silvicultura comunitaria en mexico

BOSQUE: 10(1): 37-5 3,1989

Antecedentes básicos para la silvicultura
del tipo forestal siempreverde
Silvics of the evergreen forest type
C.D.O.: 568
CLAUDIO DONOSO ZEGERS

Instituto de Silvicultura, Universidad Austral de Chile,

Casilla 567, Valdivia, Chile.


SUMMARY
Because of economic and accesibility reasons the evergreen forest type (siempreverde) has been barely
studied.Many studies related to species or stands or subtypes of the forest type have been performed
during the last years; these studies have produced numerous reports and also some theses and journal
papers. From those works the data that constitute this paper has been synthesized as the foundation
fo the silvics of the largest forest type of Chile, with 4.8 millions estimated hectares. Theevergreeen
forest type occurs over a broad latitudinal and altitudinal range, which goes together with an important
variation of the environmental condition, including climate, topography and substrate. This great varia­
tion necessarily implies a similar floristic diversity, taking into account only forest trees, there are more
than 21 forest species, which are mixed in various ways according to theenvironmental variation along
their broad distribution. This characterization indicates that the evergreen forest type is a system of
very different forest communities, and that any prescription related to its silviculture or management
must refer to specific stands or conditions. Regeneration and forest dynamics studies, together with
specific autoecologic studies, reflected a broad shadetolerance spectrum for the different species.
Depending on the shade tolerances and regenerative strategies defined for the different species, the first
and intermediate successional stages will take specific courses, according to the type of exploitation or
natural alteration produced. Stand structure of the steady-state communities is characteristicaly uneven
aged, and dominated by shadetolerant species in terms of density and frequency, and by shade in­
tolerant emergent species in terms of basal area and tree height. Floristic composition of climax forests
will vary as a function of environmental variation. In addition, the species present different cycles or
periodicity of the annual seed production, which are very regular for some species, or irregular for others,
at least fora collection period of 7 years. Seed size, weights and morphology are very variable, depend­
ing on the dissemination agent which is also related to shade tolerance and regenerative strategies of the
species. Finally, germination capacity of the species vary from very low to very high percentages of
germination, and most of the species require different cold and wet stratification for breakingoff
dormancy. This last characteristic is commonly related to the regenerative strategy of the species.

RESUMEN
El tipo forestal siempreverde ha sido escasamente estudiado desde el punto de vista ecológico y silvicultu­
ral, debido a razones económicas y de accesibilidad. En los últimos años se han llevado a cabo diversos
proyectos relacionados con las especies o con rodales o subtipos deltipo forestal, los cuales han dado
origen a numerosos informes de convenio, así como a algunas tesis y publicaciones. De estos trabajos
se han obtenido los antecedentes que constituyen esta publicación y que significan el primer paso hacia
la silvicultura básica del tipo forestal, el más extenso de Chile, con 4,8 millones de hectáreas estimadas.
El tipo forestal se desarrolla en un ampliorango latitudinal y altitudinal, que va unido a una consisten­
te variación en las condiciones medioambientales tanto de clima, como de topografía y de sustrato.
Esta enorme variación se traduce necesariamente en una gran diversidad representada, sólo en cuanto
a árboles, por más de 21 especies que se mezclan en distintas combinaciones y proporciones en función
de la variación medioambiental a...