Abstract:

Fine roots turnover play an important role in carbon allocation and nutrient cycling in forest ecosystems. Seasonal dynamics of fine roots is the key for understanding the processes of fine roots turnover. From May to October in 2002, soil core method was used for estimating seasonal pattern of fine root (diameter<1 mm) parameters I.e. biomass, specific root length(SRL) and root length density (RLD) in Fraxinus mandshurica plantation located in Maoershan Experiment Station. The relationships of fine root biomass, SRL and RLD with soil N availability, average soil temperature in 10 cm depth and soil moisture were analyzed. Seasonal variation of fine root biomass was significant (P<0.05). The peak values of fine root biomass were observed in spring and autumn, but SRL and RLD were the highest in spring and lowest in autumn. SRL and RLD were higher in spring and summer means fine root diameter was thinner, in autumn, both parameters changed to small values significantly due to secondary thickening of fine root diameter or non-structure carbohydrates accumulation. Seasonal dynamics of fine roots was associated with soil N availability, soil temperature in 10 cm depth and soil moisture. Fine root biomass has significant relationship with NH₄⁺-N availability, but less correlated with NO₃^--N availability, soil temperature in 10 cm depth and soil moisture. Correlation of fine root parameters (biomass, RLD and SRL) seasonal dynamics and multi-factors (soil available N, soil temperature and soil moisture) were significant (P<0.05), which indicated that multi-factors were responsible to fine root dynamics. Further studies about the effects of soil temperature on SRL, RLD and non-structure carbohydrates will help us to understand fine root functions in different growing seasons and turnover of Fraxinus mandshurica plantations.

Key words: Fraxinus mandshurica, fine root, biomass, root length density (RLD), specific root length (SRL), seasonal dynamics