| 1. |
- Engelmark, O., et al.
(författare)
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Ecological effects and management aspects of an exotic tree species : the case of lodgepole pine in Sweden
- 2001
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Ingår i: Forest Ecology and Management. - 0378-1127 .- 1872-7042. ; 141:02-jan, s. 3-13
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Tidskriftsartikel (refereegranskat)abstract
- The North American tree Pinus contorta var, latifolia was experimentally introduced in Sweden already in the 1920s, and has been used in Swedish forestry on a large scale since the 1970s. These plantations now cover 565,000 ha, mainly in the northern area. In this paper we summarize and discuss existing ecological knowledge of this species introduction. With regard to longterm sustainability we suggest management means to minimize harmful effects of the introduction on ecosystems. These include aspects of self dispersal, pests, ecosystem and landscape structures, and also ecological processes and biodiversity. We also focus on observed and possible interactions in the ecosystems. As Pinus contorta seeds are disseminated and trees regenerated outside initial plantations, this may have future bearings on biodiversity. We suggest a strategy which takes account of the uncertainty in predicting future ecological effects. The strategy includes areal restrictions and zones without Pinus contorta, but also to set up a monitoring program. Observations of adverse effects from the plantations would then give the possibility to adjust P. contorta management.
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| 2. |
- Akselsson, Cecilia, et al.
(författare)
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Regional mapping of nitrogen leaching from clearcuts in southern Sweden
- 2004
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 1872-7042 .- 0378-1127. ; 202:1-3, s. 235-243
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Tidskriftsartikel (refereegranskat)abstract
- Increased nitrogen leaching from forest soils is a potential environmental problem in areas with high nitrogen deposition. In Sweden nitrogen is strongly retained in the forests, and high nitrogen leaching is not common from growing forests. However, soil water measurements on clearcuts along a deposition gradient in Sweden showed a positive correlation between increased concentration of inorganic nitrogen and the deposition. In this paper nitrogen leaching from clearcuts in southern Sweden was modelled on a municipality level, based on this correlation. Modelled deposition was used as input data together with runoff and forest statistics, e.g. clearcut areas from the municipalities. The calculations showed a clear leaching gradient on clearcuts from west (up to 35 kg ha(-1) year(-1)) to east (less than 5 kg ha(-1) year(-1)). This was in accordance with the deposition gradient. The leaching gradient was reinforced by the higher runoff in the west. The results indicated that, in southwestern Sweden with the highest nitrogen deposition, up to 30-40% of the total leaching of nitrogen from forest soils originates from clearcuts. These high amounts of nitrogen leaching from clearcuts in southwestern Sweden have not been included in previous national calculations of nitrogen leaching to surface waters. The contribution of nitrogen from clearcuts to the total nitrogen leaching from all land use classes varies between 1% in the southernmost part where agricultural land is highly dominating, to 11% in the forested central part of southern Sweden. (C) 2004 Elsevier B.V. All rights reserved.
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| 3. |
- Borjesson, G, et al.
(författare)
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Fast recovery of atmospheric methane consumption in a Swedish forest soil after single-shot N-fertilization
- 2000
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Ingår i: Forest Ecology and Management. - 0378-1127 .- 1872-7042. ; 134:1-3, s. 83-88
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Tidskriftsartikel (refereegranskat)abstract
- Methane consumption was measured in samples from a Swedish forest soil once every autumn for 2 years after fertilization with 150 kg N ha(-1) as calcium ammonium-nitrate. Although fertilization initially depressed methane consumption, this effect tended to decline during the remainder of the first year, accompanied by the disappearance of inorganic N. After 2 years, the methane oxidation capacity was found to be substantially higher in the fertilized plots compared with the controls. The difference between years was pronounced, with very high rates registered 2 years after the start of the experiment. These high rates were probably due to a rapid growth of methanotrophic organisms in response to an unusually warm period preceding the date of sampling. (C) 2000 Elsevier Science B.V. All rights reserved.
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| 4. |
- Hagen-Thorn, Anna, et al.
