海南岛尖峰岭12种热带常绿阔叶乔木展叶期与开花期对气候变化的响应

Responses of leaf unfolding and flowering to climate change in 12 tropical evergreen broadleaf tree species in Jianfengling, Hainan Island

为了探讨我国热带地区植物物候与气候变化的关系,利用海南岛尖峰岭热带树木园12种热带常绿阔叶乔木植物2003–2011年物候观测资料结合同期月平均气温和降水数据,运用积分回归分析方法,筛选出影响海南岛12种乔木(8种本地种、4种引入种)展叶始期与开花始期的气象因素以及不同气象因素月值变化(月平均气温和月降水量)综合作用对这些树种物候期的动态影响,最终建立积分回归-物候预测模型,对气候变化背景下我国热带地区植物物候变化趋势进行了预测。结果表明:海南岛12种热带常绿阔叶乔木展叶始期与开花始期均对气候变化做出较明显的响应,几乎所有的树种展叶始期与开花始期的发生都受到气温和降水的共同影响。多数树种展叶始期受展叶前冬季及春季气温影响显著,且在临近展叶始期的月份,气温的影响更显著。上一年秋季月降水量对各树种开花始期的影响比其他时段显著,这验证了降水的滞后性假说。本地种展叶始期对气候变化的响应比其开花始期对气候变化的响应更敏感,引入种则相反。各树种展叶和开花在受气温和降水综合影响最明显的月份(假设其余11个月份月平均气温和月降水量不变),月平均气温升高0.1℃、月降水量增加10 mm可使展叶始期和开花始期提前或推迟1–3天。积分回归分析方法为解释海南岛热带常绿阔叶乔木物候与气温和降水的动态关系提供了有效的途径,基于气温和降水与物候资料建立的积分回归-物候预测模型具有对气温和降水变化影响下物候响应的解释率和预测精度高(R2≥0.943)的优点,对于预测气候变化影响下的植物物候变化趋势有一定的适用性。

Aims Our objective was to determine the impacts of climate change （mainly temperature and precipitation） on the phenology of tropical evergreen forests at the community and species level. Methods Two phenophases-the onset of leaf unfolding and the onset of first flowering--had been monitored in 12 evergreen broadleaf tree species in the tropical arboretum in Jianfengling, Hainan Island, since 2003. Observa- tions were made on three mature and healthy individuals for each species once every two days in the same sunny direction in the afternoon by the same person. After the phenological data were collected, they transformed into the number of days from the first day of a calendar year （DOY, i.e. from lth January）. The outliers were excluded used the Grubbs principle. Meteorological data for the corresponding time period were derived from the National Climate Centre. Ultimately, the phenological and meteorological data were combined with the integrate regression method and used to identify the impacts of changing climate on the onset of leaf unfolding and the onset of first flowering in the 12 tree species and to determine their responses in the two phenophases to climate change. Important findings Both the onset of leaf unfolding and the onset of first flowering in the tree species were af- fected by climate change; the starting dates of the two phenophases in nearly all the tree species were closely related to changes in monthly temperature and precipitation. The onset of leaf unfolding was affected by the monthly mean temperature of the preceding winter and spring, and the impacts became more apparent with the time approaching the occurrence of specific phenophases. Monthly precipitation in the preceding autumn had more effects on the onset of the first flowering than any other time period, in support of the hypothesis that the effect of precipitation on phenology had a hysteretic nature. Furthermore, the onset of leaf unfolding was more susceptible to climate change than the onset of first flowering in the native tree species, whereas the introduced tree species showed reversed responses. Generally, if the monthly mean temperature increases by 0.1 ~C and the monthly precipitation increases by 10 mm in the month with the strongest effects, and given that the conditions of other 11 months preceding the occurrence of the specific phenophases remains unchanged, then most of the species would advance or delay the phenophases by about one to three days. Ultimately, the Integrate Regression method provides an effective and operational approach to understanding the dynamic and complex relationships between climate change and the phenology in tropical plants, as demonstrated by the high values of the coefficient of determination （R2 〉/ 0.943） for the integrate temperature and precipitation regression models for phenological predictions based on climatic factors. These models can well be used for predicting the trend of phenological changes in tropical evergreen broadleaf tree species in response to changing climate.