Browsing by Subject "point dendrometer"

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  • Zweifel, Roman; Etzold, Sophia; Sterck, Frank; Gessler, Arthur; Anfodillo, Tommaso; Mencuccini, Maurizio; von Arx, Georg; Lazzarin, Martina; Haeni, Matthias; Feichtinger, Linda; Meusburger, Katrin; Knuesel, Simon; Walthert, Lorenz; Salmon, Yann; Bose, Arun K.; Schoenbeck, Leonie; Hug, Christian; De Girardi, Nicolas; Giuggiola, Arnaud; Schaub, Marcus; Rigling, Andreas (2020)
    Tree responses to altered water availability range from immediate (e.g. stomatal regulation) to delayed (e.g. crown size adjustment). The interplay of the different response times and processes, and their effects on long-term whole-tree performance, however, is hardly understood. Here we investigated legacy effects on structures and functions of mature Scots pine in a dry inner-Alpine Swiss valley after stopping an 11-yr lasting irrigation treatment. Measured ecophysiological time series were analysed and interpreted with a system-analytic tree model. We found that the irrigation stop led to a cascade of downregulations of physiological and morphological processes with different response times. Biophysical processes responded within days, whereas needle and shoot lengths, crown transparency, and radial stem growth reached control levels after up to 4 yr only. Modelling suggested that organ and carbon reserve turnover rates play a key role for a tree's responsiveness to environmental changes. Needle turnover rate was found to be most important to accurately model stem growth dynamics. We conclude that leaf area and its adjustment time to new conditions is the main determinant for radial stem growth of pine trees as the transpiring area needs to be supported by a proportional amount of sapwood, despite the growth-inhibiting environmental conditions.
  • Lintunen, Anna; Paljakka, Teemu Ville Santeri; Salmon, Yann; Dewar, Roderick; Riikonen, Anu; Hölttä, Teemu (2020)
    Understanding stomatal regulation is fundamental to predicting the impact of changing environmental conditions on vegetation. However, the influence of soil temperature (ST) and soil water content (SWC) on canopy conductance (g(s)) through changes in belowground hydraulic conductance (k(bg)) remains poorly understood, because k(bg) has seldom been measured in field conditions. Our aim was to (a) examine the dependence of k(bg) on ST and SWC, (b) examine the dependence of g(s) on k(bg) and (c) test a recent stomatal optimization model according to which g(s) and soil-to-leaf hydraulic conductance are strongly coupled. We estimated k(bg) from continuous sap flow and xylem diameter measurements in three boreal species. k(bg) increased strongly with increasing ST when ST was below +8 degrees C, and typically increased with increasing SWC when ST was not limiting. g(s) was correlated with k(bg) in all three species, and modelled and measured g(s) were well correlated in Pinus sylvestris (a model comparison was only possible for this species). These results imply an important role for k(bg) in mediating linkages between the soil environment and leaf gas exchange. In particular, our finding that ST strongly influences k(bg) in mature trees may help us to better understand tree behaviour in cold environments.