Correlates of geoxyle diversity in Afrotropical grasslands

Meller, Paulina; Stellmes, Marion; Fidelis, Alessandra; Finckh, Manfred

doi:10.1111/jbi.14305

Cited by 12 publications

(11 citation statements)

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“…For Ziziphus , fire frequency aligns with shrub and tree forms whereas the one species of Ziziphus with a geoxylic habit is associated with seasonality of temperature (Figure 3a). This association is replicated in other geoxylic species (Meller et al, 2021) in genera such as Protea (Lamont et al, 2017) and Parinari (Gomes et al, 2019).…”

Section: Discussionmentioning

confidence: 76%

“…Diversity in habits and the utility of the Ziziphus species have compounded to expand the range and environmental occupation of the genus over evolutionary and human timescales. Liana species are restricted to closed biomes and the geoxylic habit is found only in open biomes, replicating broader geoxylic patterns (Maurin et al, 2014; Meller et al, 2021). Further, habit is significantly associated with range size, with trees having on average larger range sizes than shrubs, lianas, and geoxyles.…”

Section: Discussionmentioning

confidence: 80%

“…The geoxylic habit is nested within the environmental space occupied by trees (Figure 3a) which may be because, beyond habit, geoxylic traits do not consistently differ substantially from their tree congeners (Gomes et al, 2019; Meerts, 2017). Environmental factors which drive the geoxylic habit are often related to frost (Finckh et al, 2016) and fire (Lamont et al, 2017; Maurin et al, 2014) or both in combination with herbivory (Meller et al, 2021). For Ziziphus , fire frequency aligns with shrub and tree forms whereas the one species of Ziziphus with a geoxylic habit is associated with seasonality of temperature (Figure 3a).…”

Section: Discussionmentioning

confidence: 99%

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Diversity in habit expands the environmental niche of Ziziphus (Rhamnaceae)

2022

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Functional traits are a way to infer processes from pattern, and as such are used to disentangle the macroecology and biogeography of plant families (e.g., Onstein et al., 2019;Xue et al., 2020) and biomes (e.g., Gomes et al., 2020;Solofondranohatra et al., 2018), but only infrequently plant genera (although see Proches et al., 2012;Pezzini et al., 2021). As morpho-physio-phenological characters, functional traits relate to the life history strategies of plants that embody growth, reproduction, and survival (Violle et al., 2007) and indicate how species relate to the environment. Fruit traits have been used to interpret the fossil record and infer genus-level paleo-distribution

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Section: Discussionmentioning

confidence: 76%

Section: Discussionmentioning

confidence: 80%

Section: Discussionmentioning

confidence: 99%

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Diversity in habit expands the environmental niche of Ziziphus (Rhamnaceae)

2022

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“…In high fire exposure the underground stem (geoxylic) structure of certain hedge formers ( Euclea racemosa, Olea exasperata, Rapanea gilliana, Searsia laevigata ) is likely an adaptation to recurrent fire ( Maurin et al, 2014 ; Lamont, He & Pausas, 2017 ; Meller et al, 2022 ) and, given our knowledge of the sequential temporal emergence of dominant disturbance regimes (herbivory vs . fire) through evolutionary history ( Cowling et al, 2005 ; Keeley & Rundel, 2005 ; Pennington et al, 2010 ), we would expect these geoxylic species to be more recently diversified than their laterally-spreading or vertically-growing sister species.…”

Section: Discussionmentioning

confidence: 99%

Canopy plant composition and structure of Cape subtropical dune thicket are predicted by the levels of fire exposure