(författare)
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The impact of six European tree species on the chemistry of mineral topsoil in forest plantations on former agricultural land
- 2004
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 1872-7042 .- 0378-1127. ; 195:3, s. 373-384
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Tidskriftsartikel (refereegranskat)abstract
- Influences on mineral topsoils of common European tree species (oak-Quercus robur L., lime-Tilia cordata Mill., ash-Fraxinus excelsior L., birch-Betula pendula Roth., beech-Fagus sylvatica L. and spruce-Picea abies (L.) Karst.) were studied in 30 to 40-year-old stands planted in adjacent plots on former arable land. Mineral soil samples from two depth layers (0-10 and 20-30 cm) under the different species were compared in terms of pH, base saturation, pools and concentrations of exchangeable macro- and micronutrients, total nitrogen and carbon. With the exception of pH (H2O) and extractable Al and Fe, no significant differences between species were detected in the lower layer. The upper (0-10 cm) layer was, however, affected differently depending on tree species: significant differences in pH, base saturation, exchangeable base cations and other nutrients were observed. The most prominent differences were between lime and spruce. Lime had considerably higher pH, base saturation, base cation and boron pools compared to spruce, which had the most acidifying effect on the mineral topsoils. Among the deciduous species, beech had the most similar effect to spruce on the upper layer of mineral topsoils. Soil C, N and C/N ratios did not differ significantly among species.
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| 5. |
- Jacks, Gunnar, et al.
(författare)
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Hydrochemistry and hydrology of forest riparian wetlands
- 2004
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 196:03-feb, s. 187-197
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Tidskriftsartikel (refereegranskat)abstract
- Forest stream riparian wetlands have a number of important features. This investigation treats one aspect, the nitrogen retention after upland clear-cutting which leads to elevated nitrate leaching, and the importance of the flow pathways in this connection. The runoff occurs mainly via the upper permeable section of the peat while the lower peat act as an aquitard, restricting the flow from the underlying till. The till groundwater is progressively artesian towards the discharging stream. Water analyses from piezometers show that the water chemistry in the peat is rather variable, indicating the presence of channelling. Channelling is also indicated by spring discharges from the peat that have elevated nitrate contents pointing to bypass flow. Redox bars indicating sulphate reduction display the same picture of irregular distribution. However, a general observation is that volumes with sulphate reduction increase towards the stream and that sulphate reduction occurs preferably in the surface peat, indicating the importance of a degradable substrate for the sulphate reducers. Nitrate reduction during the growth season occurs predominantly close to the upland till areas. The riparian tree stand is dominated by spruces which are likely to be disfavoured by the rising groundwater level after clear-cutting. The riparian tree stand does not extend far enough towards the upland to be benefited by the elevated nitrate flux. Buffer stands should be broader, extending into the till upland where they can utilise the leached nitrate and, more important, thanks to their deeper rooting depth protect the peatland trees against wind felling.
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| 6. |
- Jönsson, Anna Maria, et al.
(författare)
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Frost sensitivity and nutrient status in a fertilized Norway spruce stand in Denmark
- 2004
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 1872-7042 .- 0378-1127. ; 201:2-3, s. 199-209
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to assess the effect of the N, P and K status on frost sensitivity of Norway spruce needles in a fertilization experiment situated in a nutrient poor 29-year-old Picea abies stand in western Denmark. The relative difference in frost sensitivity among trees was assessed by an index of injury, based on conductivity measurements of ion leakage from needles. Despite fertilization, all trees indicated N, P and K deficiency. The foliage, collected in late winter, was generally not very frost sensitive, but foliage from trees with the lowest K and P status were more sensitive to frost, and the current year needles were more sensitive than the second and third year needles. The advancement of bud burst was assessed in May. Trees with a relatively high N concentration in the current year needles had a more advanced bud burst than trees with a lower N concentration, increasing the risk for frost damage by a temperature backlash.
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| 7. |
- Lagergren, Fredrik, et al.
