科尔沁沙地不同林龄樟子松人工林土壤生态化学计量特征

Soil Ecological Stoichiometry under the Planted of Pinus sylvestris var.mongolica Forests with Different Stand Ages in the Horqin Sandy Land

以科尔沁沙地不同林龄（15 a、25 a、35 a和45 a）樟子松林为对象,研究其0-100 cm土层土壤有机碳、全氮和全磷含量及其生态化学计量特征,探讨土壤碳氮磷化学计量特征的垂直分布规律及随林龄的变化规律。结果表明：（1）4种林龄樟子松林土壤（0-20 cm土层）有机碳、全氮和全磷含量分别为7.34、0.39 g·kg^-1和0.19 g·kg^-1,均低于全国平均水平。（2）随着林龄的增加,有机碳含量、C/N和C/P均呈现增大的趋势;全氮和全磷含量呈现先增加后降低（45 a生林分显著降低）;而N/P的变化不显著。（3）随着土层的加深,有机碳和全氮含量的变化趋势基本一致,均呈现逐渐降低的趋势,但是各林分在0-20 cm土层中的有机碳和全氮含量均不足总含量的1/3;C/N和C/P呈现相反的变化趋势（C/N增加、C/P降低）;而全磷含量和N/P的垂直分布较为均匀,变化不大。综上所述,本研究区樟子松林土壤中的有机碳、全氮、全磷含量极为贫瘠,但樟子松人工林种植增加了土壤碳、氮、磷养分含量;各林龄樟子松林土壤同时受氮、磷养分的限制,但随土层加深受氮的限制更为显著。

The observations of this study were to measure the contents of soil organic carbon（C）,total nitrogen（N）and total phosphorus（P）in soil layer from 10 cm to 100 cm in depth under the planted Pinus sylvestris var.mongolica forests with different stand ages（for 15,25,35 and 45 years）over the Horqin Sandy Land.Moreover,the vertical distribution of ecological stoichiometric ratios of soil organic C,total N and total P under the planted forests with different stand ages was investigated so as to provide a theoretical basis for sustainable management of the planted forests.The results showed that the contents of soil organic C,total N and total P varied in ranges of2.51-8.27,0.12-0.45 and 0.14-0.21 g·kg^（-1）respectively,and all of them were below the national average level in China.As the increase of stand age of the forests,the contents of soil organic C,C/N and C/P were increased;the total N and total P were increased at first and then decreased,a significant decrease occurred under the forest with a 45 year stand age,and there was no significant change in N/P.As the increase of soil depth,both the soil organic C and total N were decreased,their contents were lower than one third of the total.While the C/N was increased but the C/P was decreased.The study results revealed that the soil C,N and P storages were increased although the contents of these soil nutrients were extremely poor in the Horqin Sandy Land.