JOURNAL OF NATURAL RESOURCES ›› 2011, Vol. 26 ›› Issue (4): 619-634.doi: 10.11849/zrzyxb.2011.04.008

• Resources Ecology • Previous Articles     Next Articles

Modeled Effects of Changes in the Amount and Diffuse Fraction of PAR on Forest GPP

HE Xue-zhao1,2,3, ZHOU Tao1,2, JIA Gen-suo4, ZHANG Zi-yin1,2, LI Xiu-juan1,2, ZHAO Chao1,2, FENG Sheng-hui1,2   

  1. 1. State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, China;
    2. Academy of Disaster Reduction and Emergency Management, Ministry of Civil Affairs & Ministry of Education, Beijing 100875, China;
    3. School of Geodesy & Geomatics Engineering, Huaihai Institute of Technology, Lianyungang 222005, China;
    4. Institute of Atmospheric Physics, CAS, Beijing 100029, China
  • Received:2010-08-10 Revised:2010-12-10 Online:2011-04-29 Published:2011-04-29

Abstract: The scattering and absorption of solar radiation by anthropogenic aerosols reduce the amount of photosynthetically active radiation (PAR) reaching the earth's surface and increase the fraction of PAR that is diffuse (FDIFF), with the counteracting effects on plants photosynthesis which determines terrestrial ecosystem's gross primary production (GPP). For the complex interactions among the total PAR amount, FDIFF, temperature and humidity, it's difficult to derive the quantitative relationship between FDIFF and GPP from present field and experimental measurements, leading to substantial uncertainty and dispute about the projection of the production and carbon assimilation of terrestrial biosphere influenced by emissions of anthropogenic aerosols. Using a process-based canopy photosynthesis model (MAESTRA), we explored respective and combined effects of changes in PAR amount and the FDIFF on GPP in three typical forests among the North-South Transect of Eastern China (NSTEC). The results showed that the responses of GPP to PAR amount changes were consistently positive in all three sites, while the magnitudes of GPP change were determined not only by the degrees of PAR amount change but also the sensitivity of GPP to these changes, which was generally depressed to nearly naught by higher PAR amount and/or lower temperature from about 0.6 g C mol-1 when incident PAR was lower and temperature was not limited. The increase of FDIFF stimulated absorption and use efficiencies of incident PAR in the three forests, as a result of the difference, which was depressed by lower temperature and/or fewer leaf area, between the efficiencies of direct and diffuse PAR, leading to the magnitudes of GPP change responding to FDIFF changes were also influenced by the temperature and leaf area as well as the degree of FDIFF changes and the total PAR amount. Investigating the relations between the changes of diffuse PAR and total amount was necessary in quantifying the combined effects of these changes on GPP, which were generally the consequence of the counteraction of respective effects of the changes. In our results, the counteraction was usually significant under conditions with greater PAR amount, but the direction of GPP changes was still mainly controlled by the changes of PAR amount. The year-around offset was about 1/3 - 1/2 of the degree of the effect of total amount changes.

Key words: carbon cycle, GPP, ecosystem modeling, PAR, fraction of diffuse radiation, forest ecosystem, MAESTRA

CLC Number: 

  • S718.5