Author
Marcelo S. Moretti
Other affiliations: Swiss Federal Institute of Aquatic Science and Technology
Bio: Marcelo S. Moretti is an academic researcher from Universidade Federal de Minas Gerais. The author has contributed to research in topics: Riparian zone & Plant litter. The author has an hindex of 16, co-authored 36 publications receiving 1395 citations. Previous affiliations of Marcelo S. Moretti include Swiss Federal Institute of Aquatic Science and Technology.
Topics: Riparian zone, Plant litter, Litter, Ecosystem, Biodiversity
Papers
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Spanish National Research Council1, James Cook University2, ETH Zurich3, Swiss Federal Institute of Aquatic Science and Technology4, University of Tasmania5, University of Coimbra6, University of Hong Kong7, University of New England (Australia)8, Universidade Federal de Minas Gerais9, University of Toulouse10, Ecolab11, University of Toronto12, National University of Comahue13, Monash University14, University of Concepción15, Cornell University16, University of Puerto Rico17, University of Yamanashi18, Egerton University19, University of Panama20, Instituto Conmemorativo Gorgas de Estudios de la Salud21
TL;DR: It is found that climate warming will likely hasten microbial litter decomposition and produce an equivalent decline in detritivore-mediated decomposition rates, which implies consequences for global biogeochemistry and a possible positive climate feedback.
Abstract: The decomposition of plant litter is one of the most important ecosystem processes in the biosphere and is particularly sensitive to climate warming. Aquatic ecosystems are well suited to studying warming effects on decomposition because the otherwise confounding influence of moisture is constant. By using a latitudinal temperature gradient in an unprecedented global experiment in streams, we found that climate warming will likely hasten microbial litter decomposition and produce an equivalent decline in detritivore-mediated decomposition rates. As a result, overall decomposition rates should remain unchanged. Nevertheless, the process would be profoundly altered, because the shift in importance from detritivores to microbes in warm climates would likely increase CO2 production and decrease the generation and sequestration of recalcitrant organic particles. In view of recent estimates showing that inland waters are a significant component of the global carbon cycle, this implies consequences for global biogeochemistry and a possible positive climate feedback.
280 citations
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James Cook University1, African Institute for Mathematical Sciences2, Stellenbosch University3, Leibniz Institute for Neurobiology4, Technical University of Berlin5, University of the Basque Country6, University of California, Santa Barbara7, University of Coimbra8, University of Michigan9, National University of Comahue10, Manonmaniam Sundaranar University11, University of Tasmania12, University of New England (United States)13, École Polytechnique Fédérale de Lausanne14, Universidade Federal de Minas Gerais15, Massey University16, University of Hong Kong17, University of San Francisco18, University of Concepción19, Cornell University20, University of Brasília21, University of Toronto22, University of Yamanashi23, Monash University Malaysia Campus24, Egerton University25, National Autonomous University of Mexico26, University of Georgia27, University of Puerto Rico28, University of Zulia29
TL;DR: A global-scale study of litter breakdown in streams to compare the roles of biotic, climatic and other environmental factors on breakdown rates revealed that breakdown of alder was driven by climate, with some influence of pH, whereas variation in breakdown of litter mixtures was explained mainly by litter quality and PD.
Abstract: Plant litter breakdown is a key ecological process in terres- trial and freshwater ecosystems. Streams and rivers, in particular, contribute substantially to global carbon fluxes. However, there is little information available on the relative roles of different drivers of plant litter break- down in fresh waters, particularly at large scales. We present a global-scale study of litter breakdown in streams to compare the roles of biotic, climatic and other environ- mental factors on breakdown rates. We conducted an experiment in 24 streams encompassing latitudes from 47.88 N to 42.88 S, using litter mixtures of local species dif- fering in quality and phylogenetic diversity (PD), and alder (Alnus glutinosa) to control for variation in litter traits. Our models revealed that breakdown of alder was driven by climate, with some influence of pH, whereas variation in breakdown of litter mixtures was explained mainly by litter quality and PD. Effects of litter quality and PD and stream pH were more positive at higher temp- eratures, indicating that different mechanisms may operate at different latitudes. These results reflect global variability caused by multiple factors, but unexplained variance points to the need for expanded global-scale comparisons.
182 citations
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Spanish National Research Council1, James Cook University2, University of Hong Kong3, University of Coimbra4, ETH Zurich5, Swiss Federal Institute of Aquatic Science and Technology6, National University of Comahue7, Monash University8, University of New England (Australia)9, Universidade Federal de Minas Gerais10, Ecolab11, University of Toulouse12, University of Puerto Rico13, University of Toronto14, University of Valle15, Universidad San Francisco de Quito16, Instituto Conmemorativo Gorgas de Estudios de la Salud17, University of Panama18, University of Georgia19
TL;DR: The authors' findings markedly contrast with global trends of diversity for most taxa, and with the general rule of higher consumer diversity at higher levels of resource diversity, and highlight the emerging role of temperature in understanding global patterns of diversity, which is of great relevance in the face of projected global warming.
