Abies faxoniana Rehd. and Picea asperata Mast. in the subalpine region of Chagangliang, Gansu Province, were taken as research objects, and the C, N, P, and K contents in different organs, litter, and soil of the two coniferous forests were measured to investigate their stoichiometric characteristics and their interactions, aiming to elucidate the mechanisms underlying their ecological adaptations.

Using community ecology methods, three 50 m×50 m fixed plots were established in each forest type. C, N, P, and K contents in different organs, litter, and soil layers were analyzed, and their correlations were examined.

1) The organic C, total N, total P, and total K contents in fir leaves were higher than those in the roots and stems. For spruce, the organic C content was highest in the leaves, while the total N, total P, and total K contents were highest in the stems; 2) In both coniferous forests, the organic C, total N, and total P contents were highest in the surface soil layer (0-10 cm) and gradually decreased with increasing soil depth. The total K content, however, showed little variation across different soil layers. Among the forest components, woody debris had the lowest organic C content but the highest N content, whereas mosses exhibited the highest C content. In litter, the total N and total P contents increased as decomposition progressed. The C∶N ratio was highest in the undecomposed litter layer and lowest in CWD. Mosses had the highest C∶P ratio, followed by CWD, while the undecomposed litter layer (K₁) had the smallest C∶K ratio, and CWD showed the largest C∶K ratio; 3) In P. asperata forests, soil organic C was significantly positively correlated with soil N and P (P≤0.01), soil N with P (P≤0.05), and soil P with K (P≤0.05). In A. faxoniana forests, soil organic C was positively correlated with soil P (P≤0.01) but negatively correlated with leaf P, K, and litter N and P (P≤0.05). Soil N and litter N were significantly negatively correlated (P≤0.01), while soil P and K showed a significant positive correlation (P≤0.01).

The growth of P. asperata is constrained by limitations in N, P, and K availability, coupled with factors such as slow litter decomposition and low accumulation of organic carbon in its leaves. In contrast, A. faxoniana exhibits higher organic carbon accumulation in its leaves and thrives in environments with more abundant N, P, and K. Therefore, in future vegetation restoration efforts, prioritizing the establishment of A. faxoniana forests is recommended. This approach will better support the region’s vegetation recovery and contribute to maintaining water conservation functions and overall ecosystem stability.

Three kinds of secondary forests, including Quercus wutaishansea Mary, Betula albosinensis Burk and Betula utilis D. Don were studied with measurement of the content and stoichiometric of C, N and P in the leaf-litter-soil continuum to analyzed the response of plants to soil environmental changes and nutrient use strategies by nutrient use efficiency and reabsorption efficiency.

The article adopted community ecology research methods and three samples with the area of 50 m*50 m in the study fixed sample plot was selected to measure the C, N, and P contents of leaves, litter, and soil. Nutrient utilization efficiency and reabsorption efficiency were used to analyze the response of plants to soil environmental changes and nutrient utilization strategies.

1) The contents of C, N and P in the three secondary forests were leaf > litter > soil. The content of organic C and P in leaves was higher than the national average of plant leaves, the content of N was slightly lower than the national average, and the content of organic C in soil was higher than the national average. The content of organic C, N and P in leaf was significantly higher than that in litter and soil (P < 0.05), and the content of organic C, N and P in litter was significantly higher than that in soil (P < 0.05). The value of N/P was between 11.21 and 12.98 in the leaf, and the value of C/N was between 30.63 and 36.75 in the litter, showing that plant growth and microbial decomposition of litter were limited by N; The value of N/P ranged from 1.84 to 2.21 in the soil. This value of Q. wutaishansea Mary was the smallest and the value of Be. utilis D. Don was the largest. The N and P content of B. utilis D. Don were significantly higher than those of the other two species (P < 0.05). 2) The internal steady state of N content in leaves of B. utilis D. Don was weak. The content of N in leaves of Q. wutaishansea Mary and B. albosinensis Burk had a high internal steady state. The content of P in three secondary forests had a high internal steady state. Plants could maintain P balance under the limit of low P in soil. The content of restrictive nutrient elements in plants was relatively stable, and the response to environmental changes was relatively stable. The reabsorption rate of plant leaves to N and P was B. albosinensis Burk > Q. wutaishansea Mary > B. utilis D. Don, and the N absorption rate was greater than P.

The growth and litter decomposition of the above three secondary forests are obviously restricted by N, and the soil P content is low, N and P were the main factor limiting the growth of three secondary forests in Bailongjiang. The results are intended to provide scientific basis for the restoration and succession of ecological functions of secondary forests in Bailongjiang, southern Gansu Province.