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Explaining the exceptional 4270 m high elevation limit of an evergreen oak in the south-eastern Himalayas
JournalItem (Reviews, Editorials, Rezensionen, Urteilsanmerkungen etc. in einer wissenschaftlichen Zeitschrift)
ID 4613093
Author(s) Yang, Yang; Sun, Hang; Körner, Christian
Author(s) at UniBasel Körner, Christian
Year 2020
Title Explaining the exceptional 4270 m high elevation limit of an evergreen oak in the south-eastern Himalayas
Journal Tree Physiology
Volume 40
Number 10
Pages 1327-1342
Mesh terms Carbon; Plant Leaves; Quercus; Seasons; Trees
Abstract Unlike the well-understood alpine treeline, the upper range limits of tree taxa that do not reach the alpine treeline are largely unexplained. In this study, we explored the causes of the exceptionally high elevation (4270 m) occurrence of broad-leaved evergreen oaks (Quercus pannosa) in the south-eastern Himalayas. We assessed the course of freezing resistance of buds and leaves from winter to summer at the upper elevational limit of this oak species. Linked to leaf phenology, we analyzed freezing resistance and assessed minimum crown temperature for the past 65 years. We also examined potential carbon limitation at the range limit of this species. Last season buds and leaves operated at a safety margin of 5.5 and 11 K in mid-winter. Once fully dehardened early in July, last season foliage is damaged at −5.9 and new foliage at −4.6 °C. Bud break is timed for late June to early July when low temperature extremes historically were never below −3.0 °C. The monsoon regime ensures a long remaining season (149 days), thus compensating for the late onset of shoot growth. Compared with a site at 3450 m, specific leaf area is reduced, foliar non-structural carbohydrate concentrations are similar and the δ13C signal is higher, jointly suggesting that carbon limitation is unlikely at the range limit of this species. We also show that these oaks enter the growing season with fully intact (not embolized) xylem. We conclude that the interaction between phenology and freezing tolerance results in safe flushing, while still facilitating shoot maturation before winter. These factors jointly determine the upper range limit of this oak species. Our study illuminates an exceptional case of broad-leaved evergreen tree performance near the treeline, and by exploring a suite of traits, we can underpin the central role of flushing phenology in such a stressful environment.
Publisher Oxford University Press
ISSN/ISBN 0829-318X ; 1758-4469
Full Text on edoc No
Digital Object Identifier DOI 10.1093/treephys/tpaa070
PubMed ID
ISI-Number WOS:000607844100002
Document type (ISI) Journal Article

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