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1.
《Scandinavian Journal of Forest Research》2012,27(1-4):386-396
The location of Capercaillie lekking sites was compared in forest mosaics of different level of fragmentation. In north Finland the stand characteristics of the lekking sites did not differ from those of randomly selected stands in the 1950s judged from forestry maps and stand registers. In the 1980s, when forestry had considerably altered stand structure, lekking stands were older, larger and had a higher timber volume than random stands. These features evenly changed from the lek centre to the distance of 4 km, to which distance the adjacent areas were assessed. Southern and central Finnish analyses, based on topographic maps, showed that the proportion of forest distinctly decreased with increasing distance from a lek centre, up to a distance of 1–1.5 km. The average patch size of lekking stands were largest in the north (where both cut areas and remaining stands are large) and smallest in central Finland dominated by fine‐grained forest landscape. The results are discussed in terms of landscape ecology and forestry planning. 相似文献
2.
N. T. Donkor R. J. Hudson E. W. Bork D. S. Chanasyk M. A. Naeth 《Journal of Agronomy and Crop Science》2006,192(3):192-200
We conducted a 2‐year study in central Alberta to quantify and simulate the soil water status of boreal grasslands under three grazing systems using wapiti (Cervus elaphus Canadensis), viz. (1) ungrazed control (UNG), (2) high intensity [4.16 animal unit month per ha (AUM) ha?1 ] short‐duration grazing (SDG) and (3) moderate intensity (2.08 AUM ha?1) continuous grazing (CG). Soil water was measured from May 1997 to September 1998 to a depth of 15 cm. Total annual precipitation in 1997 and 1998 was 494 and 429 mm respectively. In both years grazing treatments reduced soil water. Soil water content under SDG was significantly (P < 0.05) lower than CG. Simulation of soil water on each grazing system was conducted using PASTURE, a simple compartmental system dynamics model. Evaluation of the model was conducted using statistical criteria that included calculation of average error, root mean square, coefficient of residual mass and modelling efficiency and comparing these statistics against optimal values. Although the model under‐predicted soil water, simulations of soil water for grazing treatments in both years were closest to measured values with modelling efficiency (how well observed values are close to simulated values) up to 68 %. 相似文献
3.
《Scandinavian Journal of Forest Research》2012,27(1-4):274-283
Published data on the quantities of organic matter in the forest floor (SOMfl) of European forest stands were collated. Studies of SOMfl were included if the total sampled surface was at least 0.15 m2, the surface of a single sample was at least 100 cm2, live material was sorted out, and ash or carbon content was determined. Data from 59 forest stands were compared with regard to stand characteristics and environment. Using a single variable, tree genus was most important for the amount of SOMfl (R 2 adj = 0.34). The amounts in spruce stands (41 × 103 kg ha?1) were significantly higher than those in larch, Douglas fir, oak and birch stands (4–11 × 103 kg ha?1). The best significant multiple model was genus combined with stand age and basal area (R 2 adj. = 0.72). The importance of litter quantity and quality for differentiating the tree genera is discussed. 相似文献
4.
Lennart Hansson 《Landscape Ecology》1994,9(2):105-115
Clearcutting is the main method of harvesting boreal forests, to some extent mimicking natural disturbances by fire and wind-felling. Effects of clearcutting on vertebrate fauna in managed forests was examined by small mammal trapping in spring and autumn, winter censuses of mammal snow tracks and censuses of birds in spring and summer in one central and one edge (125 m) section of large clearcuts and mature forests, respectively. There was a separate clearcut fauna, at least on large clearcuts, that was well distinguished from the forest fauna. There was not any physiognomic ecotone but the forest fauna showed a marked edge effect with larger numbers of many species in the peripheral parts of the forest. In the forests examined, with a Western European bird fauna, there were no typical interior forest species, in contrast to northern taiga forests. The present forest species easily changed distributions seasonally and according to variations in snow conditions and food abundance. Such generalist species in the boreal forest will therefore vary considerably in local density according to landscape composition but will also show large-scale persistence. They may have been selected for as a result of man's restructuring of temperate and boreal landscapes, e.g. by forest management. Edge effects seem to arise for several reasons but will probably only apply to generalist species. 相似文献
5.
《Scandinavian Journal of Forest Research》2012,27(2):152-163
The effects of forest site type and logging intensity on polyporous fungi were studied in subxeric, mesic and herb-rich forests and spruce mires in northern Finland. The species richness of polypores did not follow the fertility gradient of the site types, but was connected with the amount and diversity of coarse woody debris (CWD). The total number of species, and the numbers of indicator and threatened species were equal in subxeric pine forests and in more fertile spruce-dominated stands. The species composition of pine-dominated forests differed conspicuously from that of spruce-dominated site types. The total number of species was not affected by logging intensity, but no virgin forest species or threatened species were found on the sites where the number of cut stumps exceeded 150 stumps ha?1. Increasing logging intensity decreased the number of polypore observations, indicating reduced substrate availability. The results stress the importance of protecting not only fertile spruce-dominated stands, but also poorer, pine-dominated forests, and sites with high and diverse CWD content. 相似文献
6.
