Differential herbivory tolerance of dominant and subordinate plant species along gradients of nutrient availability and competition
TL;DR: It is suggested that species replacement towards subordinate species as a function of herbivory is partially dependent on the Herbivory tolerance of that species and increasing nutrient levels counteract the negative effect of grazing on dominant competitive plant species.
Abstract: We tested whether differences in the herbivory tolerance of plant species is related to their abundance in grassland communities and how herbivory and nutrient availability affect competitive balances among plant species through changes in their tolerance. The experimental approach involved a simulated grazing treatment (clipping) of two competitive grass species (Arrhenatherum elatius and Holcus lanatus) and two subordinate forb species (Prunella vulgaris and Lotus corniculatus) along a gradient of nutrient availability and under conditions of competition. Total standing, aboveground, root, and regrowth biomass were evaluated at the end of the experiment as an estimate of the capacity to compensate for twice removing aboveground biomass at different nutrient levels (NPK). Although clipping had a more pronounced negative effect on dominant plant species (Arrhenatherum and Holcus) than on subordinate species, the negative effects on dominant species were offset by the application of fertilizer. The combined effect of fertilizer and competition had more negative effects on the performance of Lotus and Prunella than on the dominant species. In terms of competition, the regrowth ability of Arrhenatherum and Holcus increased with the application of fertilizer, while the opposite pattern was observed for Lotus and Prunella. The addition of fertilizer has a positive effect on both grass species in terms of growth in clipped pots and competition, while subordinate species did not respond to the addition of fertilizer to the clipped pots and were negatively affected by competition with both grass species. The results suggest (1) that species replacement towards subordinate species as a function of herbivory is partially dependent on the herbivory tolerance of that species, (2) competitive relations between competitive grass species and subordinate forb species change under different environmental conditions, and (3) although grazing disturbance significantly influences competitive relations in favor of less competitive species, increasing nutrient levels counteract the negative effect of grazing on dominant competitive plant species.
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TL;DR: The necessity of integrating tolerance into ecological and co-evolutionary theory to better understand the biology of this defensive mechanism is highlighted.
Abstract: Summary
1. Plant tolerance to herbivory has been accepted as a mechanism of defense that can be expressed jointly with resistance. Recent advances have partially validated previous theoretical predictions and improved our understanding of tolerance. Here, I highlight the necessity of integrating tolerance into ecological and co-evolutionary theory to better understand the biology of this defensive mechanism.
2. Existing work has been biased toward understanding the adaptive nature and constraints acting on tolerance rather than its ecological implications. Increasing consensus that tolerance may alter the classical antagonistic dynamic between plants and herbivores suggests possible avenues to explore its population and community consequences.
3. In this review, I summarize previous advances in the ecology and evolution of tolerance to herbivory. I also discuss recent evidence that improves our understanding of unresolved issues such as the specificity of tolerance in response to herbivory, its role as an agent of selection on herbivores, and its ecological and evolutionary consequences which include a role of tolerance during biological invasions.
4. Although there is good support for an adaptive role of tolerance in response to herbivory damage, tolerance can itself impose selection on herbivores. Furthermore, tolerance can influence herbivore population dynamics and coexistence, as recent studies show that tolerance responses increase diversity of the associated herbivore communities on individual host plants.
5. Future studies that take into account the role of herbivores on the expression of tolerance will provide novel insight that will help disentangle the mechanisms of tolerance and its ecological and evolutionary implications.
218 citations
TL;DR: It is demonstrated that, independent of plant diversity, the presence of drought-resistant subordinate species increases plant community insurance against drought and, hence, is important for the functioning of grassland ecosystems.
Abstract: According to the insurance hypothesis, more diverse plant communities are more likely to be resistant to drought. Whilst many experiments have been carried out to determine the effects of plant diversity on plant community insurance, the results are still contradictory. Here, we conducted a drought experiment where we tested whether the presence of subordinate species increases plant community insurance. In Swiss Jura grassland, we combined a removal experiment of subordinate species with a summer drought event using rainout shelters. Plant community composition was determined after the drought and based on biomass measurements; we estimated resistance, recovery and resilience of the plant community for each combination of treatments. Moreover, to assess drought impacts on water-use efficiency (WUE), we analysed carbon isotope ratios (13C values) in plant leaves of two dominants and two subordinates collected at the end of the drought period. We showed that subordinate species are more resistant to drought and increased community resistance by enhancing their above-ground biomass production during the imposed drought. These patterns were associated with decreased competitiveness of dominant species whose biomass decreased during drought. Significant increase in 13C values in plant tissue under drought indicated a better WUE for the measured species. Interestingly, the WUE was significantly higher in plots where subordinates were removed. Recovery and resilience were not affected by the summer drought, but the absence of subordinates reduced overall above-ground biomass in both watered and drought plots. Synthesis. We demonstrated that, independent of plant diversity, the presence of drought-resistant subordinate species increases plant community insurance against drought and, hence, is important for the functioning of grassland ecosystems.
