Abstract
Global climatic changes have been observed for all natural biomes, with the greatest impact in the permafrost zone. The short series of direct observations of air temperature and precipitation from meteorological stations for this territory make it difficult to use them in studies of the impact of climate change on forest and forest-tundra ecosystems, but only longer series of gridded data expand the temporal-spatial resolution of this analysis. We compared local and gridded air temperature, precipitation and vapor pressure deficit (VPD) data, analyzed the trends of their changes over the last century for three sites in the permafrost zone (YAK and TAY in Russia, and CAN in Canada), and estimated the effect of their variability on oxygen isotopes in the tree-ring cellulose (δ18Ocell) of three different species (Larix cajanderi Mayr, Larix gmelinii Rupr. Rupr and Piceaglauca (Moench) Voss). Climate trend analysis showed strong changes after the 1980s, and even more pronounced from 2000 to 2020. We revealed that δ18Ocell-YAK showed mixed signals of the July temperature (r = 0.49; p = 0.001), precipitation (r = −0.37; p = 0.02) and vapor pressure deficit (VPD) (r = 0.31; p = 0.02), while δ18Ocell-CAN captured longer March–May (r = 0.37, p = 0.001) and July (r = 0.32, p < 0.05) temperature signals as well as spring VPD (r = 0.54, p = 0.001). The δ18Ocell-TAY showed a significant correlation with air temperature in July (r = 0.23, p = 0.04) and VPD in March (r = −0.26, p = 0.03). The obtained eco-hydrological relationships indicate the importance of temperature and moisture to varying degrees, which can be explained by site- and species-specific differences.
Highlights
Drastic temperature and precipitation changes over the past few decades have led to massive wildfires [1,2,3] and permafrost degradation [4] in boreal forests [5]
Air temperature and precipitation data obtained from the Chokurdakh (YAK), Khatanga (TAY) and Inuvik (CAN) local weather stations were correlated versus gridded climate data
We revealed that the average air temperature increased significantly mainly over recent years, staring from the 1980s (Figure 1, red line), which is confirmed by significant trends (p < 0.0001) for the period 1980–2000 for the mean annual (January-December), winter (December of the previous hydrological year to January and February of the current one—DJF), spring (March, April, May—MAM), and summer (June, July, August—JJA) temperatures for the Siberian subarctic (Figure 1, Table S2)
Summary
Drastic temperature and precipitation changes over the past few decades have led to massive wildfires [1,2,3] and permafrost degradation [4] in boreal forests [5]. Conifer trees growing in circumpolar regions are highly sensitive to rapid climatic changes due to their location at high latitudes, where air temperature is a limiting factor and has a strong impact on tree growth [6,7,8,9,10,11]. The major advantage of studying conifer trees from circumpolar regions is their remoteness, allowing one to investigate tree responses to environmental changes without anthropogenic disturbances. A major disadvantage is the scarcity of local weather stations in the study regions. Gridded large-scale climate data (CRU TS 4.04 land, KNMI climexp.knmi.nl, Accessed on 30 August 2021) can help in filling the gaps in the observed climate data and can improve the quality of climate reconstructions for remote regions. It remains unclear as to which weather stations should be included when obtaining gridded data and if these data have gaps or missing values, and how valuable they can be in the selected nets for climate interpretation
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