摘要:

The effects of photoperiod and thermal time and their interaction on the timing of growth cessation were examined in seedlings of Scots pine (Pinus sylvestrisL.) in greenhouses with 20°C day and 10°C night temperatures combined with the natural development of the photoperiod. Sowing was repeated five times during both 1995 and 1996 using origins from different altitudes and latitudes (>60°N) in Sweden and Finland. In this way, gradients in temperature sums at a nearly constant photoperiod and different photoperiods at constant temperature sums were obtained. After the first growing season the timing of growth cessation of seedlings from different origins was flexible, i.e. it was determined by the specific combinations of accumulated temperature sum and night length illustrated by fitted straight lines. The photoperiod at the site of origin was a dominant factor in determining the timing of growth cessation in origins from northern latitudes. Because of predetermined growth, the sowing date did not affect the phenology during the second growing season.

ISSN:0282-7581    

DOI:10.1080/02827589908540813

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Abundant flowering occurred in a central Swedish trial with 10-yr-oldPicea abiesL. (Karst.) cuttings, taken on 4-yr-old seedlings. Large deviations in cone-set between clones were assumed to reflect different stages in transition from juvenile to flowering competent phase. Rooting success and first-yr growth performance (leader length, leader origin and plagiotropic growth) were studied on cuttings originating from the upper and lower parts of the crown in 15 clones with heavy cone-set and 15 clones without cones. Twigs from the lower part of the crown had a significantly higher rooting percentage. Cone-set did not have an effect on any of the variables analysed. The results suggest that flowering ability and rooting capacity are independent age-related processes, implying that selection for high rooting capacity in clonal forestry does not reduce flowering competence. The results will have a great impact on breeding ofP. abies,since both early flowering and high rooting ability are important traits for reducing the turnover time of the breeding cycle.

ISSN:0282-7581    

DOI:10.1080/02827589908540814

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The spatial distribution of windthrows and dead-standing trees as well as the occurrence of two bark beetle species,Ips typographusandTomicus piniperda,were studied at forest-clearcut edges in southern Finland. More than 80% of the recorded dead trees were situated within the first 15 m from the clearcut border. The number of dead-standing spruces attacked byI.typographusdid not depend on the amount of windthrows at the same site. According to logistic regression analysis, the distance from a clearcut border had a negative effect on the likelihood ofI.typographusbeing present in the windthrows. The results indicate that windthrows do not necessarily increase bark beetle-induced tree mortality under endemic wind conditions. The accumulation of dead trees at forest-clearcut edges may support the diversity of saproxylic species, but may also maintain populations of harmful bark beetles under non-epidemic conditions.

ISSN:0282-7581    

DOI:10.1080/02827589908540815

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The influence of site preparation and reforestation method on the performance of Scots pine(Pinus sylvestrisL.) was followed during 16 growing seasons in northern Finland using a split-plot design in randomized blocks. The site-preparation methods were prescribed burning (BURN), patch scarification (PATCH), disk trenching (DISK) and ploughing (PLOU). The reforestation methods were sowing (SOW) and planting with containerized seedlings (CON) and bare-rooted transplants (BARE). The reforestation was repeated in three successive years. A total of 72000 reforestation spots was sown or planted on the 288 plots using the reforestation density of 2500 spots ha–1. Four of the eight clear-cut forest sites were dryish pine-dominated sites and four were moist, formerly Norway spruce-dominated sites. After 16 growing seasons, average survival was 49% on the pine sites and 33% on the spruce sites. Site preparation significantly affected survival on the spruce sites (PLOU 44%>DISK 23%) but not on the pine sites. The reforestation method had a significant effect only on the pine sites (CON 58%)>SOW 36%). The effect of site preparation on mean height was significant on the pine (BURN 271 cm>DISK 222 cm) and spruce sites (PLOU 269, BURN 256 cm>DISK 212 cm). The differences between the reforestation methods were highly significant on the pine (BARE 295 cm>CON 261 cm>SOW 186 cm) and spruce sites (BARE 309 cm>CON 255 cm>SOW 171 cm). The results of this study indicate that different site-preparation methods can be used successfully in Scots pine reforestation on dryish, formerly pine-dominated sites in northern Finland. Intensive site-preparation methods, such as ploughing or mounding, are needed if Scots pine is to be established on moist, formerly spruce-dominated sites. However, the low survival and wide variation in survival indicated that there is a high risk of failure on such sites.

ISSN:0282-7581    

DOI:10.1080/02827589908540816

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Fine-root production and turnover were estimated in a short-rotation stand of basket willow (Salix viminalisL.) in central Sweden. Different calculation methods, based on soil coring, or combinations of soil coring and minirhizotron technique, were used. Fine-root biomass production and mortality in the 0–50 cm soil horizon were estimated at 900–7200 kg ha−1yr−1and 500–6800 kg ha−1yr−1, respectively, depending on the method used. Corresponding values for production and mortality of fine-root length per unit soil volume were 160–1600 dm dm−3yr−1and 40–1500 dm dm−3yr−1, respectively. Methods based on soil coring alone gave the lowest estimates, and probably underestimated production and mortality, since both processes to a high degree occurred simultaneously in the willow plantation. Thus, this study emphasizes the necessity to separate the processes of growth and decay where high fine-root turnover occurs.

