Assessing reach of the stems to be removed and the quality of remaining stand in machined [thinning] | Izvācamo koku aizsniedzamības faktoru un paliekošās audzes koku kvalitātes izvērtējums krājas kopšanas cirtes mašinizētā izstrādē

Assessed is the reach of the stems to be thinned out by a harvester in machined thinning. The aim of the study, conducted on 12 different stands in the Zemgale and Vidusdaugava Forestry of the AS ''Latvijas valsts meži'', is to evaluate how easy a harvester type machine can reach the stems to be cut down. In preparing the felling sites for operations in the belts next to the striproads all the stems to be removed were marked using a luminescent paint (for working also at night). The operator was supposed to remove the marked stems while in the belt midway between the striproads the stems to be removed were after the operator’s judgement. After the operations the sample plots for evaluating the results of thinning were arranged by dividing the area between striproads in three belts, normally 16.0m wide with one side of the sample plot 5.3 m and the other 18.87 m long to get the sample plot of the size 100 m2. The sample plots were arranged so that 22-25% of the felling sites were surveyed. The field data were analysed to establish the average density of remaining stand in each belt, the number of mechanically damaged and undamaged stems, as well as those crooked or with crown defects, and the dead stand. Analysed was also the visibility from the operator's cabin for the Ponsse Beaver, John Deere 1070d, and Valmet 901.4 harvesters. The percent of the visibility of working zone was assessed after the so-called shadow method, based on a 15 × 20 m square arranged around the harvester and evaluating the shadow zones of the artificial light at night around the machine. During the operations observations were made at the harvester’s stop points, evaluating the area visible by the operator from the cabine. It was concluded that the factors affecting machined thinnings by using hydraulic boom and grapple type harvesters fall into three groups: techical specifi cations of the harvester, stand parameters, and visibility from the operator’s cabin. It was found that in the belt midway between the striproads the proportion of remaining stems because of no possibility to reach them is by 15-35% higher than in the belts next to the striproad. Th is results in a situation where easy-to-reach belt of the forest stand next to the striproad is thinned more heavily than that midway. Furthermore, the work zone visibile from the operator’s cabin is different for different harvester models. When evaluating the harvester’s stop points on the striproad, it was found that in 25% of the cases the machine had to be moved by 1.5 m backward or forward to find the best position for reaching the stems to be thinned out.