Monitoring natural Pinus sibirica regeneration in virgin and secondary forest stands of the west Sayan rain-shadow mountain landscapes

V.N. Sukachev Institute of Forest SB RAS, Krasnoyarsk, Russia

Rain-shadow mountain landscapes of the West Sayan north macroslope are the unique complex of habitats where the relict and mutant forms of Siberian pine were found. A wide amplitude of absolute heights (500-1800 m a.s.l.) in Tanzibey forestry causes a typological variety of forests grouped in 4 altitudinal belt complexes (ABC):

- light coniferous small-leaved subtaiga ABC. Detached groups of Pinus sibirica regeneration appear due to nutcracker (Nucifraga caryocatactes) activity and disappear owing to regular fires. P. sibirica produces 300-800 seedlings per hectare in a wide spectrum of habitats;

- low mountain chern ABC with aspen, Siberian pine and fir. It is the ecological optimum of P. sibirica. Outside the sites with large herbs and ferns the P. sibirica regeneration is more successful (1000-1200 seedlings per hectare);

- middle mountain-taiga ABC with Siberian pine and fir. The regeneration process is more stable in all series, and the extensive spreading of hypnum mosses favours this process. The quantity of P. sibirica regeneration is close to 800-1200 seedlings per hectare;

- high mountain subalpine open woodlands with Siberian pine and fir. The germination of P. sibirica from nuts carried by nutcracker from the lower belts is sufficiently successful, but its further growth depends on many other factors like short vegetation period, thick snow cover and extreme soil moisture.

The forest inventory data are confirmed by long-termed accounting data of P. sibirica new generation on the permanent test plots in 2009-2011. In all of 9 test plots placed in chern ABC and on the border of chern and sub-taiga ABC the regeneration of Siberian pine is poor (100-500 seedlings/ha) regardless of tree structure (it presents different combinations of Siberian pine, fir and aspen). It is caused by competition with large herbs and ferns, fir regeneration and mature trees. Only in fir forests with small-herbs and sedge cover the quantity of recently appearing P. sibirica new generation is higher (a little less than 3500 seedlings/ha). The main cause of this phenomenon is the nutcracker activity and raised nut productivity on the nearest sites with the absence of fern and large herbs competition.

© 2012 Organizing Committee