The spatial display of fire over time on the landscape is ecologically important, and spatially explicit analyses offer a possibility of revealing anthropogenic influence on fire regimes. Nonetheless few such analyses have been attempted for longer time frames. We identified past fires in a northern Swedish boreal landscape using fire scars on Pinus sylvestris trees. Within a 19 × 32 km area, local fire chronologies were established at 203 points by cross‐dating fire scars on 1133 wood samples, the earliest dating back to the 1100s. A total of 349 separate fires were identified to location and size. The estimated number of fires per unit area and time (after correcting for varying sample density over time) was relatively constant at 0.095 fires·(104 ha)−1·yr−1 from 1350 to 1650. It increased gradually thereafter, except for a low period in the early 1700s, peaked at 1.17 fires·(104 ha)−1·yr−1 in the mid‐1800s, and then dropped dramatically after 1860. The proportion of the area burned per unit time also increased after 1650, in parallel with the increase in the number of fires (although much less strongly due to a counteracting trend in fire size), from an annual rate of 0.8% prior to 1650 to 2.8% in the mid‐1800s. Prior to 1650, 90% of the total burned area was due to fires larger than 1000 ha, compared to 55% after 1650. This decrease in fire size with increasing number of fires may be an intrinsic property of the system: a negative feedback caused by lack of fuel in early succession. Fire intervals shorter than 15 yr were rare, and there was an increase in the hazard of burning during the first 3–5 decades after fire, suggesting an effect of fuel accumulation. Thus, the proportion of the area burned per unit time does not increase linearly with the number of fires in the landscape, because the probability that fires will stop at boundaries with recently burned areas increases over fires. The changes in the number of fires per unit time mirror changes in the cultural use of the land, i.e., the gradual expansion of permanent settlements in the area after the late 1600s. They are not explained by changes in climate records. This suggests that the increase in fire numbers from the second half of the 1600s represents an increase in anthropogenic fires. Before 1650, the number of fires detected per unit area and time was only marginally different from the present‐day density of lightning ignitions in the region (∼ 0.1 fires·(104 ha)−1·yr−1), whereas during the mid 1800s it was 11.7 times higher. These results show that large alterations in the fire regime can occur without substantial changes in the proportion of area burned per unit time, as exemplified by the trend after 1650, when there were concurrent changes in the number of fires and in average fire size. Therefore, the number of fire events per unit area and time should be an important variable in the analysis of fire history and its underlying causes.

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Summary1. Fires are nowadays small, yet frequent, in temperate Central European conifer forests, but little is known about the fire history in this region. This is likely due to the lack of intact forests that contain old trees and dead wood from which fire history may be reconstructed. An exception is the Białowie_ za Primeval Forest (BPF) in Poland for which we were able to reconstruct the fire history in detail. 2. From 886 tree ring samples collected in a 13-ha conifer-dominated area, we reconstructed fire events and tree establishment back to the mid 1600s. From 1653 to the late 1700s fires were very frequent, with mean point (single tree) fire intervals of 18 years and mean stand scale fire intervals of 6 years. After 1781, the intervals between the fires increased dramatically, and since 1874 no major fire was recorded. 3. Tree establishment underwent substantial changes, closely tracking shifts in fire frequency. When fires were frequent, Pinus sylvestris establishment occurred only sporadically. Later, less frequent fires promoted massive establishment of both P. sylvestris and Picea abies. At present, only P. abies and a few deciduous trees regenerate. 4. Synthesis. We present the first high-resolution fire history in the Central European temperate lowland forest area. The discovery of old P. sylvestris trees and stumps with fire scars in many conifer-dominated parts of BPF show that fire was a major component in the past dynamics of this forest. We also show that historically, fires were recurring at very close intervals, supporting an open, Pinus-dominated forest. These result contrasts with the written history of BPF, which focus on a few, large fires from the past. Human influence on the fire regime was probably substantial, although the disentangling of climatic and human impacts needs further studies. We propose that fire should be increasingly taken into consideration in models of disturbance, vegetation development and forest openness in the whole Central European lowland forest region.

Whereas there is evidence that mixed-species approaches to production forestry in general can provide positive outcomes relative to monocultures, it is less clear to what extent multiple benefits can be derived from specific mixed-species alternatives. To provide such insights requires evaluations of an encompassing suite of ecosystem services, biodiversity, and forest management considerations provided by specific mixtures and monocultures within a region. Here, we conduct such an assessment in Sweden by contrasting even-aged Norway spruce (Piceaabies)-dominated stands, with mixed-species stands of spruce and birch (Betula pendula or B. pubescens), or spruce and Scots pine (Pinussylvestris). By synthesizing the available evidence, we identify positive outcomes from mixtures including increased biodiversity, water quality, esthetic and recreational values, as well as reduced stand vulnerability to pest and pathogen damage. However, some uncertainties and risks were projected to increase, highlighting the importance of conducting comprehensive interdisciplinary evaluations when assessing the pros and cons of mixtures.

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We review species richness in major organism groups, mainly using examples from northern Europe. A high proportion of these species is forest living, and large numbers are dependent on decaying wood. Biodiversity can be assessed at various scales using two different principles. One is to use features, such as ancient and dead trees, known to be important for a large number of species. The other method is to choose species or groups of species known to indicate high biodiversity or presence of many red-listed species. We argue that any serious biodiversity assessment method should include the most species rich organism groups, for example insects. In the present paper we point out the most important features for high biodiversity (old trees and large dead trees), and review the quantities of these features in near-virgin forests. The natural disturbance regime of a region should be the basis for defining a suitable scale and the appropriate features for biodiversity assessment. Possible indicator species for high biodiversity in northern Europe are suggested, based on previous investigations. Among epiphytic lichens and wood-living beetles there are many potentially useful species in addition to vascular plants in the nemoral forest. Among vertebrates, woodpeckers and grouses seem to be the most useful. Validation tests for indicator structures and species are largely lacking but urgently needed. The implications of possible delayed local extinctions are important to bear in mind when managing for sustainable forestry. The knowledge of forest history is useful when developing cost-efficient measures.

Methods: Eight crustose lichen species were surveyed on 165 Quercus robur trees, 17-478 years old, at three study sites. The occurrence patterns of these species were examined at two spatial scales: among trees and within trees. Occurrence patterns within trees were examined in 10 cm × 10 cm plots at all four cardinal aspects at different heights from 0.5 to 4.5 m above the ground.Results: At the tree level, age-related factors were the most important predictors of species occurrence. All species were more frequent on trees > 100 years than on younger trees. At the plot level, the frequency of occurrence increased with increasing bark crevice depth. The frequencies of all study species decreased with increasing cover of bryophytes.Bryophytes were in turn more frequent in plots that were exposed to rainwater and showed a low evaporation rate. Patches most exposed to rainwater were directed upwards, and the lowest evaporation rates occurred on the northern side of the trunks.Conclusions: For many crustose lichens the association with old oak trees seems at least partly to depend on their preference for the deep bark crevices that only occur on old trees. Trees represent epiphyte habitat patches that differ in size due to within-tree variability in habitat quality, such as bark crevice depth and microclimate. This study shows that variability at a finer scale, within habitat patches, contribute to explain species occurrence patterns at habitat patch level.