Plant Ecology

, Volume 194, Issue 2, pp 207–221

Effects of altitude and livestock on the regeneration of two tree line forming Polylepis species in Ecuador

  • Arne Cierjacks
  • Nadine Katrin Rühr
  • Karsten Wesche
  • Isabell Hensen
Article

DOI: 10.1007/s11258-007-9285-x

Cite this article as:
Cierjacks, A., Rühr, N.K., Wesche, K. et al. Plant Ecol (2008) 194: 207. doi:10.1007/s11258-007-9285-x

Abstract

Regeneration is known to be limited at many temperate tree lines, but very little data is available on the impacts of altitude and anthropogenic disturbance on regeneration patterns along tropical tree lines. The study focused on the reproductive traits of two Polylepis species in the Páramo de Papallacta in Ecuador along an altitudinal gradient, and involved different intensities of cattle trampling within subsequent altitudinal ranges. We analyzed flowering, fruit set, seed viability, germination, and seedling establishment as well as stand structure of Polylepis incana and P. pauta. The numbers of P. incana inflorescences and seedlings per m² showed a marginally significant decrease with increasing altitude. Mean tree height was significantly lower at higher altitudes, while stem number increased. The number of P. pauta inflorescences also decreased significantly upslope. In both forest types, trampling was found to have a positive impact on seedling abundance, presumably due to the removal of the litter layer. Thus, there was no evidence of negative effects of moderate cattle grazing on both tree line species. However, sapling establishment was minimal inside the forest stands at all altitudes and grazing levels, and we consequently observed a low proportion of narrow stems within all investigated forests. Our results show that, along with vegetative growth limitations of adult trees, important regeneration traits such as seedling and inflorescence numbers are also influenced by altitude, which might contribute to the formation of the upper tree line. Nevertheless, recruitment in the forest interior was low overall indicating that further factors, such as light conditions, affect regeneration of the studied species.

Keywords

Anthropogenic impact Herbivory Polylepis Reproduction Trampling Tree line 

Copyright information

© Springer Science+Business Media, Inc. 2007

Authors and Affiliations

  • Arne Cierjacks
    • 1
  • Nadine Katrin Rühr
    • 1
  • Karsten Wesche
    • 1
  • Isabell Hensen
    • 1
  1. 1.Institute of Biology/Geobotany and Botanical GardenMartin-Luther-University Halle-WittenbergHalleGermany

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