IFEVA   02662
INSTITUTO DE INVESTIGACIONES FISIOLOGICAS Y ECOLOGICAS VINCULADAS A LA AGRICULTURA
Unidad Ejecutora - UE
artículos
Título:
From pattern to process: estimating expansion rates of a forest tree species in a protected palm savanna
Autor/es:
ROLHAUSER, AG; BATISTA, W.B.
Revista:
LANDSCAPE ECOLOGY
Editorial:
SPRINGER
Referencias:
Lugar: Berlin; Año: 2014 vol. 29 p. 919 - 931
ISSN:
0921-2973
Resumen:
We assessed the possible influences of
dominant tree density (Butia yatay palm trees) and fire
on the expansion of a riparian tree population
(Myrcianthes cisplatensis) over El Palmar National
Park, a protected savanna in Argentina. Our approach
is based on Skellam?s model of population expansion,
which predicts that populations with density-independent
reproduction and random dispersal will exhibit
Gaussian-shaped expansion fronts. Using Poisson
regression, we fitted Gaussian curves to Myrcianthes
density data collected at varying distances from a
riparian forest, within four environmental conditions
resulting from combinations of palm density (dense
and sparse) and fire history (burned and unburned).
Based on the estimated parameters, we derived
statistics appropriate to compare attained expansion
velocity, mean squared effective dispersal distance,
and density-independent population growth among
environmental conditions. We also analyzed the
effects of palm density, fire history, and distance from
the riparian forest on local maximum size of Myrcianthes
individuals. Gaussian curves fitted the data
reasonably well and slightly better than two alternative
front models. Palm density and fire history interacted
to control Myrcianthes spread, making unburned
dense palm savannas the preferential avenue for
Myrcianthes population expansion across the landscape.
Limitation of Myrcianthes expansion by fire
appeared to result from low survival of small individuals
to fire, whereas facilitation of Myrcianthes
expansion by palm trees may have resulted from
increased population growth. Our results stress the
interactive role of fire regime and local biotic influences
in determining propagule pressure and tree
establishment at the forefront, and the overall vulnerability
of savannas to colonization by forest species.