【Seminar】"Ecophysiological strategies of plants inhabiting harsh environments: leaf trichomes in Hawaii and root distributions in Alaska." by Dr. Gaku Amada

Zoom URL: https://oist.zoom.us/j/95087842461?pwd=EnfrFUJLJMwAYS5rwFYXElzjTz6yWQ.1
Meeting ID: 950 8784 2461
Passcode: 242456

Abstract
Harsh environments (e.g., drylands, alpine regions, and permafrost conditions) provide ideal systems for understanding evolutionary processes and their influence on ecosystem dynamics because of their relatively low species diversity and strong environment constraints. In this seminar, I present two topics: (1) the adaptive roles of leaf trichomes (hairs) in an evolutionary diverse tree species in Hawaii, and (2) belowground niche partitioning of plants under permafrost conditions in Alaska. In the first topic, we examined the multifunctionality of leaf trichomes in Metrosideros polymorpha, a dominant species that exhibits the remarkable intraspecific variation in leaf trichomes across diverse environments. We identified three major functions—diffusion resistance, enhancement of foliar water uptake, and defense against specialist gall makers—whose relative importance varied along environmental gradients. These results suggest that multiple functions must be considered to explain the observed trichome variation, and that the concept of multifunctionality is key to understanding both the diversity and ecological significance of leaf trichomes. In the second topic, we investigated the mechanism maintaining plant biodiversity under harsh permafrost conditions. We have tested the hypothesis that plants with different growth forms utilize soil nutrients at different depths within the active layer. In shallow soil layers, ectomycorrhizal trees and ericoid shrubs predominantly distribute their roots. In contrast, non-mycorrhizal herbaceous plants extend their roots deeper, near permafrost table, where they may access inorganic nitrogen unavailable to trees and shrubs. Such vertical niche partitioning may contribute to the coexistence of diverse growth forms in permafrost environments.

Short bio
Gaku Amada received his academic training in plant ecophysiology and forest ecology and earned a Ph.D. in Agriculture from Kyoto University, Japan, in 2021. His doctoral research focused on the adaptive roles of leaf trichomes in diverse Hawaiian tree species. Following his Ph.D., he worked as a postdoctoral researcher at the Japan Agency for Marine-Earth Science and Technology (JAMSTEC)(2021-2024), where he conducted a soil warming experiment to investigate the effects of permafrost degradation on biogeochemical cycling in interior Alaska. Since 2024, he has been a JSPS Research Fellow PD at the Forestry and Forest Products Research Institute, mechanisms of maintaining plant biodiversity in permafrost environments. His research centers on the adaptive strategies of plant species in harsh environments, particularly the adaptive significance of leaf functional traits (e.g., trichomes).