Direct and plant community mediated effects of management intensity on annual nutrient leaching risk in temperate grasslands

Nutr Cycl Agroecosyst https://doi.org/10.1007/s10705-022-10209-1 ORIGINAL ARTICLE Direct and plant community mediated effects of management intensity on annual nutrient leaching risk in temperate grasslands Antonios Apostolakis · Ingo Schöning · Valentin H. Klaus · Beate Michalzik · Wolf‑Anno Bischoff · Runa S. Boeddinghaus · Ralph Bolliger · Markus Fischer · Norbert Hölzel · Ellen Kandeler · Till Kleinebecker · Peter Manning · Sven Marhan · Margot Neyret · Yvonne Oelmann · Daniel Prati · Mark van Kleunen · Andreas Schwarz · Elisabeth Schurig · Marion Schrumpf Received: 27 September 2021 / Accepted: 21 May 2022 © The Author(s) 2022 Abstract Grassland management intensity influences nutrient cycling both directly, by changing nutrient inputs and outputs from the ecosystem, and indirectly, by altering the nutrient content, and the diversity and functional composition of plant and microbial communities. However, the relative importance of these direct and indirect processes for the leaching of multiple nutrients is poorly studied. We measured the annual leaching of nitrate, ammonium, Supplementary Information The online version contains supplementary material available at https://doi. org/10.1007/s10705-022-10209-1. phosphate and sulphate at a depth of 10 cm in 150 temperate managed grasslands using a resin method. Using Structural Equation Modeling, we distinguished between various direct and indirect effects of management intensity (i.e. grazing and fertilization) on nutrient leaching. We found that management intensity was positively associated with nitrate, ammonium and phosphate leaching risk both directly (i.e. via increased nutrient inputs) and indirectly, by changing the stoichiometry of soils, plants and microbes. In contrast, sulphate leaching risk was negatively associated with management intensity, presumably due to increased outputs with mowing A. Apostolakis (*) · I. Schöning · M. Schrumpf Max-Planck-Institute for Biogeochemistry, Hans‑Knöll‑Str. 10, 07745 Jena, Germany e-mail: R. S. Boeddinghaus · E. Kandeler · S. Marhan Institute of Soil Science and Land Evaluation, Soil Biology Department, University of Hohenheim, 70599 Stuttgart, Germany A. Apostolakis · B. Michalzik Department of Soil Science, Friedrich Schiller University Jena, Löbdergraben 32, 07743 Jena, Germany R. Bolliger · M. Fischer · D. Prati Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland V. H. Klaus Institute of Agricultural Sciences, ETH Zürich, Universitätstr. 2, 8092 Zurich, Switzerland N. Hölzel Institute of Landscape Ecology, University of Münster, Heisenbergstr. 2, 48149 Münster, Germany B. Michalzik German Centre for Integrative Biodiversity Research (iDiv) Halle -Jena-Leipzig, Deutscher Platz 5e, 04103 Leipzig, Germany T. Kleinebecker Institute of Landscape Ecology and Resource Management, Justus-Liebig-University Gießen, Heinrich‑Buff‑Ring 26‑32, 35392 Gießen, Germany W.-A. Bischoff · A. Schwarz TerrAquat GmbH, Schellingstr. 43, 72622 Nürtingen, Germany Vol.: (0123456789) 13 Nutr Cycl Agroecosyst and grazing. In addition, management intensification shifted plant communities towards an exploitative functional composition (characterized by high tissue turnover rates) and, thus, further promoted the leaching risk of inorganic nitrogen. Plant species richness was associated with lower inorganic nitrogen leaching risk, but most of its effects were mediated by stoichiometry and plant community functional traits. Maintaining and restoring diverse plant communities may therefore mitigate the increased leaching risk that management intensity imposes upon grasslands. Keywords Annual nutrient leaching · Inorganic nitrogen · Phosphate · Sulphate · Temperate grasslands · Grassland management Introduction Grasslands are widespread and highly diverse ecosystems providing a multitude of ecosystem functions and services, including nutrient cycling and food production (Bengtsson et al. 2019). Management intensification of grassland ecosystems places them at considerable risk of nutrient losses via leaching, especially for nitrate (Klaus et al. 2018 and references therein), which represent the loss of important resources and, at the same time, potential threats to human health and aquatic ecosystems (EEA 2018; EU-Nitrate Directive 2018; WHO 2011). Compared to nitrogen (N), management effects on leaching of other elements, like phosphorus (P) and sulphur (S), are less studied in grasslands, despite their agricultural and environmental importance (Eriksen 2009; P. Manning · M. Neyret Senckenberg Biodiversity and Climate Research Centre (SBiK-F), Senckenberganlage 25, 60325 Frankfurt, Germany Y. Oelmann · E. Schurig Geoecology, University of Tübingen, Rümelinstr. 19‑23, 72070 Tübingen, Germany M. van Kleunen Department of Biology, University of Konstanz, 87464 Constance, Germany M. van Kleunen Zhejiang Provincial Key Laboratory of Plant Evolutionary Ecology and Conservation, Taizhou University, Taizhou 318000, China Vol:. (1234567890) 13 Withers et al. 2014; Gallejones et al. 2012). Unravelling the relationships between ecosystem management, biotic drivers and nutrient leaching will provide important insights for sustainable grassland management and could help secure associated ecosystem services. In unfertilized grasslands, inorganic nutrients that are available for leaching represent the net balance between nutrient inputs to the soil solution (e.g. by organic matter mineralization or dissolution) and outputs from the soil solution (e.g. due to uptake by plants, or immobilization in microbial biomass), as well as nutrient exchange with the soil matrix (i.e. via (de)sorption to minerals). Management, such as fertilization and grazing, changes these relations by increasing both inputs and outputs of nutrients from the ecosystem. In the past, grasslands were considered to have low N leaching fluxes, and introducing temporary (mowed) grasslands in arable crop rotations can even reduce nitrate leaching (Kunrath et al. 2015). However, studies investigating the effects of grassland management on soil nitrate show increased leaching risk in pastures compared to meadows (Di and Cameron 2002; Ryden et al. 1984), and when broader management gradients are included, both fertilization and grazing equally increase nitrate leaching risk (Klaus et al. 2018). Grassland intensification can affect nutrient cycling directly by changing inputs and outputs (i.e. fertilization, grazing and harvest, Rumpel et al. 2015) and indirectly by changing plant communities (e.g. loss of diversity or functional change) and altering interactions between soils, plants and soil microorganisms (de Vries et al. 2012; Klaus et al. 2018). However, at present, it is unclear if management intensity predominantly drives leaching risk directly and/or indirectly by changing plant and/or microbial communities. Grassland management, mainly fertilization, mowing and grazing, influences soil, (...truncated)