Abstract: Most hypotheses explaining the general gradient of higher diversity toward the equator are implicit or explicit about greater species packing in the tropics. However, global patterns of diversity within guilds, including trophic guilds (i.e., groups of organisms that use similar food resources), are poorly known. We explored global diversity patterns of a key trophic guild in stream ecosystems, the detritivore shredders. This was motivated by the fundamental ecological role of shredders as decomposers of leaf litter and by some records pointing to low shredder diversity and abundance in the tropics, which contrasts with diversity patterns of most major taxa for which broad-scale latitudinal patterns haven been examined. Given this evidence, we hypothesized that shredders are more abundant and diverse in temperate than in tropical streams, and that this pattern is related to the higher temperatures and lower availability of high-quality leaf litter in the tropics. Our comprehensive global survey (129 stream sites from 14 regions on six continents) corroborated the expected latitudinal pattern and showed that shredder distribution (abundance, diversity and assemblage composition) was explained by a combination of factors, including water temperature (some taxa were restricted to cool waters) and biogeography (some taxa were more diverse in particular biogeographic realms). In contrast to our hypothesis, shredder diversity was unrelated to leaf toughness, but it was inversely related to litter diversity. Our findings markedly contrast with global trends of diversity for most taxa, and with the general rule of higher consumer diversity at higher levels of resource diversity. Moreover, they highlight the emerging role of temperature in understanding global patterns of diversity, which is of great relevance in the face of projected global warming.
172 citations
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162 citations
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James Cook University1, University of Hong Kong2, Swiss Federal Institute of Aquatic Science and Technology3, Ecolab4, University of Toulouse5, Monash University Malaysia Campus6, Universidad San Francisco de Quito7, University of Panama8, University of Maryland, Baltimore County9, Hobart Corporation10
TL;DR: In this paper, the authors used linear regression to examine the latitudinal variation in shredder diversity at different spatial scales: alpha (a), gamma (g) and beta (b) diversity.
Abstract: Aim. We tested the hypothesis that shredder detritivores, a key trophic guild in stream ecosystems, are more diverse at higher latitudes, which has important ecological implications in the face of potential biodiversity losses that are expected as a result of climate change. We also explored the dependence of local shredder diversity on the regional species pool across latitudes, and examined the influence of environ- mental factors on shredder diversity. Location: World-wide (156 sites from 17 regions located in all inhabited continents at latitudes ranging from 67° N to 41° S). Methods: We used linear regression to examine the latitudinal variation in shredder diversity at different spatial scales: alpha (a), gamma (g) and beta (b) diversity. We also explored the effect of g-diversity on a-diversity across latitudes with regression analysis, and the possible influence of local environmental factors on shredder diversity with simple correlations. Results: Alpha diversity increased with latitude, while g- and b-diversity showed no clear latitudinal pattern. Temperate sites showed a linear relationship between g- and a-diversity; in contrast, tropical sites showed evidence of local species saturation, which may explain why the latitudinal gradient in a-diversity is not accompanied by a gradient in g-diversity. Alpha diversity was related to several local habitat characteristics, but g- and b-diversity were not related to any of the environmental factors measured. Main conclusions: Our results indicate that global patterns of shredder diversity are complex and depend on spatial scale. However, we can draw several conclusions that have important ecological implications. Alpha diversity is limited at tropical sites by local factors, implying a higher risk of loss of key species or the whole shredder guild (the latter implying the loss of trophic diversity). Even if regional species pools are not particularly species poor in the tropics, colonization from adjacent sites may be limited. Moreover, many shredder species belong to cool-adapted taxa that may be close to their thermal maxima in the tropics, which makes them more vulnerable to climate warming. Our results suggest that tropical streams require specific scientific attention and conservation efforts to prevent loss of shredder biodiversity and serious alteration of ecosystem processes.
121 citations
Cited by
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TL;DR: In this article, the authors present a document, redatto, voted and pubblicato by the Ipcc -Comitato intergovernativo sui cambiamenti climatici - illustra la sintesi delle ricerche svolte su questo tema rilevante.
Abstract: Cause, conseguenze e strategie di mitigazione Proponiamo il primo di una serie di articoli in cui affronteremo l’attuale problema dei mutamenti climatici. Presentiamo il documento redatto, votato e pubblicato dall’Ipcc - Comitato intergovernativo sui cambiamenti climatici - che illustra la sintesi delle ricerche svolte su questo tema rilevante.
