摘要:

Stem‐unit measurements could be useful for early selection if these dimensions were highly heritable and strongly correlated with traits of commercial interest, such as height growth. Height increments and the number and length of stem segments were mesured in the first and second growth period in predetermined and free growth of Douglas‐fir seedlings from 40 families in each of 2 populations from southwestern Oregon. Populations, or families in populations, exhibited genetic variation in all traits except number of stem units in predetermined growth. Heritabilities for stem‐unit measurements were higher than those for height increment in the first growing season, but not in the second. Correlations among measurements of stem units and height increments were only moderate (generally <0.70). Stem units are not likely to be better measurements of height in early selection of Douglas‐fir than are measurements of either predetermined or free growth.

ISSN:0282-7581    

DOI:10.1080/02827589309382750

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Allozymes of Swedish seed orchard clones of Norway spruce (Picea abiesKarst.) were studied. There were differences between gene frequencies of origins from different regions. The gene pool of the fertilizating pollen of two different orchards was different. Pollen contamination and outcrossing rates were estimated in two seed orchards. The fraction of paternal gametes which did not originate from any seed orchard clone was 10% and 17%, respectively. Based on simulation it was estimated that only a quarter of the gametes with origin outside the orchard would be detected. Estimation of multilocus outcrossing rates were 0.95 and 0.98.

ISSN:0282-7581    

DOI:10.1080/02827589309382751

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The effects of initial spacing and tree class on the basic density of Norway spruce were evaluated in a stand on a fertile site in southwestern Sweden. The basic density at 0 and 4 m above ground level was significantly higher for trees planted with an initial spacing of 1.5 m than for trees planted with wider initial spacings. A decrease in initial square spacing from 2.5 m to 1.5 m had little effect, of small practical importance, on the basic density. The density at 0 and 4 m above ground was significantly higher for the suppressed trees than for the intermediate and dominant ones, and for the intermediate trees compared with the dominant trees. Differences in basic density appeared to be due mainly to differences in growth‐ring width. Basic density decreased outwards from the pith to the bark at 1.3 and 4 m above ground.

ISSN:0282-7581    

DOI:10.1080/02827589309382752

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

An individual tree, process‐based stand growth model is presented. It is based on the carbon balance, according to which tree growth depends on the activities of photosynthesis, respiration and senescence. A simple model is specified for each component of the carbon balance. Next, equations for the tree structure, in which e.g. pipe‐model theory is utilized, are presented. The growth model for dry‐weights of tree compartments based on the carbon balance is transformed using these equations to allow the expression of growth in terms of diameter and height. It is also possible to aggregate a number of physiological and biometrical coefficients into a small number of generalized coefficients of the dimensional growth model. Additional components, including the equations for recession of the crown base and tree survival that are necessary for a stand growth model, are specified. Comparison of the stand growth model with a yield table and a growth model for a sapling stand suggests that the model is capable of accounting for the basic features of stand growth. Furthermore, simulations with varying initial density and some of the model's coefficients indicate that the stand growth model is approximately consistent with the so‐called self‐thinning rule.

ISSN:0282-7581    

DOI:10.1080/02827589309382753

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The capabilities of understorey plant species to indicate site productivity, as expressed by site index (H100), were examined using data from 222 sample plots from mature stands ofPinus sylvestrisL. in southern Finland. The number of herb species was relatively strongly correlated with site index (r=0.81). Also, the presence of 20–30 species indicated site index well. The link between understorey vegetation and site productivity was primarily based on the distribution patterns of these indicators. In contrast, species cover was poorly related to site productivity. In regressions of species cover on site index, only ten species achievedr2of 40% or more. No good indicators existed where site index was less than 21 m. The inclusion of soil deposit types (soil texture) in the prediction model compensated for the poor prediction power of understorey plants on sites of low productivity and increased the accuracy of site productivity estimation by approximately 15%. The estimation did not improve when temperature sum was included in the model.

