In the conditions of global warming, permafrost thawing is one of the largest natural phenomena that will have a significant impact not only on the infrastructure of the subarctic and Arctic, but also on the ecosystems of northern forests. Scientists have shown that water from permafrost can help trees adapt to changing conditions, including droughts. The results of the study were published in the journal Science of The Total Environment.

Permafrost is a layer of soil that remains frozen (below 0°C) for two to thousands of years. It directly impacts the functioning and productivity of most boreal forests, the largest terrestrial biome on Earth. In recent decades, the boreal forest zone has experienced significant warming, and extreme weather events in this area are becoming more frequent. Understanding the response of permafrost to these changes is important for predicting the state of forests under the conditions of global warming.

Researchers from the Federal Research Center "Krasnoyarsk Science Center SB RAS", together with colleagues from the UK, the Czech Republic and Switzerland, have found that thawing permafrost can mitigate drought stress caused by warming in trees of boreal forests. Experts have studied the width of tree rings and the composition of stable carbon and oxygen isotopes of Gmelin larch trees in six plots within the zone of continuous permafrost soils in the northern taiga of Central Siberia.

The growth of trees in the permafrost zone is primarily affected by air and soil temperatures, as well as by the moisture content in the seasonally thawing layer and upper layers of permafrost. The research results have shown that thawing of deeper soil stimulates radial tree growth. Based on the isotopic composition of tree rings, scientists were able to establish that trees cope with moisture deficiency in dry summer conditions by obtaining water from the thawing frozen layer of soil. Thus, the role of permafrost as a source of water in warm and dry summers increases.

The specialists note that future warming may lead to long-term drying out of the surface layers of soil in the zone of continuous permafrost. Under these conditions, trees, due to their developed root system, can gain access to deeper horizons of thawing frozen soil, which can support the growth of boreal forest trees in a changing climate.

“Identification of the role of the upper layers of permafrost soils for the water supply of trees during dry periods is the most important result, which makes it possible to reveal the mechanisms of adaptation of trees to changing environmental conditions. A detailed understanding of this phenomenon will provide an opportunity to refine the strategy for preserving forest ecosystems of the permafrost zone in the context of global warming,” said Alexander Kirdyanov, Doctor of Biological Sciences, leading researcher at the V.N. Sukachev Institute of Forest SB RAS.
The work was supported by the Russian Science Foundation (project No. 22-14-00048).

The study also involved specialists from the Siberian Federal University, the University of Cambridge, the Swiss Federal Institute of Forest, Snow and Landscape, the Masaryk University (Czech Republic), and the Institute for Global Change Research of the Czech Academy of Sciences.