塞罕坝华北落叶松纯林和混交林土壤肥力质量评价

  目的  基于土壤质量指数（SQI），研究华北落叶松林不同混交方式对土壤肥力质量的影响，为其合理经营和地力恢复提供理论依据。  方法  该研究以河北省塞罕坝林场华北落叶松纯林（落叶松纯林）、华北落叶松白桦混交林（落桦混交林）和华北落叶松樟子松混交林（落樟混交林）为研究对象，采集和分析0 ~ 20 cm土层的土壤进行土壤理化性质、生物性质的调查研究，利用SQI法进行土壤肥力质量评价。建立SQI包括3个步骤:采用主成分分析法筛选最小数据集（MDS），利用非线性得分函数计算MDS指标得分，利用加权求和模型计算SQI。  结果  不同混交方式间土壤理化和生物性质存在不同程度的差异。与落叶松纯林相比，落桦混交林的土壤理化和生物性质有了明显改善；落樟混交林的土壤理化状况较差，土壤生物性质与落叶松纯林没有明显差异。在17个土壤肥力质量指标中，MDS由土壤微生物生物量氮、全磷、氨氮3个指标组成。不同混交方式间SQI差异显著，表现为落桦混交林（0.59） > 落叶松纯林（0.47） > 落樟混交林（0.39）。  结论  土壤肥力质量在不同混交方式下差异显著，塞罕坝机械林场落叶松白桦混交林有利于改善土壤肥力。利用指数法建立SQI进行土壤肥力质量评价，可为其他树种或其他地区的森林土壤质量评价提供借鉴。 

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.