Residual tree damage along skidding trails in beech stands in Greece

We studied the damage caused to unfelled trees during skidding operations in four beech stands of northern and central Greece that were managed under differing harvesting systems.After timber was harvested we recorded and analyzed all damage to a width of 2 m along both sides of the skid trails.The percentage of damaged residual trees was 17–28 %.Higher numbers of saplings were uprooted or destroyed in parts of the stands with high natural regeneration.Most damaged trees suffered 1.33–1.90 wounds that were inflicted up to a height of 1 m above ground level.At all sites mean wound sizes were large,89–1190 cm2,and caused elevated risk of future fungal infection.The damage caused by skidding during timber harvesting can be minimized by better planning the harvest operations,and training forest workers in reduced impact logging.

Selection and experimental evaluation of shaking rods of canopy shaker to reduce tree damage for citrus mechanical harvesting

Canopy shaking system is one of the research hotspots for large-scale mechanized fruits harvesting.Shaking rods considered as one of the essential components of canopy shaker are responsible for transferring mechanical energy from shaking mechanism to different regions of tree canopy.This transfer depends on the characteristics of the shaking rods that directly strike the tree canopy.In order to evaluate the effects of the shaking rods on tree damage level and fruit removal percentage,three kinds of shaking rods with different materials or shapes were selected.Based on the results of bending deformation tests,it was proven that the rigid shaking rod(R_(1))with the material of Polyvinyl Chloride(PVC)did more resistance against producing bending deformation in comparison with the other two types of shaking rods with the material of Polyamide Nylon 12(PA).By contrast,the position close to the free end of the flexible shaking rod was easier to be deformed by less external force.In addition,dynamic analysis and vibration performance tests indicated that the rigid shaking rod could produce stronger vibration with higher shaking frequency of 4.8 Hz and maximum acceleration of 31.4 m/s^(2).Finally,the results of field trials indicated that the flexible bow-shaped shaking rod(R_(3))has a better widespread performance to achieve comparative higher fruit removal percentage up to 82.6%while producing lower tree damage rate of 5.36%.This study demonstrates that the materials or shapes of the shaking rod could significantly influence the fruit detachment rate and tree damage level.This study would provide an essential reference for the application of shaking rods for canopy shaker.

The distribution and frequency of damage to roadside trees in low-volume road construction

We investigated the distribution and frequency of damage to tree stands adjacent to low-volume roads according to the type of hillside materials involved（soil or rock） and hillside gradient in mountainous forests of northern Iran. A total of 80 plots were systematically and randomly sampled to record damaged trees（bending,crushing and wounding） by class of hillside gradient and materials at the edge of road. Tree wounding and crushing at rock slopes was significantly greater than at hillsides with a mix of clay soil（p ／ 0.05）. Damage on hillsides with slope gradients[45% were 2, 8.5 and 2.3 times more frequent than on hillsides with slope gradient／15% for bending, crushing and wounding, respectively. The damage distribution varied according by type and the most frequent damage was tree wounding（p ／ 0.05）. The damage distribution was measured at distances of 4, 5 and 8 m from the road fillslope for tree bending, crushing and wounding, respectively. Using hydraulic excavators and physical barriers（wooden obstruction and synthetic holder） during earthworks for road construction could reduce these damage.

Comparison of Skidding Performance of Small Track-type Experimental Prototype Skidder and J-50 Skidding Tractor

In this paper, field experimental comparison is made between a small track-type experimental prototype skidder and a J-50 skidding tractor. Experimental data, including skidding productivity, soil compaction on skidding trails, and damage rate of the residual trees, are analyzed. The results indicate that with the condition of scattered skidding area and low skidding volume per cycle, small track-type experimental prototype skidder has advantage on working and a higher skidding productivity. It makes lower soil compaction to the skidding trails in the depth of 0-5 cm, 5-10 cm, and 10-15 cm. Under the same work conditions, the damage rate of the residual trees made by small track-type experimental prototype skidder is only 1/5 of those made by J-50 type skidding tractor. The damage rate is reduced by 80%.

Design and evaluation of a two-section canopy shaker with variable frequency for mechanical harvesting of citrus

Canopy shaking is one of the most commonly used techniques for mechanical harvesting of citrus fruits in orange juice industry.However,tree damage and low harvesting efficiency are the top concerns of growers in adopting the existing harvesting equipment on a large scale.The purpose of this research was to develop a novel canopy shaking system to minimize tree damage and maximize fruit removal for mechanical citrus harvesting.In this study,a two-section canopy shaker composing of top and bottom shaking systems mounted on two rotating drums was proposed and developed.It was configured with two sets of flexible bow-shaped shaking rods in a staggered distribution,which can shake the top and bottom zones of the tree canopy independently.The shaking system was designed based on a linked crank-rocker mechanism.Kinematic simulation analysis was conducted to verify the quick return characteristics and differential properties of this mechanism.Vibration test showed that the frequency of the shaking rod could be adjusted within a range of 1.1-8.8 Hz related to hydraulic motor speeds.The field tests of the shaking system with an average frequency of 4.7 Hz achieved a fruit removal percentage of 82.6%and tree damage rate of 5.4%under a tractor speed of 3 km/h.By contrast,the combined shaking frequency of 4.7 Hz&4.1 Hz of the canopy shaker produced less tree damage with a percentage of 3.9%.This study indicated that the two-section canopy shaker with an optimized frequency combination could be adaptable to the different zones of the tree canopy,and obtain lower tree damage and higher fruit removal percentage.

Performance evaluation of lateral canopy shakers with catch frame for continuous harvesting of oranges for juice industry

Citrus is mainly oriented to fresh consumption,and harvesting is usually performed manually.However,the high cost of harvesting and the low availability of labour can compromise the profitability of the crop when it is destined to juice industry.The development of citrus mechanical harvesting for industrial processing is conditioned to reach a high fruit removal efficiency,with a reduced damage to both fruit and trees.The current machines available are very large,requiring extensive plantations with long rows of trees to be efficient.In this study,two lateral canopy shakers equipped with a catch frame were evaluated to harvest independently both sides of the hedge on intensive citrus plantations with the main objective of determining their performance and feasibility.The lateral canopy shakers tested were three tractor-drawn machines,one commercial machine and two prototypes.The tested machines reached a mean value of 78%of fruit removal.Besides,the prototypes,equipped with a catch frame,were able to recover a mean value of 70%of yield.Although the results were promising,for achieving an efficient result,the application of this harvesting technology still requires a process of improvement,and the adaptation of both the machine and the plantation.The machines should reduce the amount of post-harvest ground fruit(5.9%-10.4%).Tree damages generated by the contact of the catch frame with the trunk and the metal rods with main branches were the most relevant.Therefore,it is still necessary to increase the ground speed of the machinery and improving the design of the rods,regulating the rod penetrating deep in the canopy to improve the fruit recovery and limit the damage caused to the trees.