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Silva Fennica 1926-1997
Acta Forestalia Fennica

Articles containing the keyword 'photoperiod'

Category : Article

article id 5583, category Article
Ilkka Leinonen, Heikki Hänninen, Tapani Repo. (1996). Testing of frost hardiness models for Pinus sylvestris in natural conditions and in elevated temperature. Silva Fennica vol. 30 no. 2–3 article id 5583.
Keywords: Pinus sylvestris; climate change; frost hardiness; Scots pine; temperature; dynamic models; photoperiod; climatic warming
Abstract | View details | Full text in PDF | Author Info

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, E-mail: il@mm.unknown (email)
  • Hänninen, E-mail: hh@mm.unknown
  • Repo, E-mail: tr@mm.unknown
article id 5534, category Article
Hyun Kang, Inger Ekberg, Gösta Eriksson, Johan Ununger. (1994). Second and third growth period responses of Picea abies families to first growth period photoperiodic, light intensity and temperature treatments. Silva Fennica vol. 28 no. 4 article id 5534.
Keywords: Picea abies; growth; maturation; temperature; seedlings; photoperiod; environmental effects; genetic effects; juvenility
Abstract | View details | Full text in PDF | Author Info

Seedlings of Picea abies (L.) H. Karst. full-sib families of contrasting origins were cultivated in a phytotron under different photoperiodic, light-intensity and temperature treatments during their first growth period. The effects of the treatments on juvenile growth traits – whether enhanced or delayed maturation was induces – were observed during the two subsequent growth periods. The following hypotheses were tested: (A) Enhanced maturation can be induced in the first growth period from sowing with (i) a long period of continuous light during active growth (24 weeks vs. 8 weeks); (ii) a shorter night during bud maturation (12 h vs. 16 h); high temperature (25°C vs. 20°C) during (iii) active growth, growth cessation and bud maturation; and during (iv) the latter part of growth cessation and bud maturation only. (B) Delayed maturation can be induced after (i) low light intensity during growth cessation and bud maturation (114 μmol m-2 s-1 vs. 340 μmol m-2 s-1); low temperature (15°C vs. 20°C) during (ii) active growth, growth cessation and bud maturation; and during (iii) the latter part of growth cessation and bud maturation only.

The most dramatic effect was observed after 24 weeks of continuous light during active growth. All traits showed a significantly more mature performance in the second growth period compared with the control. The effect for all but one trait was carried over to the third growth period. This is in accordance with the hypothesis that the activity of apical shoot meristems controls the maturation process. For the other treatments there was only weak or no support for the hypothesis of induction of enhanced or delayed maturation. Strong family effects were observed for all traits. Differential responses of the various latitudinal families were observed, suggesting that family effects must be considered to predict and interpret correctly how plants will respond to environmental effects.

  • Kang, E-mail: hk@mm.unknown (email)
  • Ekberg, E-mail: ie@mm.unknown
  • Eriksson, E-mail: ge@mm.unknown
  • Ununger, E-mail: ju@mm.unknown
article id 5257, category Article
Heikki Hänninen. (1986). Metsäpuiden vuosirytmitutkimuksen käsitteistä ja teorioista. Silva Fennica vol. 20 no. 1 article id 5257.
English title: Conceptual remarks about the study of the annual rhythm of forest trees.
Original keywords: lämpösumma; ekofysiologia; fenologia; vuosirytmi; dormanssi; aklimaatio
English keywords: acclimation; temperature sum; climatic adaptation; dormancy; phenology; photoperiod; annual cycle of development
Abstract | View details | Full text in PDF | Author Info

Different approaches to the study of the annual rhythm of forest trees are described and compared by analysing the concepts and theories presented in the literature. The seasonality varying morphological and physiological state of forest trees is referred to as the annual rhythm s. lat., from which the annual ontogenetic rhythm is separated as a distinct type. The dormancy phenomena of the trees are grouped into four categories. Theories concerning the regulation of the annual rhythm are divided into two main types, the most common examples of which are the photoperiod theory and the temperature sum theory. Recent efforts towards a synthetic theory are described.

The PDF includes a summary in English.

