In order to determine how the diameter class length distribution (DCLD) of fine roots of Chinese fir (Cunninghamia lanceolata) would be affected by soil warming, nitrogen addition and their interaction, a factorial experiment of soil warming (ambient, +5 ℃) and nitrogen addition (ambient, +4 and +8 g N·m-2·a-1) was carried out in the Chenda State-owned Forest Farm in Sanming, Fujian Province. An expanded extreme value model fitted the DCLD of roots of all the six treatments very well (R2=0.97). The model parameters showed that soil warming reduced the total root length, but its effect on root diameter was not significant. Nitrogen addition decreased both total root length and root diameter. The interaction of soil warming and nitrogen addition had significant effects on total root length, but had no significant effects on root diameter. DCLD of fine roots under the six treatments could be fitted well by the extreme value function (R2>0.98). The correlation analysis showed that specific root length for roots of 0-1 mm diameter was significantly negatively correlated with the parameter c, and the actual total root length was significantly positively correlated with the parameter b. It was concluded that the root morphology of Chinese fir seedlings would respond to both soil warming, nitrogen addition and their interaction, and these responses could be reflected by the changes in parameters of the extreme value model.
通过在福建省三明市陈大林业国有林场内开展土壤增温(增温5 ℃、不增温)和氮添加(不添加、4、8 g N·m-2·a-1)的交互试验(共6个处理),研究土壤增温、氮添加及二者交互作用对杉木细根径级根长分布的影响,用扩展模型可很好地拟合6个处理的径级根长分布(R2=0.97).结果表明: 增温使杉木细根总根长变小,但对细根直径影响不显著;氮添加使杉木细根总根长和直径均变小;增温和氮添加的交互作用对细根总根长有显著影响,但对细根直径无显著影响.6个处理细根径级根长分布均能用极值函数模型较好地拟合(R2>0.98).相关分析显示,直径<1 mm细根的比根长与极值模型拟合参数c值呈显著负相关,实际总根长与极值模型拟合参数b呈显著正相关.增温和氮添加及其交互作用可以影响杉木细根形态特征;极值模型拟合各处理径级根长分布所得参数在一定程度上可以反映细根形态特征对环境条件变化的响应.
Keywords: diameter class length distribution; extreme value model; nitrogen addition; soil warming.