北京松山林下典型灌木绣线菊光、水利用效率的季节动态及其对环境因子的响应

目的]植物资源利用效率是反映植物对环境条件适应性的重要指示指标,是气候变化生态学领域的研究热点,因此对林下灌木物种光能利用效率(LUE)和水分利用效率(WUE)的环境调控机理需进一步明晰。方法]以北京松山天然阔叶林下典型灌木绣线菊(Spiraea salicifolia)为研究对象,于2019年6月至9月完全展叶期开展原位叶片光合测定和同步环境因子的连续观测,分析了绣线菊LUE和WUE的变化特征及其对环境因子的响应。结果]LUE和WUE具有较为明显的季节变化特征,其中LUE随着光合有效辐射(PAR)和空气温度(T_a)的变化呈现逐渐增大的趋势,季节平均为0.03 mol/mol; WUE随PAR和空气饱和水汽压差(VPD)的变化呈现先增大后减小的趋势,季节平均为8.32 μmol/mmol。PAR和T_a是影响LUE变化的主要因子,分别为指数和线性负相关; PAR和VPD是影响WUE变化的主要因子,均与WUE呈线性负相关,其中VPD通过影响气孔导度(g_s)限制叶片蒸腾,从而影响WUE; LUE、WUE的季节变化和土壤含水量(SWC)均无显著相关性。LUE与WUE对环境因子存在趋同响应关系。结论]研究初步确定光合有效辐射、空气温度和空气饱和水汽压差是研究区林下灌木绣线菊资源利用效率的主要限制因子,而非土壤水分; 林下灌木绣线菊在有限资源条件下呈现资源保守策略,具体表现为在光能受限的条件下能够最大限度地使用光能进行光合作用,从而具备较高的光能利用效率。

Seasonal Dynamics in Light and Water Use Efficiency of a Typical Shrub Spiraea salicifolia in Understory and Its Response to Environmental Factors in Songshan of Beijing

Objective]Resource use efficiencies are key indicators for acclimation of a plant to environmental conditions, which is one of the main concerns in the area of climate change ecology. The controlling machanisms of light use efficiency(LUE)and water use efficiency(WUE)of understory shrub species in response to environmental changes remain unclear. Methods] The seasonal variation in LUE and WUE and its envrionmental controls for an understory shrub, Spiraea salicifolia, in a typical deciduous forest in Songshan of Beijing were examined through in-situ measurements of leaf photosynthetic parameters and environmental factors in the full leafing stage from June to September 2019. Results] LUE and WUE showed obvious seasonal variations, averaging 0.03 mol/mol and 8.32 μmol/mmol, respectively. Photosynthetically active radiation(PAR)and air temperature(T_a)were the main factors controlling the LUE, showing an exponential and a linear negative relationship, respectively. PAR and vapor preassure difference(VPD)were the main factors controlling WUE, with which both showed the linear negative relationship. The VPD limited transpiration by affecting stomatal conductance(g_s), which affected WUE. The seasonal variation in both LUE and WUE was not affected by soil water content(SWC). There was convergency between LUE and WUE in response to environmental factors. Conclusion] PAR, T_a and VPD, rather than SWC, were the main limiting factors for resource use efficiencies of the shrub Spiraea salicifolia in understory of the research area. The shrub Spiraea salicifolia in understory showed a resource conservation strategy under the condition of limited resources, specifically, under the condition of limited light, the shrub Spiraea salicifolia in understory maximized the use of light energy for photosynthesis and thus had a high light energy utilization efficiency.