Abstract: In order to reveal the relationship between plant root growth strategy and the environment and the contribution of fine root turnover to grassland soil carbon pool, the authors sampled root to one meter soil depth at 17 sites across the desert grasslands, typical grasslands and meadow grasslands across Inner Mongolia, and lowerorder roots were separated from total root. The results showed that 1) lower-order root biomass was positively correlated with total root biomass, and both lower-order root biomass and total root biomass were positively related to annual average precipitation and soil nitrogen content, negatively related to annual average temperature; 2) the ratio of lower-order root biomass to total root biomass showed a trend of desert grassland (14%) < typical steppe (20%) < meadow steppe (39%), and the ratio was positively related to average annual rainfall, negatively related to annual average temperature and not related to soil carbon and nitrogen content; 3) the vertical distribution patterns of lower-order root biomass and total root biomass were similar: decreasing with soil depth in meadow grasslands with 85% of the biomass distributed in the 0–40 cm layer, while not significantly differented among soil layers in typical grasslands and desert grasslands. This study suggested that 1) plant roots could response the two environmental factors through different mechanisms; 2) in habitats with lower water availability, plants might allocate less C to the lower-order roots to reduce C loss, and allocate more C to higher-order roots to store water and nutrient. It is further suggested that fine root absorption efficiency may be higher in drier habitats than moister habitats.

Key words: fine root biomass, absorptive roots, spatial distribution, vertical distribution, absorption efficiency

摘要： 为了揭示根系生长策略与环境的关系以及草地植物根系周转对土壤碳的贡献, 在内蒙古荒漠草地、典型草地以及草甸草地设置17 个样点, 分析总根生物量、低级根生物量和低级根占总根生物量之比随草地类型与土层深度的变化及其与气候、土壤因素之间的关系。结果表明: 1) 低级根生物量与总根生物量正相关, 低级根生物量和总根生物量都与年均降水量、土壤氮含量正相关, 与年均温为负相关; 2) 低级根占总根生物量之比总体上呈现荒漠草原(14%)<典型草原(20%)<草甸草原(39%)的趋势, 与年均降水量正相关, 与年均温负相关, 与土壤全碳和全氮不相关; 3) 低级根生物量随土层的垂直分布规律与总根生物量一致, 在草甸草地随着土层加深而降低, 低级根主要分布在0~40 cm 表层土壤中(85%以上), 而在典型草地与荒漠草地则土层之间差异不显著。研究得到以下结论: 1) 草地植物根系可能通过不同机制响应温度和降水这两个环境因子; 2) 植物在水分贫乏的生境中可能通过降低对快速周转的低级根的投入来减少碳支出, 而投入更多的高级根来存储水分养分, 同时表明干旱生境中植物细根的水分养分吸收效率可能高于湿润生境。

关键词: 细根生物量, 吸收根, 空间分布, 垂直分布, 吸收效率