Grassland compost amendments increase plant production without changing plant communities

Rebecca Ryals,Claudia Stein,Valerie T Eviner,Whendee L Silver,Katharine N Suding,D P C Peters

doi:10.1002/ecs2.1270

Rebecca Ryals, Claudia Stein + Show 4 more

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https://doi.org/10.1002/ecs2.1270

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Abstract

AbstractCompost amendment to grassland is a novel strategy proposed and demonstrated to increase ecosystem carbon (C) storage. However, the effects of compost applications on biomass production and plant diversity are not well known. We assessed impacts of a one‐time compost amendment over 4 yr on plant dynamics in two grazed grassland ecosystems in California: a coastal prairie and valley grassland. The valley grassland was dominated by exotic annual grasses and had significantly lower species diversity than the coastal prairie, which consisted of a mix of perennial and annual grasses and forbs. We observed large and persistent increases in aboveground biomass. Over the 4 study years, aboveground biomass from compost‐amended plots increased by 76% ± 21% at the valley grassland and 41% ± 21% at the coastal prairie, compared with controls. Plant N content was also greater from compost‐amended plots. There were no major shifts in species richness or abundance at either grassland site. Overall, plant communities at both grasslands were relatively resistant to the compost addition, but responses of some individual species were observed. Notably at the valley grassland, the abundance of forbs decreased slightly, while the abundance of grasses increased. The abundance of two noxious weeds did not change as a result of the compost amendment. Our results suggest that a single application of composted organic matter used to sequester C provided cobenefits to grassland plant dynamics. The compost amendments produced sustained increases in plant productivity and forage production as well as plant N content without greatly affecting the diversity of these exotic annual grasslands.

Highlights

Grasslands provide a multitude of ecosystem services, including forage production for livestock grazing, soil carbon (C) sequestration, and floristic diversity (Sala and Paruelo 1997, Herrero et al 2009, Huntsinger and Oviedo 2014)
The objective of our research was to determine the impacts on plant dynamics in two grassland ecosystems that were managed for C sequestration
Significant treatment differences in pregrazed aboveground biomass were detected at both grassland sites within the first year following the compost application (Fig. 1)

Summary

Introduction

Grasslands provide a multitude of ecosystem services, including forage production for livestock grazing, soil carbon (C) sequestration, and floristic diversity (Sala and Paruelo 1997, Herrero et al 2009, Huntsinger and Oviedo 2014). The addition of composted organic material has been recommended as strategy to sequester C in managed grasslands (Ryals and Silver 2013, Haden and De Gryze 2014). Grassland plant communities of the far western USA are dominated by exotic annual grasses. These ecosystems have undergone major changes in plant community composition due to intensive grazing, severe drought, and the introduction of species from European Mediterranean regions in the 19th century (Bartolome et al 2007a). Introduced annual grass species were opportunistic and thrived in resource-p ulse- driven environments These invasibility traits led to their persistence and altered nutrient cycling that prevent establishment or recovery of perennial grasses (D’Antonio et al 2007). Secondary invaders have spread throughout exotic annual plant communities and comprise the economic viability of rangelands by reducing forage production and nutritional quality (Norton et al 2007)

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