title: Soil nutrient content influences the abundance of soil microbes but not plant biomass at the small-scale.
abstract: Small-scale heterogeneity of abiotic and biotic factors is expected to play a crucial role in species coexistence. It is known that plants are able to concentrate their root biomass into areas with high nutrient content and also acquire nutrients via symbiotic microorganisms such as arbuscular mycorrhizal (AM) fungi. At the same time, little is known about the small-scale distribution of soil nutrients, microbes and plant biomass occurring in the same area. We examined small-scale temporal and spatial variation as well as covariation of soil nutrients, microbial biomass (using soil fatty acid biomarker content) and above- and belowground biomass of herbaceous plants in a natural herb-rich boreonemoral spruce forest. The abundance of AM fungi and bacteria decreased during the plant growing season while soil nutrient content rather increased. The abundance of all microbes studied also varied in space and was affected by soil nutrient content. In particular, the abundance of AM fungi was negatively related to soil phosphorus and positively influenced by soil nitrogen content. Neither shoot nor root biomass of herbaceous plants showed any significant relationship with variation in soil nutrient content or the abundance of soil microbes. Our study suggests that plants can compensate for low soil phosphorus concentration via interactions with soil microbes, most probably due to a more efficient symbiosis with AM fungi. This compensation results in relatively constant plant biomass despite variation in soil phosphorous content and in the abundance of AM fungi. Hence, it is crucial to consider both soil nutrient content and the abundance of soil microbes when exploring the mechanisms driving vegetation patterns.
authors.affiliation: Department of Botany, Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia.
authors.forename: Kadri
authors.initials: K
authors.lastname: Koorem
authors.affiliation: Department of Botany, Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia.
authors.forename: Antonio
authors.initials: A
authors.lastname: Gazol
authors.affiliation: Department of Botany, Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia.
authors.forename: Maarja
authors.initials: M
authors.lastname: Öpik
authors.affiliation: Department of Botany, Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia.
authors.forename: Mari
authors.initials: M
authors.lastname: Moora
authors.affiliation: Department of Botany, Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia.
authors.forename: Ülle
authors.initials: Ü
authors.lastname: Saks
authors.affiliation: Department of Botany, Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia.
authors.forename: Annika
authors.initials: A
authors.lastname: Uibopuu
authors.affiliation: Department of Zoology, Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia.
authors.forename: Virve
authors.initials: V
authors.lastname: Sõber
authors.affiliation: Department of Botany, Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia.
authors.forename: Martin
authors.initials: M
authors.lastname: Zobel
mesh_terms: D018533:Biomass; D017753:Ecosystem; D004957:Estonia; D065928:Forests; D018517:Plant Roots / Q000254:growth & development* / Q000382:microbiology*; D012621:Seasons; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology; D013559:Symbiosis
chemical_list: D012987:Soil