Fine‐Scale Estimation of Urban Biogenic CO2 Fluxes: A Novel Framework Integrating Multiple Versions of Vegetation Photosynthesis and Respiration Models and In Situ Measurements

[Geoengineering News]

https://agupubs.onlinelibrary.wiley.com/doi/pdfdirect/10.1029/2025EF007458

Authors: Junwei Li , Jia Chen, Theo Glauch, Dominik Brunner, Julia Marshall, Nikolai Ponomarev, Haoyue Tang, and Stavros Stagakis

03 February 2026

Abstract

Estimating biogenic CO2 fluxes is essential to quantify urban anthropogenic emissions, yet urban vegetation heterogeneity presents a significant challenge to making accurate estimations. We have developed an hourly temporal, 10‐m spatial resolution biogenic CO2 flux estimation framework based on the Vegetation Photosynthesis and Respiration Model (VPRM) and its variants (UrbanVPRM and VPRM‐modified). Unlike lower‐resolution models, our approach captures finer‐scale variability, particularly in fragmented urban green spaces like street trees and lawns. Results show that vegetation in Munich offsets 2.0%–2.8% of annual anthropogenic CO2 emissions in the study domain, with tree‐covered areas as primary sinks and grasslands as net sources. During summer, daytime CO2 uptake can match or exceed anthropogenic emissions.

Evaluations employing city park field measurements and eddy covariance towers confirm strong performance of our models, while highlighting VPRM‐modified's advantage in grasslands and croplands, and UrbanVPRM's improvements in urban areas via impervious surface correction. These findings highlight the value of high‐resolution modeling in improving urban carbon flux assessments.

Plain Language Summary 

Cities are emitters of carbon dioxide (CO2) from human activities like traffic and heating, but green spaces like lawns and street trees also absorb and release CO2. To accurately calculate how much CO2 humans are truly responsible for, we need to precisely estimate the CO2 exchange from the city's complex and varied vegetation. To solve this, we developed a framework to map this vegetation CO2 exchange in Munich and Zurich, creating hour‐by‐hour estimates at a fine 10‐m resolution, which can resolve the impact of small green patches, like individual street trees and lawns. This high‐resolution approach is further validated against our field measurements from city parks and tower measurements from rural areas. Results show that Munich's vegetation offsets about 2.0%–2.8% of its annual human‐caused CO2 emissions. Tree‐covered areas are the primary sinks that absorb CO2, while grasslands tend to be minor sources that release it. Remarkably, the greenery's CO2 absorption on a summer day can temporarily outweigh Munich's entire human emissions. This transferable framework enables an accurate evaluation of the carbon sequestration benefits of urban green infrastructure, ultimately providing policymakers with precise data to support more effective climate strategies and urban planning policies.

Source: AGU