  • Hänninen, E-mail: hh@mm.unknown (email)
article id 4771, category Article
J. G. Gordon, G. E. Gatherum. (1968). Photosynthesis and growth of selected Scots pine populations. Silva Fennica vol. 2 no. 3 article id 4771.
Keywords: Pinus sylvestris; photosynthesis; Scots pine; height growth; provenance; growth; photoperiod
Abstract | View details | Full text in PDF | Author Info

Eight Scots pine (Pinus sylvestris L.) seed sources, ranging from 42° to 66° north latitude, were grown under a constant, 16-hour photoperiod in a greenhouse for approximately 6 months. Rates of photosynthesis, as measured by an IRGA, and growth, as measured by increase in height and fresh and dry weight, differed among seed sources at the end of the six-month growing period. Photosynthetic capacity and growth were strongly related to latitude of seed source, and were greatest in the seed sources coming from a parent environment in which maximum photoperiods are about 16 hours.

Photosynthetic efficiency (rate of photosynthesis per gram needle weight) was also strongly related to latitude of seed source, but was lowest in the seedlings which exhibited the greatest growth and photosynthetic capacity. This may have been due to (1) more mutual shading of needles on the larger seedlings and (2) a lesser proportion of juvenile needles on the larger seedlings or (3) biochemical differences in the use of photosynthate in the needles. Seed source and light intensity had an interacting effect on rates of photosynthesis only in seedlings of the two northernmost seed sources.

The PDF includes a summary in Finnish.

  • Gordon, E-mail: jg@mm.unknown (email)
  • Gatherum, E-mail: gg@mm.unknown

Category : Article

article id 7523, category Article
Alpo Luomajoki. (1999). Differences in the climatic adaptation of silver birch (Betula pendula) and downy birch (B. pubescens) in Finland based on male flowering phenology. Acta Forestalia Fennica no. 263 article id 7523.
Keywords: Betula pendula; Betula pubescens; adaptation; seasonality; hybridization; male flowering; heat sum; timing of flowering; pollen catch; photoperiods; ecophysiological differences
Abstract | View details | Full text in PDF | Author Info

Male flowering was studied at the canopy level in 10 silver birch (Betula pendula Roth) stands from 8 localities and 14 downy birch (B. pubescens Ehrh.) stands from 10 localities in Finland in 1963–73. Distribution of cumulative pollen catches was compared to the normal Gaussian distribution. The basis for timing of flowering was the 50% point of the anthesis-fitted normal distribution. To eliminate effects of background pollen, only the central, normally distributed part of the cumulative distribution was used. Development was measured and tested in calendar days, in degree days (> 5°C) and in period units. The count of the parameters began in March 19.

Male flowering in silver birch occurred from late April to late June depending on latitude, and flowering in downy birch took place from early May to early July. The heat sums needed for male flowering varied in downy birch stands latitudinally but there was practically no latitudinal variation in silver birch flowering. The amount of male flowering in stands of the both species were found to have a large annual variation but without any clear periodicity.

The between years pollen catch variation in stands of either birch species did not show any significant latitudinal correlation in contrast to Norway spruce stands. The period unit heat sum gave the most accurate forecast of the timing of flowering for 60% of the silver birch stands and for 78.6% of the downy birch stands. Silver birch seems to have a local inclination for a more fixed flowering date compared to downy birch, which could mean a considerable photoperiodic influence on flowering time of silver birch. The species had different geographical correlations.

Frequent hybridization of the birch species occurs more often in Northern Finland than in more southerly latitudes. The different timing in the flowering causes increasing scatter in flowering times in the north, especially in the case of downy birch. Thus, the change of simultaneous flowering of the species increases northwards due to a more variable climate and higher altitudinal variation. Compared with conifers, the reproduction cycles of the two birch species were found to be well protected from damage by frost.

  • Luomajoki, E-mail: al@mm.unknown (email)
article id 7642, category Article
Alpo Luomajoki. (1986). Timing of microsporogenesis in trees with reference to climatic adaptation: a review. Acta Forestalia Fennica no. 196 article id 7642.
Keywords: photoperiod; annual cycle; heat sum; microsporogenesis; meiosis; tetrad
Abstract | View details | Full text in PDF | Author Info

The timing of the tetrad phase of microsporogenesis in sixteen tree species, belonging to the genera of Abies, Larix, Picea, Pinus, Alnus, Betula, Corylus and Populus, was studied. The tetrad phase of microsporogenesis in conifers and in Populus tremula L. was reached from late March to early June including the yearly and latitudinal variation. The tetrad phase in Betulaceae was reached in late July to mid-August. The microsporogenesis in Betulaceae species differed in ecophysiological terms from the other species studied in that the timing in Betulaceae was rather day-length dependent than heat sum-correlated. In conifers and in Populus the timing of tetrad phase correlated with heat sums accumulated and did not correlate with day length or any kind of thermal threshold. This difference was, however, judged to be associated to seasonal adaptive strategies rather than taxonomic relationships.

