A generalized law of self-thinning in plant populations (self-thinning in plant populations).
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Models, Biological↗
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[Neural network based on modified simplex method and its application in studying forest self-thinning].
The mechanism of forest self-thinning is generally nonlinear and dynamic, and the artificial neural network has the characteristic of expressing arbitrary nonlinear mapping. In this paper, the feasibility and limitation of artificial neural network used to simulating forest self-thinning was expounded, and the principle and algorithms of the neural network model based on modified simplex method (BP-MSM mixed algorithms) for modeling forest self-thinning were described. Its applications in self-thinning of Populus tremula natural forest Cunninghamia lanceolata plantation were illustrated. The results of forest self-thinning examples show the BP-MSM mixed algorithms were satisfactory in simulating forest self-thinning, and its precision was higher, which develops the method and theory of artificial neural network, and enriches the simulating method of forest self-thinning.
Algorithms↗
[Mechanism and universality of Yoda's -3/2 law of self-thinning in plant population].
According to plant modular theory, the Yoda's-3/2 law of self-thinning was theoretically rederived in this paper. With the parameters in the expression of Yoda's-3/2 law being given biological meanings, this article offered universal and rational explanations for relevant data in literatures that could not be explained before. Based on the authors' hypothesis, the experiments on the self-thinning process of spring wheat (Triticum aestivum L.) were conducted. Individual morphological and population quantitative indexes were examined at regular intervals. The results showed that the self-thinning process of spring wheat conformed to Yoda's-3/2 law of self-thinning. At the same time, the universality of Yoda's-3/2 law of self-thinning was explained theoretically by analyzing individual morphological data.
Elasticity↗
A Tridimensional Self-Thinning Model for Multilayered Intertidal Mussels.
Intertidal mussels usually form complex multilayered matrices with density-dependent effects on survival and growth, and self-thinning scaling between biomass (B) and density (N) is expected. This article develops a tridimensional model of space-driven self-thinning that in addition to B-N explicitly includes the degree of packing of the mussels, measured as the number of layers (L). The structure of our model (B-N-L) encompasses previous bidimensional models (B-N) of self-thinning as special cases and enables comparisons between mono- and multilayered populations. We contrast the predictions of the bi- and tridimensional models using data obtained from Perumytilus purpuratus mussel beds on the rocky shores of central Chile monitored during a 28-mo period. The tridimensional model suggests that density dependence is much more frequent than hitherto indicated by bidimensional models. We propose that our space-driven tridimensional model may be applied not only to mussels but also to other species where spatial overlapping configurations occur.
food driven↗
An ecological framework linking scales across space and time based on self-thinning.
Scaling up from measurements made at small spatial and short temporal scales is a central challenge in the ecological and related sciences, where predictions at larger scales and over long time periods are required. It involves two quite distinct aspects: a formulation of a theoretical framework for calculating space-time averages, and an acquisition of data to support that framework. In this paper, we address the theoretical part of the question, and although our primary motivation was an understanding of carbon accounting our formulation is more general. To that end, we adopt a dynamical systems approach, and incorporate a new dynamical formulation of self-thinning. We show how to calculate rates of change for total (and average) plant dry mass, volume, and carbon, in terms of the properties of the individual plants. The results emphasize how local scale statistics (such as, variation in the size of individuals) lead to nonlinear variation at larger scales. Further, we describe how regular and stochastic disturbance can be readily incorporated into this framework. It is shown that stochastic disturbance at patch-scales, results in (to first approximation) regular disturbance at ecosystem scales, and hence can be formulated as such. We conclude that a dynamical formulation of self-thinning can be used as a generic framework for scaling ecological processes in space and time.
Ecosystem↗
A model of self-thinning through local competition.
Explanations of self-thinning in plant populations have focused on plant shape and packing. A dynamic model based on the structure of local interactions successfully reproduces the pattern and can be approximated to identify key parameters and relationships. The approach generates testable new explanations for differences between species and populations, unifies self-thinning with other patterns in plant population dynamics, and indicates why organisms other than plants can follow the law.
