哀牢山亚热带常绿阔叶林光合有效辐射的时空分布

Spatiotemporal distribution pattern of photosynthetically active radiation in subtropical evergreen broadleaved forest in Ailaoshan Mountains of Southwest China

光合有效辐射(PAR)是影响生态系统能量转化和物质生产的重要生态因子,对其时空格局的研究,有助于深入理解生态系统的生理生态因子变化和光合行为。本研究分析了2009年哀牢山亚热带常绿阔叶林生态系统PAR的时间与垂直分布特征及相互关系。结果表明,在日尺度上,PAR在进入冠层内部的过程中,其强度不断减弱;各层次PAR月总量的年变化不尽相同,冠层上在2月和1月分别达到最大值和最小值。冠层上的PAR(PAR1)的日均变化呈单峰曲线,冠层底部(PAR2)、乔木亚层(PAR3、PAR4)和灌木层(PAR5)则为不规则的单峰曲线;各层全年PAR总量分别为8824.98、682.20、403.09、216.62、208.52mol.m-2。全年PAR2-PAR5占PAR1的比率分别为7.73%、4.57%、2.45%和0.92%;雨季各层次PAR的平均值分别为干季的89.77%、89.34%、97.32%%、116.36%和115.09%。

Photosynthetically active radiation （PAR） is an important ecological factor affecting the energy transformation and matter production of plant ecosystem. Studies on the spatiotemporal distribution patterns of PAR in a plant ecosystem are helpful to understand the physiological and ecological characteristics and photosynthesis of the ecosystem. In this paper, the temporal and vertical distributions of PAR in a coniferous and subtropical evergreen forest in Ailaoshan Mountains of Southwest China were analyzed. At daily scale, the intensity of PAR during passing through the forest canopy decreased gradually. At monthly scale, the PAR flux varied in each forest layer, with the maximum and minimum values above the canopy in February and January, respectively. The diurnal change of the PAR above the canopy （ PARl ） presented a single-peak curve, while that of the PAR at the bottom of the canopy （ PAR2 ） and in the arbor sub-layers （PAR3 and PAR4 ） and shrub layer （PARs ） presented an irregular single-peak curve. The PAR1, PAR2, PAR3, PAR4 and PARs fluxes at yearly scale were 8824.98, 682.20, 403.09, 216.62 and 208.52 mol , m-2, and the ratios of yearly PAR2, PAR3, PAR4 and PARs to PAR1 were 7.73%, 4.57%, 2.45% and 0.92%, respectively. The average PAR1, PAR2, PAR3,PAR4 and PAR5 in rain season were 89.77% , 89.34% , 97.32% % , 116.36% and 115.09% of those in dry season, respectively.