The PDF includes a summary in Finnish.

  • Luomajoki, E-mail: al@mm.unknown (email)

Category : Research article

article id 1009, category Research article
Inger Sundheim Fløistad, Aksel Granhus. (2013). Timing and duration of short-day treatment influence morphology and second bud flush in Picea abies seedlings. Silva Fennica vol. 47 no. 3 article id 1009.
Keywords: Norway spruce; photoperiod; autumn bud break; root collar diameter; second bud break; sturdyness
Highlights: The duration of short-day treatment, calculated as number of days, influenced the root collar diameter growth more than the timing of the treatment; If short-day treatment starts early in summer, a longer duration of the treatment is recommended to avoid second bud flush.
Abstract | Full text in HTML | Full text in PDF | Author Info
A slower reaction of diameter growth cessation compared to that of height growth in response to short day (SD) treatment is well documented in Picea abies (L.) Karst. seedlings, suggesting that the height/diameter ratio of seedlings could be controlled through appropriate timing and/or duration of SD treatment is forest nurseries. Here, we applied specific combinations of timing (starting date 20 and 27 June, 4 or 11 July) and duration (7, 10, 14 or 17 days) of SD treatment to assess the possibility of obtaining more sturdy seedlings. We observed a rapid and uniform height growth cessation following SD treatment compared with the delayed cessation of diameter growth. Height growth responded significantly only to starting date of SD treatment, resulting in taller seedlings for later starting dates. Diameter growth responded to the duration of SD treatment, with significantly less diameter growth in seedlings exposed to 14 or 17 days of SD treatment than in seedlings exposed to 7 or 10 days of SD treatment. Also starting date influenced diameter growth, resulting in significantly more diameter growth with the earliest starting date compared with the two latest starting dates of the SD treatment.  A second bud flush occurred only in seedlings exposed to SD treatment starting on 20 or 27 of June and only following 7-14 days of duration. This implies a need of longer duration if the SD treatment starts early. This will be at the expense of sustained diameter growth, thus compromising the objective of obtaining more sturdy seedlings.
  • Fløistad, Norwegian Institute for Agricultural and Environmental Research, Høgskolevn 7, N-1430 Ås, Norway & Norwegian Forest and Landscape Institute, P.O. Box 115, N-1431 Ås, Norway E-mail: (email)
  • Granhus, Norwegian Forest and Landscape Institute, P.O. Box 115, N-1431 Ås, Norway E-mail:
article id 691, category Research article
Jacek Oleksyn, Mark G. Tjoelker, Peter B. Reich. (1998). Adaptation to changing environment in Scots pine populations across a latitudinal gradient. Silva Fennica vol. 32 no. 2 article id 691.
Keywords: Pinus sylvestris; climate change; provenance; growth; temperature; photoperiod
Abstract | View details | Full text in PDF | Author Info
In several growth chamber and field experiments we examined the growth response of Scots pine (Pinus sylvestris L.) populations from a wide latitudinal range to temperature and photoperiod. The duration of the shoot elongation period of one-year-old seedlings was affected by temperature and photoperiod. In contrasting temperatures, 23/20 °C, 20/17 °C, and 17/14 °C (day/night), shoot elongation period for all populations was shortest in the high and longest in the low temperature treatments. The northern populations from 61–57°N ceased height growth earlier than the other populations in the southern 50°N photoperiod. The order of growth cessation among populations at 50°N in the chamber experiment and at 52°N in the field experiment was similar and related to observed population differences in terminal leader growth and total tree height. Since the length of growing season is under strong environmentally-mediated genetic control in Scots pine, potential climatic changes such as increasing temperature will probably alter the length and timing of growth in aboveground tree parts, but likely in the opposite direction (a shorter growing season) than has been often hypothesized (a longer growing season). Tree-ring analyses of a provenance experiment established in 1912 indicate that the main climatic factors that limited ring-width growth in Scots pine were air temperatures in the winter months of December through March. Low winter temperatures were followed by the formation of narrow rings over the next summer. Based on responses to temperature, Scots pine populations from the continuous European range can be divided in several geographic groups along a latitudinal gradient. Our results suggest that in developing new models to predict the response of Scots pine to changing environmental conditions, it is necessary to include intraspecific differentiation in acclimation and adaptation to environmental factors.
  • Oleksyn, Polish Academy of Sciences, Institute of Dendrology, Parkowa 5, PL-62-035 Kórnik, Poland; University of Minnesota, Department of Forest Resources, 1530 Cleveland Ave. N., St. Paul, MN 55108, USA E-mail: (email)
  • Tjoelker, University of Minnesota, Department of Forest Resources, 1530 Cleveland Ave. N., St. Paul, MN 55108, USA E-mail:
  • Reich, University of Minnesota, Department of Forest Resources, 1530 Cleveland Ave. N., St. Paul, MN 55108, USA E-mail:

