The added value of including key microbial traits to determine nitrogen‐related ecosystem services in managed grasslands

Abstract

Abstract1. Despite playing central roles in nutrient cycles and plant growth, soil microbes are generally neglected in the study of ecosystem services (ES), due to difficulties to assess their diversity and functioning. However, to overcome these hurdles, new conceptual approaches and modern tools now provide a means to assess the role of micro-organisms in the evaluation of ES.2. In managed grasslands, soil microbes are central in providing nitrogen (N)-related ES such as maintenance of soil fertility and retention of mineral forms of N. Here, we applied state-of-the-art techniques in microbial ecology and plant functional ecology to uncover the intrinsic link between N-related bacterial functional groups, important plant functional traits, environmental factors and three proxies of maintenance of soil fertility and potential for N-leaching across managed grasslands in three regions of Europe.3. By constructing well-defined structural equation modelling, we showed that including key microbial traits improve on average more than >50% of the total variances of ES proxies, that is, ammonium (NH + 4 ) or nitrate (NO − 3 ) leaching, and soil organic matter content. Geographic differences arose when considering the direct relationships of these ES proxies with specific microbial traits: nitrate leaching was positively correlated to the maximum rate of nitrification, except in the Austrian site and potentially leached NH | Rationale of key microbial traits involved in two soil ESWe propose here a conceptual framework that integrate solid knowledge on the relationships between above-ground and F I G U R E 1 A priori model for three proxies of the maintenance of soil fertility and water quality (light grey boxes) and their relationships with microbial (white boxes) and plant (dark grey boxes) functional traits and soil characteristics (black boxes). Arrows indicate either positive or negative relationships, depending on the considered variables Zumft & Korner, 1997). Nitrification is a less common autotrophic process that is driven mostly by soil ammonium concentrations and soil water content (Patra et al., 2007;Prosser, 1989). These two important processes of the soil N-cycle are obviously driven by the relative abundances of functional groups performing key enzymatic steps, that is, nitrite and nitrate reducers for denitrification and ammonium and nitrite oxidizers for nitrification. Ultimately, the variations of potential leaching of ammonium and nitrate, as well as SOM content variance, are related to the different biotic and abiotic drivers described above.Here, to estimate the relative contribution of microbes to nitrogen-related ES in mountain managed grasslands, we applied this conceptual framework to eight different sampling fields across Europe. This broad perspective documents such dynamics in different grass-based agroecosystem under common climatic conditions of the Northern Hemisphere. We tested the hypothesis that integrating the measures of microbial traits would significantly improve the amount of var...

Plant functional groups mediate drought resistance and recovery in a multisite grassland experiment

“…Our findings did not support this hypothesis. Although the abundance of bacterial groups increased with increasing CP across our study sites and fungi abundance was within the range of other grassland studies (Bardgett & McAlister, ; Karlowsky et al, ; Pommier et al, ), microbial drought resistance was unrelated to CP. In addition, neither CP nor microbial community structure showed any relationship with the drought resistance of plant biomass, suggesting that these two biotic factors play a limited role for variation in plant drought resistance.…”

Functional traits in agroecology: Advancing description and prediction in agroecosystems

“…Pommier et al. () address both of these themes, by offering a robust example of how a functional trait‐based approach provides new insights into our understanding and prediction of linkages between microbial diversity and nutrient cycles. Pommier et al.…”

“…Pommier et al. () distil trait‐mediated interactions among plant and microbial species that affect nitrogen (N) dynamics in European‐managed grasslands agroecosystems, showing that variation in nitrate and ammonium leaching and soil organic matter content is largely explained by microbial traits including the maximum rate of nitrification and fungi: bacteria ratios. To date, this contribution by Pommier et al.…”

“…To date, this contribution by Pommier et al. () is among very few studies that incorporate diversity of microbial traits with soil and plant metrics, representing an important advancement in the understanding of microbial‐controlled ecosystem services in agroecosystems.…”

Evaluating the stoichiometric trait distributions of cultured bacterial populations and uncultured microbial communities

“…Responses to the environment manifest as a suite of measurable morphological, physiological and behavioural characteristics referred to as traits (Mason et al, 2005;Schleuter et al, 2010;Carmona et al, 2016). The study of microbial traits (phenotypes of ecological importance that may or may not be phylogenetically conserved) and their inclusion into ecosystem models provide a path to improve our understanding of microbial influences over system-level processes (McGuire and Treseder, 2010;Wallenstein and Hall, 2012;Fontana et al, 2017;Pommier et al, 2018). However, due to technological and methodological challenges, estimates of microbial traits often lack a consideration of the variation within microbial communities or populations.…”