Temporary grazing exclusion promotes rapid recovery of species richness and productivity in a long‐term overgrazed Campos grassland

Abstract

Moderate grazing intensity is considered the basic requirement to enhance ecosystem function in grasslands. Yet, deterioration by overgrazing is common in many biomes, including Campos grasslands in South America. Understanding how grazing management can lead to recovery of ecosystem function is essential to design and implement effective strategies for sustainable use of this resource. In a long‐term field experiment carried out in Southern Brazil, we studied the effects of temporal grazing exclusions (spring or fall) at moderate and severe livestock grazing intensities (maintained by adjusting contrasting forage allowances) on the species richness, botanical composition, forage mass, sward height, and photosynthetic active radiation intercepted. The experiment was arranged in a completely randomized design with three replications of grazing exclusions, applied simultaneously at moderate and severe grazing intensities. Moderate grazing intensity showed a bimodal structure of shorter and taller canopies, and high species richness. Severe grazing created a shorter and homogeneous sward structure characterized by less standing biomass and species loss. In response to grazing exclusions, sward height, standing biomass, and light interception recovered almost to the levels of moderate grazing. Further, within 2 years grass species richness increased and botanical composition changed toward grasses with erect habit prevailing in moderate grazing intensity. Our study confirms that (1) moderate grazing intensities allow the coexistence of high number of species and (2) spring grazing exclusions of long‐term overgrazed grasslands can lead to a quick start to recover the grass species richness, primary productivity, and species composition like that prevailing in well‐managed grasslands.

Resilience and restoration of tropical and subtropical grasslands, savannas, and grassy woodlands

“…The resilience of tropical old‐growth grasslands to human‐altered grazing and fire regimes is highly dependent on ecosystem type and site‐specific conditions. In general, disturbance‐dependent grasslands, with moderate to high soil water and nutrient availability, can tolerate more intense grazing for longer durations (Müller et al ., ; Fedrigo et al ., ) relative to edaphic grasslands, where soil conditions severely constrain plant productivity and regeneration (Kolbek & Alves, ; Fig. A, B).…”

“…One cannot substitute native wildlife for livestock and expect to maintain the same ecological processes and plant communities; grazing and browsing patterns differ among species and may change fire regimes, woody plant cover, and biogeochemical cycling (Hempson, Archibald & Bond, 2017). Whereas livestock are incompatible with conservation of edaphic old-growth grasslands, in certain disturbance-dependent old-growth grasslands, native wildlife and/or livestock can be used to manage vegetation if manipulated adequately (Fuhlendorf & Engle, 2001;Joubert, Pryke & Samways, 2017;Fedrigo et al, 2018). Further, where land-use policies restrict fire in disturbance-dependent grasslands, domestic livestock can, in some cases, serve as an imperfect surrogate for fire, by controlling the biomass of palatable dominant plants (both native or exotic) and preventing shrub and tree encroachment (Ratter et al, 1997;Müller et al, 2012).…”

Decadal plant composition changes in grazed native grassland

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

“…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).…”

Passive restoration contributes to bird conservation in Brazilian Pampa grasslands

“…We based this assumption on our field experience of more than 20 years (C. S. Fontana) as well as on the results of studies indicating that plant species richness (Torchelsen et al ) and floristic composition of grassland remnants (Fensham et al ) can recover within ~ 10 years of abandonment, even if some differences to reference grasslands may remain both in terms of structure and floristic composition (Tognetti et al ). In addition, Fedrigo et al () evaluated the vegetation of Pampa grasslands and found high restoration capacity within ~ 3 months after a long period of intense grazing.…”