| 英文摘要： |
The timescale dependence of environmental factors' influence on net ecosystem productivity (NEP), evapotranspiration (ET), and the effect of high and cool air temperature (Ta) across multiple timescales need to be quantified to identify the response mechanisms of forest ecosystems. We analyzed NEP and ET over 11 years in a subtropical coniferous plantation, and wavelet analysis was used to determine spectrum characteristics of these fluxes and quantify the time lag between these fluxes and environmental factors from daily to annual timescales. The NEP and ET had significant daily and annual spectrum variabilities, but ET exhibited a broader significant spectrum than NEP from days to months timescales. At daily and annual timescales, NEP was significantly synchronized with, and preceded photosynthetically active radiation (PAR) and Ta by 1. 12 +/- 0.6 h and 23.16 +/- 17 days, respectively. Meanwhile, ET was significantly synchronized with net radiation (Rn) at both daily and annual timescales, lagging Rn by 1.15 +/- 1.4 h, but preceding it by 5.73 +/- 4.39 days, respectively. From days to months timescales, with no continuous significant effect, NEP preceded PAR and vapor pressure deficit (VPD), and lagged soil water content (SW); however, ET only preceded Rn and VPD. In addition, summer high-Ta enhanced the effect of SW on NEP and ET across multiple timescales. Early spring cool-Ta shortened the time lag between PAR and NEP at daily and annual timescales, but only shortened it between Ta and ET at a daily timescale. This study demonstrated the more modulating effect of SW on the dominant influence of solar energy on NEP than ET, with timescale increased. This study also indicated that NEP and ET were more sensitive to high-than cool-Ta, and the time lag effects of these Ta events should be considered separately to adequately acknowledge the response mechanisms of these fluxes. |
在线留言
联系我们
所长信箱