摘要:

The concentration of live fungal biomass (FDA mycelium) was investigated in seven chemically very different litter types, i.e. grey alder leaves, green and brown leaves of white birch, green and brown needles of both Scots pine and lodgepole pine. Concentration of FDA mycelium in the litters changed with the season, being low during the dry late summer and relatively higher during the more rainy, wet autumn. During autumns, when moisture was not limiting, lignin concentration and live fungal biomass were negatively related. It was concluded that the concentration of live fungal biomass in litter decreased linearly as the lignin concentration increased and thus also decreased linearly to decomposition level of the litter.

ISSN:0282-7581    

DOI:10.1080/02827589109382682

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Variation of sapwood thickness in terms of a linear measurement and a growth ring count with reference to the age was studied in dominant and suppressed Norway spruce trees. In the trees of both dominance classes the sapwood thickness increased in absolute terms, while its relative portion decreased with the age of the trees growing. Great differences were found in sapwood thickness between dominant and suppressed trees in linear measurements but not in the number of sapwood rings or the rate of the heartwood formation. The number of sapwood growth rings reached 40 in old trees. The index of vigour differed considerably in dominant and suppressed trees.

ISSN:0282-7581    

DOI:10.1080/02827589109382683

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The allelic constitution of 169Populus deltoidesMarsh, clones, selected in North America, was studied at 8 marker allozyme loci (Aco‐2, Mdh‐2, Pgi‐2, Pgm‐1, Pgm‐3, 6‐Pgd‐2, 6‐Pgd‐4and6‐Pgd‐5) coding for 5 enzyme systems in root tips. The enzymes were assayed by horizontal starch gel electrophoresis. An examination of the allozyme profiles revealed that twenty‐seven of these selections (16%) were misidentified asP. deltoides.Eighteen of the misidentified selections displayed isozyme genotypes and patterns typical ofP. deltoidesxP. higraL. hybrids (P.xcanadenisMoench) and the remaining nine selections typical ofP. deltoidesxP. balsamiferaL. (P.xjackiiSarg.). The results indicated a need for screening North AmericanP. deltoidesselections used for plantation, breeding, and biological studies to assure their accurate species identification. Allozyme markers can be of potential importance in detecting misidentifiedP. deltoidesspecimens and in ascertaining their correct species identity.

ISSN:0282-7581    

DOI:10.1080/02827589109382684

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Under certain environmental conditions, juvenile shoot growth characters might give early indications of adaptability and growth potential. Therefore, the reaction patterns of predetermined and free shoot growth were studied onPicea abies(L.) Karst, plants, which at different times during the growth period were treated by (1) application of nutrients, (2) defoliation, and (3) short days. Fertilization caused an increase in both predetermined and free growth, while defoliation and short day treatment caused a decrease in both forms of shoot growth and short days did not allow any free growth to occur. In the growth period following the treatments, fertilization caused more predetermined and less free growth to occur, while defoliation caused less predetermined and more free growth. Predetermined growth is explainable by the finite number of predetermined needle primordia. Free growth is initiated thereafter. It is influenced strongly by the environmental conditions and seems not to be influenced by the amount of preceding predetermined growth. Free growth enables young plants to utilize favourable growth conditions in summer for height growth precociously, which might increase their adaptability and competitive value. However, predetermined growth is the preferable mode of shoot growth because favourable conditions in successive growth periods induce more predetermined than free growth. Predetermined and free growth are well integrated forms of shoot growth giving no supporting evidence to the hypothesis that free and predetermined growth are inherited independently of each other. Rank changes in provenance development are probably not explainable by a loss in height growth when free growth occurs no more due to age, but by other causes.

ISSN:0282-7581    

DOI:10.1080/02827589109382685

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The study material consists of the data collected from an experiment established on moist mineral soil in southern Finland. Naturally established Norway spruce‐dominated(Picea abiesL. Karst.) sapling stands had been treated in four different ways. The growing stock was measured at the stage of the first commercial thinning. On considering aspects of economy, biology and the worsening of the state of the environment, the best result was obtained when the sapling stand was left untreated. The second best option was a treatment according to which a certain basic growing stock consisting of some hundreds of good quality and more vigorous individuals were liberated’ from the competition, i.e. point cleaning. The cleaning‐thinning treatment of sapling stands, as practised today, was clearly less beneficial than the above treatments.