Strydom

Kraaij

Grobler

et al. 2022

PeerJ

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Background The subtropical dune thicket (hereafter “dune thicket”) of the Cape Floristic Region experiences a wide range of fire exposure throughout the landscape, unlike other dry rainforest formations that rarely experience fire. We sought to determine how fire exposure influences species composition and the architectural composition of dune thicket. Methods We used multivariate analysis and diversity indices based on cover abundance of species to describe the species composition, architectural guild composition and structure of dune thicket sites subject to different levels of fire exposure, namely low (fire return interval of >100 years), moderate (fire return interval of 50–100 years), and high (fire return interval of 10–50 years). Results The diversity, cover abundance and architectural guild cover abundance of dune thicket canopy species were strongly influenced by the level of fire exposure such that each level was associated with a well-circumscribed vegetation unit. Dune thickets subject to low fire exposure comprises a floristically distinct, low forest characterized by shrubs with one-to-few upright stems (ca. 4–8 m tall) and a relatively small canopy spread (vertical growers). Of the 25 species in this unit, 40% were restricted to it. Dune thickets subject to moderate fire exposure had the highest abundance of lateral spreaders, which are multi-stemmed (ca. 3–6 m tall) species with a large canopy spread and lower stature than vertical growers. None of the 17 species found in this unit was restricted to it. Dune thickets subject to high fire exposure had the highest abundance of hedge-forming shrubs, these being low shrubs (ca. 0.6–1.4 m tall), with numerous shoots arising from an extensive system of below-ground stems. Of the 20 species in this unit, 40% were restricted to it. Multivariate analysis identified three floristic units corresponding to the three fire exposure regimes. Compositional structure, in terms of species and architectural guilds, was most distinctive for dune thickets subject to high and low fire exposure, while the dune thicket subject to moderate fire exposure showed greatest compositional overlap with the other units. Conclusion Fire exposure profoundly influenced the composition and structure of dune thicket canopy species in the Cape Floristic Region. In the prolonged absence of fire, the thicket is invaded by vertical-growing species that overtop and outcompete the multi-stemmed, laterally-spreading shrubs that dominate this community. Regular exposure to fire selects for traits that enable thicket species to rapidly compete for canopy cover post-fire via the prolific production of resprouts from basal buds below- and above-ground. The trade-off is that plant height is constrained, as proportionately more resources are allocated to below-ground biomass.

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“…Biomass allocation also remains poorly documented in geoxyles, whose biomass is disproportionately found belowground. Geoxyles are plants with short-lived reproductive aerial branches and woody underground structures (xylopodia) (Maurin et al, 2014;Meller et al, 2022), and these are common in regions with frequent fires such as African savannas and the cerrado in Brazil (Maurin et al, 2014;Meller et al, 2022). Geoxyles may provide the next frontier of research in biomass allocation in biomes that experience frequent disturbance by fire.…”

Section: Belowground Biomass Vs Aboveground Biomassmentioning

confidence: 99%

Allometric scaling and allocation patterns: Implications for predicting productivity across plant communities

Sileshi¹,

Nath²,

Kuyah³

2023

Front. For. Glob. Change

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As the application of allometry continues to expand, the variability in the allometry exponent has generated a great deal of debate in forest ecology. Some studies have reported counterintuitive values of the exponent, but the sources of such values have remained both unexplored and unexplained. Therefore, the objectives of our analyses were to: (1) uncover the global patterns of allometric variation in stem height with stem diameter, crown radius with stem diameter or stem height, crown depth with stem diameter, crown volume with stem diameter, crown depth with crown diameter, aboveground biomass with stem diameter or height, and belowground biomass with aboveground biomass; (2) assess variations in allometry parameters with taxonomic levels, climate zones, biomes and historical disturbance regimes; and (3) identify the sources of counterintuitive values of the allometry exponents. Here, we provide novel insights into the tight allometric co-variations between stem and crown dimensions and tree biomass. We also show a striking similarity in scaling across climate zones, biomes and disturbance regimes consistent with the allometry constraint hypothesis. We show that the central tendency of the exponent is toward 2/3 for the scaling of stem height with diameter, crown dimensions with stem diameter and height, 5/2–8/3 for the scaling of aboveground biomass with stem diameter, and 1 for the scaling of belowground biomass with aboveground biomass. This is indicative of an integrated growth regulation acting in tandem on growth in stem diameter, height, crown dimensions and biomass allocation. We also demonstrate that counterintuitive values of the exponent arise as artifacts of small sample sizes (N < 60), measurement errors, sampling biases and inappropriate regression techniques. We strongly recommend the use of larger sample sizes (N > 60) and representative samples of the target population when testing hypothesis about allometric variation. We also caution against conflation of statistical artifacts with violations of theoretical predictions.

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Correlates of geoxyle diversity in Afrotropical grasslands

Abstract: This is an open access article under the terms of the Creat ive Commo ns Attri bution-NonCo mmercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

Cited by 12 publications

References 115 publications

Diversity in habit expands the environmental niche of Ziziphus (Rhamnaceae)

Diversity in habit expands the environmental niche of Ziziphus (Rhamnaceae)

Canopy plant composition and structure of Cape subtropical dune thicket are predicted by the levels of fire exposure

Allometric scaling and allocation patterns: Implications for predicting productivity across plant communities

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