Work

Air Pollution and Climate Regulate the Large‐Scale Pattern of Foliar Nitrogen Uptake by Urban Street Trees

Year: 2026

Type: article

Abstract: ABSTRACT Urbanisation has fundamentally altered terrestrial nitrogen (N) cycling and created N‐enriched hotspots where street trees serve as essential green infrastructures. These street trees live in a distinctive environment with high‐level reactive N emissions and blocked soil N cycling, potentially relying on direct N uptake via stomata as an important N source. However, the spatial pattern and primary drivers governing this non‐root N uptake across broad climatic gradients remain elusive. Based on an analysis of leaf‐soil difference in stable isotope ratios (∆ δ 15 N, i.e., foliar δ 15 N‐topsoil δ 15 N) across 14 large cities in China, we show that urban street trees exhibit a V‐shaped latitudinal pattern of isotope‐inferred foliar N uptake, being independent of tree health status. Specifically, the strength of isotope‐inferred foliar N uptake increases from subtropical to warm temperate zones and then declines toward colder regions. The spatial pattern of foliar N uptake by urban street trees is jointly regulated by various air pollutants and total precipitation from May to August. Specifically, the isotope‐inferred foliar N uptake increases with higher road density (a surrogate for traffic NO X emissions) and air concentrations of NH 3 , O 3 and SO 2 , as well as lower precipitation. Intriguingly, the isotope‐inferred foliar N uptake shows a non‐monotonic response to CO 2 concentrations. Our results provide isotopic evidence for a distinctive N acquisition strategy of urban street trees and highlight significant anthropogenic effects on foliar N uptake in urbanised landscapes.

Source: Plant Cell & Environment

DOI: 10.1111/pce.70838

Authors: Tao He, Enzai Du, Yuehan Tian, Wim de Vries

Institutions: Beijing Normal University, Wageningen University & Research

Language: English

Topic: Soil Carbon and Nitrogen Dynamics

Subfield: Soil Science

Field: Agricultural and Biological Sciences

Domain: Life Sciences

SDGs: Sustainable cities and communities, Climate action

Open Access status: bronze

Funders: National Natural Science Foundation of China, Fundamental Research Funds for the Central Universities