Authors

Abstract

ABSTRACT In most mid-to high-latitude regions, trees are frequently subjected to severe freeze-thaw stress during the overwintering period, yet accurately detecting their freeze-thaw status remains challenging. In this study, Malus spectabilis, a common ornamental tree species in northern China, was selected as the research subject. A self-developed stem water content sensor based on the standing wave ratio (SWR) principle, in combination with a miniature thermocouple array, was employed to achieve in situ and non-destructive monitoring of internal stem water dynamics and radially stratified stem temperature. Furthermore, an Internet of Things (IoT)-based plant freeze-thaw monitoring system was established. The temporal variation characteristics of these parameters during overwintering were analyzed, on the basis of which a computational model of the freeze-thaw process was developed, and a novel method for detecting stem freeze-thaw dynamics was proposed. The results revealed that alternating freeze-thaw cycles in stems are accompanied by distinct endothermic and exothermic phenomena, with the freezing and thawing processes progressing radially from the outer to the inner stem layers—allowing the migration trajectory of freeze-thaw peaks to be tracked. In addition, different types of plant fiber materials were applied to stem tissues to verify the effectiveness of cold-resistance measures. This study provides new insights into the mechanisms regulating tree cold hardiness during overwintering and offers practical references for the scientific management of trees in cold regions.

Abstract in Chinese

在中高纬度地区，树木在越冬期间常受到严重的冻融胁迫，但其冻融状态的准确检测仍具有较大挑战性。本研究以北方常见的观赏树种海棠（Malus spectabilis）为研究对象，采用自主研发的基于驻波比（SWR）原理的茎干水分传感器，结合微型热电偶阵列，实现了茎干内部水分动态及径向分层温度的原位、无损监测。同时，构建了基于物联网（IoT）的植物冻融监测系统。通过对越冬期间上述参数的时序变化特征进行分析，建立了茎干冻融计算模型，并提出了一种新的茎干冻融动态检测方法。结果表明，茎干内交替的冻融循环伴随着明显的吸热与放热现象，冻融过程沿径向由外向内推进，可实现冻融峰迁移轨迹的动态跟踪。此外，本研究还采用不同类型的植物纤维材料包裹茎干组织，以验证防寒措施的有效性。本研究为阐明树木越冬期的抗寒调控机制提供了新的认识，也为寒冷地区树木的科学管理提供了实践参考。