鹤山丘陵3种人工林叶面积指数的测定及其季节变化

Measurement of leaf area index of three plantations and their seasonal changes in Heshan hilly land

叶面积指数(LAI)是反映森林冠层结构的重要参数,通常情况下,用光学仪器测定的LAI值偏低需要进行校正。该文使用数码植物冠层图像仪(CI-110 DPCI)测定鹤山丘陵3种人工林(马占相思林、针叶林和荷木林)的有效叶面积指数(LAIe),用直接测定法得出的LAI对LAIe进行校正,并分析冠层LAI的季节变化特征。结果表明:LAIe明显低于LAI,两者存在密切的相关关系(P<0.01);拟合的经验方程适用于校正相应林分的LAIe。3种人工林冠层的LAI总体上没有明显的季节变化;荷木林的年平均LAI最高(6.56),其次为马占相思林(3.94),针叶林最低(3.76),荷木林的LAI明显高于另两种人工林(P<0.05)。结合历史数据可发现:荷木林的LAI呈明显上升趋势;马占相思林则相反,呈下降趋势;针叶林的LAI处在相对平稳期,反映不同森林类型的生长发育状态。

Leaf area index （LAI） is an important parameter in forest canopy structure. Measurement values of optical instrument often underestimate LAI and need to be corrected. Effective leaf area index （LAI,） measured by a CI-110 digital plant canopy imager （DPCI） was calibrated by LAI in three plantations of Acacia mangium plantation, Schima plantation （S. superba ＋ S. wallichi ） and coniferous plantation （Pinus massoniana ＋ Cunninghamia lanceolata） in Heshan hilly land, Guangdong Province, South China. Direct determination was used to estimate LAI of three plantations,and the seasonal changes of LAI were analyzed as well. Direct estimations were higher than optical estimations, and significant correlations （ P 〈 0.01 ） were found between LAI and LAI, for each plantation with different equations. There weren＇ t obvious seasonal changes of LAI in three plantations as a whole. Schima plantation had the highest mean annual LAI （6.56） among the plantations,followed by A. mangium plantation （3.94） and coniferous plantation （3.76）,and LAI of Schima plantation was obviously higher than those of A. mangium and coniferous plantations （ P 〈 0.05）. Compared with historical data, the results suggest that LAIs of Schima,coniferous and A. mangium plantations present the definite trend of increase, relative stabilization and decrease, respectively.