滇中常绿阔叶林下滇青冈幼苗净光合速率对土壤水肥的响应

Responses of Net Photosynthetic Rate of Cyclobalanopsis glaucoides Seedlings to Soil Nutrient and Water Contents in Evergreen Broad Leaved Forest of Central Yunnan

为了探讨不同季节土壤水肥配置下幼苗叶片净光合速率的差异及其相互关系,本文对滇中高原常绿阔叶林林下土壤表层水肥的动态变化、滇青冈实生幼苗的叶片养分含量及其净光合速率进行了监测与分析。对不同季节间的比较与相关性分析表明:(1)土壤全氮、全钾、速效钾及有机质全年保持稳定,但全磷和有效磷呈下降趋势,而碱解氮表现为先增加后降低趋势。整体来看,除碱解氮外,土壤养分的全量及有效含量经过雨季均有不同程度的下降;(2)7月时幼苗叶片的氮、磷、钾含量最低。与7月相比,5月、9月与11月叶片养分含量均有显著的增加(P<0.05);滇青冈幼苗叶片在500μmol/(m^2·s)光照下净光合速率表现为5月的净光合速率最高,达到2.89μmolCO_2/(m^2·s),7月的净光合速率最低,为1.46μmolCO_2/(m^2·s);光合养分效率的季节变化呈先降低后增加的趋势,其中9月的光合养分利用效率最低;(3)林内土壤表层养分含量、滇青冈幼苗叶片中的养分含量及其净光合速率三者之间没有显著的相关性。雨季后期土壤磷素的缺乏可能是影响叶片净光合速率与光合养分效率的主要因子。

To understand responses of net photosynthetic rate of Cyclobalanopsis glaucoides seedlings to different combinations of soil nutrients and water in central Yunnan,the upper soil nutrient and water contents,the leaf nutrient contents and net photosynthetic rate of C.glaucoides seedlings were measured in different months.The results showed that:(1)The contents of soil total nitrogen(TN),total potassium(TK),rapidly available K,and soil organic matter remained a relative stabilization,but the total phosphorus(TP)and available P displayed the decrease trend,available N showed a increasing then decreasing change.As a whole,the different degrees of decrease were found for all soil nutrients except available N after the rainy season;(2)N,P,K concentrations in leaf were the significantly lowest in July comparing to other months;The net photosynthetic rate(Pn)of seedlings under the same light intensity〔500μmol/(m^2·s)〕was the highest〔(2.89μmolCO 2/(m^2·s)〕in May and the lowest〔1.46μmolCO 2/(m^2·s)〕in July;The photosynthetic nutrient use efficiency in different months displayed a decreasing then increasing trend,and photosynthetic nutrient use efficiency was the lowest in September;(3)No significant correlations were found among the upper soil nutrition,the leave nutrition and net photosynthetic rate.Base on above results,it is thought that the different disposition of water and fertility,particularly the deficient phosphorus in later stage of rainy reason,was the main soil ecological factor influencing the net photosynthetic rate and photosynthetic nutrient use efficiency.