Allometric relationships of different tree species and stand above ground biomass in the Gomera laurel forest (Canary Islands)

Abstract

Estimation of net above ground primary productivity in forest ecosystems by non-destructive means requires the development of allometric equations, to allow prediction of above ground biomass from readily measurable variables such as diameter-at-breast-height (DBH). Equations of this type have not been well developed for trees of the Macaronesian laurel forest. In the present study, we characterized trees of five species ( Erica arborea, Ilex canariensis, Laurus azorica, Myrica faya and Persea indica) in four types of laurel forest in the Garajonay National Park on Gomera Island in the Canary Islands, with the aim of developing appropriate allometric equations. Among forests, within each species, the slope and elevation ( y -axis intersect) of the equations obtained did not vary significantly, so that we were able to pool the data and obtain a single equation for each species. However, considering each species separately, there was significant variation among the slopes and elevations of the equations obtained for each. The difference between DBH-biomass relationships among these species can be attributed to differences in (a) the distribution of biomass among trunk-plus-primary-branches, secondary branches and leaves, and (b) woody tissue density. We applied the new allometric equations to six different forest types in the Garajonay National Park. Above ground biomass ranged from 65,631 to 352,683 kg d.w. ha −1. Comparison of these results with those obtained using a previously published allometric model revealed differences of more than 100% for some forests. When we applied the new allometric equations to data from other forests on the island of Tenerife we obtained differences of more than 20% in above ground biomass which ranged from 159,469 to 310,580 kg d.w. ha −1. We believe that all previous data corresponding to above ground biomass in Macaronesian laurel forest may contain errors, and propose the new equations to be used in the future, and that other one have to become developed for the remaining species.