Effects of fertilization and cutting frequency on the water balance of a temperate grassland

Abstract

In large areas of Central Europe, grassland management has shifted from extensive grazing and mowing to highly intensive systems during the past 50 years. Although effects on biodiversity have intensively been studied, little is known about the response of important ecosystem functions, in particular, water and nutrient cycling, to management intensification. We conducted a two‐factorial grassland management experiment (GRASSMAN) with two cutting frequencies (one/three cuttings per year) and two fertilization levels (non‐fertilized/N‐fertilized) in a moderately species‐rich temperate grassland to analyse the effects of management regimes on evapotranspiration (ET) and infiltration (I). Both were measured in the growing season 2009 with small, weighable lysimeters that contained undisturbed soil monoliths and vegetation. Aboveground biomass production (ANPP), belowground biomass, root length density, plant diversity, water use efficiency (WUE), and climatic factors were also measured. Fertilization with 180 kg N ha−1yr−1 increased aboveground biomass production by 50–70% and stand ET by 10–15% (or 20–40 mm), whereas I and ground water recharge decreased by about 50%. Consequently, fertilization increased the WUE of the grassland plants by 20–30%. However, increasing the mowing frequency from 1 to 3 had no significant effect. We found close relations between ANPP, ET and I and conclude that grassland management intensification influences the water balance primarily through fertilization effects on productivity. In areas of Central Europe with abundant grassland, ground water recharge must have significantly decreased with management intensification in the past 50 years.