Effect Of Precipitation Frequency On Litter Decomposition Of Three Annual Species (Setaria Viridis, Artemisia Sacrorum, And Chenopodium Acuminatum) In A Semi-Arid Sandy Grassland Of Northeastern China

Annual total precipitation typically fails to predict litter decomposition rates, especially in semi-arid regions, where precipitation frequency (PF) significantly affects decomposition. We hypothesized that low PF would decrease decomposition rates. We performed a litterbag decomposition experiment with litter of three annual species at three depths (aboveground litter, litter at 0-10 and 10-20 cm below the surface). We used the same total amount (280 mm), but three precipitation frequencies (PF1, 10 mm every 5 days; PF2, 20 mm every 10 days; PF3, 40 mm every 20 days) during the growing season. We measured the remaining mass, carbon (C) content, nitrogen (N) content, C:N ratio, and C and N losses of each species at the three positions. Litter decomposition and the C and N dynamics were influenced by species, depth, and PF. Low PF significantly decreased litter decomposition (mass loss rates of 49.7, 49.1, and 41.2% for PF1, PF2, and PF3, respectively). This effect interacted with placement-depth but not with species. This interaction also existed for C and N dynamics except for the N loss rate. The influence of PF on C loss mainly resulted from its effect on mass loss, whereas N loss was not affected by PF. Our results highlight the importance of PF for litter decomposition in a semi-arid region. The relationship between PF and litter decomposition provides a theoretical basis for regional carbon-cycle models and carbon budget predictions. Our results also suggest that non-graminaceous species showed higher potential than grasses for improving soil carbon in semi-arid sandy grasslands due to faster decomposition rates, especially below ground.