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.

We studied plant survival and colonization over an experimental gradient, from fire lightly scorching the soil to fire consuming most of the organic soil layer, at two forest sites in northern Sweden. The gradient was achieved by adding different amounts of fuel to small plots that were burned in 1988 and 1989. Temperature was recorded at four soil strata during burning. We analyzed survival of seeds and rhizomes in the soil immediately after fire, and followed vegetation cover and seedling establishment until 1993. During fire, there was a steep decline in maximum temperature with increasing depth below the char, irrespective of the depth of burn in the mor layer, indicating that burn depth can be used as a general indicator of heat impact below ground. Lethal temperature was not recorded deeper than 20—30 mm under the burn boundary. Plant survival was determined both by depth of burn and by depth distribution of regenerative structures in the soil. Three rhizomatous species, the dwarf shrubs Vaccinium myrtillus and Vaccinium vitis—idaea and the grass Deschampsia flexuosa, were dominant in the prefire vegetation. For all three species, the bulk of the soil bud bank was located within the mor layer, but was more superficial for D. flexuosa. Initial mortality in the bud bank was progressively higher with increasing depth of burn, and this determined the regrowth over the following years. After fires that consumed only the moss layer, cover of the Vaccinium species returned to prefire levels within 2—4 yr, and D. flexuosa showed a dramatic increase in cover as well as in fruiting. Fires that burned slightly deeper nearly eliminated D. flexuosa, and the deepest burning fires also eliminated Vaccinium spp. In contrast to regrowth from rhizomes, colonization from seed was better after relatively deep—burning fire, both for species with a soil seed bank and for species dispersing seed onto the burnt soil. However, after fires consuming most of the organic soil layer, seed bank species were also badly affected, whereas dispersers showed progressively better establishment with increasing depth of burn. Differences between treatments were still great after 5 yr, indicating that variation in depth of burn will have a long—lasting impact on the vegetation. These results from experimentally burned plots were corroborated by an analysis of depth distribution of viable plant rhizomes and seeds, and the initial colonization at a site newly burned in a wildfire. The precise response patterns of boreal vegetation to variation in burn depth will depend on characteristics of the species present. However, we assume that these results have a high degree of generality, since, in podzolized soils, most rhizomatous species are predominantly located in the mor layer, since the dormant seed bank typically is concentrated at the interface of mor and mineral soil, and also since a thick organic soil layer is a poor seedbed for incoming seeds. The results indicate that in boreal forest, depth of burn is a more important variable than fire fro...

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Past re regimes may indicate under what conditions species have been able to exist in the past, but they do not provide clear and easy answers as to how the boreal landscape should be managed today. First, re regimes have changed considerably over time through the effects of a changing climate, and sometimes even more dramatically through the in uence of humans. Therefore it is unlikely that a close quantitative link exists between re regime and biodiversity. Alternatively, if there is such a link, then biodiversity should have been highly variable in the past, even at the landscape scale. Second, it is impossible to re-enact all re variables within forestry, particularly those operating at the landscape scale. An alternative to the super cial ''emulation'' of the past, which is so often claimed in today's forest management, would be to identify critical processes and habitats at the stand and landscape scale and nd ways to maintain these at suf cient levels. This requires detailed knowledge of the mechanisms involved, and will lead to very different solutions for different groups of species. For example: whereas the highly mobile re-dependent insects can make use of randomly appearing and relatively small burns in the landscape, re-dependent plants are typically seed bankers and require that re returns to the same site within a reasonable time. For these and other more or less ''sessile'' organisms it is vital to designate selected stands and landscapes with long-term plans for the use of re. Without such a long-term commitment to selected localities, much of the unique features associated with re in the boreal landscape will be lost, despite a costly investment in prescribed burning.

Fire, being both a natural and cultural phenomenon, presents problems in disentangling the historical effect of humans from that of climate change. Here, we investigate the potential impact of humans on boreal fire regimes from a perspective of fuels, ignitions and culture. Two ways for a low technology culture to impact the fire regime are as follows: (i) by altering the number of ignitions and their spatial distribution and timing and (ii) by hindering fire spread. Different cultures should be expected to have quite different impacts on the fire regimes. In northern Fennoscandia, there is evidence for fire regime changes associated with the following: a reindeer herding culture associated with few ignitions above the natural; an era of cattle husbandry with dramatically increased ignitions and somewhat higher fire frequency; and a timber exploitation era with decreasing fire sizes and diminishing fire frequency. In other regions of the boreal zone, such schemes can look quite different, but we suggest that a close look at the resource extraction and land use of different cultures should be part of any analysis of past fire regimes.

