Savannas of North America

Beckage, Brian

doi:10.1002/9781119081111.ch5

Cited by 7 publications

(4 citation statements)

References 128 publications

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“…Fire is an evolutionary driver of tallgrass prairies, particularly in more mesic areas where it reduces woody plant encroachment (Fowler and Beckage, 2020). Fire alters the ecosystem through the selection of plant species with a particular suite of fire‐tolerant traits (Bond and Keeley, 2005) and by impacting moisture, light, and nitrogen availability (Collins, 1992; Gibson et al, 1993; Collins et al, 1995).…”

Section: Introductionmentioning

confidence: 99%

Effects of white‐tailed deer exclusion on the plant community composition of an upland tallgrass prairie ecosystem

Bloodworth

Ritchie

Komatsu

2020

J Vegetation Science

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Questions: Grasslands support ecosystem services, promote diversity, and assist in carbon sequestration. However, grasslands worldwide are diminishing in area, and understanding the drivers shaping the remaining grasslands is critical for their maintenance. The North American tallgrass prairie covers approximately 13% of its historical range and is shaped by fire and herbivory. Fire frequency negatively correlates with plant species richness, while bison (Bos bison)-the historical grazers-offset this effect. However, bison populations have declined, and large browsers are increasing in density. Few studies though have examined the role of large browsers-particularly white-tailed deer (Odocoileus virginianus)-and their interaction with fire frequency in tallgrass prairies. Here, we addressed two questions: (a) What are the impacts of deer on plant diversity, species identities, and relative abundances; and (b) is there an interactive effect between the pressures exerted by deer and the well-documented effects of fire in driving plant community responses? Location: This study took place at the Konza Prairie Biological Station in northeastern Kansas, USA. Methods: Using a 22-year deer exclosure experiment, we examined differences in plant species richness, evenness, and plant community composition between plots that were either accessible or inaccessible to deer, in areas burned annually or once every four years. Results: We did not find significant effects of deer or interactive effects between deer and burning frequency on any metric of the plant community measured, including plant species richness, evenness, and plant community composition. Conclusions: Contrary to the impact that deer have in other ecosystems (e.g. forests), our results indicate that deer do not affect the plant community of herbaceous-dominated tallgrass prairies. These results indicate that while the loss of bison-grazers has shifted tallgrass prairie plant communities to C 4 grass-dominated systems, the shift to browsing-dominated herbivore pressure from deer has a minimal effect on the plant community. 900 | Journal of Vegetation Science BLOODWORTH eT aL.

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Section: Introductionmentioning

confidence: 99%

Effects of white‐tailed deer exclusion on the plant community composition of an upland tallgrass prairie ecosystem

Bloodworth

Ritchie

Komatsu

2020

J Vegetation Science

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“…2) in this region is much less controversial. Like all the other savannas in North America (Fowler and Beckage 2019), eastern Edwards Plateau savannas are assumed to have been created and maintained by some mix of lightningstarted and anthropogenic fire that slowed or reversed woody plant encroachment (Smeins 1980; solid circular arrow under C in Fig. 2).…”

Section: Roles Of Fire In Eastern Edwards Plateau Savannasmentioning

confidence: 99%

Roles of fire in the plant communities of the eastern Edwards Plateau of Texas

Fowler,

Carden

2024

fire ecol

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Background The eastern Edwards Plateau supports a mosaic of woodlands, savannas, and shrubland in which native plant and animal species are often still dominant. Some woodlands are dominated by a mix of native woody species, including Ashe juniper (Juniperus ashei), oak species (Quercus spp.), and other hardwoods. Other woodlands are nearly pure Ashe juniper; these are particularly susceptible to crown fires. The savannas were once, and still can be, maintained by surface fires. Results We hypothesize that frequent surface fires once kept some of the mixed woodlands more open and more diverse (a “lost community”) and that these fires would have reduced the abundance of Ashe juniper, which does not resprout from the base, and allowed oak regeneration, which is currently failing. The absence of fire, the current failure of oak regeneration, and high white-tailed deer densities together favor the “juniperization” of woodlands, that is, the conversion of mixed woodlands into nearly pure stands of Ashe juniper. Surface fires in savannas can sometimes control woody encroachment and the non-native grass King Ranch bluestem (Bothriochloa ischaemum), although the particular fire characteristics required are not yet clear. The current lack of fire in savannas favors their conversion to woodlands. Since under present conditions Ashe juniper is the primary encroacher, without fire or mechanical clearing these savannas are also on trajectories towards nearly pure stands of Ashe juniper. Conclusions Prescribed fire, sometimes paired with mechanical thinning, offers land managers in this region a tool for achieving many goals, including increasing native biodiversity and reducing wildfire danger. However, more study of the effects of fires of different intensities and frequencies in these woodlands, savannas, and shrublands is needed to better inform the use of prescribed fire in this region.

