Why Do Some Evergreen Species Keep Their Leaves for a Second Winter, While Others Lose Them?

Forests

Peter J. Grubb²  Christine L. Thompson¹  Geoffrey H. Harper¹ 

[1] Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh EH3 5LR, UK; E-Mails:;Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EA, UK

关键词: leaf longevity;    dry winters;    Yunnan;    subtropical montane semi-moist forest;    Rhododendron;   

DOI  :  10.3390/f5112594

来源: mdpi

【 摘 要 】

In subtropical montane semi-moist forest in SW China (SMSF), a large majority of evergreen tree and tall shrub species was found to have only one cohort of old leaves in early spring. In contrast, almost all species of evergreen tree and tall shrub in warm temperate rain forest (WTRF) in Japan and sclerophylls in Mediterranean-climate forest (MSF) of the Mediterranean Basin have two or more cohorts of old leaves in early spring; they drop their oldest cohort during or soon after leaf outgrowth in spring. Japanese WTRF has no dry season and MSF a dry summer. SMSF has a dry winter. On four evergreen Rhododendron species from SW China with only one cohort of old leaves in spring when in cultivation in Scotland, the majority of leaves in the senescing cohort fell by the end of December. We hypothesize that with dry winters, there is an advantage to dropping older leaves in autumn, because there is a low chance of appreciable positive assimilation in winter and a high chance of desiccation, reducing the resorption of dry mass and mineral nutrients from ageing leaves. Our hypothesis may be extended to cover evergreens at high altitude or high latitude that experience cold soils in winter.

【 授权许可】

CC BY   
© 2014 by the authors; licensee MDPI, Basel, Switzerland.