Bjørn Tveite

Radial growth variation of Norway spruce (Picea abies (L.) Karst.) across latitudinal and altitudinal gradients in central and northern Europe

Regional and temporal growth variation of Norway spruce (Picea abies (L.) Karst.) and its dependence on air temperature and precipitation were compared in stands across latitudinal and altitudinal transects in southwestern and eastern Germany, Norway, and Finland. The temporal variation of radial growth was divided into two components: medium- and high-frequency variation, i.e. decadal and year-to-year variation, respectively. The medium-frequency component was rather different between regions, especially the southern and northern ones. However, within each region the medium-frequency growth variation was relatively similar, irrespective of altitudinal and latitudinal differences of the sample sites. A part of the high-frequency variation was common to all four regions, which suggests that some factors synchronising tree growth are common for the entire study area. The high-frequency component of growth was more strongly related to monthly air temperature and precipitation than was the medium-frequency variation. The limiting effect of low temperatures was more significant at northern as well as high-altitude sites, while the importance of precipitation increased in the south and at low altitudes.

Impact of whole-tree harvesting and compensatory fertilization on growth of coniferous thinning stands

Abstract A series of 16 field experiments was established to quantify the growth response of first-thinning stands of Pinus sylvestris and Picea abies to whole-tree harvesting (WTH), and to estimate the need for nutrient compensation. The experiments were undertaken in Finland, Norway and Sweden and represent a wide range of climatic and soil conditions. The biomass and nutrient amounts removed were estimated on the basis of felled sample trees. On average, WTH reduced tree volume growth in both pine and spruce stands (5% and 6%, respectively) during the first 10-year period. The growth reduction was counteracted by fertilization (NPK) and the results indicate that the reduction was an effect of reduced N supply. The inclusion of various site descriptive variables in the linear models did not explain variation in growth response to WTH. Since the growth reductions due to WTH after 10 years were still present, the observation period needs to be extended.

Large-scale climatic variability and radial increment variation of Picea abies (L.) Karst. in central and northern Europe

Abstract. High-frequency variation of Norway spruce radial increment [Picea abies (L.) Karst.] and its dependence on various climatic variables was compared in stands across latitudinal and altitudinal transects in southwestern and eastern Germany, Norway, and Finland. The tested variables included local temperature and precipitation, northern hemisphere temperature anomalies, and the climatic teleconnection patterns (North Atlantic Oscillation, East Atlantic, East Atlantic Jet, East Atlantic/West Russia, and Scandinavian patterns). Climatic impact on radial increment increased towards minimum and maximum values of the long-term temperature and precipitation regimes, i.e. trees growing under average conditions respond less strongly to climatic variation. Increment variation was clearly correlated with temperature. Warm Mays promoted radial increments in all regions. If the long-term average temperature sum at a stand was below 1,200–1,300 degree days, above average summer temperature increased radial increment. In regions with more temperate climate, water availability was also a growth-limiting factor. However, in those cases where absolute precipitation sum was clearly related to radial increment variation, its effect was dependent on temperature-induced water stress. The estimated dates of initiation and cessation of growing season and growing season length were not clearly related to annual radial increment. Significant correlations were found between radial increment and climatic teleconnection indices, especially with the winter, May and August North Atlantic Oscillation indices, but it is not easy to find a physiological interpretation for these findings.

Long-term experiments with acid rain in Norwegian forest ecosystems.

Acid rain is a serious international environmental problem. Scandinavian forests have suffered especially severe damage, and have been the focus of considerable research on the causes and impacts of atmospheric pollution. This book presents the results of long-term studies on acid rain in Norwegian forests. This research examined soil chemistry and biology; the impacts of acid rain on tree growth and nutrition; and its influence on ground vegetation, fungi, and seedling germination and development. Long-Term Experiments with Acid Rain in Norwegian Forest Ecosystems is a lasting contribution to the literature on acid precipitation, and will be of interest to researchers in ecology, air pollution, forestry and environmental chemistry.

Impacts of acid precipitation on coniferous forest ecosystems

This paper summarizes the results from current studies in Norway. One main approach is the application of artificial acid ‘rain’ and of lime to field plots and lysimeters.Application during two growth seasons of 50 mm mo−1 of ‘rain water’ of pH 3 to a podzol soil increased the acidity of the humus and decreased the base saturation. The reduction in base saturation was mainly due to leaching of Ca and Mg.Laboratory experiments revealed that decomposition of pine needles was not affected by any acid ‘rain’ treatment of the field plots. Liming slightly retarded the decomposition.No nitrification occurred in unlimed soils (pH 4.4-4.1). Liming increased nitrification.The soil enchytraeid (Ohgochaeta) fauna was not much affected by the acidification.Germination of spruce seeds in acidified mineral soil was negatively affected when soil pH was 4.0 or lower. Seedling establishment was even more sensitive to increasing soil acidity.Analysis of throughfall and stemflow water in southernmost Norway reveals that the total deposition of H2SO4 beneath spruce and pine is approximately two times the deposition in open terrain. A large part of this increase is probably due to dry deposition. Increased acidity of the rain seems to increase the leaching of cations from the tree crowns.Tree-ring analysis of spruce (Picea abies (L.) Karst.) and pine (Pinus sylvestris L.) has been based on comparisons between regions differently stressed by acid precipitation and also between sites presumed to differ in sensitivity to acidification. No effect that can be related to acid precipitation has yet been detected on diameter growth.

