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在雨水充足的森林生态系统中光合有效辐射(PAR)是植物初级生产力的主要控制因子,同时也会对森林的垂直结构、群落组成和系统演替等产生重要的影响.为了研究秦岭典型地带性植被群落天然次生油松林近成熟龄阶段林内不同层次光合有效辐射(PARs)的时空分布特征及相互关系,在陕西宁陕县秦岭森林生态系统国家野外科学观测研究站油松林内4个层次(第1层:灌木层,PAR_1;第Ⅱ层:林冠下层,PAR_2;第Ⅲ层:林冠中层,PAR_3;第Ⅳ层:林冠顶层,PAR_4)对其PARs进行长期定位观测.本研究对2007和2008连续两年的实测数据进行分析研究结果表明:林冠结构对PARs影响显著,PARs从林冠顶层到灌木层垂直衰减十分明显.2007和2008年油松林PAR_4、PAR_3、PAR_2和PAR_1的年总量分别为7604.68和7939.77mol·m~(-2)、1436.70和1389.98mol·m~(-2)、1503.42和1392.12mol·m~(-2)、1000.68和917.11mol·m~(-2);全年相对光量子通量密度RPFD_3、RPFD_2、RPFD_1分别为18.89%和17.51%、19.77%和17.53%、13.16%和11.55%.PARs时间变化上表明,PARs月均值曲线2007年呈多峰变化,2008年呈单峰变化.PARs月均值均在5月份达到最高,最低值分别出现在12月份(2007)和1月份(2008).2007和2008年备层PARs全年日总量平均值间相差较小,春、夏生长季PARs日最高值和日平均值均明显高于秋、冬非生长季.
In a rainfed forest ecosystem, photosynthetically active radiation (PAR) is the main controlling factor of plant primary productivity, but also has an important impact on the vertical structure, community composition and system succession of forests.In order to study the typical zonal The temporal and spatial distribution characteristics of the photosynthetically active radiation (PARs) at different mature stages in the natural secondary forest of Pinus tabulaeformis plantation in the vegetation communities were studied in four levels (Pinus tabulaeformis) of the National Field Observation Station of Qinling Forest Ecosystem in Ningshan County, Shaanxi Province The first layer: shrub layer PAR_1; the second layer: canopy lower layer PAR_2; the third layer: canopy middle layer PAR_3; the fourth layer: canopy top layer PAR_4) The data from two consecutive years of study showed that the canopy structure had a significant effect on PARs, and the vertical decay of PARs from the canopy to the shrub layer was very obvious. The annual total amount of PAR_4, PAR_3, PAR_2 and PAR_1 in Pinus tabulaeformis forest in 2007 and 2008 were 7604.68 and 7939.77mol · m -2, 1436.70 and 1389.98mol · m -2, 1503.42 and 1392.12mol · m -2, 1000.68 and 917.11mol · m -2, respectively. Relative light quantum flux density RPFD_3, RPFD_2, and RPFD_1 were 18.89% and 17.51%, 19.77% and 17.53%, 13.16% and 11.55%, respectively.The changes of PARs showed that the monthly average PARs showed a multi-peak curve in 2007 and a single peak in 2008. PARs The monthly average reached the highest in May and the lowest appeared in December (January 2007) and January (2008) respectively. The difference between the average daily total of PARs in 2007 and 2008 was small, and the spring and summer growing season PARs daily maximum and daily average were significantly higher than the autumn and winter non-growing season.