关键词: 根系功能性状, 落叶松, 变异特征, 纬度梯度

Abstract: Aims Latitudinal variation induces changes in climate and soil properties, yet whether closely related tree species exhibit similar trends in their root functional traits across latitudes remains unclear. Methods This study took the Larix olgensis and the L. gmelinii at four latitudinal gradients (43°N - 50°N) as the research objects. Root anatomical traits (cortex thickness, stele diameter, root stele diameter to root diameter ratio) and morphological traits (mean root diameter, specific root length, specific surface area, and tissue density) were measured. These trait data were combined with soil nutrient and climate data to analyze root responses to soil and environmental drivers. Important findings (1) Only L. olgensis root anatomical traits responded to latitudinal changes, with a significant decrease in the stele diameter of first-order roots and a significant increase in the stele diameter of fifth-order roots as latitude increased (P < 0.05).(2) The root morphological traits of the two species also responded differently to latitude. All measured morphological traits of L. gmelinii increased with latitude; for instance, the specific surface area of first-order roots increased from 237.2 cm²·g⁻¹ to 298.9 cm²·g⁻¹. In contrast, L. olgensis root morphological traits showed no consistent pattern. (3) Root functional traits of both species were strongly influenced by root order (P < 0.01), with the increase of root order, the cortex thickness, specific root length, specific surface area and tissue density of the two larch root systems decreased, while the diameter of the stele, the stele diameter to root diameter ratio and the average diameter increased.(4) In lower latitude regions, the root functional traits of both larch species were influenced by climatic factors, while in higher latitude regions, they were primarily affected by soil nutrients.(5) The collaboration gradient (PCA1) of L. gmelinii showed a highly significant positive correlation with soil pH, whereas the collaboration gradient (PCA1) and conservation gradient (PCA2) of L. olgensis exhibited highly significant negative correlations with soil pH. In conclusion, under the environmental gradient formed by latitude, the L. olgensis relies on the high plasticity of root functional traits to adapt to environmental changes, while the L. gmelinii depends on the stable symbiosis with mycorrhizal fungi. This difference demonstrates that closely related species may adapt to the same environment through different ecological strategies, which provides a scientific basis for understanding the interspecific adaptation mechanisms of plants and their responses to climate change.

Key words: root functional traits, Larix, variation characteristics, latitudinal gradient