14:15 〜 14:30
[ACG39-03] 30年目を迎える飛騨高山冷温帯落葉広葉樹林サイトにおける長期観測で検出された炭素収支の年々変動とトレンド
キーワード：森林生態系、炭素収支、長期観測
A long-term measurement of CO2 flux between the atmosphere and the forest ecosystem was initiated in September of 1993 at Takayama (TKY; 36°08’N, 137°25’E, 1420 m a.s.l.) in a cool-temperate deciduous forest in central Japan. For better understandings of the interannual variations (IAVs) and the trends of the annual carbon budget components and their environmental factors, we reanalyzed the long-term data mainly obtained from an eddy covariance (EC) measurement between 1999 and 2021. The main results obtained from the analyses are as follows:
(1) The IAVs in the annual net ecosystem production (NEP) and gross primary production (GPP) showed similar patterns with each other and much larger than that in the annual ecosystem respiration (Rec). The IAV in the annual NEP depended strongly on the annual GPP.
(2) The IAVs in the annual NEP and GPP showed significant positive correlations with those of the monthly mean NEP and GPP for each month from June to September. The IAVs in the monthly mean NEP and GPP from July to September were significantly positively correlated with those in the monthly mean solar radiation for the respective months.
(3) The IAV in the annual NEP was significantly negatively and positively correlated with those in the start (NGS) and the period (NGP) of the growing season showing positive values of NEP, respectively. Earl/late occurrence of the NGS were attributed to warm/cold spring, while long/short NGP was related to the warm/cold spring and the high/low monthly mean solar radiation in September.
(4) The IAVs in the annual NEP and GPP were significantly positively correlated with that in the leaf area index (LAI) in summer. The IAVs in monthly mean NEP and GPP were also significantly positively correlated with the monthly mean LAI for the respective months of June, August and September.
(5) Significant increasing and decreasing trends of the annual NEP and GPP were observed during the periods of 2004-2013 and 2013-2021, respectively. The former increasing trends were highly linked to recovery from the ecosystem disturbances due to typhoon strikes in 2004 and partly related to trends of some meteorological parameters. On the other hand, what factors caused the latter decreasing trends were not so clear. However, they were probably related to the decreasing trend of the monthly mean LAI in September and the advanced trend of the occurrence of the end (NGE) of the growing season for 2013-2018. They may also be influenced by recent extreme weather conditions such as high temperatures in August for 2018-2020 and the record high monthly precipitation and low monthly solar radiation in July 2020.
(6) Some intercorrelations between the events occurring in different seasons such as the occurrences of the NGS and the NGE and the occurrences of leaf expansion and leaf fall were found. It may be suggested that they are related not only to some biologically functions but also to interrelation of meteorological parameters associated with ENSO events.
These results derived from the long-term measurement are expected to provide us with very useful information for more accurate prediction of responses of the terrestrial ecosystems to climate change.
Acknowledgements
We thank staff of River Basin Research Center of Gifu University and National Institute of Advanced Industrial Science and Technology for their support to observation and data analyses. This study was partly supported by the JSPS KAKENHI (Grant Numbers JP18H03365, JP19H03301, JP19H01975 and JP22H00564) and the Global Environment Research Coordination System from the Ministry of the Environment, Japan (Grant Number MAFF2254).
(1) The IAVs in the annual net ecosystem production (NEP) and gross primary production (GPP) showed similar patterns with each other and much larger than that in the annual ecosystem respiration (Rec). The IAV in the annual NEP depended strongly on the annual GPP.
(2) The IAVs in the annual NEP and GPP showed significant positive correlations with those of the monthly mean NEP and GPP for each month from June to September. The IAVs in the monthly mean NEP and GPP from July to September were significantly positively correlated with those in the monthly mean solar radiation for the respective months.
(3) The IAV in the annual NEP was significantly negatively and positively correlated with those in the start (NGS) and the period (NGP) of the growing season showing positive values of NEP, respectively. Earl/late occurrence of the NGS were attributed to warm/cold spring, while long/short NGP was related to the warm/cold spring and the high/low monthly mean solar radiation in September.
(4) The IAVs in the annual NEP and GPP were significantly positively correlated with that in the leaf area index (LAI) in summer. The IAVs in monthly mean NEP and GPP were also significantly positively correlated with the monthly mean LAI for the respective months of June, August and September.
(5) Significant increasing and decreasing trends of the annual NEP and GPP were observed during the periods of 2004-2013 and 2013-2021, respectively. The former increasing trends were highly linked to recovery from the ecosystem disturbances due to typhoon strikes in 2004 and partly related to trends of some meteorological parameters. On the other hand, what factors caused the latter decreasing trends were not so clear. However, they were probably related to the decreasing trend of the monthly mean LAI in September and the advanced trend of the occurrence of the end (NGE) of the growing season for 2013-2018. They may also be influenced by recent extreme weather conditions such as high temperatures in August for 2018-2020 and the record high monthly precipitation and low monthly solar radiation in July 2020.
(6) Some intercorrelations between the events occurring in different seasons such as the occurrences of the NGS and the NGE and the occurrences of leaf expansion and leaf fall were found. It may be suggested that they are related not only to some biologically functions but also to interrelation of meteorological parameters associated with ENSO events.
These results derived from the long-term measurement are expected to provide us with very useful information for more accurate prediction of responses of the terrestrial ecosystems to climate change.
Acknowledgements
We thank staff of River Basin Research Center of Gifu University and National Institute of Advanced Industrial Science and Technology for their support to observation and data analyses. This study was partly supported by the JSPS KAKENHI (Grant Numbers JP18H03365, JP19H03301, JP19H01975 and JP22H00564) and the Global Environment Research Coordination System from the Ministry of the Environment, Japan (Grant Number MAFF2254).