Vegetative characteristics and biomass production of two hybrid Poplar clones in relation to the environmental conditions in the Velino river hydrographic basin (central Italy)

Short rotation plantations of fast-growing tree species like poplar, willow, false acacia and eucalyptus need intensive cultivation practices to force biomass production. In the present study, the adaptability degree of two hybrid poplar clones (‘Monviso’, ‘AF8’) and their biomass production were evaluated in the particular context of the Rieti uplands (Italy) with low-impact farming systems. The hybrid poplar clones were planted at the end of 2010, according to the biennial shift harvesting system. The plant heights increased during Spring, with further large increases during June, which were not seen for July. Over this period, temperature represented the principal forcing variable for plant development, as the water-table depth was not yet a limiting factor for poplar vegetative development. From the last part of August, the plants showed new large average vegetative increases, which reached a second maximum in the first half of September. Here, strong correlation between vegetative increase and rain volumes was seen. The analysis of the biomass production and the base diameter of the main shoots showed low variability across these two clones. The ‘Monviso’ clone showed higher biomass production, above all during the third year, when the diameter at the base was also larger in comparison with the ‘AF8’ clone. In this study, the mean annual poplar dry biomass production during the second biennial shift (2014-2015) was greater than that of the first (2012-2013), with this increase also occurring without fertilisation and irrigation practices in the second year of cultivation.