Evaluation of Eucalyptus red gum species and provenances for inland humid subtropical regions of southern China

Abstract

ABSTRACTThere is a long history of eucalypt planting in inland regions of southern China where humid summers and frequent winter frosts and extreme cold events are features of the climate. Although early eucalypt plantings suffered widespread failures, some species managed to survive with individual trees in some plantings growing to impressive sizes with diameter at breast height (DBH) exceeding 50 cm. One of the most productive and best adapted species in the plantings was Eucalyptus camaldulensis. Two species–provenance trials were established in southern and central Hunan province in 2006 primarily to explore the potential of E. camaldulensis and the related E. tereticornis, but also to provide comparisons with two other species with potential for the climate. The trials included 65 provenances representing six taxa from four species: E. camaldulensis, E. tereticornis, E. amplifolia and E. macarthurii. Three provenances represented improved seed sources from Africa, whilst the others were natural stand provenances. Eucalyptus amplifolia var. amplifolia demonstrated the best potential for growth and survival up to age 5 years. Eucalyptus macarthurii had the best cold tolerance, but relatively poor performance for growth and survival. Both E. tereticornis and E. camaldulensis demonstrated reasonable cold tolerance, but growth and survival of E. camaldulensis var. camaldulensis provenances from temperate to subtropical climatic areas with dry summers and winter-dominant rainfall (Köppen climate classification Csa) were markedly inferior than those of E. tereticornis ig. ‘tereticamal’ and E. tereticornis ssp. tereticornis sourced from tropical and subtropical environments with summer-dominant rainfall (Köppen climate classifications Aw and Am). Seedlots of E. camaldulensis, E. tereticornis and E. macarthurii from improvement programs in Zimbabwe and South Africa mostly proved inferior to or no better than the best natural stand provenances of the same species in the Hunan environment.