Early growth evaluation and biomass allocation differences of Cupressus funebris clones and families

Abstract Clonal forestry offers the opportunity to increase yields, enhance uniformity and improve wood characteristics. Evaluation of growth differences between clones and families has rarely been studied in slow-growing Cupressus funebris species, and whether such growth differences are related to biomass allocation patterns remains to be revealed and is essential for assessing the genetic selection potential and carbon sink capacity of superior species. We studied the genetic variation, heritability (replication power) and gain levels of 36 clones and 33 families of superior trees and analysed their biomass allocation patterns. The results showed that the early growth of Cupressus funebris was dominated by high growth, and the clones grew rapidly, with 253.36% and 51.77% higher diameter at breast height and height at 8 years old than the family lines, respectively. However, the genetic variation of growth traits in the families was higher than that of the clones. The clone repeatability and family heritability levels were evaluated. According to the 10% selection rate, the genetic gains of DBH and tree height of clones were 39.53% and 24.23%, respectively, 5.22 times and 2.05 times the genetic gains of families. The ratio of narrow and broad heritability of each trait was estimated to be 0.55–0.68, with an average value of 0.63, indicating that clones obtained higher additional genetic gains through nonadditive effects. The growth advantage of the clones was to increase the biomass of the aboveground part (86.03%) at the expense of the belowground biomass allocation, which was mainly reflected by the proportion of branch and leaf biomass allocation. The branches and leaves of the clones were dominated by the middle and upper layers, which accounted for 180.64% and 60.14%, respectively, while the middle and lower layers of the branches and leaves of the family lines accounted for a higher percentage. The model ln W=k0+k1 lnD + k2 lnH +k3 has the best prediction of biomass and could be used for early genetic evaluation of Cupressus funebris. In general, Cupressus funebris clones are fast growing and will help to improve the productivity and carbon storage of stands through genetic selection and utilization.