131 citations
Cites background or result from "Differential herbivory tolerance of..."
...…these semi-natural grasslands, subordinate species seem to benefit from cattle activity because large grazers create gaps and areas of reduced root competition from dominants (Mariotte et al. 2012a) or because subordinates regrow better after grazing than dominants (Tahmasebi Kohyani et al. 2009)....
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...2b), and this confirms findings from a previous study which showed that subordinates regrow more after grazing (Tahmasebi Kohyani et al. 2009)....
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TL;DR: This special feature is a broad synthesis of the evolution and ecology of plant defences and addresses three fundamental questions: How do plants defend themselves against a diverse array of enemies, why do plant species vary in defence and what are the ecological and ecosystem-level consequences of plant defence.
Abstract: Summary
1. Herbivores consume a large portion of the biomass produced by plants in virtually all ecosystems, which has dramatic effects on both the ecology and evolution of plants. In response to this threat, plants have evolved a diverse arsenal of direct and indirect defences to reduce herbivory and the impacts of damage on plant performance.
2. This special feature is a broad synthesis of the evolution and ecology of plant defences. The first objective of this special feature is to provide a review of what we have learned about plant defences against herbivores. The second objective is to stimulate debate and sow fresh ideas for the future research.
3. The 11 articles in this issue address three fundamental questions: (i) How do plants defend themselves against a diverse array of enemies? (ii) Why do plant species vary in defence? And (iii) What are the ecological and ecosystem-level consequences of plant defence? In addressing these questions the articles cover the interdisciplinary nature of plant–herbivore evolutionary ecology, from genes to global patterns.
4. The articles contained in the special feature question existing paradigms and provide new analyses of data. In some cases, influential hypotheses are firmly supported with new analyses (e.g. the Resource Availability Hypothesis), whereas in other instances conventional wisdom is called into question (e.g. the importance of secondary metabolites in the microevolution of resistance) and popular hypotheses are rejected (e.g. the Apparency Hypothesis, the Latitudinal Biotic Interaction Hypothesis).
5. This is an exciting time for research on the evolutionary ecology of plant defences. The articles in this special feature provide a guide to how we can move forward in resolving existing problems and tackling new questions.
95 citations
TL;DR: It is indicated that the loss of subordinate species can have significant consequences for soil microbial communities and ecosystem functions, suggesting that subordinate species are important drivers of ecosystem properties.
Abstract: Despite their low relative abundance, subordinate plant species may have larger impacts on ecosystem functioning than expected, but their role in plant communities remains poorly understood. The aim of this study was to test how subordinate plant species influence the functioning of a species-rich semi-natural grasslands. A plant removal experiment was set-up in the mountain grasslands of the Jura Mountains (Switzerland) to test the impact of subordinate plant species on soil microbial communities and ecosystem functioning. The experiment included three treatments: removal of all subordinate species, partial biomass removal of dominant species, and a no biomass removal control. After 2 years of treatments, we determined soil microbial community (bacteria and mycorrhizal fungi) by T-RFLP analysis and measured litter decomposition, soil respiration, soil inorganic nitrogen (DIN) availability and throughout aboveground biomass production as measures of ecosystem function. The removal of subordinate plant species strongly affected bacterial and weakly influenced mycorrhizal fungi communities and decreased rates of plant litter decomposition, soil respiration and DIN availability with larger effects than the partial loss of dominant biomass. The removal of subordinate plant species did not modify plant community structure, but it did reduce total above-ground biomass production compared to the control plots. Collectively, our findings indicate that the loss of subordinate species can have significant consequences for soil microbial communities and ecosystem functions, suggesting that subordinate species are important drivers of ecosystem properties. (C) 2012 Elsevier GmbH. All rights reserved.
39 citations
TL;DR: In this article, the authors presented a new scheme for aDGVM2, a dynamic vegetation model for tropical ecosystems, that distinguishes annual and perennial grasses based on trait trade-offs to improve the representation of rangeland communities.
33 citations
References
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Book•
01 Jan 1982
TL;DR: This book builds a mechanistic, resource-based explanation of the structure and functioning of ecological communities and explores such problems as the evolution of "super species," the differences between plant and animal community diversity patterns, and the cause of plant succession.
Abstract: One of the central questions of ecology is why there are so many different kinds of plants and animals Here David Tilman presents a theory of how organisms compete for resources and the way their competition promotes diversity Developing Hutchinson's suggestion that the main cause of diversity is the feeding relations of species, this book builds a mechanistic, resource-based explanation of the structure and functioning of ecological communities In a detailed analysis of the Park Grass Experiments at the Rothamsted Experimental Station in England, the author demonstrates that the dramatic results of these 120 years of experimentation are consistent with his theory, as are observations in many other natural communities The consumer-resource approach of this book is applicable to both animal and plant communities, but the majority of Professor Tilman's discussion concentrates on the structure of plant communities All theoretical arguments are developed graphically, and formal mathematics is kept to a minimum The final chapters of the book provide some testable speculations about resources and animal communities and explore such problems as the evolution of "super species," the differences between plant and animal community diversity patterns, and the cause of plant succession
5,795 citations
"Differential herbivory tolerance of..." refers background in this paper
...However, this allocation capability depends on the amount of nutrients available in the soil (Tilman 1982; Huisman et al. 1999; Kuijper et al. 2005)....
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Book•
01 Jan 1979
TL;DR: In this paper, the authors present plant strategies in the established phase and the regenerative phase in the emerging phase, respectively, and discuss the relationship between the two phases: primary strategies and secondary strategies.
Abstract: PLANT STRATEGIES. Primary Strategies in the Established Phase. Secondary Strategies in the Established Phase. Regenerative Strategies. VEGETATION PROCESSES. Dominance. Succession. Co-Existence. References. Index.
5,687 citations
Book•
01 Mar 1988
TL;DR: Tilman et al. as mentioned in this paper showed that relative growth rate, which is predicted by a plant's proportional allocation to leaves, is a major determinant of the transient dynamics of competition.
Abstract: Although ecologists have long considered morphology and life history to be important determinants of the distribution, abundance, and dynamics of plants in nature, this book contains the first theory to predict explicitly both the evolution of plant traits and the effects of these traits on plant community structure and dynamics. David Tilman focuses on the universal requirement of terrestrial plants for both below-ground and above-ground resources. The physical separation of these resources means that plants face an unavoidable tradeoff. To obtain a higher proportion of one resource, a plant must allocate more of its growth to the structures involved in its acquisition, and thus necessarily obtain a lower proportion of another resource. Professor Tilman presents a simple theory that includes this constraint and tradeoff, and uses the theory to explore the evolution of plant life histories and morphologies along productivity and disturbance gradients. The book shows that relative growth rate, which is predicted to be strongly influenced by a plant's proportional allocation to leaves, is a major determinant of the transient dynamics of competition. These dynamics may explain the differences between successions on poor versus rich soils and suggest that most field experiments performed to date have been of too short a duration to allow unambiguous interpretation of their results.
2,265 citations
902 citations
"Differential herbivory tolerance of..." refers background in this paper
...A long-lasting debate among experts in the field of vegetation ecology concerns the interactive influence of competition and herbivory along the gradient of productivity (Tilman 1988; Grime 2001)....
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TL;DR: Differences among ecosystems in the role played by ungulate herbivory result from the relative strength of these factors enhancing plant tolerance to herbvory and limiting foraging selectivity, a review of studies of ungulates' effects on plant community composition indicates.
Abstract: Large mammalian herbivores not only depend on plant communities for their existence but cause major changes in plant community composition and structure, These changes have direct consequences for ecosystem processes, but recent studies of ungulate-ecosystem relations show widely divergent ungulate effects in different ecosystems. We reviewed studies of ungulate effects on plant community composition to gain insight into potential mechanisms of ungulate-induced changes in both community composition and ecosystem processes. Our analysis of these studies is based on the premise that the effect ungulates exert on plant communities depends on the balance between (1) feeding selectivity of herbivores (i.e., degree to which different plant species or ecotypes experience different levels of tissue loss), and (2) differences among plant species in their ability to recover from tissue loss. A large number of studies clearly show that selective ungulate herbivory leads to the dominance of unpalatable, chemically defended plant species in communities. However, many studies have also demonstrated that intensive long-term herbivory does not lead to the invasion of unpalatable species into the community, and can even increase the dominance of highly palatable species. Our review indicates that high levels of nutrient inputs or recycling and an intermittent temporal pattern of herbivory (often due to migration) are key factors increasing the regrowth capacity of palatable species and hence maintaining their dominance in plant communities supporting abundant herbivores. Key factors limiting ungulate foraging selectivity, again limiting herbivore-induced dominance of slow-growing, unpalatable species, include herding behavior, early growing season and postfire herbivory, asynchronous phenology of palatable versus unpalatable species, and low relative abundance of unpalatable species. Our review indicates differences among ecosystems in the role played by ungulate herbivory result from the relative strength of these factors enhancing plant tolerance to herbivory and limiting foraging selectivity. Anthropogenic changes in these factors (e.g., alteration of migration patterns) therefore have the potential to significantly alter the effects of ungulates on plant communities and ecosystem processes.
889 citations
"Differential herbivory tolerance of..." refers background in this paper
...Plants with higher nutrient requirements or growth rate are most likely vulnerable to foliage losses (Lauda et al. 1990; Augustine and McNaughton 1998)....
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...Based on these observations, many scientists have argued that the effect of herbivory should be related to its differential impact on competing species and may in fact be independent of the absolute amount of damage inflicted (Anderson and Briske 1995; Augustine and McNaughton 1998)....
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