Geographic variation of growth traits in early stage for Melia azedarach among different provenances

ObjectiveThis paper aims to provide theoretical basis and technical reference for seed allocation and silviculture of fast growing timber plantation in Melia azedarach. The variance of growth traits among various provenances was estimated. Furthermore, the pattern of geographic variation was studied to reveal the underlying climatic and ecological foundations.

MethodSix traits, including tree height, DBH, clear bole height, stem form, crown and survival rate of 62 provenances (15 provinces in China), were investigated, and the descriptive statistics analysis, variance analysis, Pearson correlation analysis, canonical correlation analysis and trend surface analysis were performed using SPSS 20.0, SAS 9.0, Surfer 13.0 and EXCEL 2011, respectively.

ResultThe results showed that most provenances had well growth in Sihui Experimental Site of Southern China, and each trait had significant differences or highly significant differences among intra-provenances and inter-provenances. Tree height and DBH of the best one were 8 and 12 times of the worst one, respectively, and for crown it was 23 times. The geographic variation of Melia azedarach was influenced by multiple factors, including longitude, latitude and altitude, among which latitude plays the major role. The growth of Melia azedarach was mainly regulated by temperature, but also was affected by sunshine, precipitation and air pressure. The 62 provenances could be divided into 5 types. There were obvious differences between groups, and they followed the phenological division within a group.

ConclusionThe variance of traits had obvious geographic variation patterns and certain eco-climate foundation. In the south-to-north distribution and the west-to-east distribution, growth gradually became better and stem-form quality was being higher. In the meantime, survival rate fell as altitude increased. The provenances with mildly extreme temperature and pressure, higher mean minimum temperature and more precipitation had growth advantages. Latitude is a key factor in temperature change, so the pattern of zonal variation and the regulation of temperature decrease are inseparable from the increase of latitude. To explore the Melia azedarach regularity of geographic variance compressively with the evidences of molecular genetic analyses, the further studies will pay continuous attention to the growth state in Sihui Experimental Site of southern China.