Abstract. The soil seed bank was investigated in four dry Afromontane forests of Ethiopia. At least 167 plant species were identified in the 0–9 cm soil layer with total densities ranging between 12 300 and 24 000 seeds/m2. Herbs were represented with the largest numbers of species and seeds in the seed bank, while the contribution of tree species was generally low. The overall vertical distribution of seeds was similar at all sites with the highest densities occurring in the upper three cm of soil and gradually decreasing densities with increasing depth. Relatively high densities also occurred in the litter layer. There were large differences in depth distribution between species, suggesting differences in seed longevity. A large number of species in dry Afromontane forests evidently store quantities of seeds in the soil and this is in contrast to the situation in most tropical rain forests, dry lowland forests and savannas, where both the number of seeds and the number of species are relatively small. It is possible that the strongly seasonal and unpredictable climate of this region may have selected for high levels of dormancy, and that herb regeneration is associated with small scale disturbance. The fact that most of the dominant tree species do not accumulate seeds in the soil suggests that their regeneration from seed would be unlikely if mature individuals disappeared. Most tree species have relatively large seeds and poor long‐distance dispersal; this implies that restoration of Afromontane forests after destruction would be difficult. Since there is a diverse seed bank of the ground flora, this component of the vegetation would have a better chance of reestablishing. However, because most cleared forest land is used for agricultural crop production, it is probable that the seed bank will be depleted in only a few years. Therefore, the future of the Afromontane forest flora seems to depend on the successful conservation of the few fragments of remaining natural forest.

Abstract. Analysis of fire statistics revealed that there are steep gradients in the distribution of lightning‐caused fire ignitions in Sweden. The highest ignition density was found in the southeastern provinces of Kalmar and Östergötland, ca. 0.23/10 000 ha/yr. From there, densities generally declined both to the north and to the west, with a density averaging ca. 0.05 in the six northernmost provinces, and an equally low density in the southwestern province of Halland. For both northern and southern Sweden, lightning ignitions peaked in early July, but in the south the season for ignitions started 2–3 weeks earlier and ended 2–3 weeks later. The geographical gradients in lightning ignition density correspond to the average precipitation during summer. The patterns of lightning ignition densities may also indicate gradients in natural fire frequencies. This hypothesis is supported by the distribution of certain fire‐adapted plant species.

Summary1. Forest management involving live tree retention and natural regeneration after cutting is currently increasing in boreal areas. This calls for further analysis of the optimal conditions for seedling establishment from seed following stand disturbances due to logging. 2. We studied post-dispersal predation on seeds and juvenile seedlings of Pinus sylvestris over 3 years in 32 north Swedish boreal forest stands with dierent levels of stand disturbance by logging. The aims were to identify the most important predator species and to quantify the damage in¯icted upon seeds and seedlings in relation to disturbance. 3. In most stands and years, seed predation resulted in <20% seed mortality, although occasionally it reached 60%. Predation on juvenile seedlings ranged from 5% to 100%, with > 70% mortality in 10 cases and < 30% in 44 cases (of a total of 79 observations). 4. The most important seed predators were the carabids Pterostichus oblongopunctatus and Calathus micropterus, and seed predation was correlated with the number of seed-eating carabids caught in pitfall traps. Microtine rodents caused high damage levels only on a single occasion. 5. Logging aected both catches of carabids and seed predation levels, but the relationship between tree stand density and predation was not linear and, generally, seed predation decreased in the order shelterwood > unlogged forest > clear-cut. 6. The most important predator on juvenile seedlings was the slug Arion subfuscus, which attacked seedlings during the ®rst weeks after germination. Pitfall trap catches of Hylobius abietis, which commonly damage planted (1±3-year-old) conifer seedlings, were not related to the levels of seedling predation. 7. Seedling predation was negatively related to stand disturbance, with the highest predation levels by slugs in unlogged forests and the lowest in clear-cuts. Seedling predation was higher in wet than in dry summers, probably because slugs are moisture-limited. 8. There was a large between-site variation in both seed and seedling predation, but predation was not strongly related to forest site types. The fact that predation was strongly aected by logging operations indicates that there may be opportunities to reduce damage through modi®cation of the silvicultural practices.