Articles containing the keyword 'spring frost'

The distribution of the minimum temperatures after the beginning of the active period (one temperature for each spring) have been calculated for each principle using daily meteorological data collected during the years 1883–1980. The efficiency criterion is the variance of the minimum temperature distributions and the length of the active period. The most efficient regulation principle is found to be based on the temperature sum which includes a feedback component.

The PDF includes a summary in Finnish.

• Häkkinen, E-mail: rh@mm.unknown
• Hari, E-mail: ph@mm.unknown

The aim of the investigation was to study natural regeneration of Norway spruce (Picea abies (L.) Karst.) in drained peatlands and frost injuries in seedlings, and to compare microclimates of the regeneration areas. The experiments included peatlands in Satakunta in Western Finland. Restocking of the areas with seedlings and their survival was followed in 1935-40 at sample plots that were mainly 1 are large.

Susceptibility to freezing was shown to be dependent on the stage of development of the shoots. Shoots that have just begun to grow contain little water, and withstand better freezing temperatures than shoots in later stages of growth. Damages to the seedlings were observed when the temperatures decreased to -2.8–-4.3 °C. The most severe damage to a seedling was caused by the death of the leading shoot by spring frost.

Norway spruce regenerates easily on moist peatlands, but peatlands with dry surface tend to have little or no seedlings. The species regenerated better in marshy sites than correspondingly fertile mineral soil sites. However, it needs shelter to avoid frost damage. On clear cut spruce swamp the undergrowth spruce seedlings that were left in the site got severe frost damage. If the site had birch (Betula sp.) coppice or undergrowth, spruce seedlings survived in their shelter depending on the height and density of the birch trees. To be effective, the protective forest should have relatively even crown cover. Young spruce seedlings could grow well even under relatively dense birch stand.

The PDF includes a summary in German.

• Multamäki, E-mail: sm@mm.unknown