Abstract:

Ten crown structure indexes were measured and investigating poplar canker disease state was investigated on all the individuals in a poplar plantation. Based on the collected data relationships of crown structure with the disease state of the poplar individuals was analyzed. The results showed that height under branch (H _ub),crown width (W),first-order branch angle (A _fb),first-order branch diameter (D _fb),percentage of crown length with height(CL/H),crown shape ratio (CSR),leaf area index (LAI),total leaf area (TLA) and crown surface area (CSA) of non-diseased plants were larger than diseased plants,while,canopy layer density (CLD)of non-diseased plants was smaller than diseased plants. Poplar canker severity(CS) was very significantly negatively correlated with W,H _ub,CL/H ,CSR and CSA and very significantly positively correlated with CLD； The order of the direct effect on CS was CLD＞A _fb＞W>CSR＞D _fb＞CL/H >TLA>CSA＞H _ub＞LAI. The direct effect of TLA,CSA,H _ub,LAI on CS was negative,restrained poplar canker from developing ,and the direct inhibition of LAI was the largest. Lastly,the integrated effect of D _fb,CL/H ,A _fb,CSR,W ,LAI on CS was negative. In these six crown structure indexes,LAI,having the largest negative decisive effect,can be regarded as primary limiting factor,and the second was W.

Key words: Populus bolleana, crown structure, poplar canker, disease state