Community organization in streams: the importance of species interactions, physical factors, and chance

Oecologia ◽  
1992 ◽  
Vol 91 (2) ◽  
pp. 220-228 ◽  
Author(s):  
David D. Hart
Keyword(s):  
Species Interactions ◽  
Community Organization ◽  
Physical Factors

Community organization: effects of landscape fragmentation

1988 ◽  
Vol 66 (12) ◽  
pp. 2687-2690 ◽  
Author(s):  
Robert L. Burgess
Keyword(s):  
Community Organization ◽  
Human Impacts ◽  
Landscape Management ◽  
Terrestrial Ecosystems ◽  
Landscape Fragmentation ◽  
Physical Factors ◽  
Natural Area ◽  
Ecosystem Integrity ◽  
Theory Of Island Biogeography ◽  
Future Work

All over the world, natural terrestrial ecosystems have been subjected to a wide variety of human impacts. Most noticeable are activities and processes associated with agriculture, forestry, mining, and urban development. Results range from virtual obliterations of natural communities through varying degrees of fragmentation to a series of preserves and natural areas. Studies of many taxa, both plant and animal, indicate numerous effects associated with the loss of contiguity, reduction in total area, relationship to physical factors, and increasing separation of remaining fragments. The theory of island biogeography has been tested in many kinds of landscapes and for many groups of organisms. The great differences between true islands and terrestrial "habitat islands" lead to inconclusive results in many investigations and to major questions concerning the applicability of the equilibrium model to fragmented terrestrial landscapes. This paper attempts to summarize indicative examples that have a bearing on community structure and organization and to present some ideas for future work in landscape management and its relation to species diversity, natural area preservation, and continued ecosystem integrity, viability, stability, and vitality.

Natural disturbance and gap phase dynamics in southern Appalachian spruce–fir forests

1985 ◽  
Vol 15 (1) ◽  
pp. 233-240 ◽  
Author(s):  
Peter S. White ◽  
Mark D. MacKenzie ◽  
Richard T. Busing
Keyword(s):  
Species Interactions ◽  
Community Organization ◽  
Natural Disturbance ◽  
Canopy Gaps ◽  
Old Growth ◽  
Capture Process ◽  
Canopy Density ◽  
Great Smoky Mountains ◽  
Phase Dynamics ◽  
Smoky Mountains

Spatially small canopy gaps dominated the natural disturbance regime of old-growth spruce–fir forests in the Great Smoky Mountains, North Carolina and Tennessee. New gaps ≤200 m2 in size were formed with a frequency of 0.006 to 0.009/year and the 1- to 10-year age class of these gaps covered an estimated 6 to 17% of the study area (depending on calculation method). Sixty canopy gaps sampled on a 7-ha intensive study site ranged in size from 15 to 150 m2. Although tree replacement patterns in these gaps were unpredictable from gap size and age, the gap event was important in species interactions. The three canopy dominants, Abiesfraseri (Pursh) Poir., Picearubens Sarg., and Betulalutea Michx.f., had unique suites of life history traits. Abies reached high understory densities, but had the highest canopy turnover rate of the three species. Betula was scarce in the understory, but had a crown expansion rate in gaps eight times that of the two conifers. Picea was the longest lived species and appeared to have the best survivorship. Tree replacement models based on advanced regeneration led to the prediction that Abies canopy density would increase and Betula canopy density would decrease, while models based on gap inventories led to opposite conclusions. Data from direct observation of the gap capture process supported the hypothesis that this old-growth stand was near compositional equilibrium and underscored the importance of disturbance effects in community organization.

scholarly journals Facilitative and competitive interaction components among New England salt marsh plants

2017 ◽  
Author(s):  
John F Bruno ◽  
Tatyana A Rand ◽  
Nancy C Emery ◽  
Mark D Bertness
Keyword(s):  
Salt Marsh ◽  
New England ◽  
Species Interactions ◽  
Community Organization ◽  
Interspecific Interactions ◽  
Later Life ◽  
Positive Interactions ◽  
Life Stages ◽  
England Salt Marsh ◽  
Natural Communities

