森林细根生产和周转研究

随着近 2 0多年来对细根功能的深入认识和研究方法的发展 ,林分细根生物量、生产和周转及其与环境因子的关系成为森林生态学的研究热点之一 ,开展了大量研究。本文在收集了大量研究报道基础上 ,对森林细根研究结果进行综述。结果如下 :细根 (直径 <2～ 5mm)生物量变化在 46～ 2 80 5g·m- 2 之间 ,大部分在 10 0～ 10 0 0g·m- 2 ;细根生物量分别占地下部分总生物量和林分总生物量的 3%～ 30 %和 0 .5 %～ 10 % ;北方常绿针叶林平均细根生物量最低 (2 16g·m- 2 ) ,热带常绿阔叶林最高 (10 87g·m- 2 )。细根年净生产量 2 0～ 1317g·m- 2 ·a- 1 ,占林分总净初级生产量的3%～ 84% ,大部分在 10 %～ 6 0 % ;从北方森林到温带、亚热带至热带森林 ,细根生产量呈增加趋势 ;针叶林细根生产在总净初级生产中的比例小于阔叶林 (常绿和落叶 )。树木细根生命周期短至数天 ,长达数年。细根年周转率 4.3%～ 2 73.2 % ,阔叶林细根周转率低于针叶林。细根生产和周转是土壤碳和养分的重要来源 ,细根生产向林地输入的生物量占总输入 (细根生产和地上枯落物输入 )的 6 .2 %～ 88.7%。除气候森林类型外 ,森林生态系统细根生物量、分布、生产、周转还因季节、土壤类型、立地条件和生长发育阶段而异。同时 ,还受树木体内碳

FINE-ROOT PRODUCTION AND TURNOVER FOR FOREST ECOSYSTEMS

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.