scholarly journals A general quantitative theory of forest structure and dynamics

2009 ◽  
Vol 106 (17) ◽  
pp. 7040-7045 ◽  
Author(s):  
Geoffrey B. West ◽  
Brian J. Enquist ◽  
James H. Brown
Keyword(s):  
Size Structure ◽  
Dynamic Properties ◽  
Scale Up ◽  
Spatial Arrangement ◽  
Emergent Properties ◽  
Frequency Distributions ◽  
Individual Level ◽  
Quantitative Theory ◽  
Structure And Dynamics ◽  
Individual Trees

We present the first part of a quantitative theory for the structure and dynamics of forests at demographic and resource steady state. The theory uses allometric scaling relations, based on metabolism and biomechanics, to quantify how trees use resources, fill space, and grow. These individual-level traits and properties scale up to predict emergent properties of forest stands, including size–frequency distributions, spacing relations, resource flux rates, and canopy configurations. Two insights emerge from this analysis: (i) The size structure and spatial arrangement of trees in the entire forest are emergent manifestations of the way that functionally invariant xylem elements are bundled together to conduct water and nutrients up from the trunks, through the branches, to the leaves of individual trees. (ii) Geometric and dynamic properties of trees in a forest and branches in trees scale identically, so that the entire forest can be described mathematically and behaves structurally and functionally like a scaled version of the branching networks in the largest tree. This quantitative framework uses a small number of parameters to predict numerous structural and dynamical properties of idealized forests.

scholarly journals Extensions and evaluations of a general quantitative theory of forest structure and dynamics

2009 ◽  
Vol 106 (17) ◽  
pp. 7046-7051 ◽  
Author(s):  
Brian J. Enquist ◽  
Geoffrey B. West ◽  
James H. Brown
Keyword(s):  
Allometric Scaling ◽  
Scale Up ◽  
Resource Limitation ◽  
Scaling Relations ◽  
Emergent Properties ◽  
Frequency Distributions ◽  
Individual Level ◽  
Quantitative Theory ◽  
Structure And Dynamics ◽  
Wide Range

Here, we present the second part of a quantitative theory for the structure and dynamics of forests under demographic and resource steady state. The theory is based on individual-level allometric scaling relations for how trees use resources, fill space, and grow. These scale up to determine emergent properties of diverse forests, including size–frequency distributions, spacing relations, canopy configurations, mortality rates, population dynamics, successional dynamics, and resource flux rates. The theory uniquely makes quantitative predictions for both stand-level scaling exponents and normalizations. We evaluate these predictions by compiling and analyzing macroecological datasets from several tropical forests. The close match between theoretical predictions and data suggests that forests are organized by a set of very general scaling rules. Our mechanistic theory is based on allometric scaling relations, is complementary to “demographic theory,” but is fundamentally different in approach. It provides a quantitative baseline for understanding deviations from predictions due to other factors, including disturbance, variation in branching architecture, asymmetric competition, resource limitation, and other sources of mortality, which are not included in the deliberately simplified theory. The theory should apply to a wide range of forests despite large differences in abiotic environment, species diversity, and taxonomic and functional composition.

scholarly journals ROLE OF NEUTRAL EVOLUTION IN WORD TURNOVER DURING CENTURIES OF ENGLISH WORD POPULARITY

2017 ◽  
Vol 20 (06n07) ◽  
pp. 1750012 ◽  
Author(s):  
DAMIAN RUCK ◽  
R. ALEXANDER BENTLEY ◽  
ALBERTO ACERBI ◽  
PHILIP GARNETT ◽  
DANIEL J. HRUSCHKA
Keyword(s):  
English Language ◽  
Dynamic Properties ◽  
English Word ◽  
Neutral Evolution ◽  
Emergent Properties ◽  
Small Subset ◽  
Neutral Model ◽  
Two Stage ◽  
Frequency Distributions ◽  
Neutral Models

