Estimation of CO2 assimilation and emission flux of vegetation in subtropical island - Taiwan

Abstract

The goal of the present study is to provide a comprehensive model to estimate CO2 assimilation and emission flux in Taiwan. In addition to metrological data, the model consists of (1) 83 land-use types including 68 vegetations, (2) NDVI-LAI transfer functions for various vegetations, (3) leaf width database for 68 vegetations, and (4) LEAFC3 module. The model output includes 2D hourly CO2 assimilation flux for 68 vegetations with 1 km × 1 km resolution in Taiwan. The results of model evaluation with observed data of 26-day (Nov 12–Dec 7, 2009) CO2 flux field experiment include: (1) predicted hourly CO2 uptake fluxes on the daytime match rather well with observed data variations but CO2 release fluxes on the nighttime show significant underestimate; (2) predicted CO2 uptake and release fluxes show a relatively good correlation with observed data (R2 = 0.67); (3) predicted CO2 assimilation fluxes and isoprene emission fluxes are highly correlated with trends of variation due to photosynthesis. Based on the meteorological data in 2009, the annual total amount of CO2 assimilation about 115.3 million ton in Taiwan with 79.6 million ton for forests and 35.7 million ton for non-forest vegetations. The CO2 assimilation amount is higher in the third quarter (July–September) and lower in the first quarter (January–March) for 44.3% and 16.4% of the annual total amount respectively. The spatial distribution of annual CO2 assimilation amounts are higher in lower and medium altitude mountain areas with an average of around 6–10 thousand ton km−2 y−1. The implication of the other results is also discussed.