Grass Trumps Trees with Fire

Mayer, Audrey L.; Khalyani, Azad Henareh

doi:10.1126/science.1213908

Cited by 61 publications

(50 citation statements)

References 14 publications

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“…Such feedbacks have been observed in maintaining vegetation shifts in the boreal forest ) and elsewhere (Mayer and Khalyani 2011). The contribution of static variables such as drainage type to the SA model also suggests that fire activity is at least partly path dependent.…”

Section: Static Vs Dynamic Explanatory Variablesmentioning

confidence: 72%

Static and dynamic controls on fire activity at moderate spatial and temporal scales in the Alaskan boreal forest

et al. 2016

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. 2016. Static and dynamic controls on fire activity at moderate spatial and temporal scales in the Alaskan boreal forest. Ecosphere 7(11):e01572. 10.1002/ ecs2.1572Abstract. Wildfire, a dominant disturbance in boreal forests, is highly variable in occurrence and behavior at multiple spatiotemporal scales. New data sets provide more detailed spatial and temporal observations of active fires and the post-burn environment in Alaska. In this study, we employ some of these new data to analyze variations in fire activity by developing three explanatory models to examine the occurrence of (1) seasonal periods of elevated fire activity using the number of MODIS active fire detections data set (MCD14DL) within an 11-day moving window, (2) unburned patches within a burned area using the Monitoring Trends in Burn Severity fire severity product, and (3) short-to-moderate interval (<60 yr) fires using areas of burned area overlap in the Alaska Large Fire Database. Explanatory variables for these three models included dynamic variables that can change over the course of the fire season, such as weather and burn date, as well as static variables that remain constant over a fire season, such as topography, drainage, vegetation cover, and fire history. We found that seasonal periods of high fire activity are associated with both seasonal timing and aggregated weather conditions, as well as the landscape composition of areas that are burning. Important static inputs to the model of seasonal fire activity indicate that when fire weather conditions are suitable, areas that typically resist fire (e.g., deciduous stands) may become more vulnerable to burning and therefore less effective as fire breaks. The occurrence of short-to-moderate interval fires appears to be primarily driven by weather conditions, as these were the only relevant explanatory variables in the model. The unique importance of weather in explaining short-to-moderate interval fires implies that fire return intervals (FRIs) will be sensitive to projected climate changes in the region. Unburned patches occur most often in younger stands, which may be related to a greater deciduous fraction of vegetation as well as lower fuel loads compared with mature stands. The fraction of unburned patches may therefore increase in response to decreasing FRIs and increased deciduousness in the region, or these may decrease if fire weather conditions become more severe.

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Section: Static Vs Dynamic Explanatory Variablesmentioning

confidence: 72%

Static and dynamic controls on fire activity at moderate spatial and temporal scales in the Alaskan boreal forest

et al. 2016

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“…Most understories of overgrown savannas have 3 to 5 percent of full sunlight, and much more light is needed to stimulate germination, promote growth, and encourage seed production of the herbaceous species commonly found in savannas. For example, for grasses to proliferate, tree canopy cover needs to be <50 percent (Anderson et al 1999, Mayer and Khalyani 2011, Nelson 2010, Starver et al 2011. Managing overstory crown cover between 5 to 50 percent influences the development of the ground flora.…”

Section: Oak Savannasmentioning

confidence: 99%

The fireoak literature of eastern North America: synthesis and guidelines

Brose¹,

Dey²,

Waldrop³

2014

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Guidelines for using prescribed fire to regenerate and restore upland oak forests, woodlands, and savannas in eastern North America were developed by synthesizing the results of more than 100 scientific publications. The first four chapters provide background information on the values of oak ecosystems, eastern fire history, oak's adaptations to fire, and the findings of fire-oak research conducted over the past 50 years. The final chapter synthesizes that background information into guidelines that explain how to use prescribed fire to facilitate oak seedling establishment, release oak reproduction from competing mesophytic hardwoods, and rehabilitate open oak woodlands, oak savannas, and scrub oak communities. A reference section is also provided for readers desiring to delve more deeply into the associations between periodic fire and oak forests, woodlands, and savannas.

