Abstract: In May 2013, standing leaf litter of the dominant species Carex atrofusca was collected in an alpine swamp meadow in Tibetan Plateau. In early June, we set up three decomposition zones, including longtime flooding, periodic flooding and no flooding. The litterbag method was used, with different mesh sizes \[big mesh (4.5 mm), medium mesh (2.0 mm) and small mesh (0.1 mm)\]. Our objective was to study the effects of flooding condition and mesh size on early litter decomposition in an alpine swamp meadow. The results showed that longterm flooding significantly inhibited the decomposition of litter, and there was no significant difference in litter decomposition under periodic flooding and no flooding. Mesh size affected significantly litter decomposition, and big mesh exhibited the highest litter mass loss, followed by medium, and small mesh size. In the early period of litter decomposition, litter was characterized by nitrogen and phosphorus enrichment, irrespective of any treatment. Flooding condition affected significantly nitrogen and phosphorus enrichment. Mesh size influenced significantly nitrogen enrichment, but not phosphorus enrichment. A significant interaction of flooding conditions with mesh size was found for nitrogen enrichment, but not for phosphorus enrichment. Mesh size could reflect effects of different soil biota on litter decomposition. Therefore, our results indicated that flooding condition and soil biota had important influences on carbon, nitrogen and phosphorus cycling, and thus ecosystem functioning of alpine swamp meadow in Tibetan Plateau.

Key words: precipitation variation., stem hydraulic trait, Caragana korshinskii, Salix psammophila