Understory Vegetation Regulated the Soil Stoichiometry in Cold-Temperate Larch Forests

Carbon (C), nitrogen (N), and phosphorus (P) are vital nutrients in the soil, exerting a profound influence on the primary productivity of ecosystems. However, our understanding of how the understory influences soil nutrients and their stoichiometry remains limited, especially in cold-temperate forests where the understory plays a crucial role in mediating soil nutrient cycling. To elucidate the effect of understory vegetation on soil nutrients, three typical larch forests, namely Sphagnum-Bryum-Rhododendron tomentosum-Larix gmelinii forest (SLL), Rhododendron dauricum-Larix gmelinii forest (RL), and Rhododendron tomentosum-Larix gmelinii forest (LL), were selected in the typical cold-temperate region of northeast China to determine the soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP) contents, and their stoichiometric characteristics in 0-100 cm soil depth. The results revealed the following: (1) Significant differences in soil nutrient and its stoichiometry existed among the three different forest types (p < 0.001), with the SLL displaying the highest mean SOC, TN, and TP contents, as well as soil C:N, C:P, and N:P ratios, whereas the RL exhibited the lowest values (p < 0.05). (2) Across the 0-100 cm soil profile, the soil nutrient content and stoichiometry showed decreasing trends with soil depth, with significant differences among the soil layers. (3) Variations in soil stoichiometry were significantly correlated with soil bulk density, pH, soil temperature, soil water content, total porosity, and capillary porosity (p < 0.05). This study underscores the necessity of further consideration of the impact of understory vegetation in future research on soil stoichiometry in forest ecosystems.