Here, we test Neutral models against the evolution of English word frequency and vocabulary at the corpus scale, as recorded in annual word frequencies from three centuries of English language books. Against these data, we test both static and dynamic predictions of two neutral models, including the relation between corpus size and vocabulary size, frequency distributions, and turnover within those frequency distributions. Although a commonly used Neutral model fails to replicate all these emergent properties at once, we find that modified two-stage Neutral model does replicate the static and dynamic properties of the corpus data. This two-stage model is meant to represent a relatively small corpus of English books, analogous to a ‘canon’, sampled by an exponentially increasing corpus of books among the wider population of authors. More broadly, this model — a smaller neutral model within a larger neutral model — could represent more broadly those situations where mass attention is focused on a small subset of the cultural variants.

scholarly journals Estimating individual level plant traits at scale

2019 ◽  
Author(s):  
Sergio Marconi ◽  
Sarah J. Graves ◽  
Ben. G. Weinstein ◽  
Stephanie Bohlman ◽  
Ethan P. White
Keyword(s):  
Remote Sensing ◽  
Test Data ◽  
Large Scale ◽  
Plant Traits ◽  
Scale Up ◽  
Functional Ecology ◽  
Individual Level ◽  
Structural Traits ◽  
Individual Trees ◽  
Better Than

AbstractFunctional ecology has increasingly focused on describing ecological communities based on their traits (measurable features affecting individuals fitness and performance). Analyzing trait distributions within and among forests could significantly improve understanding of community composition and ecosystem function. Historically, data on trait distributions are generated by (1) collecting a small number of leaves from a small number of trees, which suffers from limited sampling but produces information at the fundamental ecological unit (the individual); or (2) using remote sensing images to infer traits, producing information continuously across large regions, but as plots (containing multiple trees of different species) or pixels, not individuals. Remote sensing methods that identify individual trees and estimate their traits would provide the benefits of both approaches, producing continuous large-scale data linked to biological individuals. We used data from the National Ecological Observatory Network (NEON) to develop a method to scale up functional traits from 160 trees to the millions of trees within the spatial extent of two NEON sites. The pipeline consists of three stages: 1) image segmentation, to identify individual trees and estimate structural traits; 2) ensemble of models to infer leaf mass area (LMA), nitrogen, carbon, and phosphorus content using hyperspectral signatures, and DBH from allometry; and 3) predictions for segmented crowns for the full remote sensing footprint at the NEON sites.The R2 values on held out test data ranged from 0.41 to 0.75 on held out test data. The ensemble approach performed better than single partial least squares models. Carbon performed poorly compared to other traits (R2 of 0.41). The crown segmentation step contributed the most uncertainty in the pipeline, due to over-segmentation. The pipeline produced good estimates of DBH (R2 of 0.62 on held out data). Trait predictions for crowns performed significantly better than comparable predictions on pixels, resulting in improvement of R2 on test data of between to 0.26. We used the pipeline to produce individual level trait data for ∼5 million individual crowns, covering a total extent of ∼360 km2. This large dataset allows testing ecological questions on landscape scales, revealing that foliar traits are correlated with structural traits and environmental conditions.

Nucleosome dynamics

2006 ◽  
Vol 73 ◽  
pp. 109-119 ◽  
Author(s):  
Chris Stockdale ◽  
Michael Bruno ◽  
Helder Ferreira ◽  
Elisa Garcia-Wilson ◽  
Nicola Wiechens ◽  
...  
Keyword(s):  
High Resolution ◽  
Chromatin Structure ◽  
Current Knowledge ◽  
Dynamic Properties ◽  
Structure And Dynamics ◽  
Nucleosome Dynamics ◽  
Sharp Focus ◽  
Recent Advances ◽  
Insight Into ◽  
Chromatin Structure And Dynamics

In the 30 years since the discovery of the nucleosome, our picture of it has come into sharp focus. The recent high-resolution structures have provided a wealth of insight into the function of the nucleosome, but they are inherently static. Our current knowledge of how nucleosomes can be reconfigured dynamically is at a much earlier stage. Here, recent advances in the understanding of chromatin structure and dynamics are highlighted. The ways in which different modes of nucleosome reconfiguration are likely to influence each other are discussed, and some of the factors likely to regulate the dynamic properties of nucleosomes are considered.