Category : Review article

article id 10381, category Review article
Carl F. Salk. (2020). Interpreting common garden studies to understand cueing mechanisms of spring leafing phenology in temperate and boreal tree species. Silva Fennica vol. 54 no. 5 article id 10381.
Keywords: photoperiod; bud break; budburst; chilling; elevation gradients; latitudinal gradients; leaf flush; reciprocal transplant experiments; xylem anatomy
Abstract | Full text in HTML | Full text in PDF | Author Info

Trees are particularly susceptible to climate change due to their long lives and slow dispersal. However, trees can adjust the timing of their growing season in response to weather conditions without evolutionary change or long-distance migration. This makes understanding phenological cueing mechanisms a critical task to forecast climate change impacts on forests. Because of slow data accumulation, unconventional and repurposed information is valuable in the study of phenology. Here, I develop and use a framework to interpret what phenological patterns among provenances of a species in a common garden reveal about their leafing cues, and potential climate change responses. Species whose high elevation/latitude provenances leaf first likely have little chilling requirement, or for latitude gradients only, a critical photoperiod cue met relatively early in the season. Species with low latitude/elevation origins leafing first have stronger controls against premature leafing; I argue that these species are likely less phenologically flexible in responding to climate change. Among published studies, the low to high order is predominant among frost-sensitive ring-porous species. Narrow-xylemed species show nearly all possible patterns, sometimes with strong contrasts even within genera for both conifers and angiosperms. Some also show complex patterns, indicating multiple mechanisms at work, and a few are largely undifferentiated across broad latitude gradients, suggesting phenotypic plasticity to a warmer climate. These results provide valuable evidence on which temperate and boreal tree species are most likely to adjust in place to climate change, and provide a framework for interpreting historic or newly-planted common garden studies of phenology.

  • Salk, Southern Swedish Forest Research Centre, Swedish University of Agricultural Sciences, P.O. Box 49, SE- 230 53 Alnarp, Sweden; Faculty of International Studies, Utsunomiya University, 350 Minemachi, Utsunomiya-shi, Tochigi 321-8505 Japan; Institute for Globally Distributed Open Research and Education (IGDORE) E-mail: (email)

Category : Research note

article id 608, category Research note
Jouni Partanen, Ilkka Leinonen, Tapani Repo. (2001). Effect of accumulated duration of the light period on bud burst in Norway spruce (Picea abies) of varying ages. Silva Fennica vol. 35 no. 1 article id 608.
Keywords: Norway spruce; phenology; growth initiation; photoperiod
Abstract | View details | Full text in PDF | Author Info
One-year-old seedlings (two sowing times), two-year-old seedlings and 14- and 18-year-old cuttings of Norway spruce (Picea abies (L.) Karst.) were exposed to shortening photoperiod (initially 16 h), lengthening photoperiod (initially 6 h) and constant short photoperiod (6 h) treatments with uniform temperature conditions in growth chambers. The timing of bud burst was examined. In all plants, shortening photoperiod treatment seemed to promote bud burst compared with other treatments. This effect was clearest in the oldest material. The results suggest that, in addition to temperature sum, the accumulated duration of the light period may promote bud burst of Norway spruce.
  • Partanen, Finnish Forest Research Institute, Punkaharju Research Station, Finlandiantie 18, FIN-58450 Punkaharju, Finland E-mail: (email)
  • Leinonen, University of Joensuu, Faculty of Forestry, P.O. Box 111, FIN-80101 Joensuu, Finland E-mail:
  • Repo, University of Joensuu, Faculty of Forestry, P.O. Box 111, FIN-80101 Joensuu, Finland E-mail:

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