摘要:全球气候变暖强烈影响树线交错带植物的生活史策略，异龄叶大小-出叶强度权衡关系是常绿植物生活史策略的重要内容。以川西树线交错带的岷江冷杉（Abies faxoniana）幼苗为例，研究气候变暖对异龄叶大小与出叶强度关系的影响。通过开顶箱（Open-top chamber， OTC）对川西王朗自然保护区树线交错带的岷江冷杉进行模拟增温，采用标准化主轴估计（Standardized major axis estimation， SMA）方法研究了叶大小（单叶质量、单叶面积）与出叶强度（基于茎生物量、茎体积）间异速生长关系对长期增温的响应及其年际变化。结果表明：使用不同参数表征叶大小与出叶强度得到的结果存在差异；多年生小枝上存在单叶质量-出叶强度的负等速权衡关系，共同主轴随小枝年龄增加而向下漂移；长期增温并不影响单叶质量与出叶强度的异速生长关系，不同年龄小枝的异速生长常数对增温具有差异性响应。增温处理中当年生小枝在相同单叶质量下的出叶强度更低，以换取叶片总数的增加，使小枝具有更大的可塑性而适应增温。本研究提供了岷江冷杉幼苗协调异龄叶大小与出叶强度从而适应长期增温的证据，为评估树木生长随气候变化而加速提供了理论参考。



Abstract:Global warming has strong effects on life history strategies of plants located in the cold regiones such as alpine treeline ecotone. More studies have paid attentions on the shift of leaf traits (e.g. photosynthesis and leafing intensity). However, the trade-off different-age leaves between leaf size and leafing intensity of evergreen plants within treeline ecotone in the future warming scenario is still limited, which is important to understand life history strategies of evergreen plants. In this article, in situ open-top chambers were used to simulate warming effect on A. faxoniana seedlings in the treeline ecotone of Wanglang National Natural Reserve, western Sichuan Province. Our objectives were to test whether the negative and isometric relationship between leaf size (individual leaf biomass and individual leaf area) and leafing intensity (based on stem biomass and stem volume) could be found in different-age stems(current-year, 1 a; 2 a and 3 a), and explore the effects of simulated warming on the relationship between leaf size and leafing intensity. Standardized major axis estimation method was used to examine the scaling relationship between leaf size and leafing intensity within stems at different ages. The results showed that allometric relationships were different when leaf/stem size was expressed as different traits. Constantly, there were negative and isometric scaling relationships between individual leaf biomass and leafing intensity in stems of different ages. The intercept with common slope decreased with increasing stem ages. Long-term warming did not shift the negative and isometric scaling relationships between individual leaf biomass and leafing intensity. Allometric constants of stems at different ages responded differently to long-term warming. Under the same individual leaf biomass, current-year stems within the open-top chambers had lower leafing intensity, in exchange for an increase in the total number of leaves, so that current-year stems had greater plasticity, hence it could adapt to global warming and grew better in the treeline ecotone. Although the effect of simulated warming would decrease with increasing stem ages, the whole plant would still accumulate more biomass. These findings suggested that A. faxoniana seedlings could adapt to global warming by coordinating leaf size and leafing intensity in different-age stems, and provided the evidence for the acceleration of tree growth with climate waming, as changes in plasticity of stems allowed plants to accumulate more biomass.





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