Soil ecoenzymatic stoichiometric characteristics in pure and mixed plantations of tree species with different mycorrhizal types, as affected by roots, hyphae, and microorganisms

Compared with -R-H, +R+H significantly increased TP, AP, MBC, MBN, and MBP by 13.6%, 2.7%, 58.2%, 16.4%, and 42.5%, respectively; -R+H significantly increased MBC and MBN by 16.7% and 24.0%, respectively. 2) The activities of carbon-acquiring enzymes (cellobiohydrolase and β-1,4-glucosidase), nitrogen‑acquiring enzymes (β-1,4‑N-acetylglucosaminidase and leucine aminopeptidase), and phosphorus‑acquiring enzyme (acid phosphatase) among stand types all followed the order ML–CH > CH > ML > CH, with ML-CH significantly higher than the other stand types; CH exhibited significantly higher nitrogen‑ and phosphorus‑acquiring enzyme activities than ML.

Among microcosm treatments, enzyme activities followed the order +R+H > -R+H > -R-H, with +R+H significantly higher than -R+H and -R-H. 3) In -R+H and +R+H treatments, C:PEnzyme and N:PEnzyme in ML, CH and ML-CH were significantly lower than those in CL, and soil microbial metabolism was limited by phosphorus in all stands. FR, TP, AP, C:NSoil and qMBN were the main factors affecting enzyme activities, and C:NSoil was the main factor affecting soil enzyme stoichiometric ratios.

In conclusion, broadleaf pure forests and mixed forests can effectively increase soil nutrient contents and enzyme activities, and the combined effects of roots and hyphae can enhance soil phosphorus availability. The phosphorus cycling enzyme activity of EcM species (Castanopsis hystrix) was higher than that of AM species (Mytilaria laosensis), The mixed plantation with complementary mycorrhizal types exhibited the best enhancement effects on both nitrogen and phosphorus cycling enzyme activities.

The soil in the study area is phosphorus‑deficient, and appropriate exogenous phosphorus supplementation is recommended in subsequent management to alleviate microbial phosphorus limitation, promote effective nutrient cycling, and thereby maintain and enhance plantation productivity.