Herbaceous Layer Species Richness of Southeastern Forests and Woodlands

Peet, Robert K.; Palmquist, Kyle A.; Tessel, Samantha M.

doi:10.1093/acprof:osobl/9780199837656.003.0010

Cited by 29 publications

(50 citation statements)

References 46 publications

(67 reference statements)

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“…Forb richness also increased with increasing calcium availability in both seasons and at both spatial scales (Figures a,b and a,b). The strength and persistence of this particular trend throughout our study, as well as its prevalence in the literature (Bellemare et al, ; Burton et al, ; McEwan & Muller, ; Peet et al, ), suggests it is worth further consideration. We note that mean calcium is also highly correlated with pH and potassium variability (Figure ).…”

Section: Discussionsupporting

confidence: 60%

Novel insights into how the mean and heterogeneity of abiotic conditions together shape forb species richness patterns in the Allegheny plateau ecoregion

Catella

Eysenbach

Abbott

2019

Ecology and Evolution

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While plant community theory tends to emphasize the importance of abiotic heterogeneity along niche axes, much empirical work seeks to characterize the influence of the absolute magnitude of key abiotic variables on diversity. Both magnitude (as reflected, e.g., by a mean) and heterogeneity (variance) in abiotic conditions likely contribute to biodiversity patterns in plant communities, but given the large number of putative abiotic drivers and the fact that each may vary at different spatiotemporal scales, the challenge of linking observed biotic patterns with the underlying environment remains acute. Using monitoring data from a natural resource agency, we compared how well statistical models of the mean, heterogeneity, and both the mean and heterogeneity combined of 17 abiotic factor variables explained patterns of forb species richness in Northeast Ohio, USA. We performed our analyses at two spatial scales, repeated in spring and summer across four forest types. Although all models explained a great deal of the variance in species richness, models including both the mean and heterogeneity of different abiotic factors together outperformed models including either the mean or the heterogeneity of abiotic factors alone. Variability in forb species richness was mostly due to changes in mean calcium levels regardless of forest type. After accounting for forest type, we were able to attribute variation in forb species richness to changes in the heterogeneity of different abiotic factors as well. Our results suggest that multiple mechanisms act simultaneously according to different aspects of the abiotic environment to structure forb communities, and this underscores the importance of considering both the magnitude of and heterogeneity in multiple abiotic factors when looking for links between the abiotic environment and plant community patterns. Finally, we identify novel patterns across spatial scales, forest types, and seasons that can guide future research in this vein.OPEN RESEARCH BADGES This article has earned an Open Data Badge for making publicly available the digitally‐shareable data necessary to reproduce the reported results. The data is available at https://doi.org/10.5061/dryad.kp3cb17.

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Section: Discussionsupporting

confidence: 60%

Novel insights into how the mean and heterogeneity of abiotic conditions together shape forb species richness patterns in the Allegheny plateau ecoregion

Catella

Eysenbach

Abbott

2019

Ecology and Evolution

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“…This site is the source of the North American records of 42 species in 0.25 m 2 and 52 species in 1 m 2 (see Peet et al. , ), values which rival those reported for other species‐rich grasslands throughout the world (Kull & Zobel ; Cantero et al. ; Klimeš et al.…”

Section: Introductionmentioning

confidence: 65%

“…; Peet et al. ). In addition to disturbance, grassland community structure is influenced by seasonal, periodic, and multi‐year drought events (Gibson & Hulbert ), which can have prolonged consequences (Haddad et al.…”

Section: Introductionmentioning

confidence: 98%

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Changes in plant species richness following reduced fire frequency and drought in one of the most species‐rich savannas in North America

