جستجوی مقالات مرتبط با کلیدواژه « pruning » در نشریات گروه « جنگلداری »

The semi-arid vegetation area of Zagros is the second source of forest biomass in Iran and has a special environmental importance. Over the past decades, the ecological potential of this region has degraded due to severe human pressure, and its forest trees have declined in the last two decades due to drought stress and attacks by wood-eating pests and charcoal fungi. Since chemical control further disturbs the natural conditions in ecosystems and biological control requires long-term research, so the application of sanitary cuttings is the most important way to control the degradation of Zagros forests in the current situation. Numerous scientific references have reported the positive role of branching and pruning of forest and garden trees in controlling pests and diseases. This article is the results of the second phase of a study that investigated the proper method of sanitary cutting in the forests of the Zagros vegetation area in the next four years. The aim was to investigate the role of five cuttings treatments in two forms of high and coppice to control the dieback of Persian Oak trees in the Zagros area.

In this study, the effects of vegetative form and sanitary cuttings on the survival and vitality of Persian oak after eight years was tested and compared with the project results in the four-year period of the first phase. Vegetative form was studied at two levels of high and coppice and cutting type in five levels including removal of infected parts of trees, complete removal of crown, cutting from height 10 cm and cutting from 10 cm depth and control treatment (without sanitary cutting). The researches treatments were compared with non-parametric tests due to the quality of the vitality data and the lack of parametric statistics assumptions in the survival treatments. Pair of two-phase research treatments were compared with Wilcoxon test, two vegetative form treatments with Mann-Whitney test and group cutting treatments with Kruskal-Wallis test and in pairs with Dunn-Bonferroni test.

The results showed that the difference in survival and vitality of the two vegetative forms in the two phases of the study was not significant at the 5% probability level. The difference of survival of cutting treatments in the two phases of the study was significant in all treatments at the level of 1% probability, except in the treatment of cutting infected sections. The difference of viability of cutting treatments in the two phases of the study was significant only in the control treatment at the level of 1% probability, in contrast to survival. The results of survival and vitality after eight years from the start of the experiment in the second phase showed a significant difference (α=1%) in the cutting treatments and no significance (α=5%) in the two vegetative form treatments. Also, the results of pairwise comparisons showed that the difference in the vitality percentage of the two treatments cut from the depth and from a height of 10 cm with the control treatment and the difference between the two treatments of cutting infected parts and complete cutting of the crown were not significant (α=1%).

In general, the targeted cutting treatment of infected parts in terms of survival (88.8%) which was the main factor of the study showed the best result alone and in terms of vitality (87.4%) with complete crown cutting treatment. Therefore, this sanitary cut is recommended to control the dieback of Persian oak trees in similar forest areas in the Zagros.

Pruning and eliminating some of the shoots of each poplar tree at short rotation method helps the reminder shoots to use more nutrition, light and water and produce stems with high diameter and height which can be used at high productivity industries such as paper production. The aim of the research was to study the effect of different levels of pruning on wood production per area unit, as well as their effect on wood dimensions. The trial was conducted under the experimental design of split plots at three replicates at four year period (2004-2007) in Alborz Experimental Complex, Karaj city of I.R. Iran. The main treatments consisted of five outstanding poplar clones (Populus x euramericana costanzo, Populus x euramericana vernirubensis, Populus euramericana triplo, Populus x euramericana 561.41 and Populus x deltoids 63.8) and the secondary treatments consisted of different remaindered shoots at each poplar tree. The shoots height and diameter were measured annually at the end of growth period of the poplars. The wooden biomass wet and dry weight was measured at the end of the trial. The data were analyzed, using the SAS software. The results showed that the average number of the shoots varied between three (minimum) at control treatment for each tree of P.d. 63.8 and 5.8 (maximum) for each tree of P. e. 561.41. These two poplar clones had greater diameter and height than the other clones. The average total height and diameter of the single shoot was more the bishoots and the bishoots were more than the multishoots. The greatest and the lowest average of dbh belonged to P.d. 63.8 at single shoot treatment and P.e. vernirubensis at multishoots treatment, respectively. The greatest and the lowest total height belonged to P.d. 63.8 (9.14 m.) and P. e. 561.41 (4.24 m.), respectively and there were different differences between the clones and different treatments in respect to average of diameter and total height. The highest and the lowest amount of biomass belonged to P.d. 63.8, P. e. 561.41 and P.e. vernirubensis, respectively and there was significant difference between the clones in respect to iomass production. Biomass production in the P. euramericana clones at multishoots treatment (control) was more than the single and bishoot treatments, whereas in P. deltoids it was greater in single shoot treatment than the bio and multishoots treatments. The heighest and the greatest biomass (dry weight) production belonged to P.e. vernirubensis at single shoot treatment (9.2 tone/ha/yea) and P.d. 63.8 at singe shoot treatment (19.3 tone/ha/year), respectively.

The determination of survival and vigority effective parameters on old saxaul (Haloxylon aphyllum) shrub is essential for sustainable development of planted forests in desert area. In fact, the objective of this study was to determine the effects of different density and pruning levels on survival and the vigority of saxaul. The study was carried out in obviously wilted planted saxaul forest that is located in Ashkezar desert region of Yazd province. Experiment was conducted in split plot design with main-plots that had 250 and 125 trees per ha and sub-plots were 3 types of pruning at height of 10, 35 and 70 cm above ground surface, plus control (no pruning) sub-plot. Pruning was done on autumn 1994. After one year from shrubs pruning, analysis of plant mortality percentages was started and continued on the same pruning time to 2000. The determination of vigority carried out only in 2000. Results showed that the differences of survival among all treatments were not significant. The effect of density on vigority was also not significant, whereas the pruning height had significant effect (p<0.01) on vigority of saxaul shrubs. One can conclude that the best pruning method was cutting 35 cm above ground with vigority of 43.3% and 40.9% in 250 and 125 trees per hectare treatments, respectively.