Competitive Hierarchies in Herbaceous Plant Communities

Keddy, Paul A.; Shipley, Bill

doi:10.2307/3565272

Cited by 282 publications

(259 citation statements)

References 28 publications

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“…This question can be partially answered by studies that compete all possible pairs of plant species from a defined community. Although prior reviews of such studies have emphasized that certain species tend to win in competition and others tend to lose (30,31), these studies often show that some poorly ranked competitors (those that tend to lose to other species) beat some species of generally higher rank (those that tend to win), and sometimes of much higher rank (32,33). Importantly, these empirical results likely underestimate the frequency of intransitive competitive relationships because they are almost always conducted in greenhouse pot experiments.…”

Section: Discussionmentioning

confidence: 75%

A competitive network theory of species diversity

Allesina

Levine²

2011

Proc. Natl. Acad. Sci. U.S.A.

326

386

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Nonhierarchical competition between species has been proposed as a potential mechanism for biodiversity maintenance, but theoretical and empirical research has thus far concentrated on systems composed of relatively few species. Here we develop a theory of biodiversity based on a network representation of competition for systems with large numbers of competitors. All species pairs are connected by an arrow from the inferior to the superior. Using game theory, we show how the equilibrium density of all species can be derived from the structure of the network. We show that when species are limited by multiple factors, the coexistence of a large number of species is the most probable outcome and that habitat heterogeneity interacts with network structure to favor diversity.competitive exclusion | rock-paper-scissor | neutral theory | niche theory E cologists have long sought to explain how a wide diversity of species coexists in nature (1). Coexistence is a conundrum because if two species share the same niche, the competitive exclusion principle predicts the extinction of the inferior competitor (2). This foundational principle continues to motivate advances in niche and neutral theories (3-5) of coexistence, which use niche differences and species equivalence, respectively, to avoid competitive exclusion. However, each theory suffers shortcomings. Field evidence that classic resource-based niche differences are essential for coexistence is rare (6-8), whereas the species equivalence assumption of neutral theory is hard to reconcile with nature. These shortcomings justify the quantitative exploration of less conventional niche mechanisms of coexistence.Here, we ask how embedding pairs of superior and inferior species in a network of competitors alters the outcome of competition and influences patterns of relative abundance. We find that although the competitive exclusion principle certainly holds for any pair of competitors, when multiple factors determine the outcome of competition and species are embedded in competitive networks, a large number of species can coexist. The coexistence relies on the stabilizing effect of intransitivities (9-12) that emerge in these networks rather than more traditional pairwise niche differences. By combining a game theoretical framework with graph theory and dynamical systems (13, 14), we show how the equilibrium abundance of all species can be determined from the competitive network, how species diversity relates to the number of limiting factors, and how spatial heterogeneity combines with intransitivity to interactively favor diversity maintenance. ModelThe pairwise competitive relationships between species in a community can be expressed as a network, or more formally, a tournament, in which species are the nodes and arrows connect the competitive inferior to the superior competitor (Fig. 1A). In the simplest case, where all species in a system compete for a single limiting resource, their competitive abilities should be transitive: Species A beats all others, B beats all but...

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Section: Discussionmentioning

confidence: 75%

A competitive network theory of species diversity

Allesina

Levine²

2011

Proc. Natl. Acad. Sci. U.S.A.

326

386

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“…Grime et al (1997) postulated the existence of a fundamental axis of specialization in plants along the resource availability gradient that results from a trade-off between attributes that confer species an advantage when resources are in high supply (resource acquisition strategies), and those that are beneficial for plant performance in chronically poor environments (resource retention strategies). Evidence from numerous empirical and observational studies (Keddy and Shipley 1989;Goldberg 1996;Westoby 1998;Westoby et al 2002) support the association between plant height and the species competitive ability when resources are in high supply, and between leaf traits (e.g., leaf area and LDMC, and SLA -although in this case, less consistent) and the amount of resources available for plant growth (Kazakou et al 2006;Rusch et al 2009). The distribution of clonal attributes also appears to vary along the resource availability axis (van Groenendael et al 1996;Klimeš et al 1997;Dalgleish and Hartnett 2006) although the amount of evidence is considerably smaller.…”