Palmquist

Peet

Weakley

2014

J Vegetation Science

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Questions: How has plant species richness changed over two decades in one of the most species-rich savannas in North America? Is an altered disturbance regime, environmental stress, or both, driving these changes? In what ways can observations in this savanna inform management of other species-rich plant communities?Location: Longleaf pine savannas in southeast North Carolina, USA. Methods:In 2011-2013, we re-surveyed permanent plots established in the 1980s and 1990s in a longleaf pine (Pinus palustris) savanna in North Carolina to quantify changes in species richness at multiple spatial scales following 15 yr of reduced fire frequency plus periodic drought. For comparison, we re-sampled other longleaf pine savannas in the region that had not experienced reduced fire frequency, but had experienced similar drought. In addition, we identified which types of species were lost and gained, and summarized changes in species frequency by growth form, plant height, and habitat affinity. Results:We detected substantial declines in small-scale species richness and species frequency from the 1980s to 2011, representing a loss of 33% to 41% of the flora, depending on the spatial scale. Small herbaceous species had become particularly scarce. Additional re-sampling in the wetter years of 2012 and 2013 after consecutive years of fire revealed that species richness had increased slightly from 2011, but was still considerably lower than that in the 1980s. Other savannas did not exhibit such dramatic declines in species richness, suggesting reduced fire frequency in addition to drought contributed to species loss in Big Island Savanna over time.Conclusions: Our work suggests that nearly annual fire is necessary for the maintenance of high plant species richness in mesic longleaf pine savannas, and even a modest reduction in fire frequency can have dramatic negative impacts. This study also suggests that drought is an important factor structuring grassland ecosystems in the southeastern US, despite relatively high regional precipitation. We believe these findings can be generalized to other species-rich grasslands that are sensitive to changes in disturbance regimes and may require frequent disturbance to maintain plant species richness.

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“…, Peet et al. , Veldman et al. ) expressed through engineering of fire by pyrogenic fuels, might well set the stage for mesic and high rainfall savannas becoming high diversity landscapes.…”

Section: Discussionmentioning

confidence: 99%

Pyrogenic fuels produced by savanna trees can engineer humid savannas

Platt

Ellair

Huffman

et al. 2016

Ecological Monographs

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Natural fires ignited by lightning strikes following droughts frequently are posited as the ecological mechanism maintaining discontinuous tree cover and grass‐dominated ground layers in savannas. Such fires, however, may not reliably maintain humid savannas. We propose that savanna trees producing pyrogenic shed leaves might engineer fire characteristics, affecting ground‐layer plants in ways that maintain humid savannas. We explored our hypothesis in a high‐rainfall, frequently burned pine savanna in which the dominant tree, longleaf pine (Pinus palustris), produces resinous needles that become highly flammable when shed and dried. We postulated that pyrogenic needles should have much greater influence on fire characteristics at ground level, and hence post‐fire responses of dominant shrubs and grasses, than other abundant fine fuels (shed oak leaves and grass culms). We further reasoned that these effects should increase with amounts of needles. We managed site conditions that affect fuels (time since fire, dominant vegetation), manipulated amounts of needles in ground‐layer plots, prescribed burned the plots, and measured fire characteristics at ground level. We also measured characteristics of ground‐layer oaks and grasses before, then 2 and 8 months after fires. We tested our hypotheses regarding effects of pyrogenic pine fuels on fire characteristics and vegetation regrowth and explored direct and indirect effects of fuels on fire characteristics and vegetation using a structural equation model. Pine needles influenced fire characteristics, elevating maximum temperature increases, durations of heating above 60°C, and fine fuel consumption considerably above measurements when fuels only included other savanna plants. Presence of pine needles depressed post‐fire numbers of oak stems and grass culms, especially in the interior of grass genets, as well as post‐fire flowering of grasses. The structural equation model indicated strong direct and indirect pathways from pine needles to post‐fire responses of oaks and grasses. The experimental field tests of hypotheses, bolstered by structural equation modeling, indicate pyrogenic fine fuels modify characteristics of prescribed fires at ground level, negatively affecting dominant ground‐layer oaks and grasses. Frequent fires fueled by pyrogenic needles should maintain humid savannas and generate spatial pyrodiversity that affects composition and dynamics of pine savanna ground‐layer vegetation.

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Herbaceous Layer Species Richness of Southeastern Forests and Woodlands

Cited by 29 publications

References 46 publications

Novel insights into how the mean and heterogeneity of abiotic conditions together shape forb species richness patterns in the Allegheny plateau ecoregion

Novel insights into how the mean and heterogeneity of abiotic conditions together shape forb species richness patterns in the Allegheny plateau ecoregion

Changes in plant species richness following reduced fire frequency and drought in one of the most species‐rich savannas in North America

Pyrogenic fuels produced by savanna trees can engineer humid savannas

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