Impacts of fertilization on grassland productivity and water quality across the European Alps under current and warming climate: insights from a mechanistic model

Abstract

Abstract. Alpine grasslands sustain local economy by providing fodder for livestock. Intensive fertilization is common to enhance their yields, thus creating negative externalities on water quality that are difficult to evaluate without reliable estimates of nutrient fluxes. We apply a mechanistic ecosystem model, seamlessly integrating land-surface energy balance, soil hydrology, vegetation dynamics, and soil biogeochemistry, aiming at assessing the grassland response to fertilization. We simulate the major water, carbon, nutrient, and energy fluxes of nine grassland plots across the broad European Alpine region. We provide an interdisciplinary model evaluation by confirming its performance against observed variables from different datasets. Subsequently, we apply the model to test the influence of fertilization practices on grassland yields and nitrate (NO3-) losses through leaching under both current and modified climate scenarios. Despite the generally low NO3- concentration in groundwater recharge, the variability across sites is remarkable, which is mostly (but not exclusively) dictated by elevation. In high-Alpine sites, short growing seasons lead to less efficient nitrogen (N) uptake for biomass production. This combined with lower evapotranspiration rates results in higher amounts of drainage and NO3- leaching to groundwater. Scenarios with increased temperature lead to a longer growing season characterized by higher biomass production and, consequently, to a reduction of water leakage and N leaching. While the intersite variability is maintained, climate change impacts are stronger on sites at higher elevations. The local soil hydrology has a crucial role in driving the NO3- use efficiency. The commonly applied fixed threshold limit on fertilizer N input is suboptimal. We suggest that major hydrological and soil property differences across sites should be considered in the delineation of best practices or regulations for management. Using distributed maps informed with key soil and climatic attributes or systematically implementing integrated ecosystem models as shown here can contribute to achieving more sustainable practices.

Responses of Diversity and Productivity to Organo-Mineral Fertilizer Inputs in a High-Natural-Value Grassland, Transylvanian Plain, Romania

“…Dry matter biomass increases as fertilizer doses increase. Significant biomass increases were also obtained by other researchers in this field [ 51 , 52 , 53 , 54 , 55 , 56 ]. Following this study, the use of fertilizers in moderate doses, namely the application of a 10 t/ha −1 manure or N 50 P 25 K 25 , will provide an increase in biomass and exert a minor influence on the diversity of grasslands, being close to the traditional use of grasslands in the Transylvanian Plain (our study area).…”

Gross primary productivity and water use efficiency are increasing in a high rainfall tropical savanna

“…The model can be used for distributed simulations at catchment scales or applied as one‐dimensional vertical model as was implemented in this study. A detailed description of T&C’s structure and process parameterizations is presented in Fatichi et al (2012) and it has been shown to have significant predictive capability across a range of ecosystems worldwide (e.g., Botter et al, 2021; Fatichi & Ivanov, 2014; Fatichi et al, 2012, 2014; Mastrotheodoros et al, 2017, 2020; Manoli et al, 2018; Paschalis et al, 2015).…”

The Energy and Mass Balance of Peruvian Glaciers

“…The physically based model Tethys-Chloris (T&C) is used to simulate the mass, energy, and water fluxes at the point scale at the five Peruvian study sites. T&C is a land surface model with an hourly time step that can resolve the surface energy balance, soil and vegetation dynamics, processes of runoff generation and flow routing, and the evolution of snow and ice packs (see Botter et al, 2021;Fatichi et al, 2012aFatichi et al, , 2012bFatichi &Pappas, 2017 andMastrotheodoros et al, 2020 for a description of the distributed model and its applications). For this study, we use it at the point scale for computation of the surface energy fluxes and snow and ice mass balance.…”