摘要:

Scots pine(Pinus sylvestris)and lodgepole pine(Pinus contorta)needle litters were compared in terms of nutrient composition and its change during decomposition. Initial nutrient composition differed between the species, with lodgepole pine needle litter having significantly higher concentrations of P, Mg and Mn. However, no difference was found for concentrations of N, Ca or K. Increases in concentrations of N, P and K during decomposition were significant in both litter types. For Ca the pattern of concentration changes followed a quadratic function as decomposition proceeded. Concentrations of Mg and Mn decreased in lodgepole pine needle litter. In Scots pine litter there was also an initial decrease, but it was followed by an increase in most incubations. For both Mg and Mn, changes in concentrations during decomposition differed significantly between species. In the late decomposition stages, concentrations of Mg and Mn became similar in both litter types. Nutrient concentrations generated by the models were compared with those of the humus (F and H) layer in the stands. The model was quite accurate in predicting concentrations of N and P for both species and the concentration of Mg for lodgepole pine. By contrast, it was not accurate in predicting concentrations of Ca and Mn. Nutrient release was estimated for the two species using both measured litterfall data and long‐term estimates, and regression models were used to predict concentration changes. Rates of release of P, Mg and Mn in the lodgepole pine stands were found to be about twice as high compared with those in Scots pine. Calcium was also released to a greater extent although the difference was not significant.

ISSN:0282-7581    

DOI:10.1080/02827589709355392

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Biomass and nutrient dynamics of black spruce seedlings during the hardening phase of the greenhouse rotation were examined after four pre‐hardening fertilization regimes—conventional, constant‐rate loading, exponential loading and high exponential loading (delivering respectively 15, 40, 40 and 60 mg N seedling−1)—in order to assess nutrient dilution and steady‐state nutrition. Although height growth of seedlings had virtually ceased during hardening, shoot biomass increased 99–142% and root biomass increased five‐ to tenfold depending on treatment. The biomass increase compromised steady‐state nutrient status by diluting internal nutrient pools as nutrient supply was unable to keep up with growth. Soil nutrient levels were rapidly depleted during this period because of plant uptake and lack of fertilizer supplementation. Pre‐hardening nutrient loading partly countered and delayed dilution effects, especially when applied exponentially and at high dose levels. Plant nutrient uptake was increased, presumably drawing on residual fertilizer in the rooting media. The higher pre‐plant nutrient reserves in the seedlings are expected to contribute to improved outplanting performance. Sustained steady‐state nutrition in seedlings during hardening may not be achieved by nutrient loading alone, suggesting the need for supplemental fertilization during this period.

ISSN:0282-7581    

DOI:10.1080/02827589709355393

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Populations ofQuercus roburL. andQuercus petraea[Matt.] Liebl. were shown previously to be fixed for the same chloroplast DNA marker in western Europe and for another form of this marker in eastern Europe. Application of this marker to 17 Danish populations ofQ. roburshowed significant population differentiation(GST= 0.6). Restricted gene flow, low effective population size, restricted colonization ability of oak in dense forest and historical data might explain this. In addition, the genetic structure in eastern and western Denmark was quite different. In Jutland the populations were homogeneous for the western marker, in eastern Denmark, significant population differentiation and high diversity within populations were found. Post‐glacial migration is likely to explain the geographical structure. Oaks have immigrated to Jutland from the west, whereas eastern Denmark was colonized from both east and west, forming a hybrid zone where immigrants met. Data from three populations ofQ. petraeaand from two hybrid populations also support this.

ISSN:0282-7581    

DOI:10.1080/02827589709355394

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Height growth, needle mass and needle concentrations of N, P, K, Ca, Mg, and Cu were determined for black spruce(Picea mariana(Mill.) B.S.P.) 2 years, 4 years and 6 years after planting on an ombrotrophic domed bog. Experimental treatments included four ditch spacings (3 m, 5 m, 7 m and 15 m), two surface preparation treatments (tilled, untilled), and 2 fertilization treatments (PK, unfertilized), contained within five blocks. The most effective treatment for early growth of black spruce was a 3‐m and/or 5‐m ditch spacing that had been tilled and fertilized with PK. The effects of tilling alone on growth and nutrient uptake were minimal. However, in many instances, growth was increased by the combined effects of tilling and PK fertilization or tilling and drainage. Fertilization with PK significantly increased needle concentrations of P and K as well as N. Because concentrations of K were above “optimum”; levels, even within the unfertilized treatments, uptake was accounted for by luxury consumption, thereby precluding the need for K fertilization. Thus, improved height growth and needle mass in the PK‐fertilized treatments can be attributed to addition of P, and the subsequent increase in N uptake. Needle concentrations of Mg were slightly increased by PK‐fertilization treatments in 1987. However, over the 6‐year period, concentrations of Ca, Cu, and Mg, were generally not affected by treatments.

ISSN:0282-7581    

DOI:10.1080/02827589709355395

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A site‐index model was constructed based on stem analysis data for 266 top‐height trees ofBetula pendulaRoth andBetula pubescensEhrh. growing on 155 temporary sample plots and 12 remeasured, permanent sample plots in pure and mixed stands scattered throughout Sweden. Different growth functions and techniques for modelling the top‐height growth over breast‐height age were assessed. A difference model based on the Hossfeld IV growth equation performed best, and its practical application was therefore recommended. For birch stands over 40 yrs of age, top‐height growth predicted by the new model was significantly slower than that predicted by a site‐index model used previously.

