Per Angelstam

Reserves, Resilience and Dynamic Landscapes

Abstract In a world increasingly modified by human activities, the conservation of biodiversity is essential as insurance to maintain resilient ecosystems and ensure a sustainable flow of ecosystem goods and services to society. However, existing reserves and national parks are unlikely to incorporate the long-term and large-scale dynamics of ecosystems. Hence, conservation strategies have to actively incorporate the large areas of land that are managed for human use. For ecosystems to reorganize after large-scale natural and human-induced disturbances, spatial resilience in the form of ecological memory is a prerequisite. The ecological memory is composed of the species, interactions and structures that make ecosystem reorganization possible, and its components may be found within disturbed patches as well in the surrounding land-scape. Present static reserves should be complemented with dynamic reserves, such as ecological fallows and dynamic successional reserves, that are part of ecosystem management mimicking natural disturbance regimes at the landscape level.

Predation on ground-nesting birds' nests in relation to predator densities and habitat edge

To study which predators are responsible for nest-losses among ground-nesting birds in boreal forest and how predators utilize different habitats, especially forest/farmland edge, artificial nests were exposed to predators in central Sweden in 1981. A setup which forced nest-robbers to leave foot-prints showed that different avian and mammalian species robbed nests in relation to their relative densities. Among both avian and mammalian nest-robbers there were habitat specialists and generalists. Predators appeared not to develop a memory for the experimental nests. In forest, birds were relatively more common than mammals as nest robbers than in farmland. Differences in the role of different predator species as nest robbers in forest vs. farmland habitats reflected their choice of habitat. No predator seemed to have developed specific nest-robbing skills and loss of individual nests was considered as a random event. Predation rates were higher when nests could be detected from a distance. However, the relevance of the results for real nests remains largely unknown. Variations in predation pressure in relation to different types of ecotones is discussed in view of the recent debate on how patterns of predation become altered as the size of patches of pristine environments are reduced as a consequence of human influences. It is suggested that the main factor affecting the rate of predation in patchy environments is the steepness of productivity gradients between an habitat island and the surrounding matrix rather than patch size itself.

Maintaining and restoring biodiversity in European boreal forests by developing natural disturbance regimes

Abstract. A conceptual model is presented as a guide to the maintenance and restoration of ecologically sustainable boreal forest. The model is based on the hypothesis that self-sustained forest ecosystems can be (re-)created, and their biodiversity developed, if forest management can simulate the composition and structure of boreal forest landscapes by introducing and maintaining disturbances leading to naturally dynamic spatial and temporal patterns of forest regeneration. The major explanatory variable in the model is the effect of wildfire on sites with different fuel characteristics and climates found in the European boreal forest. Four levels of fire intensity are distinguished, based on mean fire frequencies. These range from extremely low in some wet tall-herb sites or sites at high altitudes or latitudes with a humid climate, where fire is absent or rare, to dry lichen-rich sites where fire occurs often. The model is called ASIO, after the words Absent, Seldom, Infrequent and Often, indicating the four levels. Three main disturbance regimes are distinguished in the European boreal forest, based on the complex interactions between probabilistic (e.g. mean fire intervals at different site types) and random events (e.g. where and when a fire occurs): (1) gap-phase Picea abies dynamics; (2) succession from young to old-growth mixed deciduous/coniferous forest; and (3) multi-cohort Pinus sylvestris dynamics. The model stems mainly from studies in Fennoscandia, but some studies from outside this region are reviewed to provide support for a more general application of the model. The model has been implemented in planning systems on the landscape level of several large Swedish forest enterprises, and is also used as an educational tool to help private land owners with the location and realization of forest management regimes. Finally, the model can be used to develop an administrative system for the monitoring of biodiversity in boreal forest.

Role of predation in short-term population fluctuations of some birds and mammals in Fennoscandia

SummaryWe tested the hypothesis that synchronous fluctuations in small game species in boreal Fennoscandia are caused by varying predation pressure. The main prey of predators are the cyclically superabundant voles. Small game species (alternative prey) are rare compared to voles. The following 4 predictions were checked: (1) Predators should shift their diet from main prey to alternative prey as main prey decline. — This was confirmed using data on red fox (Vulpes vulpes L.) diet.; (2) The mortality rate of alternative prey should be inversely correlated to the abundance of main prey. — This was true for mountain hare (Lepus timidus L.) mortality rates and the rate of nest predation on black grouse (Tetrao tetrix L.).; (3) The total consumption of prey by all the predators should at least equal the critical losses in alternative prey during a decline year. — A tentative estimate of predator consumption amounted to 10 times the losses in grouse and hare.; and (4) The absence of synchrony between the species in the boreonemoral region should be associated with a more diverse diet of predators. — This was the case for red fox diets throughout Sweden. Although all 4 predictions were confirmed, we could not necessarily exclude other hypotheses involving changes in quality or quantity of plant food.

