Carbon dioxide fluxes and carbon balance of an agricultural grassland in southern Finland

Abstract

Abstract. A significant proportion of the global carbon emissions to the atmosphere originates from agriculture. Therefore, continuous long-term monitoring of CO2 fluxes is essential to understand the carbon dynamics and balances of different agricultural sites. Here we present results from a new eddy covariance flux measurement site located in southern Finland. We measured CO2 and H2O fluxes at this agricultural grassland site for two years from May 2018 to May 2020. Especially the first summer experienced prolonged dry periods, which affected the CO2 fluxes, and substantially larger fluxes were observed in the second summer. During the dry summer, leaf area index (LAI) was notably lower than in the second summer. Water use efficiency increased with LAI in a similar manner in both years, but photosynthetic capacity per leaf area was lower during the dry summer. The annual carbon balance was calculated based on the CO2 fluxes and management measures, which included input of carbon as organic fertilisers and output as yield. The carbon balance of the field was −50 ± 68 g C m−2 yr−1 and −118 ± 24 g C m−2 yr−1 during the first and second study year, respectively. We estimated that on average the grassland exceeded the global 4 per 1000 goal to increase the soil carbon content.

Measurement report: Atmospheric new particle formation in a coastal agricultural site explained with binPMF analysis of nitrate CI-APi-TOF spectra

“…Since 2017, sustainable and environmentally friendly field management practices have been conducted at the farm. More detailed information on the location, species, and management practices of Qvidja can be found in Heimsch et al (2021).…”

Towards agricultural soil carbon monitoring, reporting, and verification through the Field Observatory Network (FiON)

“…Focusing the sampling on georeferenced locations and using composite sampling reduces the overall sampling variability and allows tracking relatively small (4 % of background level) changes in SOC stock (Knebl et al, 2015). The offline field measurements at the intensive site Qvidja are described in Heimsch et al (2021).…”

“…The measurement heights fulfill guidelines for grasslands and croplands defined by the Integrated Carbon Observation System (ICOS; Sabbatini and Papale, 2017). For details of the measurement setup in Qvidja, see Heimsch et al (2021).…”

Use, calibration and verification of agroecological models for boreal environments: A review

“…Since the 1970s, global grasslands have been estimated to transition from an anthropogenic sink to a source of anthropogenic GHG (Chang, Ciais, et al, 2015; Chang et al, 2021) due to increased livestock numbers and conversion of natural grasslands to improved pastures, according to a global modelling assessment. Nevertheless, boreal grasslands studies have concluded to either carbon sinks (Heimsch et al, 2021; Kätterer et al, 2011; Poeplau et al, 2015) or sources (Heikkinen et al, 2013; Lind et al, 2020; Lohila, 2004). Thus, a useful avenue of research is to reduce this uncertainty and assess if boreal grasslands are collectively either a net source or sink of CO 2 , both historically and in the future.…”