城市香樟群落类型对土壤有机碳氮的影响

Effect of Cinnamomum camphora Communities on Soil Organic Carbon and Total Soil Nitrogen in Urban Area

以上海城市人工绿地为研究对象，比较研究不同香樟群落类型土壤有机碳（SOC）、全氮（TSN）含量和垂直分布特征。结果表明：（1）各类型香樟群落显著影响0～40cm土层平均SOC（Pd0．05），其中0～20cm土层SOC变化范围在10．77~26．87g／kg，20~40cm土层变化范围在6．60~12．87g／kg，均表现为乔灌草结构的香樟混交林群落（MF）〉地被覆盖的香樟纯林群落（PF）〉土壤裸露的香樟纯林群落（BF）；（2）0～40cm土层土壤TSN和C／N因群落类型而异，变化趋势与SOC相同，但差异性并不如SOC明显，总体而言碳素增加速度高于氮素；（3）群落叶凋落量与土壤有机碳和全氮分别显著正相关，R2达到0．9483和0．7176。混交林叶凋落量对土壤有机碳和全氮的增加效应大于纯林，提高了114．90％。研究表明，群落通过地上凋落物的输入和地下空间根系周转而影响SOC和TSN，城市配置香樟群落时，应考虑多树种混交，多层次搭配，增加地上和地下有机物输入量，提高土壤SOC含量，增强土壤碳汇能力。

The soil organic carbon （SOC）,total soil nitrogen （TSN）and their distribution in the soil profile under different Cinnamomum camphora community types were studied in Shanghai urban area. The results showed that community types significantly influenced SOC in the 0-40 cm soil layer （P〈0. 05）. SOC in the 0-20 cm soil layer varied from 10.77 to 26. 87 g/kg,in the 20-40 cm layer from 6.60 to 12.87 g/kg,in the order of mixed forest planting with grass and shrubs 〉 pure forest only with grass 〉 pure forest on bare soil. TSN and C/N in the 0-40 cm soil layer varied with community types in the same order with SOC,but in less remarkable difference. Carbon （C）got the higher rate of increase in soil than Nitrogen （N）. There was a significant positive relationship between leaf litter mass and SOC （R2 =0. 9483）and TSN （R2= 0. 7176）. The increase of leaf litter mass affected SOC and TSN which rose by 114. 90% in mixed forest compared to pure forest. We conclude that plant community types modify the input of litter mass and fine root turnover,and thereby influence SOC and TSN. With more mixed species and structured collocation, Cinnamomum camphora community increased the aboveground and underground input of organic matter and improved SOC and soil carbon sink capacity.