Plant functional traits affect soil nutrient cycling in many ecosystems, but high levels of diversity make it challenging to identify their influence in tropical rainforests. Here, we used a litter manipulation experiment to demonstrate that differences in litter chemistry alone are sufficient to drive changes in soil nitrogen (N) cycling within a two-year period in a lowland tropical rainforest. Previously, we used airborne imaging spectroscopy to identify ten 0.25 ha plots on the Osa Peninsula of southwestern Costa Rica, each containing 10–20 emergent trees, with relatively high or low mean canopy N content (± 0.4 standard deviations of the landscape mean; n = 5 each). Plots with high canopy N content had higher soil inorganic N concentrations, faster net N cycling rates, and greater nitrous oxide (N₂O) emissions. Because abiotic conditions were similar among the plot types, we hypothesized that litter inputs drove the formation of these high and low soil N patches. We tested this hypothesis with a reciprocal litter transplant experiment. After two years of monthly treatments, litter inputs from the high canopy N plots increased soil N availability in the low canopy N plots by 30% but had no measurable effects on net N cycling rates or N₂O emissions. Surprisingly, litter inputs from the low canopy N plots increased soil N availability and net nitrification in the high canopy N plots. While somewhat counterintuitive from a canopy N perspective, these results may reflect a more nuanced effect of litter chemistry. Although low canopy N plot litter had lower N content than high canopy N plot litter, it leached relatively more and higher quality soluble carbon (C), which we speculate may have had a positive priming effect, releasing N from more recalcitrant compounds. Additionally, low canopy N plot litter supported higher rates of free-living N fixation, which could have directly increased soil N availability. Overall, our results show that tropical tree assemblages with differing foliar chemistry can directly influence soil properties through litter inputs, and that this effect may be mediated not only by litter N, but also relative C solubility and chemistry.

植物功能性状影响许多生态系统中的土壤养分循环，但是高度的多样性使其难以确定其在热带雨林中的影响。在这里，我们使用垃圾处理实验来证明，在低地热带雨林中，仅垃圾化学上的差异就足以驱动两年内土壤氮（N）循环的变化。以前，我们使用机载成像光谱技术确定了哥斯达黎加西南部奥萨半岛上的十个0.25公顷土地，每个地块包含10至20棵新兴树木，平均冠层N含量相对较高或较低（景观平均值的±0.4标准差；n  = 5个）。冠层氮含量较高的地块的土壤无机氮含量较高，净氮循环速率更快，一氧化二氮（N₂ O）排放。由于各样地类型之间的非生物条件相似，我们假设垫料输入驱动了这些高低土壤氮素斑块的形成。我们通过对立的垫料移植实验验证了这一假设。经过两年的月度处理，高冠层N田的垫料输入量使低层N田的土壤氮素利用率提高了30％，但对净氮循环速率或N ₂却没有可测量的影响O排放。出人意料的是，低冠层N地块的凋落物输入增加了高冠层N地块的土壤氮素利用率和净硝化作用。从冠层N角度看，虽然有些违反直觉，但这些结果可能反映了垫料化学作用的细微差别。虽然低冠层N垫料的氮含量比高冠层N垫料的氮含量低，但它浸出的相对较多且质量较高的可溶性碳（C），我们推测这可能具有积极的引发作用，可从更多顽固的化合物中释放出N。此外，低冠层氮积土支持较高的自由固氮率，这可能直接增加了土壤氮素的利用率。总体而言，我们的结果表明，叶面化学性质不同的热带树木组合可以通过凋落物的输入直接影响土壤特性，