Kjell Sjöberg

Boreal Forests—The Focal Habitats of Fennoscandia

This chapter deals with the question of maintaining biological diversity in the boreal forests of Fennoscandia, i.e. the Scandinavian Peninsula and Finland. The boreal coniferous forest, or taiga, is the dominant biome, with a latitudinal extension from 56°N to 69°N (Fig. 7.1). The total area of the Fennoscandian forest amounts to more than 50 million ha, of which 13% occurs in Norway, 40% in Finland and 47% in Sweden (Nordic Statistical Secretariat, 1990). Man has utilized the boreal forest, for various purposes, during a very long period of time (Tenow, 1974). However, the most intense utilization has occurred during the last 300 years in connection with the development of the forest industry. At present, Fennoscandian forestry is amongst the most mechanized and efficient in the world. The result is that almost all forest land is now used for production of saw-timber and wood pulp. This has a tremendous impact on the structure and function of the boreal ecosystem. Cutting of old-growth forest and other consequences of forestry have a destructive impact on a large number of boreal organisms, despite the fact that some species are favoured by forest management. The result is decreasing populations for many hundreds of plants and animals, as reflected in recent Red Data lists (Andersson et al., 1987; Ahlen & Tjernberg, 1988; Databanken for hotarer och Naturvardsverket, 1991).

Invertebrate communities in boreal forest canopies as influenced by forestry and lichens with implications for passerine birds

Abstract To investigate the effects of commercial forestry on canopy-living invertebrates in the boreal forest, we sampled branches in northern Sweden for invertebrates and lichens from paired natural spruce Picea abies forests and adjacent managed forests that were selectively logged. The study was conducted during late winter, when invertebrate abundance is lowest, and when small differences may be critical to foraging birds. Natural forests had significantly greater invertebrate diversity than managed forests and nearly five times as many invertebrates per branch. The number of large invertebrates (> 2·5 mm, the minimum prey size for foraging passerine birds) was consistently higher in natural forests, with spiders (Araneae), Lepidoptera and Diptera larvae dominating. The number and biomass of invertebrates were related to the abundance of lichens even after controlling for sampling location and branch size. Other studies have implicated forestry in the decline of non-migratory passerine birds in northern Europe through the destruction and fragmentation of forests, but our study indicates that it may also reduce foraging habitat quality through a reduction in lichen abundance.

Habitat use and spatial patterns of wild boar Sus scrofa (L.): agricultural fields and edges

Rapidly increasing populations of wild boar in Sweden and Europe cause much damage to crops, and there is a critical need for more knowledge about their habitat utilization, especially of agricultural fields. In our study, we first assess the spatial pattern of damage in relation to the edges of agricultural fields. Next, with the aid of global positioning system collars, we studied the pattern of movement of wild boar on agricultural fields. Finally, in order to understand the role of agricultural fields, we studied how habitat selection may vary throughout the year. We found edge effects on damage patterns in agricultural fields. During winter and spring, we found wild boar not only to follow edges, but also to move along narrow landscape elements within agricultural fields. In our habitat analysis, we found strong avoidance of exposed agricultural fields throughout the year, but significantly less when crops are ripe.

Relationships between species number, lake size and resource diversity in assemblages of breeding waterfowl

Breeding waterfowl, habitat diversity and food diversity were studied in 31 boreal lakes in Finland and Sweden. Lakes were 2-48 hectares in size, and had zero to eleven waterfowl species each. In a ...

Ecological effects and management aspects of an exotic tree species: the case of lodgepole pine in Sweden.

The North American tree Pinus contorta var, latifolia was experimentally introduced in Sweden already in the 1920s, and has been used in Swedish forestry on a large scale since the 1970s. These pla ...

