栲树冠层光合生理特性的空间异质性

森林冠层在能量传输、光合有效辐射和微气象等方面的差异可导致冠层光合生产力空间分布的变化.叶片光合生理特性在空间上的差异对精确估算森林冠层的初级生产力十分重要.本文以亚热带常绿阔叶林优势种---栲树(Castanopsis fargesii)为对象,研究叶片光合生理特性在冠层空间上的变化.结果表明:1)在垂直方向上,冠层北向叶的饱和光合速率(Amax)、光饱和点(LSP)和CO2羧化效率(CCE)均表现为上部>中部>底部,且依次平均降低19.4%、18.1%和37.1%;光补偿点(LCP)、光下暗呼吸(Rd)以及冠层南向叶的饱和光合速率、光饱和点和CO2羧化效率均表现为上部>底部>中部,上部比中部和底部高出12.3%~71.4%;表观量子效率(AQY)表现为底部>上部>中部,底部分别是顶部和中部叶的1.2和1.3倍;2)在水平方向上,冠层上部和底部南向叶的饱和光合速率、光饱和点和CO2羧化效率比北向叶高0.9%~31.5%;冠层中部北向叶的饱和光合速率等6个参数比南向叶高9.6%~63.2%.因此,在冠层水平上模拟和估算植物生产力时,必须考虑冠层光合生理特性的空间差异.

Spatial heterogeneity of photosynthetic characteristics of Castanopsis fargesii canopy

The vertical and horizontal differences in the energy transmission,photosynthetically active radiation,and micrometeorological characteristics of forest canopy can lead to a considerable heterogeneity,which should be analyzed when estimating forest primary productivity.With Castanopsis fargesii,the dominant species in the subtropical evergreen broad-leaved forest in Tiantong National Forest Park of Zhejiang Province as test object,this paper studied the vertical and horizontal variations of photosynthetic characteristics of its canopy.Vertically,the photosynthetic indices such as maximum photosynthetic rate(Amax),light saturation point(LSP),and carboxylation efficiency(CCE)of north-facing leaves in the canopy all declined in the sequence of top canopy>mid-canopy>bottom canopy.The mean values of light compensation point(LCP),respiration in light(Rd),and Amax from top canopy to bottom canopy reduced by 19.4%,18.1% and 37.1%,respectively.The LSP and CCE of south-facing leaves followed the pattern of top canopy>bottom canopy>mid-canopy.These two indices decreased by 12.3% in bottom canopy and 71.4% in mid-canopy,compared with those in top canopy.The apparent quantum yield(AQY)of leaves followed the sequence of bottom canopy>top canopy>mid-canopy,being 1.1 and 1.3 times higher at bottom canopy than at top-and mid-canopy,respectively.Horizontally,the Amax,LSP and CCE of south-facing leaves at top-and bottom canopy were 0.9%-31.5% higher than those of north-facing leaves.In mid-canopy however,the values of test six indices of north-facing leaves were 9.6%-63.2% higher than those of south-facing leaves.It was suggested that in order to estimate and model forest primary productivity accurately,the vertical and horizontal heterogeneity of photosynthetic characteristics of forest canopy should be analyzed.