Abstract
We investigated the growth of 5-year-old Eucalyptus sp. Regenerated secondary stand of sucker shoots. The results indicated that the survival shoot number 2 years after cutting varied widely. The surviving shoots decreased from the original 820 existing shoots per hectare to an average of 574 shoots. After 2 years, the surviving shoot number remained stable.In which the control plot has 546 plants per hectare; deshooting treatment retained 603 plants per hectare.In the 5-year forest, control plot retained 1809 shoots/ha; the deshooting plot retained 1119 shoots/ha. In the control plot, a single stump averaged 3.3±2.5 shoots with average dbh of 10.0±3.8cm and shoot length of 10.5±4.5 m ; in the deshooting plot, each stump retained 1.9±1.1 shoots with average dbh of 12.0±3.5 cm and shoot length of 11.6±3.8 m. The results also indicated that the dbh and height growth of shoots in deshooting plot was better than the control plot. The total dbh cross-sectional area in the control plot was 16.7 m2/ha; and in the deshooting plot was 13.6 m2/ha; The more shoots retained on thecontrol plot,caused that the total dbh crosssectional area of the deshooting plot was still poorer than did the control. However, the net dbh and tree height growths after deshooting were greater. In subsequent investigations, we hope to establish more clearly the effect of deshooting treatment. In a survey of natural regenerated seedlings in the secondary Eucalyptus sp. shoot forest, there were 363 plants belonging to 22 species; whereas in the deshooting forest, there are 567 plants of 27 species sprouting from seeds. The species appeared both in the control plots and deshooting include Acacia auricuriformis, Macaranga tanarius, Breynia officinalis, Aleurites montana, Murraya paniculata etc. The other plants present only scattering, such as Cinnamomum camphora, Melia azedarach and Gardenia jasminoides, indicating renewable species showed little variation.. However, the post-sprouting treatment released environmental resources can provide forest trees with a more varied regeneration opportunity, even facilitating seeding renewal of Eucalyptus urophylla. Comparing the emerging plant species, we found that the environmental resources released by deshooting treatment apparently allowed more plant species to take hold. Secondary planting of important endemic reforestation species of high economic values such as Acacia confusa, Swietenia macrophylla, Michelia compressa, and Pistacia chinensis in understories was also carried out. In 2015, the total survival rate after 4-year of all species averaged 64%. S. macrophylla had the highest surviving rate of 87% with average sapling height of 406.5±121.1 cm, the highest of all species; Acacia confusa had survived rate of 73%, with average sapling height of 303.2 ±120.5 cm . The survived rate of P. chinensish droped from 97% to 79% ,with tree height only of 193.6±73.1cm; M. compressa grew to a height of 83.4±65.2 cm, with survival rate of only 45%. These results are useful reference for selecting trees for understory planting in local planting programme.