《Scandinavian Journal of Forest Research》2012,27(1-4):270-274
Site index was calculated for 66 experimental plantations in western Canada and northern Sweden, containing a wide range of Pinus contorta provenances drawn from seed lots belonging to the IUFRO international provenance testing program. Growth data from recommended provenances were used to calculate the site index. Site index was defined as predicted average height of the 100 largest trees by diameter ha‐1 at age 50. Latitude and altitude explained 56% of site index variation by fitting the function: Site Index (m) = 99.8 ‐ 1.226 ? Latitude (°N) ‐ 0.01205 ? Altitude (m). The site index pattern indicated that forest productivity of the sites investigated decreased approximately by 0.8 m3 ha‐1 yr‐1 per one‐degree latitude northwards and per 100 m increase in altitude. 相似文献
7.
《Scandinavian Journal of Forest Research》2012,27(4):283-288
Aspen (Populus tremula L.) and rowan (Sorbus aucuparia L.) are important for biodiversity conservation and aesthetic reasons. Intensified levels of ungulate browsing the last decades have raised concerns over the recruitment of aspen and rowan in boreal forests. Demographic data are vital to understand and quantify how the structure of tree populations are affected over time by browsing and other factors but such data are rare. In a five-year study, we quantified vital demographic rates for co-occurring aspen and rowan using exclosures in a productive forest area in eastern-central Sweden. Mean annual browsing rate on small (<1 m) aspen and rowan stems was 20 vs. 38%, whereas the order in browsing intensity was reversed for stems of medium (1–2 m) size (28 vs. 14%). Browsing had a clear negative effect on transition rate from small to medium size class in both species, but had a much smaller impact on transition rate from medium to large (2–3 m) size class. Residence time for small stems and regeneration rate was much higher in aspen than in rowan, but browsing did not affect these dynamics. Transition to ungulate safe height (>3 m) was reduced with a factor of two in rowan and four in aspen by browsing. 相似文献
8.
The emulation of natural disturbances such as fire is a prominent harvest management strategy for ecosystems in Canada's boreal forest region, but the effect of harvesting on subsequent lightning fire occurrence has not been studied systematically in the mixedwood boreal forest. We quantified the relationship between annual patterns of lightning fire initiation, forest composition, lightning, and fire weather conditions over eight years (1994–2001) in a 60,000 km2 region of actively harvested mixedwood boreal forest in western Canada. Our analyses illustrated that forest harvesting and burning had opposite effects on subsequent fire initiation, so harvest was not a surrogate for fire. Fire initiation increased in landscapes with more area harvested and decreased with area recently burned. Our data suggested that increased fire initiation was most pronounced in harvested stands up to a decade old, and there was some evidence that the effect might last as long as 30 years. We then used a dynamic fire-succession simulation model to quantify the long-term effects of these fuel-based relationships using two metrics. As expected, the first metric demonstrated that the number of years between disturbances was significantly less in stands that were harvested and then burned, than those that were burned and then burned again. However, the more revealing component of the simulations was an illustration that despite the strong, positive relationship between harvested areas and fire initiation, the area affected over the long-term by a reduced disturbance interval was relatively small. Accordingly, our study shows that spatiotemporal regulation of lightning fire initiation through harvesting activity results in a systematic accelerated frequency of disturbance that is novel to the mixedwood boreal system, but the area affected by these events amount to local peculiarities rather than broad-scaled regularities. 相似文献
9.
Stable carbon and nitrogen isotopic evidence for ecotonal coupling between boreal forests and fishes 总被引:2,自引:0,他引:2
R. L. France 《Ecology of Freshwater Fish》1997,6(2):78-83
Abstract— As a result of water turbulence effects on boundary layer diffusion resistance and carbon isotopic discrimination, the δ13 C values (ratios of 13 C: 12 C) of attached algae may often overlap those of terrestrial plants, thereby making it impossible to distinguish between the relative importance of these two potential food sources for aquatic animals. The present study used a dual isotope approach (δ13 C and δ15 N) to refine measurements of the incorporation of allochthonous organic matter into freshwater fishes. The dependence of five species of littoral fishes on terrestrial detritus for part of their energy sustenance was demonstrated. The littoral zones of boreal Canadian Shield lakes are, therefore, not isolated from their surrounding riparian forests in terms of carbon flow as present day timber management guidelines erroneously assume, but instead exhibit a measurable degree of ecotonal land-water coupling. As a result, clearcut logging of riparian forests to the lakeshore edge, permissible by law in most Canadian provinces containing boreal forests, may have to be reassessed as a forest harvesting strategy. 相似文献
10.
The Swedish tax system affects distribution of forest revenue between national, municipal and individual interests. The study reported here takes a Boreal municipality perspective, with the objective of investigating the tax and investment implications of non-industrial private forestry (NIPF) in a case-study municipality at these three interest levels. Sales revenue, operating costs, investment, disposable income and direct tax revenue generated in NIPF within the boreal municipality are quantified, drawing on income tax return data. The question addressed is, does NIPF contribute to the local economy and thereby to development and maintenance of infrastructure in a typical boreal municipality, given the present NIPF ownership structure and tax system? Results support two different views. On one hand, tax revenues generated from NIPF to the resource municipality amounted to only 17% of the direct tax revenues or less then 1% of the tax revenues in the municipality budget. On the other hand, NIPF owners returned as much as 72% of sales revenue back into their firms in form of operating costs, and 20% in from of investments. 相似文献