| 要旨トップ | 目次 | | 日本生態学会第73回全国大会 (2026年3月、京都) 講演要旨 ESJ73 Abstract

一般講演（口頭発表） H02-06 （Oral presentation）

#### 異なる環境条件における異なる機能群の葉群の最適炭素・窒素動態モデル【E】
Optimality models of carbon and nitrogen dynamics in leaf canopy of different plant functional types under different environmental conditions【E】

*城崎菜乃（東北大学）, 田代萌（東北大学）, 伊藤昭彦（東京大学）, 彦坂幸毅（東北大学）
*Nano SHIROSAKI（Tohoku Univ.）, Moe TASHIRO（Tohoku Univ.）, Akihiko ITO（Tokyo Univ.）, Kouki HIKOSAKA（Tohoku Univ.）

Understanding ecosystem material cycling is crucial for grasping and estimating ecosystems and the global climate. Terrestrial biosphere models (TBMs) simulate the cycling of carbon (C), nitrogen (N), and other materials within ecosystems. For improving TBMs, it is challenging to integrate C and N cycles in plants. In most existing TBMs, C and N cycles in plants are divided completely or combined by simple empirical equations. Meanwhile, in real plants, C and N cycling strongly couple with each other, which determines the physiological activities and structure of plant canopies in response to environmental variables. Under elevated CO2, previous experimental studies have shown that the photosynthetic rate increases, leaf N declines, and there are no significant changes in leaf area index (LAI). Additionally, it is known that higher N availability increases photosynthesis rate, LAI, and leaf N. However, existing TBMs without sufficient C-N coupling are sometimes unable to predict these plant environmental responses. Hikosaka (2003) proposed a model of C and N dynamics through leaf production and shedding in a plant canopy with optimization theory. This model can simulate plant responses more accurately, but it was too simplified to be incorporated into TBMs. Here, we extended this model by refining the representation of photosynthesis and then constructing new models of deciduous and evergreen trees with different leaf phenology. We verified each plant functional type model by simulating plant responses in LAI, canopy photosynthesis rate (Pc), leaf N, leaf life span (LLS), and nitrogen use efficiency (NUE) to elevated CO2 and N availability with changing input parameters. Responses in Pc, LAI, and leaf N to elevated CO2 and N availability were consistent with the results of previous experimental studies. Simulation results also demonstrated that responses to CO2 depend on leaf dry mass per area (LMA); higher LMA at elevated CO2 suppresses the decline in leaf N and the increase in LAI, suggesting that it is a key response to improve CO2 assimilation under elevated CO2. Furthermore, simulated responses in LLS and NUE differ between models. These results suggested that our models can simulate realistic plant responses and contribute to improving the estimation of plant responses in TBMs.

日本生態学会