Phenological Observation of Japanese Larch on a Mountainous Landscape in Central Japan, and Application to Carbon Budget Simulation by Using a Process-based Terrestrial Ecosystem Model

Carbon budget of terrestrial ecosystems is one of the most important factor to simulate future climate, because forests serve as a major sink of atmospheric CO₂. Especially, deciduous forests can be susceptible to climate change, because the phenology of leaves and photosynthesis are largely influenced by temperature. On the other hand, the management of artificial forests can function as the mitigation and adaptation strategies for climate change. In this study, we observed leaf phenology of Japanese larch, which is the only deciduous tree in artificial forests in Japan, and estimated the timings of leaf flush and leaf shedding based on the seasonal variation of plant area index in central Japan from fall of 2018 to summer of 2019. Then, we evaluated relationships of these timings and effective cumulative temperature (ECT), and compared with the results of previous study based on satellite observation in order to improve the carbon budget simulation by a process-based terrestrial ecosystem model. As a result, we found that the relationship between a timing of leaf flush and ECT based on our in-situ observation was similar with that based on satellite observation. But, a timing of leaf shedding based on our in-situ observation was about two weeks later than the timing based on satellite observation, so that, the lower ECT was required to leaf shedding in our in-situ observation. When we incorporated the relationship between the timing of leaf shedding and ECT into a process-based terrestrial ecosystem model, the model reproduced carbon budget in autumn better than the simulation incorporated the relationship of leaf phenology and ECT based on satellite observation.

Acknowledgement

This research was supported by the Environmental Research and Technology Development Fund (2RF-1803) of the Environmental Restoration and Conservation Agency of Japan.