Large Scale Shrub Biomass Estimates for Multiple Purposes

With the increase of forest fires in Portugal in recent decades, a significant part of woodlands is being converted into shrubland areas. Background: From an ecological point of view, woodlands and shrublands play an essential role, as they not only prevent soil erosion and desertification, but also contribute to soil protection, habitat preservation and restoration, and also increased biodiversity for carbon sequestration. Concerning the shrublands, the assessment of their biomass is essential for evaluating the fuel load and forest fire behavior and also beneficial for obtaining estimates of carbon and biomass for energy use. Methods: In this study, we collected data about the potential shrub biomass accumulation along fifteen years in former burnt areas within North Portugal. Results: The achieved results showed that for a post-fire period ranging from one to 15 years, the accumulated shrubs' biomass ranged from 0.12 up to 28.88 Mg ha^-1. The model developed to estimate the shrub biomass using the time after a fire (age) as a predictor variable presented a high adjustment to data (p-value of the F statistic <0.01 and R² = 0.89), allowing estimating shrub biomass regeneration within former burnt areas with an RMSE of 3.31 Mg ha^-1. Conclusions: This paper provides practical information on the availability and assessment of shrub biomass in North Portugal, highlighting the suitability of shrubs as potential sources of biomass.