Larch growth across thermal and moisture gradients in the Siberian Mountains

Climate-driven changes in the thermal and moisture regimes may variously influence different tree species growth and ranges.We hypothesize that drought resistant Siberian larch(Larix sibirica Ledeb.)and precipitation-sensitive Siberian pine(Pinus sibirica Du Tour)responded differently to climate change along the elevational thermal and precipitation gradients.We studied the influence of air temperature,precipitation,soil moisture,and atmospheric drought(indicated by the drought index SPEI)on larch and pine growth along the southward megaslope of the West Sayan Ridge.We found that since 2000 climate change resulted in increasing larch and pine radial growth index(GI)(c.1.5–3times)within treeline(2000–2300 m)and timberline(1900–2000 m)ecotones,i.e.within high precipitation zones.Within the forest-steppe ecotone(1100–1200 m)in which L.sibirica is the only species,larch GI stagnated or even decreased.The total forested area increased since 2000 up to+50%in the high elevations,whereas in the low elevations(<1400 m)area changes were negligible.Within treeline and timberline,trees’GI was stimulated by summer temperature.Meanwhile,temperature increase in early spring reduces GI due to living tissue activation followed by tissue damage by desiccation.Within forest-steppe,larch radial growth was mostly dependent on soil moisture.Warming shifted dependence on moisture to the early dates of the growing period.Acute droughts decreased GI within forest-steppe as well as within treeline,whereas the drought influence on both species within highlands was insignificant.Within forest-steppe seedlings establishment was poor,whereas it was successful within treeline and timberline.Current climate change leads to stagnation or even decrease in Larix sibirica growth in the southern lowland habitat.In combination with poor seedlings establishment,reduced growth threatens the transformation of open lowland forests into forest-steppe and steppe communities.Meanwhile,in the highlands warming facilitated the growth of Siberian larch and pine and the increase of forested area.

Fuel characteristics, loads and consumption in Scots pine forests of central Siberia

Forest fuel investigations in central and southern Siberian taiga of Scots pine forest stands dominated by lichen and feather moss ground vegetation cover revealed that total aboveground biomass varied from 13.1 to 21.0 kg/m 2.Stand biomass was higher in plots in the southern taiga,while ground fuel loads were higher in the central taiga.We developed equations for fuel biomass(both aerial and ground)that could be applicable to similar pine forest sites of Central Siberia.Fuel loading variability found among plots is related to the impact and recovery time since the last wildfi re and the mosaic distribution of living vegetation.Fuel consumption due to surface fi res of low to high-intensities ranged from 0.95 to 3.08 kg/m 2,that is,18–74%from prefi re values.The total amount of fuels available to burn in case of fi re was up to 4.5–6.5 kg/m 2.Moisture content of fuels(litter,lichen,feather moss)was related to weather conditions characterized by the Russian Fire Danger Index(PV-1)and FWI code of the Canadian Forest Fire Weather Index System.The data obtained provide a strong foundation for understanding and modeling fi re behavior,emissions,and fi re eff ects on ecosystem processes and carbon stocks and could be used to improve existing global and regional models that incorporate biomass and fuel characteristics.

Spatial analysis of vegetation cover response to climate trends in Khakassia(South Siberia)

An analysis of the changes in vegetation cover on the territory of the Republic of Khakassia in 2000–2021 due to climatic trends was carried out based on the MODIS data.The changes in vegetation cover were estimated based on trends in Normalized Difference Vegetation Index(NDVI)and Enhanced Vegetation Index(EVI).In general,in the 21st century,an increase in the biomass of vegetation cover is observed.Positive trends were observed in 16%–22%of the territory,and negative only in 1%–3%.For about 20%of the analyzed territory,a significant influence of climate on the changes in vegetation cover was revealed.The most pronounced negative impact on vegetation cover was caused by summer air and soil temperatures,spring temperature,and summer winds,and the positive impact was caused by summer precipitation and soil moisture.The response of the vegetation cover to climate was non-uniform concerning the topography.Thus,a significant correlation with the amount of precipitation was observed for~20%–35%of vegetation growing below 600 m above sea level and for less than 5%above this elevation.The negative effect of summer temperatures on plants prevailed mainly at an elevation below~1400 m above sea level.Projected climate change is likely to lead to significant degradation of vegetation in the steppe and foreststeppe in Khakassia in the coming decades.

Siberian silkmoth outbreaks surpassed geoclimatic barrier in Siberian Mountains

Siberian silkmoth(SSM,Dendrolimus sibiricus Tschetv.)is the most important defoliator of Siberian pine(Pinus sibirica Du Tour)and fir(Abies sibirica Ledeb.)stands.Warming-induced SSM outbreaks are one of the major driving factors of successions within the taiga zone.It is suggested that climate change impacted the SSM range and life cycle.We analyzed the migration of alpine and northerly SSM outbreak boundaries in Siberia and the impact of the climate variables and topography on the outbreak dynamics.We used time-series scenes(multispectral data,and vegetation indexes EVI and NDII)in combination with field studies,climate variables,and GIS techniques.We found that SSM outbreaks in the area of alpine boundary shifted about 370 m uphill since the mid of 1950.The outbreak onset was promoted by increased dryness and active temperatures and decreased root zone moisture content in the spring-early summer period.The terrain topography strongly affected SSM outbreak onset and dynamics.Initially,the outbreak was located at the middle elevations on the gentle concave southeastern slopes,which are the favorable insect habitats between outbreaks.Then the outbreak expanded uphill and downhill,to steeper slopes,and both concave and convex terrains.Alongside with elevation range expansion,SSM surpassed its northern historical outbreak boundary:the potential outbreaks’boundary moved about 300 km northward.Climate warming contributes to SSM migration into former outbreak free conifer stands located in highlands and at northern latitudes.