Journal Article↗
Stem sapwood permeability in relation to crown dominance and site quality in self-thinning fire-origin lodgepole pine stands.
Stem sapwood hydraulic permeability, tree leaf area, sapwood basal area, earlywood to latewood ratio of annual rings, radial variation in hydraulic permeability and stem hydraulic capacity were examined in dominant (D), codominant (CD) and suppressed (SP) lodgepole pine (Pinus contorta Dougl. ex Loud.) trees growing on medium and poor sites. Hydraulic permeability on a sapwood area basis (ks) was lower in suppressed trees (0.71 x 10(-12) m2) compared to dominants (1.97 x 10(-12) m2) and codominants (1.79 x 10(-12) m2), and higher on medium than on poor sites. The leaf/sapwood area ratio (S) varied with crown dominance position (D > CD > SP) but not by site type. Leaf specific conductivity (kL) did not vary between crown classes or site types. The relationship between leaf area and stem hydraulic supply capacity (Q*) was strong, but differed among crown classes. Dominant trees and trees from the medium sites had a greater proportion of earlywood in outer rings of sapwood than suppressed trees. Sapwood permeability declined from the cambium to the sapwood-heartwood boundary in all samples, but the decline was more gradual in dominant trees compared to codominant and suppressed trees; differences in the radial variation in sapwood permeability may be related to differences in S. Sapwood permeability is positively related to crown dominance, whereas subdominant (CD and SP) trees have greater Q* in relation to leaf area, leading us to propose that this may give subdominant trees a survival advantage, slowing self-thinning.
Fires↗
Genetic structure of age classes in Camellia japonica (Theaceae).
Camellia japonica L. (Theaceae), an insect- and bird-pollinated, broad-leaved evergreen tree, is widely distributed in Japan and the southern Korean peninsula. The species has a relatively even age distribution within populations, which may influence the spatial genetic structure of different age classes relative to species with typical L-shaped age distributions. To determine whether the internal spatial genetic structure found in seedlings and young individuals carries over into adults, we used allozyme loci, F-statistics, spatial autocorrelation statistics (Moran's I), and coancestry measures to examine changes in genetic structure among seven age classes in a population (60-m x 100-m area) in southern Korea. In seedlings, weak but significant positive values of Moran's I-statistics and coancestry measures were found for distances less than 14 m, which is consistent with a mechanism of limited seed dispersal combined with overlapping seed shadows. This spatial structure, however, dissipates in older age classes, and in adults genetic variation has an essentially random spatial distribution. Morisita's index of dispersion of individuals in each age class showed that seedlings and juveniles are more highly clustered than are older individuals. These results suggest that self-thinning changes the spatial relationships of individuals, and thus genotypes. A multilocus estimate of FST (0.008) shows a small but statistically significant difference in allele frequencies among age classes. In summary, intrapopulation genetic structure within and among age classes of C. japonica was significant but weak. Despite presumably limited seed dispersal, weak spatial genetic structure in juveniles suggests overlapping seed shadows followed by self-thinning during recruitment. The present study also demonstrates that studies of spatial genetic structure focusing on limited numbers of generations may not be sufficient to reveal the entire picture of genetic structure in populations with overlapping generations.
Electrophoresis↗
Biological power laws and Darwin's principle.
Assuming that the repertoire of responses by living systems to perturbation gives a measure of their Darwinian fitness in a rapidly fluctuating environment, those that fulfill allometries (power laws) are described by means of catastrophes, whose variables and parameters are smooth functions of biological attributes. Using empirical allometries from a given system as input, a method is proposed to construct its associated catastrophe, allowing specific predictions on its susceptibility to perturbation and related properties, based on general results from catastrophe theory. The method is discussed within the macroecological context, and an example is provided by applying it to ecological systems that satisfy the self-thinning rule.
Animals↗
[Influence of biotic and abiotic factors on the morphology and reproduction of Suaeda maritima on a salt marsh].
