Abstract: [Objective] The aim of this study was to investigate the effect of the different modes of mixing birch (Betula platyphylla) into larch (Larix principis-rupprechtii) plantations on soil faunal communities and functional groups in mountain area of northern Hebei, China,to provide theoretical basis for the mixed management and sustainable management of larch plantation.[Method] In May, July and September, 2013, a pure larch forest (CK) and two mixed forests (M₁: young and even-aged larch stands mixed with birch; M₂: striped, and uneven-aged stands of larch mixed with birch) were investigated. Hand pick and the Tullgren method were employed to extract soil fauna in these forests. In accordance with the feeding habits, soil fauna were classified into four functional groups, including saprophagous, predacity, phytophagous and Omnivorous. In addition, the differences in soil faunal community structures, biodiversity, and functional group composition of these two mixed modes were analyzed.[Result] A total of 49 106 individuals, belonging to 70 groups, were identified. Among them, 2802 macro-fauna specimens were clustered into 50 groups with Formicidae, Curculionidae larvae and Nematocera larvae as the dominant groups; the others (meso- and micro-fauna) were classified into 33 groups with Acarina and Collembola as dominant ones. Our results showed that M₂ had a significant effect on soil faunal communities after six years of mixed reconstruction, in that the group numbers and mean density of macro-fauna, as well as group numbers of meso- and micro-fauna in M₂ were significantly higher than the these in CK and M₁ (P<0.05), respectively. Moreover, mixed modes, seasons and soil layers had significant influences on group numbers of soil fauna (P< 0.05) but not on mean density. Shannon-Wiener index (H) and Pielou evenness (J) of soil fauna in M₁ were significantly higher than those in CK. Remarkably, the density group index (DG) showed the most significant difference among the three forests (P< 0.001). Of the four functional groups, Saprophagous was the most dominant group in the three forests. Group numbers of saprophagous, predacity and phytophagous in M₂ were significantly higher than those in CK (P< 0.05). The redundancy analysis (RDA) indicated that the distribution of soil fauna in litter layer was significantly correlated with organic carbon (P= 0.048), and the distribution soil fauna in soil layers was significantly correlated with not only soil organic carbon (P= 0.006) but also total nitrogen (P= 0.02) and soil bulk density (P= 0.044).[Conclusion] Our results demonstrated that mixed management in larch plantation after six years enhanced soil faunal structure and diversity possibly through altering litter composition and number and soil physicochemical properties, especially in the uneven-aged striped mixed forests.

Key words: soil fauna, mixed modes, community structure, functional group, larch plantations