Meng Chen, Xu Ming-Ce, Li Jun-Xiang, Gao San-Ping
Department of Environmental Science, East China Normal University, Shanghai 200062, China.
Ying Yong Sheng Tai Xue Bao. 2007 Sep;18(9):1932-6.
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.
森林冠层的能量传输、光合有效辐射和微气象特征在垂直和水平方向上的差异会导致显著的异质性，在估算森林初级生产力时应予以分析。以浙江省天童国家森林公园亚热带常绿阔叶林的优势种栲树为试验对象，研究了其冠层光合特性的垂直和水平变化。垂直方向上，冠层北向叶片的最大光合速率（Amax）、光饱和点（LSP）和羧化效率（CCE）等光合指标均表现为冠层上部＞冠层中部＞冠层下部。从冠层上部到下部，光补偿点（LCP）、光呼吸（Rd）和Amax的平均值分别降低了19.4%、18.1%和37.1%。冠层南向叶片的LSP和CCE表现为冠层上部＞冠层下部＞冠层中部。与冠层上部相比，冠层下部和冠层中部的这两个指标分别下降了12.3%和71.4%。叶片的表观量子效率（AQY）表现为冠层下部＞冠层上部＞冠层中部，冠层下部的AQY分别比冠层上部和冠层中部高1.1倍和1.3倍。水平方向上，冠层上部和下部南向叶片的Amax、LSP和CCE比北向叶片高0.9% - 31.5%。然而，在冠层中部，北向叶片的六个测试指标值比南向叶片高9.6% - 63.2%。研究表明，为了准确估算和模拟森林初级生产力，应分析森林冠层光合特性的垂直和水平异质性。
