引种保护植物对西双版纳极端冷年的春季物候响应

Spring Phenology of Introduced Species in Response to Extreme Chilliness in Xishuangbanna Tropical Botanical Garden

气温被普遍认为是春季物候期最主要的控制因子之一,然而低温对植物物候的影响效应一直都存在不同的观点。西双版纳由于地处热带地区的北缘,其气温相对于赤道附近的热带地区较低。自1959年以来,西双版纳热带植物园引入了来自世界各个热带地区的4万余种植物进行保护,之前的研究证明西双版纳的低温对这些引种植物的生长有很大影响。因此,1974年西双版纳出现的极端低温势必对引种植物造成极大威胁,同时也是对这些植物低温适应能力的一个考验。通过对比43种引种植物物候期(生长抽梢期与开花期)在1974年与常年的差异情况,分析不同来源(热带亚洲、热带美洲与热带非洲)引种植物对西双版纳低温的适应性。结果表明,经历西双版纳1974年初的极端低温之后,使81%的引种植物生长抽梢期提前,同时也造成35%的引种植物在该年没有开花;而植物生长抽梢提前的主要原因则是极端低温以及低温过后气温迅速回升。引种植物均能顺利度过1974年的最冷时期,并出现生长抽梢物候,这意味着引种植物在经历极端低温之后都能够进行正常的生长活动,但极端低温对引种植物繁殖活动的不利影响大于其对生长活动的影响;引种植物对西双版纳极端低温的适应能力由大到小顺序依次为:亚洲来源植物>美洲来源植物>非洲来源植物。因此在迁地保护植物的选择过程中,应多选择亚洲热带植物,其次为美洲热带植物,而对非洲热带植物的引入则需谨慎考察。

Temperature is widely considered to be one of the most important factors affecting the spring phenophases,such as leaf flushing and flowering.However,different viewpoints still exist as to the effect of the low temperature.Xishuangbanna（in China）,which is located in the northern part of the tropics,has a lower temperature than the equatorial tropical regions.Since 1959,the Xishuangbanna Tropical Botanical Garden（XTBG） has introduced more than 40 000 tropical plant species for conservation from all over the world.The low temperature of the garden is a key factor significantly affecting the growth of these plants.The extreme chilliness that occurred in 1974 was a threat to the plants and also a test of their cold resistance.In this study,we compared the spring phenology（leaf flushing and flowering） of 43 introduced plants in 1974 with that of plants in other years and evaluated their cold resistance by different origins（Asian tropics,American tropics and African tropics）.In total,81% of the plants showed advanced leaf flushing because of both the extreme chilliness and the rapid temperature rebound afterwards.The chilliness also caused non-flowering in 35% of the plants.Successful flushing after chilliness represents a good vegetative cold resistance for all the species;however,the progenitive phenophase was more adversely affected by the chilliness.According to the performance of their spring phenology,species from Asian tropics showed the best cold resistance with the highest species percentage of flowering（83%） and the fewest shifts in phenotypic durations after the chilliness.Species from the American tropics were next highest in flowering and phenotypic durations,then African species.Hence,species from the Asian tropics should be considered first for ex situ conservation in Xishuangbanna,and African species must be carefully introduced.