Spatial and seasonal variations of leaf area index (LAI) in subtropical secondary forests related to floristic composition and stand characters
Spatial and seasonal variations of leaf area index (LAI) in subtropical secondary forests related to floristic composition and stand characters
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与植物区系组成和林分特征相关的亚热带次生林叶面积指数（LAI）的空间和季节变化
DOI：
10.5194/bg-13-3819-2016
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发表时间：
2016
期刊：
影响因子：
4.9
通讯作者：
Changhui Peng
中科院分区：
文献类型：
--
作者：
Wenjuan Zhu;Wenhua Xiang;Qiong Pan;Yelin Zeng;Shuai Ouyang;Pifeng Lei;Xiangwen Deng;Xi Fang;Changhui Peng
叶面积指数(LAI)是一个与冠层与大气之间的碳、水和能量交换有关的重要参数，被广泛应用于模拟森林生态系统生产和水文循环的过程模型中。然而，在中国亚热带森林中，叶面积指数的细尺度空间异质性及其控制因素尚未得到充分的了解。2014年4月至2015年1月，利用半球照相法对马尾松常绿阔叶混交林、落叶阔叶林和青冈常绿阔叶林三种亚热带森林的叶面积指数进行了测定。分别用地统计学方法和广义加性模型(GAMS)分析了叶面积指数的空间异质性及其控制因素。结果表明，三种林分叶面积指数差异较大，其季节变化与植物物候特征一致。1月份测得的三种森林的LAI值表现出很强的空间自相关性，4月、7月和10月测得的光肩星天牛群落的LAI值表现出很强的空间自相关性。三种林分的LAI值在非生长期均出现明显的斑块分布格局，随着生长季节的变化，这种格局逐渐减弱。枝条数、冠幅、断面积常绿针叶树种比例、断面积落叶树种比例和森林类型影响1月份LAI值的空间变异，而7月份落叶树种的空间变异受茎条数和落叶树种比例的影响。在间接测定叶面积指数和应用叶面积指数模拟亚热带森林功能过程时，应考虑植物区系组成、空间异质性和季节变化的抽样策略。
Leaf area index (LAI) is an important parameter related to carbon, water, and energy exchange between canopy and atmosphere and is widely applied in process models that simulate production and hydrological cycles in forest ecosystems. However, fine-scale spatial heterogeneity of LAI and its controlling factors have yet to be fully understood in Chinese subtropical forests. We used hemispherical photography to measure LAI values in three subtropical.forests (Pinus massoniana–Lithocarpus glaber coniferous and evergreen broadleaved mixed forests, Choerospondias axillaris deciduous broadleaved forests, and L. glaber–Cyclobalanopsis glauca evergreen broadleaved forests) from April 2014 to January 2015. Spatial heterogeneity of LAI and its controlling factors were analysed using geostatistical methods and the generalised additive models (GAMs) respectively. Our results showed that LAI values differed greatly in the three forests and their seasonal variations were consistent with plant phenology. LAI values exhibited strong spatial autocorrelation for the three forests measured in January and for the L. glaber–C. glauca forest in April, July, and October. Obvious patch distribution pattern of LAI values occurred in three forests during the non-growing periodand this pattern gradually dwindled in the growing season. Stem number, crown coverage, proportion of evergreen.conifer species on basal area basis, proportion of deciduous species on basal area basis, and forest types affected the spatial variations in LAI values in January, while stem number and proportion of deciduous species on basal area basis affected the spatial variations in LAI values in July. Floristic.composition, spatial heterogeneity, and seasonal variations should be considered for sampling strategy in indirect LAI measurement and application of LAI to simulate functional processes in subtropical forests.