Competition Indices Identify Forb Species That Promote Overyielding of a Dominant Grass in Grassland Restoration

Drew A Scott

doi:10.5539/jps.v9n1p28

Abstract

Overyielding is a common phenomenon. Overyielding of dominant grasses when in competition with common forbs during grassland restoration could lead to lower plant diversity. My objective was to characterize overyielding of Andropogon gerardii in competition with fcommon forbs. I collected soils representing different stages of restoration (0, 4, and 16 years restored) and conducted a pairwise competition experiment with a dominant grass, Andropogon gerardii, in competition with four subordinate forbs (Oligoneuron rigidum L., Liatris punctata Hook, Lespedeza capitata Michx., or Desmanthus illinoensis Michx.). Relative yield indices (RY) were calculated by comparison with a two-individual monoculture of A. gerardii with both per grass biomass and per grass net absolute tiller appearance rate (TAR). Overyielding of A. gerardii was in competition with Oligoneuron rigidum was indicated by RY values (greater than1) using both biomass and TAR measurements. These findings suggest that O. rigidum should be given low priority for inclusion in tallgrass prairie restoration seed mixes.

Highlights

Plant communities in grassland restorations undergo rapid changes (Manning & Baer, 2018; Scott and Baer, 2019) coinciding with dynamically changing soil properties (Rosenzweig et al 2016; Scott et al, 2017) and could change the cover of dominant grasses
Overyielding of dominant grasses when in competition with common forbs during grassland restoration could lead to lower plant diversity
These findings suggest that O. rigidum should be given low priority for inclusion in tallgrass prairie restoration seed mixes

Summary

Introduction

Plant communities in grassland restorations undergo rapid changes (Manning & Baer, 2018; Scott and Baer, 2019) coinciding with dynamically changing soil properties (Rosenzweig et al 2016; Scott et al, 2017) and could change the cover of dominant grasses. Whether overyielding (i.e. more biomass production in mixture relative to monoculture) of a dominant grass occurs during competition with forb species within grassland restoration remains unclear. In this follow up report to Scott & Baer (2018), which described soil influence on performance of a dominant grass, I report on overyielding of dominant grass in competition with common forbs during tallgrass prairie restoration. Overyielding is expected to occur commonly and reach equilibrium quickly based on theoretical analyses (Beckage & Gross, 2006) Because of this expectation, a way to screen for overyielding of a dominant grass when in competition with common forbs is useful for planning diverse grassland restorations

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