ISSN:0282-7581    

DOI:10.1080/02827589309382754

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Survival of pine seedlings was studied in a planting trial with special attention paid to damage caused by the pine weevil. The seedlings were checked individually at ten different instances during the five‐year period following planting. The survival data and seedling characteristics were fitted to the nonparametric Cox proportional hazard model. The proportional hazard model is apparently useful in forest regeneration studies, both in analyzing changes in the seedling survival rates, and in predicting consequent survival probabilities over continuous time.

ISSN:0282-7581    

DOI:10.1080/02827589309382755

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Survival and height development of planted Scots pine (Pinus sylvestrisL.) and lodgepole pine (P. contortaDougl. ex Loudon) were followed during a 13‐year period in a soil preparation experiment in northern Sweden. The experiment comprised three soil treatments: no scarification, patching, and mounding. The results indicated that the duration of the positive effects of the soil treatments on survival and height growth was at least 13 years. Mounding resulted in the highest mean heights for both species, but the dominant height for lodgepole pine seemed to be less influenced by the type of soil treatment than seemed the dominant height for Scots pine. No scarification led to significantly higher survival and dominant height for lodgepole pine than for Scots pine. The results do not support the hypothesis that Scots pine saplings run an increased risk of dying when they start emerging above the prevailing snow cover. The reason is probably that the Scots pine provenance used is well adapted to the local conditions.

ISSN:0282-7581    

DOI:10.1080/02827589309382756

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Two coniferous forest drainage areas in central Sweden were partially fertilized with ammonium nitrate and calcium ammonium nitrate respectively, both at a dose of 150 kg N ha‐1. During the following years observations were made on stream water chemistry, invertebrates and brown trout (Salmo truttaL.). Upstream stations were used as controls. Very high concentrations of inorganic N (up to 45 mg l‐1) were recorded immediately after the fertilization. Thereafter, concentration decreased rapidly but remained elevated during the whole study period. Acidity conditions (pH, alkalinity, aluminium) were unaffected by both treatments. The only registered effect on the benthic fauna was a three‐ to five‐fold increase of drifting invertebrates during the first four‐five days after the treatment. However, this did not reduce the population density at the treated stations. No effects on population of trout were recorded.

ISSN:0282-7581    

DOI:10.1080/02827589309382757

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Roots of 4–6‐year old European aspen and pubescent birch were collected monthly during 1983–87 and 1983–88, and analysed to determine their starch, fructose and glucose concentration. Carbohydrate concentrations in aspen roots fluctuated with low levels in May‐June. Seasonal variation was not as consistent in birch roots as in aspen roots. The drop during May‐June occur as consistently in birch. Total carbohydrate concentrations in roots of birch collected from six latitudes (56–67°N) in Sweden showed similar patterns of variation. There were no significant difference between starch concentrations among roots of different diameters (2–11 mm), nor did concentrations differ between sites at different distances (5–25 cm) from the main stem. It was difficult to visually differentiate between low and medium starch levels. Some practical implications of the results are discussed

ISSN:0282-7581    

DOI:10.1080/02827589309382758

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The effect of constant and fluctuating temperatures on germination of Norway spruce (Picea abies(L.) Karst.) seeds collected from three individual trees was tested in darkness using a temperature‐gradient incubator. The germination probability of seeds was modeled between + 6.3 and + 29.1°C. Between minimum (+10°C) and optimum (+21°C) temperatures the probability fit well with a logistic curve reaching 50% germination at + 14.3°C. At temperatures above + 21°C the probability decreased, and the differences between trees were significant. At temperatures between + 10 and + 23°C the day degrees [Snk(T‐ 6°C)] with threshold temperature +6°C predicted germination rate reasonably well. At temperatures above +23°C germination rate was delayed significantly. The temperature fluctuation around mean temperature + 11.6°C did not effect the degree days required for germination. The increasing temperature fluctuation around mean temperature +24.3°C delayed germination. The seeds remaining dormant below and above optimum temperatures germinated after transfer to constant temperature (+ 22°C).

ISSN:0282-7581    

DOI:10.1080/02827589309382759

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor