Metla Project 3231

Adaptation of the sexual reproduction of trees to climatic change

Duration: 1998-2002 Keywords: bud-burst, cessation of growth, critical night length, male flowering, pubescent birch, silver birch, temperature sum

Objectives

The main objects of the project were to study
- adaptation of the Finnish tree species to the annual cycle
- sensitivity of trees to the temperature and light factors as seedlings and as mature trees
- quantification of the onset of the annual cycle
- cessation of growth period.

During the project these objects were tried to achieve by investigating the susceptibility of flower buds and seeds to wintertime damage due to low temperatures. Also responses of the adaptation process and flower abundance to climatic change were studied. Each provenience was compared to other origins at each locality and the responses to climatic factors were observed. Changes in probabilities of successful generative reproduction were also evaluated. The main research question to answer was, will a change in the annual cycles of generative processes occur more readily than within the annual cycle of vegetative growth?

Results

Phenology of finnish tree species was studied: Häkkinen (1999) studied leaf bud-burst of birch species using long time series of observations published, Luomajoki (1999) studied timing of male flowering in pubescent birch and silver birch by means of pollen recording data and Linkosalo (2000) utilized time series of flowering or leaf bud-burst in seven tree species. Studies by Häkkinen and Linkosalo were based on already published observations processed by statistical methods. Study of Luomajoki uses solely pollen data recorded at Metla by pollen recorders and subsequently treated statistically.

In all studies above initiation of development in the spring was considered to commence by a fixed calendar date that corresponds a light signal received in nature. In study by Häkkinen birch species could not be specified but Luomajoki found a considerable ecophysiological difference in the timing of male flowering between pubescent birch and silver birch. On the other hand Linkosalo concluded that all of the seven time series derived from different tree species could be treated with identical methods.

Partanen (2004) studied onset and cessation of growth in seedlings of Norway spruce, Scots pine and silver birch in greenhouse experiments under constant observation of light and temperature factors. In the beginning of development air temperatures paid a greater effect on the onset of growth than light conditions. Cessation of growth was initiated by a signal of shortening night length. The age of seedlings or trees reflected in their behaviour: second year seedlings differed from first year seedlings and 56 years old mature trees differed from 15 years old young trees.

The papers by Häkkinen, Linkoaho and Partanen are academic dissertations.

Project leader: Luomajoki, Alpo

Other researchers: Häggman, Juhani, PU (1998-2002), Häkkinen, Risto, ES (1998-2002), Koski, Veikko (1998-2000), Savonen, Eira-Maija, PA (1998-2002)

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Updated 12.06.2012
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