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“…Rapid land cover transitions within savanna biomes can be driven by complex nonlinear feedbacks between biophysical and human systems at local, regional, and even global scales [14,71]. For example, recent evidence suggests increasing levels of atmospheric CO 2 may play a significant role in the expansion of woody plants in savannas by favoring regrowth following injury from fire or browsing [72,73] and inducing plant water-saving [74].…”

Section: Chobe District Net and Gross Lccmentioning

confidence: 99%

Land Cover Change in Northern Botswana: The Influence of Climate, Fire, and Elephants on Semi-Arid Savanna Woodlands

Fox

Vandewalle²,

Alexander

2017

Land

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Abstract:Complex couplings and feedback among climate, fire, and herbivory drive short-and long-term patterns of land cover change (LCC) in savanna ecosystems. However, understanding of spatial and temporal LCC patterns in these environments is limited, particularly for semi-arid regions transitional between arid and more mesic climates. Here, we use post-classification analysis of Landsat TM (1990), ETM+ (2003), and OLI (2013) satellite imagery to classify and assess net and gross LCC for the Chobe District, a 21,000 km 2 area encompassing urban, peri-urban, rural, communally-managed (Chobe Enclave), and protected land (Chobe National Park, CNP, and six protected forest reserves). We then evaluate spatiotemporal patterns of LCC in relation to precipitation, fire detections (MCD14M, 2001(MCD14M, -2013 from the Moderate Resolution Imaging Spectroradiometer (MODIS), and dry season elephant (Loxodonta africana) aerial survey data (2003, 2006, 2012, 2013). Woodland cover declined over the study period by 1514 km 2 (16.2% of initial class total), accompanied by expansion of shrubland (1305 km 2 , 15.7%) and grassland (265 km 2 , 20.3%). Net LCC differed importantly in protected areas, with higher woodland losses observed in forest reserves compared to the CNP. Loss of woodland was also higher in communally-managed land for the study period, despite gains from 2003-2013. Gross (class) changes were characterized by extensive exchange between woodland and shrubland during both time steps, and a large expansion of shrubland into grassland and bare ground from 2003-2013. MODIS active fire detections were highly variable from year to year and among the different protected areas, ranging from 1.8 fires*year −1 /km 2 in the Chobe Forest Reserve to 7.1 fires*year −1 /km 2 in the Kasane Forest Reserve Extension. Clustering and timing of dry season fires suggests that ignitions were predominately from anthropogenic sources. Annual fire count was significantly related to total annual rainfall (p = 0.009, adj. R 2 = 0.50), with a 41% increase in average fire occurrence in years when rainfall exceeded long-term mean annual precipitation (MAP). Loss of woodland was significantly associated with fire in locations experiencing 15 or more ignitions during the period 2001-2013 (p = 0.024). Although elephant-mediated damage is often cited as a major cause of woodland degradation in northern Botswana, we observed little evidence of unsustainable pressure on woodlands from growing elephant populations. Our data indicate broad-scale LCC processes in semi-arid savannas in Southern Africa are strongly coupled to environmental and anthropogenic forcings. Increased seasonal variability is likely to have important effects on the distribution of savanna plant communities due to climate-fire feedbacks. Long-term monitoring of LCC in these ecosystems is essential to improving land use planning and management strategies that protect biodiversity, as well as traditional cultures and livelihoods under future climate change scenarios for Southern Afr...

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Grass Trumps Trees with Fire

Abstract: Feedbacks involving rainfall, fire, and vegetation govern transitions between forests, savannas, and grasslands.

Cited by 61 publications

References 14 publications

Static and dynamic controls on fire activity at moderate spatial and temporal scales in the Alaskan boreal forest

Static and dynamic controls on fire activity at moderate spatial and temporal scales in the Alaskan boreal forest

The fireoak literature of eastern North America: synthesis and guidelines

Land Cover Change in Northern Botswana: The Influence of Climate, Fire, and Elephants on Semi-Arid Savanna Woodlands

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Grass Trumps Trees with Fire

Abstract: Feedbacks involving rainfall, fire, and vegetation govern transitions between forests, savannas, and grasslands.

Cited by 61 publications

References 14 publications

Static and dynamic controls on fire activity at moderate spatial and temporal scales in the Alaskan boreal forest

Static and dynamic controls on fire activity at moderate spatial and temporal scales in the Alaskan boreal forest

The fire&#151;oak literature of eastern North America: synthesis and guidelines

Land Cover Change in Northern Botswana: The Influence of Climate, Fire, and Elephants on Semi-Arid Savanna Woodlands

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The fireoak literature of eastern North America: synthesis and guidelines