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“…However, the conservation of these ecosystems is often overlooked because accurately defining and characterizing them is challenging. Savannas exhibit remarkable diversity in that they may be dominated by either woody or herbaceous plant species; typically, those having low percentages of woody cover are classified as grasslands, and those having high percentages of woody cover are classified as closed-canopy woodlands (Fowler and Beckage, 2019). This results in conservation efforts that aim to either afforest or deforest natural savannas to better align with their classification.…”

Section: Introductionmentioning

confidence: 99%

“…The diverse collections of open-canopy savannas in subtropical and temperate regions have received comparatively little attention, despite the fact that these ecosystems exhibit more distinct characteristics than their tropical counterparts. It is estimated that across North America, there exist thirteen distinct types of savannas-six which are found in the state of Texas (Fowler and Beckage, 2019). Many of the open-canopy savanna ecosystems in Texas have undergone a process of woody plant encroachment (WPE), resulting in their transformation to shrublands or woodlands.…”

Section: Introductionmentioning

confidence: 99%

Examining changes in woody vegetation cover in a human-modified temperate savanna in Central Texas between 1996 and 2022 using remote sensing

Olariu,

Wilcox,

Popescu

2024

Front. For. Glob. Change

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Savanna ecosystems across the globe have experienced substantial changes in their vegetation composition. These changes can be attributed to three main processes: (1) encroachment, which refers to the expansion of woody plants into open areas, (2) thicketization, which is characterized by the growth of sub-canopy woody plants, and (3) disturbance, defined here as the removal of woodland cover due to both natural forces and human activities. In this study, we utilized Landsat surface reflectance data and Sentinel-1 SAR data to track the progression of these process from 1996 to 2022 in the significantly modified Post Oak Savannah ecoregion of Central Texas. Our methodology employs an ensemble classification algorithm, which combines the results of multiple models, to develop a more precise predictive model, along with the spectral–temporal segmentation algorithm LandTrendr in Google Engine (GEE). Our ensemble classification algorithms demonstrated high overall accuracies of 94.3 and 96.5% for 1996 and 2022, respectively, while our LandTrendr vegetation map exhibited an overall accuracy of 80.4%. The findings of our study reveal that 9.7% of the overall area experienced encroachment of woody plants into open area, while an additional 6.8% of the overall area has transitioned into a thicketized state due to the growth of sub-canopy woody plants. Furthermore, 5.7% of the overall area encountered woodland disturbance leading to open areas. Our findings suggest that these processes advanced unevenly throughout the region, resulting in the coexistence of three prominent plant communities that appear to have long-term stability: a dense deciduous shrubland in the southern region, as well as a thicketized oak woodland and open area mosaic in the central and northern regions. The successional divergence observed in these plant communities attests to the substantial influence of human modification on the landscape. This study demonstrates the potential of integrating passive optical multispectral data and active SAR data to accurately map large-scale ecological processes.

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Savannas of North America

Cited by 7 publications

References 128 publications

Effects of white‐tailed deer exclusion on the plant community composition of an upland tallgrass prairie ecosystem

Effects of white‐tailed deer exclusion on the plant community composition of an upland tallgrass prairie ecosystem

Roles of fire in the plant communities of the eastern Edwards Plateau of Texas

Examining changes in woody vegetation cover in a human-modified temperate savanna in Central Texas between 1996 and 2022 using remote sensing

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