Interannual Variation and Trend of Carbon Budget Observed Over a 28-year Period at Takayama in a Cool-Temperate Deciduous Forest in Central Japan

Abstract

Long-term carbon dioxide (CO) flux measurements between the atmosphere and the ecosystem have been made since 1993 at a cool-temperate deciduous forest site (Takayama) in Japan influenced by Asian Monsoon, constituting the longest dataset among all the AsiaFlux sites. Interannual variations (IAVs) and trends of the annual carbon budget components and their environmental factors were examined. Annual net ecosystem production (NEP) (mean ± 1σ) during the period of eddy covariance measurement in 1999-2021 was 265 ± 86 gC m yr, and its IAV was dependent more on gross primary production (GPP) than on ecosystem respiration. IAVs in annual NEP and GPP were correlated with the IAVs of the monthly mean NEP, GPP and leaf area index (LAI) from June to September, as well as with that of the length of the net carbon uptake period. Significant increasing and decreasing trends in the annual NEP and GPP were detected during 2004-2013 and 2013-2021, respectively; the increasing trends were mainly caused by the vegetation recovery from typhoon disturbances while the decreasing trends were partly influenced by recent extreme weather events. Significant positive correlations of the IAVs between the start and the end of the net carbon uptake period, and between the leaf expansion and leaf fall were found. These may be attributed to biological functions and interseasonal relationship of meteorological parameters associated with ENSO events that can also influence IAVs in annual NEP and GPP.

Interannual Variation and Trend of Carbon Budget Observed for More Than Two Decades at Takayama in a Cool‐Temperate Deciduous Forest in Central Japan

“…The data set of the carbon budget at TKY presented in this study (Murayama et al, 2023) is available at https://doi. org/10.5281/zenodo.8300684.…”

“…The data set of the carbon budget at TKY presented in this study (Murayama et al, 2023) is available at https://doi.org/10.5281/zenodo.8300684. The flux and meteorological data at TKY used in the study (Murayama et al, 2024) are now available at the AsiaFlux Database via https://db.cger.nies.go.jp/asiafluxdb/?page_id=13 after registration.…”