Abstract:

As a basic measure for forest management，pruning has an important impact on the tree trunk shape, wood qulity, etc. At present，in the process of growing fastgrowing and highyielding plantation, afforestation was took into account, whereas management after planting was ignored, which had much detrimental effect on woodland's quality and productivity. The paper studied the topic to find a scientific pruning model that could provide a guideline for the management in forest production. The plantation and the intercropping of poplarcrop were pruned in four different levels in Hebei and Shandong province. The levels were respectively light p1 (1/6 crown was pruned), medium p2 (2/6 crown was pruned), strong p3 (3/6 crown was pruned), heavy p4 (4/6 crown was pruned) and the control (unpruned). Heights and diameters at breast height(DBH) were measured. Diameter growth and cuttingarea increment in one year from ten parsed trees were counted.The volume growth of trunk (below 9 m) was calculated. The results were: 1) the difference of relative growth rate for different pruning treatment was not significant (P<0.05), which demonstrated the nutrition for height growth came from the branches and leaves of the top crown; 2) The difference of relative growth rate of DBH was significant(P<0.01). That is, the greater of pruning intensity, the smaller relative growth in the DBH. 3) The stem growth of parsed disk at different height was fluctuant among the different treatments. From stem base (0.0 m) to 9 m height of the trunk , the stem increase of the lower half reduced along with the increase of pruning intensity, while the growth of the upper half in pruning trees was bigger than that of non pruning ones. 4) The difference of volume growth rate for different treatments was significant, all of the pruning treatments were bigger than the control. The medium p2 had the biggest growth, and the order was CKgested that reasonable pruning can improve the growth of volume. However an excessive pruning reduced volume growth. 5) Pruning can decrease relative taper of trunk, make trunk straight and satiety, and increase the rate of volume increasing for one year. 6) In conclusion, in the process of production, the reasonable pruning should be moderate intensity as pruning p2, in which 1/3 crown length was removed.

Key words: pruning, poplar, growth rate, volume, taper of trunk