ISSN:0282-7581    

DOI:10.1080/02827589709355396

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Different reforestation methods were compared in terms of their effect on conifer seedling damage caused by the pine weevilHylobius abietis(L.), seedling survival, and weevil abundance as measured by trapping, during a period of up to 6 yrs after clear‐cutting. Although attack rates on seedlings and seedling mortality differed greatly among sites, attacks were less frequent on plots scarified in the first year after clear‐cutting than in unscarified plots. However, after a fallow period of 2 or 4 yrs, scarification had no effect on attack rates. Mortality due to pine weevils was highest for seedlings planted after 2 yrs and lowest for seedlings planted after 4 yrs. Only small differences in attack rates were found between bare‐root and containerized seedlings. Survival of insecticide‐treated seedlings planted on scarified ground without a fallow period was almost 90% after 3 yrs compared with less than 70% for untreated seedlings. The number of pine weevils caught in pitfall traps in spring of the second year after clear‐cutting was positively correlated with the number of insecticide‐protected seedlings attacked during the first year. ManyH. abietiswere caught in baited traps on clear‐cuttings older than 4 yrs.

ISSN:0282-7581    

DOI:10.1080/02827589709355397

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The susceptibility ofPinus sylvestristo the rusts ofP. contorta—Endocronartium harknessii, Cronartium coleosporioides, and C.comandrae—was determined by an assessment of these diseases in 1993 in five seven‐year‐old experimental plantations in British Columbia and the Yukon in western Canada. After seven years, infection byE. harknessiiwas much higher onP. contortathan onP. sylvestris(27.3% resp. 2.5%). The average number of galls per infected tree was, however, higher onP. sylvestristhan onP. contorta(5.99 resp. 3.61).C. coleosporioideswas uncommon but occurred onP. contortaat all the five sites, while onP. sylvestrisit occurred only at the two southern sites. 28.2% of theP. contortatrees were infected byC. comandraeat one site, but it was recorded only sporadically at the four other sites.P. sylvestriswas slightly affected byC. comandraeat two of the sites.

ISSN:0282-7581    

DOI:10.1080/02827589709355398

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The aim of the study was to establish single‐tree functions to predict crown height, defined as the height from the ground to the attachment of the lowest living branch to the trunk. Data from the Swedish National Forest Inventory 1983–1992 were used to construct country‐wide functions for Scots pine (Pinus sylvestrisL.) and for Norway spruce (Picea abies(L.) Karst.). The model derived was based on the assumption that crown recession in closed forests is caused primarily by lack of light. A crown height function and a relative crown height (crown height/total tree height) function were calculated for each species and were found to predict crown height fairly accurately. Crown height was generally predicted more accurately for Scots pine than for Norway spruce. The crown height functions developed here can be used as an input for predicting the quality of timber. The functions are meant to form part of a system for the long‐term forecasting of timber yields, but they can also be used in calculations of the timber quality of a stand.

ISSN:0282-7581    

DOI:10.1080/02827589709355399

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The objective of forest management planning is often expressed as maximum sustainable economic yield. Methods used to collect information for forestry planning should, therefore, include variables significant for economic evaluations of management alternatives. It is important to be able to differentiate mature stands with respect to timber volumes and species mixture. In this study, digital high‐altitude aerial photographs are tested as a data source for planning. Circular plot data from a forest estate in northern Sweden were used as reference material. Global positioning system (GPS) measurements, with differential correction, were used to georeference the plots. Harvesting priorities were calculated for each plot using the Forest Management Planning Package. Volumes, species mixture and harvest priorities were estimated using regression analysis based on textural and spectral information from aerial photographs. The results show that the dependent variables could be estimated fairly well using only spectral information, e.g.,R2= 0.44 when estimating timber volume at reference plot (10 m radius) level. Aggregated to stand level, the precision was comparable with customary field survey methods (e.g., RMSE= 13.4% for timber volume).

ISSN:0282-7581    

DOI:10.1080/02827589709355400

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The purpose of this study was to examine the use of the non‐parametrick‐nearest‐neighbour method in estimating the basal‐area diameter distribution. Distance‐weighted nearest‐neighbour estimation was based on the similarities of known stand characteristics, e.g. basal area and basal area median diameter, between the target stand and reference stands. The weights for the reference stands were determined using similarity distances. These similarity distance functions were determined by tree species using standardized stand variables. The material of this study consisted of 553 forest stands located in eastern Finland. The accuracy of the k‐nearest‐neighbour method was compared with the Weibull distribution by tree species, using current stand volume characteristics and those that should exist after 10 yrs’ simulation time. The Weibull‐based method was, in most cases, more accurate than the nearest‐neighbour method, but the results were also quite good for thek‐nearest‐neighbour method. Both methods were negligibly biased across the whole material. However, at the extremes of the volume distribution clear underestimates were obtained when using thek‐nearest‐neighbour method.

ISSN:0282-7581    

DOI:10.1080/02827589709355401

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor