Biomass allocation differences with Pinus massoniana in Guangdong and Hubei provenances

To analyze biomass allocation in the process of productivity formation in man-made forests of fast- and slow-growing provenances, Masson pine (Pinus massoniana), an important man-made forest species in south China, was used. Different mechanisms of long-term adaptation in the two provenance types were also discussed. The allocation patterns of above- and below-ground biomass in Guangdong and Hubei provenances were analyzed by using the whole plant harvest method. According to differing diameter at breast heights (DBH), the analytic trees were grouped into three classes:12 cm ≤ DBH < 18 cm, 18 cm ≤ DBH < 26 cm, and 26 cm ≤ DBH < 34 cm. Results showed that (1) The maximum of annual growth of Guangdong provenance reached 0.015 m3·a-1 in 25 years and the average annual growth of Guangdong provenance reached 0.011 m3·a-1 in 30 years. In addition, the maximum of annual growth of Hubei provenance reached 0.011 and 0.007 m3·a-1 in 30 and 42 years, respectively. (2) A large proportion of biomass was distributed to the underground part in Guangdong provenance. There were significant differences in the crude root biomass of the two provenances (P < 0.05). With the increasing of chest diameter, the relative difference were 36.5%, 62.9% and 47.5%, respectively, while there was no significant difference in the biomass between the fine roots. In the DBH range from 26 to 34 cm, there were significant differences among the biomass of the whole plant, the aboveground part, the tree trunk and the conifer (P < 0.05). (3) The biomass allocation proportion of Hubei provenance for the whole growth process in the 3 DBH classes was lower than that of the Guangdong provenance. At the initial stage of growth, the total biomass of the trunk in the Hubei provenance was higher than that in the Guangdong seed source; whereas, the biomass allocation proportions of branches and leaves was lower. As tree age increased, the proportion of total biomass for the tree trunk in the Guangdong provenance was gradually higher than that in the Hubei provenance and tended to be stable. However, the results were opposite in the branches and leaves. Therefore, the growth characters and the biomass of tree trunks showed the characteristic of rapid growth in Guangdong provenance, while quantitative maturity age was earlier than that in Hubei provenance.