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- Hazell, P, et al.
(författare)
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Presence and abundance of four epiphytic bryophytes in relation to density of aspen (Populus tremula) and other stand characteristics
- 1998
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Ingår i: Forest Ecology and Management. - 0378-1127 .- 1872-7042. ; 107:1-3, s. 147-158
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Tidskriftsartikel (refereegranskat)abstract
- The influence of the local density of aspen on the presence and abundance of four epiphytic bryophytes was investigated in four mixed forest stands in Central Sweden, each about 30 ha and aged 70-120 yr. Cover of the bryophytes Nyholmiella obtusifolia, Orthotrichum speciosum, Pylaisia polyantha and Radula complanata (the four most frequent aspen-specific epiphytic bryophytes in this region) was recorded on the bark of 155 systematically sampled aspen stems. In circular plots with 10 m radius surrounding each sampled aspen, information on ground vegetation, soil moisture and stand density was collected. In these plots, and also in plots with 5 m and 20 m radius, stem number and diameters of aspen trees were recorded together with an observation of the presence/absence of the four bryophytes. There was no general and consistent relation between aspen density and presence or abundance of the studied bryophytes. Site, host aspen diameter and forest stand structures were more important for the bryophytes. The site factor explained more of the variation than any of the studied variables. All species except N. obtusifolia were favoured by a large diameter of the host tree, and the density of the surrounding forest stand had a positive effect on the cover of Pyl. polyantha and R. complanata. The practical implications of the results are discussed.
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| 2. |
- Lyytikäinen-Saarenmaa, Päivi, et al.
(författare)
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Monitoring European pine sawfly population densities with pheromone traps in young pine plantations
- 1999
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Ingår i: Forest Ecology and Management. - 0378-1127. ; 124:2-3, s. 113-121
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Tidskriftsartikel (refereegranskat)abstract
- Field trials utilizing pheromone traps were evaluated to develop a population monitoring and predicting system for the European pine sawfly (Neodiprion sertifer). Larval density was censused in a transect across each study site. Three traps per site were baited with 100μg of (2S,3S,7S)-3,7-dimethyl-2-pentadecyl (diprionyl) acetate. During a two-year period traps loaded with 1, 10 and 100 μg of diprionyl acetate were compared. Correlations and coefficients of determination between numbers of captured males and larvae of the same or successive generations were seldom high. Between-generation relationships were significant, when population density was increasing. Having years with increasing densities in a row, the present monitoring method might provide warning of an outbreak.
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