(författare)
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Variation in sapflow and stem growth in relation to tree size, competition and thinning in a mixed forest of pine and spruce in Sweden
- 2004
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 1872-7042 .- 0378-1127. ; 188:1-3, s. 51-63
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to analyse the relationship between different biometric parameters and sapflow and growth, respectively, in order to assess their potential for use in scaling. The effect of thinning on these relationships was also investigated. The studied stand consisted of Scots pine (ca. 60%), Norway spruce (ca. 35%) and downy birch (ca. 5%). Sapflow was measured by the tissue heat-balance method, and growth in circumference was measured by dendrometer bands, during a 3-year period. The thinning was carried out after 1 year of measurements. Regressions were calculated between sapflow and growth and tree diameter, needle mass estimated by allometry, and a competition index (CI), which depended on the distance and diameter of neighbouring trees. Both sapflow and growth were affected by strip-roads from a thinning ca. 8 years earlier. Before thinning, the variation in sapflow for spruce was best explained by CI when trees close to a strip-road were excluded; for pine, needle mass was equally as good as CI. In 1999 and 2000, needle mass generally explained the variation in sapflow best. Before thinning, the variation in pine growth was explained almost as well by diameter alone, as by CI. For spruce, needle mass explained most of the variation if all trees were included. If trees beside strip-roads were excluded, r(2) for CI increased and CI explained the variation best. Almost all spruces close to strip-roads had lower growth than was expected from their CI relationships; for pine, 13 of 23 trees had higher growth than expected. For the years after thinning, diameter was mostly at least as good as the other variables for predicting BA growth. It was concluded that a competition index is potentially useful for scaling, and that strip-roads affected both sapflow and growth of nearby trees. This should be considered in sampling design as well as in scaling up to stand level. (C) 2003 Elsevier B.V. All rights reserved.
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| 8. |
- Nilsson, Carin, et al.
(författare)
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Recorded storm damage in Swedish forests 1901-2000
- 2004
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 1872-7042 .- 0378-1127. ; 199:1, s. 165-173
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Tidskriftsartikel (refereegranskat)abstract
- Severe storm damage has been a recurring problem to the Swedish forestry sector since, at least, the start of the 19th century. This short communication presents a regionally resolved time-series of storm damage in Swedish forests during the last century. Data on storm damage have been gathered from the National Board of Forestry, the Regional Forestry Boards and scientific reports. Storm damage in Swedish forests seems to have increased during the century with a peak around the 1980s. In total 110 million m 3 forest were destroyed by 77 recorded wind storms, with the severe storms in 1954 and 1969 accounting for 49% of the total damage. Reported damage in southern Sweden was normalised against the area of productive forest with trees older than 40 years, for inter annual comparisons. The geostrophic wind was used to describe the regional wind direction during the storm events. Most damage occurred during NNW to SW winds, and by winds from NNE. Apart from a possible shift in storm intensity and frequency, the increase in storm damaged trees can be attributed to changes in regeneration and thinning regimes, variations in storm damage reporting system, increase in forest cover and various damage to root architecture.
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| 9. |
- Wolf, Annett, et al.
(författare)
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Storm damage and long-term mortality in a semi-natural, temperate deciduous forest
- 2004
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Ingår i: Forest Ecology and Management. - : Elsevier. - 0378-1127 .- 1872-7042. ; 188:1-3, s. 197-210
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Tidskriftsartikel (refereegranskat)abstract
- 1.Wind-damaged trees, following the severe storm of 1999, are compared with data from a 50-year monitoring of Draved Forest, Denmark, to assess differing causes of mortality through time in an unmanaged semi-natural forest. Species-specific mortality characteristics and the changing effects of tree size and growth rate (diameter increment) on mortality through time are also investigated.2.Storm was found to be the major mortality factor affecting large trees in this forest. For smaller trees, competition was an important cause of death, as trees that were found standing dead had a slower growth rate (diameter increment) than survivors.3.Individual species showed different mortality patterns. Betula died more often and Fagus less often than expected from their abundance. Betula, Fagus and Tilia were mainly wind-thrown, whereas for Alnus and Fraxinus, 50% of the mortality was observed as standing dead trees.4.Both wind and competition are important mortality factors in Draved Forest.
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| 10. |
- Bergstedt, Johan, et al.
(författare)
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The impact of logging intensity on field-layer vegetation in Swedish boreal forests
- 2001
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Ingår i: Forest Ecology and Management. - 0378-1127. ; 154:1-2, s. 105-115
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Tidskriftsartikel (refereegranskat)abstract
- The relationship between logging intensity and changes in ground cover vegetation was studied in 16 species and groups of species recorded at 10- or 11-year intervals in mature conifer-dominated forests. The 789 plots located in northern and central Sweden had been surveyed by the National Forest Inventory and the National Survey of Forest Soil and Vegetation. Thirty-seven percent of the plots had been subjected to a thinning or clear-cutting between the inventories. A principal components analysis showed that, of the variables considered, logging intensity had the highest explanatory power regarding change in ground cover vegetation between the inventories (the other variables were sum of temperatures, age of stand, timber volume, percentage Pinus sylvestris and site productivity). A multivariate direct gradient analysis technique (Redundancy analysis) showed that the logging intensity significantly affected the change in cover. This analysis also ranked the species in their responsiveness to logging. Epilobium angustifolium, narrow-leaved grasses and broad-leaved grasses, increased most with logging intensity. The response was not linear and only detectable at high logging intensities (>80%). In contrast, Vaccinium myrtillus seemed to decrease linearly with increased logging intensity. There was several years time-lag in the response to logging of E. angustifolium, V. myrtillus and narrow-leaved grasses. Several species and groups of species seemed unaffected by the logging. In sample plots unaffected by logging the cover of most species decreased.
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| 11. |
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| 12. |
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| 13. |
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| 14. |
- Falkengren-Grerup, Ursula, et al.
(författare)
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Use of a gradient of N-deposition to calculate effect-related soil and vegetation measures in deciduous forests
- 2003
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Ingår i: Forest Ecology and Management. - 1872-7042. ; 180:1-3, s. 113-124
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Tidskriftsartikel (refereegranskat)abstract
- Deposition of N and S has increased since the 1950s in most European countries and N accumulates in ecosystems that are not N saturated. This study shows long-term effects of a (modelled) N deposition of 7-17 kg N ha(-1) per year on biological and chemical processes in soil, vegetation composition, and functional types of field-layer plant species in deciduous forests. Soil pH largely determined the response of the soil processes, emphasising the importance to compare soils of similar acidity regarding the effects of N deposition. The most pronounced effects were demonstrated for the most acid study plots. When we compared regions with a deposition of 7 and 17 kg N ha(-1) per year we found a 40-80% higher soil N mineralisation rate, 2-90% higher nitrification rate and 10-25% lower C:N ratio in the region with the highest deposition. Similar but smaller differences were indicated when regions with a deposition of 7 and 10 kg N ha(-1) per year were compared. Number of species was lower in the regions with the highest deposition. Literature data for plants on N concentration, nitrate reductase activity (NRA), growth rates, morphology and height were calculated on a site basis. They varied to different extent between the regions. The N concentration was 7-24% higher in the regions with the highest N deposition. We argue that the effect-related critical load based on our results should be set to a N deposition of 7-10 kg N ha(-1) per year. Critical loads for a subdivision of deciduous forests would give lower critical loads for the most acid soils compared to less acid soil.
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| 15. |
- Fransson, Ann-Mari, et al.
(författare)
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Phosphorus fertilisation causes durable enhancement of phosphorus concentrations in forest soil
- 2000
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Ingår i: Forest Ecology and Management. - 1872-7042. ; 130:1-3, s. 69-76
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Tidskriftsartikel (refereegranskat)abstract
- The duration of P fertiliser in acid forest soil was investigated in a Norway spruce (Picea abies Karst.) forest in southcentral Sweden. The fertilisation of the soil started in 1967, but no P has been applied since 1988. The N fertilisation is still continuing. Totally, 300 kg P per hectare, as superphosphate, and/or 1090 kg N per hectare, as ammonium nitrate, was applied. Concentrations of both 0.05M Na2SO4 + 0.02M NaF extractable P and 0.5M H2SO4 extractable P in the Of, Oh, E and top B horizons of fertilised soils were elevated compared to the control. The P fractions considered to be extracted are adsorbed and some Al-bound phosphate, in the case of Na2SO4 + NaF, and Ca phosphates, in the case of H2SO4. 3-4% of the added P was recovered as Na2SO4 + NaF extractable P, and 10-22% was recovered as H2SO4 extractable P in the soil profile down through the first 5 cm of the B horizon. Still continuing ammonium nitrate fertilisation has decreased the H2SO4 extractable P concentration in this soil. Cumulative P fertiliser application of 300 kg P per hectare has counteracted this decrease. (C) 2000 Elsevier Science B.V. All rights reserved.
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| 16. |
- Gunnarsson, Bengt, 1954, et al.
