Correlated Changes in Plant Size and Number in Plant Populations

White, James; Harper, John L.

doi:10.2307/2258284

Cited by 430 publications

(272 citation statements)

References 14 publications

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“…Once at or near the boundary line, stands typically begin to 'self-thin', becoming less dense through mortality of weak or suppressed trees that are out-competed for light and nutrients by dominant and co-dominant trees. Historically, researchers have hypothesized that the slope of the boundary line should be )3 ⁄ 2, a geometric relationship between the two variables with biomass (a cubic measure) on the y-axis vs. density (a squared measure) on the x-axis (White & Harper 1970). Accumulating empirical evidence and theoretical derivations invoking allometric scaling relationships now suggest that the slope of this line may be closer to )4 ⁄ 3, conforming to the widely reported population density-mass ¾ relationship, once the axes are inverted (West, Brown & Enquist 1997;Farrell-Gray & Gotelli 2005).…”

Section: Methodsmentioning

confidence: 99%

Subcontinental impacts of an invasive tree disease on forest structure and dynamics

et al. 2011

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Summary1. Introduced pests and pathogens are a major source of disturbance to ecosystems world-wide. The famous examples have produced dramatic reductions in host abundance, including virtual extirpation, but most introductions have more subtle impacts that are hard to quantify but are potentially at least as important due to the pathogens' effects on host reproduction, competitive ability and stress tolerance. A general outcome could be reduced host abundance with concomitant increases in the abundance of competitors. 2. Beech bark disease (BBD) is a widespread, fatal affliction of American beech (Fagus grandifolia), currently present in c. 50% of beech's distribution in eastern North America. Despite high adult mortality, beech remains a dominant component of the forest community. 3. Employing spatially extensive data from the national Forest Inventory and Analysis program of the United States Forest Service, we show that forests have changed dramatically in the presence of BBD. Within the 2.3 million km 2 range of beech, size-specific mortality was 65% higher in the longest-infected regions, and large beech ( >90 cm diameter at breast height) have declined from c. 79 individuals km )2 to being virtually absent. Small stem beech density was dramatically higher ( >350%) such that infested forests contain a roughly equivalent cross-sectional (basal) area of beech as before BBD. 4. There was no evidence for compensation by sugar maple or other co-occurring tree species via increased recruitment or adult survivorship at the landscape scale. Overall, community composition remained roughly unchanged as a result of BBD. 5. Surprisingly, trajectory of stand dynamics (shifts in stem density and mean tree size reflecting normal stand maturation (self-thinning) or retrogression (more abundant, smaller trees over time)) did not differ between affected and unaffected regions. Variance in stand dynamics was greater in afflicted forests, however, indicating that predictability of forest structure has been diminished by BBD. 6. Synthesis. Forests of eastern North America have shifted to increased density and dramatically smaller stature -without notable change in tree species composition -following the invasion of a novel forest disease. Our results reinforce the conclusion that introduced diseases alter fundamental properties of ecosystems, but indicate that the spectrum of potential effects is broader than generally appreciated.

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Section: Methodsmentioning

confidence: 99%

Subcontinental impacts of an invasive tree disease on forest structure and dynamics

et al. 2011

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“…This study adds to the small number of reports (White & Harper 1970, Bazzaz & Harper 1976, Malmberg & Smith 1982, White 1985 which suggest that it can be applied to mixed communities. Unlike most of the latter studies, which have examined experimental communities, this study shows that it applies to natural mixed communities.…”

Section: Discussionmentioning

confidence: 88%

“…This was intended to indicate only proportional differences, not absolute volumes. For practical reasons, such indirect estimates of size have normally been used in weight/density studies with woody plants (e.g., White & Harper 1970, Gibson & Good 1986.…”

Section: Methodsmentioning

confidence: 99%

The -3/2 law applied to some gorse communities, with consideration of line fitting

Wilson

Lee

1988

New Zealand Journal of Botany

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A "self-thinning" line is fitted to size/ density data from gorse (Ulex europaeus L.) communities around Dunedin, New Zealand. Three methods of line fitting were triedwunweighted least squares, weighted least squares, and weighted least absolute deviations regressions; they yielded similar results. The slope of the fitted line depends on whether other species are included, and whether dead material is excluded. If both are done, the fitted slope is close to the theoretical-3/2 (-1.5).

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“…A description of the distribution of sizes is a common starting point for many demographic studies (e.g. [1][2][3]). This is especially the case for plants, where size distributions are often considered to convey information regarding the stage of development of a stand or the processes occurring within a population [4].…”

Section: Introductionmentioning

confidence: 99%

“…This is particularly likely to be the case for light competition among vascular plants, where taller stems capture a greater proportion of available radiation and determine access for those beneath [18]. As larger individuals can thereby maintain higher growth rates, incipient bimodality will be reinforced [12], at least until light deprivation causes mortality among smaller individuals [1]. Stand development models are able to generate bimodal patterns when resources for growth become limited [19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Asymmetric competition causes multimodal size distributions in spatially structured populations

et al. 2016

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Plant sizes within populations often exhibit multimodal distributions, even when all individuals are the same age and have experienced identical conditions. To establish the causes of this, we created an individual-based model simulating the growth of trees in a spatially explicit framework, which was parametrized using data from a long-term study of forest stands in New Zealand. First, we demonstrate that asymmetric resource competition is a necessary condition for the formation of multimodal size distributions within cohorts. By contrast, the legacy of small-scale clustering during recruitment is transient and quickly overwhelmed by density-dependent mortality. Complex multi-layered size distributions are generated when established individuals are restricted in the spatial domain within which they can capture resources. The number of modes reveals the effective number of direct competitors, while the separation and spread of modes are influenced by distances among established individuals. Asymmetric competition within local neighbourhoods can therefore generate a range of complex size distributions within even-aged cohorts.

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Correlated Changes in Plant Size and Number in Plant Populations

Cited by 430 publications

References 14 publications

Subcontinental impacts of an invasive tree disease on forest structure and dynamics

Subcontinental impacts of an invasive tree disease on forest structure and dynamics

The -3/2 law applied to some gorse communities, with consideration of line fitting

Asymmetric competition causes multimodal size distributions in spatially structured populations

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