摘要:城市化过程会引起周边环境要素的改变，而这种变化是否会对植物功能性状产生影响目前尚不清楚。选择我国亚热带常绿阔叶林优势树种木荷（Schima superba Gardn.et Champ.）为研究对象，分别在杭州市中心（HZ）、郊区（FY）及偏远地区（JD）3个位置采集阴生和阳生枝条样品进行植物枝条功能性状测定，并对各功能性状在3个区域间的差异性以及阴生阳生枝条功能性状间的差异性进行双因素方差分析（Two-way ANOVA）和多重比较（Tukey法），对所有区域的功能性状与环境气象因子进行相关分析。结果表明，从JD到HZ，阳生枝条水力结构性状枝条密度（ρ），叶片比叶面积（SLA）及叶枝比（A_L∶A_S）逐渐降低，而边材导水率（K_S）则逐渐增加。而阴生枝条除了A_L∶A_S不受影响以外，其他水力结构性状也存在相同的变化趋势。在叶片气体交换能力上，阳生枝条叶片最大净光合速率（A_n），蒸腾速率（E_l）以及气孔导度（g_s）均从JD到HZ逐渐增加，其中HZ的阳生枝条E_l是JD的2.8倍，而水分利用效率（WUE）以及¹³C同位素丰度（δ¹³C）则逐渐降低。阴生枝条除了A_n不存在显著差异以外（P > 0.05），其他与阳生枝条也具有相同的变化趋势。此外，阳生和阴生枝条的对比结果表明，除了WUE和δ¹³C，两者的各功能性状均存在显著差异，并且阳生枝条对于城市化的环境效应的敏感性更高。植物水力结构性状和叶片气体交换功能性状之间存在显著相关性（P<0.05），尤其是K_S与叶片气体交换能力（A_n，E_l）。而3个区域温度（T_a）和水汽压亏缺（VPD）的变化对植物水力结构性状的影响较大。这些结果表明，城市化会导致植物的生存策略向高气体交换能力-低水力安全阈值转变。



Abstract:Urbanization will induce substantially environmental changes. However, the potential effects of urbanization on plant functional traits are still not understood. In this study, the dominant species Schima superba Gardn. et Champ. was selected to measure the plant leaf and shoot functional traits under both sunlit and shaded conditions along the urbanization gradients (including urban site HZ, suburban site FY and rural site JD) around the urban center Hangzhou. Two-way analysis of variance (Two-way ANOVA) and multiple comparisons (Tukey) were conducted to analyze the differences of those traits among the three studied sites, and the differences between sunlit and shaded traits for different sites, as well as the sensitivity to the urbanization were also compared. Pearson correlation analysis was adopted to detect the relationships among these functional traits and the meteorological factors of the three sites. The Two-way ANOVA indicated the co-varying of these functional traits due to the urbanization. Specifically, the hydraulic traits including shoot density (ρ), specific leaf area (SLA), and leaf shoot ratio (A_L:A_S) were found to decrease, while the sapwood area specific hydraulic conductance (K_S) increased significantly. The shaded traits shifted in the same way, with the exception of the A_L:A_S. As to the gas exchange traits, the sunlit leaf maximum photosynthetic rate (A_n), transpiration rates (E_l), and stomatal conductance g_s increased from JD to HZ sites, among which, the E_l at HZ site was 2.8 folds of that at JD site. The water use efficiency (WUE) and abundance of ¹³C (δ¹³C) in HZ was also decreased significantly. Besides, the shaded traits shared the same pattern with the exception of the A_n(P > 0.05). In addition, the comparisons between sunlit and shaded traits showed significant difference between these two groups and the sunlit traits had higher sensitivity in response to the urbanization. Our results indicated that plants hydraulic traits and gas exchanges traits were highly related, especially for the relationships between K_S and the A_n, E_l (P<0.05). Besides, the variation of temperature (T_a) and vapor pressure deficit (VPD) have significant effect on the hydraulic traits. These results could provide some evidence that urbanization would lead to the shift of survival strategies into high gas exchange ability and low hydraulic threshold.





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