Abstract: With the seeds from nine natural Cyclocarya paliurus populations as test materials, their phenotypic traits, including 1000-seed weight, seed size, seed diameter, seed thickness, and seed diameter/thickness ratio, were investigated, and the phenotypic diversity among and within the populations were studied by the methods of ANOVA analysis, hierarchical cluster analysis, and correlation analysis. Significant differences were observed in the 1000-seed weight, seed size, seed diameter, and seed thickness among and within the populations, and in the seed diameter/thickness ratio within the populations, illustrating that there existed high phenotypic diversity of seed traits at these two levels. The mean phenotypic differentiation coefficient (V) of test seed traits was 20.54%, i.e., the variation among the populations was far smaller than that (79.46%) within the populations. The seed traits had different correlation degrees with geographical factors, and most affected by mean annual air temperature. According to the hierarchical cluster analysis based on the Euclidean distance, the nine natural Cyclocarya paliurus populations could be classified into three groups.

Key words: Cyclocarya paliurus, natural population, seed traits, phenotypic diversity, subalpine forests, soil labile nitrogen pools, growing season, non-growing season, western Sichuan.