Southern Swedish Forests Research Articles

Did forest fires maintain mixed oak forests in southern Scandinavia? A dendrochronological speculation

In northern Europe, a long history of human exploitation effectively eliminated legacies of natural disturbances in mixed oak forests and we currently lack understanding of the role of natural disturbance factors in affecting oak regeneration into the forest canopies. We compiled dendrochronological, observational and paleochronological data from Southern Sweden to discuss the role of forest fires in oak (Quercus spp.) dynamics. We analyzed oak age structure and its growth dynamics in six southern Swedish forests, which experienced fires between 42 and 158 years prior to our sampling. Extending our analysis over longer time frames, we studied the relationship between sediment charcoal and oak pollen in an area of south-eastern Sweden, where oak has been a common canopy species. In three of the study sites, forest fires resulted in increased oak regeneration. Although fires were generally not associated with a wave of growth releases in surviving trees, the mean basal area growth rate of oaks increased by a range of 108% to 176%, following the fires. The overall pattern indicated that historical fires in oak-dominated forests were of low severity, did not kill canopy oaks, and yet provided a window of regeneration opportunities for that species. Post-fire sprouting of oak and an increase in oak seedling densities following modern prescribed fires are consistent with this explanation. Consistent with this conclusion were significant positive correlations between charcoal concentration and the oak pollen percentage in a site in southeastern Sweden. We discuss the co-occurrence of oak and pine in the historical southern Swedish landscape, as a possible analogy to eastern North American oak-pine forests. Modern conservation policies aimed at the preservation of oak in the southern Swedish landscape should consider the use of low severity fires to maintain natural oak regeneration.

Ash recycling — A method to improve forest production or to restore acidified surface waters?

This cost–benefit analysis compared different strategies for ash recycling in southern Swedish forests, with a special emphasis on the potential to use ash recycling as a measure to ameliorate acidification of soils and surface waters caused by acid deposition. Benefit transfer was used to estimate use values for sport fishing and non-use values in terms of existence values. The results show that the optimal share of acidified forest land that should be treated with ash depends on how optimistic one is about the effect of using ash to restore lakes and streams from acidification. More optimistic assumptions imply that the ash to larger extent should be used to ameliorate acidification. Using the most realistic assumption, given the experiences of forest liming, shows that acidified forest land should not be treated with ash with the aim of restoring lakes and streams from acidification. From a socioeconomic point of view, ash simply does more good as fertilizer on forested organic soils.

Tree species mixtures - a common feature of southern Swedish forests

Summary The proportions of forests in southern Sweden with the most common single or mixed species compositions were determined using the data provided by the Swedish National Forest Inventory. Forests including a second tree species with a basal area of at least 10 per cent, in addition to the most abundant species, were defined as mixed forests. The most common compositions were spruce, pine/spruce, pine and spruce/birch. Overall, mixed forest was more common than single-species forest, and approximately two-thirds of both spruce-dominated and pine-dominated forests included a sufficient proportion of other tree species to be classified as mixed forests, according to the above definition. Differences in composition related to age, site and ownership classes were analysed. Hypotheses that pine/birch mixtures only occur in early-successional stages and that spruce/birch mixtures occur mainly on wet sites were rejected. In fact, 90 per cent of spruce/birch mixtures were found on mesic and moist-mesic sites. The hypothesis that pine/ spruce mixtures are more frequent in private forest was also rejected. In conclusion, the study found high proportions of mixed forest across age and site classes and provides background information for assessing the potential to refine silvicultural methods applicable, e.g., to young spruce/birch or very old pine/spruce stands.

