Nguyen Son Tung
INTRODUCTION
Vule forest is found in a mountainous area with medium elevation and annual rainfall of 2000 mm. This forest is part of the tropical, monsoon, evergreen type with typical tree species such as Bassia sp., Vatica sp., Dipterocarpus sp., Pasania sp., Castanopsis sp. Cinnamomum sp., Amora sp., Dyxoxylon sp., Michelia sp. and Markhamia sp. Due to overexploitation, forests at Vule are mostly in a poor condition.
RESEARCH AIMS AND METHOD
This research investigates regeneration methods to change poor forest into forest with high levels of wood production. Artificial regeneration was used in combination with natural regeneration to create a mixed forest, which showed more natural characteristics. Forests selected were IIIa1 and IIIa2 forest types as classified in production. Preliminary experiments were done with Machilus bonii and Pasania ducampii. These are large tree species found in many areas and their wood has many uses. They have different growth habits, especially at the juvenile stage.
The research was based on characteristics of rehabilitation success where tree species showing different patterns of behaviour can live normally in a mixture with rehabilitated grass and other tree species. The research was orientated at finding ways to regenerate tree species living in a mixture with other, rehabilitated tree species.
Experiments were carried out as follows:
– Cut all old forest trees and leave only naturally regenerated trees.
– Keep seedlings in a nursery up to heights of 0.7-1.2 m for both tree species then plant them after cutting all old forest trees. Planting density is 200 trees/ha for Pasania ducampii and 400 trees/ha for Machilus bonii with the aim that half of those trees will
develop into large trees with available, naturally regenerated trees, so that one forest with final density of 300-330 trees/ha can be formed.
– Husbandry includes turning up earth around trees, cutting regenerated grass and trees to a certain level so that timber species can grow well in the layer of regenerated grass and trees.
RESULTS
1. By using this regeneration method in the field, 10 ha of young forests aged 1 to 6 years have been established. After 3 years, the forest canopy contains planted trees and naturally regenerated trees which form a 4-5m high tree layer. Beside planted trees, there were other naturally regenerated tree species such as Canarium sp., Prunus arborea, Peltophorum pterocarpum, Endospermum sinensis, Pasania sp., and scattered Bassia sp., Aglaia sp. and Dipterocarpus tonkinensis with a total of 1000-1500 trees/ha. Growth of trees seems to be normal in the rehabilitated grass and tree layer, with an annual increment in height of 0.7-1.0m and in diameter 0.7-0.9 cm. Big, pioneering trees (Styrax tonkinensis, Litsea cubeba, Trema angustifolia) are replacing small, pioneering trees. Forest conditions seem to be rehabilitated: forest soil is cool and moist; fern species, Phrynium parviflorum and Alpinia globosa exist.
2. Total labour costs from seedling production to a uniformly grown, 3 year old forest is only half the normal cost and can be calculated as follows:
120 man days + 3.5 days per 1 ha for Pasania ducampii
115 man days + 30.5 days per 1 ha for Machilus bonii
The results show that this regeneration method can be applied in an area where there is a moist climate and rainfall ranges from 1500 to 2000 mm/yr, and it can be applied to tropical monsoon evergreen forests which have been exploited many times and now belong to IIIa1, IIIa2 forest types with regenerated trees of large tree species with a density of more than 2000 trees per ha. The slope cannot be more than 30 degrees and soil depth is more than 30 cm. In areas where large and small wood pieces can be easily used, this method is more favourable because it can take advantage of firewood which originated from cutting of old forests.
CONCLUSION
The research aimed to complete seedling production in order to reduce the cost of planting. The next problem is to investigate husbandry measures in order to achieve a complete regeneration system.
The Scientific and Technical Council of the Forest Research Institute approved the methods for regeneration of IIIa1 and IIIa2 forest types by using Pasania ducampii and Mechilus bonii as being correct. At the same time, the Council emphasized the pharmaceutical value of Machilus bonii and disadvantages such as narrow distribution area, low quantity of seed, damage by stem borers at 4-5 years of age, and also the advantages of Pasania species such as low requirement for soil, effect of rapid soil improvement and large quantity of seed.
The Council agreed to recommend that these results be classified as a technical advance in the 1978s.
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- study on techniques to impove poor forest regeneration at vule by using machilus bonii and pasania ducampii ( 1968-1969 and 1972-1977)
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