Manipulating livestock grazing to enhance native plant diversity and cover in native grasslands

Abstract

Temperate perennial grasslands globally have been subject to extensive biodiversity loss. Identifying livestock grazing regimes that maintain and enhance the diversity and cover of native plant species in these ecosystems remains a key challenge. The responses of vegetation to different sheep grazing regimes were assessed over 3 years in grasslands of southeastern Australia. An open communal experimental design was used to assess the effects of varying season and duration of exclusion of grazing by sheep, replicated at three locations. Manipulation of season and duration of exclusion of grazing led to few major changes in the cover of native perennial grasses or forbs, although seasonal variation was considerable. Exclusion of grazing in the spring did increase the likelihood of occurrence of grazing-sensitive native forb species but also lead to an increase in the cover of exotic annual species. However, cover of exotic annual species tended to decline with increasing duration of exclusion, while the abundance of native, grazing-sensitive forbs and the cover of perennial grasses increased. Small-scale richness of native perennial forb species increased with a 3-month period of exclusion of grazing, but declined with year-round exclusion of sheep. Total species richness also declined in response to year-round exclusion of sheep and rates of decline were correlated with the rate at which herbage mass accumulated. While strategic grazing did not result in major vegetation changes in the short term, it is suggested that some grazing exclusion may enhance the survival of infrequent species most sensitive to sheep grazing. Caution, however, should be taken when grazing regimes implemented benefit both desirable (native forbs) and undesirable (exotic annuals) species. Having a mosaic of flexible grazing management regimes across the landscape is likely to be beneficial for native plant diversity.

Loss of biodiversity and hydrologic function in seasonal wetlands persists over 10 years of livestock grazing removal

“…In the Dambo wetlands of Zimbabwe, ungrazed wetlands had much lower species richness than both moderately grazed and year‐round grazing regimes (Dahwa et al ). Using various grazing exclusion trials in grasslands in southeastern Australia, Mavromihalis et al () recorded an overall loss of plant species richness coupled with an increase in herbage mass with complete exclusion of sheep but found little consistent changes in native species composition with other seasonal grazing exclusion treatments. A study of depressional wetlands in British Columbia, Canada, found differential responses of the plant community to grazing intensity depending on the type of wetland with a general increase in annual forbs and decrease in perennial herbaceous species with increasing intensity (Jones et al ).…”

“…The role of disturbance in maintaining biodiversity and ecosystem function is one of the most critical elements in the success of ecological restoration yet very few studies measure—let alone experimentally manipulate—disturbance regimes and track the impact on success of the restoration project (Fuhlendorf & Engle ; Suding ; Mavromihalis et al ). In fact, Brudvig () found that out of 190 articles on ecosystem restoration, only 17% measured the effects of disturbance on restoration outcomes.…”

Decadal plant composition changes in grazed native grassland

“…Although grazing rest during periods of peak plant growth and reproduction (i.e. spring) has been shown to maintain native forb richness and grass cover (Leonard & Kirkpatrick 2004;Zimmer et al 2010b;Mavromihalis et al 2013;Fedrigo et al 2018), this study could not dissociate the effects of grazing from other factors operating at larger spatial scales (i.e. rainfall).…”

“…; Mavromihalis et al . ; Fedrigo et al . ), this study could not dissociate the effects of grazing from other factors operating at larger spatial scales (i.e.…”

Grazing primarily drives the relative abundance change of C4 plants in the typical steppe grasslands across households at a regional scale

“…Animal grazing is the most dominant land use of grasslands (Mavromihalis et al 2013). Grazing influence on the relative abundance of C 4 plants has received much attention in the study of grasslands in North and South America (Reeder et al 2004;Altesor et al 2006;Derner et al 2006), Central Asia (Auerswald et al 2012;Ren et al 2012), South Africa (Franz-Odendaal et al 2002), Australia (Bell et al 2012) and New Zealand (Crush and Rowarth 2007).…”