Protection plantations with indigenous species have increased considerably in the last few years in Brazil, mainly in degraded areas of the most densely populated states. Such reforestations for nonindustrial purposes assume the association of many species in the plantations, imitating the high diversity of species existing in natural tropical forests.
Results of experimentation on mixed protection plantations are presented, using the secondary succession to separate species into ecological groups. It is considered that mixed reforestation should be similar to natural forests, which consist of a mosaic of successional stages.
Following the patterns that characterize the natural occurrence of tree species in tropical forests, it is proposed to create mixed protection reforestation models, where the requirement of amount of seed per species and per hectare is minor, and differentiated by ecological group species.
Seed production of indigenous tree species for the purpose of revegetating degraded areas must comply with the high diversity of species of tropical forests, as well as the form in which the individuals of the species occur in the forest. The separation of species into ecological groups seems to be an adequate manner of solving the problem, since the different groups present very distinct characteristics with regard to seed production.
Les plantations de protection avec des espèces indigenes ont été considérablement développées ces derriere années au Brésil surtout dans les regions détêriorées des Etats qui ont plus grandes densités de population. Ces reboissements qui n'ont pas d'interêt industrial, utilisent ['union des plusieurs specimens dans les plantations en imitant la grande diversité d'espèces existent dans les forêts naturelles tropicales.
On considère que la plantation mixte est similaire a la fores naturelle, qui est composée d'un mosaique de stades successifs. On présente ici des résultats d'expérimentation avec des plantations mixtes de protection qui utilisent la succession secondaire pour séparer les spécimens en groupes écologiques.
En suivant les modèles qui caractérisent l'occurence naturelle des spécimens d'arbres dans les forêts tropicales, on propose de devélopper des modèles de rehabilitation forestière mixte de protection où la nécessité de quantité de semences par espèce et par hectare est minimisée et différenciée par groupe écologique.
La production de semences de specimens d'arbres natifs dans le but de réhabiliter des zones détériorées a besoin de s'adapter a la grande diversité d'espèces de la fores tropicale et d'être organisée de la même manière pour que les arbres de chaque espèce qui se developpent dans la fores.
La séparation de specimens par groupes écologiques semble être une bonne manière de résoudre le problème, puisque les différents groupes présentent des caractéristiques très diverges par rapport a la production des sémences.
Las plantaciones de protección con espécies natives hen sido incrementadas considerablemente en los ultimos anos en el Brasil, principalmente en areas degradadas en los estados con mayor densidad populacional. Estas reforestaciones non-industriales están utilizando la associación de muchas espécies en las plantaciones, imitando la alta diversidad existente en las selves tropicales.
Se presentan resultados de la experimentación con plantaciones mixtas de protección, usando la successión secundaria pare separar hs espécies en grupos ecológicos. Se está considerando que h reforestación mixta seria similar a la selva natural, que está compuesta de un mosaico de estadios de sucesión.
Seguiendo los padrones que caracterizan la ocurrencia natural de las espécies arbóreas en las selvas tropicales, x propone desarrollar modelos de reforestación mixto de protección, donde la necesidad de cantidad de semillas por especie y por hectárea sea minimizada y diferenciada por grupo ecológico de espécies.
La producción de semillas de espécies natives pare fines de revegatación de areas degradadas precise adequarse a la alta diversidad de espécies de la selva tropical, así como la forma en que los individuos de las espécies ocurren en la selva. La separación de las espécies en grupos ecológicos parece ser una forma adequada de resolver el problema, ya que los diferentes grupos presentan caracteristicas muy distintas en relación a la produción de semillas.
The advance of present environmental legislation in Brazil, together with environmentalist actions and society pressure has demonstrated the need for protection plantations of indigenous species, with the aim of minimizing the advanced degree of disturbance involving large areas of permanent protection, mainly in the most densely populated regions of the country.
Towards this end, several universities, research institutions and even private enterprises are developing research projects with indigenous species, especially in the last 10 years, with the aim of revegetating degraded areas, notably those of permanent protection (riparian forests, slopes, reserves etc.). The Non-Governmental Organizations (NGOs) have also played an important role towards this objective.
Silviculture has evolved in Brazil as an activity directed, to a large extent, to the production of raw material for wood and fibre industries, especially exotic species of the genera Eucalyptus and Pinus. The concept of multiple use of planted forests has only recently emerged as a basic objective with recreational, soil protection, water resource and genetic conservation purposes. Such plantations for non-industrial purposes assume the association of many species in an attempt to imitate the high diversity of species existing in the tropical forests.
According to KAGEYAMA, CASTRO and CARPANEZZI (1989), the actions intended to establish protection forests, for example in degraded riparian forests, are undertaken for the following purposes:
a) recreate the vegetation existing in the past, maintaining the structure as well as the composition of original species; and
b) recompose a vegetation structure with a view to obtain benefits such as the containment of bank erosion, re-establishment of a hydric and nutrient regime, and the retention of fertilizers and agrotoxics.
The much demanded planting of indigenous species comes up against a number of operational difficulties for commercial scale production of seed, as well as in promoting the growth and development of many associated species together. To overcome such problems, we believe that much can be inferred from knowledge relating to the reproductive biology, secondary succession and genetic structure of tropical tree species.
Information on the major part of the species is still scanty due, mainly, to the large quantity of species existing in the tropics, as well as the complexity of the interactions involving such species, especially with animals.
The objective of this paper was to review the state of art in Brazil, with regard to the revegetation in degraded areas as well as the production and procurement of seed of indigenous species, discussing the main problems existing and pointing out solutions and research directions for them.