A pulse of summer precipitation after the dry season triggers changes in ectomycorrhizal formation, diversity, and community composition in a Mediterranean forest in California, USA

Takeshi Taniguchi,Kuni Kitajima,Norikazu Yamanaka,Greg W Douhan,Michael F Allen

doi:10.1007/s00572-018-0859-3

Takeshi Taniguchi, Kuni Kitajima + Show 3 more

Open Access

https://doi.org/10.1007/s00572-018-0859-3

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Journal: Mycorrhiza	Publication Date: Aug 13, 2018
Citations: 24	License type: open-access

Affiliation: University of California, Riverside, Tottori University

Abstract

Rapid responses of microbial biomass and community composition following a precipitation event have been reported for soil bacteria and fungi, but measurements characterizing ectomycorrhizal fungi remain limited. The response of ectomycorrhizal fungi after a precipitation event is crucial to understanding biogeochemical cycles and plant nutrition. Here, we examined changes in ectomycorrhizal formation, diversity, and community composition at the end of a summer drought and following precipitation events in a conifer–oak mixed forest under a semiarid, Mediterranean-type climate in CA, USA. To study the effects of different amounts of precipitation, a water addition treatment was also undertaken. Ectomycorrhizal fungal diversity and community composition changed within 6 days following precipitation, with increased simultaneous mortality and re-growth. Ectomycorrhizal diversity increased and community composition changed both in the natural rainfall (less than 10 mm) and water addition (50 mm) treatments, but larger decreases in ectomycorrhizal diversity were observed from 9 to 16 days after precipitation in the water addition treatment. The changes were primarily a shift in richness and abundance of Basidiomycota species, indicating higher drought sensitivity of Basidiomycota species compared with Ascomycota species. Our results indicate that ectomycorrhizal formation, diversity, and community composition rapidly respond to both precipitation events and to the amount of precipitation. These changes affect ecosystem functions, such as nutrient cycling, decomposition, and plant nutrient uptake, in semiarid regions.

Highlights

Dryland ecosystems, defined as those having a precipitation: evapotranspiration ratio less than 1, occupy approximately 35– 45% of the Earth’s land area (Asner et al 2003; Reynolds et al 2007; Jenerette et al 2012)
From April to the end of June, the soil water content decreased, and it remained low until the monsoon rain at the end of July
From the automated minirhizotron images, there was a drop in number of ECM root tips from May to August (Allen and Kitajima 2014)

Summary

Introduction

Dryland ecosystems, defined as those having a precipitation: evapotranspiration ratio less than 1, occupy approximately 35– 45% of the Earth’s land area (Asner et al 2003; Reynolds et al 2007; Jenerette et al 2012). Rainfall in dryland ecosystems has seasonal patterns, but the actual amount and timing varies seasonally and annually and is highly unpredictable (NoyMeir 1973). Pulse responses of microorganisms and plants increase the biogeochemical fluxes of carbon and nitrogen (Austin et al 2004; Huxman et al 2004; Inglima et al 2009; Yahdjian and Sala 2010; Dijkstra et al 2012). Biological transformation of nitrogen by microorganisms is stimulated by the water supply (Yahdjian and Sala 2010; Dijkstra et al 2012).

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