(författare)
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Effects of logging residue removal on ground-active beetles in temperate forests
- 2004
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127. ; 201:2-3, s. 229-239
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Tidskriftsartikel (refereegranskat)abstract
- Logging residue ("slash") left on clear-cuttings may affect the microhabitat complexity, and thereby indirectly the beetle (Coleoptera) populations. In three regions (West, North and East) of south and central Sweden, we studied short-term effects of slash removal on species richness and abundance of beetles, collected by pitfall trapping in 16 clear-cuttings (<1 year old) in coniferous and mixed forests. The sites were managed in two alternative ways, either slash was removed (SR), or slash was left (SL). Overall, the number of morphospecies per trap was significantly higher on SL sites than on SR sites. Species richness differed significantly between the regions, the Western region being the poorest in number of species per trap. Rarefaction plots of species richness in four sites suggested that accumulation rate of species differed between two SR sites but rates were similar for two SL sites. Microhabitat structure was measured by aboveground height of slash heaps. Slash height was positively correlated with the number of sticks in slash heap and fractal dimension, respectively. There was a positive relationship between the number of individuals per trap and slash height in SR sites in the Western and Eastern regions, but not in the Northern one. We concluded that extensive slash removal leads to impoverish species richness of Coleoptera. at a local scale. Slash heaps left on site may provide important refuges for ground-active beetles. Moreover, our results supported the general theory that microhabitat structure affects arthropod abundance and diversity. (C) 2004 Elsevier B.V. All rights reserved.
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| 17. |
- Jönsson, Anna Maria
(författare)
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Soil treatment effects on bark lesions and frost sensitivity of beech (Fagus sylvatica) in southern Sweden
- 2000
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Ingår i: Forest Ecology and Management. - 1872-7042. ; 129:1-3, s. 167-175
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Tidskriftsartikel (refereegranskat)abstract
- Bark lesions on beech are mostly caused by frost damage and/or insect and fungal infections. Liming, treatment with wood ash and N-fertilization were hypothesised to affect this type of damage. The frost sensitivity was measured as an index of injury, calculated from electrolytic leakage of bark samples. Samples were taken from the same trees in August and November at five sites. Two sites had been limed, one treated with wood ash and two had been fertilized with nitrogen, one of them with an additional phosphorous fertilization. Trees fertilized with nitrogen had significantly more lesions than trees from other treatments. The bark was more damaged at -20 degrees C than at -10 degrees C in both August and November at experimental conditions. No clear pattern in temperature sensitivity was detectable among sites or treatments approximately seven years after soil treatment. Trees with bark lesions seemed to be less able to withstand low temperatures. (C) 2000 Elsevier Science B.V. All rights reserved.
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| 18. |
- Kalén, Christer, et al.
(författare)
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Forage availability for moose of young silver birch and Scots pine
- 2004
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Ingår i: Forest Ecology and Management. - 1872-7042. ; 187:2-3, s. 149-158
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Tidskriftsartikel (refereegranskat)abstract
- Forestry in Sweden suffers from browsing damage caused by large herbivores, mainly moose (Alces alces) and roe deer (Capreolus capreolus). Silviculture affects the availability of forage for these animals, and thus the browsing pressure. A step towards modeling the response of trees or to predict browsing damage is to gain more knowledge on the availability of food in forest stands. Individual gap-models are a genre of computer models widely used in studying forest dynamics. Since few of these models include browsing effects, however, they are of limited use for evaluating the effects that silvicultural strategies have on forage availability and browsing damage. The aim of this study was to collect data useful in developing a model for describing the amounts of biomass of young birch (Betula pendula) and pine (Pinus sylvestris) trees available to moose. Birch and pines trees were harvested and were divided into different biomass fractions (leaves and twigs of different diameters). The distribution of leaf/needle and twig biomass in the crown was recorded by dividing the trees into sections. The results showed the distribution of the crown biomass to be best described by a sinusoidal model. On average, the model described 79 and 86% (pine and birch, respectively) of the variation in the different fractions. A significant relationship was found between the basal area and the amounts of both leaves and twigs of the different fractions. The biomass available for consumption increased with tree height up to a maximum of 0.6 and 1.0 kg per tree (pine and birch, respectively), 4 m in height. The correlations obtained can be used for introducing browsing into existing gap-models. (C) 2003 Elsevier B.V All rights reserved.
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| 19. |
- Mahmood, Shahid, et al.
(författare)
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Ectomycorrhizal colonisation of roots and ash granules in a spruce forest treated with granulated wood ash
- 2002
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Ingår i: Forest Ecology and Management. - 1872-7042. ; 160:1-3, s. 65-74
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Tidskriftsartikel (refereegranskat)abstract
- Granulated wood ash has been proposed as a slow release fertiliser suitable for forest soils. In this study ectomycorrhizal colonisation of roots and ash granules was studied in a 40-year-old spruce forest treated with 0, 3 or 6 t ha(-1) granulated wood ash. We used PCR-RFLP methods for ITS-typing and identification of ectomycorrhizal fungi. In total 20 different ITS-types were recognised on roots in the organic soil horizon. Five of these were identified to species and two to genus. Six species, Tylospora fibrillosa Donk, Cortinarius sp. 3, Piloderma sp. 1, and three unidentified ITS-types (Ve-95-1, To-95-3 and Ve-95-9) each occurred on over 5% of the total root tips analysed. Together these comprised 557c of the ectomycorrhizal community on the screened roots. Ash granules collected from the fertilised plots were normally colonised by fungal mycelia. PCR-RFLP analysis of these mycelia revealed the presence of four ITS-types. Three of these (Piloderma sp. 1, Ha-96-3 and Tor-97-1) were also present on the mycorrhizal roots. Piloderma sp. I was the most abundant species colonising roots. A possible role of ectomycorrhizal mycelia in the direct mobilisation of nutrients from ash granules is discussed. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 20. |
- Mellander, Per-Erik, et al.
(författare)
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The influence of soil temperature on transpiration: : a plot scale manipulation in a young Scots pine stand
- 2004
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127. ; 195:1-2, s. 15-28
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Tidskriftsartikel (refereegranskat)abstract
- Classic studies have stressed the importance of forest management for soil frost and the dynamics of soil warming during spring. But, we know very little about the potential loss of forest production due to cold soils. Liquid soil water may not be available to trees due to cold soil conditions, thus reducing transpiration and photosynthesis. We believe that these effects need to be quantified in order to keep silvicultural practices from inadvertently reducing forest growth through effects on soil temperature. In order to test this hypothesis it is important to know more about water uptake in the field by trees in cold environments. The snow cover was manipulated on plots in a young stand of Pinus sylvestris L. to create plots with different timings of soil warming. Soil profile temperature and liquid water content, as well as snow and frost depths, were measured together with tree physiological parameters such as sap flow, stomatal conductance and needle water potential. The study has confirmed the importance of the soil temperature for tree water uptake when soil warming was delayed beyond the start of growing season as defined by air temperature. The absence of frost (and hence the presence of liquid water) was not sufficient to enable water uptake. It was rather elevation of soil temperature above zero in the upper soil layers that was required for substantial water uptake, in combination with other site factors. Below ca. +8 °C, soil temperature was a factor in the restriction of transpiration, explained by a lower stomatal conductance and likely decreased root permeability. The effect of a certain soil temperature was not the same at different times due to its interaction with aboveground factors such as air temperature and day-length. The effect of low soil temperature increased with the persistence of low temperatures after the start of the growing season. The timings of soil warming induced by our study were within the spatial and inter-annual variation of soil warming in this region. Thus, we conclude that influences of forest management on soil temperature can affect the transpiration deficit during spring, with potential implications for forest productivity
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| 21. |
- Månsson, Katarina, et al.
(författare)
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The effect of nitrogen deposition on nitrification, carbon and nitrogen mineralisation and litter C : N ratios in oak (Quercus robur L.) forests
- 2003
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Ingår i: Forest Ecology and Management. - 1872-7042. ; 179:1-3, s. 455-467
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Tidskriftsartikel (refereegranskat)abstract
- The present study addresses the question why there is a positive relationship between nitrogen deposition and potential net nitrogen mineralisation and nitrification in oak (Quercus robur L.) forest soils in south Sweden (Falkengren-Grerup et al., 1998), and how this is related to the carbon mineralisation. We tested three hypotheses based on European studies (Persson et al., 2000a,b) that postulate lower availability of carbon due to chemical binding of nitrogen to lignin remains and phenolic compounds or a more decomposed, recalcitrant organic matter due to faster initial decomposition rates of fresh litter. This in turn leads to increased net nitrogen mineralisation, and nitrifiers that may adapt to acid soils when ammonium availability increases. We used soils from two regions exposed to a total deposition of 17 and 10 kg N ha(-1) per year and incubated the soils in the laboratory separately as well as in mixtures between the regions. To be able to evaluate how the microbial communities and organic matter interacted in the soil mixtures, we divided the observed values of the net carbon and nitrogen mineralisation and nitrification for the soil mixtures by the calculated expected values. C:N ratios of litter, fresh leafs of Deschampsia flexuosa and microbial biomass were also measured. Contrary to the assumptions in the hypothesis, the soil respiration was somewhat higher in soils subjected to high nitrogen deposition. Furthermore, the observed rate of nitrogen mineralisation was higher than expected in the majority of soil mixtures, while observed rates of carbon mineralisation only showed a weak tendency to be higher than expected. All the results taken together indicate that there has been a positive change in litter quality that leads to increased carbon and nitrogen mineralisation. This conclusion is supported by the C:N ratio of oak litter and fresh leaves of Deschampsia flexuosa that was lower in the most nitrogen-exposed sites and which might indicate an increase in decomposability. The observed values of nitrification were significantly higher than the calculated expected values. Thus, the increased net nitrogen mineralisation in the region with high nitrogen deposition seems to allow nitrifiers to adapt to these acid soils when they are no longer limited by ammonium.
