Extractable nitrogen and microbial community structure respond to grassland restoration regardless of historical context and soil composition.

Sara Jo M Dickens,David Crowley,Louis S Santiago,Edith B Allen

doi:10.1093/aobpla/plu085

Sara Jo M Dickens, David Crowley + Show 2 more

Open Access

https://doi.org/10.1093/aobpla/plu085

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Journal: AoB PLANTS	Publication Date: Jan 1, 2015
Citations: 12	License type: CC BY 4.0

Affiliation: University of California, Riverside

Abstract

Grasslands have a long history of invasion by exotic annuals, which may alter microbial communities and nutrient cycling through changes in litter quality and biomass turnover rates. We compared plant community composition, soil chemical and microbial community composition, potential soil respiration and nitrogen (N) turnover rates between invaded and restored plots in inland and coastal grasslands. Restoration increased microbial biomass and fungal : bacterial (F : B) ratios, but sampling season had a greater influence on the F : B ratio than did restoration. Microbial community composition assessed by phospholipid fatty acid was altered by restoration, but also varied by season and by site. Total soil carbon (C) and N and potential soil respiration did not differ between treatments, but N mineralization decreased while extractable nitrate and nitrification and N immobilization rate increased in restored compared with unrestored sites. The differences in soil chemistry and microbial community composition between unrestored and restored sites indicate that these soils are responsive, and therefore not resistant to feedbacks caused by changes in vegetation type. The resilience, or recovery, of these soils is difficult to assess in the absence of uninvaded control grasslands. However, the rapid changes in microbial and N cycling characteristics following removal of invasives in both grassland sites suggest that the soils are resilient to invasion. The lack of change in total C and N pools may provide a buffer that promotes resilience of labile pools and microbial community structure.

Highlights

The effects of exotic plant invasions on terrestrial ecosystems vary temporally and spatially and span scales ranging from the plant rhizosphere to changes in nutrient flux that occur at the ecosystem level (Ehrenfeld 2003; Potthoff et al 2009)
This study indicates that the soils of these systems are dynamic and change in response to exotic or native vegetation type and seasonal variation in soil moisture
Measured changes in extractable soil N and microbial characteristics in response to removal of exotic plants indicated that grassland soils are not resistant to the impacts of plant community shifts, but have the capacity for resilience regardless of the method of exotic plant control

Summary

Introduction

The effects of exotic plant invasions on terrestrial ecosystems vary temporally and spatially and span scales ranging from the plant rhizosphere to changes in nutrient flux that occur at the ecosystem level (Ehrenfeld 2003; Potthoff et al 2009). The impacts of exotic invasive plants on soil microbial communities and nutrient fluxes have received considerable attention Dickens et al — Soil chemical and microbial response to restoration responses to restoration practices and studies on the legacy effects of plant invasions are relatively new areas of research (Potthoff et al 2006, 2009; Kulmatiski and Beard 2008, 2011; Dickens 2010; Dickens and Allen 2014). The role of legacy effects of exotic invasion and exotic species identity in the success of restoration is unclear, greatly limiting the knowledge base needed for strategic restoration of invaded lands

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