摘要:

Ten mor cores (O‐horizon) were sampled every month during September 1985 to August 1986 (except December) from a 9 m2plot. Each core usually yielded four sliced 1‐cm‐layers in addition to the S‐layer. Each layer was extracted in both distilled water and in 0.01 M CaCl2The spatial pH variation was found to be greater than the seasonal variation in all layers. With few exceptions, pHH2Oand pHCaCl2showed a similar seasonal trend in the entire mor layer. Seasonal alteration of chemical or biological conditions generally influenced pH of all cm‐layers in the same direction. The general seasonal trend of pHH2Oand pHCaCl2was a‐continuous increase during autumn and winter, with a maximum in April, followed by a more drastic decrease and a pHH2Ominimum in June. The minimum pHCaCl2appeared in August. Cation uptake (May‐June) and mineralisation, leaching and alteration of organic acid properties (September‐April, July‐August) were discussed as the dominating factors behind the seasonal pH variation.

ISSN:0282-7581    

DOI:10.1080/02827589109382642

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The soil acidity of four coniferous sites, two in S Sweden and two in N Sweden, were studied 7–9 years after clear‐felling. Each site had three different slash treatments; (a) all slash harvested,(b)only needles remaining, and (c) all slash remaining. Our results verify that harvesting of slash after clear‐cutting means an acidification of the organic horizon in acid forest soils. On plots subjected to full slash harvest the pH‐value of the forest floor was 0.2–0.4 units lower than that of slash‐covered ones, and at three of the four study sites the exchangeable acidity was significantly higher on the slash‐cleared plots. Plots with only needles remaining were generally intermediate in acidity. The change in exchangeable acidity corresponded to approximately 10% of the theoretically estimated proton load caused by slash harvesting. The rate of proton flux associated with whole‐tree harvesting varied between 7–65 meq m‐3yr‐1, which roughly corresponds to the amounts deposited in precipitation. Harvesting of stems accounted for about one third and needles for one third of the proton load.

ISSN:0282-7581    

DOI:10.1080/02827589109382643

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Autumn colouration, dry matter content and frost hardiness ofPinus sylvestrisseedlings were monitored during their first autumn. Seedlings of southern (62° N, 24° E) and northern (67° N, 26° E) Finland origin were grown under two fertilization regimes in Suonenjoki (63°N, 27°E). Northern seedlings turned purple earlier than southern ones, and low fertilized earlier than normal fertilized. Northern seedlings also hardened earlier than southern ones, while fertilization had no effect on hardening. Neither purple autumn colour nor dry matter content was clearly related to frost hardiness of seedlings when treatment means were compared. Comparison of seedlings within treatments suggested, however, that purple seedlings had higher dry matter content than green seedlings at the beginning of hardening period but the relationship between colouring and frost hardiness was not clear.

ISSN:0282-7581    

DOI:10.1080/02827589109382644

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Scots pine(Pinus sylvestrisL.) seeds were induced to germinate by a 15 min red light (R) treatment after a 5 h wet incubation in the dark. Controls, irradiated with 15 min R immediately followed by far‐red light (FR) for 5 min. were run in parallel. Cytokinins of the zeatin riboside type were quantified at the first, second and third day after the light treatment. The cytokinin determination was carried out with an enzyme‐linked immuno‐sorbent assay (ELISA) with polyclonal antibodies raised againsttrans‐zeatin riboside (ZR). Evidence for the occurrence of ZR in the extract was further established by high performance liquid chromatography (HPLC) of samples purified on immunoaffinity columns. The short pulse of R led to a transient increase in endogenous ZR‐type cytokinins on the second day whereas there was no marked change during the time course after FR treatment. It is suggested that the ZR‐type cytokinins were involved in the regulation of incipient growth activity taking place after the period of germination in astrict sense.

ISSN:0282-7581    

DOI:10.1080/02827589109382645

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0282-7581    

DOI:10.1080/02827589109382646

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A variety of terms are used in evaluation of planting stock: phrases including the term ‘quality’ appear most frequently, while ‘attribute’, ‘vigour’, ‘vitality’ and ‘viability’ are also used. These terms are defined and discussed, and it is argued that the commonly used nursery tests assess the seedlings at the level of ‘viability’.

ISSN:0282-7581    

DOI:10.1080/02827589109382647

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Photosynthetic performance and root respiration were measured for seedlings of Scots pine and Norway spruce under constant conditions in an open gas exchange system in the laboratory. Measurements were carried out after root exposure to ‐20, ‐5 and 0°C and subsequent longtime storage in darkness at +1 or +4°C. Stomatal conductance in relation to net photosynthetic rates was also investigated after the same treatment of seedlings. Root respiration was low for seedlings whose root system had been exposed to ‐20°C, Scots pine showing lower rates than Norway spruce. This was probably an indication of root damage. At least for one provenance of Scots pine, respiration rates were higher for seedlings stored at +1 than at +4°C. Photosynthetic performance was also lowest for seedlings whose roots had been exposed to +20°C compared to higher temperatures, the difference being more clear‐cut for Norway spruce than for Scots pine. Storage at +1 gave slightly higher photosynthetic rates than at +4°C. There was a close relation between stomatal conductance measured on individual needles and photosynthetic performance measured on the whole seedling.

ISSN:0282-7581    

DOI:10.1080/02827589109382648

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Cold stored, one‐year‐old Norway spruce seedlings were manipulated to obtain seedlings with different viabilities. Either half or whole root systems were submerged in boiling water for five minutes, or 40 or 75%of the shoot volume was cut away. The seedlings were grown in a climate chamber, and transpiration rates were estimated daily for 20 days after treatment by weighing individual seedlings. Rates of transpiration and photosynthesis were also measured by porometry after 20 days. Root and shoot growth was assessed after 21 days. Buds of treated seedlings broke earlier than the buds of untreated ones. The transpiration rate increased with time for the undamaged seedlings, while the severely damaged seedlings transpired at a uniform low rate throughout the experiment. Root growth capcity Failed to detect the different magnitudes of root damage, whereas the reduction in both transpiration and photosynthesis rates did. Transpiration rates estimated by weighing correlated linearly with those measured by porometer after 20 days, and both correlated with the rate of photosynthesis and the shoot volume. Also, the dry weight of roots grown during the experiment (root growth capacity) correlated significantly with the rate of photosynthesis.

ISSN:0282-7581    

DOI:10.1080/02827589109382649

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Effects of soil temperature on gas exchange of Scots pine seedlings were studied to evaluate the significance of reduced gas exchange in seedlings planted in cold soils. The patterns of net photosynthesis during the 3‐week period at the two constant soil temperatures (8°C and 12°C) were quite similar but at 12°C the photosynthetic rate was higher. After U days differences were no more significant. Photosynthesis at the increasing soil temperature, from 5.5°C to 13°C, decreased for the first 18 days and then recovered up to the level of other treatments. The same patterns were found for transpiration, stomatal conductance, and photosynthetic efficiency. Xylem pressure potentials and relative resistance to water flow after 3 weeks did not differ among soil temperatures. Initiation and development of current‐year needles affected all the results of gas exchange parameters.

ISSN:0282-7581    

DOI:10.1080/02827589109382650

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Norwayspruceseedlings were grown in 50 ml pots, and irrigated when 30, 50, 70 and 90% of the liquid held at container capacity was left in the substrate. The total volume of nutrient solution added was smallest in the irrigation regime with the most frequent irrigation, and increased with decreased irrigation frequency. This was an effect of increased leaching with decreased irrigation frequency. Within each irrigation regime, the transpiration rate of the highest transpiring seedling was three times that of the lowest transpiring one. The transpiration rate was linearly related to shoot volume, independent of irrigation regime for approximately 50 days. Thereafter, the relationship became curvilinear and more affected by irrigation regime. The deviation from linearity was ascribed to an increased stomatal resistance when the growth substrate became drier. Towards the end of the experiment, the seedlings subjected to the most frequent irrigation transpired on a per seedling basis approximately four times more than seedlings subjected to the least frequent irrigation. Even on a shoot volume (or shoot dry weight) basis the transpiration was 2.5 times higher for seedlings with the most frequent irrigation compared to the ones in the least frequent irrigation. In conclusion, frequent irrigation with small volumes could be a way to reduce the risk for individual seedlings to experience the extreme conditions of drought and drowning, which could be one way to grow more uniform seedlings. Besides, the reduced drainage should reduce the pollution hazards, and more nursery resources could be converted to nursery products.

ISSN:0282-7581    

DOI:10.1080/02827589109382651

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor