Abstract:

Aims As a typical water-related physiological parameter, the stem water content of living standing trees has always been one of the most effective characterization parameters of the life state of living standing trees, which plays an important role in maintaining the water balance of the whole tree, and has been highly valued by researchers and forest tender. However, the method of obtaining stem water content sequence of living standing trees has been affected by factors such as cumbersome operation, expensive cost, poor real-time performance, low accuracy and damage to the life of living standing trees, which limits its in-depth research and application. We innovatively adopted a stem water content sensor with independent intellectual property rights to obtain the stem water content of standing trees in real time and non-destructively, and conducted a thorough investigation of the stem water content sequence and its influencing factors.

Methods A common virescence tree species Acer pictumsubsp. mono was chosen as the research object. The stem water content sensors based on the standing wave rate principle independently developed by our team were used to achieve in-situ and non-destructive monitoring of stem water content in the growing season. Meanwhile, meteorological parameters were simultaneously measured. The sequence characteristics of stem water content and its response to meteorological factors at different stages of growing season were analyzed.

Important findings (1) In spring (April) and mid-late autumn (from September to October), the stem water content presented the rhythm of “rising in the day and falling in the night”, while from summer to middle autumn (from May to August) presented a rhythm of “falling in the day and rising in the night”; the daily range and maximum of stem water content would be inhabited under the cloudy day, while rainy days led the stem water content surge to a large value, and dry days dropped the stem water content. (2) During the germination stage, the main meteorological factors that had direct effects on the variation of stem water content were air temperature and vapor pressure deficit. During the growth period, the main meteorological factors directly affecting stem water content were vapor pressure deficit and soil temperature. During the defoliation stage, the main meteorological factors that had direct effects on stem water content were air temperature and vapor pressure deficit, and the Pearson correlation coefficients between stem water content and these two factors were higher. A stepwise regression analysis method was used to model the relationship between stem water content and various meteorological factors in these three periods, the meteorological factors entering the regression model at different periods were different. In conclusion, this study revealed that stem water content exhibited different sequence characteristics and influencing factors under the synergistic effects of different meteorological factors, which could provide some insights into the internal water transport capacity and environmental adaptation mechanism of plant stems.

Key words: Acer pictum subsp. mono, stem water content, meteorological factor, growing season