Objective To explore the soil quality under the four forest types (Larix kaempferi, Quercus mongolica+Larix kaempferi, Pinus densiflora, and Cunninghamia lanceolata) in Kunyushan National Nature Reserve.

Method Using the method of soil sampling combined with laboratory analysis, the physical and chemical properties and enzyme activities in different soil profiles under these forests were analyzed. The comprehensive analysis and evaluation of soil quality under different forest types were conducted by integrated soil quality index and principal component analysis.

Result The soil density of different forests increased with the increase of soil depth, and the total porosity decreased significantly (P < 0.05). The capillary porosity of L. kaempferi and P. densiflora were significantly reduced with the increase of soil depth, while the Q. mongolica+L. kaempferi and C. lanceolata were the opposite. The soil pH ranged from 4.13 to 5.07. The contents of soil organic matter, total nitrogen, total phosphorus, available nitrogen, and available potassium generally decreased with the increasing of soil depth, reflecting the surface aggregation characteristic of soil nutrient. On the whole, the soil total potassium content had no significant differences in different soil layers under four forest types (P < 0.05), the soil total potassium content in 20-40 cm and 40~60 cm layers of L. kaempferi were significantly higher than that of other forests. In addition to C. lanceolata, the soil available phosphorus content increased as soil depth increased. Except for soil invertase, the activity of other three soil enzyme decreased with the increase of soil depth. The soil quality index of these forests showed an order of L. kaempferi(0.792)> Q. mongolica+L. kaempferi (0.639) > C. lanceolata (0.353) > P. densiflora (0.267).

Conclusion Forest type has a significant impact on the physical and chemical properties at different levels of the soil layers. The soil quality status of different forest types is different, among them, the soil quality of L. kaempferi forest is the best, and the soil quality of P. densiflora forest is the worst.