Ninth International Conference on Permafrost ... - IARC Research

Influence of a Hydrothermal Soil Regime on the Radial Incrementof Larch and Pine in Central YakutiaAnatoly N. NikolaevPermafrost Institute, SB RAS, Yakutsk, RussiaIntroductionCentral Yakutia (eastern Siberia, Russia) has a dominantgrowth of larches, for it is situated on the area of permafrostdistribution. According to sustainable zoning of permafrostsoils of Yakutia, the observed area refers to the CentralYakutia taiga-alas provinces of permafrost and palesoils (Elovskaya & Konorovskiy 1978). It has severe,long, and low-snow winters and hot, short, and droughtysummers with significant insolation, low annual and wintertemperatures, high seasonal and daily amplitudes, and smallamount of deposits (Gavrilova 1973). Hydrothermal soilcondition is one of the important factors influencing treespecies growth. Long-term observation of the thermal soilregime in Central Yakutia has enabled the use of tree-ringchronology not only to reveal the relations between radialincrement, atmospheric temperature, and precipitation, butalso to analyze the influence of the hydrothermal soil regimeon growth and development of larch (Nikolaev & Fyodorov2004, Fyodorov et al. 2007).Materials and MethodsTree-ring chronology was examined at Spasskaya Padand Tyungyulyu, 25 km northwest and 45 km northeastfrom Yakutsk accordingly, in Central Yakutia, the scientificstations of Institute of Biological Cryolitozone Problems ofthe SB RAS.Due to the fact, that Spasskaya Pad site has areas oflarch and pine forests nearby, it was possible to carry outthe comparative analysis of the growth of these two speciesin conditions of permafrost. The forest areas are situated inthe Lena and Amga interfluve, which has one of the mostdroughty climates in Central Yakutia. The width of year ringswas measured with the LINTAB-III measuring instrument(Rinn 1996) in the laboratories of cryogenic landscapes ofMelnikov Permafrost Institute SB RAS. Dendroclimatologystandard research and the analysis technique were appliedduring dating and construction of tree-ring chronology(Vaganov et al. 1996, Shiyatov et al. 2000, Holmes 1983,1998, Methods … 1990, Rinn 1996). As a result, we got 2generalized tree-ring chronologies on the station SpasskayaPad, one of which is for larch kayander (Larix cajanderiMayr.) (SPPV) and the other for scotch pine (Pinus sylvestrisL.) (SPP12), which have been constructed. Other treeringchronologies on larch have been made up at stationTyungyulyu (TYNG).The comparative analysis of larch and pine growthdepending on external conditions at Spasskaya Pad stationwas carried out. It is known that these two species are thebasic forest-forming ones in Central Yakutia. Growth of treesis influenced not only by climatic factors such as atmospherictemperature and deposits, but also hydrothermal soilsconditions. Larch prefers moderately fertile and moderatelymoistened loamy ground, and grows worse in dry and crudeareas. In contrast to larch, pine grows on well aerated drysandy and sabulous soils.The soil temperature condition influence on radial treesincrement at Spasskaya Pad was analyzed. Here datafrom Pokrovsk meteorological stations were used. Thismeteorological station has more homogeneous data incomparison with data of the Yakutsk meteorological station,which has some series disorder as a result of its relocation in1930, 1952, and 1964 (USSR Climate Directory 1975) andsoil condition changes since 1989 caused by an increase insubterranean water.Results and DiscussionCorrelation analysis of larches tree-ring chronology fromSpasskaya Pad with soils temperature conditions at variousdepths shows that considerable correlation occurs duringwinter period. The higher the soil temperatures, the fastersoils warm up, which promotes timely beginning of active treegrowth in the vegetation beginning. Summer temperaturesdo not limit radial trees increment. During this period treeshave enough amount of heat for favorable growth.The similar analysis of pine radial increment has shown,that winter soil temperatures until the end of May have apositive relation to radial tree increments both at activelayer table and zero annual amplitudes of active layer at 20cm and 120 cm depth. A positive influence of temperatureoccurs in spring months in soil layers at 40–80 cm, whichleads to early soil thawing and the beginning of pine growthprocesses. However, unlike larch, a significant negativeinfluence of summer months’ temperature on pine growthoccurs at some depths. Probably this is due to a significantdeficiency of soil water content in drier soils, where heatscauses a drying up effect.The correlation analysis of larch tree-ring chronology atTyungyulyu with soil temperature conditions at differentdepths shows the presence of significant correlation; it is thesame for Spasskaya Pad at winter period. It is also revealed,that the soil’s summer temperature value has no significantinfluence on radial tree increments. In some cases, the soilhigh temperature means its negative relation with larchgrowth, which features for pine from Spasskaya Pad.Correlation analysis of tree-ring chronology for larch withsoil water content changes was carried out. Results showgood correlation occurs during the whole vegetative period.However, it is necessary to note that the most significantratios fall at the autumn period of the previous season. This225