Drought alters the canopy architecture and micro-climate of Hevea brasiliensis trees

In this study a comparison of the canopy architecture and the growth and di stribution of roots was made in 10-year-old trees of Hevea brasiliensis gro wn in a severely drought-prone area on the west coast of India under rainfe d and irrigated conditions. LAI and light interception increased significan tly in the irrigated compared to the rainfed trees. Girth and height of the tree were 29 and 19% more while width and height of the canopy were 19 and 20% more in the irrigated than rainfed trees. There were 22% more primary branches which had 26% more diameter in the irrigated trees than rainfed tr ees. The branches were inserted on the main trunk at an angle of 58.36 degr ees in the irrigated and 44.22 degrees in rainfed trees. The above changes led to more light penetration which altered the light distribution inside t he rainfed trees during summer and inhibited leaf photosynthesis particular ly in the top canopy leaves. In the rainfed trees most of the growth occurr ed during the short favorable season immediately after the monsoon between June and October and no growth or even shrinking of the trunk was seen duri ng summer. In the irrigated trees a higher growth was seen throughout the y ear and summer had no adverse effect. Although there was some difference in the root distribution pattern, the total root density per unit soil volume did not vary between the irrigated and rainfed trees.