A density-dependent model of Cirsium vulgare population dynamics using field-estimated parameter values

Gillman, Michael; Bullock, James M.; Silvertown, Jonathan; Hill, B. Clear

doi:10.1007/bf00317743

Cited by 30 publications

(32 citation statements)

References 16 publications

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“… References: 1 Jefferies et al 1981, 2 Keddy 1981, 3 Watkinson 1982, 4 Shaw and Antonovics 1986, 5 Gillman et al 1993, 6 Fowler 1995, 7 Castellanos et al 1998, 8 Lintell Smith et al 1999, 9 Silva Matos et al 1999, 10 Buckley et al 2001, 11 Goldberg et al 2001, 12 Gustafsson and Ehrlén 2003, 13 Blundell and Peart 2004, 14 Buckley et al 2005, 15 Kluth and Bruelheide 2005, 16 Sletvold 2005, 17 Rebek and O'Neil 2006, 18 Picó and Retana 2008, 19 Price et al 2008. …”

Section: Methodsmentioning

confidence: 99%

Multiple life stages with multiple replicated density levels are required to estimate density dependence for plants

Ramula¹,

Buckley²

2009

Oikos

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Negative density dependence resulting from intraspecific competition can regulate plant populations by limiting demographic rates (survival, growth, fecundity). However, the strength of intraspecific competition can vary within and among populations due to spatial or temporal environmental heterogeneity, or genetic differences. Quantification of variation under a relatively constant environment is needed to assess the inherent potential for density dependence to vary. This knowledge will help adjust data collection effort required for parameterisation of density dependence. Our review of published plant demographic studies revealed that only half of the studies included the whole life‐cycle in the analysis of density dependence. Approximately half of the studies manipulated density, while the rest examined density dependence from observed densities in the field. Regardless of the design used, density dependence was estimated from a small number of replicates. To investigate inherent variation in density dependence during the life‐cycle, and the effect of low replication on density dependence estimates, we combined an experimental approach with simulations for an invasive herb Senecio madagascariensis. We found significant negative density dependence for five out of six examined demographic rates in a constant environment, with the strength of density dependence increasing during the life‐cycle. An exception was plant growth, in which the direction of density dependence varied from positive to negative depending on the life stage. Simulations showed substantial deviation for density dependence parameterised from a small number of replicates even when environmental variation was minimal. This suggests that data collection procedures currently used to assess the effect of density on plant demographic rates may produce inaccurate estimates, increasing uncertainty in demographic models. Due to variation in the direction and strength of density dependence during the life‐cycle, multiple life stages with multiple replicated density levels are required to parameterise density dependence for demographic rates.

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Section: Methodsmentioning

confidence: 99%

Multiple life stages with multiple replicated density levels are required to estimate density dependence for plants

Ramula¹,

Buckley²

2009

Oikos

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“…0.38). Several studies on effects of non-native grazers (Gillman et al 1993;Bullock et al 1994;Bastrante et al 1995;Lennartsson & Oostermeijer 2001) have shown that these consumers can have positive to mildly or even strongly negative effects on l depending on whether consumers have mostly indirect or direct effects on vegetation. Where sheep act solely as agents of disturbance and create gaps in vegetation (e.g.…”

Section: Consumer Effects On Plant Abundance and Distribution: How Mumentioning

confidence: 99%

Herbivory: effects on plant abundance, distribution and population growth

2006

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Plants are attacked by many different consumers. A critical question is how often, and under what conditions, common reductions in growth, fecundity or even survival that occur due to herbivory translate to meaningful impacts on abundance, distribution or dynamics of plant populations. Here, we review population-level studies of the effects of consumers on plant dynamics and evaluate: (i) whether particular consumers have predictably more or less influence on plant abundance, (ii) whether particular plant lifehistory types are predictably more vulnerable to herbivory at the population level, (iii) whether the strength of plant-consumer interactions shifts predictably across environmental gradients and (iv) the role of consumers in influencing plant distributional limits. Existing studies demonstrate numerous examples of consumers limiting local plant abundance and distribution. We found larger effects of consumers on grassland than woodland forbs, stronger effects of herbivory in areas with high versus low disturbance, but no systematic or unambiguous differences in the impact of consumers based on plant life-history or herbivore feeding mode. However, our ability to evaluate these and other patterns is limited by the small (but growing) number of studies in this area. As an impetus for further study, we review strengths and challenges of population-level studies, such as interpreting net impacts of consumers in the presence of density dependence and seed bank dynamics.

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“…While the role of density dependence in the population dynamics of plants has been clearly demonstrated for a range of annuals and herbaceous perennials (e.g., Barkham and Hance 1982, Watkinson et al 1989, Gillman et al 1993, Rees et al 1996, the role of density dependence in the population dynamics of trees, and especially tropical trees, is much less clear. That density dependence occurs in tropical trees is not in dispute (Alvarez- Buylla et al 1996).…”

Section: Introductionmentioning

confidence: 99%

The Role of Density Dependence in the Population Dynamics of a Tropical Palm

Matos¹,

Freckleton²,

Watkinson³

1999

Ecology

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology.Abstract. The role of density dependence in the population dynamics of tropical trees has been a subject of considerable debate. Here, we present data on the demography of the edible palm Euterpe edulis, classified into seven size categories and monitored over three years. On average, each adult palm contributed 98 seedling recruits per year into the population. The pattern of mortality was similar to that of other palms, with mortality being highest among the smallest plants. Those plants with a diameter at soil level >20 mm had an annual mortality <7%. Density dependence was found to act only on the seedling stage of the life cycle. The probability of survival and transition of seedlings to the next size class were affected both by the density of seedlings and the presence of conspecific adults. Matrix modeling indicated that the true finite rate of population increase (X) was 1.28 and that the observed reverse "J"-shaped size distribution of plants was a consequence of the density dependence operating in the population. Elasticity analysis showed that the survival elements in the matrix contributed most to the value of X, and that the position of the transition matrix in growth-survival-fecundity (G-L-F) space was influenced by density. The matrix model incorporating density dependence predicted size distributions and densities approximating the maximum observed in the field. Spatial simulations indicated that the predictions from the matrix model relating to the size structure of plants are robust, but that the predictions of densities are sensitive to the precise spatial dynamics of the population.1979, Hubbell and Foster 1986), known as the community drift model. In contrast to this nonequilibrium model, it has been argued at the other extreme that density-dependent and distance-related recruitment may be responsible for the low mean densities of many tropical trees and the consequent high species diversity (Janzen 1970, Connell 1971. In this latter case, specialist herbivores, seed predators, and pathogens are envisaged as maintaining populations around low densities and high species diversity. Critics of the Janzen-Connell model have suggested that the strength of density dependence is insufficient to remove the clumped distributions of seedlings beneath parents (Hubbell 1980). The community drift model of tropical forest dynamics, on the other hand, has also been criticized on the basis that it fails to take into account high levels of compositional similarity in disjunct samples of forest (Terborgh et al. 1996). Moreover, Wills et al. (1997) have found that int...

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A density-dependent model of Cirsium vulgare population dynamics using field-estimated parameter values

Cited by 30 publications

References 16 publications

Multiple life stages with multiple replicated density levels are required to estimate density dependence for plants

Multiple life stages with multiple replicated density levels are required to estimate density dependence for plants

Herbivory: effects on plant abundance, distribution and population growth

The Role of Density Dependence in the Population Dynamics of a Tropical Palm

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