Assessment of carbon balance in intensive and extensive tree cultivation systems for oak, olive, poplar and walnut plantation

To reduce GreenHouse Gas (GHG) emissions, the Kyoto Protocol identifies a number of activities that are closely related to land use, included in the category called Agriculture, Forestry and Land Uses (AFOLU). While forests and agricultural systems result in CO2 absorptions (live biomass, dead biomass and soil), every process undertaken for their management requires energy and resources, which can lead to a significant reduction of the environmental benefits. The study analyzes three tree plantations managed at different cultivation intensities in Italy, from an extensively managed plantation (a pure oak plantation) and a semi-intensively managed plantation (walnut and poplar plantation with nurse plants), to an intensively managed olive grove. Permanent and non-permanent biomass were accounted for in order to get the carbon stock of every plantation, estimated at the same age of 14 years old. The numerous processes operated for management of different cultivated species, e.g. planting, soil management, fertilization, phytosanitary treatments, pruning, harvesting, etc. were monitored and their impacts were quantified by applying the methodology known as Life Cycle Assessment (LCA). Removals (carbon sequestrations) were compared to emissions on a time scale, in order to assess the net CO2-eq balance. Impacting treatments and processes were identified and further analysis on the individual phases and materials were conducted. Olive trees showed an unexpected capacity to store CO2-eq, but this ability was evident only if annually harvested fruits and prunings were considered in the calculation. The plantation that demonstrated its ability to store most CO2-eq at the age of 14 was the semi-intensively managed plantation, showing a higher efficiency in the energy spent by man. The paper offers a contribution for an innovative environmental performance evaluation of different tree cultivation management systems, including the assessment of potential benefits in terms of sequestered CO2-eq for the studied tree plantations and possible avoided emissions thanks to sustainable agricultural practices.