scholarly journals Biomass explains the intensity of facilitative – not competitive – interactions: three intraspecific tests with annuals

Web Ecology ◽  
2012 ◽  
Vol 12 (1) ◽  
pp. 49-55 ◽  
Author(s):  
C. Ariza ◽  
K. Tielbörger
Keyword(s):  
Size Dependence ◽  
Resource Competition ◽  
Theoretical Models ◽  
Plant Size ◽  
Competitive Interactions ◽  
Positive Interactions ◽  
Plant Interactions ◽  
Belowground Competition ◽  
Size Dependent ◽  
Negative Effect

Abstract. Despite efforts to discern the role of plant size in resource competition, the circumstances under which size-dependent plant-plant interactions occur are still unclear. The traditional assumption is that competition intensifies with increasing neighbour size. However, recent studies suggest that the size (biomass) dependence of competitive interactions is strongest at very low biomass levels and becomes negligible after a certain threshold neighbour biomass has been reached. We searched for the generality of such patterns for three common annual plant species in Israel. We monitored target and neighbour biomass along their entire lifecycle using an even-aged, intraspecific and intrapopulation competition screenhouse experiment under water-limited conditions. For all focal species, neighbour presence had a net negative effect on vegetative biomass at harvest. However, this was not explained by increasing neighbour biomass over time, as a consistent pattern of size-dependent facilitative, rather than competitive, interactions was observed at all life stages. We explain these observations in terms of co-occurring aboveground facilitation and dominant belowground competition for water. Since our findings are the first of their kind and contradict theoretical predictions of biomass dependence of net negative interactions, we advocate further experiments addressing size dependence in interactions among plants. In particular, theoretical models addressing size dependence of positive interactions must be developed.

scholarly journals Local Victory: Assessing Interspecific Competition in Seagrass From a Trait-Based Perspective

2021 ◽  
Vol 12 ◽  
Author(s):  
Agustín Moreira-Saporiti ◽  
Sonia Bejarano ◽  
Inés G. Viana ◽  
Elizabeth Fay Belshe ◽  
Matern S. P. Mtolera ◽  
...  
Keyword(s):  
Resource Competition ◽  
Plant Size ◽  
Maximum Length ◽  
Competitive Interactions ◽  
Size Difference ◽  
Seagrass Species ◽  
Thalassia Hemprichii ◽  
Functional Strategy ◽  
Seagrass Meadows ◽  
Halophila Ovalis

Tropical seagrass meadows are formed by an array of seagrass species that share the same space. Species sharing the same plot are competing for resources, namely light and inorganic nutrients, which results in the capacity of some species to preempt space from others. However, the drivers behind seagrass species competition are not completely understood. In this work, we studied the competitive interactions among tropical seagrass species of Unguja Island (Zanzibar, Tanzania) using a trait-based approach. We quantified the abundance of eight seagrass species under different trophic states, and selected nine traits related to light and inorganic nutrient preemption to characterize the functional strategy of the species (leaf maximum length and width, leaves per shoot, leaf mass area, vertical rhizome length, shoots per meter of ramet, rhizome diameter, roots per meter of ramet, and root maximum length). From the seagrass abundance we calculated the probability of space preemption between pairs of seagrass species and for each individual seagrass species under the different trophic states. Species had different probabilities of space preemption, with the climax species Thalassodendron ciliatum, Enhalus acoroides, Thalassia hemprichii, and the opportunistic Cymodocea serrulata having the highest probability of preemption, while the pioneer and opportunistic species Halophila ovalis, Syringodium isoetifolium, Halodule uninervis, and Cymodocea rotundata had the lowest. Traits determining the functional strategy showed that there was a size gradient across species. For two co-occurring seagrass species, probability of preemption was the highest for the larger species, it increased as the size difference between species increased and was unaffected by the trophic state. Competitive interactions among seagrass species were asymmetrical, i.e., negative effects were not reciprocal, and the driver behind space preemption was determined by plant size. Seagrass space preemption is a consequence of resource competition, and the probability of a species to exert preemption can be calculated using a trait-based approach.

