Dendrometer analysis of tree water dynamics and radial stem growth of Norway spruce in Hyltemossa
2024
Weibull, Martin
Forests which form a central part in climate change mitigation strategy of Sweden and as precipitation patterns shift and temperatures rise, understanding the responses of forests to these shifts becomes of paramount importance. Automatic high resolution dendrometers have allowed for the continuous measurement of tree radial stem growth and water dynamics, allowing for the forcings of meteorological variables to be studied at a minute-by-minute scale. This allows for the determination of which meteorological variables that drive these processes. This study assesses the conditions and dynamics of Norway spruce (Picea abies (L.) H. Karst.) in Hyltemossa, a managed forest in Southern Sweden. It was hypothesised that vapor pressure deficit (VPD) was the main driver in determining the radial growth, however the utilized methodology prevented the effects of VPD to be disaggregated from precipitation, relative humidity (RH) and photosynthetic photon flux density (PPFD). However, air temperature showed a weaker link to radial growth compared to other factors. A secondary hypothesis detailed that maximum day swelling correlated with factors driving stomatal conductance, in particular PPFD and VPD, however only maximum temperature and VPD were found to be correlated, and only under tree water stress. Key findings highlight the bimodal distribution of total radial growth, variable lengths of radial growth between trees, absence of lagged meteorological effects, and the central role of atmospheric moisture and PPFD in limiting when radial growth occurs.
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