Abstract:

In many forest ecosystems,the production,death and decomposition of fine root appear to play a very important role in carbon and nutrient cycling,due to their rapid turnover rates.During 1999—2001,the production,distribution and turnover of fine roots were comparatively studied between two coniferous plantations(Fokienia hodginsii and Cunninghamia lanceolata) in Sanming,Fujian. Mean standing crop of total fine roots and living fine roots of F.hodginsii amounted to 389.7g·m^-2 and 216.3 g·m ^-2 ,respectively,being 1.41 times and 1.46 times as high as that of Chinese Fir,roots less than 0.5 mm in diameter(242.2 g·m^-2 )constituted 61.2% of total fine root standing crop,compared with 45.0% in Chinese Fir stand.The maximum differences of fine root density between two stands occurred in the soil layers of 0～10 cm,where root density of F.hodginsii(144.2 g·m^-2 )was 2.1 times as much as that of Chinese Fir(70.2 g·m^-2 ).Living fine root biomass peaked in March in F.hodginsii stand,and peaked in March and September in Chinese Fir stand.The weight loss rates of roots after the first year of decomposition and the decomposition rate coefficient of F.hodginsii were lower than those of Chinese Fir.Annual fine root net production and mortality of F.hodginsii were 320.2 and 326.5 g·m^-2 a^-1,respectively,being 1.27 times and 1.31 times as high as that of Chinese Fir,though a lower fine root turnover rate was found for F.hodginsii(1.48a^-1 vs 1.69a^-1 ).In F.hodginsii and Chinese Fir stands,fine roots each contributed to 19.84% and 19.21% of total NPP and equaled 48.74% and 51.00% of annual aboveground litterfall of tree layer,albeit they account for only 1.70% and 1.18% of total tree layer biomass,respectively.

Key words: Fokienia hodginsii, Cunninghamia lanceolata, Fine root, Distribution, Net productivity, Turnover rate