Abstract
The diurnal changes of solar radiation, air temperature and fruit temperature, and integrated solar radiation in all day were investigated at different locations on the trees of open center and hedgerow of satsuma mandarins (Citrus unshiu Marc. var Sugiyana) from late-July to mid-December, 1977.
The results are given as follows.
In the open center form, integrated circumglobal radiation (ICR) was the highest at the top in the south side of the tree and slightly lower in the other sides, but ICR of the hedgerow was lower even at the top of the canopy, when compared with the open center form. ICR at the skirt of a canopy was considerably low in both forms. ICR at the skirt in the north side of both trees was about 45% and 2% of that at the top of the south side in summer and in autumn, respectively. ICR at the interior of canopy was low in both forms, especially in the hedgerow, it was about 10-20% of the integrated value at the top of the south side.
Ambient air temperature of the open center form rised more rapidly at the south side, the top and the skirt of the east side, and the interior than at the top and the skirt of the west and the north sides in the morning. The air temperature at the top of the west side on the canopy rised slowly until 14:00, then reached the maximum at about 16:00, thereafter fell gradually, but remained higher than that at the other locations. At the top of the north side, air temperature rised slowly from sunrise until 16:00, and then until sunset, thereafter gradually fell, keeping higher than that at the top and the skirt of the east side. At the interior, air temperature rised more rapidly than that at the top and the skirt of the west and the north sides in the morning, then kept constant from 12:00 to 16:00, and was higher than that at the top and the skirt of the east side after 16:00. Ambient air temperature of the hedgerow rised remarkably at the top and the skirt of the east side of the canopy in the morning, and that at the top and the skirt of the west side rised more slowly. Around noon, temperature on the west side was higher than that on the east side and fell down gradually keeping higher than the other locations. This was considered to be due to the westering sun. However, the air temperature at the top and the skirt of the east side fell rapidly after 14:00 and was the lowest of all locations at sunset. Air temperature at the interior canopy showed intermediate changes in the all locations all day.
Fruit temperature rised more rapidly at the top and the skirt of the east side of the open center form than that at the other locations in the morning. After noon, fruit temperature at the top and the skirt of the west side was higher than that at the other sides. Fruit temperature at the south side was lower than that at the east side in the morning and was lower than that at the west side in the afternoon. At the top of the north side, fruit temperature was the lowest of all locations from sunrise to 15:00 and thereafter was higher than that at the south side. At the skirt of the north side and the interior of canopy, fruit temperature rised slowly and remained lower than that at the other locations all day. Fruit temperature rised more rapidly at the top and the skirt of the east side and the top of the west side of the hedgerow than at the other locations in the morning. At the skirt of the west side and the interior of canopy, fruit temperature rised more slowly than that at the other locations from sunrise to 15:00 and remained lower than that at the other locations all day. After 16:00, fruit temperature at the interior fell rapidly and that at the skirt of the west side fell gradually.