Intra- and interspecific interactions can be broken down into facilitative and competitive components. The net interaction between two organisms is simply the sum of these counteracting elements. Disentangling the positive and negative components of species interactions is a critical step in advancing our understanding of how the interaction between organisms shift along physical and biotic gradients, and whether component interactions are unique or redundant across species in natural communities. We performed a manipulative field experiment to quantify the positive and negative components of the interactions between a perennial forb, Aster tenuifolius, and three dominant, matrix-forming grasses and rushes in a New England salt marsh. Specifically, we asked whether positive and negative interaction components: (1) are unique or redundant across three matrix-forming grass and rush species (Juncus gerardi, Distichlis spicata, and Spartina patens), and (2) change across Aster life stages (seedling, juvenile, and adult). For adult forbs, the strength of the facilitative component of the matrix-forb interaction was stronger than the competitive component for two of the three matrix species, leading to net positive interactions. There was no statistically significant variation among matrix species in their net or component effects, however, the competitive effect of J. gerardi was negligible, especially compared to that of D. spicata. We found little difference in the effects of J. gerardi on Aster at later life-history stages; interaction component strengths did not differ between juveniles and adults. However, mortality of seedlings in neighbor removal plots was 100%, indicating a particularly strong and critical facilitative effect of matrix species on this forb during the earliest life stages. Overall, our results indicate that matrix forming grasses and rushes have important, yet largely redundant, positive net effects on Aster performance across its life cycle. Studies that untangle various components of interactions and their contingencies are critical to both expanding our basic understanding of community organization, and predicting how natural communities and their component parts will respond to environmental change.

scholarly journals Facilitative and competitive interaction components among New England salt marsh plants

2017 ◽  
Author(s):  
John F Bruno ◽  
Tatyana A Rand ◽  
Nancy C Emery ◽  
Mark D Bertness
Keyword(s):  
Salt Marsh ◽  
New England ◽  
Species Interactions ◽  
Community Organization ◽  
Interspecific Interactions ◽  
Later Life ◽  
Positive Interactions ◽  
Life Stages ◽  
England Salt Marsh ◽  
Natural Communities

Intra- and interspecific interactions can be broken down into facilitative and competitive components. The net interaction between two organisms is simply the sum of these counteracting elements. Disentangling the positive and negative components of species interactions is a critical step in advancing our understanding of how the interaction between organisms shift along physical and biotic gradients, and whether component interactions are unique or redundant across species in natural communities. We performed a manipulative field experiment to quantify the positive and negative components of the interactions between a perennial forb, Aster tenuifolius, and three dominant, matrix-forming grasses and rushes in a New England salt marsh. Specifically, we asked whether positive and negative interaction components: (1) are unique or redundant across three matrix-forming grass and rush species (Juncus gerardi, Distichlis spicata, and Spartina patens), and (2) change across Aster life stages (seedling, juvenile, and adult). For adult forbs, the strength of the facilitative component of the matrix-forb interaction was stronger than the competitive component for two of the three matrix species, leading to net positive interactions. There was no statistically significant variation among matrix species in their net or component effects, however, the competitive effect of J. gerardi was negligible, especially compared to that of D. spicata. We found little difference in the effects of J. gerardi on Aster at later life-history stages; interaction component strengths did not differ between juveniles and adults. However, mortality of seedlings in neighbor removal plots was 100%, indicating a particularly strong and critical facilitative effect of matrix species on this forb during the earliest life stages. Overall, our results indicate that matrix forming grasses and rushes have important, yet largely redundant, positive net effects on Aster performance across its life cycle. Studies that untangle various components of interactions and their contingencies are critical to both expanding our basic understanding of community organization, and predicting how natural communities and their component parts will respond to environmental change.

Intraspecific Genetic Variation and Species Interactions Contribute to Community Evolution

2020 ◽  
Vol 51 (1) ◽  
pp. 587-612
Author(s):  
Thomas G. Whitham ◽  
Gerard J. Allan ◽  
Hillary F. Cooper ◽  
Stephen M. Shuster
Keyword(s):  
Genetic Variation ◽  
Environmental Change ◽  
Empirical Evidence ◽  
Evolutionary Theory ◽  
Species Interactions ◽  
Community Organization ◽  
Community Evolution ◽  
Multiple Levels ◽  
Selection For ◽  
Rapid Environmental Change

Evolution has been viewed as occurring primarily through selection among individuals. We present a framework based on multilevel selection for evaluating evolutionary change from individuals to communities, with supporting empirical evidence. Essential to this evaluation is the role that interspecific indirect genetic effects play in shaping community organization, in generating variation among community phenotypes, and in creating community heritability. If communities vary in phenotype, and those phenotypes are heritable and subject to selection at multiple levels, then a community view of evolution must be merged with mainstream evolutionary theory. Rapid environmental change during the Anthropocene will require a better understanding of these evolutionary processes, especially selection acting at the community level, which has the potential to eliminate whole communities while favoring others.

