Preprints
https://doi.org/10.5194/gmd-2022-176
https://doi.org/10.5194/gmd-2022-176
Submitted as: model description paper
25 Aug 2022
Submitted as: model description paper | 25 Aug 2022
Status: this preprint is currently under review for the journal GMD.

Modeling the role of livestock grazing in C and N cycling in grasslands with LPJmL5.0-grazing

Jens Heinke, Susanne Rolinski, and Christoph Müller Jens Heinke et al.
  • Potsdam Institute for Climate Impact Research (PIK), member of the Leibniz Association, P.O. Box 60 12 03, 14412 Potsdam, Germany

Abstract. Grazing livestock alter the fluxes of carbon (C) and nitrogen (N) in grasslands. We implement a livestock module representing grazing dairy cows into LPJmL5.0-tillage, a global vegetation and crop model with explicit representation of managed grasslands and pastures, forming LPJmL5.0-grazing. The new module explicitly accounts for feed quality on dry matter intake and feed digestibility using relationships derived from compositional analyses for different forages. Partitioning of N into milk, feces, and urine are simulated by the new livestock module shows very good agreement with observation-based relationships reported in the literature. Modeled C and N dynamics depend on feed quality (C:N ratios in grazed biomass), feed quantity, livestock densities, manure or fertilizer inputs, soil, atmospheric CO2 concentrations, and climate conditions. Due to the many interacting relationships, C sequestration or emission rates as well as N losses and N use efficiency (NUE) show substantial variation in space and across livestock densities. The improved LPJmL5.0-grazing model can now assess the effects of management and climate change on grazing dairy productivity, C dynamics and N losses. Optimal stocking densities can be derived per location for different optimization targets, such as maximization of milk production, lowest emission intensity, best NUE, or highest C sequestration.

Jens Heinke et al.

Status: open (until 27 Oct 2022)

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  • RC1: 'Comment on gmd-2022-176', Anonymous Referee #1, 24 Sep 2022 reply

Jens Heinke et al.

Jens Heinke et al.

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Short summary
We develop a livestock module for the global vegetation model LPJmL5.0 to simulate the impact of grazing dairy cattle on carbon and nitrogen cycles in grasslands. A novelty of the approach is that it accounts for the effect of feed quality on feed uptake and feed utilisation by animals. The portioning of dietary nitrogen into milk, feces, and urine shows very good agreement with estimates obtained from animal trials.