainly caused by post‐drainage subsidence of the mire surface and the consequent compaction, which increased the peat bulk densities and brought new stores from deeper peat layers into the layer under observation. Measured stand volumes and published values for N and P concentrations of tree stand compartments were used to estimate the amounts of N and P bound up in the tree stands. The estimates of N and P in the tree stands of the oldest drainage areas were considerable (ca. 400 kg N and 40 kg P ha‐1in the meso‐oligotrophic and ca. 300 kg N and 30 kg P ha‐1in the oligo‐ombrotrophic sites), but were small when compared to the stores in the peat (ca. 10 000 kg N and 400 kg P ha‐1in the meso‐oligotrophic and ca. 7000 kg N and 300 kg P ha‐1in the oligo‐ombrotrophic sites in the 0–50 cm layer).

ISSN:0282-7581    

DOI:10.1080/02827589409382838

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The aim of the study was to address the question of whether shelterwood cutting should be discouraged as a forest regeneration method in Norway spruce(Picea abies(L.) Karst.) forests on highly productive peatlands due to a higher risk of windthrow in such forests. The total extent of windthrow was observed during six years after shelterwood cutting in nine spruce forests on fertile peatlands in north, central and south Sweden. Shelterwoods at densities of 140 and 200 stems ha‐1were studied. At the end of the six year study period, 43% of all trees in the sparser shelterwoods and 38% of the trees in the denser shelterwoods had blown down. With respect to results from recent studies of the development of naturally regenerated and planted seedlings under the shelter trees, the extent of windthrow was regarded acceptable. Analysis of wind data from national weather stations close to the experiments showed that the acceptable extent of windthrow could not be explained by low frequencies of high winds during the shelterwood period. On the contrary, according to the wind observations made at the weather stations selected in central and south Sweden, the annual number of days with high winds (>21 ms‐1) during the six years after the shelter‐wood cutting was larger than the average high wind frequency for the last 40 years. Observations of maximum wind speeds show that the mean annual gale force during the shelterwood period was higher than the long term average. Thus, the results from this study do not justify avoidance of shelterwood cutting in spruce peatland forests because of the risk of windthrow. Each of the shelterwoods in the experiment was located close to a large clearcut, and the shelterwood cuttings were carried out as heavy thinnings. For further reduction of windthrow, denser shelterwoods and no clearcutting in adjacent stands are suggested when using shelterwood systems in practical forestry.

ISSN:0282-7581    

DOI:10.1080/02827589409382839

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Site index was calculated for 66 experimental plantations in western Canada and northern Sweden, containing a wide range ofPinus contortaprovenances drawn from seed lots belonging to the IUFRO international provenance testing program. Growth data from recommended provenances were used to calculate the site index. Site index was defined as predicted average height of the 100 largest trees by diameter ha‐1at age 50.

ISSN:0282-7581    

DOI:10.1080/02827589409382840

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Survival at a mean height of 2.5 m was studied in eight experimental series comprising provenances ofPinus sylvestris(L.). A ninth series of planting experiments was used for verifying functions predicting local provenance survival. The estimated survival of local provenances declined as the temperature sum decreased, with the decline being most rapid close to timberline. Variation in survival within the same climatic region was large, especially in moderately harsh areas. Southward transfer increased survival. Transfer effects differed depending on the temperature sum at the growth site; the greatest effects were found in moderately harsh areas. Altitudinal transfer effects were small and inconsistent. Local provenance survival differed between series. Local provenance survival varied depending on topography and humidity. Transfer effects did not vary between series, nor were they influenced by site factors. Prediction confidence limits were used to estimate the risk for failure of single reforestation attempts.

ISSN:0282-7581    

DOI:10.1080/02827589409382841

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Voles have caused more damage by bark consumption toPicea abiesandPinus contortaseedlings from southern than those from northern origins when planted in northern Scandinavia. In field and laboratory experiments, indigenous Scandinavian tree species from different origins and of various phenological stages were tested for susceptability to vole attacks. Seedlings from northern sites and late phenological stages were most severely attacked by both bank volesClethrionomys glareolusand field volesMicrotus agrestis,while a few aspen clones differed independently of origin. Bark consumption by the two vole species was strongly and negatively related to the concentration of crude fibre in the examined twigs. Bank voles also reacted positively to the content of nitrogen‐free extracts. Differences in preferences for seedlings from different geographical regions appear to result from differences in the bark at the end of growth and in the frost‐hardening process in autumn. Plants transferred northwards probably will not harden in a climatically appropriate way, will contain low concentration of fibre in winter, and will be a preferred food for voles.

ISSN:0282-7581    

DOI:10.1080/02827589409382842

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

By using the approach presented in this paper, the decision‐maker's risk attitude can be ascertained and taken into account in the comparison of reforestation alternatives of a forest stand. Risks which reforestation alternatives include are described using distributions of outcomes. Cardinal utility values of five accumulation points of cumulative distributions of outcomes, calculated without considering risk preferences, are the variables included in a preference function. The parameters of that additive preference function represent the importance of the accumulation points in the choice of the reforestation alternative. They indicate the decision‐maker's attitude towards risk. The parameters are estimated on the basis of pairwise comparisons between the importance of variables, using Saaty's eigenvalue method. Estimation, application, and interpretation of the preference function are simple to carry out, which is important for an approach applied to practical decision‐making. The approach could be applied also, for example, to other forestry decision‐making problems.

ISSN:0282-7581    

DOI:10.1080/02827589409382843

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Chemical properties of the soil water in a clearfelled Norway spruce forest in SW Sweden were monitored using lysimeters during a five‐year period. Measurements were made in plots treated as follows: (i) conventional harvest (CH), with slash and stumps remaining at the site, (ii) whole‐tree harvest (WHT), where only the slash was removed, and (iii) complete‐tree harvest (CTH), where both slash and stumps were harvested. Removal of slash from the clearcutting reduced concentrations of NO3‐, NH4+and K+in soil water below the rooting zone. In plots mechanically disturbed by stump harvesting, NH4+concentrations increased strongly during the first year after felling. High levels were noted for two years, whereafter there was an additional two‐year period with elevated NO3‐concentrations and reduced pH, indicating enhanced nitrification and NO3‐leaching. The nitrate concentration drop coincided with a rapid expansion of the ground vegetation, mainly composed ofDeschampsia flexuosaL. Trin.,Carex piluliferaL. andSeneciospp. In slash‐covered plots, there was a rise in NO3‐concentrations about one year after felling. Within four years all major differences between treatments had disappeared. The possible use of whole‐tree harvesting for reducing NO3‐losses from clearcuttings in areas receiving high atmospheric N loads is discussed.

ISSN:0282-7581    

DOI:10.1080/02827589409382844

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

In conifers the needles are connected to the pith by so‐called needle traces, which elongate in accordance with the thickening of the shoot as long as the needles are alive. This study describes how to determine in retrospect the early foliation of spruce which has already been shed, by means of the needle traces found in the innermost column of the trees. The actual foliation of the main axis and of the branches of young trees showed no significant difference. The number of needle traces in the main axis as compared with the number of needles actually counted on the same segments showed no significant difference either. Therefore, the needle‐trace method appears to be applicable for reconstructing the foliation of old spruce trees retrospectively.

ISSN:0282-7581    

DOI:10.1080/02827589409382845

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor