| 1. |
- Eriksson, Ove, et al.
(författare)
-
Land-use history and fragmentation of traditionally managed grasslands in Scandinavia
- 2002
-
Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 13:5, s. 743-748
-
Tidskriftsartikel (refereegranskat)abstract
- Plants associated with traditional agricultural landscapes in northern Europe and Scandinavia are subjected to drastic habitat fragmentation. In this paper we discuss species response to fragmentation, against a background of vegetation and land-use history. Recent evidence suggests that grassland-forest mosaics have been prevalent long before the onset of human agriculture. We suggest that the creation of infield meadows and outland grazing (during the Iron Age) increased the amount and spatial predictability of grasslands, resulting in plant communities with exceptionally high species densities. Thus, distribution of plant species in the present-day landscape reflects historical land-use. This holds also when traditional management has ceased, due to a slow response by many species to abandonment and fragmentation. The distribution patterns are thus not in equilibrium with the present habitat distribution. Fragmentation influences remaining semi-natural grasslands such that species density is likely to decline as a result of local extinctions and invasion by habitat generalists. However, species that for a long time have been subjected to changing mosaic landscapes may be more resistant to fragmentation than is usually believed. Conservation should focus not only on 'hot-spots' with high species richness, but also consider species dynamics in a landscape context.
|
|
| 2. |
- Hedenås, H, et al.
(författare)
-
Spatial distribution of epiphytes on Populus tremula in relation to dispersal mode
- 2003
-
Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 14:2, s. 233-242
-
Tidskriftsartikel (refereegranskat)abstract
- We examined if the spatial distribution of epiphytes in a forest stand differs between two sexually and three asexually dispersed species. As study species we have chosen two sexually dispersed species, the lichen Collema curtisporum and the bryophyte Orthotrichum speciosum, and three asexually dispersed species, the lichens C. furfuraceum and Leptogium saturninum and the bryophyte O. obtusifolium. All of these species grow on Populus tremula. In P. tremula stands, individual trees may be regarded as distinct patches for the studied species, while the stand represents a 'landscape" of discrete patches. The study was performed in two relatively homogeneous forest stands. The study revealed that the asexually dispersed species were more common than the sexually dispersed. It was also shown that the sexually dispersed species were more aggregated than P. tremula in both stands. In contrast, the distribution of the asexually dispersed species mirrors, more or less, the distribution of their host, i.e. the spatial pattern shown by P. tremula. It is unlikely that the measured environmental variables strongly influenced the observed spatial distribution. Thus, we suggest that the different dispersal and establishment strategies were important in shaping the local distribution of the species.
|
|
| 3. |
- Berglund, Håkan, et al.
(författare)
-
Predictability of plant and fungal species richness of old-growth boreal forest islands
- 2001
-
Ingår i: Journal of Vegetation Science. - 1100-9233 .- 1654-1103. ; 12:6, s. 857-866
-
Tidskriftsartikel (refereegranskat)abstract
- The fragmentation and deterioration of old-growth forest habitat by modern forestry have become a major threat to species diversity in Fennoscandia. In order to develop a conservation strategy for the remaining diversity it is essential to identify the existing diversity and to develop appropriate conservation and monitoring programs. For these purposes indicators of conservation value for administrative prioritization are required. This study examines the predictability of plant and fungal species richness on two spatial scales on 46 isolated old-growth forest islands (0.17-12 ha) in a forest-wetland mosaic. We explore (1) to what extent area, isolation and stand structure variables can explain the variation in species richness and (2) if richness patterns of individual species groups correlate. Isolation showed no relation to species richness. Area explained 50-70% of the variation in total species richness and was positively related to the density of crustose lichens and Red-list species in island interiors. Stand structure variables explained 28-66% of the residual variation in total species richness after controlling for island size, and 15-73% of the variation in density of species in island interiors. The highest predictability of species richness was found among substrate-specific fungi and Red-list species. Different stand structure variables were found to explain richness in the different species groups, and only among a few species groups species richness correlated. Thus, species richness of one single species group is unlikely to be a good indicator for total biodiversity. The results show that measurements of stand size and stand structure variables may be a strong complementary tool. and sometimes a substitute to extensive species inventories when one aims to estimate and monitor plant and fungal species diversity in old-growth Picea abies forests.
|
|
| 4. |
- Dai, Xiaobing
(författare)
-
Impact of cattle dung deposition on the distribution pattern of plant species in an alvar limestone grassland
- 2000
-
Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 11:5, s. 715-724
-
Tidskriftsartikel (refereegranskat)abstract
- Seed banks in cattle dung, soil under cattle dung and soil under vegetation and growth response of plant species to the changes in soil nitrogen availability were studied in an alvar limestone grassland on Öland, Sweden, in order to analyse the impact of dung deposition and decomposition on the formation of patches of plant species. Results suggest that patches of four plant species could result from cattle dung deposition and decomposition. Impact of dung could proceed in three ways: (1) by changing the relative abundance of species in the soil seed bank under dung, and/or (2) by influencing the deposition of seeds in the dung, and/or (3) by intensifying the growth of some species through nutrient release. Species patches could result from one or more of these aspects. For instance, patches of Arenaria serpyllifolia may be induced by dung deposition because of the dominance of its seeds in dung, while the pattern of Cerastium semidecandrum and Festuca ovina may be due to the abundance of their seeds in the soil seed bank under dung and their positive growth response to increased nitrogen availability.
|
|
| 5. |
- Edman, Mattias, et al.
(författare)
-
Spatial pattern of downed logs and wood-living fungi in an old-growth spruce forest
- 2001
-
Ingår i: Journal of Vegetation Science. - 1100-9233 .- 1654-1103. ; 12:5, s. 609-620
-
Tidskriftsartikel (refereegranskat)abstract
- Since many wood-living forest species are influenced by the dynamics of coarse woody debris (CWD), information about the spatial pattern of CWD under natural conditions is essential to understand species distributions. In this study we examined the spatial pattern of downed logs and wood-decaying fungi in an old-growth boreal Picea abies forest in northwestern Sweden that is governed by gap-phase dynamics. The spatial pattern of wood-decaying fungi was studied to draw conclusions about species dispersal abilities. A total of 684 logs with a diameter 10 cm were mapped and analysed with Ripley's K-function. The distribution of all logs taken together displayed a significant aggregated pattern up to 45 m. The different decay stages also deviated from random expectations. Fairly fresh logs and logs in the middle decay stage were clumped up to about 25 and 35 m respectively, and late decayed logs aggregated up to 95 m. Logs with diameters from 10-29 cm were aggregated up to 25 m, whereas logs ≥30 cm diameter were randomly distributed. The result suggests that gap-dynamics do have an impact on the spatial pattern of the CWD, creating fine-scale clumping. The random distribution of large logs may result from the slightly regular spacing of large living trees. The spatial patterns of 16 species (n 20) of wood-decaying fungi were analysed with Ripley's K-function. Three patterns were aggregated, for Gloeophyllum sepiarium, Coniophora olivacea and Vesiculomyces citrinus. These results indicate that the distribution of most species at the stand level is generally not influenced by dispersal limitations.
|
|
| 6. |
- Gunnarsson, Urban, et al.
(författare)
-
Diversity and pH changes after 50 years on the boreal mire Skattlosbergs Stormosse, Central Sweden
- 2000
-
Ingår i: Journal of Vegetation Science. - 1100-9233 .- 1654-1103. ; 11:2, s. 277-286
-
Tidskriftsartikel (refereegranskat)abstract
- The Skattlosbergs Stormosse min was reinvestigated in 1995 after 50 years of natural development since the previous investigation. The undrained mire is situated in an area with low anthropogenic deposition. The distribution of 106 plant species was mapped in detail and pH was measured at 251 locations, providinga unique opportunity to quantify long-term mire dynamics. The resultss how decreased pH in the richer (high-pH) parts of the mire, but little or no change in the poor fen andombrotrophipca rts.1 4 species had disappeared while two news pecies were recorded. Most species had a more restricted distribution in the mire area in 1995 than in 1945. Species richness in lOm x 0Omp lots had decreased, especially in plots with higher pH. Most Sphagnum species had unchanged distributions over the mire, while 7 3 % of other bryophyt sepecies and 3 8% of vascular plant species had decreased by more than 20 % in plot frequency. There was a strong relationship between number of species and pH-value. The mean and standard eviation of pH in plots where the species occurred have both decreased since 1945. We interpret the changes in species richness in the richer fens to be mainly caused by acidification. This could partly be an autogenic succession, but may be enhanced by increased atmospheric deposition. The mire represents an almost untouched site which can act as a reference for mires in morepolluted areas.
|
|
| 7. |
- Milberg, Per, 1959-, et al.
