Impact of degradation on the above-ground biomass of plants composing the shrub layer of Djebel Zaghouan

The above-ground shrub biomasses were studied in a degradation sequence of Djebel Zaghouan. The plots of 25 and 400 m2 each were geolocated with a breakdown into three stages of degradation: degraded, moderately degraded and preserved. Mathematical models were developed for each species to determine the relationships of aboveground biomass as a function of biovolume and crown surface. Regression equations are of different types: logarithmic, power, polynomial, linear and exponential with high coefficient of determination (R2). The highest total phytomass was recorded at station 14 with an average production of 17.48t / ha and a significant degree of recovery of 61.13%. However, the lowest aerial phytomass was recorded in station 22 (0.561t / ha) with a recovery rate of 6%.