Study On Growth Rhythm And Undergrowth Management Models Of Six Poplar Clone Plantations

The results showed that the six poplar clones existed significant differences in growth characteristic, the increment of the six poplar clones'height,DBH,volume followed P.×euramericana cv.'L35'> P. deltoides'Zhonghe1'> P.×euramericana cv.'I-107'> P. deltoids cv.'I-69'>P.deltoides cv.'L323'> and P.×euramericana cv.'zhonglin46'by high to low. No matter the growths of height,DBH or volume , P.×euramericana cv.'L35'was the best, and suitable for growth and development in the alluvial flatlands flooded by the Yellow River. So growth of P.×euramericana cv.'L35'was the most advantageous clone which evidently better than the other poplar clones in the same cultural condition, P.×euramericana cv.'zhonglin46'was the worst. Compared with P.×euramericana cv.'zhonglin46', P.×euramericana cv.'L35'increased by 117.39% in height,respectively by 127.60% in DBH and especially by 118.27% inolume. P. deltoides'Zhonghe1'approximates P.×euramericana cv.'zhonglin46'in height's increment, P.×euramericana cv.'I-107'approximates P. deltoids cv.'I-69'and P.deltoides cv.'L323'; P. deltoides'Zhonghe1'approximates P.×euramericana cv.'I-107'in DBH's increment, P. deltoids cv.'I-69'approximates P.deltoides cv.'L323'and P.×euramericana cv.'zhonglin46'; P.×euramericana cv.'I-107'approximates P. deltoids cv.'I-69', P.deltoides cv.'L323', P.×euramericana cv.'zhonglin46'Comparison of shape few showed that the form of P. deltoides'Zhonghe1', P. deltoids cv.'I-69'and P.×euramericana cv.'zhonglin46'better than P.×euramericana cv.'L35', P.×euramericana cv.'I-107'and P.×euramericana cv.'zhonglin46'.The study of poplar clones'growth forecast showed that the height's growth, DBH's growth and volume's growth appeared to be'fast-slow-fast'growth rhythm,and it might be well expressed by Logistic equation (R=0.99468,P<0.0001). The height's limit value of P.×euramericana cv.'L35'was the biggest in the different clones, it was 20.4249m; the DBH's limit value of P.×euramericana cv.'L35'was the biggest also, it was 27.8978cm, and P. deltoides'Zhonghe1'taken second place, the differences among P. deltoids cv.'I-69', P.deltoides cv.'L323'and P.×euramericana cv.'zhonglin46'were slight; the volume's limit value of P.×euramericana cv.'L35'was the biggest too, it was 0.7566m3, and P. deltoides'Zhonghe1'taken second place, P.deltoides cv.'L323'and P.×euramericana cv.'zhonglin46'were the least.The study of growth stages and growth characteristic of these clones showed that the growth process could be divided into three stages: early growth stage, rapid stage and late growth stage. The rapid growth stage was the major decision in the growth of height, DBH and volume. It was recommended intensify the tending of the trees during their rapid growth stage so as to promote the volume growth to the greatest extent while reduce the tending cost for the timber production.The DBH growth process of the ten-year P.×euramericana cv.'I-107'analyzed by sequential cluster analysis showed that it could be divided into three growth stages, and basically coincided with that of Logistic equation, which further verified the feasibility to modulate the growth rhythm of this poplar clone with.The studies in the mature age of polar clones have shown that : in the density of 4 m×6 m, the economic mature age of each polar clone implodes on the year of 21～24,and varies due to the different strain of the clones. Among that , P.×euramericana cv.'I-107''reaches to the Economic mature age earliest at the year of 21, behind which P.×euramericana cv.'L35', P. deltoids cv.'I-69', P.deltoides cv.'L323'follows at the age of 22; P. deltoides'Zhonghe1'is the latest at the year of 24;additionally,the Economic mature age of P.×euramericana cv.'zhonglin46'is 23.From the quantitative mature age, the quantitative mature age of each poplar clone concentrates on the year of 10～12. P.×euramericana cv.'I-107'and P.×euramericana cv.'L35'reach to the quantitative mature age earliest at the year of 10, P. deltoides'Zhonghe1'is latest at the year of 12; moreover, the quantitative mature age of other clones is 11.From the technological mature age, in addition to P.×euramericana cv.'L35'and P. deltoides'Zhonghe1'other 4 clones all reach to the technological mature age ,which demonstrates that P.×euramericana cv.'L35'and P. deltoides'Zhonghe1'are appropriate to cultivate large-diameter timber(Frederick-foot diameter of 26cm - 36cm) or (Frederick-foot diameter of more than 38cm), and other clones are suitable for fostering the medium- diameter timber(Frederick-foot diameter of 14cm-24cm).Choose the same site conditions and management level of the P.×euramericana cv.'I-107'under different intercropping woodland, and analysis of different forest economic models impact on the cost-effectiveness. By analyzing the various modes of input-output ratio, establishing the best cultivation mode during the young poplar in order to improve forest production and land use , and providing the scientific basis for the intensive cultivation of poplar plantations and operation of decision-making. The research of forest economic models showed that: Early intercropping could increase the economic benefits of poplar plantations, and intercropping increased earnings obviously. Inter-planting of different crops make different income levels: control (not intercropping)