高原鼠兔干扰强度对高寒草甸土壤碳氮分布的影响

Effects of Plateau Pika(Ochotona Curzoniae)Disturbing Soil Carbon and Nitrogen Distribution in Alpine Meadow

采用高原鼠兔(Ochotona curzoniae)有效洞口数差异划分其干扰梯度的方法,研究其不同干扰强度对高山嵩草(Kobresia pygmaea)草甸土壤有机碳和速效氮分布特征及耦合关系的影响。结果表明:随着高原鼠兔干扰强度的增加,植被覆盖区和裸斑生境窗区各土层有机碳含量均先升高后降低,在干扰强度Ⅱ(有效洞口数密度为192个hm^(-2))时显著升高达到最大值(p<0.05),相比干扰强度Ⅰ时增加了21.51%和46.03%;裸斑生境窗区速效氮含量先升高后降低,在干扰强度Ⅱ时最大且显著高于植被覆盖区(p<0.05),高于植被覆盖区155.63%。高原鼠兔干扰下植被覆盖区0~10 cm土层有机碳、速效氮和铵态氮含量均显著高于10~20 cm土层,而硝态氮含量显著低于10~20 cm土层(p<0.05),且表层土壤有机碳占整个土层的69.74%;裸斑生境窗区0~10 cm土层速效氮和铵态氮含量均显著低于10~20 cm土层,硝态氮含量显著高于10~20 cm土层(p<0.05),而不同土层间有机碳含量仅在干扰强度Ⅰ时差异显著。高原鼠兔干扰下,土壤有机碳与速效氮、硝态氮、铵态氮在植被覆盖区为极显著的负相关关系(p<0.01),而在裸斑生境窗区为极显著正相关关系(p<0.01)。这说明高原鼠兔改变了土壤碳氮的耦合关系,适宜的干扰强度能明显提高高山嵩草草甸土壤有机碳的含量和形成氮素含量较高的裸斑生境窗区。

A study was conducted on how activities of plateau pika（Ochotona curzoniae）in Kobresia pygmaea meadows affect the distribution of soil organic carbon and readily available nitrogen in the soil and their coupling relationship in the effect,using the method of counting effective burrows density of the animals in the field as the basis for setting up a disturbance gradient. In the study,the activity or disturbance of the animals was divided into four levels in intensity. In Level I,112 effective burrows hm^-2 were found,Level II,192 were,Level Ⅲ,352 were,and Level Ⅳ,608 were. Results show that with the activity of the animal getting intensified,the contents of organic carbon in the 0～10 cm and 10～20 cm soil layers of the vegetation-covered land（over 80% of the land covered with vegetation）and bare land（patches of land devegetated by the burrowing animals,with only 10% of the vegetation left growing）rose significantly first and then dropped rapidly,and the contents were the highest in lands of Level Ⅱ or about 21.51% and 46.03% higher than that in lands of Level I. And furthermore,content of organic carbon was much higher in the topsoil layers of vegetation-covered lands than in those of bare lands. The content of readily available N in the bare lands increased significantly first and then declined apparently,and the increase in bare lands of Level II was the biggest or 155.63% higher than that in the vegetation-covered lands,which had significant differences. Under the disturbance of the animals,contents of soil organic carbon,soil available nitrogen and NH4^＋-N decreased with soil depth in the vegetation-covered lands and were much higher in the 0～10 cm soil layer than in the 10～20 cm soil layer,however,content of NO3^--N acted reversely and was lower in the 0～10 cm soil layer than in the 10～20 cm soil layer,where topsoil organic carbon accounted for 69.74% of the total in the soil. In the bare lands 0～10 cm soil layer,the soil available nitrogen and NH4^＋-N content were significantly lower than in the 10～20 cm soil layer and the NO3^--N content significantly higher than 10～20 cm soil layer,content of organic carbon did not varied much between the two soil layers except of Level I. Under the plateau pika＇s disturbance,soil organic carbon was in significantly negative relationships with available nitrogen,NO3^--N and NH4^＋-N in the vegetation-covered lands,but in significantly positive relationships in the bare lands. It indicates that the activities of the animals changed the coupling relationships of soil C and N and the disturbance of a proper intensity may significantly increase the content of soil organic carbon in the Kobresia pygmaea meadows and cause the formation of bare patches relatively high in nitrogen content,which provides room for expansion,colonization and reproduction of other grasses or opportunistic plant species. Burrowing activities of plateau pika can alter vertical distribution of soil nutrients,which enhances heterogeneity of the soil. All the findings in this study demonstrate that the study to investigate effects of plateau pika disturbing the soil in the alpine meadow should take into account the influence and meaning of the existence of bare patches and the necessity of unified vegetation types,and the population density of plateau pika should be controlled within a reasonable range in the Kobresia pygmaea meadow.