The detection of stem water content is necessary as it is an important indicator for measuring woody plant vitality. However, the relationship between stem water content, determined by non-destructive, real-time, and long-term monitoring, and woody plant vitality remains undefined. In this study, the response of woody plant vitality to stem water content under different stress (freeze–thaw, pest, or drought) was analysed by mining the dynamic characteristics of the stem water content in different woody plants at the temporal scales of year, month, and day. Compared with unstressed trees, stressed trees had contrasting diurnal patterns. The stem water content in Populus koreana Rehd. during the freeze period was much lower than that during the thaw period, and opposite diurnal variation trends were observed during the freeze and thaw periods. The stem water content in infected Lagerstroemia indica was lower than that in uninfected L. indica, and the amplitude of the diurnal variation curve was lower in infected than in uninfected L. indica. Under drought stress, the more severe the water shortage, the lower the stem water content in Malus micromalus. When it was below a certain threshold, the diurnal variation trend was opposite to that without water shortage. In conclusion, stem water content dynamics can be used to evaluate the cold, pest, and drought response of trees, which could monitor tree health and guide forest assessment.

中文翻译：

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基于茎含水量无损实时监测的胁迫树木活力表征

茎含水量的检测是必要的，因为它是衡量木本植物活力的重要指标。然而，通过无损、实时和长期监测确定的茎含水量与木本植物活力之间的关系仍不清楚。本研究通过挖掘不同木本植物茎含水量在年份时间尺度上的动态特征，分析不同胁迫（冻融、虫害或干旱）下木本植物活力对茎含水量的响应，月份和日期。与未受胁迫的树木相比，受胁迫的树木具有截然不同的昼夜模式。朝鲜杨茎秆含水量雷德。冻结期远低于解冻期，且冻融期日变化趋势相反。感染紫薇茎秆含水量低于未感染紫薇，且日变化曲线幅度也低于未感染紫薇。干旱胁迫下，缺水越严重，小苹果茎含水量越低。当低于一定阈值时，日变化趋势与不缺水时相反。总之，茎含水量动态可用于评估树木的寒冷、病虫害和干旱反应，从而监测树木健康状况并指导森林评估。