scholarly journals Linking population size structure, heat stress and bleaching responses in a subtropical endemic coral

Coral Reefs ◽  
2021 ◽  
Author(s):  
Liam Lachs ◽  
Brigitte Sommer ◽  
James Cant ◽  
Jessica M. Hodge ◽  
Hamish A. Malcolm ◽  
...  
Keyword(s):  
Heat Stress ◽  
Size Structure ◽  
Temporal Trends ◽  
Early Recovery ◽  
Size Frequency Distribution ◽  
Frequency Distributions ◽  
Community Organisation ◽  
Size Frequency ◽  
Eastern Australia

AbstractAnthropocene coral reefs are faced with increasingly severe marine heatwaves and mass coral bleaching mortality events. The ensuing demographic changes to coral assemblages can have long-term impacts on reef community organisation. Thus, understanding the dynamics of subtropical scleractinian coral populations is essential to predict their recovery or extinction post-disturbance. Here we present a 10-yr demographic assessment of a subtropical endemic coral, Pocillopora aliciae (Schmidt-Roach et al. in Zootaxa 3626:576–582, 2013) from the Solitary Islands Marine Park, eastern Australia, paired with long-term temperature records. These coral populations are regularly affected by storms, undergo seasonal thermal variability, and are increasingly impacted by severe marine heatwaves. We examined the demographic processes governing the persistence of these populations using inference from size-frequency distributions based on log-transformed planar area measurements of 7196 coral colonies. Specifically, the size-frequency distribution mean, coefficient of variation, skewness, kurtosis, and coral density were applied to describe population dynamics. Generalised Linear Mixed Effects Models were used to determine temporal trends and test demographic responses to heat stress. Temporal variation in size-frequency distributions revealed various population processes, from recruitment pulses and cohort growth, to bleaching impacts and temperature dependencies. Sporadic recruitment pulses likely support population persistence, illustrated in 2010 by strong positively skewed size-frequency distributions and the highest density of juvenile corals measured during the study. Increasing mean colony size over the following 6 yr indicates further cohort growth of these recruits. Severe heat stress in 2016 resulted in mass bleaching mortality and a 51% decline in coral density. Moderate heat stress in the following years was associated with suppressed P. aliciae recruitment and a lack of early recovery, marked by an exponential decrease of juvenile density (i.e. recruitment) with increasing heat stress. Here, population reliance on sporadic recruitment and susceptibility to heat stress underpin the vulnerability of subtropical coral assemblages to climate change.

scholarly journals Examining social determinants by locale to inform community linkages

2020 ◽  
Vol 30 (Supplement_5) ◽  
Author(s):  
J Davis
Keyword(s):  
Social Determinants ◽  
Low Income ◽  
Negative Impact ◽  
Rank Order ◽  
Disabled Persons ◽  
Behavioral Risk ◽  
Exploratory Research ◽  
Frequency Distributions ◽  
Individual Level ◽  
Negative Impacts

Abstract Achieving a long-lasting impact on health outcomes requires focus not just on patient care, but also on community approaches aimed at improving population health through addressing gaps in Social Determinants of Health (SDOH). SDOH have been found to disproportionately affect those in low-income brackets and the disabled to varying degrees based on locale. The purpose of this exploratory research was to determine 1) which SDOH have the greatest negative impact on disabled and elderly populations within four targeted states (Iowa, Ohio, Minnesota, Wisconsin) and 2) if there is a difference in negative SDOH impact between metro and non-metro locales. Individual-level data were obtained from disabled persons aged 65 years or older who responded to the Centers for Disease Control and Prevention's 2017 Behavioral Risk Factor Surveillance System (BRFSS) survey. Utilizing these data, frequency distributions were obtained using SPSS. Rank order variation in SDOH was observed among four Midwestern states and between metro vs. non-metro geographic regions. Frequency distributions assisted in identifying the greatest negative impacting SDOH on elderly disabled populations. An examination of the rank order tables allowed the investigator to accurately assess the rank of negative impacts. There were variabilities in responses to questions with moving two or more times within 12 months having the lowest negative impact. When regrouped based upon SDOH negative impacts, were you able to pay your bills was the most frequent SDOH across all states. Feeling unsafe or extremely unsafe in your neighborhood was the highest negatively impacted SDOH within states. Cited determinants in three categories were highest in Ohio. Ohio also had the highest proportion of negatively impacted SDOH across all states. No money for balanced meals was a close second SDOH across states. Key messages Social Determinants Impacting Elderly Disabled. Impact of Social Determinants by Geography.