Demographic parameters at evolutionary equilibrium

1984 ◽  
Vol 62 (11) ◽  
pp. 2264-2271 ◽  
Author(s):  
Peter D. Taylor ◽  
George C. Williams
Keyword(s):  
Growth Rate ◽  
Mortality Rate ◽  
Life Histories ◽  
Community Organization ◽  
Geometric Constraints ◽  
Physical Factors ◽  
Total Biomass ◽  
Age Cohort ◽  
Population Sizes ◽  
The Individual

We reason that natural selection acting under conditions imposed by physical factors (e.g., geometric constraints on growth rate) and community organization (e.g., persistent finite population sizes, equal total biomass of organisms in proportionately equal size ranges) should lead to certain life history features. The initial size of resource-capturing young should be the smallest that permits growth rate to exceed mortality rate so that the age cohort will start to increase in biomass. Production of such young must be an inefficient use of biomass because of metabolism, predation of embryos, the cost of males, and other losses. Mortality rate during juvenile growth should be a power function like growth rate, but always a bit lower so that the age cohort continues to increase and ultimately to compensate for the inefficiency of reproduction. In a constant environment, the individual should stop growing at the size of greatest expected excess of future reproductive resources over size, and thereafter devote all expendable resources to reproduction. Any given size range of animals, such as 1–2 mg or 1–2 kg, should consist of both mature and immature individuals in any community and should be devoting about a third of its investable resources to reproduction and the rest to growth. We use our equations to generate sample life histories. The simple form of our equations organizes these life tables into families of similar schedules with variable generation time.

scholarly journals Facilitative and competitive interaction components among New England salt marsh plants

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e4049 ◽  
Author(s):  
John F. Bruno ◽  
Tatyana A. Rand ◽  
Nancy C. Emery ◽  
Mark D. Bertness
Keyword(s):  
Salt Marsh ◽  
New England ◽  
Species Interactions ◽  
Community Organization ◽  
Interspecific Interactions ◽  
Later Life ◽  
Positive Interactions ◽  
Life Stages ◽  
England Salt Marsh ◽  
The Matrix

Intra- and interspecific interactions can be broken down into facilitative and competitive components. The net interaction between two organisms is simply the sum of these counteracting elements. Disentangling the positive and negative components of species interactions is a critical step in advancing our understanding of how the interaction between organisms shift along physical and biotic gradients. We performed a manipulative field experiment to quantify the positive and negative components of the interactions between a perennial forb, Aster tenuifolius, and three dominant, matrix-forming grasses and rushes in a New England salt marsh. Specifically, we asked whether positive and negative interaction components: (1) are unique or redundant across three matrix-forming species (two grasses; Distichlis spicata and Spartina patens, and one rush; Juncus gerardi), and (2) change across Aster life stages (seedling, juvenile, and adult). For adult Aster the strength of the facilitative component of the matrix-forb interaction was stronger than the competitive component for two of the three matrix species, leading to net positive interactions. There was no statistically significant variation among matrix species in their net or component effects. We found little difference in the effects of J. gerardi on Aster at later life-history stages; interaction component strengths did not differ between juveniles and adults. However, mortality of seedlings in neighbor removal plots was 100%, indicating a particularly strong and critical facilitative effect of matrix species on this forb during the earliest life stages. Overall, our results indicate that matrix forming grasses and rushes have important, yet largely redundant, positive net effects on Aster performance across its life cycle. Studies that untangle various components of interactions and their contingencies are critical to both expanding our basic understanding of community organization, and predicting how natural communities and their component parts will respond to environmental change.

Community Organization Curriculum Development

1967 ◽  
Author(s):  
Arnulf M. Pins ◽  
Arnold Gurin ◽  
Wyatt C. Jones ◽  
Joan Levin ◽  
Robert Perlmam
Keyword(s):  
Curriculum Development ◽  
Community Organization
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