Section: Discussionmentioning

confidence: 99%

Do Clonal and Bud Bank Traits Vary in Correspondence with Soil Properties and Resource Acquisition Strategies? Patterns in Alpine Communities in the Scandian Mountains

et al. 2010

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Plant traits associated with resource acquisition strategies (specific leaf area (SLA), leaf dry matter content (LDMC), leaf size and plant height) change along gradients of soil properties, being the most conservative in a resource-poor environment and the most dynamic in a resource-rich environment. Clonal attributes also vary along soil and other environmental conditions. We hypothesized that in alpine communities in the Scandian Mts. (1) the average composition of traits in a plant assemblage in terms of i) the predominance of different clonal growth organ types, ii) the number of buds in the bud bank, iii) the distribution of the bud-bank (above-and below ground), iv) the distance of lateral spread and v) the longevity of plant -offspring connections would change along a gradient of soil properties and (2) that this variation would be in correspondence with that of traits associated with resource acquisition strategies (SLA, LDMC, leaf size and plant height). Analysis of clonal and bud bank traits for species of alpine communities supported our first hypothesis: with decreasing soil quality the most common clonal growth organs were rhizomes, and there was a predominance of perennial bud banks located at the soil surface or below-ground, low rates of lateral spread and long persistence of plant -offspring connections. Our second hypothesis was partly supported. As predicted, at the level of the plant assemblage, these clonal and bud bank traits were positively associated with LDMC, and negatively with leaf size and plant height. These observations reinforce the hypotheses about trade-offs between acquisition and retention strategies in plants. The only result that was in contradiction with our expectations was the lack of correspondence between clonal and bud bank traits and SLA that could be attributed to errors associated to Folia Geobot (2011) 46:237-254 DOI 10.1007

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“…Later in the growing season the taller and early developing variety like barley cv. Arra might not only have access to incoming light for its own growth, but might simultaneously reduce the growth of the smaller plant by setting up a positive feedback loop whereby the larger plant continually improves its access to light and the smaller plant was increasingly denied access to it as shown by Keddy and Shipley (1989). Reduced access to light will reduce carbohydrates available for root growth, thereby reducing rates of nutrient uptake (Tilman 1988).…”

Section: Factors Affecting Competition Between Components and Competimentioning

confidence: 99%

Competition and yield advantage in barley-barley and barley-oats mixtures

Jokinen¹

1991

AFSci

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Competition and yield advantage in barley varietal mixtures and in barley-oats mixtures were investigated. The trials were based on replacement series, but in a few cases the overall density of the stand was varied on the basis of an addition series. Both models of competition, one based on the de Wit model and the other upon a linear regression model, agreed as to which component was the dominant and which was the subordinate in the mixture. The competition coefficients from regression analyses depicted competition between components better in a dense than in a sparse stand. The competitive ability of a genotype did not depend directly upon individual characters of the genotype, such as rate of initial development, earliness, culm height, tillering capacity or grain yield in monoculture (adaptation), A good combination of characters from the viewpoint of competition was provided by the barley cv. Arra with its rapid initial development and rapid culm growth (earliness), the variety being dominant irrespective of number of components in the mixture, stand density, level of nitrogen fertilization or growing season. This suggests that competitive relations and distribution of resources within a mixture are determined at an early stage in the growing period. In other cases the competitive ability of a genotype varied from one environment to another with the competitive relations between components being inconsistent. The dominance of an aggressor usually increased with increasing nitrogen fertilization especially when the total density of the stand was high. As a rule, competition affected all the components of yield with the kernel weight being least affected. The grain yield of varietal mixtures did not differ from the yield of the highest yielding component grown alone, i.e., mixtures did not over yield. The relative yield total of varietal mixtures was higher at low (RYT > 1) than at optimal densities (RYT =1). Also the relative yield total was higher under conditions where the nitrogen fertilization was not optimal. The results of a varietal trial repeated during three successive years indicated that the relative yield total of a given mixture varied from one growing season to another, fluctuating around unity. Thus highly adapted barley varieties appear to compete for the same resources, and the grain yield advantage of such mixtures is marginal. The results of the barley-oats mixture trials revealed that the mixture may over yield. The relative yield totals of barley-oats mixtures were usually equal to or greater than unity the latter suggesting that the mixtures of barley and oats may use resources more efficiently than monocultures, and some grain yield advantage could be achieved with such mixtures. The protein yield of the barley-oats mixtures did not differ from the yield of the highest yielding component grown alone. The ratio of actual and expected protein yield and the relative protein yield total were usually slightly greater than one. The grain yields of mixtures were not consistently more stable than monocultures as determined by the coefficient of variation.

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Competitive Hierarchies in Herbaceous Plant Communities

Cited by 282 publications

References 28 publications

A competitive network theory of species diversity

A competitive network theory of species diversity

Do Clonal and Bud Bank Traits Vary in Correspondence with Soil Properties and Resource Acquisition Strategies? Patterns in Alpine Communities in the Scandian Mountains

Competition and yield advantage in barley-barley and barley-oats mixtures

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