| 1. |
- Brunet, Jörg, et al.
(författare)
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Understory succession in post-agricultural oak forests: Habitat fragmentation affects forest specialists and generalists differently
- 2011
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 1872-7042 .- 0378-1127. ; 262:9, s. 1863-1871
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Tidskriftsartikel (refereegranskat)abstract
- The herbaceous understory forms the richest stratum in temperate broadleaved forests in terms of plant diversity. Understanding the process of understory succession is thus of critical importance for the development of management guidelines for biodiversity restoration in post-agricultural plantation forests. We studied effects of stand age, forest fragmentation, and soil and canopy conditions on species richness and abundance of four species groups in the understory of post-arable oak plantations in southern Sweden: herbaceous forest specialists, habitat generalists and open-land species, and woody species. The group of forest specialists may approach the richness of continuously forested sites after 60-80 years in non-fragmented plantations, but many forest species were sensitive to habitat fragmentation. Open-land species richness decreased during succession, while the richness of woody species and of generalists remained stable, and was not affected by fragmentation. Abundance of generalists gradually decreased in non-fragmented plantations, probably due to competition from colonizing forest specialists. Soil pH in post-arable stands remained consistently higher than in continuously forested stands, which maintained differences in species composition. The development of a shrub layer seemed to imply a competitive advantage for forest specialists compared to generalist species. For successful recovery of a rich understory, we suggest that post-arable plantations should be established on loamy soils of intermediate to high pH proximate to older forest with source populations, and that a continuous overstory canopy cover of 70-80% is maintained by regular light thinnings and promotion of a shrub layer. (C) 2011 Elsevier B.V. All rights reserved.
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| 2. |
- Bruun, Hans Henrik, et al.
(författare)
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Post-dispersal seed predation of woody forest species limits recolonization of forest plantations on ex-arable land
- 2010
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Ingår i: Preslia. - 0032-7786. ; 82:3, s. 345-356
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Tidskriftsartikel (refereegranskat)abstract
- Reforestation of ex-arable land in temperate regions increases the area of potential habitat for forest plants. However, the herbaceous plant layer of these plantations contains fewer forest species than comparable plantations at continuously forested sites. One of the reasons for this might be differences in recruitment. The present study addresses post-dispersal seed predation, mainly of woody plants, as the factor limiting the recolonization of young oak plantations in southern Sweden. Our objectives were to investigate differences in dispersal and post-dispersal seed predation between first-generation forest plantations on ex-arable land and re-planted clear-cuts on continuously forested land. There was no recruitment following the experimental sowing of six common woody species (Abuts glutinosa, Betula pendula, Frangula alnus, Sambucus nigra, Sorbus aucuparia and Sorbus intermedia). Thus, the colonization of forest plantations by native shrubs and trees appears to be habitat-limited; the only exception being Rhamnus catharticus, for which poor dispersal ability may be more important. Post-dispersal seed predation of forest shrubs and trees was marked, especially in relatively small and isolated plantations on ex-arable land. There was a high seed predation of Crataegus monogyna, Sorbus aucuparia and Viburnum opulus on ex-arable land, while that of Frangula alnus and Sambucus racemosa was not associated with site placement and land-use history. Seed predation is probably a more important factor limiting restoration of near-natural forests than previously thought.
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| 3. |
- Graae, Bente J., et al.
(författare)
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Germination requirements and seed mass of slow- and fast-colonizing temperate forest herbs along a latitudinal gradient
- 2009
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Ingår i: Écoscience. - : Informa UK Limited. - 1195-6860 .- 2376-7626. ; 16:2, s. 248-257
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Tidskriftsartikel (refereegranskat)abstract
- Predictions on displacement of suitable habitats due to climate change suggest that plant species with poor colonization ability may be unable to move fast enough to match forecasted climate-induced changes in habitat distribution. However, studies on early Holocene plant migration show fast migration of many plant species that are poor colonizers today We hypothesize that warmer temperatures during the early Holocene yielded higher seed quality, contributing to explaining the fast migration. We studied how the 3 seed quality variables, seed mass, germinability, and requirements for break of seed dormancy, vary for seeds of 11 forest herb species with varying colonization capacity collected along a 1400-km latitudinal gradient. Within species, seed mass showed a positive correlation with latitude, whereas germinability was more positively correlated with temperature (growing degree hours obtained at time of seed collection). Only slow-colonizing species increased germinability with temperature, whereas only fast-colonizing species increased germinability with latitude. These interactions were only detectable when analyzing germinability of the seeds, even though this trait and seed mass were correlated. The requirement for dormancy break did not correlate with latitude or temperature. The results indicate that seed development of slow colonizers may be favoured by a warmer climate, which in turn may be important for their migration capacity.
