Soil enzyme activities and ecological stoichiometry characteristics of Lactarius akahatsu shiroes soil in contrasting forest ecosystems

To explore the regulatory effect of Lactarius akahatsu on soil enzyme activities and ecological stoichiometry characteristics in three different forest stands, and to clarify the effect of ectomycorrhizal fungi on forest soil nutrient cycling.

The Lactarius akahatsu shiroes soil and adjacent control soil were collected from Pinus massoniana pure forest, Cyclobalanopsis glauca pure forest and Pinus massoniana -Cyclobalanopsis glauca mixed forest. Soil physicochemical properties, including organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), acid available phosphorus (AAP), ammonium nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃^--N), and pH value were analyzed. Enzyme activities related to carbon, nitrogen, and phosphorus cycling, including β-glucosidase (BG), N-acetyl-glucosaminidase (NAG), leucine aminopeptidase (LAP), urease (URE), acid phosphatase (AP), peroxidase (PER) were measured. The enzyme ecological stoichiometric ratio (E_C∶N、E_C∶P、E_N∶P) and vector analysis (V_A、V_L) were calculated. Principal component analysis and redundancy analysis were employed to identify key drivers of enzymatic variation.

Compared to control soils, the contents of SOC, TN, TP, NH₄⁺-N and NO₃^--N in Lactarius akahatsu shiroes soil in the three stands were significantly higher than control soil. Lactarius akahatsu shiroes soil in all three stands demonstrated increased activities of BG, NAG, LAP, and URE, while significantly reduced PER activity, though AP activity remained statistically invariant, with the most pronounced variation observed in Pinus massoniana -Cyclobalanopsis glauca mixed forest. The results of soil enzyme stoichiometry revealed that the E_C∶P and E_N∶P ratios in Lactarius akahatsu shiroes soil in the three stands significantly increased, with the highest values in Cyclobalanopsis glauca pure forest. In the Pinus massoniana-Cyclobalanopsis glauca mixed forest, the E_C∶N ratio in shiroes soil decreased significantly, while the E_C∶P and E_N∶P ratios increased significantly. All three stands exhibited carbon and phosphorus limitations, with the Cyclobalanopsis glauca pure forest experiencing the most severe phosphorus limitation. Lactarius akahatsu was more effective at relieving soil phosphorus limitation in the Pinus massoniana-Cyclobalanopsis glauca mixed forest. Redundancy analysis and vector analysis identified soil C∶N ratio and NH₄⁺-N as critical regulatory factors affecting soil enzyme activities, with URE serving as a key indicator for distinguishing soil properties among the three forest stands.

Lactarius akahatsu altered soil physicochemical properties, enzyme activities and ecological stoichiometry characteristics in three forest stands, it significantly enhanced soil nutrient accumulation and enzyme activities in the Pinus massoniana -Cyclobalanopsis glauca mixed forest, and effectively alleviated soil phosphorus limitation, which could provide a reference for mycorrhizal management of plantations.