Structure and dynamics of high-elevation mountain forest of Severo-Chuisky range (Altai Mountains)in conditions of climate change

The age structure of high altitudinal forests and fluctuations of tree radial increment werestudied on sample areas in the waterhead of the Aktru river on the northern macroslope in the central section of Severo-Chuisky Range(the Altai Mountains) at 2150-2350 m a.s.l. The study area falls into the Central Altai mountain hollow province of larch and dark coniferousforests. The main tasks were to study the age structure of the forests, to isolate generations, and to built and analyse tree ringwidth chronologies. At the upper forest line in the Aktru river valley the relatively closed stands are Siberian stone pine open woodlandslocated at 2350 m a.s.l. The pure old Siberian stone pine forests grow lower the line. The Siberian larch and Siberian stone pine forestslocate down to 2200 m a.s.l. The altitude decrease as low as 2150-2100 m a.s.l., the younger Siberian larch and Siberian stone pine forestsof the after-fire origin supersede the primary old forests. Within these altitudes the pure mid-aged Siberian larch forests grow. Theundergrowth is mainly the Siberian stone pine. The Siberian stone pine (515 years) and the Siberian larch (525 years) tree ring widthchronologies were built in order to assess the climate effect on the radial growth. The coefficients of correlation between the individualring rows of different sites are 0.35-0.72. The synchronism is 0.69. According to the ring chronologies, there are similar trends of increasingand decreasing growth in Siberian stone pine and larch trees. The radial growth correlates positively with the spring and summermonth temperatures (coefficients of correlation is 0.55 in May and 0.50 in June and July). The analysis of the age structure of theforests and fluctuation of the radial growth demonstrates that the increasing increment corresponds with the appearance of groups of thetrees of close ages in all the sites of the valley. The young Siberian stone pine generation can be produced under canopy and in standgaps from the undergrowth at the upper forest line and in the forests near it. Now there is intensive Siberian stone pine regeneration inboth the primary and after-fire Siberian stone pine forests and Siberian larch forests with Siberian stone pine trees. The close periods ofproducing the generations at and near the forest line indicate the significance of the climate change in the growth, development and distributionof these forests in Severo-Chuisky Range. Relief is also important for forest development because it is a natural barrier forstrong fires and has therefore an influence on conservation of the primary old Siberian stone pine forests with several generations.

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