(författare)
-
Timing of disturbance and vegetation development : How sowing date affects the weed flora in spring-sown crops
- 2001
-
Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 12:1, s. 93-98
-
Tidskriftsartikel (refereegranskat)abstract
- The number of annual weeds were recorded in 752 field experiments in spring-sown cereal crops conducted in Sweden 1972-1993. Two null hypotheses were tested regarding how the sowing date influenced the weed flora. 1. There is no relationship between the weed flora composition and sowing date. A pCCA (with geographic regions, crop species and soil types as covariables) clearly refuted this hypothesis. Hence, the composition of the weed flora varied depending on sowing date. 2. Species classified as summer annuals, winter annuals and germination generalists (that can germinate substantially in both spring and autumn) do not differ in their placement along the first ordination axis in the pCCA, i.e. according to sowing date. An ANOVA was unable to reject this hypothesis. Hence, germination syndrome classification did not explain the observed community differences related to sowing date. These results illustrate the importance of the date of disturbance for any secondary succession involving a seed bank and also the importance of annual dormancy cycles in seed banks.
|
|
| 8. |
- Xiong, Shaojun, et al.
(författare)
-
Responses of riparian plants to accumulation of silt and plant litter : the importance of plant traits
- 2001
-
Ingår i: Journal of Vegetation Science. - 1100-9233 .- 1654-1103. ; 12, s. 481-490
-
Tidskriftsartikel (refereegranskat)abstract
- A 2-yr field experiment was used to determine the response of riparian plants to accumulation of litter or silt in a river flood-plain meadow in northern Sweden. Such disturbances occur regularly in free-flowing rivers but are likely to change as a result of global changes in land use or climate. We anticipated that plants with different traits would differ in their response to litter and silt accumulation. We quantified plant response as relative change in above-ground biomass, and regressed it on either litter mass or silt depth, and on plant traits such as lateral spread, plant height, relative growth rate, seed mass and seed persistence in soil. The relative changes in riparian plant biomass following litter or silt accumulation were negatively related to litter mass and silt depth, and positively related to most examined plant traits Such as seed mass. seed persistence and lateral spread. The vegetation recovery in the second season was largely determined by plant traits; litter or silt accumulation had no significant effect. Litter accumulation selected for large-seeded species, but silt accumulation selected for species with strong ability of lateral spread. Seed persistence was a useful variable in predicting species recovery from both litter and silt accumulation. Plant height was negatively related to plant recovery, but relative growth rate was not significantly related to relative change in plant biomass after silt or litter accumulation. Our results imply that plant traits are important variables to consider for predicting the responses of riparian vegetation to deposition of organic and inorganic matter.
|
|
| 9. |
- Brathen, K A, et al.
