Camposeo Salvatore, Vicino Francesco, Vivaldi Gaetano Alessandro, Pascuzzi Simone
Department of Soil, Plant and Food Science, Università di Bari Aldo Moro, Bari, Italy.
Front Plant Sci. 2023 Apr 21;14:1155120. doi: 10.3389/fpls.2023.1155120. eCollection 2023.
The Mediterranean basin is home to centuries-old large olive trees; high-vigor cultivars are widespread, with training forms poorly adapted to mechanical harvesting by trunk/branch shakers. The significant quantity of leaves, the considerable tree height, and the presence of multiple dichotomous hanging branches reduce the transmission of vibrations applied by the branch-shaker machines. Thus, re-shaping pruning may improve the performance of this modern mechanical harvesting method by focusing on removing both the hanging branches and those forming dichotomies. The goal of this study was to evaluate the dynamic responses of large-sized olive trees to pruning (or not) through various field tests under different excitation forces. We hypothesized that more rational pruning could significantly increase vibration transmissions.
To assess the transmission of vibrations, tests were conducted before and after the pruning on representative trees. Tri-axial accelerometers packed in a small titanium housing were used. Trees were assessed before and after the re-shaping pruning. This study reports the first data about the dynamic behavior of centuries-old tree skeletons, in the context of very large-sized olive trees, while taking into account the effects of two different vibrations application modes: a realistic one represented by the system vibration head-tree, originated when the gripper of a shaking machine wrapped and fastened the main branch of the olive trees, and a more speculative one, represented by a single impulse of a short-duration force originated by a hammer.
After pruning, spectral density increased 10 fold in the tertiary branches of pruned trees (ranging 1.0-10 m s) compared to that of not-pruned ones (ranging 0.1-1.0 m s) at frequency >50 Hz under vibration excitation. Moreover, vibrational decay times (120-150 ms) and amplitude (>10 m s) were higher under single-impulse excitation.
A more rational pruning applied to ancient large-sized olive trees significantly increased the vibration transmission under both impulse and vibratory excitation forces, without affected their typical "look". Moreover, these insights are helpful in turn in achieving maximum fruit-removal efficiency. These insights could be applied to various horticultural conditions which would improve the economic sustainability of monumental olive trees, a key portion of the Mediterranean landscape and cultural heritage.
地中海盆地生长着数百年树龄的大型橄榄树；高活力品种广泛分布，其整形方式不太适合用树干/树枝振动器进行机械采收。叶片数量众多、树体相当高大以及存在多个二叉状悬垂枝条，会降低树枝振动器施加的振动传递。因此，通过着重去除悬垂枝条和形成二叉状的枝条，整形修剪可能会提高这种现代机械采收方法的性能。本研究的目的是通过在不同激振力下进行的各种现场测试，评估大型橄榄树对修剪（或不修剪）的动态响应。我们假设更合理的修剪可以显著增加振动传递。
为了评估振动传递，在修剪前后对代表性树木进行了测试。使用了封装在小型钛制外壳中的三轴加速度计。在整形修剪前后对树木进行了评估。本研究报告了在非常大型橄榄树的背景下，关于数百年树龄树体骨架动态行为的首批数据，同时考虑了两种不同振动施加模式的影响：一种是由振动头 - 树系统代表的实际模式，当振动采收机的夹具包裹并固定橄榄树的主枝时产生；另一种是更具推测性的模式，由锤子产生的短持续时间力的单个脉冲代表。
修剪后，在振动激励下，频率>50Hz时，修剪树木的三级枝条的谱密度相比未修剪树木（范围为0.1 - 1.0m/s）增加了10倍（范围为1.0 - 10m/s）。此外，在单脉冲激励下，振动衰减时间（120 - 150ms）和振幅（>10m/s）更高。
对古老大型橄榄树进行更合理的修剪，在脉冲和振动激励力下均显著增加了振动传递，且不影响其典型外观。此外，这些见解反过来有助于实现最大的果实采收效率。这些见解可应用于各种园艺条件，这将提高具有纪念意义的橄榄树的经济可持续性，而橄榄树是地中海景观和文化遗产的关键组成部分。
