Silvicultura

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. Manystudies 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. The evergreeen foresttype 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 the environmentalvariation 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 shade tolerance spectrum forthe 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 shade tolerant species in terms ofdensity 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 for a collection period of 7years. 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 breaking off dormancy. This lastcharacteristic 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 del tipo forestal, los cuales han dadoorigen 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 amplio rango latitudinal y altitudinal, que vaunido 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 lo largo de su amplísima distribución....