Effect of Lopping Intensities on Water Potential, Regrowth, 14 C-photosynthate Distribution and Biomass Production in Alnus glutinosa

A study on the effect of four lopping intensities (0, 30, 60 and 90 %) was made on three years old Alnus glutinosa (L.) Gaertn. It was observed that the reduction in leaf area led to a corresponding decline in transpiration rate after lopping. Consequently, there was an increase in water potential upto 48 days. The raised water potential enhanced water use efficiency particularly during first 30 days. Lopping at 30 and 60 percent intensities led to 62 and 57% more leaf area on the lopped plants than the unlopped ones. Regrowth in Alnus glutinosa was found to be related to a combination of higher net assimilation rate during first 30 days, recovery of larger leaf area, delayed leaf senescence and use of current and ischolar_main stored carbohydrates (particularly at 60 and 90% lopping intensities) for leaf growth. Unlike defoliation, a greater percentage of 14 C-photosynthate were translocated to the ischolar_mains than to the shoot of the lopped plants within 24 hours after commencement of lopping treatment but the established course of translocation of photosynthate identical to defoliation commenced at 50 days after lopping. At this stage, a greater percentage of 14 C-photosynthate was translocated for the growth of shoot and less to the ischolar_mains of the lopped plants, when a branch at bottom part of the main stem was fed 14 CO₂. The plants lopped at 30 percent intensity produced total biomass equivalent to the unlopped plants due to relatively quick resumption of total leaf area than those plants lopped at 60 and 90 percent intensities. Lopping treatments adversely affected dry matter accumulation in the nodules.