Annual balances and extended seasonal modelling of carbon fluxes from a temperate fen cropped to festulolium and tall fescue under two‐cut and three‐cut harvesting regimes

Abstract

Annual balances and extended seasonal modelling of carbon fluxes from a temperate fen cropped to festulolium and tall fescue under two-cut and three-cut harvesting regimes AbstractThis study reports the annual carbon balance of a drained riparian fen under two-cut or three-cut managements of festulolium and tall fescue. CO 2 fluxes measured with closed chambers were partitioned into gross primary production (GPP) and ecosystem respiration (ER) for modelling according to environmental factors (light and temperature) and canopy reflectance (ratio vegetation index, RVI). Methodological assessments were made of (i) GPP models with or without temperature functions (Ft) to adjust GPP constraints imposed by low temperature (<10°C) and (ii) ER models with RVI or GPP parameters as biomass proxies. The sensitivity of the models was also tested on partial datasets including only alternate measurement campaigns and on datasets only from the crop growing period. Use of Ft in GPP models effectively corrected GPP overestimation in cold periods, and this approach was used throughout. Annual fluxes obtained with ER models including RVI or GPP parameters were similar, and also annual GPP and ER fluxes obtained with full and partial datasets were similar. Annual CO 2 fluxes and biomass yield were not significantly different in the crop/management combinations although the individual collars (n = 12) showed some variations in GPP (À1818 to À2409 g CO 2 -C m À2 ), ER (1071 to 1738 g CO 2 -C m À2 ), net ecosystem exchange (NEE, À669 to À949 g CO 2 -C m À2 ) and biomass yield (556 to 1044 g CO 2 -C m À2 ). Net ecosystem carbon balance (NECB), as the sum of NEE and biomass carbon export, was only slightly negative to positive in all crop/management combinations. NECBs, interpreted as emission factors, tended to favour the least biomass producing systems as the best management options in relation to climate saving carbon balances. Yet, considering the down-stream advantages of biomass for fossil fuel replacement, yieldscaled carbon fluxes are suggested to be given additional considerations for comparison of management options in terms of atmospheric impact.

Mapping of Peat Thickness Using a Multi-Receiver Electromagnetic Induction Instrument

“…The field mainly comprises organic soil areas and small zones with mineral soils (coarse sand). This site is considered as a riparian fen peatland [34] where vascular plants such as reeds and sedges dominate [12]. As will be discussed later, and similar to Walter et al [12] (2015), its specific configuration, underlain by sandy soils characterized by low electrical conductivity, ensured a contrast with the peat layers, which generally present higher electrical conductivity.…”

Identifying criteria for greenhouse gas flux estimation with automatic and manual chambers: A case study for N2O

“…These guidelines are needed to guide the user of the HMR package to analyse the recorded data consistently to achieve the best possible flux calculations. Differences between sampling systems may be inherent to the sampling methodology, chamber design (probably a minor factor in our study because the chamber dimensions were relatively similar for both systems), length of deployment (Kandel et al, 2017) and the number of data points (Hüppi et al, 2018;Parkin et al, 2012). Both older and more recent studies of N 2 O emissions from soil have used linear regression as the only way to calculate N 2 O fluxes (Christensen et al, 2021;Guo et al, 2021;Pugesgaard et al, 2017;Smith & Dobbie, 2001).…”

Effects of cutting frequency of tall fescue on cadmium form in soil and cadmium enrichment in the plant

“…Higher concentrations of heavy metals resulted in more obvious inhibitory effects. Some studies have found that proper cutting methods stimulate root activity and promote the growth of aboveground plants (Kandel, Elsgaard, & Lærke, 2017). However, our results indicated that the cutting method reduced the biomass of tall fescue under Cd stress because the increased cutting treatment promoted the absorption of Cd by the plant, which caused the high concentration of Cd in the plant to affect the physiological activity of plants (Dias et al., 2013).…”