scholarly journals Experimental evidence that belowground competition can influence the evolution of root traits in two closely related morning glory species

2019 ◽  
Author(s):  
Sara M. Colom ◽  
Regina S. Baucom
Keyword(s):  
Critical Role ◽  
Natural Populations ◽  
Root Traits ◽  
The United States ◽  
Morning Glory ◽  
Competitive Interactions ◽  
Plant Interactions ◽  
Belowground Competition ◽  
Ipomoea Purpurea ◽  
Root Angle

AbstractAlthough root traits play a critical role in mediating plant-plant interactions and resource acquisition from the soil environment, research examining if and how belowground competition can influence the evolution of root traits remains largely unexplored. Here we examine the potential that root traits may evolve as a target of selection from interspecific competition using Ipomoea purpurea and I. hederacea, two closely related morning glory species that commonly co-occur in the United States. We show that belowground competitive interactions between the two species can alter the pattern of selection on root traits in each species. Specifically, competition with I. purpurea changes the pattern of selection on root angle in I. hederacea, and competitive interactions with I. hederacea changes the pattern of selection on root size in I. purpurea. However, we did not uncover evidence that intraspecific competition altered the pattern of selection on any root traits within I. hederacea. Overall, our results suggest that belowground competition between closely related species can influence the phenotypic evolution of root traits in natural populations. Our findings provide a microevolutionary perspective of how competitive belowground interactions may impact plant fitness, potentially leading to patterns of plant community structure.

scholarly journals Do interactions between plant and soil biota change with elevation? A study on Fagus sylvatica

2011 ◽  
Vol 7 (5) ◽  
pp. 699-701 ◽  
Author(s):  
Emmanuel Defossez ◽  
Benoît Courbaud ◽  
Benoît Marcais ◽  
Wilfried Thuiller ◽  
Elena Granda ◽  
...  
Keyword(s):  
Fagus Sylvatica ◽  
Elevation Gradient ◽  
Biotic Interactions ◽  
Theoretical Models ◽  
Tree Regeneration ◽  
Soil Biota ◽  
Positive Interactions ◽  
Plant Interactions ◽  
Tree Survival ◽  
Plant Plant

Theoretical models predict weakening of negative biotic interactions and strengthening of positive interactions with increasing abiotic stress. However, most empirical tests have been restricted to plant–plant interactions. No empirical study has examined theoretical predictions of interactions between plants and below-ground micro-organisms, although soil biota strongly regulates plant community composition and dynamics. We examined variability in soil biota effects on tree regeneration across an abiotic gradient. Our candidate tree species was European beech ( Fagus sylvatica L.), whose regeneration is extremely responsive to soil biota activity. In a greenhouse experiment, we measured tree survival in sterilized and non-sterilized soils collected across an elevation gradient in the French Alps. Negative effects of soil biota on tree survival decreased with elevation, similar to shifts observed in plant–plant interactions. Hence, soil biota effects must be included in theoretical models of plant biotic interactions to accurately represent and predict the effects of abiotic gradient on plant communities.

scholarly journals The Influence of Plant Dominants on the Associated Species Abundance in Wet Tall-Herb Meadow Plant Communities

2018 ◽  
Vol 72 (4) ◽  
pp. 244-251
Author(s):  
Vera Lebedeva ◽  
Marina Tikhodeyeva ◽  
Elena Koptseva
Keyword(s):  
Plant Communities ◽  
Species Abundance ◽  
Positive Interactions ◽  
Percent Cover ◽  
Plant Interactions ◽  
Deschampsia Cespitosa ◽  
Filipendula Ulmaria ◽  
Anthriscus Sylvestris ◽  
Negative Effect ◽  
Associated Species

