Genetic Variation And Tree Improvement Of The Genus, Paulownia Sieb.et Zucc.

The genus of Paulownia including 9 species and 4 varieties is distributed in eastern Asia and all species and varieties of the genus occur in China. Paulownia trees grow in23 provinces, municipalities and autonomous regions, being important species to plantation forestry and agroforestry intercropping system. P. tomentosa and P. fortuneiii,24 provenances of P. tomentosa and 33 provenance of P. fortuneii, and 31 hybrid clones were studied. A randomized completely block design was used for the provenance trail of P. tomentosa, with 3 replicates each consisting of 10 plots planted with single line trees. For the hybrid trial and the clonal test, a randomized complete block design, with 4 replicates consisting of 6 plots with single line trees. Measurements were conducted for growth, tree crown, phenology, damages respectively by freezing and disease. The lab analyses were made for cell membrane penetrability, wood properties etc. Based on the data obtained from many years of field trials and the lab analyses, principal component analysis, single linkage cluster analysis, correlation analysis and gray regression analysis were conducted to study the geographical variation of P. tomentosa, the potential of introduction of P. fortuneii to areas out of its natural range, the performance of the inter-specific hybrids, the pattern of stem re-growth after topping, the variation in MLO and the wood properties. Main findings are summarized as follows:1 Significant geographic variation of growth traits was found within the range of P. tomentosa. In normal condition P. tomentosa does not suffer from freezing in the north of China. The higher the latitudes of a provenance, the earlier the seeds germinate. The height and the DBH (diameter at breast height) increase with the latitudes of the origin of the provenance. However, it is weakly correlated with the latitude. Year to year correlations indicates that selection of fast-growing trees can be reliably conducted atthe 5th year.The cluster analysis indicates that provenances can be divided into 3 groups, provenances from Anhui and Hubei provinces, provenances from Funiu Mountains, the central area of the distribution, Dalian, Taiyuan, Yanan and northern areas of the distribution, and provenances from Gansu and Shanxi, northeast part of the distribution. This finding corresponds to the geographical locations of the provenances.2 The species introduction trial of P. foriuneii indicated that the growth and adaptability varied greatly within the range of species. Majority of the provenances belonging to Yunnan, Guangxi, Guangdong were frozen to death in winter, leading to a lower survival rate. However, the north provenances displayed a higher survival rate. The conductivity test showed that survival rate was closely related with the field freezing rate, indicating the possibility of using conductivity to reveal extent of field freezing. The performance of different provenances was closely correlated with meteorological factors in the provenance origins. It was found that the low temperature had stronger influence than did the other factors. Results indicate that provenances from lower locations had higher survival rate. Provenances with lower mean annual temperature in their origins had smaller survival rate. No significant correlation was found between the precipitation and the survival rate and damage by freezing. The growth rate was not correlated with longitude of provenance origin, but significantly with latitude. Height and DBH (diameter at breast height) appeared to decline along with the increase of latitude.Provenances from areas with latitude lower than 26?displayed a survival rate of 56.69%, those from between 26皛29?showed a survival rate of 65.71%, those from latitudes higher than 29?had a survival rate of 74.59%. This indicates that the climatic conditions in Henan had significant impacts on provenances introduced from central to south of the distribution range of Paulownia.Gray connecting analysis indicates that Henan,Shanxi,Shanxi and the north from Shanxi are n...