Abstract: Litter-derived phenolics are one of the main media affecting the surrounding environment of trees. The effects of mixed decomposition induced non-additive effects on litter phenolics release remain unclear. To investigate how coniferous and broad-leaved species litter affects the release of phenolics from each other during the mixed decomposition, we created nine combinations of 1∶1 (w/w) coniferous and broad-leaved mixed litters, with coniferous species litters of Picea asperata (Pa), Larix principis-upprechtii (Lp), and Pinus armandii (Par), and broad-leaved species litters of Acer tsinglingens (At), Betula albosinensis (Ba), and Catalpa fargesii (Cf) from Qinling Mountains. Litter mixtures with litterbag were incubated under dark indoor condition at 20-25 ℃ and constant humidity for six months. The results showed that: (1) Pa+At combination and Lp+At combination firstly had antagonistic overall effect on water-soluble phenols release of litter mixture, and turned to synergistic effect at the late stage (P<0.05). Specifically, the mutual effects between coniferous and broad-leaved litter on water-soluble phenols release also exhibited a similar pattern to their combinations. The other seven litter combinations had antagonistic overall effect on water-soluble phenols release of litter mixture (P<0.05). For the mixtures of Pa+Ba, Pa+Cf, Lp+Cf, and Lp+Ba, the water-soluble phenols release of coniferous litter was firstly inhibited and then accelerated (P<0.05) or unchanged in the late stage. The release was significantly inhibited in the mixtures of Par+Ba, Par+Cf, and Par+At (P<0.05). Generally, the water-soluble phenols release of broad-leaved litters was significantly inhibited in the aforementioned seven mixtures (P<0.05). (2) All combinations had overall antagonistic effects on condensed tannins release of litter mixtures (P<0.05). In litter mixtures of Lp+At and Lp+Ba, the condensed tannins release of coniferous litter tended to be accelerated, while an opposite pattern was observed for the broad-leaved litters (P<0.05). In other mixtures, coniferous and broad-leaved litters tended to significantly inhibit condensed tannins release of each other (P<0.05).

Key words: litter, phenolic substance, mixed decomposition, mutual effect, non-additive effect.