The aim of this study was to estimate the influence of biotic and abiotic factors on Suaeda maritima reproduction on a salt marsh. Individuals of Suaeda maritima were submitted in natural conditions to four series of densities (100, 1,000, 4,000 and 8,000 plants/m2). When density increases, individuals tend to be less or non-branched, while individual biomass decreases. Consequently, individual seed production decreases as density increases. Despite morphological modifications, Suaeda maritima present density-dependent mortality. For a unit area, total biomass and seed production are higher at intermediate density (1,000 plants/m2). Environmental factors could interfere with self-thinning. They seem to limit the effect of competition on mortality and to have an influence on individual and total seed production. This experiment stressed the importance of a biotic factor such as intra-specific competition, which occurs at the same time as abiotic factors, in Suaeda maritima dynamics in the field.
Biomass↗
Differences in genetic structure between two Japanese beech (Fagus crenata Blume) stands.
To examine the effects of forest cutting on within-population genetic structure, the genetic structure and variability of two Japanese beech (Fagus crenata Blume) stands with contrasting histories in relation to cutting were investigated. Six hundred and sixty beech trees, covering two hectares in total, were mapped and genetically analysed using nine isozyme loci encoding eight enzyme systems. The proportion of polymorphic loci, the average number of alleles per locus, the effective number of alleles per locus, the expected heterozygosity and the observed heterozygosity were 78, 3.3, 1.31, 0.200 and 0.189, respectively, in a secondary stand (designated AK) cut during the 1920s. Corresponding figures were 78, 3.3, 1.33, 0.203 and 0.193, respectively, in a primary stand designated KU. The inbreeding coefficient and the grand mean of the number of alleles in common (NAC) were 0.055 and 1.684 in AK, and 0. 042 and 1.649 in KU, respectively. The genetic variability was slightly but significantly lower in AK. The genetic structure of the two stands was strikingly different. The proportions of positively significant Moran's I and SND values found in the shortest distance class were 0.86 and 0.38 for AK, and 0.14 and 0.29 for KU, respectively. Furthermore, significant linkage disequilibrium was observed in AK, but none at all in KU. To examine which, if any, differences in the genetic structure would be likely to influence succeeding generations, we simulated a self-thinning process. The simulation suggested that reduced genetic variability and linkage disequilibrium would have significant influence in the AK stand for several generations.
Alleles↗
Dependence of some stand characteristics on stand density.
The development of stand basal area at the height of the lowest living branch was studied in four Norway spruce (Picea abies L. Karst.) plantations subjected to various levels of thinning. Crown limit basal area (defined as the sum of the cross-sectional areas of stems estimated at the base of the living crown per hectare) increased after each thinning until it matched that of unthinned plots. In unthinned plots, the crown limit basal area remained constant during the 26-year period of study. The dependence of the logarithm of stem number on the logarithm of the mean stem diameter at breast height was curved and dependent on the degree of thinning. The dependence of the logarithm of stem number on the logarithm of the mean stem diameter at crown height was linear and slightly dependent on the degree of thinning. This dependence can be used as the self-thinning rule.
Journal Article↗
Size symmetry of competition alters biomass-density relationships.
As crowded populations of plants develop, the growth of some plants is accompanied by the death of others, a process called density-dependent mortality or 'self-thinning'. During the course of density-dependent mortality, the relationship between total population biomass (B) and surviving plant density (N) is allometric: B = aN(b). Essentially, increasing population biomass can be achieved only through decreasing population density. Variation in the allometric coefficient a among species has been recognized for many years and is important for management, assessment of productivity and carbon budgets, but the causes of this variation have not been elucidated. Individual-based models predict that size-dependent competition causes variation in the allometric coefficient. Using transgenic Arabidopsis with decreased plasticity, we provide experimental evidence that morphological plasticity of wild-type populations decreases the size asymmetry of competition for light and thereby decreases density-dependent mortality. This decrease in density-dependent mortality results in more biomass at a given density under size-symmetric compared with size-asymmetric competition.
Arabidopsis↗
Size distribution and genetic structure in relation to clonal growth within a population of Magnolia tomentosa Thunb. (Magnoliaceae).
