Assessment of biomass and carbon storage of a Populus simonii windbreak located in the Western Cape Province, South Africa

Abstract

The integration of trees within agricultural systems delivers the opportunity to provide multiple benefits over those afforded by agriculture without trees. The use of windbreaks as a form of agroforestry, in water scarce environments, is primarily used to reduce windspeeds in order to decrease evapotranspiration. Quick growing poplar species such as Populus simonii ((Carrière) Wesm.) are frequently utilised within windbreak structures, but to date, few allometric equations are available to quantify biomass production and to make inferences about carbon storage potential of this species, and none outside the forest. To fill this knowledge gap, we destructively sampled 17 P. simonii growing within a windbreak on a wine estate in the Western Cape Provence, South Africa. Power functions were constructed to explain tree height, whole tree aboveground woody biomass, stem and branch biomass as a function of stem diameter at 1.3 m. Additional functions were developed to predict individual branch length and biomass based on branch stub diameter. The presented models explained each variable with high significance. The models could be used to estimate carbon stock per km of windbreak for the given example. Furthermore, bark percentage predicted by stem sectional diameter was modelled to provide a function that can separate wood and bark fractions as a further outlook for the species’ utilisation.