Torbjörn Josefsson

Long-Term Human Impact and Vegetation Changes in a Boreal Forest Reserve: Implications for the Use of Protected Areas as Ecological References

Northern boreal forest reserves that display no signs of modern forest exploitation are often regarded as pristine and are frequently used as ecological reference areas for conservation and restoration. However, the long-term effects of human utilization of such forests are rarely investigated. Therefore, using both paleoecological and archaeological methods, we analyzed temporal and spatial gradients of long-term human impact in a large old-growth forest reserve in the far north of Sweden, comparing vegetational changes during the last millennium at three sites with different land use histories. Large parts of the forest displayed no visible signs of past human land use, and in an area with no recognized history of human land use the vegetation composition appears to have been relatively stable throughout the studied period. However, at two locations effects of previous land use could be distinguished extending at least four centuries back in time. Long-term, but low-intensity, human land use, including cultivation, reindeer herding and tree cutting, has clearly generated an open forest structure with altered species composition in the field layer at settlement sites and in the surrounding forest. Our analysis shows that past human land use created a persistent legacy that is still visible in the present forest ecosystem. This study highlights the necessity for ecologists to incorporate a historical approach to discern underlying factors that have caused vegetational changes, including past human activity. It also indicates that the intensity and spatial distribution of human land use within the landscape matrices of any forests should be assessed before using them as ecological references. The nomenclature of vascular plants follows Krok and Almquist (Svensk flora. Fanerogamer och ormbunksväxter, 2001).

Influence of habitat history on the distribution of Usnea longissima in boreal Scandinavia: a methodological case study

Changes in habitat affect the distribution of species at different spatial and temporal scales. Our aim was to assess the use of several retrospective methods when determining habitat history and its influence on species distribution, using the pendent lichen Usnea longissima Ach. as a model organism. The study was carried out in a Norway spruce dominated forest, located in the middle boreal zone of northern Sweden. Historical sources (including forest inventories and maps) and dendrochronology were combined with field surveys to determine past stand characteristics with a high spatial precision. Also, present stand characteristics were thoroughly surveyed and the relationship between distribution of U. longissima and past and present habitat characteristics were evaluated. Our results showed that, despite the fact that historical logging was unevenly distributed within the study area, similarities in stand structure exist today. Several essential factors affecting the distribution of U. longissima could be related to changes in past stand structure, especially the extent and intensity of previous logging operations and the subsequent stand development during the last c . 150 years. Our results also showed that U. longissima was favoured by a continuous old age structure with canopy openness preserved. The importance of detailed reconstructions of specific habitat components is highlighted when relating species presence to habitat change. It is suggested that the use of retrospective methods presented in this study can be helpful in clarifying possible causes for the complex distribution of certain organisms.

Indications of shifting cultivation west of the Lapland border: Multifaceted land use in northernmost Sweden since AD 800

Permanent cultivation is generally believed to have been established in the interior of northernmost Fennoscandia later than elsewhere in northern Europe, during or after the late 17th century. Although subtle evidence from various pollen records suggests cultivation may have occurred much earlier in this region, such indications have generally been disregarded. We hypothesized that cultivation was introduced early in the Lapland border zone where western native Sami interacted with coastal farming societies due to the high degree of contact between these communities. Therefore, we investigated historical land usage at three settlement sites in the interior of Sweden’s northernmost territories – two in the Lapland border zone and one in a more westerly traditional Sami area. Analyses of pollen, charcoal and written historical records indicated that cultivation first occurred in AD 800 (700–900) at the westernmost site and one of the border zone sites. Permanent cultivation appears to have been established in c. AD 1480 (1400–1560) and 1750 (1720–1810) in the two Lapland border zone settlements and around AD 1840 (1725–1940) in the westernmost settlement. These results suggest that small-scale shifting cultivation may have been conducted in inland regions of Northern Fennoscandia (including a traditional Sami area) since AD 800. As such, they support the hypothesis that intermittent small-scale cultivation has been going on in these regions for much longer than was previously accepted. Because there was a great mobility of people and ideas across northernmost Fennoscandia, we conclude that the current tendency to describe specific geographical regions as being solely used by ‘nomadic herders’ or ‘permanent farmers’ is inappropriate and fails to capture the complexity of historical land usage.

