Abstract: [Objective] In order to explore the effects of different regeneration pattern on the dynamic distribution of fine root biomass, and to examine the relationship between fine root biomass and soil properties, the fine root biomass and soil nutrient availability were investigated in primary forest, secondary forest and plantation, respectively. [Method] This study was carried out in mixed broadleaved-Korean pine(Pinus koraiensis) forest, secondary birch forest (natural regeneration after clear cutting), Korean pine plantation and Dahurian larch(Larix gmelinii) plantation (artificial planting after clear cutting) in Xiaoxing'an Mountains. Fine roots (≤2 mm in diameter) and soil samples were collected by taking soil cores successively from May to September in 2013 for each forest type. [Result] The results showed that fine root biomass in the mixed broadleaved-Korean pine forest and Korean pine plantation were significantly higher than that in secondary birch forest and Dahurian larch plantation. There were significant differences in the vertical distribution of fine root biomass in the four forest types. Fine root biomass was mainly distributed in 0-20 cm soil layer, and the highest was in the secondary birch forest (75.81%) and the lowest was in the mixed broadleaved-Korean pine forest (62.73%). There were seasonal fluctuations of fine root biomass in the four forest types. In each forest type, both fine root biomass and necromass showed two peaks. There was no significant correlation between soil temperature and fine root biomass in the four forest types, however, there was a highly significant positive correlation between soil moisture and fine root biomass in the three regenerated forest types (except the mixed broadleaved-Korean pine forest). The soil hydrolysis nitrogen content was highly significantly correlated with fine root biomass in all the four forest types. The available soil phosphate content was significantly negatively correlated with fine root biomass in the secondary birch forest. [Conclusion] Fine root biomass in the Korean pine plantation and mixed broadleaved-Korean pine forest were significantly higher than that in the secondary birth forest and Dahurian larch plantation dominated by pioneer species B. platyphylla and L. gmelinii, respectively. The vertical distribution of fine root biomass was not even, but mainly concentrated in the soil surface where nutrient availability was higher. Forests in climax stage adopted a more refined strategy of accession to resources than forests in early succession stage, thus the proportion of fine root biomass in bottom soil layers was significantly higher in the mixed broadleaved-Korean pine forest and Korean pine plantation. The seasonal dynamics of fine root biomass was consistent with phenological rhythm, and the peak of fine root biomass appeared in late spring and early autumn.

Key words: Xiaoxing'an Mountains, fine root biomass, vertical distribution, seasonal dynamics, soil properties