Abstract

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.

摘要

年总降水量通常无法预测凋落物分解率，尤其是在半干旱地区，降水频率 ( PF ) 显着影响分解。我们假设低PF会降低分解率。我们在三个深度（地上的垃圾、地表以下 0-10 和 10-20 厘米的垃圾）对三种一年生物种的垃圾进行了垃圾袋分解实验。我们使用了相同的总量（280 毫米），但在生长季节使用了三种降水频率（PF1，每 5 天 10 毫米；PF2，每 10 天 20 毫米；PF3，每 20 天 40 毫米）。我们测量了每个物种在三个位置的剩余质量、碳 (C) 含量、氮 (N) 含量、C:N 比以及 C 和 N 损失。凋落物分解和 C 和 N 动态受物种、深度和PF 的影响。低PF显着减少凋落物分解（PF1、PF2 和 PF3 的质量损失率分别为 49.7、49.1 和 41.2%）。这种效应与放置深度相互作用，但与物种无关。除了 N 损失率之外，C 和 N 动力学也存在这种相互作用。PF对C损失的影响主要来自其对质量损失的影响，而N损失不受PF影响。我们的结果强调了PF在半干旱地区凋落物分解中的重要性。PF之间的关系凋落物分解为区域碳循环模型和碳收支预测提供了理论依据。我们的结果还表明，由于分解速度更快，尤其是在地下，非禾本科物种在改善半干旱沙质草地土壤碳方面表现出比草更高的潜力。