ISSN:0282-7581    

DOI:10.1080/02827589109382686

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Altogether 1 080 two‐year‐old silver birch(Betula pendulaRoth) were planted in groups of 36 plants at aspacing of 20 x 20 Cm in spring 1983 on a nursery field at lat. 60ˆ 15 N and long. 16ˆ00 E. In spring 1984 all plants were cut with 10 cm high stumps and light screens were arranged on the stump groups. Relative ¡rradiance (RI) 5, 10, 25, 50, 75 and 100% of full sunlight were used. After five growing seasons, all stumps exposed to 5 or 10% light intensity were dead, and 64–94% of stumps exposed to 25–100% RI were alive. 1.3–1.4 sprouts per living stump were living five years after cutting. The mean height of sprouts was highest on stumps exposed to 100% light. Also dry weights of leaves and sprouts, number of leaves per sprout, and leaf area were highest on stumps exposed to full sunlight. Stumps producting only one sprout five years after cutting have higher height and dry weight values than stumps with more sprouts. The biomass production per hectare and year for silver birch sprouts at a spacing of 0.2 m and with 90% survival was calculated as 5.4 tonnes. The biomass of leaves was 8.1 tonnes/ha/year five years after cutting.

ISSN:0282-7581    

DOI:10.1080/02827589109382687

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A pine forest in the south of Sweden was treated with lime and wood ash. In early June, 12 months after the ash treatment and 18 months after the lime treatment, one year oldPinus syhestrisL. seedlings were planted. Four months later six différent ectomycorrhizal types had infected the seedlings in all the treatments. A mycorrhizal type designated “pink”; was more than twice as common in the lime treatments as in the control and ash treatments.Piloderma croceumErikss. & Hjorts. was significantly more abundant in limed soil than in ash treated soil. The results were compared to those from a bioassy performed in the laboratory, whereP. syhestrisseedlings had been grown in soil from the same forest. Similar soil pH values in the two studies resulted in different relative infection rates of the mycorrhizal types found. One additional mycorrhizal type, designated “white”; was found in the field experiment. This suggests that mycelial connections to the mature host plants may significantly alter the ability of different fungi to colonize host plant roots in competition with each other compared to when the fungi infect from propagules in the soil.

ISSN:0282-7581    

DOI:10.1080/02827589109382688

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The study deals with the structure of advanced virgin forests in Finland based on the national forest inventory carried out in the 1920's. At that time, virgin forests covered 2/3 of the forested area of Finland. Stand structure was described in terms of the d.b.h. distribution. The study material consisting of 10 x 50 m sample plots was grouped according to geographical region, site type and the age class of the overstorey. A stand was classified to be advanced if the age of the overstorey was at least half of the currently applied rotation age and if the stem volume exceeded 40 m3/nectare. About 60% of all virgin forests (i.e. 932 sample plots) were classified to be advanced. In the 1920's. the majority of advanced virgin forests were mixed stands with an all‐sized structure. Trees of small diameter prevailed and the stem number diminished rather steadily with increasing d.b.h. Even‐sized stands with a d.b.h. range of 15 or 20 cm and a normally distributed diameter frequency accounted for only 10 sample plots (i.e. about one percent). The stand structures described in this study can be used as models when developing so‐called natural silvicultural regimes. This concept includes methods for maintaining and developing the growing stock as a mixed stand all‐sized in structure.

ISSN:0282-7581    

DOI:10.1080/02827589109382689

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Patterns of host plant utilization of the pine resin gall mothRetinia resinellain a young Scots pine stand were studied along a belt transect in southeastern Finland. The gall distribution in 1984–1989 was retrospectively analysed. The moth preferred leaders to lateral shoots. In 1984, 60% of the galls occurred on the leaders, while the respective proportion was 40% in 1986 and 38% in 1988. The mean height of pines attacked by the moth changed from 74 to 127 cm. In 1984, moth galls on leaders occurred on higher and better‐growing trees than the average, while the opposite was true in 1988. There was an indication of clumping ofR. resinella, with clumps spaced about 20 m apart which may be‐due to microhabitat distribution, the behaviour of ovipositing females or spatial dynamics of predators. The galls occurred more frequently on trees with a previous year's gall, but this tendency was not observed in the leader galls. The results support the view that the pattern of host plant utilization by a herbivore may profoundly depend on the successional stage of the habitat.

ISSN:0282-7581    

DOI:10.1080/02827589109382690

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

An optimal control theory model for the determination of optimal harvest and inventory is shown initially. The second part uses some aggregate data from Norwegian forestry to illustrate how the theory could be applied in the elaboration of a national forest policy. Finally the practical implications are discussed in relation to the social discount rate, industrial capacity and environmental concerns.

ISSN:0282-7581    

DOI:10.1080/02827589109382691

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor