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Mechanistic Framework (mechanistic + framework)
Selected AbstractsPhenology, ontogeny and the effects of climate change on the timing of species interactionsECOLOGY LETTERS, Issue 1 2010Louie H. Yang Abstract Climate change is altering the phenology of many species and the timing of their interactions with other species, but the impacts of these phenological shifts on species interactions remain unclear. Classical approaches to the study of phenology have typically documented changes in the timing of single life-history events, while phenological shifts affect many interactions over entire life histories. In this study, we suggest an approach that integrates the phenology and ontogeny of species interactions with a fitness landscape to provide a common mechanistic framework for investigating phenological shifts. We suggest that this ontogeny,phenology landscape provides a flexible method to document changes in the relative phenologies of interacting species, examine the causes of these phenological shifts, and estimate their consequences for interacting species. Ecology Letters (2010) 13: 1,10 [source] Plant functional traits and soil carbon sequestration in contrasting biomesECOLOGY LETTERS, Issue 5 2008Gerlinde B. De Deyn Abstract Plant functional traits control a variety of terrestrial ecosystem processes, including soil carbon storage which is a key component of the global carbon cycle. Plant traits regulate net soil carbon storage by controlling carbon assimilation, its transfer and storage in belowground biomass, and its release from soil through respiration, fire and leaching. However, our mechanistic understanding of these processes is incomplete. Here, we present a mechanistic framework, based on the plant traits that drive soil carbon inputs and outputs, for understanding how alteration of vegetation composition will affect soil carbon sequestration under global changes. First, we show direct and indirect plant trait effects on soil carbon input and output through autotrophs and heterotrophs, and through modification of abiotic conditions, which need to be considered to determine the local carbon sequestration potential. Second, we explore how the composition of key plant traits and soil biota related to carbon input, release and storage prevail in different biomes across the globe, and address the biome-specific mechanisms by which plant trait composition may impact on soil carbon sequestration. We propose that a trait-based approach will help to develop strategies to preserve and promote carbon sequestration. [source] Linking the global carbon cycle to individual metabolismFUNCTIONAL ECOLOGY, Issue 2 2005A. P. ALLEN Summary 1We present a model that yields ecosystem-level predictions of the flux, storage and turnover of carbon in three important pools (autotrophs, decomposers, labile soil C) based on the constraints of body size and temperature on individual metabolic rate. 2The model predicts a 10 000-fold increase in C turnover rates moving from tree- to phytoplankton-dominated ecosystems due to the size dependence of photosynthetic rates. 3The model predicts a 16-fold increase in rates controlled by respiration (e.g. decomposition, turnover of labile soil C and microbial biomass) over the temperature range 0,30 °C due to the temperature dependence of ATP synthesis in respiratory complexes. 4The model predicts only a fourfold increase in rates controlled by photosynthesis (e.g. net primary production, litter fall, fine root turnover) over the temperature range 0,30 °C due to the temperature dependence of Rubisco carboxylation in chloroplasts. 5The difference between the temperature dependence of respiration and photosynthesis yields quantitative predictions for distinct phenomena that include acclimation of plant respiration, geographic gradients in labile C storage, and differences between the short- and long-term temperature dependence of whole-ecosystem CO2 flux. 6These four sets of model predictions were tested using global compilations of data on C flux, storage and turnover in ecosystems. 7Results support the hypothesis that the combined effects of body size and temperature on individual metabolic rate impose important constraints on the global C cycle. The model thus provides a synthetic, mechanistic framework for linking global biogeochemical cycles to cellular-, individual- and community-level processes. [source] 4-Acetoxystyrene nitroxide-mediated controlled radical polymerization: Comparison with styreneJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2010Andrew S. Cho Abstract The nitroxide-mediated controlled radical polymerization (NM-CRP) of 4-acetoxystyrene with an alkoxyamine was analyzed by a combined experimental and modeling approach. At low nitroxide concentrations, thermal initiation was significant, and control of the polydispersity was poor, as was observed previously for styrene. A continuum model based on the method of moments was used to regress the parameters for the reversible nitroxide uncoupling/coupling reactions (activation energy of uncoupling), thermal initiation (activation energy of initiation), and termination (frequency factor of recombination). The model was able to capture the molecular weight averages and the polydispersity index as a function of time and the nitroxide concentration qualitatively and quantitatively. Using this mechanistic framework, we developed kinetic Monte Carlo models that allowed the molecular weight distributions to be predicted explicitly in good agreement with experimental data. A comparison of the NM-CRP of 4-acetoxystyrene and styrene is provided to illustrate the effect of the acetoxy substituent. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] The role of genotypic diversity in determining grassland community structure under constant environmental conditionsJOURNAL OF ECOLOGY, Issue 5 2007RAJ WHITLOCK Summary 1A recent experiment varied the genetic diversity of model grassland communities under standardized soil and management conditions and at constant initial species diversity. After 5 years' growth, genetically diverse communities retained more species diversity and became more similar in species composition than genetically impoverished communities. 2Here we present the results of further investigation within this experimental system. We proposed that two mechanisms , the first invoking genetically determined and constant differences in plant phenotypes and the second invoking genotype,environment interactions , could each underpin these results. This mechanistic framework was used as a tool to interpret our findings. 3We used inter-simple sequence repeat (ISSR) DNA markers to confirm which of the individuals of six study species initially included in the model communities were unique genotypes. We then used the molecular markers to assess the survival and abundance of each genotype at the end of the 5-year experimental period. 4The DNA marker data were used to create, for the first time, a genotype abundance hierarchy describing the structure of a community at the level of genotypes. This abundance hierarchy revealed wide variation in the abundance of genotypes within species, and large overlaps in the performance of the genotypes of different species. 5Each genotype achieved a consistent level of abundance within genetically diverse communities, which differed from that attained by other genotypes of the same species. The abundance hierarchy of genotypes within species also showed consistency across communities differing in their initial level of genetic diversity, such that species abundance in genetically impoverished communities could be predicted, in part, by genotypic identity. 6Three species (including two canopy-dominants) experienced shifts in their community-level genotype abundance hierarchies that were consistent with an increased influence of genotype,environment interactions in genetically impoverished communities. 7Our results indicate that under relatively constant environmental conditions the species abundance structure of plant communities can in part be predicted from the genotypic composition of their component populations. Genotype,environment interactions also appear to shape the structure of communities under such conditions, although further experiments are needed to clarify the magnitude and mechanism of these effects. [source] | ||||||||||