(författare)
-
More efficient estimation of plant biomass
- 2004
-
Ingår i: Journal of Vegetation Science. - 1654-1103. ; 15:5, s. 653-660
-
Tidskriftsartikel (refereegranskat)abstract
- Question: The optimal use of the point intercept method (PIM) for efficient estimation of plant biomass has not been addressed although PIM is a commonly used method in vegetation analysis. In this study we compare results achieved using PIM at a range of efforts, we assess a method for calculating these results that are new with PIM and we provide a formula for planning the optimal use of PIM. Location: Northern Norway. Methods: We collected intercept data at a range of efforts, i.e. from one to 100 pins per 0.25 m(2) plots, on three plant growth forms in a mountain meadow. After collection of intercept data we clipped and weighed the plant biomass. The relationship between intercept frequency and weighed biomass (b) was estimated using both a weighted linear regression model (WLR) and an ordinary linear regression model (OLR). The accuracy of the estimate of biomass achieved by PIM at different efforts was assessed by running computer simulations at different pin densities. Results: The relationship between intercept frequency and weighed biomass (b) was far better estimated using WLR compared to the normally used OLR. Efforts above 10 pins per 0.25 m(2) lot had a negligible effect on the accuracy of the estimate of biomass achieved by PIM whereas the number of plots had a strong effect. Moreover, for a given level of accuracy, the required number of plots varied depending on plant growth form. We achieved similar results to that of the computer simulations when applying our WLR based formula. Conclusion: This study shows that PIM can be applied more efficiently than was done in previous studies for the purpose of plant biomass estimation, where several plots should be analysed but at considerably less effort per plot. Moreover, WLR rather than OLR should be applied when estimating biomass from intercept frequency. The formula we have deduced is a useful tool for planning plant biomass analysis with PIM.
|
|
| 10. |
- Jonsson, Bengt-Gunnar
(författare)
-
Availability of Coarse Woody Debris in a Boreal Old-Growth Picea abies Forest
- 2000
-
Ingår i: Journal of Vegetation Science: official organ of the international association for vegetation science. - 1100-9233. ; 11:1, s. 51-56
-
Tidskriftsartikel (refereegranskat)abstract
- This study reports temporal (based on cross-dated dead trees) and spatial patterns of availability of coarse woody debris (CWD) from Picea abies in a Swedish boreal landscape with discrete old-growth forest patches in a wetland matrix. Data were collected from 29 patches ranging in size from 0.3 to 28 ha. A total of 897 dead trees with a minimum diameter of 15 cm occurred on the 7.2 ha area analysed. The year of death was established for 50 % of these trees. CWD volume ranged from 17 to 65 msup3/sup/ha for downed logs and from 0.5 to 13 cmsup3/sup/ha for standing snags. CWD of all decay stages and diameter classes occurred abundantly and the probability of finding logs of all decay stages and sizes was very high at the scale of single hectares. Tree mortality differed among 5 yr periods. However, during the last 50 yr no 5 yr period produced less than 3 logs/ha. Decay rates were highly variable among different logs. Logs with soft wood and some wood pieces lost (decay stage 5) died ca. 34 years ago. This suggests a fairly rapid decay in this northern forest. The data indicate a high and continuous availability of CWD of all types. It is likely, therefore, that selection pressures for efficient dispersal among CWD dependent species may not be very high. Consequently, species with narrow habitat demands and/or low dispersal ability may have evolved and this may contribute to the decrease of certain species in the managed landscape.
|
|
| 11. |
- Niklasson, M, et al.
(författare)
-
A long-term record of Quercus decline, logging and fires in a southern Swedish Fagus-Picea forest
- 2002
-
Ingår i: Journal of Vegetation Science. - 1654-1103. ; 13:6, s. 765-774
-
Tidskriftsartikel (refereegranskat)abstract
- We reconstructed forest development and disturbance events (fire and logging) during the last 1000 yr with tree-ring data, pollen and charcoal analysis from a semi-natural Fagus sylvatica-Picea abies forest (ca. I km(2)) in the hemiboreal zone. According to pollen analysis, Quercus robur together with Pinus sylvestris was abundant in the forest until the turn of the 18th/19th centuries when these species disappeared completely (Quercus) or nearly completely (Pinus) and were replaced by Fagus and Picea. The disappearance of Quercus was corroborated by the remarkable discovery of a single Quercus stump that had been cut in the 18th century and had become overgrown and preserved by a very old Picea. In total I I fires were dated from 1555 to 1748 from fire scars in several Pinus stumps cut 100 - 200 yr ago. Since the last fire in 1748, no Quercus or Pinus have regenerated in the core of the reserve apart from single pines in neighbouring managed forest (80 yr ago). During the period of documented fires Fagus was protected from fires in a refuge made up of large boulders. Picea colonized the region at the time when the fires ceased 250 yr ago. We hypothesize that most of the fires were probably of human origin because of their patchiness and high frequency compared to the natural background levels of lightning ignitions in the region. On a 300-yr time scale, logging and fire suppression seem to strongly overshadow the effect of climate change on forest composition and dynamics.
|
|
| 12. |
- Pan, Y, et al.