Disease Reveals the Predator: Sarcoptic Mange, Red Fox Predation, and Prey Populations

An epizootic of sarcoptic mange was prevalent among Scandinavian red foxes (Vulpes vulpes) during the late 1970s and 1980s. By substantially reducing the population density of foxes, the epizootic created a natural experiment on the importance of fox predation for prey density. The fox population started to recover during the late 1980s. We monitored the populations of the fox and its prey [voles (Cricetidae), mountain hare (Lepus timidus), European hare (L. europaeus), Capercaillie (Tetrao urogallus), Black Grouse (T. tetrix), Hazel Grouse (Bonasa bonasia), and roe deer (Capreolus capreolus)] throughout the event, on a local (101—102 km2), a regional (104 km2), and a national scale. Methods included den counts, snap—trapping, pellet/dropping counts, counts of displaying birds, young/adult ratio from incidental observations of deer, regional questionnaires, and national hunting records. The study revealed red fox predation as a crucial factor in limiting the numbers of hares and grouse as well as fawns per doe of roe deer in autumn, and in conveying the 3—4 yr cyclic fluctuation pattern of voles to small game. The classical view, that predators take but a doomed surplus of their prey, was false for these species in Scandinavia.

Scale Mismatches in Management of Urban Landscapes

Urban landscapes constitute the future environment for most of the worlds human population. An increased understanding of the urbanization process and of the effects of urbanization at multiple scales is, therefore, key to ensuring human well-being. In many conventional natural resource management regimes, incomplete knowledge of ecosystem dynamics and institutional constraints often leads to institutional management frameworks that do not match the scale of ecological patterns and processes. In this paper, we argue that scale mismatches are particularly pronounced in urban landscapes. Urban green spaces provide numerous important ecosystem services to urban citizens, and the management of these urban green spaces, including recognition of scales, is crucial to the well-being of the citizens. From a qualitative study of the current management practices in five urban green spaces within the Greater Stockholm Metropolitan Area, Sweden, we found that 1) several spatial, temporal, and functional scales are recognized, but the cross-scale interactions are often neglected, and 2) spatial and temporal meso-scales are seldom given priority. One potential effect of the neglect of ecological cross-scale interactions in these highly fragmented landscapes is a gradual reduction in the capacity of the ecosystems to provide ecosystem services. Two important strategies for overcoming urban scale mismatches are suggested: 1) development of an integrative view of the whole urban social-ecological landscape, and 2) creation of adaptive governance systems to support practical management.

The effect of matrix on the occurrence of hazel grouse (Bonasa bonasia) in isolated habitat fragments

The aim of this study was to determine the effect of matrix on the occurrence of hazel grouse (Bonasa bonasia) in habitat fragments. The study was conducted in two kinds of landscape: (1) an agricultural landscape, where the censused forest habitat fragments were surrounded by farmland, and (2) in an intensively managed forested landscape, where the censused habitat fragments were surrounded by nonhabitat coniferous forest. Occupied and unoccupied habitat fragments in the agricultural landscape differed significantly in distance to the nearest suitable continuous habitat, with hazel grouse occurring only in habitat fragments closer than 100 m from continuous forest. In the intensively managed forest landscape, the effect of isolation was less evident, but there might be a threshold around 2 km. Effects of isolation occurred over much shorter distances when the surrounding habitats consisted of farmland than when it was forested habitats. The size of the habitat fragments was important in both landscapes, with larger habitat fragments more often containing hazel grouse.

Resilience and vulnerability of northern regions to social and environmental change

Abstract The arctic tundra and boreal forest were once considered the last frontiers on earth because of their vast expanses remote from agricultural land-use change and industrial development. These regions are now, however, experiencing environmental and social changes that are as rapid as those occurring anywhere on earth. This paper summarizes the role of northern regions in the global system and provides a blueprint for assessing the factors that govern their sensitivity to social and environmental change.

Deciduous forest and resident birds: the problem of fragmentation within a coniferous forest landscape

Six species of resident birds were censused in patches of deciduous forest within a coniferous forest landscape in south central Sweden. Here, the forests have been subjected to active forestry for a long time, but with recently increased intensity. Although the forest cover is more or less continuous in this landscape, mature deciduous forest is now a rare element compared with the untouched forest.All censused patches were similar with regards to size, proportion and amount of deciduous trees, but were either isolated in the coniferous forest (‘isolated patches’) or near to other deciduous patches (‘aggregated patches’). We concentrated on six species of resident birds, with moderate area requirements, that are tied to deciduous forest and whose ecology is well-known. The Nuthatch and the Marsh tit, which both show strict year-round territoriality and have a restricted dispersal phase, were significantly more likely to be found in aggregated than in isolated patches. No effect was found for the Great tit and the Blue tit, which are less territorial outside the breeding season and have a longer dispersal phase. Moreover, the Great tit is less specialized on deciduous forest than the other species. Also, the Long-tailed tit was negatively affected by isolation, which may be due to restricted dispersal and to larger area requirements of this flock-territorial species. The Hazel grouse, finally, was not affected, but this larger bird probably uses the forest in a different way from the smaller species.Our study clearly shows that fragmentation of one type of forest (deciduous) within another can have serious detrimental effects on forest-living species and raises important issues for forest management practices and conservation within a forest landscape.

Moose browsing on scots pine in relation to stand size and distance to forest edge

We studied moose (Alces alces (L.)) browsing on Scots pine Pinus sylvestris (L.) in young forest stands of different sizes (1, 10 and >100 ha) and at different distances from old forest edges (5, 20, 100 and 400 m) in single areas in both northern and in soutbern Sweden. In both of our study areas, damage was neither significantly related to stand size nor to distance to edge. In the southern area damage was significantly higher in glades within (<0.1 ha) mature forest than in the young forest stands. However, most of the variation in browsing intensity on pine was due to differences between stands, irrespective of size and distance to forest edge. Using stepwise multiple regressions 30-40% of the variation in damage could be explained (...)