Articles containing the keyword 'frost hardiness'.

• Li, Key Laboratory for Silviculture and Conservation, Ministry of Education, Beijing 100083, China ORCID ID: – E-mail: –
• Liu, Key Laboratory for Silviculture and Conservation, Ministry of Education, Beijing 100083, China ORCID ID: – E-mail: lyong@bjfu.edu.cn
• Zhu, Key Laboratory for Silviculture and Conservation, Ministry of Education, Beijing 100083, China ORCID ID: – E-mail: –
• Li, Research Institute of Forestry, Chinese Academy of Forestry; Key Laboratory of Forest Silviculture of State Forestry Administration, Beijing 100091, China ORCID ID: – E-mail: –
• Dumroese, US Department of Agriculture, Forest Service, Rocky Mountain Research Station, Moscow, ID, USA ORCID ID: – E-mail: –

• Luoranen, The Finnish Forest Research Institute, Suonenjoki Research Unit, FI-77600 Suonenjoki, Finland ORCID ID: – E-mail: jaana.luoranen@metla.fi
• Konttinen, The Finnish Forest Research Institute, Suonenjoki Research Unit, FI-77600 Suonenjoki, Finland ORCID ID: – E-mail: –
• Rikala, The Finnish Forest Research Institute, Suonenjoki Research Unit, FI-77600 Suonenjoki, Finland ORCID ID: – E-mail: –

• Hänninen, Plant Ecophysiology and Climate Change Group (PECC), Department of Biological and Environmental Sciences, Box 65, FI-00014 University of Helsinki, Finland ORCID ID: – E-mail: heikki.hanninen@helsinki.fi
• Kramer, Alterra, P.O. Box 47, 6700 AA Wageningen, The Netherlands ORCID ID: – E-mail: –

Two dynamic models predicting the development of frost hardiness of Finnish Scots pine (Pinus sylvestris L.) were tested with frost hardiness data obtained from trees growing in the natural conditions of Finland and from an experiment simulating the predicted climatic warming. The input variables were temperature in the first model, and temperature and night length in the second. The model parameters were fixed on the basis of previous independent studies. The results suggested that the model which included temperature and photoperiod as input variables was more accurate than the model using temperature as the only input variable to predict the development of frost hardiness in different environmental conditions. Further requirements for developing the frost hardiness models are discussed.

• Leinonen, ORCID ID: – E-mail: –
• Hänninen, ORCID ID: – E-mail: –
• Repo, ORCID ID: – E-mail: –

The relationships between bud dormancy and frost hardiness were examined using two-year-old Pinus sylvestris L. seedlings. The chilling temperatures used were +4 and -2°C. To examine the dormancy release of the seedlings, a forcing technique was used. Frost hardiness was determined by artificial freezing treatments and measurements of electrical impedance. At the start of the experiment, the frost hardiness of the seedlings was about -25°C. After the rest break, the seedlings kept at +4°C dehardened until after eight weeks their frost hardiness reached -5°C. At the lower chilling temperature (-2°C) the frost hardiness remained at the original level. When moved from +4 to -2°C, seedlings were able to reharden only after the time required for bud burst in the forcing conditions had reached the minimum.

The PDF includes an abstract in Finnish

• Valkonen, ORCID ID: – E-mail: –
• Hänninen, ORCID ID: – E-mail: –
• Pelkonen, ORCID ID: – E-mail: –
• Repo, ORCID ID: – E-mail: –

Seven hundred one-year-old Betula pendula Roth seedlings were given different concentrations of potassium fertilizer. Over the study period seedlings were subjected to artificial growing and dormant phases. Frost resistance of the seedlings was assessed by artificial freezing tests and electrical impedance measurements on stem cuttings. In general, high concentrations of potassium fertilizer reflected a low tolerance to frost. Pre-freezing impedance readings decreased with increasing potassium fertilizer dosages. Results from pre-freezing impedance measurements were found to be in broad agreement with the hypothesis that high impedance readings indicate a frost hardy tissue whereas low readings imply the opposite.

The PDF includes an abstract in Finnish.

• Jozefek, ORCID ID: – E-mail: –

Nursery grown Norway spruce (Picea abies (L.) H. Karst.) seedlings from 12 different seed orchards were tested for early autumn frost hardiness using artificial freezing tests. Seed orchards containing grafted parent clones originating from high altitudes produced seedlings showing higher damage than commercial control seed lots of the commercial controls. A seed orchard containing both German and Norwegian clones produced seedlings showing high damage. The correlation between bud-set and frost damage was high at the provenance level, but lower at the half- and full-sib-levels. Families with good growth capacity in progeny field tests showed large between-family variation in frost damage in the artificial freezing tests. This indicates the possibility to combine high growth rate with acceptable autumn frost hardiness in the selection of parent trees.

The PDF includes an abstract in Finnish.

• Johnsen, ORCID ID: – E-mail: –
• Apeland, ORCID ID: – E-mail: –

Visible frost damage to forest trees in Sweden seldom occurs in winter but is frequent in late spring, summer and early autumn. Frosts are frequent in all seasons in various parts of Sweden, even in the southernmost part (lat. 56°, N) and temperatures may be as low as -10°C even around mid-summer. Ice crystal formation within the tissues, which in most seedlings takes place at around -2°C, causes injury, not the sub-zero temperatures themselves.

The apical meristem, the elongated zone, and the needles of seedlings of Picea abies (L.) H. Karst. in a growing phase were damaged at about -3°C and those of Pinus sylvestris L. at about -6°C. Other species of the genus Pinus were tested and most were found to be damaged at about -6°C, with some variations. Picea species tested were damaged at about -3°C to -4°C.

A method has been designed to compare the response of different species to winter desiccation, which occurs under conditions of (1) low night temperature, (2) very high irradiation and increase in needle temperature during the photoperiod, (3) frozen soil, and (4) low wind speed. There were differences in response to winter desiccation between pine and spruce species. Seedlings of Pinus contorta tolerated these winter desiccation conditions much better than those of P. sylvestris or Picea abies. Picea mariana was the least tolerant of the species tested.

The PDF includes an abstract in Finnish.

• Christersson, ORCID ID: – E-mail: –
• Fircks, ORCID ID: – E-mail: –

This issue of Silva Fennica consists of eight articles, which are based on a co-nordic conference ”Frost hardiness and over-wintering in forest tree seedlings”, held in Joensuu, Finland, during December 1–3, 1986. The whole annual cycle of the trees is considered. Emphasis is given on methods for the study of frost hardiness, genetic variation in frost hardiness, nitrogen metabolism, bud dormancy release, and joint effect of natural and anthropogenic stress factors in the winter damage of forest trees. Practical implications for tree breeding and nursery management are discussed.

The PDF includes an abstract in Finnish.

• Hänninen, ORCID ID: – E-mail: –
• Pelkonen, ORCID ID: – E-mail: –