摘要:

The performance of a carbon‐balance model of tree growth is analysed, using a generalized sensitivity test based on Monte Carlo techniques. The tree growth model allocates carbon to different biomass compartments according to the principle of functional balance and the pipe‐model theory. A simple stand‐level version of the model is presented, based on average tree growth and canopy interactions through shading. Plausible ranges of parameter values are estimated from the literature for Scots pine. The results are compared with yield tables for 4 growing sites, and the most critical parameters and assumptions with respect to model validity are identified. The results indicate that a better understanding of the formation of the woody structure of trees is crucial for the further development of the approach. More reliable data are necessary on the parameters related with sapwood respiration and senescence. Secondly, the results are sensitive to light interception, suggesting that the assumption of horizontal homogeneity should be reconsidered, in particular, in the later stage of canopy development. Other important processes with unreliable and sparse data are those related to root functioning.

ISSN:0282-7581    

DOI:10.1080/02827588809382520

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Current annual needle litterfall was analysed in 16 Scots pine stands of different ages, site qualities and latitudes. As a mean, the current needle litterfall was 1605 kg (dw) per ha and year, corresponding to a current annual volume increase of 7.9 m3. It was shown that the needle litterfall 1) increased with increasing site quality, 2) decreased with increasing stand age, and 3) decreased with increasing latitude. An increase in the number of living age classes of needles in the tree crowns with increasing latitude was observed. This should be considered if total needle biomass in the crowns is to be estimated from litterfall. A method is proposed for calculating current annual needle litterfall inPinus sylvestrisstands of any age, site quality or latitude in Sweden.

ISSN:0282-7581    

DOI:10.1080/02827588809382521

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The numbers of basal dormant buds and resulting sprouts and their distribution on the stumps of the trees were studied in specimens ofBetula pubescensEhrh. of vegetative and seedling origin of different ages and growing on peatland or mineral soil. The results suggest that the number of buds at the base of the tree varies markedly from one tree to another. The old and young trees had quite similar numbers of buds, but those on mineral soil had less than those growing on peatland. The highest numbers of basal buds were found on sprout‐origin trees. Although about 90% of the basal buds were found below ground level, 1/3 of the sprouts originated from above the ground. This discrepancy can be explained by the formation of bud clusters, since the majority of the sprouts were derived from buds which occurred singly or in very small clusters. The total number of basal buds explains only part of the observed variation in sprouting potential. More important is the formation of bud clusters during the maturation of the tree. The old stumps gave the poorest sprouting results, because their buds were located principally in large clusters. Similarly less sprouts developed on peat soil than on stumps of a corresponding type on mineral soil. The best sprouting ability was observed on the stumps of the trees which had themselves developed vegetatively. The results suggest that sprouting success can be predicted when the location of the buds on the stump is known.

ISSN:0282-7581    

DOI:10.1080/02827588809382522

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Observed diameter distributions of forest stands are adapted to the Johnson Sbprobability function. The stands investigated are untreated mixed stands of Norway spruce(Picea abies(L.) Karst.) and birch(Betula pendulaRoth andBetula pubescensEhrh.) aged between 20 and 32 years. The adaptation of the JohnsonSbprobability function is made both on mixed spruce and birch, and on each species separately. Altogether 156 observations were tested with observed distributions against calculated distributions in the Kolmo‐gorov‐Smirnov test. The fractiles are predicted with multiple regression and two multivari‐ate techniques, simultaneous‐equation models (multivariate regression) and partial least squares with latent variables. The independent variables are characteristics of site and stand. Both multivariate methods predict diameter distribution well when tested.

ISSN:0282-7581    

DOI:10.1080/02827588809382523

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The field‐ and bottom‐layer vegetation changed substantially whenSalixspp. andAlnus incanawere planted, fertilized and irrigated on aSphagnumpeat bog. Of the original peatbog species, onlyEriophorum vaginatumwas favoured. Only 20 of the original 39 peat‐bog species remained after five years. New species likeChamaenerion angustifolium, Epilo‐bium adenocaulonandE. palustreinvaded the bog and became dominant. 20 new species were recorded in the field layer. The change was very rapid and after five years no stabilization could be observed. There was a correlation between the nutritional status of the peat and the composition of vegetation and also between the amount of fertilizers given and the composition of vegetation.

