Yrjö Norokorpi

Diversity-oriented silviculture in the Boreal Zone of Europe

Abstract This article presents the concepts and models of diversity-oriented silviculture in the Boreal Zone of Europe based on literature, Finnish national forest inventories and field experiment data. The basic idea following the natural processes of forest ecosystems in silvicultural practices has been known since the last century but appropriate comparison materials for modelling have been scanty previously. Stand structure classification used in this study is based on the range and shape of stem distribution. The two main groups are even-sized and uneven-sized. A subclass of the latter, regularly all-sized, with dbh distribution resembling a reversed J, forms the primary basis for treatment models. This kind of structure, following the development and dynamics of natural mixed stands, fulfils the requirements for biodiversity according to international resolutions. Single tree selection and group selection are primarily the main treatments and seed tree and shelterwood cuttings are secondary treatments in diversity-oriented silviculture. In addition, regimes aiming to diversify even-sized stands in different development stages are discussed.

Haloacetic acids, phytotoxic secondary air pollutants

Haloacetic acids are atmospheric oxidation products of airborne C2-halocarbons which are important solvents and propellants. Levels of trichloroacetate (TCA) in conifer needles from mountain ranges in Germany (Black Forest, Erzgebirge) and from two sites in Finland are compared; TCA is present in conifer needles at concentrations up to 0.7 μmol/kg, MCA up to 0.2 μmol/kg. At the Finnish sites, TCA-concentrations and branch degeneration symptoms of Scots pine are correlated. Monochloroacetate (MCA) has been determined in needle samples from Southern Germany in concentrations exceeding its phytotoxicity threshold towards photoautotrophic organisms. Data on atmospheric chloroacetate levels in Germany are also given; ambient air levels of chloroacetic acids range from about 2 pmol/m3 (TCA) to 390 pmol/m3 (MCA). TCA and dichloroacetic acid (DCA) arise from atmospheric oxidation of airborne C2-chlorocarbons, while the source of MCA is not yet known; several tentative pathways are suggested.

The Structure of Advanced Virgin Forests in Finland

The study deals with the structure of advanced virgin forests in Finland based on the national forest inventory carried out in the 1920s. At that time, virgin forests covered 2/3 of the forested area of Finland. Stand structure was described in terms of the d.b.h. distribution. The study material consisting of 10 x 50 m sample plots was grouped according to geographical region, site type and the age class of the overstorey. A stand was classified to be advanced if the age of the overstorey was at least half of the currently applied rotation age and if the stem volume exceeded 40 m3/nectare. About 60% of all virgin forests (i.e. 932 sample plots) were classified to be advanced. In the 1920s. the majority of advanced virgin forests were mixed stands with an all‐sized structure. Trees of small diameter prevailed and the stem number diminished rather steadily with increasing d.b.h. Even‐sized stands with a d.b.h. range of 15 or 20 cm and a normally distributed diameter frequency accounted for only 10 sample...

Trichloroacetic acid (TCA) in pine needles caused by atmospheric emissions of kraft pulp mills

Abstract Trichloroacetic acid (TCA) concentrations in Scots pine needles were determined in the vicinity of two closely situated kraft pulp mills which use C102 as a bleaching agent. TCA in the needle samples was analyzed by the GC/NCI-MS/SIR-method as its methyl ester. TCA levels increased considerably when approaching the pulp mills. TCA may be formed as a degradation product of short chain chlorocarbons, which are volatilized from the spent bleach liquor or it may be released from the spent bleach liquor during the wastewater treatments. The impact of the pulp mill emissions could be observed 60-80 km from the mills downwind. Therefore the emissions of organochloro compounds from pulp mills are important locally, but they may also contribute to the overall organochloro compounds load of the environment.

Trichloroacetic acid in conifer needles and arboreal lichens in forest environments

In the past, trichloroacetic acid (TCA) was a commonly used herbicide, which caused alterations in the properties of surface wax, inhibited growth and caused leaf necrosis. TCA is also a degradation product of short chain chlorocarbons which are used as solvents and degreasers in industry. TCA may also originate from the bleaching of kraft pulp with agents containing chlorine. In this study TCA concentrations in conifer needles were determined in several rural forest areas in subarctic regions in Finland. TCA was analyzed as its methyl ester by GCNCI-MSSIR. The TCA levels in the third-year needles varied in the range 1–180 μg kg−1 (median 23 μg kg−1, n = 130); 90% of the values being between 5 and 70 μg kg−1. No regional concentration trends could be observed. TCA was also present in arboreal lichens of conifers, which is further proof of its atmospheric origin. Comparison of the TCA levels in Usneaceae lichens with lichen biomass gave a significant negative correlation (P = 0.02), whereas TCA concentrations in needles and visible symptoms of tree vitality did not show causal relationships.