Abstract Plant interactions in wet tall-herb meadow plant communities were described through dominant and edificator species identification. Five dominant species were identified: Alopecurus pratensis, Filipendula ulmaria, Deschampsia cespitosa, Anthriscus sylvestris, and Angelica sylvestris. The effects of species were studied using ANOVA and correlation analyses. Not all dominants were recognised as edificators. Edificators (Alopecurus pratensis, Filipendula ulmaria, Deschampsia cespitosa, Angelica sylvestris) had a negative effect on the various abundance indicators of associated species: percent cover, number, phytomass, and height. The edificator effects differed significantly in their level and duration and depended on the biomorphs of dominants. The perennial species Alopecurus pratensis, Filipendula ulmaria, and Deschampsia cespitosa were strong constant edificators. Angelica sylvestris, a short-lived monocarpic from the Apiaceae, is a weak seasonal edificator, while Anthriscus sylvestris is not an edificator. Analysis of the life strategies of species showed that competitors are not always edificators (Anthriscus sylvestris), whereas stress-tolerant may show edificator properties (Deschampsia cespitosa). The associated plant species often show positive interactions. Most of the associated species are stress-tolerant and have not an edificator effect.

Size Dependence in Assemblage Measures: Essentialism, Materialism, and “She” Analysis in Archaeology

2010 ◽  
Vol 75 (4) ◽  
pp. 886-906 ◽  
Author(s):  
Michael J. Shott
Keyword(s):  
Size Dependence ◽  
Theoretical Models ◽  
Ideal Types ◽  
Size Dependent ◽  
Methodological Bias ◽  
Joint Study ◽  
Complex Relationships ◽  
Meaningful Relationships ◽  
Tool Types ◽  
She Analysis

"Assemblage" is a fundamental archaeological construct. By their composition, we interpret assemblages as expressions of activity or cultural identity. Yet they are not simple products of these factors alone but also of formation processes. Assemblages accumulated over varying spans, with varying combinations of tool types and discard rates. They are contexts for the playing out of complex relationships, not static types. This is a materialist view, against the essentialist view that assemblages are exemplars of ideal types (e.g., "base camps," "Quina Mousterian"). Materialism implies that their size and composition, fundamental assemblage characteristics, are correlated variables, not fixed properties, and that composition varies as size increases. I document size dependence consistent with materialism in Paleoindian and Paleolithic assemblages. Among ways to analyze size-dependent assemblage data, I apply "SHE analysis"—the joint study of assemblage richness, heterogeneity, and evenness—to gauge data’s fit to theoretical models. Archaeologists acknowledge size dependence, but we misapprehend it as a methodological bias of assemblage measures that must be suppressed when, in materialist perspective, it reveals meaningful relationships that an essentialist view cannot.

SIZE-DEPENDENT EFFECTS IN ATOMIC CLUSTERS

2020 ◽  
Author(s):  
A. S. Sharipov ◽  
◽  
B. I. Loukhovitski ◽  
Keyword(s):  
Binding Energy ◽  
Physical Properties ◽  
Size Dependence ◽  
Atomic Clusters ◽  
Energy Collision ◽  
Size Dependent

The size-dependence of different physical properties of atomic clusters (by the example of binding energy, collision diameter, and static isotropic polarizability) is discussed.

scholarly journals The evolution of size‐dependent competitive interactions promotes species coexistence

2021 ◽  
Author(s):  
Jaime M. Anaya‐Rojas ◽  
Ronald D. Bassar ◽  
Tomos Potter ◽  
Allison Blanchette ◽  
Shay Callahan ◽  
...  
Keyword(s):  
Species Coexistence ◽  
Competitive Interactions ◽  
Size Dependent

An ecological explanation for hyperallometric scaling of reproduction

2021 ◽  
Author(s):  
Tomos Potter ◽  
Anja Felmy
Keyword(s):  
Body Size ◽  
Reproductive Output ◽  
Resource Competition ◽  
Natural Populations ◽  
Scaling Exponent ◽  
Wild Populations ◽  
Wet Season ◽  
Size Dependent ◽  
In The Wild ◽  
The Relationship

