11:15 AM - 11:30 AM
[ACG40-03] Inter-annual variations and long-term trends in the carbon budget and the atmospheric CO2 concentration in a cool-temperate deciduous forest at Takayama
Keywords:forest ecosystem, inter-annual variation, long-term trend, carbon budgets, atmospheric CO2 concentration
We have made long-term systematic measurements of the CO2 flux between the atmosphere and forest ecosystem, the atmospheric CO2 concentration, and meteorological parameters in a 60-year-old cool-temperate deciduous forest at Takayama (TKY; 36o08’N, 137o25’E, 1420 m a.s.l.), Japan since 1993. Using these data, we have examined their inter-annual variations, long-term trends and environmental factors governing these variations. The results obtained from the analyses are as follows:
(1) Annual net ecosystem production (NEP) and the gross primary production (GPP) vary significantly from year by year, while inter-annual variation in the annual ecosystem respiration (ER) is relatively small. The inter-annual variation in the annual NEP depends strongly on the annual GPP.
(2) Annual NEP shows a statistically significant positive correlation with the monthly NEP in June and July. Higher insolation during the summertime tends to produce higher amount of the annual NEP.
(3) In the warm-spring years, budding, beginning of the daily positive NEP and the spring downward zero crossing of atmospheric CO2 concentration tend to occur early.
(4) These inter-annual variations may be influenced by those of meteorological conditions associated with the ENSO event.
(5) Significant long-term trends in the increased annual NEP, GPP and ER, the enhanced seasonal amplitude of atmospheric CO2 above the canopy during the daytime and the delayed occurrences in the leaf-fall are found.