Modelling the biomass of Lebanon oak sprouts and it’s response to thinning in northern Zagros forests (The case of Baneh, Kurdistan Province)

This study was carried out to understand the dynamics of Lebanon oak coppice regeneration. In this regard, the effect of thinning on both individual sprouts and stools as well as estimation of sprout biomass using allometric equation were investigated. 45 Lebanon oak trees with different sizes (i.e. DBH from 25 to 65< cm) in five sites were cut and individual stumps were fenced to monitor the sprouting behavior. In the second year after the cutting, light (six sprouts reserved in each stool) and heavy thinning (three sprouts reserved in each stool) were conducted in two third of stools equally and the rest un-thinned ones were considered as control. Data analysis, five years after thinning, showed that the most portion of individual biomass allocated to main stem (57.4%), main branches, leafs and fine branches, respectively. On average 42% of total fresh mass of sprouts were reduced due to water loss in drying process. Analysis of variance indicated that stump size has no significant effect on biomass of individual sprout either stools while it was significantly different among sites. Comparison of thinning treatments and control one showed that light thinning resulted in sprouts with the most biomass while no significant difference was observed between heavy thinning and un-thinned. Using a basic power model, allometric equation was fitted to estimate the sprout biomass. Based on regression analysis as well as derived indicators (R2, STDEV, RMSE, rRMSE and nRMSE) and models validation by leave one-out method, the collar diameter was found as the best explanatory variable in young sprouts biomass.