INVESTIGADORES
ASCHERO Valeria
artículos
Título:
The fencing paradigm in woodland conservation: consequences for recruitment of a semi-arid tree. Applied Vegetation Science 15: 307-317
Autor/es:
ASCHERO, V. & GARCÍA, D.
Revista:
APPLIED VEGETATION SCIENCE
Editorial:
WILEY-BLACKWELL PUBLISHING, INC
Referencias:
Lugar: Londres; Año: 2012 vol. 15 p. 307 - 317
ISSN:
1402-2001
Resumen:
Question:
How
does long-term fencing against large domestic herbivores affect
regeneration
of the dominant tree, Prosopis
flexuosa,
and hence the structure of
semi-arid
woodlands?
Location:
Woodlands
in the Central Monte Desert biome of Argentina, N? acun
?
a´n Man and the Biosphere Reserve area (34°
20′
S,
67°
58′
W)
and surrounding
cattle-grazed
ranches.
Methods:
We
compared seedling emergence and survival, the spatial distribution
of
seedlings and saplings, and the population stage-based structure of
P.
flexuosa between
paired sites inside and outside the Reserve of N? acun? a´n
(Argentina),
which has been fenced to exclude domestic cattle for ca. 40 yr.
Results:
Reserve
sites had lower tree recruitment and seedling emergence, in
spite
of having greater seed production and seedling survival. Outside the
reserve,
survival was higher for seedlings in high-density clumps than for
isolated
seedlings.
Seedling clumps occurred mostly near adult individuals, where
cattle
dung was abundant, suggesting an effect of cattle on seed dispersal.
The
balance
between the effects of cattle exclusion on seedling emergence and on
seedling
survival was reflected in the stage structure of P.
flexuosa woodlands,
as
populations
at fenced sites were dominated by adult individuals, whereas those
at
cattle-grazed areas presented greater proportions of seedlings and
saplings.
Conclusion:
Fencing
is a common practice used worldwide to exclude conservation
areas
from human disturbance. For example, it is assumed that disturbed
woodlands
may recover after fencing, thanks to increased tree recruitment after
the
exclusion of large herbivores. However, the actual effectiveness of
fencing as
a
tool for forest conservation in overgrazed environments could be
controversial
because
sequential effects of herbivores during the tree regeneration cycle
may
hamper
predictions of the overall balance of the recruitment process. Our
results
suggest
that dispersal by cattle influences the regeneration of P.
flexuosa woodlands,
and
that the positive effects of cattle on seedling emergence compensate
for
the negative effects on seed production and seedling and sapling
survival.
Futuremanagement
of P.
flexuosa woodlands
in the CentralMonte Desert should
consider
that tree recruitment is closely related to land use, and that cattle
exclusion
does
not necessarily guarantee woodland recovery in the long term.