Trichloroacetic acid as a phytotoxic air pollutant and the dose-response relationship for defoliation of Scots pine

Various ubiquitous volatile organic air pollutants (VOCs), especially C2-halocarbons, may be converted to secondary air pollutants that are phytotoxic and known as herbicides. One of these is trichloroacetic acid (TCA), found in concentrations ranging from 10 to 130 ng/g in the foliage of forest trees in northern Finland. TCA has been used as a herbicide against monocotyledonous weeds. It has formative effects, inhibits growth, and induces chlorosis and necrosis of light-exposed leaves, including those of woody plant species. Twenty Scots pine trees in an experimental stand 50 km southeast of Rovaniemi were sampled for correlation of TCA levels and needle loss. The trees located at the northwesterly edge of the stand could be divided into two groups, one more resistant to the phytotoxicant TCA than the second. The range of TCA concentrations in needles was 8–65 ng/g. The extent of defoliation (range 25–90%) was lower in the TCA-resistant group, with a gradient of 0.32% defoliation per unit TCA concentration; in the sensitive group, the correlation line had a steeper slope of 0.78% defoliation per unit TCA concentration. These two groups serve as a basis for further studies on morphological, anatomical, and biochemical parameters.

Nitrate reductase activity in some subarctic species and UV influence in the foliage of Betula pendula Roth. seedlings

Nitrate reductase (NR) activity was studied in the foliage of five subarctic species: mature trees of European white birch (Betula pubescens Erch. S.S.), Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies L. Karst), Ericaceous shrub bilberry (Vaccinium myrtillus L.), naturally growing in a forest, and seed-grown silver birch (Betula pendula Roth.) seedlings in an ultraviolet (UV) exclusion field experiment at the Pallas-Ounastunturi National Park in Finnish Lapland (68 degrees N). Mean NR activity ranged from 0 in bilberry to 1477 (S.D. = 277.7) and 1910 (S.D. = 785.4) nmol g(-1) DW h(-1) in mature trees of European white birch and silver birch seedlings, respectively. Significant differences due to UV exclosure treatments were determined for the NR activity of silver birch seedlings (F = 3.62, P= 0.025*) after three growing seasons (191 days) of UV exclusion. The ambient and control silver birch seedlings had or tended to have higher NR activity than those grown under UV exclusion. No relationship was found between the foliage NR activity and total nitrogen content, which ranged from 0.61 to 1.35% per seedling. The present study suggests large differences in NR activity between the species and the induction of NR activity in silver birch seedlings due to ambient UV radiation.

Spatial distribution of dead wood and the occurrence of five saproxylic fungi in old-growth timberline spruce forests in northern Finland

Abstract Adequate understanding of the factors that determine the establishment and survival of dead-wood-dependent species in natural forests is a prerequisite to the successful maintenance of these species in managed forests. This study investigated the factors affecting the occurrence of five wood-inhabiting polypores in old-growth timberline spruce forests in northern Finland, including the substrate availability and the spatial arrangement of large-diameter logs. The volume of coarse woody debris (CWD) varied significantly between the sites (range 15–30 m3 ha−1), large-diameter logs comprising on average 35% of the total CWD volume. However, the within-site variation in CWD volume was 10–15 times larger than the between-site variation. The spatial distribution of large-diameter logs was aggregated or initially aggregated on four sites and random on one site, creating local patches of high CWD volume. An individual target species occurred on average on 8% of all large-diameter logs, and on 11% of optimal logs (as determined by the decay stage). The characteristics of the logs and stand variables explained partly the occurrence of the target species; furthermore, the mortality pattern of trees (stem breakage versus uprooting) and the presence of primary decomposers also significantly affected the occurrence of the target species. The results indicate that besides substrate availability and quality, local habitat factors and species interactions also play a role in the occurrence of wood-inhabiting fungi in boreal timberline forests.