Research on the Technique of the Microhabitat Regenerating

Wang Jinxi Xu Jinduo (Sichuan Research Institute of Forestry) (Forestry Institute of Ganzi Prefecture) Qiao Guanghui Xie Guocheng (Daofu Forestry Bureau) (Luhuo Forestry Bureau)

hilly area of the plateau; microhabitat; regeneration

The hilly area of the plateau in the upper reaches of the Yangtze River is a weak zone as far as its forest ecological environment is concerned. In recent years,the overcutting of forests has made the originally adverse natural conditions still worsened. The old silvicultural techniques have difficulty in adaption to the regeneration of forests in this zone and thus the survival rate of regeneration is very low. Researches have shown that unfavourable factors affecting forest regeneration are as follows;the accumulated temperature in the growing season of younglings is on the low side .and the accumulated temperatures of≥10℃ range only from 500 to 1300℃;the cutover land has a heavy deficit of moisture content,and the amount of deficit in a year reaches 200 to 300 mm:the moisture temperatures are unco-ordinated in the early growing season of younglings;and younglings are often trampled by oxen or sheep. For this reason,a corresponding technique, namely the regeneration of microhabitat,should be adopted ,including strict selection of tree species and sea-sons for regeneration and use of stumps on the cutover land to bring about a favourable microhabitat for the growth of regenerated younglings. And moreover, such silvicultural measures as refining in narrow strip, land preparation in small hole and shading of cuttings can raise the regeneration efficiently. According to the determination of multiple indicators, the microhabitat created by this technique has shown an evident improvement in hydrothermal conditions for the growth of younglings. For example, the water content of soil has increased by 10 to 15% ,the transpiration strength of younglings reduced by 20 to 30% ,the mean daily relative water content in needles raised by 4. 6% ,and the mean daily value of natural saturation deficits of moisture in needles decreased by 6% ,thus making the survival percent of regeneration rise by 20 to 40%. Additionally,this technique is now in common use in the local silvicultural production.