Variation in Leaf Traits among Different Indocalamus Germplasms and Their Responses to Environmental Factors

To investigate the variation patterns in leaf functional traits and ecological stoichiometric characteristics among different Indocalamus germplasms and to elucidate their adaptive mechanisms to geographical environmental factors, 12 wild Indocalamus germplasms collected from mountainous regions of southwestern China were selected for this study. The sampling sites covered the Daba Mountains in northeastern Chongqing, the Wuling Mountains in southeastern Chongqing, as well as Zhenba County in Shaanxi Province and Sangzhi County in Hunan Province. The materials comprised 11 Indocalamus species and one conspecific germplasm originating from a different geographical population. Mature and healthy leaves were collected to determine leaf functional traits, including leaf area, specific leaf area, leaf dry matter content, and leaf shape index, as well as leaf carbon (C), nitrogen (N), and phosphorus (P) concentrations and their stoichiometric ratios. Analysis of variance, correlation analysis, principal component analysis, and redundancy analysis were employed to examine trait variation and the environmental drivers underlying these variations. The results showed that both leaf functional traits and ecological stoichiometric characteristics differed highly significantly among the Indocalamus germplasms (P<0.01). Among the leaf functional traits, leaf area exhibited relatively large variation, with a maximum coefficient of variation of 25.38%. Specific leaf area showed the most pronounced differences among germplasms, whereas leaf shape index exhibited relatively limited variation. Among the ecological stoichiometric characteristics, leaf C concentration was the most stable, with coefficients of variation ranging from 0.33% to 2.71%, whereas leaf P concentration showed relatively large variation, with the coefficient of variation reaching 22.98% in I. tessellatus. Marked differences in leaf traits were observed among germplasms. I. longiauritus exhibited the largest leaf area (271.70 cm²), whereas I. henryi had the smallest leaf area (45.83 cm²). I. hispidus showed the highest leaf C concentration (401.80 g kg⁻¹), while I. wuxiensis exhibited the highest leaf P concentration (1.87 g kg⁻¹). Correlation analysis revealed a significant positive correlation between leaf area and specific leaf area (P<0.05), whereas specific leaf area was significantly negatively correlated with leaf dry matter content (P<0.05). Redundancy analysis indicated that altitude was the primary environmental factor influencing leaf traits and ecological stoichiometric characteristics, explaining 60.1% of the variation, and was positively associated with increases in leaf C, N, and P concentrations and leaf dry matter content. In contrast, increasing temperature promoted increases in specific leaf area and leaf shape index.