PDF(Pubmed)
Abstract：
Soil extractable nitrate, ammonium, and organic nitrogen (N) are essential N sources supporting primary productivity and regulating species composition of terrestrial plants. However, it remains unclear how plants utilize these N sources and how surface-earth environments regulate plant N utilization. Here, we establish a framework to analyze observational data of natural N isotopes in plants and soils globally, we quantify fractional contributions of soil nitrate (fNO3-), ammonium (fNH4+), and organic N (fEON) to plant-used N in soils. We find that mean annual temperature (MAT), not mean annual precipitation or atmospheric N deposition, regulates global variations of fNO3-, fNH4+, and fEON. The fNO3- increases with MAT, reaching 46% at 28.5 °C. The fNH4+ also increases with MAT, achieving a maximum of 46% at 14.4 °C, showing a decline as temperatures further increase. Meanwhile, the fEON gradually decreases with MAT, stabilizing at about 20% when the MAT exceeds 15 °C. These results clarify global plant N-use patterns and reveal temperature rather than human N loading as a key regulator, which should be considered in evaluating influences of global changes on terrestrial ecosystems.
摘要：
土壤可提取硝酸盐，铵，有机氮（N）是支持初级生产力和调节陆生植物物种组成的重要氮源。然而,目前尚不清楚植物如何利用这些氮源以及地表环境如何调节植物氮的利用。这里,我们建立了一个框架来分析全球植物和土壤中天然氮同位素的观测数据，我们量化了土壤硝酸盐(fNO3-)的分数贡献，铵（fNH4+），和有机氮(fEON)到土壤中植物使用的氮。我们发现年平均温度(MAT)，不意味着年降水量或大气氮沉积，调节fNO3-的全球变化，fNH4+,和FEON。fNO3-随MAT增加，在28.5°C时达到46%。fNH4+也随着MAT的增加而增加，在14.4°C时达到最大46%，随着温度的进一步升高，呈现下降趋势。同时,fEON随着MAT逐渐降低,当MAT超过15°C时稳定在约20%。这些结果阐明了全球植物氮素使用模式，并揭示了温度而不是人类氮素负荷作为关键调节剂，在评估全球变化对陆地生态系统的影响时应予以考虑。
