Stand level lumber recovery rate of Pinus patula at Shashemane Wood Industry Enterprise, South Oromiya

In Ethiopia the studies of lumber recovery rate for different exotic as well as indigenous tree species were very limited. Particularly, stand level lumber recovery rate assessment was not practiced at all. Forest managers responsible for marketing, work study and logging planning require detailed information on the potential yield and lumber size distribution likely to result from felling a stand of trees. The aim of this study was to assess stand level lumber recovery rate shortly before harvesting.The study was carried out in Shashemanne Wood Industry Enterprise. Stands in three different compartments were selected. There10 x 10m sample plots from each compartment were taken for the analysis of stand level recovery rate. The three selected compartments were similar in age, initial spacing, as well as pruning stage. The only differences between them were site condition and thinning practices.The trees in each selected sample plot were marked and measured for total height and felled by a logging team. Diameter measurement of butt and top end both over and under bark, was carried out and log volume calculated using Smalian formula. The logs were sawn by feeding top end first and the volume of each piece of lumber was measured separately. The result obtained was compared with a theoretical recovery rate obtained from sawing simulation software. All in all 263 logs of P. patula were extracted and processed into 1555 boards. The analysis of stand level recovery rate was made based on full stem volume, merchantable log volume, over and under bark, as well as, theoretical condition.Based on full stem volume the recovery rates were 29%, 35% and 45% for the three stands. Such differences will have a great effect on the economy of utilization of P. patula. The stand on the high site index with third thinning yielded the highest recovery rate compared with the second thinning stand. Beside thinning, log defects (bow) due to site difference showed a great effect on overall stand level lumber recovery rate, as much lumber was lost in the form of slabs and trims to get center boards. The theoretical recovery rate showed a high correlation with actual recovery rate for compartments with better management practice and site condition. The software did not fit well for the site with a high frequency of log defects (bow).The stand level lumber recovery rate of a given plantation could be improved by proper thinning at the proper time, training of the mill's workers, appropriate maintenance of mill machinery and an adequate supply of equipment.