To establish a baseline for conservation of a threatened clonal tree, Magnolia tomentosa, we investigated size distribution and genetic structure within a population, using six microsatellite markers. Within the study site, 1044 living ramets (stems) were distinguished into 175 genets (individuals). The mean number of ramets per genet was 5.97, and 76% of all genets had multiple ramets. Genets, which apparently produced new ramets through sprouting and layering, were generally composed of several large ramets and many small ramets. Spatial autocorrelation analysis of microsatellite alleles revealed positive autocorrelation over short distances for both ramets and genets. The Moran's I-value of ramets in the shortest distance class was 3.8 times larger than that of genets, reflecting the effect of clonal growth. To analyse the size-class differences in genetic structure, the 175 genets were separated into two size classes, small and large. The correlogram for the small genets exhibited positive spatial autocorrelation in the shortest distance class, but this was not the case for the correlogram for the large genets, indicating that genetic structure is weakened or lost through self-thinning as the genets grow. The FIS value over all loci for the small genets was positive and deviated significantly from zero, while the corresponding value for the large genets was close to zero. The excess homozygotes in the small genets may be the result of genetic substructuring and/or inbreeding, and the reduction in homozygote frequency from the small to large genets may be because of loss of genetic structure and/or inbreeding depression.
Alleles↗
[Age-structure dynamics and genetic consequences of Hippophea rhamnoides L. subsp sinensis clone population in Mu Su sandland].
Based on the measurement of all individuals of population at different successional stage, the investigation on edge dispersal effect and the following excavation of clones, the dynamics of age structure and genetic consequences of Hippophea rhamnoides L. subsp sinensis clone population in Mu Su sandland were examined. The results showed that the age structure of the clone population was characterized by a transformation from an increasing type in the early period starting from the initial colonization through a stable type to a declining type. The clone population could maintain or recover its stability by edge dispersal and gap regeneration with clonal growth. As the population self-thinned, the composition of clone population changed from more clones with less ramets to less clones with more ramets and the genetic diversity of clone population decreased.
Age Factors↗
[Skewness and inequality of height distribution of young Pinus sylvestris var. mongolica stands introduced on sandy soil with lower limited precipitation for tree survival and normal growth].
Based on the investigation of a transect (20 m wide and 80 m long) along a gradient (bottom, middle, and top) of a dune, whose height was about 5-10 m, the population dynamics in young Pinus sylvestis var. mongolica stands was studied. The results showed that both skewness and height inequality declined before the self-thinning process occurred. Age, initial growth status, density of the population, and neighborhood competition were the main factors affected height inequality. The location at sand dune was also an important factor, and its effect was more obvious than that of density.
Chemical Precipitation↗
[Parital microflora of human intestine].
The modified method of the microbiological study of parietal mucin has been developed. The proposed method makes it possible to evaluate the parietal microflora of the intestine. The advantages of using physiological saline and Hanks' solution as medium ensuring the storage and self-thinning of mucin have been proved. The optimum time of making the microbiological study of intestinal mucin has also been determined.
Bacteria↗
[Community characteristics of Pinus armandi forest on Qinling Mountains].
The community characteristics of Pinus armandi forest distributed on the mid-west zone of Qinling Mountains' south slope were investigated. The results showed that there were 166 seed plants belonging to 51 families, 111 generas. Among them, 65 genera, 66.7% of the total, belonged to temperate biome. There was a closely relationship between Pinus armandi forest and the temperate biome. As regards to the physiognomy of the community, phanerophyte made up 75.9% of the total, dominating the community. In the community, 96 species with middle-sized leaves made up 57.8%, and there were 139 single leaf species, accounted for 83.7% of the total. There was a complicated vertical structure in the community, which could be divided into three layers:arbor layer, shrub layer and herb layer. In addition, there were also a lot of inter-stratum plants in the community. It is also found that the lack of seedlings, saplings and small trees was due to both the self-thinning caused by intra-specific competition and the alien-thinning by inter-specific competition for the light resource in the stand. The population of P. armandi was characterized with the patch size about 100 m2. The dynamics of the community showed that the community was stable and in a process of development.
Ecosystem↗