Early performance of Pinus radiata provenances in the earthquakeravaged dry river valley area of Sichuan, southwest China

A provenance experiment involving five native provenances and an Australian landrace of Pinus radiata (D. Don) was established over three sites in the dry river valley area of Sichuan, southwest China in 2004 in order to select the most suitable provenance for environmental planting on the dry, steep and degraded slopes to reduce soil erosion. Although with much lower soil moisture supply and mean minimum temperatures in winter compared to P. radiata provenance trials established elsewhere in the world, these sites are within the working limits of the species defined by previous climate modelling and matching. Because of the difficult site conditions and severe natural disturbances after the experiment was established, mortality was high across the three sites in comparison to provenance trials in other countries. The average mortality rate among the provenance by replicate planting units over the three sites varied from 16% to 76% four years after planting, and from 40% to 88% five years after planting. The repeated measurements of tree size over time were analysed using multilevel linear mixed models to derive growth curves for the mean, median, the 75th and the 90th percentiles of the size distribution of each provenance at each site. There were significant site effects on tree growth, but no significant interactions between site and provenance was detected. Among the six provenances, Cambria was the best performer in diameter, height and stem volume growth across all sites. The better than average and the best trees of this provenance, as represented by the 75th and 90th percentiles of the nominal stem volume distribution, were significantly larger than the Australian landrace, Año Nuevo, and the two island provenances, Guadalupe and Cedros. Monterey was overall the second best performer behind Cambria. The Australian landrace, Guadalupe and Año Nuevo had similar performances in general. Cedros was significantly and consistently inferior to all other native provenances and the Australian land race. Because the genetic base of the present Australian plantations was derived largely from Año Nuevo and Monterey, the superior early growth performance of Cambria at such difficult sites brings a new promise to the search of P. radiata provenances for the vast dryland areas in New South Wales and other parts of Australia.