To confirm the results, the variations of the 
maximum surface temperature minus the maximum 
air temperature for the measurement periods are 
calculated and shown in Fig. 9. The same results 
were indicated in Fig. 9. 
In the latter growth stage of an erectophile crop, 
the canopy temperature includes the low leaf 
temperature of the under part within the canopy. 
However, leaves of the planophile crop receive 
much energy and the canopy temperature becomes 
high. 
4 , Conclusions 
The results of this study are summarized as 
follows: 
1) Canopy surface temperatures of the planophile 
crop (soybean) as measured by IR thermometer 
are affected by the leaf temperatures of leaves in 
the upper portion, because most of such canopy 
leaf area is near the upper portion of the canopy. 
2) In contrast, canopy temperatures for the 
erectophile crop (corn) are affected by the leaf 
temperature from the upper to the lower portion of 
the canopy. 
3) Therefore, in latter stages of growth (dense 
vegetation cover), the maximum canopy temperature 
of the erectophile crop (corn) is lower than that of 
the planophile crop (soybean). 
4) Also, the directional variation and hourly 
variation of leaf surface temperature are larger for 
the planophile crop (soybean) than for the 
erectophile crop (corn), because wind and solar 
radiation more influence the planophile crop. 
5) At low intensities of solar radiation, however, 
surface temperatures of leaves facing skyward are 
lower for soybeans than for corn. 
These results suggest that canopy temperatures 
vary due to canopy structure: especially orientation 
and distribution of leaves within canopies, and crop 
spaces. Therefore, in the latter growth stage of 
crops, vegetation cover ratio is not an important 
factor for canopy temperature. In the latter growth 
stage (dense vegetation cover), the canopy 
temperature of the erectophile crop is lower than 
that of the planophile crop in daytime. 
This is important for analyzing thermal 
phenomena using canopy temperature measured by 
IR thermometer. 
762 
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International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B7. Vienna 1996