Influence of environmental factors on the morphological variability of aspen (Populus tremula L.) in floodplain and ravine forests of the West Kazakhstan region

Abstract

 This study evaluates the influence of environmental factors on the morphological and morphometric variability of Populus tremula L. in the floodplain ravine forests of the West Kazakhstan region. The research compares three natural aspen populations that differ in hydrological regimes, soil characteristics,  levels of anthropogenic pressure. The main objective was to identify adaptive morphological changes occurring under the combined effects of natural - climatic  technogenic environmental factors.

Field methods included measuring tree height, stem diameter at breast height (DBH), and crown parameters using a Suunto PM-5/1250 hypsometer and a forestry measuring tape. Leaf morphology was assessed using 20 - 30 representative leaf blades per tree, measured with a caliper (0.1 mm accuracy). Examined traits included shape, color, thickness of the leaf blade, petiole length, shoot structure, and bark condition. Herbarium specimens collected between 1927 and 2015 were analyzed to identify long-term morphological variation. Forest inventory data were used to determine age structure, stand volume, and stand dynamics.

The results showed that the population growing in ravine forest conditions maintains stable morphological characteristics typical of P. tremula, indicating favorable ecological conditions. In contrast, the second and third populations - located near the Karachaganak oil and gas condensate complex and the “Karachaganak - Atyrau” pipeline - demonstrated distinct morphological deviations. These included changes in leaf shape and color, increased leaf blade thickness, deformation of young shoots, and signs of pathogen-induced damage. Such deviations were found to correlate with increasing levels of anthropogenic impact.

Overall, the study confirms that Populus tremula L. exhibits high sensitivity to environmental gradients and serves as a reliable bioindicator for assessing the ecological condition of forest ecosystems in Western Kazakhstan.

Keywords: Populus tremula L., morphometric traits, ecological - cenotic conditions, adaptive plant responses, herbarium studies, forest inventory indicators, forest ecosystems of West Kazakhstan.