ISSN:0282-7581    

DOI:10.1080/02827588809382524

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

This paper deals with taxation of private, nonindustrial forest owners in Sweden. It includes both theoretical findings and empirical results. In the theoretical analysis it is emphasized why progressive income taxation might influence the supply from individual forest owners. Imperfections in the forest account system in combination with progressi‐vity changes are of importance. If taxation influences the individual supply behaviour, then taxation will most certainly affect the aggregate supply from private, nonindustrial forest owners. This is also supported by the empirical analysis, where it is found that a progressi‐vity increase during a period tends to reduce that period's aggregate supply.

ISSN:0282-7581    

DOI:10.1080/02827588809382525

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Using aerial photographs and a PC (personal computer) based photogrammetric instrument, the author measured landscape features to characterize clearcuts in a “multiple‐use” forest of the outskirts of Oslo, Norway. One hundred and forty‐six clearcuts were examined for area and non‐timber features (such as buffer dimensions and residual vegetation). The results of three dimensional digitized data—captured directly off the stereophotos—created the profiles of clearcuts on private and public land. In addition, the application of PC‐based photogrammetry to natural resource management is discussed.

ISSN:0282-7581    

DOI:10.1080/02827588809382526

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The chemical status within a subset of Swedish forest soils representing Spodosols and acid Entisols and Inceptisols at mesic sites is reported. Three regions which differ in climate and deposition, southwestern (SW), southeastern (SE) and northern (N) Sweden are compared. Most of the soils are located on acid siliceous bedrock. The three regions differ in the percentage of sample plots where the value of a given variable exceeds the mean calculated for the whole country. The order of decreasing frequency in the 0 and B horizons is N>SE>SW for base saturation, calcium saturation and magnesium saturation, and N>SW>SE for potassium saturation. For aluminium saturation the order is SW=SE>N in the 0 horizon and SE>SW>N in the B horizon. The regional difference is especially pronounced with respect to the calcium saturation in the B horizon. The percentage figure is 13, 37 and 45 in SW, SE and N respectively. 33 and 38% of the sample‐plots in SE and N respectively have a calcium saturation <1%of CEC, the corresponding figure for SW being 73%. Different liming criteria and the possible need for forest liming are discussed.

ISSN:0282-7581    

DOI:10.1080/02827588809382527

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Denitrifying enzyme activity (DEA) is defined as N2O production rate over the first eight hours of anaerobic incubation of soil slurries at 15°C with added nitrate and acetylene. Organic fraction explained 81 % of the spatial variation in DEA among soil horizons of beech(Fagus), alder(Alnus), and spruce(Picea)forests, and spruce ciearcuts. Nitrate and pH limit denitrification in anaerobic O horizons at 15°C. Thick, poorly drained O horizons, such as in alder forest, have a high capability for denitrification. Failure to recover all added nitrate in O horizon incubations suggested both production of unmeasured NO and dissimilatory reduction of nitrate to ammonium. In mineral horizons, N2O production was small and could not be increased by increasing nitrate, carbon, pH, and phosphorus; some other factor appears to prevent significant denitrifier activity in acid forest mineral horizons.

ISSN:0282-7581    

DOI:10.1080/02827588809382528

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Seeds from each of six full‐sib families of Norway spruce were separated into fractions of light and heavy seeds. The mean difference in 1000 seed weight between the two lots within families was 1.6 g. The terminal bud‐set after the first growth season was assessed in a nursery test. No significant differences between the seedlings from the light and heavy seed lot fraction within full‐sib families were found. No relationships were observed between the 1000 seed weights of the lots and the mean bud‐sets of their seedlings.

ISSN:0282-7581    

DOI:10.1080/02827588809382529

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor