该文研究了华北落叶松(Larix principis-rupprechtii)人工林细根生物量水平分布和季节变化特征。采用钻土芯法(土钻内径7.0 cm), 在距树干20、50和100 cm处设取样点, 每个样点处分3层(0~10、11~20和21~30 cm)钻取土芯, 取样时间为5、7、9和10月。华北落叶松人工林细根(≤2 mm)生物量全年平均值为224.89 g·m^-2, 在水平分布上表现为100 cm处细根生物量最大(244.20 g·m^-2), 其次为20 cm处(221.03 g·m^-2), 50 cm处最少(209.45 g·m^-2)。在0~30 cm土层, 总细根(包括活跟和死根)生物量季节变化范围在169.67~263.09 g·m^-2之间, 9月细根生物量最大, 5月细根生物量最少。0~10 cm土层细根生物量季节变化差异显著(p<0.05), 11~20和21~30 cm差异不显著(p>0.05)。距树干100和20 cm处(0~10 cm土层), 细根生物量的季节变化差异明显(p<0.05), 9月总细根生物量最大(172.82和185.68 g·m^-2), 5月总细根生物量最少(69.28和73.47 g·m^-2); 50 cm处季节变化差异不明显(p>0.05)。细根生物量分布和季节变化不仅受土壤垂直格局影响同时也与距树干不同水平距离有很大的关系。

Aims Root systems are important in carbon and nutrient cycling in forest ecosystem. There is much research on vertical distribution and seasonal dynamics of fine root biomass; however, horizontal distribution and seasonal dynamics at different horizontal distances remain poorly understood. Our objectives are to determine how fine root biomass and seasonal dynamics of fine root biomass change with horizontal distance.

Methods The study was conducted in a 28-year-old Larix principis-Rupprechtii plantation in Guandi Mountain (110°30′ E, 37°28′ N) in Shanxi Province, China. Soil cores (30.0 cm depth, 7.0 cm diameter) were taken in May, July, September and October,2004, at different horizontal distances (100, 50 and 20 cm) from the stem. Soil cores were separated into 3 sections, 0-10, 11-20 and 21-30 cm. Fine roots (≤2 mm) were separated into live and dead, and live fine roots were classified into two categories, ≤1 and 1-2 mm. Roots were dried at 80^oC to constant mass for weighing.

Important findings The biomass of fine roots was 244.20, 209.45 and 221.03 g·m^-2at 100, 50 and 20 cm, respectively, and differences were not statistically significant (p>0.05). Total fine root biomass changed from 169.67 to 263.09 g·m^-2. Differences were larger at 0-10 cm depth than at 11-20 and 21-30 cm. Seasonal dynamics of fine root biomass changed significantly in the 0-10 cm layer (p<0.05), and it changed more at the 100 and 20 cm distances rather than at 50 cm. Horizontal differences in fine roots likely resulted from tree crowns causing heterogeneous illumination, soil water, temperature and nutrients. The study indicates that combined and integrated horizontal distribution factors should be considered in research on spatial distribution and seasonal dynamics of fine roots.