Intensive land use in the Swedish mountains between AD 800 and 1200 led to deforestation and ecosystem transformation with long-lasting effects

Anthropogenic deforestation has shaped ecosystems worldwide. In subarctic ecosystems, primarily inhabited by native peoples, deforestation is generally considered to be mainly associated with the industrial period. Here we examined mechanisms underlying deforestation a thousand years ago in a high-mountain valley with settlement artifacts located in subarctic Scandinavia. Using the Heureka Forestry Decision Support System, we modeled pre-settlement conditions and effects of tree cutting on forest cover. To examine lack of regeneration and present nutrient status, we analyzed soil nitrogen. We found that tree cutting could have deforested the valley within some hundred years. Overexploitation left the soil depleted beyond the capacity of re-establishment of trees. We suggest that pre-historical deforestation has occurred also in subarctic ecosystems and that ecosystem boundaries were especially vulnerable to this process. This study improves our understanding of mechanisms behind human-induced ecosystem transformations and tree-line changes, and of the concept of wilderness in the Scandinavian mountain range.

Revealing the cultivation history of northernmost Sweden: Evidence from pollen records

Archaeological and historical records suggest that cultivation became established rather late in northern Fennoscandia, preferably in coastal villages of northernmost Sweden during the 14th century. The expansion of these settlements has obliterated the relevant biological archives, thus restricting our ability to conduct palaeoecological studies of the oldest villages and limiting our knowledge of their cultivation history. In a secondary phase, new settlements were established around the periphery of these primary villages. We hypothesize that such secondary villages, which generally are only moderately affected by urban expansion, may function as key sites for vegetation-history studies and that the results can be extrapolated to provide clues about the establishment of primary villages and the initiation of associated permanent cultivations. Analyses of pollen, pollen accumulation rates, charred particles and loss-on-ignition residues from a small lake in the secondary village of Arnemark revealed continuous land use from at least c. 1650 cal. BP (cal. ad 300), a step-up phase in grazing and trampling around 1200 cal. BP (cal. ad 750), and permanent cultivation during the last c. 625 years (cal. ad 1325). The results suggest that the secondary village was established around cal. ad 750, that is, c. 600 years earlier than previously thought and that cultivation here was initiated at the same time as has been suggested for the primary villages by the coast. In this study, we also demonstrate that using pollen from old cereal types as references can make the distinction between cereal and wild-grass pollen more reliable.

Surviving the Winter in Northern Forests: An Experimental Study of Fuelwood Consumption and Living Space in a Sami Tent Hut

Abstract Subsistence in northern regions with cold climate and long winters relies to a large extent on fuelwood access and logistics. The preferred sources of fuelwood in pre-industrial times in northern Scandinavia were dead standing Scots pine trees. To assess historical impacts of Sami settlement sites on surrounding forests, and effects of burning wood on living conditions inside their huts, we burned pine wood in a Sami tent hut during winter, as realistically as possible, then analyzed fuelwood consumption, temperatures, and CO levels inside it. Hourly wood consumption rates ranged from 5.0 to 7.4 kg, corresponding to an estimated average annual consumption of ca. 22,000 kg or 42 m3 per hut. The smoke created by the fire and the low indoor temperature at the periphery of the hut limited the comfortable living space to approximately a third of the total space. We estimate that areas up to 300 m from settlements were used for fuelwood collection, but deliberate, recurring tree girdling to produce snags suitable for fuelwood might have reduced this area. Overall, the landscape impact of settlements was low, affecting less than 2.2% of the utilized lands. We conclude that experimental simulations of historical resource uses can provide valuable quantitative data for verifying or challenging qualitative interpretations and thoroughly modeling human effects on ecosystems over time.

The structure and reproduction of the virgin forest: a review of Eustace Jones (1945)

Abstract Jones (1945) was a milestone paper exploring the natural forest concept with examples from the temperate and boreal ecosystems. It has become a classic because of its use of field observation of regeneration, succession and structure to assess theories about disturbance and the dynamic properties of natural forests. His main aim was to review some of the features of the structure and reproduction of the north temperate virgin forests, and this article presents, discusses and evaluates the main features of this legendary paper. Jones had international experience of both the ecological and silvicultural research communities and combined long-term field observations with theory to develop a realistic assessment of natural forest properties that formed the basis for current understanding. He demonstrated that natural disturbance regimes could generate a variety of structures and that a stable, “climax” forest concept was often not supported by field data. He also showed that even-aged components are common in these forest ecosystems and that the recruitment of tree species proceeds irregularly even in undisturbed stands. His work has influenced subsequent development of related subjects such as disturbance theory, gap-phase dynamics and long-term vegetation changes and has left a legacy with practical relevance for nature conservation and silviculture.