A STUDY ON PROMOTING SEED STANDS OF PINUS YUNNANENSIS TO BLOSSOM AND BEAR FRUIT

The timber quality of Pinus yunnanensis is decereasing mainly because the low-grade seeds in genetic quality are used to afforest. In order to ensure the timder guality of Pinus yunnanensis and to raise the economic value of stand, it is necessery to use the high quality seeds to afforest, to set up the base of ine quality seed sources and to make the scedtrees bear more fruits earlier. The authors of this paper have been experimenting on the seed stand of Pinus yunnanensis on Baima River forest farm in Yongren County, Yunnan Rovince. Having spent four years planning, constructing, observing and analysing, they got the following results. The seed production increased by 265%, 175.32%, 43.76% and 87.66% respectively by applying nitrogen fertilizer and the trace element of boron to the seed trees, and by injecting gibberellin and potassium permanganate into trunks of the trees while the crown shaps were changed and fruiting layer and crown surface area were widened afterthe trees were pruned. All these methods could not change the heredity of seed trees of Pinus yunnonensis, but could increase the seed production of the seed trees and be easy and convenient to be used in practice. The seed-producing depardment was suggested to use them.