Four-dimensional growth response of mature Larix decidua to stem burial under natural conditions

This paper illustrates the effects of abrupt stem burial (burial depth ~0.5 m) on tree growth in mature (46 ± 8 years) European larch (Larix decidua Mill.) trees. In contrast to the previous research, which was mostly carried out with saplings and on experimental sites where regular aggradation occurred through the transport of sand, this work focuses on the impact of natural, abrupt burial of mature trees with rocks contained in a sandy-silty matrix typical for debris flows in mountainous headwater catchments. The effect of burial is assessed radially and axially within the stem and over almost three decades after burial. The analysis of growth disturbances and their intensity was based on the 143 cross sections (572 growth series) taken at 10-cm intervals from 6 Larix decidua Mill. The results show quite clearly that abrupt burial causes massive suppression of radial growth as compared to pre-event conditions (mean 77 %, min 38 %, max 92 %, SD 7.2 %). The trees sampled were unable to resume pre-burial growth rates even after 25 years, but recovered to reference growth conditions (as measured in undisturbed, local reference trees) after 15 years (min 3 years, max 25 years, SD 9 years). The results differ only insignificantly between different heights along the tree axis and suppression is equally well expressed at different radial positions within the stem.