基于粗糙集的林木冠层结构和光分布对净光合速率影响研究

Effects of canopy structure and solar radiation distribution on net photosynthetic rate based on rough set theory

以广东省东莞市大岭山森林公园33个乡土树种为研究对象,使用半球面影像技术和Li-6400光合仪分别获取林木冠层结构、光分布和光合作用指标,用方差分析和粗糙集理论进行评价。结果表明,林冠开度、叶面积指数、林下直射光、林下散射光、透光率和净光合速率均在各树种间存在极显著差异(p<0.0001),各指标在树种间的变化幅度也各不相同,其中林冠开度、林下直射光、林下散射光和透光率的变化幅度均超过了20%,分别为29.95%、20.40%、23.77%和22.56%,而叶面积指数和净光合速率的变化幅度分别为3.24和7.80。林冠结构和光分布均对林木净光合速率有重要贡献,但其影响程度不同。其中林冠开度最大,重要值为1/11,其余几项指标对光合作用的重要性相同,为2/33,略小于林冠开度的重要性。在评价林木冠层结构和光分布对净光合速率的综合影响力中,林冠开度贡献的权重最大,为0.27,林下直射光、林下散射光和透光率贡献的权重均为0.18。冠层结构和光分布对林木净光合速率的综合影响力在一定程度可指示冠层结构和光分布的合理性,与林木净光合速率大小不存在线性正相关关系,它只表明冠层结构和光分布对林木净光合速率的影响程度。

By taking the 33 native trees species in Dalingshan Forest Park in Dongguan city of Guangdong province as the studied objects, using hemispherical photography technology and Li-6400 portable photosynthesis system, the tested tree species’ canopy structure, solar radiation distribution and photosynthesis indexes were investigated and measured, and then the observed results were evaluated with variance analysis and rough set theory. The results indicate that there were very significant differences of canopy openness, leaf area index, transmitted direct solar radiation, transmitted diffuse solar radiation, transmitted total solar radiation and net photosynthetic rate respectively among tree species （p〈0.0001）, and the amplitude of inter-specific variations of all these 6 indexes were not the same. The amplitude variations of canopy openness, transmitted direct solar radiation, transmitted diffuse solar radiation and transmitted total solar radiation were all more than 20.000%being such as：29.95%, 20.40%, 23.77%, 22.56%, respectively, while those of leaf area index and net photosynthetic rate were 3.24 and 7.80, respectively;the canopy structure and solar radiation distribution both had significant effects on net photosynthesis rate of the forests, however, the influenced degrees were different, the canopy openness contributed the most significance, its’ important value was 1/11, and the others indexes had the same significance to the net photosynthesis rate, all being 2/33, a little less than that of canopy openness;while comprehensively evaluating the effects of canopy structure and solar radiation on net photosynthesis rate, the canopy openness contributed the most weight （0.27） and the leaf area index, transmitted direct solar radiation, transmitted diffuse solar radiation, transmitted total solar radiation contributed the same weight of 0.18;the comprehensive impacts of canopy structure and solar radiation distribution on net photosynthesis rate, which can be an indication of rationality of canopy structure and solar radiation distribution in some degrees, was not positively correlated with net photosynthetic rate absolutely, only to showed the degree of effects of canopy structure and solar radiation distribution on photosynthesis. The Rough Set Theory, a method which didn’t rely on specialists’ opinions but objective data to reveal potential information, was used to evaluate the effects of canopy structure and solar radiation distribution on photosynthesis in this research. And the result of this evaluation is more objective and more reliable.