Environmental Conservation



Arrested succession in pastures hinders regeneration of Tropandean forests and shreds mountain landscapes


FAUSTO O.  SARMIENTO a1c1
a1 The Center for Latin American and Caribbean Studies and the Institute of Ecology, University of Georgia, Athens, Georgia 30602-1619, USA

Abstract

Arrested succession is conspicuous in the abandoned pastures of the Andean piedmont that have encroached upon the tropical montane forests toward higher limits and steeper slopes. Habitat 'shredding' is analysed to depict the current spatial configuration of tropical Andean landscapes, based on fragmentation patterns prompted by seed dispersal ecology and pasture encroachment.

Seed dispersal was studied to address the hypo-thesis that seed input constrains the recruitment of montane forest seedlings, thus impeding pasture conversion to forest. It turns out that a better competitor, the tussock grass Setaria sphacelata, is limiting dispersal success due to its bioarchitecture and planting patterns. Because of the variegation of fragments, the area is in danger of landscape homogeneity within a matrix of degraded pasture. Currently, protection of fragmented remnants and restoration of original landscape structure and function are urgent needs for land-use planning toward sustainable development in the region.

Restoration ecology is plausible as a means of conservation for degraded Tropandean forests, since human impacts have shredded landscapes entirely. Dispersal ecology may be used to facilitate pasture conversion to forest in equatorial landscapes, but the proactive approach of pasture removal or planting strategy should differ from that for lowland Amazonia, where abandoned pastures are different from those of montane environs. However, the region may be proactively managed only if political decisions include conservation as a goal of development.

(Received November 6 1996)
(Accepted February 12 1997)


Key Words: seed dispersal; habitat fragmentation; forest conversion; landscape restoration; tropical Andes; Ecuador.

Correspondence:
c1 Correspondence: Dr Fausto O. Sarmiento. Tel: 11 706 542 9079. Fax: 11 706 548 0089. E-mail: fsarmien@uga.cc.uga.edu