ISSN:0282-7581    

DOI:10.1080/02827589908540817

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Sedimentary phosphorus, superphosphate, and wood-ash, as well as either sedimentary phosphorus, superphosphate or ash combined with lime, were distributed in selected plots in an 80-yr-old Norway spruce forest [Picea abies(L.) Karst], After 2 yrs, the sedimentary phosphorus had increased the oxalate/oxalic acid-extractable P in the O-horizon, and the superphosphate had increased the oxalate/oxalic acid-extractable P in the E-horizon. At first, the percolation water from the superphosphate treatment showed high P concentrations. It soon returned to control levels, however. The percolation water from the sedimentary phosphorus treatment gradually showed increased phosphate concentrations. The wood-ash increased neither the amount of extractable P nor the P concentration in the percolation water. The oxalate/oxalic acid-extractable P from the sedimentary P treatment was reduced by liming. The P concentration in the percolation water also tended to be reduced. This was perhaps due to formation of Ca phosphates in the vicinity of the lime particles. In addition, if the solubility rate was similar to the uptake rate, it could account for the decreased P concentration.

ISSN:0282-7581    

DOI:10.1080/02827589908540818

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A suitable method based on gas chromatography to detect the diphytanylglycerol diether (archaeol), the domain membrane lipidof Archaea,was used to trace the presence ofArchaeain humus and peat. The elution of the standard used (1,2-di-O-hexadecyl-rac-glycerol) was reproducible above a concentration of 1 mg 1−1(2 ng peak−1), which was the detection limit of the method. No archaeol was detected from the humus sample. This was verified using polymerase chain reaction (PCR) with primers specific toarchaeal16S rDNA gene region. Spiking the humus with an archaeon,Halobacterium salinarum,gave a positive response for both methods. This indicated that there were noArchaeain the specific humus sample. The peat samples used for extraction of diether lipids were first characterized for their CH4production rate, which indicated the presence of methanogens(Archaea).With unlimited access to CO2/H2, the methane production rate peaked between 15 and 25 cm. The archaeol could be identified from all depths sampled. The maximum archaeol concentration was at 20 cm, indicating the highest methanogenic population density at this depth. This is in accordance with the results from the methane production estimates.

ISSN:0282-7581    

DOI:10.1080/02827589908540819

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Transect relascope sampling is a recently proposed method for making efficient inventories of coarse woody debris on the ground. However, before the method can be recommended, its performance in the field requires investigation. This paper presents the results of a field study in which 11 surveyors tested the method in two coniferous stands in northern Sweden. The average bias introduced by the surveyors was moderate under normal sighting conditions, but underestimation was substantial when combining a small relascope angle with poor sighting conditions. In all cases, the differences between the systematic errors of individual surveyors were substantial. The conclusion is that transect relascope sampling is not an appropriate method when the demand for unbiased estimates is high, e.g. in connection with long-term monitoring, but that the method can be useful as a first phase in double sampling or in ocular-based inventories aimed at identifying biologically valuable areas.

ISSN:0282-7581    

DOI:10.1080/02827589908540820

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A 717 ha forest area dominated by Norway spruce [Picea abies(L.) Karst.] and Scots pine [Pinus sylvestrisL.] was used to assess the effects of photointerpreter errors in the placement of stand boundaries on the estimated area of different groups of forest stands (strata) and other land use classes, and on the total timber volume estimate of the forest. The boundaries between thinning phase stands and clearcuts were classified into three different groups according to the length of the tree shadows hindering ground visibility in the aerial photographs. Different distributions of errors in stand boundaries were assigned to the three groups of boundaries. By means of Monte Carlo simulations of errors in each boundary, the placement of each boundary was altered according to a normally distributed random deviate. In total, 125 independent estimates of total timber volume and area of different land use classes were produced. For thinning phase forest, the difference between the mean area of the simulations and true area was –2.0% of true area. The corresponding difference for total timber volume of all stands was –2.1%. For individual simulations, the minimum and maximum biases in timber volume were –4.8% and 3.1%, respectively

ISSN:0282-7581    

DOI:10.1080/02827589908540821

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A methodology is presented which solves local management problems by combining a timber procurement model with decision analysis and heuristic optimization. A hierarchical participatory method resolves the difficulties of the timber-flow model based on dynamics and system balance theories applying to the tactical management process of policy selection. The methodology was developed for team/group decision-making on the assumptions of bounded rationality, imperfect mill service information and lagged inventory adjustment. The experiments analyze the logistics of timber-flow changes. Although the most important objective of the tactical policy of an organization has been to satisfy the timber demand of the mills at minimum cost, the work group in this study was also able to decide utilizing the criteria of the mill service: (1) local managers responsible for transportation preferred a larger roadside inventory slock; and (2) a manager responsible for supervision of logistics preferred a higher level of aggregate inventory turnaround. In the first participatory stage of the method, the criteria for aspiration levels, which determined the group managers’ goal as a combined aspiration point, were described. In the second stage, to avoid problems, participatory inventory models and a decision boundary were used in the management process, in this tradeoff analysis, heuristics provided equal hierarchical consideration and commensurate goals. Since the experiments showed that consideration of local managers’ needs in predicting feasible buffer stocks may reduce possible conflicts in decision-making, the applied theories and the methodology of this study were useful in establishing balanced policies for tactical management situations

ISSN:0282-7581    

DOI:10.1080/02827589908540822

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor