Browsing by Subject "resource availability"

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    Direct and indirect effects of CO2, nitrogen, and community diversity on plant–enemy interactions
    (Ecological Society of America, 2008) Lau, Jennifer A; Strengbom, Joachim; Stone, Laurie R; Reich, Peter B; Tiffin, Peter
    Resource abundance and plant diversity are two predominant factors hypothesized to influence the amount of damage plants receive from natural enemies. Many impacts of these environmental variables on plant damage are likely indirect and result because both resource availability and diversity can influence plant traits associated with attractiveness to herbivores or susceptibility to pathogens. We used a long-term, manipulative field experiment to investigate how carbon dioxide (CO2) enrichment, nitrogen (N) fertilization, and plant community diversity affect plant traits and the amount of herbivore and pathogen damage experienced by the common prairie legume Lespedeza capitata. We detected little evidence that CO2 or N affected plant traits; however, plants growing in high-diversity treatments (polycultures) were taller, were less pubescent, and produced thinner leaves (higher specific leaf area). Interestingly, we also detected little evidence that CO2 or N affect damage. Plants growing in polycultures compared to monocultures, however, experienced a fivefold increase in damage from generalist herbivores, 64% less damage from specialist herbivores, and 91% less damage from pathogens. Moreover, within diversity treatments, damage by generalist herbivores was negatively correlated with pubescence and often was positively correlated with plant height, while damage by specialist herbivores typically was positively correlated with pubescence and negatively associated with height. These patterns are consistent with changes in plant traits driving differences in herbivory between diversity treatments. In contrast, changes in measured plant traits did not explain the difference in disease incidence between monocultures and polycultures. In summary, our data provide little evidence that CO2 or N supply alter damage from natural enemies. By contrast, plants grown in monocultures experienced greater specialist herbivore and pathogen damage but less generalist herbivore damage than plants grown in diverse communities. Part of this diversity effect was mediated by changes in plant traits, many of which likely are plastic responses to diversity treatments, but some of which may be the result of evolutionary changes in response to these long-term experimental manipulations.
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    Species interactions in a changing environment: Elevated CO2 alters the ecological and potential evolutionary consequences of competition
    (Evolutionary Ecology, 2010) Lau, Ja; Shaw, R G; Reich, Peter B; Tiffin, P
    Question: How will global changes impact the ecological and evolutionary outcomes of competition? Hypothesis: Global changes that alter resource availability, such as rising atmospheric carbon dioxide (CO2) concentrations, will alter the effects of competition on mean fitness and patterns of natural selection. Because species exhibit different growth responses to elevated CO2 and because different traits may aid in competition against different taxa. these ecological and evolutionary effects may depend on the Identity of the competitor Organism: Arabidopsis thaliana grown under intraspecific competition or interspecific competition with the C3 grass Biomus inermis or the C4 grass Andropogon gerardu Field site: BioCON (Biodiversity, CO2, and Nitrogen) experiment at Cedar Creek Ecosystem Science Reserve. Minnesota, USA Methods: Manipulate the presence and type of competition experienced by A thaliana populations growing under ambient or elevated CO2 conditions. Measure the interactive effects of CO2 and competition on mean fitness and on patterns of natural selection Conclusions: Elevated CO2 reduces the effects of competition on mean fitness, alters the relative fitness effects of different competition treatments, and minimizes the strength of competition as a selective agent