Seasonal And Interannual Variability Of Light Use Efficiency Of Typical Temperate And Subtropical Forests In China

Light use efficiency(LUE) refers to an important indicator of the different ecosystems to use solar energy synthetic biochemical energy, is also an important parameter of sensing inversion model. Reveal dynamic characteristics of LUE of ecosystems, clarify variability of LUE between different ecosystems, investigate the spatial and temporal dynamics of biological and environmental control mechanisms for understanding ecosystem photosynthesis carbon cycle and improved regional productivity estimation model is important. This study utilization 2003- 2011 years, long-term, continuous observational data from Chinese terrestrial ecosystem flux observation and research network(ChinaFLUX), compared and analyses LUE seasonal variability, and reveals its response mechanism to environmental factors changing of the Changbai Mountain temperate Coniferous mixed forest(CBM) and Dinghu Mountain subtropical evergreen broadleaf forest( DHM) two kinds of zonal forests.The main findings are as follows:1. CBM’s LUE mainly controlled by temperature conditions, monthly LUE changes with the temperature showed significant seasonal variations in a single peak, LUE begins to grow rapidly from the end of March to the end of June, the maximum of LUE is in July. Monthly LUE begins to decrease rapidly by the end of July to October. Compared with CBM, monthly LUE seasonal variation of DHM is not obvious relatively, from January to March showed increases, decreases in March to June. July to the end of LUE showed significant differences. In contrast, since annual hydrothermal conditions of DHM are suitable for the growth of vegetation, LUE seasonal dynamics characteristics are not obvious.2. In the period 2003- 2011, the interlineal maximum light use efficiency of CBM changes yearly growth trend, but in 2006 and 2009 LUEmax relatively low, mainly by less rainfall in 2006 and 2009. DHM’s LUEmax showed a steady growth during 2003- 2007, followed by the reduction, steady growth during 2009- 2011, interracial variability of LUEmax of DHM and soil moisture and precipitation trends a negative correlation.3. Seasonal changes in daily LUE of CBM showed a variability in a single peak, while the air temperature and EVI showed a significant positive correlation. DHM showed EVI and VPD in a range of negative correlation with soil moisture and display a positive correlation.4. CBM’s LUEmean and LUEmax are higher than DHM’s, this result is consistent with the results that LUE of broad-leaved forest is lower than coniferous forests.