Adaptability evaluations of Eucalyptus clones at six stand conditions in Southern China

Objective To evaluate scientifically the resistance and adaptability of Eucalyptus clones at different stand conditions, and provide a scientific basis for planting proper trees at different areas.

Method The adaptability of ten eucalyptus clones were compared at six sites in Guangdong and Guangxi Provinces. The survival rates, tree heights, diameters at breast height, incidence of disease, wind damage rates and volumes were studied.

Result Hybrid Eucalyptus clones kept excellent characteristics of strong adaptability, and the survival rates were above 95% except for LH9224(93.7%). There were large differences in disease resistance among clones at different sites. LH9224 had the highest incidence of disease (averaged over 6.7%), while LH9211 had the highest disease resistance with no diseased plant. The incidence of disease was the highest (3.63%) under heavy clay soil condition, and 0 under light sandy soil condition. There were significant differences in wind resistance among clones. Under the average wind speed of nine grade, the wind damage rates for the 1.5-year-old young forests ranged from 5% to 64%, DH3327 and DH3226 had the poorest wind resistance with above 60% wind damage rates, and LH9211, LH9224 and Sh1 had the highest wind resistance with below 10% wind damage rates. For the 6-year-old forests, M1 and DH2012 had the poorest wind resistance with above 12% windthrow rates under the 11-grade wind. There were highly significant differences in growth speed among clones, and the mean annual increments(MAI)for the 8.5-year-old forests ranged from 17.19 to 38.87 m³·hm^-2·a^-1. DH3213 at Qinlian had the fastest growth, while U6 at Qinlian had the least growth. The average MAI from six sites ranged from 12.24 to 26.97 m³·hm^-2·a^-1 for ten Eucalyptus clones.

Conclusion In typhoon-prone areas, LH9224 clone with strong wind resistance is suggested to be planted, while DH3213 and DH3327 clones are the desired strains for the inland areas with little wind damage. In Tangjia area with the lowest survival rate and the highest incidence of disease, we suggest planting M1 with the highest survival rate and LH9211 with the highest disease resistance, and for Wuchuan and Suixi areas with low volume production, the best choice is DH3213 with the fastest growth rate.