Facilitation by isolated trees triggers woody encroachment and a biome shift at the savanna–forest transition

Abreu, Rodolfo Cesar Real de; Durigan, Giselda; Melo, Antônio Carlos Galvão de; Pilon, Natashi A. L.; Hoffmann, William A.

doi:10.1111/1365-2664.13994

Cited by 14 publications

(13 citation statements)

References 100 publications

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“…We observed an increase in vegetation density in SBES throughout the 15 years between the two surveys analyzed (from 2003 to 2018), corroborating that woody encroachment may be a common phenomenon in the Cerrado (e.g., Moreira, 2000;Roitman et al, 2008;Pinheiro and Durigan, 2009;Abreu et al, 2017Abreu et al, , 2021. The 27% increase in the mean EVI affected primarily the grasslands.…”

Section: Woody Encroachmentsupporting

confidence: 71%

“…The other plots that were sampled, burned for the last time before 1985 (Melo and Durigan, 2011;Conciani et al, 2021). Although these sparse fire events contributed to the grasslands maintenance in the area, SBES have been suffering under woody encroachment across this period (Melo and Durigan, 2011;Abreu et al, 2017Abreu et al, , 2021. The study site also holds stands of exotic timber plantations, including Eucalyptus sp.…”

Section: Study Areamentioning

confidence: 99%

“…The total richness observed (17 species) is high, given that only about 8% of the Cerrado small mammal communities are composed of more than 10 species (Mendonça et al, 2018), evidencing the completeness of the surveys in SBES. Rodents were the richest order, a recurrent pattern (Quintela et al, 2020;Abreu et al, 2021), with five sigmodontine rodents representing 74% of the total abundance in the SBES assemblage (Oligoryzomys nigripes, O. mattogrossae, Calomys tener, Cerradomys scotti, and Necromys lasiurus). The general abundance pattern recorded for SBES is also in accordance with previous Cerrado studies (see Mendonça et al, 2018 review), with Necromys lasiurus being the dominant species in the 2003 survey, and O. nigripes in the 2017-2018 survey.…”

Section: Small Mammal Community Structurementioning

confidence: 99%

“…In the case of forest-savanna ecotone regions, climate, and land-use change, especially fire and deforestation, are leading to an invasion savanna species into disturbed forests, shifting the forest fauna assemblages toward a "savannization" (Sales et al, 2020). Similarly, the woody encroachment is changing southern Cerrado assemblages toward a "forestization, " with the invasion of species from adjacent forest biomes and the loss of savanna specialists (Abreu et al, 2017(Abreu et al, , 2021. Our findings highlight the importance of the maintenance of the mosaic of open formations in Cerrado remnants in order to shelter a high diversity of small mammal grassland specialists.…”

Section: Woody Encroachmentmentioning

confidence: 99%

“…For instance, the Santa Bárbara Ecological Station (SBES), located in southeastern Brazil, has been under almost complete fire suppression for about 30 years, and recently (since 2015) fire management was introduced (Durigan et al, 2020). Over three decades , this remnant of Cerrado experienced woody encroachment and decreases in plant (especially herbs and shrubs) and ant species typical of open habitats (Abreu et al, 2017(Abreu et al, , 2021.…”

Section: Introductionmentioning

confidence: 99%

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Winners and Losers: How Woody Encroachment Is Changing the Small Mammal Community Structure in a Neotropical Savanna

