Edge effects in a forest mosaic: implications for oak regeneration in the Highlands of Chiapas, Mexico.
dc.contributor.advisor
Newton, Adrian
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dc.contributor.advisor
Legg, Colin
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dc.contributor.advisor
Manson, Robert
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dc.contributor.advisor
González-Espinosa, Mario
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dc.contributor.author
López-Barrera, Fabiola
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dc.date.accessioned
2005-08-09T11:12:28Z
dc.date.available
2005-08-09T11:12:28Z
dc.date.issued
2004-07
dc.description.abstract
Forest edges created by scattered-patch clear-cutting have become a common
landscape feature in tropical montane forests, including pine-oak and evergreen
cloud forests. Forest-edge-pasture gradients were characterised with respect to
changes in vegetation structure and ecological function in the Highlands of Chiapas,
Mexico. In this study two edge types were recognised by assessing vegetation
structure and floristic composition along a gradient from adjacent clearings into the
forest interior. The influence of edge type (either “hard” or “soft”) was investigated
with respect to acorn production, predation, dispersal and germination, seedling
establishment and abundance of small mammals during two consecutive years.
There was no significant difference between the forest interior and the edge in plant
density and basal area. Floristic richness and composition did not vary with depth-of edge
influence. Edge type influenced the relationship between probability of acorn
removal by small mammals and distance from the edge in both mast fruiting and
non-mast fruiting years. Movements of metal-tagged acorns supported the hypothesis
that soft edges are permeable to acorn predators and/or dispersers, and that rodents
move acorns up to 15 m into the grasslands in soft edges. In hard edges, acorn
dispersal and removal was greater within the forest. Peromyscus spp. were the main
acorn predators and/or dispersers of acorns. The intensity and rate of acorn removal
varied with the year, demonstrating that in mast-fruiting years some seeds may
escape predation by animals, according to the predator satiation hypothesis.
Grasslands presented fewer insect damaged acorns and higher seedling emergence
than the edge and the forest, emphasising the importance of acorn dispersal. Seedling
survival and growth were higher for 12 m into grassland from the soft edges,
suggesting that the probability of oak expansion into the grassland increases when
the grasslands have been abandoned and have a scattered cover of shrubs.
The results indicate that edge structure alters edge function (edge permeability),
which determines the probabilities of tree invasion into old-fields. These findings
have implications for the conservation of montane forest in Mexico where scattered
patch clear-cutting is widespread. Recommendations are made for different
restoration practices to accelerate tree colonisation into the grasslands across hard
and soft edges.
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5023855 bytes
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dc.format.mimetype
application/pdf
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dc.identifier.uri
http://hdl.handle.net/1842/806
dc.language.iso
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dc.publisher
University of Edinburgh; College of Science and Engineering; School of GeoScience
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dc.subject
Forest
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dc.subject
tropical montane
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dc.subject
Chiapas
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dc.subject
Mexico
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dc.subject
Global Change Research Institute
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dc.subject.other
Forest
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dc.subject.other
tropical montane
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dc.subject.other
Chiapas
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dc.subject.other
Mexico
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dc.title
Edge effects in a forest mosaic: implications for oak regeneration in the Highlands of Chiapas, Mexico.
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dc.type
Thesis or Dissertation
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dc.type.qualificationlevel
Doctoral
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dc.type.qualificationname
PhD Doctor of Philosophy
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