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| 4. |
- Valtinat, Karin
(författare)
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Plant colonization of oak plantations - the interactive effects of local environment and land-use history
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In Europe, only small fragments of deciduous woodlands remain intact and species dependent on this ecosystem have declined. In southern Sweden, a shifting trend during the 20th century, with more afforestations on former arable land, resulted in new oak stands. These new stand are either on former arable fields or on continuously forested land. This thesis has its emphasis on colonization patterns of vascular plants in oak plantations and the interactive effects of local environment and different land-use history. All together 194 species were found in 44 sample plots (12- 80 years). They where groupt according to habitat preferences; true forest species, forest fringe species, semi-natural habitat species i.e. open forest, pastures and meadows, ruderal species and weeds of agricultural fields and indifferent species. Difference between land-uses did not reside in total species number but rather in the species richness of groups with different habitat preference. Many typical forest species were absent from the plantations on former arable sites, especially spring ephemeroids, while weedy species were more abundant on former arable sites. The single most important abiotic environmental factor for colonization was age of the plantation. Stand age appeared to influence all groups. Forest species and forest fringe species increase with age. Weedy and ruderal species are more sensitive to increased vegetation cover and accumulation of a deep litter layer and by that decrease with age. Species predominantly occurring in semi-natural habitats decreased as the environment become increasingly unsuitable with increasing total vegetation cover and accumulation of a litter layer on the forest floor. In situ incubation showed lower NO3- and higher NH4+ mineralization rates in continuously forested land than in former arable fields, mostly at 0-5 cm soil depth. The seasonal variation in N mineralization rates was considerable and the land-uses showed different N mineralization rates for all seasons except the autumn. Lower pH and P, and higher C content, in continuously forested sites were the most obvious differences in soil parameters. Differences in vegetation between sites are related to soil pH and though many true forest species are sensitive to acid conditions these results indicate that oak stands on former fields are potential refuges for acid-sensitive forest plants. Differences between land-use histories were also visible in the spontaneous regeneration after small-scale disturbance. Regeneration in plantations on continuously forested sites was more similar to established vegetation than regeneration in former arable sites. Acer pseudoplatanus was very abundant on continuously forested sites while lacking from sites on former arable land. Quercus robur, had better regeneration on continuously forested sites than on former arable land. In contrast, Fraxinus excelsior, Sambucus nigra and Ulmus glabra were more abundant on former arable. F. excelsior and U. glabra were regarded as indicator species for former arable sites in indicator species analysis. Anemone nemorosa, Deschampsia cespitosa, Oxalis acetosella and Stellaria holostea nearly only occurred on continuously forested sites, while Urtica dioica and Geum urbanum had higher cover in former arable sites. Richness of forest and forest fringe species was higher in plantations adjacent to existing strongly suggests that colonization in oak plantations by forest species are controlled by dispersal limitation. There was the very strong post-dispersal seed predation pressure on seeds of Crataegus monogyna, Frangula alnus, Sambucus racemosa, Sorbus aucuparia and Viburnum opulus and Carex sylvatica, especially in isolated plantations on former arable land. Colonization of recent forest by woody forest species appears to be habitat limited. In conclusion, my results indicate that stand age and distance from existing forest are more important to the number of forest species in new plantations than habitat quality parameters.
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| 5. |
- Valtinat, Karin, et al.
(författare)
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Restoration of oak forest: Effects of former arable land use on soil chemistry and herb layer vegetation
- 2008
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Ingår i: Scandinavian Journal of Forest Research. - : Informa UK Limited. - 0282-7581 .- 1651-1891. ; 23:6, s. 513-521
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Tidskriftsartikel (refereegranskat)abstract
- Stands of pedunculate oak (Quercus robur) planted 50-80 years ago on two types of land (previously forested land and former arable fields) were compared regarding vegetation and soil. Former arable soils were characterized by a higher pH, higher nitrate concentration and higher soil density, but had lower organic matter content and lower ammonium concentration in the topsoil (0-5 cm). These differences, however, decreased with soil depth. Phosphorus concentration was consistently higher in former fields throughout the soil profile (0-45 cm). Nitrogen mineralization, determined by in situ incubation, showed a strong seasonal pattern with peak values in spring. Non-metric multidimensional scaling ordination revealed marked compositional differences in the vegetation between the two land-use categories, and also compositional turnover along gradients in soil pH and nitrogen availability. Differences in soil pH between land-use categories occurred in a range critical for the establishment of many typical forest herb layer species. Plant indicator species were identified for the two land-use categories. The results showed that acid-sensitive forest herbs may benefit from the higher pH soils in new woodlands, in contrast to ancient forest soils with little buffer capacity towards natural and anthropogenic acidification. In conclusion, former arable use has long-lasting effects on soil properties and vegetation composition in broadleaved forests. New woodlands on former fields can thus offer relatively persistent new habitats for acid-sensitive species that have suffered from reduction in habitat area during historic periods of deforestation and cultivation.
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