Frequency and severity of drought is expected to increase in the era of climate change, therefore the drought tolerance of tree species should be considered before plantation for their survival in the field. Morphological and physiological characteristics of two of the most popular plantation tree species in Korea, Sargent cherry (Prunus sargentii) and Japanese larch (Larix kaempferi), were examined for their drought tolerance. Three different irrigation regimes; control (CT; 100% precipitation (P)), light drought (LD; 40% reduction of P), and heavy drought (HD; 80% reduction of P) were applied at the experimental site at Mt. Giri, Republic of Korea.
Results/Conclusions
For morphological responses, both species significantly decreased their leaf sizes in drought conditions, however, Sargent cherry and Japanese larch reduced leaf width and length, respectively. On the other hand, leaf mass area (LMA, g m-2) increased (maximum P = 0.003), but branch growth decreased in both species under drought conditions (maximum P = 0.012). However, stem diameter and plant height was not affected in both species under drought (minimum P = 0.058 and 0.249, respectively). For physiological responses, drought stress significantly decreased maximum photosynthesis rate (Amax), electron transfer rate (Jmax) and stomatal conductance (Gs) at Amax for both species (maximum P = 0.011, 0.017 and 0.014, respectively), but maximum carboxylation rate (Vcmax) was not different among treatments (minimum P = 0.062). Drought reduced predawn leaf water potentials (ΨPD) and midday leaf water potential (ΨMD) in Sargent cherry (P = 0.020 and 0.009, respectively), but not in Japanese larch (P = 0.057 and 0.591, respectively). Similarly, reduction of transpiration was also significant in Sargent cherry (P = 0.001), but it was not different in Japanese larch (P = 0.078). The seasonal water-use-efficiency (WUE) was evaluated with the carbon isotopic discrimination (δ13C). In mid-summer, Sargent cherry increase the WUE under drought conditions (P = 0.035), but not in Japanese larch (P = 0.187). However, δ13C in both species was not significantly affected in early summer (minimum P = 0.211) and late summer (minimum P = 0.256). In the present study, Japanese larch showed more water conserving and showed greater resilient of morphological and other physiological traits (i.e. photosynthesis) as compared to Sargent cherry under drought stress. Therefore, Japanese larch will be more appropriate species than Sargent cherry for more frequent drought stress conditions.