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Open AccessArticle

Leaf Physiological Responses to Drought Stress and Community Assembly in an Asian Savanna

1
Department of Forest Inventory and Sustainable Forest Management, Silviculture Research Institute, Vietnamese Academy of Forest Sciences, No. 46, Duc Thang, Bac Tu Liem, Ha Noi 100000, Vietnam
2
School of Ecosystem and Forest Sciences, The University of Melbourne, 500 Yarra Boulevard, Richmond, VIC 3121, Australia
*
Author to whom correspondence should be addressed.
Forests 2019, 10(12), 1119; https://doi.org/10.3390/f10121119
Received: 3 November 2019 / Revised: 15 November 2019 / Accepted: 6 December 2019 / Published: 8 December 2019
(This article belongs to the Section Forest Ecophysiology and Biology)
Deciduous dipterocarp forest (DDF) is the most extensive forest type in continental Southeast Asia, but across much of its range is functionally more similar to tropical savannas than tropical forests. We investigated water relations and drought responses of the four dominant tree species (two Shorea and two Dipterocarpus species) of the DDF in central Vietnam to determine how they responded to prolonged periods of drought stress. We quantified leaf water relations in nursery- and field-grown seedlings of the four species and conducted a dry-down experiment on 258 seedlings to study leaf water potential and morphological responses of the seedlings following the drought stress. The two Shorea and two Dipterocarpus species differed significantly in leaf water potential at turgor loss point and osmotic potential at full turgor, but they showed similar responses to drought stress. All species shed leaves and suffered from stem loss when exposed to water potentials lower than their turgor loss point (approximately −1.7 MPa for Dipterocarpus and −2.6 MPa for Shorea species). Upon rewatering, all species resprouted vigorously regardless of the degree of leaf or stem loss, resulting in only 2% whole-plant mortality rate. Our results suggest that none of the four deciduous dipterocarp species is drought tolerant in terms of their water relations; instead, they employ drought-adaptive strategies such as leaf shedding and vigorous resprouting. Given that all species showed similar drought avoidance and drought-adaptive strategies, it is unlikely that seasonal drought directly influences the patterns of species assembly in the DDF of Southeast Asia. View Full-Text
Keywords: drought stress; water potential; Dipterocarps; tree mortality; resprouting drought stress; water potential; Dipterocarps; tree mortality; resprouting
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Nguyen, T.T.; Arndt, S.K.; Baker, P.J. Leaf Physiological Responses to Drought Stress and Community Assembly in an Asian Savanna. Forests 2019, 10, 1119.

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