Abstract:

The fine-root biomass and its vertical distribution, production, turnover, lifespan of global major climatic forest types and its role in C and nutrient cycling of forest ecosystems were reviewed and evaluated based on published information and 169 data sets. The fine-root biomass varied from 46 to 2805g·m^-2, mostly between 100～1000 g·m^-2, accounting for 3%～30% and 0.5%～10% respectively of below-ground biomass and total biomass of ecosystems. Boreal evergreen needleleaf forest had the lowest average fine-root biomass (216 g·m^-2) while tropical evergreen broadleaf forest had the highest (1087g·m^-2). Annual fine-root net primary production (NPP) was 20～1317 g·m^-2·a^-1, amounting to 3%～84% of total stand NPP, mostly 10%～60%. The fine-root NPP tended to increase from boreal forest, through cold-temperate, warm-temperate and subtropical forest, to tropical forest ecosystem. The percentage of fine-root NPP in total NPP of needleleaf forest seems lower than that of broadleaf forest within same climatic zone. The fine-root lifespan of tree species varied from several days to years, with annual fine-root turnover between 4.3%～273.2%. The necromass input through fine-root turnover accounted for 6.2%～88.7% of total input from both above- and below-ground, indicating substantial amount of C and nutrients input from the fine-root production and turnover. Apart from the climatic forest type, fine-root biomass, production and turnover varied with seasons, soil type, site conditions, development stage of forest and etc. They are also controlled by carbon source-sink relations, involving above-ground assimilation,carbonhydrate needed for fine-root growth and maintenance and site-specific conditions such as soil nutrients, water, temperature, toxic element, mycorhiza and other soil factors.

Key words: Forest, Fine-root, Biomass, Production, Turnover, Lifespan