Climate-Driven Productivity Responses and Implications for Genetic Adaptation and Breeding of Boreal Trees in Kazakhstan

Abstract

Kazakhstan’s boreal and forest-steppe forests form the southern ecotonal edge of the West Siberian taiga, where relatively small changes in heat and moisture can trigger disproportionate impacts on tree growth, mortality, and regeneration. Although forests cover only ~4% of Kazakhstan, they provide critical ecosystem services: stabilizing hydrological regimes, buffering microclimates, protecting agricultural lands from wind and water erosion, and supporting landscape resilience in drought-prone regions. Sustainable forest management therefore requires quantitative monitoring of forest productivity and carbon balance, not only descriptive assessments, to support both climate policy and adaptive silviculture. Over recent decades, Kazakhstan has experienced persistent warming and increasing hydroclimatic stress. Rising temperatures can lengthen the growing season and increase potential productivity, but warming also elevates atmospheric water demand and Vapor-Pressure Deficit (VPD), intensifying drought stress and increasing the likelihood of productivity collapse during extreme years. Globally, such “hotter droughts” have been linked to declining growth and higher tree mortality risk, especially in climate-sensitive ecotones. For boreal systems, drought effects may offset warming-driven gains and destabilize the net carbon sink. Productivity and carbon dynamics are also central to genetic adaptation and breeding. Tree populations often exhibit genetically structured variation in phenology, hydraulic traits, and growth responses to climate, producing distinct reaction norms across climatic gradients. Under climate change, selective pressures may shift from cold tolerance toward drought and heat tolerance, implying that breeding programs and seed-origin zoning must be updated to maintain forest performance and reduce maladaptation risk. However, for Kazakhstan, long-term quantitative relationships among climate drivers (temperature, precipitation, SPEI, VPD), productivity (NDVI, NPP, NEP), carbon pools (AGC, SoilC), and breeding-relevant adaptation patterns remain insufficiently established. This study addresses that gap by integrating multi-decadal climate datasets with satellite observations and carbon-cycle modelling to evaluate climate-driven productivity responses across five boreal regions of Kazakhstan (Akmola, Kostanay, North Kazakhstan, Pavlodar, East Kazakhstan) during 1990–2024. We test the expectation that (i) productivity shows an overall increasing trend under warming but (ii) drought years trigger strong negative anomalies in NPP and NEP, potentially switching forests from sink to source, and (iii) regional contrasts in climate elasticities delineate functional adaptive–breeding zones relevant for provenance selection and assisted gene flow. Aim. To quantify climate-driven changes in productivity and carbon balance of Kazakhstan’s boreal forests (1990–2024) and interpret them in the context of genetic adaptation and breeding priorities of dominant tree species.