人工覆盖地表对北京典型绿化树光合特性的影响

地表硬化影响城市绿化树生长及生态服务功能的发挥,研究人工覆盖地表下城市绿化树关键生理过程具有重要意义.采用田间模拟试验方法,布设对照(自然地表)、透水硬化和不透水硬化3种覆盖地表,栽植北京2种典型绿化树白蜡和元宝枫,栽植后第4年野外测定其叶片光合及相关生理生态参数,分析人工覆盖地表对北京典型绿化树光合特性的影响.结果表明:白蜡和元宝枫光合作用对不同人工覆盖地表的响应存在差异,对于白蜡而言,透水硬化和不透水硬化地表均使其净光合速率显著降低,对于元宝枫而言,仅不透水硬化地表导致其净光合速率显著降低,透水硬化地表并未对其造成显著影响.透水硬化和不透水硬化地表的空气相对湿度和土壤体积含水率低于对照,植物可利用水分减少,叶片气孔导度下降是白蜡和元宝枫净光合速率降低的主要原因.透水硬化和不透水硬化地表使白蜡PSⅡ有效光化学量子产量(F_v′/F_m′)下降,不透水硬化地表使元宝枫PSⅡ实际光化学量子效率(Φ_PSⅡ)和表观电子传递速率(ETR)升高.

Impact of land pavement on photosynthetic characteristics of common greening trees in Beijing,China

Land pavement has impacted urban tree growth and its ecosystem service, and it is necessary to investigate the key physiological processes of urban trees grown under land pavement. To study the impact of land pavement on photosynthetic characteristics of common greening trees in Beijing, a field experiment was designed with three treatments: the control (the non-paved), pervious pavement and impervious pavement, and the leaf net photosynthetic rates and related physiological-ecological parameters of two common greening trees (Fraxinus chinensis and Acer truncatum) in Beijing were measured in the 4^th year after planting. Results showed that the photosynthesis of F. chinensis and A. truncatum showed different responses to different types of pavement, the net photosynthetic rate was significantly decreased for F. chinensis under both pervious and impervious pavements and for A. truncatum only under impervious pavement. The air relative humidity and soil volumetric water content under pervious and impervious pavements were lower than that under the control, which reduced water amount available for trees. The lower net photosynthetic rates of F. chinensis and A. truncatum under impervious pavement were mainly attributed to the decrease in leaf stomatal conductance. The PSⅡ effective photochemical quantum yield (F_v′/F_m′) of F. chinensis was significantly lower under pervious and impervious pavements, while the PSⅡ actual photochemical quantum efficiency (Φ_PSⅡ) and apparent electron transport rate (ETR) of A. truncatum were significantly higher under impervious pavement.