Wedin David A, Pastor John
Natural Resources Research Institute, University of Minnesota, 55811, Duluth, MN, USA.
Oecologia. 1993 Nov;96(2):186-192. doi: 10.1007/BF00317731.
Although Wedin and Tilman (1990) observed large differences in in situ N mineralization among monocultures of five grass species, the mechanisms responsible were unclear. In this study, we found that the species did not change total soil C or N, and soil C: N ratio (range 12.9-14.1) was only slightly, but significantly, changed after four years. Nor did the species significantly affect the total amount of N mineralized (per g soil N) in year-long aerobic laboratory incubations. However, short-term N mineralization rates in the incubations (day 1-day 17) differed significantly among species and were significantly correlated with annual in situ mineralization. When pool sizes and turnover rates of potentially mineralizable N (N) were estimated, the best model treated N as two pools: a labile pool, which differed among species in size (N, range 2-3% of total N) and rate constant (h, range 0.04-0.26 wk), and a larger recalcitrant pool with a constant mineralization rate across species. The rate constant of the labile pool (h) was highly correlated with annual in situ N mineralization (+0.96). Therefore, plant species need only change the dynamics of a small fraction of soil organic matter, in this case estimated to be less than 3%, to have large effects on overall system N dynamics.
尽管韦丁和蒂尔曼（1990年）观察到五种草类单作之间原位氮矿化存在很大差异，但其背后的机制尚不清楚。在本研究中，我们发现这些物种并未改变土壤总碳或总氮含量，且经过四年后，土壤碳氮比（范围为12.9 - 14.1）仅有轻微但显著的变化。这些物种在为期一年的好氧实验室培养中，对矿化的总氮量（每克土壤氮）也没有显著影响。然而，培养过程中的短期氮矿化速率（第1天至第17天）在不同物种间存在显著差异，且与年度原位矿化显著相关。当估算潜在可矿化氮（N）的库大小和周转率时，最佳模型将N视为两个库：一个是活性库，其大小在不同物种间有所不同（N，占总氮的2 - 3%），速率常数（h，范围为0.04 - 0.26周），另一个是较大的难分解库，其矿化速率在各物种间保持恒定。活性库的速率常数（h）与年度原位氮矿化高度相关（+0.96）。因此，植物物种只需改变一小部分土壤有机质的动态变化，在这种情况下估计小于3%，就能对整个系统的氮动态产生重大影响。
