Abstract
BackgroundThe dynamics of cambial activity and xylogenesis provide information on how and to what extent wood formation respond to climatic variability. The Lebanon Cedar (Cedrus libani A.Rich) is a montane tree species which is distributed along a wide altitudinal range in the northeastern Mediterranean region, currently considered as a potential forest species for Central Europe with respect to climate change. This study provides first data on intra-annual growth dynamics at cellular level using the microcore technique for a montane Mediterranean tree species at different altitudes within and outside its natural range.ResultsMicrocores were collected fortnightly in the growing season of 2013 in order to study temporal dynamics of cambial activity and xylogenesis in stems of C. libani at different altitudes in the Taurus Mountains (1000 – 2000 m a.s.l.) and at a plantation at Bayreuth (330 m a.s.l.; Germany). The dormant cambium consisted of about 5 cells at the Turkish sites and 7 cells at Bayreuth. Cambial activity set in, when daily minimum temperatures exceeded 0 °C and daily means of air and stem temperature exceeded 5 °C. Xylogenesis started between April and May, ended approximately the end of September to the beginning of October and lasted 134 (at tree line) to 174 days (at the lowest Turkish site). Mean ring widths varied from 0.55 to 3.35 mm, with highest values observed at Bayreuth very likely resulting from a steady water supply during growing season. Means of daily cell production rates varied from 0.73 to 0.12. Samples containing traumatic resin ducts occurred only rarely and where not used for analysis.ConclusionsIn C. libani, onset and dynamics of cambial activity and xylogenesis are triggered by daily means of stem and air temperatures whereas water availability has a higher influence on growth rates and cessation of wood formation. Within sites, duration of xylogenesis does not significantly differ with respect to age and tree size. C. libani grows well outside its natural range and thus may be a promising species for forestation in Central Europe with respect to climate change. We suggest further studies on if/how traumatic resin ducts influence tree ring width.Electronic supplementary materialThe online version of this article (doi:10.1186/s40529-015-0100-z) contains supplementary material, which is available to authorized users.
Highlights
The dynamics of cambial activity and xylogenesis provide information on how and to what extent wood formation respond to climatic variability
The objective of the study was to determine with the use of the microcore method (a) how cambial activity and xylogenesis in stems of C. libani take place along an altitudinal gradient (b) how dynamics of cambial activity and xylogenesis are linked with contemporary microclimatic conditions and (c) how xylogenesis of C. libani occur under central European climate conditions where a uniform water supply is available throughout the year
Temperature, especially daily means of air and stem temperature, appeared to be the main trigger when it comes to the onset of cambial activity and xylogenesis, whereas water availability and other factors, e.g. stand structure, light exposure etc., affect the total annual increment
Summary
The dynamics of cambial activity and xylogenesis provide information on how and to what extent wood formation respond to climatic variability. Some studies used the microcore method to investigate wood formation of Mediterranean tree species with the aim to determine the influence of climate parameters on cambial activity and xylogenesis. To our knowledge there are no studies present which investigate cambial activity and xylogenesis of a montane (oreophilous) Mediterranean tree species along an altitudinal gradient which could contribute to a better understanding on how the dynamics of wood formation change with altitude and varying site-specific conditions. The objective of the study was to determine with the use of the microcore method (a) how cambial activity and xylogenesis in stems of C. libani take place along an altitudinal gradient (critical timings of the onset of cell production, termination of wood formation, cell number and ring width) (b) how dynamics of cambial activity and xylogenesis are linked with contemporary microclimatic conditions (air temperature, rain, drought) and (c) how xylogenesis of C. libani occur under central European climate conditions where a uniform water supply is available throughout the year (no severe summer drought). Based on the information of xylogenesis we present an initial insight on the effect of spring temperature on the onset of growth and the relative role of vegetation period on seasonal growth when drought periods are present or missing
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