scholarly journals Structure and dynamics of a Cariniana estrellensis (Lecythidaceae) population in a fragment of Atlantic Forest in Minas Gerais, Brazil

Rodriguésia ◽  
2012 ◽  
Vol 63 (2) ◽  
pp. 257-267 ◽  
Author(s):  
Yule Roberta Ferreira Nunes ◽  
Miguel Petrere Jr.
Keyword(s):  
Population Structure ◽  
Seed Production ◽  
Size Structure ◽  
Canopy Cover ◽  
High Rate ◽  
Structure And Dynamics ◽  
Seedling Bank ◽  
Phase Size ◽  
Population Structure And Dynamics ◽  
Establishment Phase

We aimed to describe population structure and dynamics of Cariniana estrellensis (Raddi) Kuntze to test the hypothesis that this species survives in the forest by forming a seedling bank. We evaluated seed germination, spatial distribution, and recruitment, growth and mortality rates of young individuals. To characterize population structure a 1.2-ha plot was defined, where reproductive adults were mapped; also 100 6 m² sub-plots were established to characterize structure and monitor dynamics of young individuals. We estimated seed production using seed collectors and determined the percentage of canopy cover by hemispherical photographs. Seed rain and saplings showed clustered distribution indicating habitat-patch formation. Sapling mortality occurred mainly during the initial establishment phase. Size structure was characterized by many saplings (X = 9,763 individuals ha-1) and few adults (X = 5 individuals ha-1), associated with a high rate of seed production (X = 60,800 seeds ha-1), low growth rates (X = 2.37 cm ano-1) and mortality (15.66%) of established saplings, showing that species invest in seedling bank formation as a reproductive strategy.

scholarly journals Opposite outcomes of coinfection at individual and population scales

2018 ◽  
Vol 115 (29) ◽  
pp. 7545-7550 ◽  
Author(s):  
Erin E. Gorsich ◽  
Rampal S. Etienne ◽  
Jan Medlock ◽  
Brianna R. Beechler ◽  
Johannie M. Spaan ◽  
...  
Keyword(s):  
Reproduction Number ◽  
Negative Impact ◽  
Scale Up ◽  
Population Level ◽  
Clear Understanding ◽  
African Buffalo ◽  
Global Public Health ◽  
Individual Level ◽  
Secondary Infections ◽  
The Individual

Coinfecting parasites and pathogens remain a leading challenge for global public health due to their consequences for individual-level infection risk and disease progression. However, a clear understanding of the population-level consequences of coinfection is lacking. Here, we constructed a model that includes three individual-level effects of coinfection: mortality, fecundity, and transmission. We used the model to investigate how these individual-level consequences of coinfection scale up to produce population-level infection patterns. To parameterize this model, we conducted a 4-y cohort study in African buffalo to estimate the individual-level effects of coinfection with two bacterial pathogens, bovine tuberculosis (bTB) and brucellosis, across a range of demographic and environmental contexts. At the individual level, our empirical results identified bTB as a risk factor for acquiring brucellosis, but we found no association between brucellosis and the risk of acquiring bTB. Both infections were associated with reductions in survival and neither infection was associated with reductions in fecundity. The model reproduced coinfection patterns in the data and predicted opposite impacts of coinfection at individual and population scales: Whereas bTB facilitated brucellosis infection at the individual level, our model predicted the presence of brucellosis to have a strong negative impact on bTB at the population level. In modeled populations where brucellosis was present, the endemic prevalence and basic reproduction number (R0) of bTB were lower than in populations without brucellosis. Therefore, these results provide a data-driven example of competition between coinfecting pathogens that occurs when one pathogen facilitates secondary infections at the individual level.