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| 22. |
- Nilsson, Sven, et al.
(författare)
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Densities of large living and dead trees in old-growth temperate and boreal forests
- 2002
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Ingår i: Forest Ecology and Management. - 1872-7042. ; 161:1-3, s. 189-204
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Tidskriftsartikel (refereegranskat)abstract
- We recorded and reviewed densities and basal areas of large living and dead trees in old-growth forest in Europe. Recorded densities were similar to those reported from old-growth forests in eastern North America, but lower than in northwestem North America. Based on our results we suggest that, 10-20 living trees per ha with dbh > 70 cm may have been typical values for many central European and south Scandinavian virgin forests. In boreal forests, it was probably common with at least 20 living trees per ha with dbh > 40 cm. Basal areas of living trees in mixed old-growth forests in central Europe and southern Sweden were 34-40 m 2 per ha on dry ground and about 60 m(2) per ha in wet alder-ash-spruce forests. Densities of large trees (dbh > 40 cm) were twice as high in the latter forest type than on dry ground in Bialowieza forest, Poland. Based on our results, we propose the following generalizations to be further tested in other old-growth temperate and boreal forests: 1. Among all standing trunks (including high stumps) about 10% are dead. but this proportion increases for the largest trees. The proportion of standing trees that are dead seem to be independent of total basal areas. Based on this, we suggest that the volume of dead wood is directly proportional to the productivity of old-growth forests. 2. Standing dead trees (snags) are on average larger than downed dead trees. Trees with dbh >40 cm often dominate the basal area and volume of standing dead trees and living trees. 3. About 30% (20-40%) of the basal area and volume of dead trees is standing in old-growth forests. This proportion seems to be independent of total volume of dead wood. Large disturbances by fire, strong winds and insects may temporarily change these proportions considerably in individual stands. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 23. |
- Nordén, Björn, 1965, et al.
(författare)
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Dead wood in semi-natural temperate broadleaved woodland: contribution of coarse and fine dead wood, attached dead wood and stumps
- 2004
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127. ; 194:1-3, s. 235-248
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Tidskriftsartikel (refereegranskat)abstract
- Dead wood is essential for biodiversity in forests and is therefore often surveyed in conservation inventories. Usually only coarse downed trees (logs) and standing dead trees (snags) are surveyed, but dead wood also occurs on living trees, in stumps, and in fallen branches. Attached, standing (including stumps) and downed dead wood with a diameter of more than I cm was surveyed in 25 semi-natural stands of temperate broadleaved woodland dominated by oak in southern Sweden (most trees younger than 70 years but with an older generation of Quercus, and often Corylus scrub). This study is primarily motivated by the rising interest in biofuel harvesting by thinning which will affect dead wood structure in forests, especially the finer dead wood fractions. The sites in this study contained on average 14.3 m(3)/ha coarse dead wood (defined as wood with a diameter >10 cm), which is more than twice as much as in production woodland. Fine dead wood (diameter 1-10 cm) made up another 12.2 m(3)/ha (45% of the total dead wood volume). Of the fine dead wood, on average 20% was oak wood and 71 % was wood from other broadleaved trees. The coarse dead wood fraction consisted equally of oak wood (46%) and wood from other broadleaved species (47%). Coniferous wood amounted to 7% (coarse dead wood) or 8% (fine dead wood). The total dead wood volume was dominated by downed (66%) and standing dead wood (22%), while attached dead wood and stumps amounted to smaller fractions (6% each). The total volume of fine dead wood did not correlate with the total volume of coarse dead wood. These results therefore suggest that fine dead wood cannot be predicted from conservation surveys of coarse dead wood. The value for biodiversity of fine dead wood is discussed, and should not be overlooked in conservation work due to the fact that for example, many fungi and insects are associated with it. (C) 2004 Elsevier B.V. All rights reserved.
