基于茎干水分包络分析的活立木冻融检测方法

Freeze-thaw Detection Method of Living Standing Wood Based on Stem Moisture Envelope Analysis

为解决活立本在越冬期易遭受低温所引发的冻融灾害问题,针对现有评估检测方法存在的检测手段复杂、对活立本破坏性大、设备昂贵和难以实时检测的现状,通过分析活立本在越冬期的茎干水分和环境温度的变化规律,提出一种基于活立木茎干水分序列包络分析的冻融状况检测方法。在采用具有自主知识产权的活立木冻融检测传感器实时获取活立木茎干水分和环境温度的基础上,通过对照试验选取1320 min作为包络分析的信号采样间隔获取数据的极值信息,以便对活立木的冻融状况进行定量表示。进一步利用活立木茎干水分包络上下线的平均值,并结合环境温度的包络下线值建立归一化的冻融状况评价指标的计算模型,为植物冻融状况的实时检测与评估提供一种新思路、新手段。选用3种不同地区的阔叶树种(紫薇、海棠和香杨树)进行试验验证,整个越冬期紫薇树的冻融状况轻微,对应的冻融指标最高为0.004,远小于1.0;海棠树的冻融状况变化较大,对应的冻融指标在0.1~0.7之间波动变化;香杨树的冻融状况相对严重,对应的冻融指标最高时可达0.9。试验表明本文方法及自主研发的冻融检测传感器准确可靠,可以作为活立木冻融状况检测的有效手段,为植物冻灾预警提供理论及数据支撑。

In order to solve the problem of freeze-thaw disasters caused by low temperatures that living standing wod were vulnerable during the overwintering period.A method for freeze-thaw detection was proposed based on the sequence envelope analysis of stem moisture of living standing wood during the overwintering period by analyzing the change of stem moisture and environmental temperature data.Firstly,based on the use of a freeze-thaw detection sensor with independent intellectual property rights,the real-time information on the stem moisture and environmental temperature of living standing wood was obtained,and the changes of stem moisture and environmental temperature data of living standing wood during the overwintering period were clarified through pre-tests by the research team of Beijing Forestry University and the research team.However,ambient temperature was indirectly related to the physiological state of the living standing wood and cannot be used alone as a basis for determining freeze-thaw conditions,and the change of stem moisture of standing trees during the winter due to water-ice interactions in the stem can reflect the freeze-thaw conditions of the living standing wood.Secondly,a method of freeze-thaw condition detection based on the envelope analysis of stem moisture series was proposed.And 1320 min was selected as the signal sampling interval for the envelope analysis to obtain the extreme values of the data for quantitative representation of the freeze-thaw condition of living standing wood.The mean values of the upper and lower lines of the stem moisture envelope and the lower line of the envelope in combination with the ambient temperature were used to establish a normalised calculation model of the freeze-thaw condition assessment index.Finally,three broad-leaved tree species(Violet,Begonia and Balsam Poplar)were chosen as representatives to verify the generalisability of the method based on the sequence envelope analysis of stem moisture in standing wood during freeze-thaw.The experimental site of Violet was located at Sanqingyuan Nursery of Beijing Forestry University,Haidian District,Beijing(116°21′14″E,40°0′54″N),for the period of November 1st,2018—April 1st,2019.The experimental site of Begonia was located at the nursery of Hesheng Institute of Ecological Science and Technology,Horinger County,Huhhot City District,Inner Mongolia(111°50′28″E,40°32′33″N),for the period September 1st,2018—June 1st,2019.The experimental site of Balsam Poplar was located at the experimental forestry farm under Northeast Forestry University in Maor-Mountain,Harbin City,Heilongjiang Province(127°34′48″E,45°16′12″N),for the period October 1st,2018-May 1st,2019.The freeze-thaw condition of the Violet was slight throughout the wintering period,with a maximum freeze-thaw index of 0.004,much less than 1.0.The freeze-thaw condition of the Begonia tree was more variable,with a fluctuating index between 0.1 and 0.7.The freeze-thaw condition of the Balsam Poplar was relatively severe,with a maximum freeze-thaw index of 0.9.The tests results showed that the proposed principle and the self-developed freeze-thaw detection sensor were accurate and reliable,and can be used as an effective means to detect the freeze-thaw condition of living standing wood,which can provide theoretical and data support for early warning of plant frost damage.