Agronomy and Horticulture Department

 

ORCID IDs

Jane F. Capozzelli

Date of this Version

2020

Citation

Ecosphere 11(2):e02993

Comments

© 2020 The Authors.

Open access

DOI: 10.1002/ecs2.2993

Abstract

Woody encroachment can convert grasslands and savannas to shrublands and woodlands, so understanding the processes which regulate woody encroachment is necessary to conserve or restore these ecosystems. We hypothesized that recreating the fire–grazing interaction would limit woody encroachment because focal grazing increases fuel accumulation on unburned areas and increases browsing on emergent woody plants in burned areas. This study was conducted in the Grand River Grasslands of Iowa and Mis- souri (USA) on 11 sites (15.4–35.0 ha). Each site was assigned to one treatment: patch-burn-graze (n = 4), with spatially discrete prescribed fires and free access by cattle (the fire–grazing interaction); graze-and- burn (n = 4), with free access by cattle and one burn of the entire site every 3 yr; or burn-only (n = 3), with one site-wide burn every 3–5 yr and no grazing. The burn-only treatment increased woody encroachment fourfold compared to the graze-and-burn and patch-burn-graze treatments (130.2, standard error [SE] = 16.0; 20.9, SE = 12.0; and 46.3, SE = 10.8; plants/200 m2). The patch-burn-graze treatment had 2– 3 cm more accumulated fuel and woody plants which were 12% shorter, on average, than the other treat- ments (comparing eight common species). The movement of large herbivores also appeared to decrease the frequency of woody species which spread vegetatively. Our work illustrates how the fire–grazing inter- action may control woody encroachment and shows that cattle substitute, at least partially, for endemic large herbivores.

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