Soil microbial community structure and function relationships: A heat stress experiment Wassila Riah-Anglet a, *, Isabelle Trinsoutrot-Gattin a , Fabrice Martin-Laurent b , Emilie Laroche-Ajzenberg a , Marie-Paule Norini a , Xavier Latour c , Karine Laval a a Unité Agri'Terr, Esitpa, 3 rue du Tronquet 76134, Mont Saint Aignan, France b INRA, UMR Agroécologie, Écologie des Communautés et Durabilité Systèmes Agricoles, Centre de Dijon, 17 rue Sully BP 86510, 21065 Dijon cedex, France c Laboratoire de Microbiologie Signaux et Microenvironnement (LMSM EA 4312) Normandie Université - Université de Rouen - IUT Evreux, Evreux, France A R T I C L E I N F O Article history: Received 5 May 2014 Received in revised form 25 September 2014 Accepted 1 October 2014 Available online xxx Keywords: Microbial diversity Bacterial taxa Enzymatic activities Heat stress Soil land use A B S T R A C T Links between the microbial community structure and soil functions are unclear. The study of these relationships requires the development of highly specific experimental approaches. In this work, the soil microbial community structure and function relationship was evaluated in relation to heat stress in a soil microcosm incubated at 17  C and 50  C. We selected a luvisol that included two land uses. Samples were taken from the soil of a long-term (>10 year) arable cropping plot (CC) and a permanent grassland (PG) (>25 years). The soil functions were evaluated by measuring the enzyme activities, including cellulase, N-acetyl-glucosaminidase, b-glucosidase, xylanase and dehydrogenase. The total microbial biomass was assayed by the quantification of the total DNA extracted from the microcosm soils. The abundance of total bacterial and fungal communities and different bacterial taxa were measured by qPCR rRNA genes. For both soil types, heat stress induced changes in the microbial community structure and soil functions. In most cases, the results yielded effects following heat treatment. All of the enzymes were inhibited except xylanase. Heat stress significantly reduced the total microbial biomass and fungal abundance in the soils. The abundance of the total bacterial community was not affected by heat stress. In the two soils, the dominant taxa were Actinobacteria (13–40%) and Bacteroidetes (14–32%), while Planctomycetes and Gammaproteobacteria exhibited lower abundance (0–3%). Changes in the microbial community structure and changes in the functions were correlated; the correlation was positive in the PG soil and negative in the CC soil. The changes in the CC soil structural and functional state were greater than of those observed in PG soil. Our initial hypothesis was confirmed, indeed, grassland soil is more resistant to drastic stress due to its highly abundant and highly diversified microbial community. These results represent a contribution to the understanding of soil microbial community structure and functions relationships. ã 2014 Elsevier B.V. All rights reserved. 1. Introduction Soils are considered the primary reservoirs of biodiversity (Jangid et al., 2010). Among this biodiversity, microflora represents a considerable fraction, which is highly diversified (Torsvik et al., 1990; Allison and Martiny, 2008). A large number of studies have documented how the microbial community struc- ture, or the different types of microorganisms and their abundances (Fuhrman, 2009), constitute an essential element for understanding the impacts of environmental and anthropo- genic perturbations on soil functioning (Nannipieri et al., 2003). However, the close relationship between the structure of microbial communities and soil functions remain poorly understood because of functional redundancy of microbial communities. Yin et al. (2000) defined the functional redundancy as the potential for multiple species to be able to perform the same function and thus, changes in the microbial community structure do not necessarily lead to a change in soil functioning (Chapin et al., 1997). Microbial species that appear after an environmental stress or disruption but harbor the same ability to perform a function might (i) not have the same growth rate or competitive ability compared with the original community * Corresponding author. Tel.: +33 232829198. E-mail address: wriah@esitpa.fr (W. Riah-Anglet). http://dx.doi.org/10.1016/j.apsoil.2014.10.001 0929-1393/ ã 2014 Elsevier B.V. All rights reserved. Applied Soil Ecology 86 (2014) 121–130 Contents lists available at ScienceDirect Applied Soil Ecology journal homepage: www.elsevier.com/locate/apsoil