Natural regeneration of Scots pine and Norway spruce close to the timberline in northern Finland

Abstract

Two different datasets were analyzed in order to clarify the factors that affect regeneration success of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) in the climatically extreme areas in northern Finland. First, pine seed maturity and the number of cones in the trees were investigated at five pairs of study sites during the period 1997-2003. Secondly, the rate of seedling establishment and seedling survival of Scots pine and Norway spruce were monitored and compared among three different timberline zones (forest zone, timberline, tree line) in 13 localities during the period 1983-1999. The first study showed that both cone production (bud formation) and seed maturity may be limiting factors for successful reproduction in the climatically marginal habitats. Seed maturity correlated well with the temperature sum of the summer, but variation in the number of cones had a periodic component rather than strictly following the temperature sum of the summer of bud formation. Monitoring surveys since 1983 showed that pine and spruce regenerated more or less regularly in all the zones during 1983-1999. However, seedling mortality of pines was much higher compared to spruce. In general, initially small sized seedlings showed higher mortality compared with larger ones. The results suggest that besides restrictions in reproduction, stand dynamics in the timberline habitats are strongly controlled by seedling mortality due to a variety of causes.

Coping with spring frost-effects on polyamine metabolism of Scots pine seedlings

“…Late winter and spring weather conditions have great significance on the population dynamics of Scots pine at the northern timberline (Juntunen & Neuvonen 2006). Humidity and temperature affect the timing of Scots pine seed germination.…”

The contradictory role of understory vegetation on the success of Scots pine regeneration

“…Poor natural regeneration of Scots pine in harsh climate conditions is known to be associated with northern latitude, high elevation, and low temperature sum causing small seed crops, a low seedling establishment rate, slow height growth and high seedling mortality (Varmola et al 2004;Hyppönen et al 2005;Juntunen and Neuvonen 2006). In North-East Finland, the regeneration of Scots pine has been even more difficult than elsewhere in the timberline regions (Niemelä 2002;Hallikainen et al 2007).…”

Treelines—Approaches at Different Scales

“…Thus, the distance from the seed source, the way of seed dispersal (anemochoric, zoochoric), the overlying of seeds, the availability of viable seeds, seed predation, and the availability of favorable seed beds (e.g., [5,85,87,88,[90][91][92][93]) are relevant factors that need further examination. However, discussion of whether reduced availability of viable seeds are playing a major role or not is controversial (e.g., [3,5,17,19,45,87,90,[93][94][95][96][97]). In any case, the performance of "new" trees that survived the seedling stage and became a sapling appears to be the most important factor for treeline advance in the medium and long term.…”