光辐射对青藏高原高寒草甸凋落物分解的影响

Effect of light radiation on litter decomposition in alpine meadow of the Tibetan Plateau.

光照对干旱半干旱生态系统凋落物分解有显著作用。然而,在太阳辐射强度大、高寒湿润的青藏高原东部高寒草甸,光辐射在凋落物分解中的作用尚不明确。本试验采用凋落物袋法,研究自然光照和遮光2种处理下10种高寒草甸常见物种(披针叶黄华Thermopsis lanceolata、珠芽蓼Polygonum viviparum、线叶嵩草Kobresia capillifolia、小花草玉梅Anemone rivularis、黄帚橐吾Ligularia virgaurea、麻花艽Gentiana straminea、大籽蒿Artemisia sieversiana、瑞苓草Saussurea nigrescens、垂穗披碱草Elymus nutans和矮藨草Scirpus pumilus)叶片凋落物分解特点。结果表明:(1)不同物种凋落物的木质素含量存在显著差异,其中珠芽蓼木质素含量最高(达29.44%),黄帚橐吾木质素含量最低(为4.91%);(2)整体上,遮光显著降低了凋落物质量损失率,而光照的影响程度也因物种而异;(3)无论在自然光照还是在遮光处理下,凋落物质量损失率与初始木质素含量均呈显著负相关关系;遮光明显降低木质素质量损失率,其降低程度也因物种而异。

Light radiation plays an important role in litter decomposition in arid and semi-arid ecosystems. Yet, whether light radiation significantly affects litter decomposition in Tibetan alpine meadow remains unclear. In present study, we measured leaf litter decomposition of ten common species （Thermopsis lanceolata, Polygonum viviparum, Kobresia capillifolia, Anemone rivularis, Scirpus pumilus, Gentiana straminea, Artemisia sieversiana, Saussurea nigrescens, Elymus nutans and Ligularia virgaurea） abundant in Tibetan alpine meadows under shading and control treat- ments. The results showed that species differed significantly in litter lignin content, with highest in P. viviparum （29.44%） and lowest in L. virgaurea （4.91%）. In general, shading decreased litter mass loss, while the decrease extent depended on species. Litter mass loss significantly neg- atively correlated with lignin content either in shading or in control treatments. Shading decreased the litter lignin mass loss, and the decrease extent varied with species. This study suggests that light radiation promotes litter decomposition through accelerating photodegration of lignin in Tibet- an alpine meadow.