Kinetic and Thermodynamic Characteristics of Soil Enzymes in Pure and Mixed Forest Samples on the Loess Plateau of China

ABSTRACT Background Soil enzymes are key to predicting nutrient availability and forest fertility. Aims We aimed to evaluate the influence of forest type on the kinetic and thermodynamic characteristics of soil enzymes. Methods Soils were sampled at 0–10 and 10–20 cm depth from two pure forests ( Pinus tabulaeformis [PTF] and Quercus acutissima [QAF]) and a mixed forest of PTF and QAF (MF) on the Chinese Loess Plateau. Kinetic parameters (maximum enzyme activity [ V max ], half‐saturation constant [ K m ], and enzyme efficiency [ K cat ]) and thermodynamic parameters (temperature coefficient [ Q 10 ] and activation energy [ E a ]) of β‐1,4‐glucosidase (BG), β‐1,4‐ N ‐acetylglucosaminidase (NAG), l ‐leucine aminopeptidase (LAP), and alkaline phosphatase (AP) were determined. Results Forest type exerted significant influence on soil enzyme kinetic parameters. The V max and K cat values of BG, NAG, and AP in PTF of 0–10 cm soil depth were 42.54% and 59.22%, 77.18% and 23.08%, and 62.82% and 58.21% higher than that in MF, respectively. The V max of AP and K cat of NAG in PTF of 10–20 cm depth were 34.61% and 39.90% higher than that in MF. The soil enzyme thermodynamic parameters were significantly influenced by forest type and soil depth. At 0–10 cm depth, low values of Q 10 – V max and Q 10 – K m of BG, Q 10 – V max and Q 10 – K cat of NAG, and E a of BG and NAG were found in PTF. At 10–20 cm depth, low values of Q 10 – V max , Q 10 – K cat , and E a of BG and NAG were found in MF. Conclusions PTF was more effective in promoting soil enzymatic reactions, especially in surface soil. MF improved subsoil enzyme thermal stability and reduced temperature sensitivity. The study showed that pure and mixed forests affect soil enzyme characteristics differently, with soil depth as a key factor.