Soil Nitrogen Dynamics in a Managed Temperate Grassland Under Changed Climatic Conditions

Abstract

Grasslands are one of the most common biomes in the world with a wide range of ecosystem services. Nevertheless, quantitative data on the change in nitrogen dynamics in extensively managed temperate grasslands caused by a shift from energy- to water-limited climatic conditions have not yet been reported. In this study, we experimentally studied this shift by translocating undisturbed soil monoliths from an energy-limited site (Rollesbroich) to a water-limited site (Selhausen). The soil monoliths were contained in weighable lysimeters and monitored for their water and nitrogen balance in the period between 2012 and 2018. At the water-limited site (Selhausen), annual plant nitrogen uptake decreased due to water stress compared to the energy-limited site (Rollesbroich), while nitrogen uptake was higher at the beginning of the growing period. Possibly because of this lower plant uptake, the lysimeters at the water-limited site showed an increased inorganic nitrogen concentration in the soil solution, indicating a higher net mineralization rate. The N2O gas emissions and nitrogen leaching remained low at both sites. Our findings suggest that in the short term, fertilizer should consequently be applied early in the growing period to increase nitrogen uptake and decrease nitrogen losses. Moreover, a shift from energy-limited to water-limited conditions will have a limited effect on gaseous nitrogen emissions and nitrate concentrations in the groundwater in the grassland type of this study because higher nitrogen concentrations are (over-) compensated by lower leaching rates.

Coupled modelling of hydrological processes and grassland production in two contrasting climates

“…Likewise, harvested biomass at Selhausen was similar in all three replicate lysimeters, whereas it varied more at Rollesbroich, with one lysimeter clearly an outlier (Ro_Y_013, Table 2). Much larger nitrate nitrogen concentrations were consistently found at the beginning of the experiment in the leachate from this lysimeter (Giraud et al 2021), which suggests that the larger harvest from Ro_Y_013 may be due to a better nutrient supply from the soil. Table 2 and figure 2 show that the water use efficiency (WUE) of the grassland in the drier climate at Selhausen was smaller than for the lysimeters at Rollesbroich (Forstner et al, 2021), since harvests were somewhat smaller and evapotranspiration was larger.…”

Effect of slurry application techniques on nitrous oxide emission from temperate grassland under varying soil and climatic conditions

“…Depending on soil, climatic and land management factors, successive fertilizer application increases soil N content. Under high temperature and moisture conditions, elevated microbial activity and soil biogeochemical process rates may increase inorganic N concentration in soil solution with a positive residual effect for subsequent pasture production (Giraud et al, 2021). Furthermore, soils with relatively high total oxidized N and lower C/N ratio are associated with higher N uptake and DM yield response from SOM mineralization (McDonalds et al, 2014).…”

Effects of dry spells on soil moisture and yield anomalies at a montane managed grassland site: A lysimeter climate experiment

“…Likewise, the evaporative index was estimated by dividing the actual annual evapotranspiration ( ET a ) through the annual P . If AI < 1 evapotranspiration is limited by its demand for energy (energy limited), whereas for AI > 1 water is the limiting factor (water limited) (Giraud et al, 2021).…”

“…through the annual P. If AI < 1 evapotranspiration is limited by its demand for energy (energy limited), whereas for AI > 1 water is the limiting factor (water limited) (Giraud et al, 2021).…”