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Ecological Intelligence

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Ecological Intelligence / Subject

savanna

Africa

Open glades may use herbivores to hold back woody regrowth

Evidence
Peer-reviewed experimental exclosure study
Geography
South African woody-encroached savanna
System
Savanna / woody encroachment and browsing

WHAT THE EVIDENCE SAYS

Researchers opened 24-by-24-metre glades at six sites and fenced paired subplots. Grazers and browsers selected clearings in fine-leaved woodland more than broad-leaved stands. Browsing after one growing season kept resprouting shoots relatively short, but preference depended strongly on tree type.

WHY IT MATTERS / OUR READ

For managers, clearing is the first disturbance, not a completed regime. Test herbivore visitation, resprout height, plant composition and costs by woody species before extrapolating small-glade designs.

CAVEATS / UNCERTAINTY

Only six sites and one growing season; no evidence yet that grazing feedback will keep glades open without future maintenance over multiple years.

SOURCE

Journal of Applied Ecology · paired clearing/exclosure experiment
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Paired exclosures suggest a savanna-clearing response depends on woody species identity and browsers' preferences.

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North America

Fire and girdling changed structure faster than they rebuilt an oak-savanna groundlayer

Evidence
Peer-reviewed restoration field experiment
Geography
West Michigan, USA
System
Degraded oak savanna

WHAT THE EVIDENCE SAYS

Prescribed fire increased bare ground and tree girdling created snags and structural change, but desired groundlayer recruitment remained limited where shrub cover and residual canopy continued to constrain light and establishment. The authors argue for more targeted canopy reduction, refined burning and active seed inputs where propagule limitation persists.

WHY IT MATTERS / OUR READ

Restoring a process is not always enough to restore the community that once depended on it. Fire can be necessary and still insufficient when canopy structure, shrubs and missing propagules keep the system on a different trajectory.

CAVEATS / UNCERTAINTY

The experiment covers two degraded savanna communities and a finite treatment period, so responses may differ under other soils, seed banks and disturbance histories. Additional treatments recommended by the authors are management inferences rather than outcomes already demonstrated in this study.

SOURCE

Forest Ecology and Management
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In two degraded Michigan oak savannas, prescribed fire and tree girdling opened parts of the system but produced limited recruitment of the desired herbaceous community, complicating the idea that restoring disturbance automatically restores composition.

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Peer-reviewed Africa

One national park can contain very different fire regimes

Evidence
Peer-reviewed
Geography
Hwange National Park, Zimbabwe
System
Fire-managed savanna protected area

WHAT THE EVIDENCE SAYS

MODIS records from 2002–2022 showed strong spatial differences in fire across Hwange National Park. Roughly 37% of the park burned at least once, but the Robins section had far more recurrent burning than Makona, and total annual burned area did not show a significant park-wide temporal trend. Fire patterns also varied with vegetation, temperature and precipitation.

WHY IT MATTERS / OUR READ

A protected-area average can conceal operationally important fire heterogeneity. Management units may need different monitoring and fire strategies even inside a single legal boundary.

CAVEATS / UNCERTAINTY

Satellite burned-area products capture fire occurrence more readily than ecological severity, ignition cause or population response. The study is observational, and section-level patterns should not be interpreted as proof that one fire regime is optimal.

SOURCE

Journal of Applied Ecology · Original evidence
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Two decades of satellite data from Hwange, Zimbabwe, show strong internal variation in burned area and recurrence even where park-wide totals show no significant trend.

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