100 Influential Papers - page 11

POPU L AT I ON DYNAM I C S
Sarukhán, J. & Harper, J.L. (1973)
Studies on plant demography:
Ranunculus repens
L.,
R. bulbosus
L. and
R. acris
L. I. Population flux
and survivorship.
Journal of Ecology, 61, 675-716.
In his seminal ‘Darwinian approach’ paper [see (1967)
Journal of Ecology
,
55
, 247-270; on p. 10] Harper highlighted the almost total
neglect of studies on plant numbers, a neglect that had hindered development of plant ecology within both population dynamics and life
history evolution. A surge of papers on plant demography followed, and in the early 1990s the time was ripe for a first general synthesis
of plant demography [see Silvertown
et al
. (1993)
Journal of Ecology
,
81
, 465-476 see below]. An essential inspiration for this tremendous
growth of knowledge on the details of plant population dynamics was the study on three buttercup species by Jose Sarukhán in a field
in Caernarvonshire, Wales. During a period of two years from spring 1969, Sarukhán made continuous detailed recordings of every
single plant in permanent plots, from seedlings to mature adults, using a pantograph. This methodology would set the standards for
later studies on plant demography. The two years of trying field work rewarded Sarukhán with several new insights into the life of plant
populations, e.g. the large dynamic flux of individuals despite rather stable population sizes, detailed estimates of plant turnover, life-
length and reproductive output, and, perhaps most important for later population analyses, the basis for estimates of vital rates.
Ove Eriksson
10
Silvertown, J., Franco, M., Pisanty, I.
& Mendoza, A. (1993)
Comparative plant demography – relative
importance of life-cycle components to
the finite rate of increase in woody and
herbaceous perennials.
Journal of Ecology,
81, 465-476.
How can ecologists make meaningful comparisons
of the demography of plants as contrasting in life
history as annual weeds and giant redwoods? Such
comparisons make apples and oranges seem like
close cousins. This paper pioneered the use of stage
projection matrices to compare large numbers of
species, compiling data for 66 herbs, shrubs and trees.
It uses the finite rate of population increase (
λ
) and
the elasticity of matrix elements (a measure of an
element’s contribution to fitness) to make meaningful
comparisons of the growth, survival and fecundity
of this diverse array of species, showing clear trade-
offs among life-cycle components and a separation
of functional groups in demography space. Over 300
plant matrix modelling papers have been published
since 1993 using ever-more sophisticated techniques,
but this paper remains as a leading example of how
the technique can be used to compare the ecology of
species.
David Coomes
11
12
11
1
Mohler, C.L., Marks, P.L. & Sprugel, D.G. (1978)
Stand structure and allometry of trees during
self-thinning of pure stands.
Journal of Ecology,
66, 599-614.
Self-thinning is one of the major phenomena of plant
populations. Mohler, Marks & Sprugel evaluated the -3/2
power relationship between tree density and average tree
biomass, proposed by Yoda, Kira, Ogawa and Hozumi, along
the development of even-aged pure stands of pin cherry and
balsam fir, with allometric properties between size dimensions
that are used to estimate tree biomass, and the change in size
structure with stand age. Their study was attractive for various
reasons: (1) the two target stands were contrasted in that pin
cherry is shade-intolerant whereas balsam fir is shade-tolerant;
(2) a bivariate model fitting was employed, which is statistically
appropriate; and (3) interaction between crowding and tree
allometry was suggested. To relate individual architecture,
resource competition, population structure and dynamics, and
ecosystem properties in carbon accumulation and turnover is
a central issue of ecology, and this paper keeps its significance
for this reason. This study has been followed by many empirical
and theoretical studies, including critical meta analyses, that
encourage ecologists to employ stand biomass rather than
average tree biomass for discriminating statistical problems,
and in building the metabolic theory of allometry.
Takashi S Kohyama
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