GROWTH, LEAF GAS EXCHANGE AND PRODUCTION OF BIOMASS IN COPPICED AND POLLARDED AGROFORESTRY TREE SPECIES

摘要

Four coppicing or pollarding treatments (stems cut at heights of 0.5, 1.0, 1 .5 and 2.0 m) were applied to four tree species, aged five years old, in an agroforestry plantation We measured growth, leaf gas exchange characteristics and foliage and branchwood biomass in four important fuel and fodder agroforestry tree species, namely, Grewia optiva, Celtis australis, Bauhinia variegata and Morus alba. Out of the four species, B. variegata transpired the most followed by M. alba, then C. australis and G, optiva. For G. optiva and M, alba, transpiration was higher from plants pollarded at 1.5 or 2.0 m compared with plants pollarded at 1.0 m or coppiced at 0.5 m. Photosynthetic rate was highest in M. alba and lowest in C. australis. In M. alba and G. optiva, higher rates of photosynthesis were observed in trees pollarded at 1.5 and 2.0 m. Water-use efficiency was higher in M. alba and G. optiva than in B. variegata and C. australis. Maximum leaf size was observed in B. variegata, followed by M. alba andG. optiva. Cutting height did not affect leaf size significantly. For M. alba and G. optiva, LAI was highest at cutting heights of 1.5 and 2.0 m. Coppicing and pollarding significantly affected the production of foliage and branchwood biomass. Fodder and fuelwood production from agroforestry plantations would be maximised by planting M. alba or G. optiva and pollarding annually at a height of 2.0 m.