华南地区桉树/相思混交种植的林木生长效应

Growth effect of eucalyptus-acacia mixed plantation in South China

将桉树U6与厚荚相思按不同比例和不同模式进行混交种植,测定二者的生长参数.结果表明:2～3年生混交林中,随着桉树比例的增大,相思免受风害的效果越来越显著,桉树/相思混交比例为3∶1时,风害率下降了26.14%;但不同处理间桉树或相思保存率没有显著差异;桉树/相思混交种植对相思生长有一定抑制作用,混交林中相思胸径约为其纯林的90%,混交种植虽对桉树高生长影响不明显,但对胸径生长有显著促进作用,并随相思比例的增加而越发明显.6年生的桉树/相思1∶1混交林分,桉树胸径>15cm所占比例达到了32.1%,而桉树纯林仅为5.83%;桉树/相思2∶1株间混交的种植模式使总生物量达到最大,为198.8m3.hm-2,是桉树纯林的118.8%,相思纯林的169.9%;桉树与相思混交种植对大径材桉树的培育是一种理想的种植模式.

Eucalyptus U6 and Acacia crassicarpa were mixed planted with different ratios and modes to investigate the growth parameters of the two tree species. In the 2-3 years old mixed plantation, the wind-throw of A. crassicarpa decreased markedly with increasing ratio of Eucalyptus U6, the decrement being 26. 14% when the Eucalyptus U6/A. crassicarpa ratio was 3： 1, but the survival rates of Eucalyptus U6 and A. crassicarpa had no significant difference under different planting modes. Mixed planting retarded the A. crassicarpa growth to some extent, with the DBH being 90% of that in pure A. crassicarpa stand. The mixed planting had little effects on the height growth of Eucalyptus U6, but promoted its DBH growth markedly, and the beneficial effect increased with in- creasing ratio of A. crassicarpa. In the 6 years old 1 ： 1 Eucalyptus U6/A. crassicarpa plantation, the Eucalyptus U6 individuals with DBH 〉 15 cm occupied 32. 1% ; while in pure Eucalyptus U6 stand, they only accounted for 5.83%. Mixed planting with 2：1 Eucalyptus U6/A. crassicarpa could obtain a maximum total biomass of 198.8 m^3·hm^-2 , which was 118.8% of the total biomass in pure Eucalyptus U6 stand, or 169.9% of that in pure A. crassicarpa stand. Mixture of Eucalyptus with Acacia would be a good choice to produce Eucalyptus trees with larger DBH.