Growth response of coniferous stands to whole‐tree harvesting in early thinnings

A series of 15 field experiments was established to quantify the growth response of first‐thinning stands of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst) to whole‐tree harvesting and to estimate the need for nutrient compensation. The experiments were undertaken in Finland, Norway and Sweden and represent a wide range of site conditions. The site index (H 100) of Scots pine stands varied from 19 to 29 m, and that of Norway spruce stands from 28 to 36 m. Total amounts of biomass and nutrients removed were calculated based on data obtained from felled sample trees. During the first 5‐yr period the growth response to the removal of logging residues varied considerably in both pine and spruce stands. Regression analyses did not reveal any functions that explained the variation in results satisfactorily. In cases where whole‐tree harvesting influenced tree growth negatively, this effect was counteracted by compensatory fertilization. It was concluded that to determine the respons...

Crown Density and Growth Relationships Between Stands of Picea abies in Norway

Relationships between the crown density and growth of Norway spruce (Picea abies L. Karst.) stands are presented, after removal of the effects of major natural influences. Crown density was assessed annually from 1991 to 1996 on 569 monitoring plots comprising 40000 trees. Stand growth was determined from measurements of diameter and height in 1991 and 1996. Various models explaining mean crown density and annual growth of the stands as a function of natural factors, such as age and site index, were compared. The influence of the natural factors was then removed by recalculating crown density to residual values from one preferred model, and by recalculating growth to relative values given as a percentage of model predictions. Crown density and its residuals were positively correlated to growth. These relationships were weak in terms of their ability to explain variation (low R2). However, the various relationships consistently indicated that approximately 1% change in crown density corresponded to 1% change in growth. This relationship also included common spatial variation over Norway: a large part of south - east Norway had unexplained low crown density and unexplained low growth. Some other, smaller regional consistencies were also found. The study supports the use of crown density assessments and encourages the use of growth data in the search for major stress factors responsible for present forest condition.

Discussion and Synthesis

As mentioned in Chapter 1, knowledge of and concern about the effects of acidic rain in Norway go back to the late 1950s and the beginning of the 1960s. However, it was not untill the beginning of the 1970s, after the UN Conference on the Human Environment in Stockholm in 1971, that politicians and the public began showing interest in the problem. At the Stockholm Conference, Svante Oden from Sweden claimed that the soil in Scandinavia was severely acidified by acidic deposition (RMFA, RMA 1971). Norwegian botanists followed up by describing scenarios in which forest production was substantially reduced (Dahl and Skre 1971). The views of these scientists received remarkable attention and, especially in Norway, funds were given to initiate a large project on “Acid precipitation—effect on forest and fish” (The SNSF Project) (Overrein et al. 1980).

Effect of Artificial Rain on Soil Chemical Properties and Forest Growth

Field plots, 150 m2 in size, were watered 27 times, 50 mm each time in the period of July 1973 to September 1978. Groundwater adjusted with sulphuric acid to pH levels of 6, 4, 3, and 2.5, was applied to treatment plots. The experiment was in a homogenous stand of Norway spruce (Picea abies) planted in 1956 on a Cambic Arenosol soil. Tree growth measurements and needle and soil samples have been taken in the period 1973 to 1986. The relatively large changes in soil chemical properties created by applying strong acid to the soil were moderated within a relatively short period after the application of acid was terminated. No effect from the acid treatments were measured on tree height and basal area growth during the watering period. However, negative effects on growth from the acid treatments gradually developed after the watering was stopped. Maximum effects occurred two to five years later. Since then, recovery has been measured. The negative effects are difficult to explain by the nutrient status of the stand as measured by standard foliar analysis. High Al concentrations in the soil solution may have been important.

Effects of Artificial Acid Rain on the Growth and Nutrient Status of Trees

This paper gives results of growth measurements in four field irrigation experiments with artificial acid rain within southern Norway. Foliar analyses were carried out in three of the experiments. Height and diameter growth were stimulated by increased “rain” acidity in a Scots pine sapling stand: The reason for this is probably increased nitrogen uptake from the soil. A beneficial effect of sulphur application either alone, or in combination with increased nitrogen uptake is also possible. In the other experiments no treatment effects on height or diameter growth were found.