et al. 2021

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Years of fire suppression, decreases in herbivores, and global climate change have led to shifts in savannas worldwide. Natural open vegetation such as grasslands and shrublands is increasing in wood density, but the effects for small mammals are not well understood. While most of the mammal studies from the Brazilian Cerrado are concentrated in the core area of this large Neotropical savanna, its southern portions are suffering from biome shifting through woody encroachment. Herein, we surveyed a small mammal community from the southeastern boundary of Cerrado (Santa Bárbara Ecological Station) and evaluated the micro and macro environmental variables shaping community structure in order to investigate how the woody encroachment in the last 15 years may have influenced this assemblage. We recorded 17 species of marsupials and rodents along five distinct habitats in a gradient from grasslands to woodlands. Although richness was not affected by microhabitat variables, total and relative abundance varied according to habitat type and in relation to herbaceous, shrub, and tree density. Rodents such as Calomys tener and Clyomys laticeps were positively affected by increasing herb cover, Cerradomys scotti and Oligoryzomys nigripes by shrub cover, while the marsupial Didelphis albiventris had higher association with increasing tree cover. We detected an increase of 27.4% in vegetation density (EVI) between 2003 and 2018 in our study site, and this woody encroachment negatively affected the abundance of some small mammals. The open-area specialists Cryptonanus chacoensis and C. scotti had a decrease in abundance, while D. albiventris and O. nigripes were favored by woody encroachment. Our data suggest that woody encroachment is shifting community composition: small mammals often associated with grasslands and open savannas are likely to be negatively affected by woody encroachment; while species that rely on tree-covered habitats are likely to benefit from an increasing woody landscape. Therefore, forest-dwellers are gradually replacing open-vegetation inhabitants. Active management of open formations (e.g., with prescribed burning) may be needed to maintain Cerrado biodiversity, especially considering the open-area endemics.

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Section: Woody Encroachmentsupporting

confidence: 71%

Section: Study Areamentioning

confidence: 99%

Section: Small Mammal Community Structurementioning

confidence: 99%

Section: Woody Encroachmentmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Winners and Losers: How Woody Encroachment Is Changing the Small Mammal Community Structure in a Neotropical Savanna

et al. 2021

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Demography and dispersal at a grass‐shrub ecotone: A spatial integral projection model for woody plant encroachment

Drees

Ochocki

Collins

et al. 2023

Ecological Monographs

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The encroachment of woody plants into grasslands is a global phenomenon with implications for biodiversity and ecosystem function. Understanding and predicting the pace of expansion and the underlying processes that control it are key challenges in the study and management of woody encroachment. Theory from spatial population biology predicts that the occurrence and speed of expansion should depend sensitively on the nature of conspecific density dependence. If fitness is maximized at the low‐density encroachment edge, then shrub expansion should be “pulled” forward. However, encroaching shrubs have been shown to exhibit positive feedbacks, whereby shrub establishment modifies the environment in ways that facilitate further shrub recruitment and survival. In this case there may be a fitness cost to shrubs at low density causing expansion to be “pushed” from behind the leading edge. We studied the spatial dynamics of creosotebush (Larrea tridentata), which has a history of encroachment into Chihuahuan Desert grasslands over the past century. We used demographic data from observational censuses and seedling transplant experiments to test the strength and direction of density dependence in shrub fitness along a gradient of shrub density at the grass–shrub ecotone. We also used seed‐drop experiments and wind data to construct a mechanistic seed‐dispersal kernel, then connected demography and dispersal data within a spatial integral projection model (SIPM) to predict the dynamics of shrub expansion. Contrary to expectations based on potential for positive feedbacks, the shrub encroachment wave is “pulled” by maximum fitness at the low‐density front. However, the predicted pace of expansion was strikingly slow (ca. 8 cm/year), and this prediction was supported by independent resurveys of the ecotone showing little to no change in the spatial extent of shrub cover over 12 years. Encroachment speed was acutely sensitive to seedling recruitment, suggesting that this population may be primed for pulses of expansion under conditions that are favorable for recruitment. Our integration of observations, experiments, and modeling reveals not only that this ecotone is effectively stalled under current conditions but also why that is so and how that may change as the environment changes.

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Effects and response of the Cerrado ground-layer to frost along the canopy cover gradient

et al. 2022

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Facilitation by isolated trees triggers woody encroachment and a biome shift at the savanna–forest transition

Cited by 14 publications

References 100 publications

Winners and Losers: How Woody Encroachment Is Changing the Small Mammal Community Structure in a Neotropical Savanna

Winners and Losers: How Woody Encroachment Is Changing the Small Mammal Community Structure in a Neotropical Savanna

Demography and dispersal at a grass‐shrub ecotone: A spatial integral projection model for woody plant encroachment

Effects and response of the Cerrado ground-layer to frost along the canopy cover gradient

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