Selection of drought-resistant tree species by morphological, physiological, and biochemical traits

Narayan Bhusal, Minsu Lee and Hyun-Seok Kim, Department of Forest Sciences, Seoul National University, Seoul, Korea, Republic of (South), Hojin Lee, Interdisciplinary program in Agricultural and Forest Meteorology, Seoul National University, Seoul, Korea, Republic of (South), Ah Reum Han and Areum Han, Division of Basic Research, National Institute of Ecology, Seocheon-gun 33657, Korea, Republic of (South)

Background/Question/Methods
The frequency and severity of drought are expected to increase due to climate change; therefore, selection of tree species for afforestation should consider drought resistance of the species for maximum survival and conservation of natural habitats. In this study, three soil moisture regimes: control (100% precipitation), mild drought (40% reduction in precipitation), and severe drought (80% reduction in precipitation) were applied to six gymnosperm and five angiosperm species for two consecutive years. We quantified the drought resistance index based on the root collar diameter and to assess the association of other morphological, physiological, and biochemical traits to species drought resistance regression analysis was performed.
Results/Conclusions
The prolonged drought stress altered the morphological, physiological, and biochemical traits, but responses were species-specific. The species with high drought resistance had high leaf mass per area (LMA), photosynthetic rate (Pn), and midday leaf water potential (ΨMD) and low carbon isotopic discrimination (δ13C), flavonoid and polyphenol content, and superoxide dismutase and DPPH radical scavenging activity. The highly drought-resistant species had a relatively less decrease in leaf size, Pn, and predawn leaf water potential (ΨPD), and less increase in δ13C, abscisic acid, and sucrose content and LMA compared to the control. The interannual variation drought resistance (∆Rd) was positively correlated with the species hydroscopic slope (isohydric and anisohydric). Korean pine was highly drought resistant, sawtooth oak, hinoki cypress, East Asian white birch, East Asian ash, and mono maple were highly drought susceptible, and Korean red pine, Japanese larch, Sargent cherry, needle fir, and black pine showed a moderately drought resistance under consecutive drought experiments. These findings will help species selection for afforestation programs and establishment of sustainable forests, especially of drought-tolerant species under increased frequency and intensity of spring and summer droughts.