Modeling Carbon and Water Fluxes of Managed Grasslands: Comparing Flux Variability and Net Carbon Budgets between Grazed and Mowed Systems

Abstract

The CenW ecosystem model simulates carbon, water, and nitrogen cycles following ecophysiological processes and management practices on a daily basis. We tested and evaluated the model using five years eddy covariance measurements from two adjacent but differently managed grasslands in France. The data were used to independently parameterize CenW for the two grassland sites. Very good agreements, i.e., high model efficiencies and correlations, between observed and modeled fluxes were achieved. We showed that the CenW model captured day-to-day, seasonal, and interannual variability observed in measured CO2 and water fluxes. We also showed that following typical management practices (i.e., mowing and grazing), carbon gain was severely curtailed through a sharp and severe reduction in photosynthesizing biomass. We also identified large model/data discrepancies for carbon fluxes during grazing events caused by the noncapture by the eddy covariance system of large respiratory losses of C from dairy cows when they were present in the paddocks. The missing component of grazing animal respiration in the net carbon budget of the grazed grassland can be quantitatively important and can turn sites from being C sinks to being neutral or C sources. It means that extra care is needed in the processing of eddy covariance data from grazed pastures to correctly calculate their annual CO2 balances and carbon budgets.

Ensemble modelling, uncertainty and robust predictions of organic carbon in long‐term bare‐fallow soils

“…Puche et al. (2019) performed a similar study in France. Using multi‐model ensembles in scenario studies at eight sites worldwide, Basso et al.…”

Climate Changes Challenges to the Management of Mediterranean Montado Ecosystem: Perspectives for Use of Precision Agriculture Technologies

“…Montado ecosystems are particularly complex and difficult to study because of the wide range of management and environmental conditions that they are exposed to [3]. The results of this study demonstrated the effect of trees and their importance in the dynamics of soil nutrients in agro-silvo-pastoral systems and highlighted the importance of optimizing the management of pasture and animal grazing as a potential measure for mitigating climate change in Mediterranean regions.…”

“…This system is characterized by a high complexity resulting from the interactions between climate, soil, pasture, trees, and animals [2]. Montado and pasture production are very important farming systems since, in Portugal, this ecosystem represents 33% of total forest area [2] and in Europe, grasslands cover 22% of the land area [3]. Since the turn of the new millennium, greater recognition of the importance of grasslands in conserving soil, promoting biodiversity, stabilizing farming communities, and providing a wealth of natural ecosystem services has led to renewed interest in the dynamics of grasslands function [4].…”

Grassland Management for Sustainable Agroecosystems

“…At the same time, models need to be tested and verified against real-world observations to build confidence in their ability to accurately describe the patterns we are interested in, in particular, the effect of different management options in enhancing soil organic carbon storage without compromising pasture productivity. The contribution from Puche et al [25] is a modeling work on mown and grazed paddocks in France, equipped with eddy-covariance (EC) measuring systems. The model used, CenW, confirms the difficulty of simulating grazing systems where EC devices may not completely detect C losses.…”