北京林业大学学报2018，Vol.40Issue(1)：46-56,11.DOI:10.13332/j.1000-1522.20170202
生态系统尺度水汽通量分配——以寒温带兴安落叶松林为例
Partitioning of water vapor flux on the ecosystem scale: a case study on larch boreal forests
摘要
Abstract
[Objective] Evapotranspiration (ET) including evaporation (E) and transpiration (T), was the main way that ecosystem precipitation ( P) returned to the atmosphere. Under the background of climate change, understanding the characteristics and distribution of ET in a cold-temperate Larix gmelinii natural forest at permafrost region of northern part of Daxing'an Mountains, northeastern China could help to further comprehend the response modes of the boreal forest ecosystem to the climate change. [Method]Model simulation and field experiments were applied for estimating and measuring ecosystem scale evaporation (E), transpiration ( T), and evapotranspiration ( ET) in a boreal larch forest. E includes forest floor evaporation (Ef ) and canopy interception (Ec ) which only occurred during rainfall events. Total forest transpiration ( Ttot ) in this study is the sum of dominant tree transpiration ( Td ), intermediate tree transpiration (Ti ) and suppressed tree transpiration (Ts ). Furthermore, we analyzed the variations and allocation proportions of ET and components under conditions of non-rainy or rainy. Then we discussed the responses of Ef , Ttot and ET to the net radiation ( Rn ) and the vapor pressure deficit ( VPD) under different water input conditions. [ Result] Diurnal variations of ET and its components all performed as single peak patterns in both non-rainy and rainy days, and peak value in each curve at non-rainy day grouping was higher than in rainy day grouping. Ef , Td , Ti , Ts and ET in non-rainy days were 10. 3, 25. 6, 15. 2, 10. 8 and 66. 3 mm, respectively. Meanwhile, Ef , Ec , Td , Ti , Ts and ET in rainy days were 2. 2, 24. 3, 11. 2, 5. 1, 3. 8 and 47. 8 mm, respectively. In non-rainy days, Ef / ET was 15. 5％ , and Ttot / ET was 78. 0％ , while Td / ET, Ti / ET and Ts / ET contributed 38. 7％ , 23. 0％ and 16. 4％ , respectively. In rainy days, Ef / ET could go low to 4. 6％ , Ec / ET reached 50. 9％ , and Ttot / ET decreased to 42. 2％ , in which Td / ET, Ti / ET and Ts / ET were 23. 5％ , 10. 6％ and 8. 0％ , respectively. These results represented that ET was dominated by T (specifically for Td ) in non-rainy days. However, E (specifically for Ec ) contributed the highest proportion of ET in rainy days. 94. 7％ of P returned to the atmosphere through ET during whole observation days, there into, T and E accounted for nearly 57％ and 38％ , respectively. Overall, without regard to rainfall events, ET had better correlation with net radiation at 23 m height (Rn ) than with VPD and Ttot owned similar correlations with both Rn and VPD, but Ef expressed opposite result with ET. This result demonstrated that Rn was obviously the main driver for ecosystem's energy cycle and material exchange,Ttot restrained by Rn and VPD at the same time, and Ef was more susceptible to VPD compared to Rn . [Conclusion] The transpiration capacity of dominant trees of Larix gemelinii species was stronger than intermediate and suppressed trees. So that, forest transpiration upscale from the individual tree could be overestimated if this method only considers in situ measured Td (even including Ti with larger DBH) and ignores Ts . The actual error depends on the degree of forest differentiation and moisture income conditions. The meteorological condition of non-rainfall days is more propitious to the water-vapor exchange at vegetation-atmosphere interface, and the occurrence of rainfall will affect the distribution pattern of ecosystem ET.关键词
北方森林/蒸发/林冠截留/蒸腾/蒸散发Key words
boreal forest/evaporation/canopy interception/transpiration/evapotranspiration分类
农业科技引用本文复制引用
刘家霖,满秀玲..生态系统尺度水汽通量分配——以寒温带兴安落叶松林为例[J].北京林业大学学报,2018,40(1):46-56,11.基金项目
国家自然科学基金项目(31770488),中央高校基本科研业务费专项(2572016AA07). （31770488）
