Global distribution and drivers of relative contributions among soil nitrogen sources to terrestrial plants.

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 (f), ammonium (f), and organic N (f) to plant-used N in soils.

Significant contributions of combustion-related sources to ammonia emissions.

Atmospheric ammonia (NH) and ammonium (NH) can substantially influence air quality, ecosystems, and climate. NH volatilization from fertilizers and wastes (v-NH) has long been assumed to be the primary NH source, but the contribution of combustion-related NH (c-NH, mainly fossil fuels and biomass burning) remains unconstrained. Here, we collated nitrogen isotopes of atmospheric NH and NH and established a robust method to differentiate v-NH and c-NH.

Plant nitrogen-use strategies and their responses to the urban elevation of atmospheric nitrogen deposition in southwestern China.

The elevation of nitrogen (N) deposition by urbanization profoundly impacts the structure and function of surrounding forest ecosystems. Plants are major biomass sinks of external N inputs into forests. Yet, the N-use strategies of forest plants in many areas remain unconstrained in city areas, so their responses and adapting mechanisms to the elevated N deposition are open questions.

A new isotope framework to decipher leaf-root nitrogen allocation and assimilation among plants in a tropical invaded ecosystem.

Exotic plant invasion is an urgent issue occurring in the biosphere, which can be stimulated by environmental nitrogen (N) loading. However, the allocation and assimilation of soil N sources between leaves and roots remain unclear for plants in invaded ecosystems, which hampers the understanding of mechanisms behind the expansion of invasive plants and the co-existence of native plants. This work established a new framework to use N concentrations and isotopes of soils, roots, and leaves to quantitatively decipher intra-plant N allocation and assimilation among plant species under no invasion and under the invasion of Chromolaena odorata and Ageratina adenophora in a tropical ecosystem of SW China.

Important contributions of non-fossil fuel nitrogen oxides emissions.

Since the industrial revolution, it has been assumed that fossil-fuel combustions dominate increasing nitrogen oxide (NO) emissions. However, it remains uncertain to the actual contribution of the non-fossil fuel NO to total NO emissions. Natural N isotopes of NO in precipitation (δN) have been widely employed for tracing atmospheric NO sources.