A Bald Cypress Excellent Source Selection

Taxodium distichum (L.) is a venerable and relic plant originating from North America, which now is introduced to being planted all over the world. Taxodium distichum have many virtues just like rapid growth and widely adapted planting, the graceful shape of tree, the excellent wood property and it can be planted not only under wetland areas but also highlands for the production of timber, shelter belt and ornamental in most of China. To elucidate the difference of the different Taxodium distichum provenances in the bio-productivity, photosynthetic characteristics, wood physical and chemical properties, this investigation was carried out to study the bio-productivity, photosynthetic characteristics, wood physical and chemical properties of sixteen provenances of thirteen year-old Taxodium distichum (L.). In this paper, we also discussed the correlation coefficients of all indexes and screened out the fine provenances in order to provide the theoretic basis for widely planting Taxodium distichum.The results were as follows: (1) There were highly significant differences at 0.01 level among the Taxodium distichum provenances in growth traits of height, DBH (diameter at breast height) , tree volume and the above biomass. The differences of form factor among provenances were also greater and all the taper coefficients were more than the intensity-taper coefficients; (2) Broad-sense heritability among provenances varied from 5.99 to 39.06 percent. The broad-sense heritability of DBH was the biggest among all the genetic control of traits, and the broad-sense heritability of branch angle and branch number was the smallest; (3) There existed positive relationship at 0.05 level between growth traits such as height, DBH, tree volume and the width of tree crown. The regression equation based on the stem volume taken as attributive variable and the diameter at breast height (X₁) and height (X₂) taken as automatic variable was: Y=0.00577X₁+0.00436X₂-0.0628; (4) Synthetic result based on the compare with all the growth traits showed that the provenances of 12,9,6 were the best varieties; (5) There existed significant differences among 16 provenances in photosynthetic characteristics indexes like net photosynthetic rates, light use efficiency, transpiration rate, Stomatal conductance, transpiration rate, water use efficiency, initial fluorescence, maximum fluorescence, electronic transport rate, quantum efficiency of PS II and the primary light energy conversion of PSII, but the difference of intercellular CO₂ concentration was not obvious; (6) The diurnal courses of 16 provenances were distinguished two types: the provenances of the 4th, 5th, 6th, 7th, 12th, 15th, 16^th, 17th, 30th demonstrating single-peaked curve and the provenances of the 2nd, 3rd, 8th, 9th, 10th, 13th, 14th being dual- peaked curve; (7) There was a certain difference among the daily change and magnitude of net photosynthetic rates, water use efficiency and light use efficiency of 16 provenances in different layers of tree crown; (8) It showed the close correlation among the measured parameters of photosynthetic characteristics, between the parameters of photosynthetic characteristics and DBH. Path analysis based on the measured parameters of photosynthetic...