• The cold climes on high-altitude mountain tops make it usually difficult for trees to grow above the timberline (the last canopy forests on the mountains).
  • Though global warming is changing this in many of the world’s high mountains and causing timberlines to move upward, the eastern Himalaya may be an exception, find scientists.
  • The zone of uppermost canopy forests here are unlikely to shift upwards but will get denser.
  • Timberlines, the uppermost limit of canopy forests that gradually gives way to the treeline (beyond which trees do not grow) are limited by climate: factors including low temperatures and high winds on mountain tops prevent woody tree growth higher up.
  • Timberlines, therefore, serve as indicators of climate change.
  • Across nine contiguous sites in the Park, the team studied tree composition in this ecotone which lay between 3,787 and 3,989 metres above sea level.
  • Among the 20 woody tree species they recorded here, the Bhutan fir Abies densa, the woolly rhododendron Rhododendron lanatum and the small-leaf rowan Sorbus microphylla dominated the vegetation.
  • Environmental factors such as elevation, slope and humus played a role in this species composition.
  • The density of trees in the timberline ecotone was significantly higher than that of its western Himalayan counterparts.
  • Bhutan fir seedlings regenerated well here and elevation (along with humus and slope) played a role in this regeneration too.
  • The zone contained high numbers of seedlings and saplings.
  • The ecotone could become denser in the near future.
  • However, there were no tree seedlings or saplings beyond the treeline.