Non-random spatial arrangement of clone sizes in chimaeric retinal pigment epithelium

Development ◽  
1986 ◽  
Vol 91 (1) ◽  
pp. 197-208
Author(s):  
Günter H. Schmidt ◽  
Maureen M. Wilkinson ◽  
Bruce A. J. Ponder
Keyword(s):  
Retinal Pigment Epithelium ◽  
Patch Size ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Spatial Arrangement ◽  
Tissue Growth ◽  
Geometric Means ◽  
Frequency Distributions ◽  
Size Frequency ◽  
Wide Range

Clonal analysis of whole-mount preparations of entire retinal pigment epithelium (RPE), using SWR ↔ C57BL/6JLac and DDK ↔ C3H/Bi mouse aggregation chimaeras in which one of the two parental components predominated, revealed a markedly non-random spatial arrangement of patch (clone) sizes. Single-cell and small patches predominated in an area around the optic nerve head while large patches occurred most frequently near the periphery. Mechanisms are discussed which may explain these results. Patch size frequency distributions were concave and skewed. Singletons were the most frequent size class, but a wide range of sizes and a smaller number of much larger patches were also always found. The results preclude the use of statistical methods previously employed to calculate clone sizes from the geometric means of observed patch sizes. Instead, the median and interquartile range may provide the best summary of the observed patch size frequency distributions. Our findings support a stochastic model of tissue growth.

Biomass models for three species with different growth forms and geographic distribution in the Brazilian Atlantic forest

2021 ◽  
pp. 1-13
Author(s):  
Heitor Felippe Uller ◽  
Laio Zimermann Oliveira ◽  
Aline Renata Klitzke ◽  
Joberto Veloso de Freitas ◽  
Alexander Christian Vibrans
Keyword(s):  
Atlantic Forest ◽  
Geographic Distribution ◽  
Morphological Features ◽  
Brazilian Atlantic Forest ◽  
Growth Forms ◽  
Individual Level ◽  
Generic Models ◽  
The Individual ◽  
Species Specific ◽  
Individual Trees

Allometric models embedding independent variables such as diameter at breast height (d) and total height (h) are useful tools to predict the biomass of individual trees. Models for tropical forests are often constructed based on datasets composed of species with different morphological features and architectural models. It is reasonable to expect, however, that species-specific models may reduce uncertainties in biomass predictions, especially for palms, tree ferns, and trees with peculiar morphological features, such as stilt roots and hollow trunks. In this sense, three species with wide geographical distribution in the Brazilian Atlantic Forest were sampled, namely Euterpe edulis Mart., Cyathea delgadii Sternb., and Cecropia glaziovii Snethl., with the aim to (i) quantify their aboveground biomass (AGB), (ii) evaluate the AGB distribution in different plant compartments, (iii) fit species-specific models for predicting AGB at the individual level, and (iv) assess the performance of specific and generic models available in the literature to predict the AGB of individuals of these species. The compartment stem represented, on average, ∼74% of the total AGB of E. edulis individuals; in turn, the caudex compartment of C. delgadii represented, on average, ∼87% of the total AGB, while the trunk compartment of C. glaziovii represented, on average, ∼74%. Among the fitted models, the power model [Formula: see text] showed the best performance for E. edulis and C. delgadii. In turn, the asymptotic logistic model [Formula: see text], where dc is the diameter above the upper stilt root, presented the best performance for C. glaziovii. The variable h appeared as the most important predictor of AGB of E. edulis and C. delgadii; in contrast, the stem and caudex mean basic specific gravities were not suitable predictors. The fitted species-specific models outperformed the specific and generic models selected from the literature. They may, therefore, contribute to the reduction of uncertainties in AGB estimates. In addition, the results support evidence that specific models may be necessary for species with different growth forms and (or) peculiar morphological features, especially those with great abundance and wide geographic distribution.

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