The importance of forested mire margin plant communities for the diversity of managed boreal forests in Finland. (Väitöskirja - Dissertation)

Korpela, Leila. 2004
Metsäntutkimuslaitoksen tiedonantoja 935. 60 p. + appendices I - IV.
[ISBN 951-40-1945-8]

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Asiasanat:

biodiversity, vegetation diversity, forest ecology, mire ecology, forest vegetation, mire vegetation, forested peatland, forest drainage, boreal forest, spruce mire, mire margin, species diversity, structural diversity, forest structure

Sisällys:

List of Original Publications

Abstract

Acknowledgements

1. Introduction
1.1. Background
1.2. Concepts of biodiversity
1.3. Importance of forested mire margins for the overall biodiversity
  of boreal forests and mires
1.3.1. Definitions of forested mire margin sites
1.3.2. Special characteristics of forested mire margins - the
  biodiversity viewpoint
1.3.3. Structure and dynamics of the tree stands on forested
  mire margins
1.4. Effect of drainage on the diversity of boreal forests and mires
1.5. Approach and aims of the study

2. Material and methods
2.1. Study area and study sites
2.1.1. Description of the study area
2.1.2. Sample plots
2.1.3. Data collection in the field
2.2. Data analysis
2.2.1. Species (alpha) and community level (beta) diversity analyses
2.2.2. Analysis of structural diversity
2.2.3. Environmental and ecological interpretation of the results

3. Results
3.1. The structure of vegetation and compositional gradients in
  undrained forested mire margin communities
3.2. The diversity of undrained forested mire margin communities
  at the species, community and structural levels
3.3. Effect of drainage on the compositional variation and diversity
  of the understorey vegetation in forested mire margin communities
3.4. Structural diversity of the forested mire margin communities and
  the effect of drainage
3.4.1. Effect of drainage on structural diversity of the understorey
3.4.2. Effect of drainage on the structure of the overstorey
3.4.2.1. Canopy layer structure, species composition and diversity
3.4.2.2. Stand structure

4. Discussion
4.1. Evaluation of the data and methods
4.1.1. NFI-data
4.1.2. Statistical methods
4.1.2.1. Beta-diversity methods
4.1.2.2. Alpha-diversity methods
4.1.2.3. Structural-diversity methods
4.2. The state of forested mire margin communities in relation
  to drainage in Finland
4.3. Importance of forested mire margin vegetation communities
  in maintaining the diversity of managed forests
4.3.1. Community and species level diversity
4.3.2. Changes in structural diversity and species abundances
  of the understorey vegetation
4.3.3. Temporal changes in the structure of understorey
  vegetation of forested mire margin sites
4.4. Structural features of the overstorey of forested mire margins
  that contribute in maintaining the diversity of managed forests
4.4.1. Canopy layer structure, species diversity and composition
4.4.2. Stand structure
4.4.3. Disturbance dynamics, restoration and management from
  the point of view of diversity

5. Concluding remarks

References

Articles I–IV

I Korpela, L. & Reinikainen, A. 1996. Numerical analysis of mire margin forest vegetation in South and Central Finland. Annales Botanici Fennici 3: 183-197.

II Korpela, L. & Reinikainen, A. 1996. Patterns of diversity in boreal mire margin vegetation. Suo - Mires and Peat 47(1): 17-28.

III Korpela, L. 1999. Diversity of vegetation in pristine and drained forested mire margin communities in Finland. International Peat Journal 9: 94-117.

IV Korpela, L. 2004. Structural and species diversity of boreal forested mire margin communities in South and Central Finland– effect of drainage. Silva Fennica (submitted manuscript).

Tiivistelmä:

The study deals with the components and sources of plant diversity in pristine mire margin influenced forested sites and the effects of forest drainage on their diversity pattern. The study focuses on these mire types because (1) their position along the gradients between wetlands and forests results in high diversity, and (2) these sites have been strongly impacted by forest drainage. The study sites consist of paludified mineral soil forest, paludified mire margin forest, and forested spruce and pine mire sites, from the permanent sample plot data of the 8th National Forest Inventory (NFI 8, 1985-1986). The pattern of plant diversity and the effect of forest drainage on it have been approached from two main directions: (1) species diversity, and (2) structural diversity. Species diversity was measured using taxonomic units (species) as alpha- diversity and beta-diversity. The former was understood as species richness in the site (sample plot), and expressed by means of species number and diversity indices. The latter was understood as species diversity along ecological gradients and measured as the length of the gradients, dissimilarity in species composition, and the rate of compositional change along a gradient. Structural diversity, which means the vertical and horizontal architecture of a community, was measured by means of spatial dimensions. The results of this study revealed that species diversity remained relatively high after drainage, but the vegetation composition in the understorey changed towards mineral soil forest vegetation. The most drastic change in the composition and structure of the understorey vegetation after drainage was the clear decrease of Sphagnum species and their replacement by forest bryophytes. Also the structure and composition of the field layer showed increased abundance of the most common forest grasses and mesic forest herbs and forest dwarf-shrubs and by decrease of sedges after drainage. The structure and size distribution of the tree stands on forested mire margin sites remained uneven-aged and uneven-sized after drainage. Drainage changed the tree and shrub species composition and abundance in the different layers more clearly than the tree size distributions. The increased percentage cover of the dominant trees at all fertility levels and the increased percentage cover of deciduous trees, especially that of pubescent birch, were obvious.

Overall, the increase in the diversity indices of the understorey vegetation along the post-drainage succession gradient, as also the increased cover of deciduous trees in the overstorey, was seen to be mostly due to the increased number and cover of pioneer species (e.g. forest herbs, grasses, and bryophytes and pubescent birch in the overstorey), colonist species (e.g. forest dwarf shrubs, and carpet mosses), existing concurrently with decreased covers of mire species. The enrichment of nutrients after drainage caused an initial increase in diversity, but this was seen only as a transient phenomenon in the composition of the community. The drained forested mire margin communities change towards forest vegetation in which mesic and herb-rich forest species dominate but remnants of mire species are still found.

Kommentit

ON-LINE version: ISBN 952-10-2218-3 (PDF-version) TEMPOS project ("Temporal and spatial diversity of boreal forest and peatland vegetation" (2000-2003)


Linkit: METLA Project 3222, METLA Project 3397, Tempos

Yksikkö: Vantaan toimintayksikkö
Hankkeet: Metsä- ja suokasvillisuuden muutokset Suomessa 1950-luvulta nykypäivään, Metsä- ja suokasvillisuus ympäristömuutoksen ilmentäjinä - esitutkimus

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