The scientific basis for a new and sustainable management of migratory European ducks

Abstract It is an axiom in ecology that knowing the sheer number of individuals in a population is of very little help if the objective is to understand future and past changes in population size. Yet, this is exactly how migratory European ducks are monitored, many of which are important quarry species in several countries. We argue that present monitoring is insufficient to address objectives of wise use andsustainabilitysuchasthoseemphasisedinrecentmanagementdirectivesand multilateral international agreements. The two main problems are the almost total lack of reliable data on recruitment and mortality. We advocate a pan-European monitoring system based on undisputed scientific principles; i.e. a long-term, coordinated and standardised scheme that produces data about vital rates of duck populations as well as about harvest size. Data from such a scheme can be used by game biologists to produce predictive tools, thus providing a functional basis for management decisions for adaptive harvesting and conservation alike.

RESPONSE OF MALLARD DUCKLINGS TO VARIATION IN HABITAT QUALITY: AN EXPERIMENT OF FOOD LIMITATION

Occurrence of Mallard (Anas platyrhynchos) pairs and broods was studied on 86 boreal lakes in two areas in south Finland during 1988-1997 (35 lakes) and 1989-1996 (51 lakes), and field experiments ...

Forest ecosystem research - priorities for Europe.

Abstract European Forest Ecosystem Research Network (EFERN), was set up in 1996 as one result of the Ministerial Conferences on the Protection of European Forests in Strasbourg 1990 and Helsinki 1993 with the aim of promoting ecological research for sustainable forest management. Three plenary meetings were held, each with a specific theme. The results of these meetings have been documented in 10 chapters in a volume with the title ‘Pathways to the wise use of forests in Europe’. The intention was also to give priorities for future forest ecosystem research. In accepting the idea that sustainability includes a multifunctional view of forests, there is a need to find ways of integrating classical forest ecosystem research with biodiversity, water quality and socio-economics. The balancing of the different interests in the forests can be done through planning. From this results also a choice of adequate management methods of the forest resources. The classical stand level in forestry requires now an additional scale — the landscape level. The aim with this paper is to present a concept which attempts to integrate the disciplines involved — ecosystem and landscape ecology and its components. Areas where research efforts are central are also mentioned.

Abundance and species richness patterns of predaceous diving beetles (Coleoptera, Dytiscidae) in Swedish lakes

Abundance and species richness of dytiscid water beetles were estimated with activity traps in ten lakes each in south, central and north Sweden. Partial least square regression models with two significant components explained 76.5% and 55.8% of the total variance in dytiscid abundance and species richness, respectively. For abundance as well as species richness, component 1 had its highest positive loadings for structural complexity of vegetation and abundance of Asellus and Diptera immatures, and high negative loadings for relative shore depth. Component 2 had its highest positive loadings for fish abundance, number of dipterans in emergence traps and relative shore depth, and high negative loadings for lake area. Both the number of dytiscid individuals and species were higher in the northern lakes than in the two other regions. Smaller species were not more abundant in the traps than larger ones. Species mean abundance was positively correlated with number of lakes occupied.

Interspecific interactions and co-existence in dabbling ducks : observations and an experiment

Abstract We studied the possible role of resource limitation and interspecific competition in assemblages of dabbling ducks on breeding lakes in Finland and Sweden with observational and experimental data. After initial vegetation mapping and yearly censuses of ducks in 1985–1990, we collected observational data in 1991–1994 from 28 lakes with natural populations of mallard Anas platyrhynchos and teal A. crecca. Mallard and teal co-occur over vast areas in the Holarctic and they are the only breeding dabbling ducks on many oligotrophic lakes. Both species are migratory in our study regions, teal arriving later in spring than mallards. Log-linear model analysis of observational presence/absence data revealed a positive, not a negative, association between the species. This association was independent of habitat diversity as well as of lake size. Mallard-teal interaction was also studied in a cross-over introduction experiment in 32 other lakes in two years. Wing-clipped mallards were introduced to breeding lakes before the arrival of teal to induce resource limitation and interspecific competition, hypothesized to reduce lake use by teal. The density of mallard pairs on experimental lakes was 2.9–8.0 times higher than on controls, but there was no negative response by teal to the treatment. This is the first combined observational-experimental demonstration of lack of interspecific competition in waterfowl. Our results indicate that heterospecific attraction may affect species co-existence in dabbling ducks.