Stand Structure and Allometry of Trees During Self-Thinning of Pure Stands

Mohler, Charles L.; Marks, P. L.; SPRUGELt, D. G.

doi:10.2307/2259153

Cited by 323 publications

(252 citation statements)

References 19 publications

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“…This change in population structure has been reported in a large number of terrestrial species (e.g. Koyama & Kira, 1956;Obeid et aL, 1967;Ford, 1975;Mohler et al, 1978). Changes in seaweed population structures have been reported only for plants of a visible size, yet a knowledge of early population structure is fundamental to our understanding of seaweed population dynamics.…”

Section: Introductionmentioning

confidence: 55%

“…Furthermore, because canopy-cleared areas were large, discs were spatially separated from source plants by up to 2 m, and dispersal ranges in fucoids may limit propagule supply at this scale (Norton, 1992;Chapman, 1995). The experimental monitoring of the F. serratus populations was designed to test a particular assumption widespread in plant demography that a population of seeds (or gametes or zygotes) starts with a normally distributed, narrow range of plant sizes, but that the population develops a positive skew and a size hierarchy as individual plants become more variable in size (Koyama & Kira, 1956;Stern, 1965;Obeid et al, 1967;Ogden, 1970;White & Harper, 1970;Ford, 1975;Mohler et al, 1978;Turner & Rabinowitz, 1983;Higgins et al, 1984;Weiner & Solbrig, 1984;Weiner, 1985;Schmitt et al, 1986;Weiner & Thomas, 1986;Bonan, 1988;Bendel et al, 1989). Unfortunately there is little evidence to support or refute this in microscopic seaweed populations as no population studies have been concerned with size distributions of gametes, newly settled zygotes or very small germlings/"embryos".…”

Section: Discussionmentioning

confidence: 99%

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The development of size structure in a youngFucus serratuspopulation

Creed

Norton

Harding

1996

European Journal of Phycology

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Artificial discs were used to monitor the settlement and development of Fucus serratus propagules in five areas cleared of an adult canopy, in order to test the assumptions that sizes of recently settled propagules are normally distributed but that over time plant sizes become more variable and hierarchical. Settlement was spatially (3-20 m) variable only at the beginning and end of the settlement period, and at the time when most settlement took place (88% in a fortnight) no differences between areas were found. Increases in the skewness coefficient, Gini coefficient and coefficient of variation confirmed that there was not a size hierarchy in the recently settled population, but 8 months later sizes of plants were variable and a positive skew in plant sizes (many small and few big) developed. Mortality was high at first (70% in 1 month) but fell considerably later. F. serratus behaves like most higher plants with respect to changing population structure. The observed change in population structure provided evidence of how a "seed bank" develops in an algal population, as I year after settlement an estimated 37 000 plants m 1 are still

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Section: Introductionmentioning
confidence: 55%

Section: Discussionmentioning
confidence: 99%

The development of size structure in a youngFucus serratuspopulation
Creed
¹
,
Norton
²
,
Harding
³

1996
European Journal of Phycology
24
0
13
1
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“…For example, Mohler et al (1978) presented an analysis in which the correlation between log m arid log N was reasonably high (r2 = 0.72), yet the regression slope, y = -1.2 1, was less steep than the PCA estimate, y = -1.52. Since most thinning lines have been fit by regression (Westoby 1984), there may be an important bias toward underestimating the steepness of thinning slopes, particularly since for many size-density correlations r2 is well below 1 when the data are correctly analyzed in log B-log N form (Weller 1985).…”

Section: Fitting the Self-thinning Linementioning
confidence: 99%

A Reevaluation of the ‐3/2 Power Rule of Plant Self‐Thinning
Weller¹
1987
Ecological Monographs
423
13
369
6
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Abstract. The self-thinning rule predicts that for a crowded even-aged plant population a log-log plot of average plant mass vs. plant density will reveal a straight "self-thinning" line of slope -%. The rule is supported by examples from many individual populations, and by the existence of an interspecific relationship that yields a line of slope -% in a loglog plot displaying average mass and density data from many populations of different species. I examined and reanalyzed the evidence to evaluate the strength of support for this widely accepted rule.Some problems in fitting thinning lines and testing agreement with the rule have no truly satisfactory solution, but three improvements on commonly used methods were made: the analysis related stand biomass density to plant density because the alternative of relating average plant mass to plant density is statistically invalid; principal components analysis was used rather than regression, because regression relies on unrealistic assumptions about errors in the data; and statistical tests of hypotheses were used to interpret the results.The results of this reanalysis were that 19 of 63 individual-population data sets previously cited in support of the thinning rule actually showed no significant correlation between stand biomass density and plant density, and 20 gave thinning slopes significantly different ( P < .05) from the thinning rule prediction. Four other analyses provided additional evidence against a single quantitative thinning rule for all plants: slopes of the thinning lines were more variable than currently accepted, differed significantly among plant groups, were significantly correlated with shade tolerance in forest trees, and differed among stands of the same species. The same results held for the intercepts of self-thinning lines.Despite the failure of the thinning rule for individual populations, the combined data for all populations are still consistent with an interspecific relationship of slope -3/,; therefore, the existence of the interspecific relationship does not necessarily support the withinpopulation thinning rule. The within-population and interspecific relationships are apparently different phenomena that may arise from different constraints, so the two relationships should be tested and explained separately. power law.The self-thinning rule (also called the -% power rule or Yoda's law) describes a relationship between size and density in even-aged plant populations that are crowded but actively growing. If competition from other populations and crowding-independent stresses (drought, fire, disease, etc.) are absent, mortality or "thinning" is caused by competition within the population, hence the term "self-thinning." Yoda et al. Two lines of evidence support this relationship as an ecological "rule" or "law" governing even-aged plant populations. First, the slopes of many reported thinning lines are near y = -%, including data from monospecific populations ranging in size from small herbs to large trees , White and Harper 1970, Wh...

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“…A simple least-squares line is therefore inappropriate (Mohler et al 1978). Hutchings & Budd (1981) overcame this by subjectively excluding plots where self-thinning did not seem to be occurring.…”

Section: Discussionmentioning
confidence: 99%

The -3/2 law applied to some gorse communities, with consideration of line fitting
Wilson
¹
,
Lee
²

1988
New Zealand Journal of Botany
6
0
3
0
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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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Stand Structure and Allometry of Trees During Self-Thinning of Pure Stands

Cited by 323 publications

References 19 publications

The development of size structure in a youngFucus serratuspopulation

The development of size structure in a youngFucus serratuspopulation

A Reevaluation of the ‐3/2 Power Rule of Plant Self‐Thinning

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

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