遮光对杉木幼苗树干表面CO_2通量的影响

Effects of shading on stem surface CO_2 effluxes of Chinese fir seedlings

树干表面CO_2通量是森林生态系统碳收支的重要组成部分,对全球碳平衡产生重要影响。近年来,全球变化导致植物光合产物供应发生改变,这将影响树干表面CO_2通量。然而,关于光合产物供应如何影响树干表面CO_2通量的机理仍不清楚。以盆栽杉木(Cunninghamia lanceolata)幼苗为研究对象,采用遮光方法减少光合产物供应,通过自制呼吸气室,使用Li-8100测定树干表面CO_2通量,并结合树干可溶性糖、淀粉和非结构性碳及树干温度等数据分析遮光对树干表面CO_2通量的影响。结果表明:遮光后树干可溶性糖、淀粉和非结构性碳含量分别显著下降了55.0%、78.9%和64.3%。遮光处理阶段树干表面CO_2通量平均下降39.9%,且下降幅度随着遮光时间的延长而增加;此外,遮光降低了树干表面CO_2通量的温度敏感性。恢复光照后,树干表面CO_2通量、树干可溶性糖、淀粉和非结构性碳含量以及树干温度均恢复至对照水平。可见,光合产物供应变化对树干表面CO_2通量具有调控作用,而且能够通过调控树干表面CO_2通量对温度变化的响应对全球碳循环产生重要影响。

Stem surface CO2 effluxes are an important part of the carbon(C)budget of forest ecosystems,which play an important role in sustaining global C balance.In recent years,global changes have altered the supply of plant photosynthates,and this could affect plant stem surface CO2 effluxes.However,the underlying mechanisms of how changes in plant photosynthates affect stem surface CO2 effluxes are still unclear.In the present study,potted Chinese fir(Cunninghamia lanceolata)seedlings were used,and shading was applied to alter the supply of photosynthate.We measured stem surface CO2 effluxes using a Li-8100 Automated Soil Gas Flux System,and measured the concentrations of stem soluble sugar,starch,non-structural C,and stem temperature to clarify the effects of shading on stem surface CO2 effluxes.The results showed that the concentrations of stem soluble sugar,starch,and non-structural C were significantly reduced by 55.0%,78.9%and 64.3%,respectively.The mean stem surface CO2 effluxes significantly decreased by 39.9%during shading,and the decrease rate gradually increased as shading time increased.Moreover,shading decreased the temperature sensibility of stem surface CO2 effluxes.The stem surface CO2 effluxes and the concentrations of stem soluble sugar,starch,non-structural C,and stem temperature were recovered after regaining normal light conditions,as compared with the control.These results suggest that the changes in photosynthate supply could affect stem surface CO2 effluxes and consequently global C cycling by regulating the response of stem surface CO2 effluxes to temperature.