AbstractIn wild populations, large individuals have disproportionately higher reproductive output than smaller individuals. We suggest an ecological explanation for this observation: asymmetry within populations in rates of resource assimilation, where greater assimilation causes both increased reproduction and body size. We assessed how the relationship between size and reproduction differs between wild and lab-reared Trinidadian guppies. We show that (i) reproduction increased disproportionately with body size in the wild but not in the lab, where effects of resource competition were eliminated; (ii) in the wild, the scaling exponent was greatest during the wet season, when resource competition is strongest; and (iii) detection of hyperallometric scaling of reproduction is inevitable if individual differences in assimilation are ignored. We propose that variation among individuals in assimilation – caused by size-dependent resource competition, niche expansion, and chance – can explain patterns of hyperallometric scaling of reproduction in natural populations.

Ecological field theory model: a mechanistic approach to simulate plant–plant interactions in southeastern forest ecosystems

1993 ◽  
Vol 23 (10) ◽  
pp. 2180-2193 ◽  
Author(s):  
Pu Mou ◽  
Robert J. Mitchell ◽  
Robert H. Jones
Keyword(s):  
Field Theory ◽  
Loblolly Pine ◽  
Vegetation Dynamics ◽  
Plant Size ◽  
Theory Model ◽  
Plant Interactions ◽  
Simulation Accuracy ◽  
Individual Level ◽  
The Individual ◽  
Plant Plant

Ecological field theory, unlike many other vegetation modeling approaches, provides a basis to construct an individually based, spatially explicit, and resource-mediated model for mechanistic simulation of plant–plant interactions and vegetation dynamics. The model REGROW has been developed, based on ecological field theory principles, to simulate vegetation dynamics for northern hardwood forests. Using data from a current study of a southern pine system to calibrate a modified version of this model, SPGROW, we simulated growth of individuals for the first growing season in stands of loblolly pine (Pinustaeda L.) and sweetgum (Liquidambarstyraciflua L.) seedlings and loblolly pine seedling–sweetgum sprout mixtures. SPGROW accurately simulated stand development at population and stand levels. However, less agreement occurred at the individual level between simulated and field survey values, possibly owing to lack of data on site heterogeneity and genetic variation. Plant interactions, which altered resource availability (light, water, and nutrients) to individual plants, played a major role in differentiating plant size in the model. Given its unique model structure and simulation accuracy, SPGROW has the potential to provide very detailed insight into the mechanisms of plant–plant interactions.

scholarly journals Size-dependent allocation of biomass to ancillary versus flowers of the inflorescences of the epiphyte Tillandsia stricta Soland (Bromeliaceae)

2009 ◽  
Vol 23 (1) ◽  
pp. 130-135 ◽  
Author(s):  
André Mantovani ◽  
Ricardo Rios Iglesias
Keyword(s):  
Leaf Area ◽  
Plant Species ◽  
Vegetative Growth ◽  
Reproductive Investment ◽  
Plant Size ◽  
Reproductive Allocation ◽  
Heterogeneous Environment ◽  
Plant Resources ◽  
Total Leaf Area ◽  
Size Dependent

The amount of resources invested in reproduction is closely correlated to plant size. However, the increase in reproductive investment is not always proportional to the increase in vegetative growth, as the proportion of plant resources allocated to reproduction can increase, decrease or be maintained along different plant sizes. Although comprising thousand of species, epiphytes are poorly studied in relation to reproductive allocation (RA). We describe the variation in the RA of the epiphytic bromeliad Tillandsia stricta Soland with increasing plant sizes. Our goal is not only to evaluate the RA of the whole inflorescence but also quantify the contribution of ancillary structures in the final RA of this plant species. With increasing sizes of T. stricta the reproductive allocation of biomass to the whole inflorescence decreased significantly along plant sizes from 37% to 12%. Reproductive allocation to ancillary and to flowers decreased respectively from 30% to 9% and 10% to 3%. As leaves are the main source of water and nutrients absorption in atmospheric Tillandsia, the total leaf area and area per leaf were used as indicators of foraging capacity, that also increased with plant size. We discuss these results with respect to the capacity of T. stricta to reproduce in the heterogeneous environment of the canopies.

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