Condition of pine and larch forests adjacent to the reservoir within the Sayano-Shushensky Nature Reserve

Abstract

Forests cover 60% of the Sayano-Shushensky Nature Reserve, 48% of which are larch and pine stands. The purpose of the research was to assess condition of Larix sibirica Ledeb. and Pinus sylvestris L. forests adjacent to the reservoir within the reserve. We conducted forest pathological inspection (for each species on four research plots), an integral assessment of the stands condition, macroscopic diagnostics and disease manifestations indicators estimation and studied model trees affected by xylophagous insects. Studied stands ranged from sustainable to ones with disturbed sustainability and their health status ranged from healthy to varying degrees of weakening. One of the main factors weakening forest stands were ground fires, leading to increased mortality of small-diameter trees that are less resistant to heat stress (most typical of P. sylvestris). Medium and large diameter trees post-fire mortality in L. sibirica forest stands was due to the Zeiraphera griseana feeding, and in relatively flat coastal areas due to repeating flooding. The presence of groups of trees dying from the top down were observed in pine forests growing on thin soils most likely due to an imbalance between the amount of required and available soil moisture. Diseases were not common and did not have a significant impact on the forest stands. Potentially harmful are the following diseases: in larch forests - European larch canker (pathogen - Lachnellula willkommii), in pine forests - Scots pine blister rust (pathogen - Cronartium pini). Xylophagous insects (dominated by Ips acuminatus) had an increased abundance and fed on dying trees in pine forests weakened after fires.