南京地区落叶栎林木本植物叶物候研究

LEAF PHENOLOGY OF WOODY SPECIES IN DECIDUOUS BROAD-LEAVEDOAK FORESTS IN NANJING AREA, EAST CHINA

叶物候参数长期以来被认为与植物的碳获取的最大化有关,能反映物种的资源利用策略。温带地区因为寒冷冬天的限制,延长叶寿命成为一些物种进行生长发育和繁衍的基础。为探讨叶寿命延长的可能途径(早出叶、晚落叶,或两者兼有),该研究以南京地区两个落叶栎(Quercusspp.)林为研究对象,观测了其中木本植物的出叶物候、落叶物候,并分析了它们与叶寿命之间的关系。结果发现1)不同物种的出叶开始时间相差较大,出叶早的物种早结束出叶过程;2)不同物种的落叶开始时间相差较大,早开始落叶的物种,落叶持续时间较长,落叶结束时间则相对集中。3)相关分析和回归分析都表明,叶寿命与出叶时间和落叶时间显著关联,但早出叶对叶寿命的延长可能更为重要,因为早出叶相对于晚落叶在物种资源利用上比较具有优势。4)不同物种的出叶时间和落叶时间没有显著相关,可能因为出叶过程和落叶过程是由不同的启动因子引起。这说明延长叶寿命不一定同时通过早出叶和晚落叶来达到。

Leaf phenology has long been thought to evolve to maximize plant carbon gains, and it reflects plant life history strategies for exploiting resources. Extending leaf life span is of great importance for some species of temperate deciduous forests to gain enough carbon needed for plant survival and persistence, because their growing seasons are repeatedly interrupted by cold winters, leaf life span can be extended by early leafing, late shedding, or both. To examine which approach was employed to maximize leaf longevity, the phenology of leaf emergence and abscission was investigated for species of two deciduous bread-leaved oak forests in Nanjing area, East China, and the relationships between leaf phenological parameters were analyzed. The timing of leaf emergence differed greatly among species. The earlier the species leafed out, the earlier the species ended the process of leaf emergence; the earlier a species leaf began to abscise its leaves, the longer it took to end the process of leaf abscission. Consequently, the leaf abscission for all species was completed within a narrow time period although the start of leaf abscission differed greatly among species. Both correlation analysis and regression analysis indicated close relationships between leaf longevity and the timing of leaf emergence and abscission, in which a longer leaf life span was related to early leafing and late shedding. The timing of leaf emergence seems more important for plant carbon gain than the timing of leaf abscission, assuming that early leafing has advantages over late shedding for carbon gain for the woody species living in the study region. No significant relationship was found between the timing of leaf emergence and leaf abscission indicating that long leaf longevity could be achieved by either early leaf emergence or late leaf abscission. Early leafing is not necessarily correlated to late shedding for the study species.