Climate change and the global economy impose new challenges in the management of food-producing trees and require studying how to model plant physiological responses, namely growth dynamics and phenology. Hazelnut (Corylus avellana L.) is a multi-stemmed forest species domesticated for nut production and now widely spread across different continents. However, information on stem growth and its synchronization with leaf and reproductive phenology is extremely limited. This study aimed at I) defining the sequencing of radial growth phases in hazelnut (onset, maximum growth and cessation) and the specific temperature triggering stem growth; II) combining the stem growth phases with leaf and fruit phenology. Point dendrometers were installed on 20 hazelnut trees across 8 orchards distributed in the Northern and Southern hemisphere during a period of three growing seasons between 2015 and 2018. The radial growth variations and climatic parameters were averaged and recorded every 15 minutes. Leaf and reproductive phenology were collected weekly at each site. Results showed that stem radial growth started from DOY 84 to 134 in relation to site and year but within a relatively narrow range of temperature (from 13 to 16.5°C). However, we observed a temperature-related acclimation in the cultivar Tonda di Giffoni. Maximum growth always occurred well before the summer solstice (on average 35 days) and before the maximum annual air temperatures. Xylogenesis developed rapidly since the time interval between onset and maximum growth rate was about 3 weeks. Importantly, the species showed an evident delay of stem growth onset with respect to leaf emergence (on average 4–6 weeks) rarely observed in tree species. These findings represent the first global analysis of radial growth dynamics in hazelnut, which is an essential step for developing models on orchard functioning and management on different continents.

中文翻译：

---

南北半球果园多茎植物（Corylus avellana L.）的径向茎生长动力学和物候

气候变化和全球经济对产粮树木的管理提出了新的挑战，需要研究如何模拟植物的生理反应，即生长动态和物候。榛子 ( Corylus avellanaL.) 是一种为生产坚果而驯化的多茎森林物种，现在广泛分布在不同的大陆。然而，关于茎生长及其与叶和生殖物候同步的信息极为有限。本研究旨在 I) 确定榛子径向生长阶段的顺序（开始、最大生长和停止）和触发茎生长的特定温度；II) 将茎生长期与叶和果实物候相结合。在 2015 年至 2018 年的三个生长季节期间，分布在北半球和南半球的 8 个果园的 20 棵榛子树上安装了点测树仪。每 15 分钟对径向生长变化和气候参数进行平均和记录。每周在每个地点收集叶子和生殖物候。结果表明，与地点和年份有关的茎径向生长从 DOY 84 开始到 134，但在相对较窄的温度范围内（从 13 到 16.5°C）。然而，我们在栽培品种 Tonda di Giffoni 中观察到与温度相关的驯化。最大增长总是发生在夏至之前（平均 35 天）和最高年气温之前。由于发病和最大生长速率之间的时间间隔约为 3 周，因此木糖生成迅速发展。重要的是，在树种中很少观察到，相对于叶片出现（平均 4-6 周），该物种表现出明显的茎生长开始延迟。这些发现代表了对榛子径向生长动态的首次全球分析，这是开发不同大陆果园功能和管理模型的重要步骤。