Alpine ecotone in the Siberian Mountains:vegetation response to warming

Birch(Betula tortuosa)is one of the treeline forming species within the Siberian Mountains.We analysed the area dynamics of birch stands and the upslope climb of birch treeline based on the Landsat time series scenes and on-ground data.We found that since the warming onset(1970th)birch area increased by 10%,birch stands and treeline boundary were moving upslope with a rate of 1.4 m/yr and 4.0 m/yr.Birch upslope shift correlated with air temperatures at the beginning(May-June)and the end(August-October)of the growth period.Meanwhile,no correlation was found between birch upslope migration and precipitation.Winds negatively influenced both birch area growth and birch upslope climb during spring,fall,and wintertime.In the windy habitats,birch,together with larch and Siberian pine,formed clusters(hedges)which mitigated the influence of adverse winds.These clusters are the adaptive pattern for trees’upslope climb within windward slopes.The other adaptation to the harsh alpine ecotone habitat is non-leaf(bark)photosynthesis which supports tree survival.Thereby,Betula tortuosa upslope climb depends on the wind impact and warming in spring and fall that extended growth period.With ongoing warming and observed wind speed decrease on the background of sufficient precipitation,it is expected to further birch advance into alpine tundra in the Siberian Mountains.

Warming hiatus-and evergreen conifers in Altay-Sayan Region,Siberia

"Warming hiatus" occurred in the AltaySayan Mountain Region, Siberia in c. 1997–2014. We analyzed evergreen conifer(EGC) stands area(satellite data) and trees(Siberian pine, Pinus sibirica Du Tour, Siberian fir, Abies sibirica Ledeb.) growth increment(dendrochronology data) response to climate variables before and during the hiatus. During the hiatus, EGC area increased in the highlands(>1000 m)(+30%), whereas at low and middle elevations(<1000 m. a.s.l.) the EGC area decreased(-7%). The EGC area increase was observed on the rain-ward northwest slopes mainly. In highlands, EGC area increase mainly correlated with summer air temperature, whereas at low and middle elevations EGC area decrease correlated with drought index SPEI and vapor pressure deficit(VPD). EGC mortality(fir and Siberian pine) in lowland was caused by the synergy of water stress(inciting factor) and barkbeetle attacks(contributing factor). Tree growth increment(GI) dynamics differs with respect to elevation. At high elevation(1700 m) GI permanently increased since warming onset, whereas at the middle(900 m) and low elevations(450 m) GI increased until c. 1983 yr. with followed depression. That GI "breakpoint" occurred about a decade before hiatus onset. In spite of growth depression, during hiatus GI was higher than that in pre-warming period. At high elevation, GI positively responded to elevated June temperatures and negatively to moisture increase(precipitation, root zone moisture content, VPD, and SPEI). At low elevation GI negatively responded to June temperatures and positively to moisture increase. For both, low and high elevation, these patterns persisted throughout the study period(1967–2014). On the contrary, at middle elevations GI dependence on climate variables switch after breakpoint year(1983). Before breakpoint, June air temperature(positive correlation) and moisture(negative correlations) controlled GI. Further temperature increase leads GI depression and switched correlation signs to opposite(from positive to negative with temperature, and from negative to positive with moisture variables).

Infl uence of fire on soil temperatures of pine forests of the middle taiga,central Siberia,Russia

Temperatures of sandy podzols of middle taiga pine forests with moss and lichen ground cover were analyzed which had been exposed to ground fires of low to medium intensity.In general,temperatures in lichen and moss plots of the pine forests under study,are close to each similar,but in the first year after a fire a noticeable contrast was observed.The reasons are an increase in the amplitude of daily temperatures on the soil surface and stronger heating of upper mineral layers.Temperatures in the mineral layer with depths up to 30 cm depend on the thickness of the forest fl oor.Analysis of the results show that the duration of postfire effects in pine forests with sandy podzols is determined by a number of factors:the intensity of the fire,the degree of erosion of the ground cover and litter,and the recovery rate of these components.

Erratum to:Siberian silkmoth outbreaks surpassed geoclimatic barrier in Siberian Mountains

Aim&Scope:Journal of Mountain Science(JMS)is devoted to mountains and their surrounding lowlands-ecoregions of particular global importance,with a particular emphasis on the important highlands/mountains in the world.JMS mainly publishes academic and technical papers concerning environmental changes and sustainable development in mountain areas under natural conditions or/and with the influence of human activities.It also accepts book reviews,commentary,and reports on mountain research and introductions to mountain research organizations.