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| 24. |
- Nyholm, N E I, et al.
(författare)
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Rubidium content of plants, fungi and animals closely reflects potassium and acidity conditions of forest soils
- 2000
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Ingår i: Forest Ecology and Management. - 1872-7042. ; 134:1-3, s. 89-96
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Tidskriftsartikel (refereegranskat)abstract
- Rubidium concentrations in tissues of organisms (vascular plants, fungus, insect, bird, rodents) were closely related to soil chemical properties (K+ saturation as % cation exchange capacity, and pH) at repeated sampling of 30 beech forest sites in south Sweden. The Rb+ concentration of organisms, representing a variety of tropic levels, was a sensitive measure of the K+ status of acid soil ecosystems. Low K+ status (pool of exchangeable K+) in the soil, usually aggravated by high soil acidity which causes K+ leaching losses, is compensated by greatly increased uptake of Rb+ by plants and fungi and these elevated Rb+ levels are propagated in the food web. The relationship between Rbi concentration in the tissues of organisms and soil chemical properties was not erased through the food web. (C) 2000 Elsevier Science B.V. All rights reserved.
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| 25. |
- Olsson, M O, et al.
(författare)
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Partitioning of nitrate uptake between trees and understory in oak forests
- 2003
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Ingår i: Forest Ecology and Management. - 1872-7042. ; 179:1-3, s. 311-320
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Tidskriftsartikel (refereegranskat)abstract
- The nitrate reductase activity (NRA) was measured during spring, early summer and late summer in three deciduous forests, where the tree layer was dominated by oak. The nitrate assimilation capacities of the compartments of the above-ground and below-ground biomass of the understory and of the leaves and roots of the tree layer were calculated as NRA per unit biomass and NRA per unit area. The NRA per unit biomass in the above-ground parts of the understory ranged from 0.56 to 13.6 mumol NO2- g(-1) dw h(-1) and was highest in the spring at all sites. The NRA per unit below-ground biomass ranged from 0.12 to 0.94 mumol NO2- g(-1) dw h(-1). For leaves, the NRA per unit biomass varied between 0.27 and 3.51 mumol NO2- g(-1) dw h(-1), and for the roots between 0.14 and 0.91 mumol NO2- g(-1) dw h(-1). Over 90% of the total nitrate uptake (measured as NRA m(-2)) was performed by the understory in the spring, when the nitrification is high, but the unleafed trees showed little activity. Measurements during other periods than spring are scarce in the literature, but results reported here demonstrate the importance of the understory also during the summer, as the NRA per unit biomass of the understory layer was quite high. Fifteen to 50% of the total NRA m(-2) was found in the understory. The capability of the understory and the tree layer to change NRA with nitrate availability and thereby prevent nitrate leaching is further discussed.
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| 26. |
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| 27. |
- Thelin, Gunnar, et al.
(författare)
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The nutrient status of Norway spruce in pure and in mixed-species stands
- 2002
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Ingår i: Forest Ecology and Management. - 1872-7042. ; 160:1-3, s. 115-125
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Tidskriftsartikel (refereegranskat)abstract
- Atmospheric deposition of N and S appears to have caused nutrient imbalance in Norway spruce stands in southern Sweden. This calls for a change of forest management to procedures that promote nutrient balance. Studies have shown lower soil acidity in Norway spruce/deciduous mixed stands than in spruce monocultures, but the tree nutrient status in such mixtures has not been much investigated so far. The nutrient status of Norway spruce foliage and top mineral soil chemistry in monocultures and in stands mixed with beech, birch, or oak was investigated through paired comparisons on 30 sites in southern Sweden (27 sites) and eastern Denmark (three sites). In total, 45 mixed stands and 34 pure stands were included in the study. Spruce needles from mixed stands had higher concentrations and ratios to N of K, P, and Zn than needles from pure spruce stands. Among the mixed stands, the K status appeared to be positively correlated with the percentage of deciduous tree basal area. Soil samples from mixed stands had a higher Mg concentration, base saturation, and BC/Al ratio than soil samples from pure stands. The spruce needle nutrient status was comparable in pure stands on fertile sites and in mixed stands on poor sites. We did not detect any differences in spruce tree growth between pure and mixed stands. This paper discusses possible reasons for a positive effect on the tree nutrient status in mixed-species stands and the possibility of using mixed-species stands as a forest management procedure to avoid nutrient imbalance. (C) 2002 Elsevier Science B.V. All rights reserved.
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