80 



P. C. Miller et al. 



SOLAR 



Direct Diffuse Reflected 



INFRARED 



Down Up 



23.9 



-3.9 



-28.5 



0.8 



27.8 



11.7 



7.9 



-29.3 



3.8 



Soil 



Rr 



Canopy 



11.7 



CONVECTION 



8.9 



7.9 



777777777777 



Soil 



777777777777777777777 



EVAPORATION CONDUCTION 



2.8 



4.6 ' 2.5 



3.8 



0.8 



1.8 



2.0 



ninnnnnninnnni/i/nnnninnnj 



0.04 



FIGURE 3-7. Partitioning of incoming solar and infrared irradiance (MJ 

 m'^ day'^) by the canopy and soil in the meadow vegetation type. Con- 

 vectional loss is divided into that lost from standing dead material (4.6 

 MJ m~^ day') and that lost from green leaves (2.5 MJ m'^ day'). (After 

 Stoner et al. 1978b.) 



with relative humidities of 90 to 100% within the canopy. The high 

 relative humidity was caused by the high rates of evaporation from the 

 moss, and by the convectional loss of radiation that was intercepted by 

 standing dead material. At the moss surface 30 to 50% of the absorbed 

 radiation was lost by convection and 50 to 70% by evaporation. Conduc- 

 tion accounted for less than 1% of the incoming solar radiation. Of the 

 total water lost by evapotranspiration from the wet meadow 14 to 20% 

 was lost by transpiration from the vascular plants. The remainder was 

 lost by evapotranspiration from the moss understory (Miller et al. 1976, 

 Ng and Miller 1977, Stoner et al. 1978b). This partitioning of water loss 

 was confirmed in field studies with tritiated water (Koranda et al. 1978). 

 During the growing season the fraction of incoming radiation inter- 

 cepted by the Carex-Oncophorus meadow canopy increased as the foli- 

 age area index increased, while the intercepted radiation per unit of foli- 



