藏北高寒草原典型物种凋落物分解与养分动态

Litter decomposition and nutrient dynamics of typical plant species in an alpine steppe ecosystem in Northern Tibet

凋落物分解在陆地生态系统碳循环和养分循环中起着重要作用,以往的研究主要集中在森林生态系统和温带草原生态系统,而对于高寒草原生态系统关注不足。本研究采用凋落物袋法,通过为期3年的野外分解试验,研究青藏高原北部高寒半干旱草原4种典型物种凋落物[紫花针茅(Stipa purpurea)、青藏苔草(Carex moocroftii)、火绒草(Leontopodium pusillum)、昆仑蒿(Artemisia nanschanica)]的分解动态。结果表明,4种凋落物的质量损失在不同物种和分解时间下存在显著差异,在试验结束时,各物种凋落物失重率大小顺序为昆仑蒿(46.69%)>紫花针茅(44.97%)>青藏苔草(33.55%)>火绒草(17.05%);凋落物的分解常数在0.07～0.22,分解的半衰期在3.14～10.50年,分解的周转期在13.59～45.37年;分解过程中氮(N)、磷(P)养分主要表现为累积–释放和直接释放两种模式,在试验结束时,4种凋落物N、P养分的残留量均表现为火绒草>青藏苔草>紫花针茅>昆仑蒿。本研究将丰富对高寒地区半干旱草原生态系统的生物地球化学循环过程的认识。

Litter decomposition is a key process that regulates the carbon and nutrient cycling in terrestrial ecosystems.Most previous studies were conducted in forest and temperate grassland ecosystems,while limited studies have focused on alpine steppe ecosystems.Here,we employed the litter-bag method to study the decomposition of four kinds of alpine steppe species,including Stipa purpurea,Carex moocroftii,Leontopodium pusillum,and Artemisia nanschanica.The results showed significant differences in litter mass loss among plant species and decomposition times.At the end of the experiment,the order of litter mass loss was A.nanschanica(46.69%)>S.purpurea(44.97%)>C.moocroftii(33.55%)>L.pusillum(17.05%).Additionally,the decomposition constant(k)of the four species was between 0.07 and 0.22,the half-life of the litter decomposition was between 3.14 years and 10.50 years,and the turn-over periods were between 13.59 and 45.37 years.The litter N and P dynamics during decomposition largely presented as"cumulation release"and"direct release"patterns.At the end of the experiment,the N and P remaining in the four species were in the order of L.pusillum>C.moocroftii>S.purpurea>A.nanschanica.This study will enrich our understanding of biogeochemistry cycling in alpine steppe ecosystems.