Influence of outdoor recreation on self-rated human health: comparing three categories of Swedish recreationists

This study investigated the relationship between self-rated human health and outdoor recreation, comparing three categories of Swedish outdoor recreationists. Data were obtained from three different surveys, concerning outdoor recreation in all of Sweden, outdoor recreation in southern Swedish forests and hunting in all of Sweden. The influence of outdoor recreation on health was measured by comparing self-rated health in the current situation with a hypothetical situation where the possibility for outdoor recreation was suggested to be removed. The removal resulted in a reduction of average self-rated health in all three samples. The average reduction was significantly different between the samples. The results in this paper suggest that methods usually used in medical research can also be useful in the context of measuring the influence of outdoor recreation on human health.

Should planting of broad-leaved species be encouraged at the expense of spruce? An economic approach to a current southern Swedish forestry issue

Non-timber values of the forest have been subject to much attention in Sweden during the last decades. Of special interest in this respect are the diminishing and species rich broad-leaved forests in southern Sweden. During the late 1900s many of these forests were converted to monocultures of Norway spruce (Picea abies L. Karst.) and other conifers at a high and accelerating pace. While the consequences of this change on biodiversity are currently studied on a broad scale, recreational values, although recognized, have only been subject to a limited number of scientific studies.In the current study, we focused on timber values and recreational values of coniferous and broad-leaved forests in southern Sweden. The first objective was to model the timber value of different management alternatives including spruce or beech (Fagus sylvatica L.) at a typical southern Swedish forest site. The site expectation value for spruce was considerably higher than for beech. The second objective was to include recreational values in monetary terms in the model. The estimated required level of marginal willingness-to-pay for an increase in the area of beech forest in the county of Skåne was very low, indicating that regeneration of beech may be superior to spruce from a socio-economic point of view.

Effect of Reforestation Methods on Pine Weevil (Hylobius abietis) Damage and Seedling Survival

Örlander, G.1 and Nilsson, U. (Swedish University of Agricultural Sciences, The Southern Swedish Forest Research Centre, Asa Forest Research Station, S-360 30 Lammhult, Sweden and Swedish University of Agricultural Sciences, The Southern Swedish Forest Research Centre, Box 49, S-230 53 Alnarp, Sweden). Effect of reforestation methods on pine weevil (Hylobius abietis) damage and seedling survival. Received Feb. 16, 1998. Accepted Sept. 15, 1998. Scand. J. For. Res. 00: 000-000, 199X. Damage to Norway spruce (Picea abies (L.) Karst.) seedlings by the large pine weevil, Hylobius abietis (L.) (Coleoptera: Curculionidae), was monitored in relation to clear - cutting age and silvicultural treatments in southern Sweden. New clear - cuttings were established on four sites during five consecutive years, and seedlings were planted on them from 1989 through 1993. In total, 31 774 seedlings were planted on 20 clear - cuttings. The measures evaluated were seedling insecticide treatment, application of herbicide to ground vegetation, scarification (mound) and planting late in the season. In addition, the effects of slash removal and seedling type were studied. The pine weevil was, by far, the dominant damaging agent. Planting without insecticide or soil treatment on fresh, one- or two - year - old clear - cuttings resulted in a mean level of weevil - caused mortality exceeding 60%. The results indicate that the risk of serious damage by pine weevils remains high until the clear - cuttings reach four or five years of age. Killing the vegetation with herbicide had no effect on pine weevil damage. Slash removal decreased damage on older clear - cuttings, but the effect was small. Scarification (mounding) strongly reduced damage. On fresh clear - cuttings the mean mortality caused by pine weevils in mounded plots was 13%, whereas it was 77% in the controls. The mounding effect varied between sites and clear - cuttings of different ages. Late planting (10 June instead of 1 May) reduced damage on two- and three - year - old clear - cuttings. Three - year - old, bare - rooted seedlings were not damaged as seriously as two - year - old, containerized ones, but the effect was probably due to the larger size of the bare - rooted seedlings. Non - lethal injury resulted in reduced seedling growth. Damage by pine weevils varied between years and within growing seasons. However, on fresh, one- and two - year - old clear - cuttings, damage was severe enough to cause high mortality during all studied years.