青藏高原东缘乔灌交错带地被物和土壤碳氮储量特征

Carbon and Nitrogen Storage of Ground Covers and Soils in the Forest-Shrub Ecotone of Eastern Qinghai-Tibet Plateau

为揭示青藏高原群落交错带地被物(枯落物和苔藓)和土壤碳、氮过程,以青藏高原东缘典型乔灌交错带云杉针叶林、云杉针叶林—高山柳灌丛交错区(乔灌)和窄叶鲜卑花灌丛3个林型为研究对象,采用野外调查和对地被物、土壤的采样分析,研究了乔灌交错带地被物和土壤有机碳和全氮储量及其分配特征。结果表明:3个林型的地被物有机碳和全氮储量大小顺序为乔灌>针叶林>灌丛,有机碳大小分别为28.73,19.96,5.31 t/hm^2,全氮储量大小分别为0.96,0.54,0.12 t/hm^2。灌丛0—30 cm土壤有机碳储量(148.37 t/hm^2)显著高于针叶林(118.19 t/hm^2)和乔灌(114.93 t/hm^2),而土壤全氮储量大小顺序则表现为灌丛(19.53 t/hm^2)>乔灌(14.60 t/hm^2)>针叶林(11.79 t/hm^2),10—20 cm土壤有机碳和全氮储量显著高于0—10 cm和20—30 cm土壤。综合地被物和土壤有机碳和全氮储量,3个林型地表有机碳、全氮储量大小顺序均表现为灌丛>乔灌>针叶林,0—30 cm土壤有机碳和全氮储量均显著高于地被物,分别占总储量的80.0%~96.5%和93.8%~99.3%。这些研究表明青藏高原东缘高寒灌丛群落扩张将增加地表碳、氮库,有利于生态系统碳、氮固存。

In order to reveal carbon and nitrogen processes of ground covers(litter and moss)and soils in the ecotone on the Qinghai-Tibet Plateau,the organic carbon and total nitrogen storage and allocation characteristics of ground covers and soils among three forest types in a typical ecotone(i.e.,Picea likiangensis coniferous forest,Picea likiangensis coniferous forest—Salix oritrepha shrub,Sibiraea angustata shrub)on the eastern Qinghai-Tibet Plateau were investigated through field investigation and the sample analysis of ground covers and soils.The results show that the organic carbon and total nitrogen storage of ground covers followed the order of forest-shrub>coniferous forest>shrub,with the value of 28.73 t/hm^2,19.96 t/hm^2,5.31 t/hm^2 and 0.96 t/hm^2,0.54 t/hm^2,0.12 t/hm^2,respectively.The organic carbon storage in 0—30 cm soil layer in shrub(148.37 t/hm^2)were significantly higher than those in coniferous forest(118.19 t/hm^2)and forest-shrub(114.93 t/hm^2),and the total nitrogen storage of soils followed the order of shrub(19.53 t/hm^2)>forest-shrub(14.60 t/hm^2)>coniferous forest(11.79 t/hm^2).Moreover,the organic carbon and total nitrogen storage in 10—20 cm soil layers were significantly higher than those in 0—10 cm and 20—30 cm soil layers.Combining the organic carbon and total nitrogen storage of ground covers and soils,the organic carbon and total nitrogen storage of soil surface were significantly different among the three forest types,following the order of shrub>forest-shrub>coniferous forest.Furthermore,the storage in 0—30 cm soil layer accounted for 80.0%~96.5%and 93.8%~99.3%of the organic carbon and total nitrogen storage of soil surface,which were significantly higher than those in ground covers.These results indicate that the expansion of alpine shrub communities can increase carbon and nitrogen pools,which is beneficial to ecosystem carbon and nitrogen sequestration on the eastern Qinghai-Tibet Plateau.