Tree recruitment at theNothofagus pumilioalpine timberline in Tierra del Fuego, Chile

Abstract

Summary1 Nothofagus pumilio forms an abrupt alpine timberline (AT) at 690 m a.s.l on Balseiro mountain, 54 S, Tierra del Fuego, Chile. Fruit and seed rain (quantity and quality), emergence, density and survival of seedlings were studied across an altitudinal gradient (450±740 m) from within the forest to above the AT. 2 Fruit rain generally declined with altitude but increased between 630 and 690 m before falling sharply beyond the AT. The proportion of seed-bearing fruits, seed viability and seed mass also declined with increasing altitude, but showed no recovery in the vicinity of the AT. 3 Fruit rain decreased exponentially with distance into the alpine zone, so that e ective dispersal rarely exceeded 20 m beyond the AT and few of these fruits contained seeds. 4 Seedling emergence and density decreased with altitude both within the forest and into the alpine zone so that seedlings were found no more than 10±20 m above the AT. Even in 1996, when fruit production was high, successful seedling recruitment was limited to lower altitudes. 5 There was little correlation between altitude and the percentage survival of naturally occurring seedlings within the forest. However, transplanted seedlings survived better at the AT itself than immediately inside the forest, and showed high mortality in the alpine zone. 6 The most severe bottlenecks for tree recruitment within the forest appeared to be seedling emergence and seed production. Above the AT, seed viability and emergence were the principal bottlenecks. 7 Although not all demographic variables declined altitudinally, the overall probability of adult establishment decreased with increasing altitude and became very low once the protection by the tree canopy became unavailable. A demographic model explaining the origin and abrupt character of the AT studied is presented.

High solar radiation hinders tree regeneration above the alpine treeline in northern Ecuador

“…The importance of clonal growth for this species can be easily observed in the field, because of its strongly clustered distribution. This all indicates that dispersal is an additional limiting factor for forest extension, as has been suggested for some temperate treelines (Cuevas 2000;Wardle and Coleman 1992).…”

Human land-use, forest dynamics and tree growth at the treeline in the Western Italian Alps

“…This phenomenon has been observed in many mountain ranges in the northern [13,30,46,52,53,55] and southern hemisphere [10,62]. A smaller number of studies, however, have also shown that these limits are relatively stable [25].…”

Nurse effect and herbivory exclusion facilitate plant colonization in abandoned mine tailings storage facilities in north-central Chile

“…Density trends as a function of distance were adjusted to a negative exponential model given the shapes of the distribution frequencies. Moreover, the exponential curve is a common model for seed dispersal and seedling recruitment that has been used in many studies (e.g., Willson 1993, Bustamante 1995, Cuevas 2000. The regressions were computed through the Levenberg-Marquardt algorithm (Statistica 2.0 software).…”

“…Regarding seed dispersal, the concentration of fl oral and vegetative remnants near a mother plant is a typical result for abiotically dispersed species (Willson 1993, Bustamante 1995, Cuevas 2000. Moreover, species which have plumose achenes, such as those belonging to the Asteraceae family, are easily dispersed by the wind towards vegetation patches (Flores & Jurado 2003) where wind speed is lower (Ginocchio et al 2004).…”