Response of Non-Structural Carbohydrates in Picea crassifolia to Elevation Gradients in the Qilian Mountains

Non-structural carbohydrates (NSC) are important components of plant photosynthetic carbon products and play key roles in carbon allocation and stress adaptation. We hypothesized that elevational gradients and organ functional differences jointly shape NSC concentrations in Picea crassifolia. We measured NSC, soluble sugar, and starch in leaves, trunks, and fine roots at three elevations (2500, 2900, 3300 m) in the Qilian Mountains. NSC and its components decreased with elevation in all organs, while the soluble sugar-to-starch ratio increased. NSC concentrations ranked leaves > fine roots > trunks, and the relative distribution of starch shifted from trunks at low elevations to leaves at high elevations. Climate and soil jointly explained 79.70% of NSC variation, with the elevational-climate gradient being the dominant driver. These findings enhance understanding of carbon allocation strategies in alpine coniferous forests.