(författare)
-
A biogeochemistry-based dynamic vegetation model and its application along a moisture gradient in the continental United States
- 2002
-
Ingår i: Journal of Vegetation Science. - 1654-1103. ; 13:3, s. 369-382
-
Tidskriftsartikel (refereegranskat)abstract
- We develop and evaluate a large-scale dynamic vegetation model, TEM-LPJ, which considers interactions among water, light and nitrogen in simulating ecosystem function and structure. We parameterized the model for three plant functional types (PFTs): a temperate deciduous forest, a temperate coniferous forest, and a temperate C-3 grassland. Model parameters were determined using data from forest stands at the Harvard Forest in Massachusetts. Applications of the model reasonably simulated stand development over 120 yr for Populus tremuloides in Wisconsin and for Pinus elliottii in Florida. Our evaluation of tree-grass interactions simulated by the model indicated that competition for light led to dominance by the deciduous forest PFT in moist regions of eastern United States and that water competition led to dominance by the grass PFT in dry regions of the central United States. Along a moisture transect at 41.5degrees N in the eastern United States, simulations by TEM-LPJ reproduced the composition of potential temperate deciduous forest, temperate savanna, and C3 grassland located along the transect.
|
|
| 13. |
- Semenova, GV, et al.
(författare)
-
Plant functional types - a strategic perspective
- 2000
-
Ingår i: JOURNAL OF VEGETATION SCIENCE. - : OPULUS PRESS UPPSALA AB. - 1100-9233. ; 11:6, s. 917-922
-
Tidskriftsartikel (refereegranskat)abstract
- This paper discusses the use of Plant Functional Types to describe vegetation types - from plant communities to formations - in order to understand the ecological constraints of plants and plant communities on a higher level of abstraction. The terminolog
|
|
| 14. |
|
|
| 15. |
- Tyler, Torbjörn, et al.
(författare)
-
Sensitivity of the woodland herb Anemone hepatica to changing environmental conditions
- 2002
-
Ingår i: Journal of Vegetation Science. - 1654-1103. ; 13:2, s. 207-216
-
Tidskriftsartikel (refereegranskat)abstract
- The decline of deciduous woodland populations of Anemone hepatica L. in southern Sweden is documented and possible causes are discussed. The study was based on (1) re-investigations of 6.25 km(2) grid-squares first studied in 19381970, (2) distribution of A. hepatica in woodland sites with well-known soil chemical properties and (3) a detailed study over 12 consecutive years into the relationships between biological characteristics of the species (number of individuals, vegetative development, flowering frequency) and environmental variables (temperature, precipitation), soil chemistry and time. There was a close relationship between soil acidity (pH, solubility of Al3+) and both distribution and biological characteristics. The biological variables declined significantly overtime but were not related to climatic variability. Increasing soil acidity and Al3+ solubility are concluded to be the main factors responsible for the decline of A. hepatica in S. Swedish deciduous woodlands.
|
|
| 16. |
|
|
| 17. |
- Wikberg, Sofie, et al.
(författare)
-
Spatial variation in vegetation and abiotic factors related to the occurrence of a ring-forming sedge
- 2002
-
Ingår i: Journal of Vegetation Science. - 1654-1103. ; 13:5, s. 677-684
-
Tidskriftsartikel (refereegranskat)abstract
- The clonal sedge Carex humilis forms rings of densely aggregated ramets in a dry grassland community in Central Europe. We describe the small-scale spatial variation, both in abiotic factors and vegetation, in relation to these rings. Compared to the surrounding vegetation the cover of plants, other than C. humilis, was significantly lower both in the central area of rings and within the rings themselves. The vegetation structure was also different. The soil was more fertile in the central area and within the ring than in the surroundings, measured both directly and by the abiotic response values of the vascular plants. We conclude that neither resource depletion nor competition from other plants were likely to be responsible for the low ramet density in the central area of C. humilis rings. Instead, we suggest that the ring form is caused either by the deposition of growth inhibiting substances or by intrinsic morphological rules.
|
|
