Soil fertility quality evaluation of pure and mixed Larix principis-rupprechtii forests in Saihanba, Hebei Province of northern China

  Objective  In this study, soil quality index (SQI) was used to evaluate the effects of different mixed modes on soil fertility quality in Larix principis-rupprechtii forests, in order to provide theoretical basis for proper management and soil fertility recovery.

  Method  The pure Larix principis-rupprechtii stands (LP), mixed Larix principis-rupprechtii and Betula platyphylla stands (BL), and mixed Larix principis-rupprechtii and Pinus sylvestris var. mongolica stands (ML) were selected as the research objects in Saihanba Mechanical Forest Farm of Hebei Province, northern China. The soils of 0−20 cm soil depths were collected and analyzed to investigate the soil physicochemical and biological properties. SQI was used to evaluate soil fertility quality. SQI was determined in three steps by selecting a minimum data set (MDS) through principal component analysis, scoring the MDS indicators using non-linear scoring functions, and integrating the indicator scores into a SQI using the weighted additive equation.

  Result  There were different degrees of differences in soil physicochemical and biological properties among different mixed modes. Compared with LP, the soil physicochemical and biological properties of BL were significantly improved. The soil physicochemical conditions in ML were worse than those in LP. And there were no obvious differences in soil biological properties in ML and LP. The MDS consisted of soil microbial biomass nitrogen, total phosphorus, and ammonia nitrogen among 17 soil fertility quality indicators. There were significant differences in the SQI among three mixed modes, which were showed as: BL (0.59) > LP (0.47) > ML (0.39).

  Conclusion  The soil fertility quality differed significantly among varied mixed modes. The mixed Larix principis-rupprechtii and Betula platyphylla stands in Saihanba Mechanical Forest Farm can improve soil fertility. Soil fertility quality evaluation based on SQI by indexing approach can provide the basis for evaluating forest soil quality of other species and regions.