摘要:

The experimental use of the relative addition rate as the driving variable for plant nutrition and growth is reviewed with special attention to the theoretical background and the technical and methodological problems. In this technique the culture solution is not a “nutrient solution” in the classical sense, i.e. a solution with a specified initial concentration of nutrient salts. Instead the solution is a carrier of repeatedly added nutrients to the roots. The nutrients are added quantitatively for a specified growth rate and period of time, to permit a steady state relative uptake rate. High accuracy in the control of nutrition and growth has been obtained in solution culture experiments in which the relative addition rate was applied as the treatment variable, when all necessary nutrients were accounted for, when the additions were made very often, and when the culture solution was in darkness and in good physical contact with the roots.

ISSN:0282-7581    

DOI:10.1080/02827588609382436

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The branch biomass of young Scots pines(Pinus sylvestrisL.) was inversely related to the branch number per projected crown area giving greater branch density and smaller branch biomass for narrow crowns than for broad crowns. In particular, in dense stands the small share of branches from the total biomass of narrow‐crowned trees was emphasized. The productivity of narrow crowned trees was, however, smaller than that of trees with broad crowns. The concept of the tree ideotype has been discussed on the basis of theoretical calculations.

ISSN:0282-7581    

DOI:10.1080/02827588609382437

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Root growth capacity (RGC) in Scots pine seedlings was studied from the time of sowing and during the following two growing seasons. The method used for measuring RGC is also described. In the first growing season root growth was intense during the period mid‐July to mid‐September with an earlier peak for early sowing dates. After a period of low growth activity during winter, RGC rose sharply in early spring. During periods of intensive shoot elongation in May and June root growth was depressed. After shoot elongation was completed, RGC rose again before declining during the autumn. During winter and the second growing season, higher RGC levels were obtained for seedlings sown in June compared to the ones sown in April. This result is discussed with regard to differences in cultivation regimes.

ISSN:0282-7581    

DOI:10.1080/02827588609382438

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Altogether 82 plots (261 estimations) ofPicea abies(L.) Karst, and 193 plots (360 estimations) ofPinus sylvestris(L.) stands were estimated by a vertical tube. The “crown free projection”, CFP, of stands thinned in three methods with different thinning grades was measured: unthinned, heavily and very heavily thinned, heavily thinned delayed first thinning, extra heavily thinned and thinned from the top. Basal area (m2ha−1) density (stems ha−1) and diameter sum (m ha−1) were plotted against CFP. Basal area was the best practical measure of stand in this study. Generally Scots pine stands have higher CFP and the curves are steeper than in Norway spruce stands. Depending on the grade of thinning, heavily and very heavily thinned spruce stands, delayed first thinning included, have CFP values of 10–15% and stands thinned from the top, 20–40%, compared with 30–80% and 30–60% respectively in pine stands. Extra heavily thinned stands have the highest CFP, 20–80% in spruce and 50–90% in pine stands. The CFP levels after thinning are too high in pine stands for avoidance of sucker and sprout production of aspen and birch. In dense Norway spruce stands thinned from the top or heavily and very heavily thinned, the CFP values are low enough (≤30%) to diminish the production of suckers.

ISSN:0282-7581    

DOI:10.1080/02827588609382439

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The three‐parameter Weibull function met specified statistical standards for goodness of fit as a model for the diameter distribution of moderately thinned Norway spruce stands in Denmark. Weibull distributions estimated by percentile estimators fit the majority of 522 observed diameter distributions (material made available by the Danish Forest Experiment Station) at the 10% level of significance in the Chi‐square and Kolmogoroff‐Smirnow tests. The Weibull distribution was less suited to describe the diameter distribution in unthinned stands and heavily thinned stands. Weibull parameter predictions were developed and used in connection with a Danish yield table for Norway spruce on clay‐rich coastal soils. The use of the Weibull distribution to predict stem frequencies in different diameter classes before and after a specified thinning of stands is demonstrated.

ISSN:0282-7581    

DOI:10.1080/02827588609382440

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor