Exploring Environmental Factors That Drive Diel Variations in Tree Water Storage Using Wavelet Analysis
Exploring Environmental Factors That Drive Diel Variations in Tree Water Storage Using Wavelet Analysis
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DOI：
10.3389/frwa.2021.682285
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发表时间：
2021-08
期刊：
影响因子：
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通讯作者：
R. Harmon;H. Barnard;F. Day‐Lewis;D. Mao;K. Singha
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文献类型：
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作者：
R. Harmon;H. Barnard;F. Day‐Lewis;D. Mao;K. Singha
树木内部的水储存可以是一个关键的水库，帮助树木克服短期和长期的环境压力。我们监测的变化，在内部树水存储在黄松的每日和季节尺度上使用水分探头，测树仪，和时间推移电阻率成像（ERI）。这些数据被用来调查如何在树内储水模式的树干液流速率，土壤水分和气象因素，如蒸汽压赤字的变化的影响。木质部流体电导率的测量是恒定的，在生长季节的早期，而倒边材电导率稳步上升，表明边材电导率的增加并没有导致木质部流体电导率的增加。茎电导率的季节性增加对应于树干直径的季节性增加，这表明电导率的增加可能是由于新的增长。在日尺度上，倒边材电导率的变化对应于边材水分的变化。小波分析表明，反电导率和树干液流之间的滞后时间增加风暴事件后，这表明，土壤湿润，依赖内部水存储减少，因为需要的时间来填补日常赤字的内部水存储。我们发现短的时间滞后液流和逆电导率与干燥条件下，当黄松是已知的，以减少气孔导度，以避免木质部空化。倒边材电导率在干燥期间的昼夜振幅的下降表明，黄松依赖于内部水存储，以补充蒸腾需求，但随着干旱条件的进展，树水存储蒸腾的贡献下降。延时ERI和小波分析的结果突出了重要的作用，内部树储水支持蒸腾作用在一天内，在地下水分下降的时期。
Internal water storage within trees can be a critical reservoir that helps trees overcome both short- and long-duration environmental stresses. We monitored changes in internal tree water storage in a ponderosa pine on daily and seasonal scales using moisture probes, a dendrometer, and time-lapse electrical resistivity imaging (ERI). These data were used to investigate how patterns of in-tree water storage are affected by changes in sapflow rates, soil moisture, and meteorologic factors such as vapor pressure deficit. Measurements of xylem fluid electrical conductivity were constant in the early growing season while inverted sapwood electrical conductivity steadily increased, suggesting that increases in sapwood electrical conductivity did not result from an increase in xylem fluid electrical conductivity. Seasonal increases in stem electrical conductivity corresponded with seasonal increases in trunk diameter, suggesting that increased electrical conductivity may result from new growth. On the daily scale, changes in inverted sapwood electrical conductivity correspond to changes in sapwood moisture. Wavelet analyses indicated that lag times between inverted electrical conductivity and sapflow increased after storm events, suggesting that as soils wetted, reliance on internal water storage decreased, as did the time required to refill daily deficits in internal water storage. We found short time lags between sapflow and inverted electrical conductivity with dry conditions, when ponderosa pine are known to reduce stomatal conductance to avoid xylem cavitation. A decrease in diel amplitudes of inverted sapwood electrical conductivity during dry periods suggest that the ponderosa pine relied on internal water storage to supplement transpiration demands, but as drought conditions progressed, tree water storage contributions to transpiration decreased. Time-lapse ERI- and wavelet-analysis results highlight the important role internal tree water storage plays in supporting transpiration throughout a day and during periods of declining subsurface moisture.