Austin Amy T, Araujo Patricia I, Leva Paula E
Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura and Consejo Nacional de Investigaciones Científicas y Tecnicas, Facultad de Agronomia, Universidad de Buenos Aires, Av. San Martin 4453, Buenos Aires (C1417DSE) Argentina.
Ecology. 2009 Sep;90(9):2642-7. doi: 10.1890/08-1804.1.
Litter lignin and nutrient content, annual rainfall, and biotic activity are not good predictors of litter decomposition in arid and semiarid ecosystems, suggesting that other factors may be important in controlling carbon turnover. We explored the relative importance of litter position (above- vs. belowground), litter type (leaf vs. root), and pulsed water events (large vs. small) on mass loss with grass species of the semiarid Patagonian steppe. In a factorial experiment of mesocosms, we incubated leaf and root litter simultaneously above- and belowground and manipulated water availability with large and small pulses. Significant interactions between position and litter type and position and pulse sizes demonstrated interactive controls on organic mass loss. Aboveground decomposition showed no response to pulse size or litter type, as roots and leaves decomposed equally rapidly under all circumstances. In contrast, belowground decomposition was significantly altered by litter type and water pulses, with roots decomposing significantly slower and small water pulses reducing belowground decomposition. The results of this mesocosm experiment support the idea that controls other than water availability may dominate aboveground mass loss, while a combination of recalcitrant litter and water penetration in the soil profile are critical factors determining belowground decomposition, which is ultimately mediated by biotic degradation.
凋落物的木质素和养分含量、年降水量以及生物活性并非干旱和半干旱生态系统中凋落物分解的良好预测指标，这表明其他因素可能在控制碳周转方面具有重要意义。我们以半干旱巴塔哥尼亚草原的草本植物为研究对象，探讨了凋落物位置（地上与地下）、凋落物类型（叶片与根系）以及脉冲式水分事件（大脉冲与小脉冲）对质量损失的相对重要性。在一个中宇宙的析因实验中，我们同时将叶片和根系凋落物置于地上和地下进行培养，并通过大脉冲和小脉冲来控制水分供应。位置与凋落物类型以及位置与脉冲大小之间的显著交互作用表明了对有机物质损失的交互控制。地上分解对脉冲大小或凋落物类型没有响应，因为在所有情况下根系和叶片的分解速度相同。相比之下，地下分解受到凋落物类型和水分脉冲的显著影响，根系分解明显较慢，小水分脉冲会减少地下分解。这个中宇宙实验的结果支持了这样一种观点，即除水分供应外的其他控制因素可能主导地上质量损失，而难分解的凋落物和土壤剖面中的水分渗透相结合是决定地下分解的关键因素，而地下分解最终是由生物降解介导的。
