Abstract
Dendroclimatological studies in a dry inner Alpine environment (750 m a.s.l.) revealed different growth response of co-occurring coniferous species to climate, which is assumed to be caused by a temporal shift in wood formation among species. The main focus of this study therefore was to monitor intra-annual dynamics of radial increment growth of mature deciduous and evergreen coniferous species (Pinus sylvestris, Larix decidua and Picea abies) during two consecutive years with contrasting climatic conditions. Radial stem growth was continuously followed by band dendrometers and modelled using Gompertz functions to determine time of maximum growth. Histological analyses of tree ring formation allowed determination of temporal dynamics of cambial activity and xylem cell development. Daily fluctuations in stem radius and radial stem increments were extracted from dendrometer traces, and correlations with environmental variables were performed. While a shift in temporal dynamics of radial growth onset and cessation was detected among co-occurring species, intra-annual radial growth peaked synchronously in late May 2011 and early June 2012. Moist atmospheric conditions, i.e. high relative air humidity, low vapour pressure deficit and low air temperature during the main growing period, favoured radial stem increment of all species. Soil water content and soil temperature were not significantly related to radial growth. Although a temporal shift in onset and cessation of wood formation was detected among species, synchronous culmination of radial growth indicates homogenous exogenous and/or endogenous control. The close coupling of radial growth to atmospheric conditions points to the importance of stem water status for intra-annual growth of drought-prone conifers.
Highlights
A major factor affecting radial stem growth and wood formation in trees is climatic variation
The dormant cambium consisted of 5–6 cells in P. sylvestris and L. decidua, when there was no cambial activity from July through March (Fig. 2a, b)
Results of our study provided an insight into environmental control of intra-annual radial growth of co-occurring coniferous trees exposed to drought
Summary
A major factor affecting radial stem growth and wood formation in trees is climatic variation. Decade-to-century long-time series of radial tree growth (ring width) are related to climate variables (e.g. monthly mean temperature and total precipitation) to determine growth-limiting climatic factors (Fritts 1976). A combination of dendroclimatological and intra-annual growth studies is recommended to assess longand short-term climatic influences on tree growth, respectively (Deslauriers et al 2003a; Rossi et al 2006b; Gruber et al 2009). Knowledge of intra-annual dynamics of radial tree growth allows determination of (1) crucial phenological stages of radial growth, i.e. onset, time of maximum growth, end and duration of wood formation, (2) seasonal influence of meteorological factors on growth and (3) species-specific response to climate change
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