4,187 citations
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University of Coimbra1, University of Brasília2, University of the Basque Country3, University of California, Santa Barbara4, University of Vigo5, Leibniz Association6, Technical University of Berlin7, Swedish University of Agricultural Sciences8, National Scientific and Technical Research Council9, University of Tasmania10, Universidade Federal de Minas Gerais11, University of Toulouse12, Georgia Southern University13, University of Hong Kong14, Universidad San Francisco de Quito15, University of Concepción16, Cornell University17, Polish Academy of Sciences18, University of Tromsø19, Umeå University20, University of Toronto21, University of Yamanashi22, Egerton University23, University of Georgia24, University of Puerto Rico, Río Piedras25, University of Maryland, Baltimore County26, Monash University27, James Cook University28
TL;DR: It is hypothesized that litter quality would increase with latitude (despite variation within regions) and traits would be correlated to produce ‘syndromes’ resulting from phylogeny and environmental variation, and it is found lower litter quality and higher nitrogen:phosphorus ratios in the tropics.
Abstract: Plant litter represents a major basal resource in streams, where its decomposition is partly regulated by litter traits. Litter-trait variation may determine the latitudinal gradient in decomposition in streams, which is mainly microbial in the tropics and detritivore-mediated at high latitudes. However, this hypothesis remains untested, as we lack information on large-scale trait variation for riparian litter. Variation cannot easily be inferred from existing leaf-trait databases, since nutrient resorption can cause traits of litter and green leaves to diverge. Here we present the first global-scale assessment of riparian litter quality by determining latitudinal variation (spanning 107°) in litter traits (nutrient concentrations; physical and chemical defences) of 151 species from 24 regions and their relationships with environmental factors and phylogeny. We hypothesized that litter quality would increase with latitude (despite variation within regions) and traits would be correlated to produce ‘syndromes’ resulting from phylogeny and environmental variation. We found lower litter quality and higher nitrogen:phosphorus ratios in the tropics. Traits were linked but showed no phylogenetic signal, suggesting that syndromes were environmentally determined. Poorer litter quality and greater phosphorus limitation towards the equator may restrict detritivore-mediated decomposition, contributing to the predominance of microbial decomposers in tropical streams.
616 citations
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Queen Mary University of London1, National University of Ireland2, University of Coimbra3, University of Toulouse4, Ecolab5, Umeå University6, Swiss Federal Institute of Aquatic Science and Technology7, ETH Zurich8, University of Rochester9, Manchester Metropolitan University10, University of the Basque Country11, Polish Academy of Sciences12, Kristianstad University College13, University of Bucharest14
TL;DR: Dramatically slowed breakdown at both extremes of the gradient indicated strong nutrient limitation in unaffected systems, potential for strong stimulation in moderately altered systems, and inhibition in highly polluted streams, emphasizing the need to complement established structural approaches with functional measures for assessing ecosystem health.
Abstract: Excessive nutrient loading is a major threat to aquatic ecosystems worldwide that leads to profound changes in aquatic biodiversity and biogeochemical processes. Systematic quantitative assessment of functional ecosystem measures for river networks is, however, lacking, especially at continental scales. Here, we narrow this gap by means of a pan-European field experiment on a fundamental ecosystem process—leaf-litter breakdown—in 100 streams across a greater than 1000-fold nutrient gradient. Dramatically slowed breakdown at both extremes of the gradient indicated strong nutrient limitation in unaffected systems, potential for strong stimulation in moderately altered systems, and inhibition in highly polluted streams. This large-scale response pattern emphasizes the need to complement established structural approaches (such as water chemistry, hydrogeomorphology, and biological diversity metrics) with functional measures (such as litter-breakdown rate, whole-system metabolism, and nutrient spiraling) for assessing ecosystem health.
553 citations
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TL;DR: In this article, the authors evaluated how congruent three commonly used metrics of diversity were among taxa for six groups of freshwater species and found that broad-scale patterns of species richness, threatened-species richness and endemism lack congruence among these metrics.
Abstract: Aim Global-scale studies are required to identify broad-scale patterns in the distributions of species, to evaluate the processes that determine diversity and to determine how similar or different these patterns and processes are among different groups of freshwater species. Broad-scale patterns of spatial variation in species distribution are central to many fundamental questions in macroecology and conservation biology. We aimed to evaluate how congruent three commonly used metrics of diversity were among taxa for six groups of freshwater species. Location Global. Methods We compiled geographical range data on 7083 freshwater species of mammals, amphibians, reptiles, fishes, crabs and crayfish to evaluate how species richness, richness of threatened species and endemism are distributed across freshwater ecosystems. We evaluated how congruent these measures of diversity were among taxa at a global level for a grid cell size of just under 1°. Results We showed that although the risk of extinction faced by freshwater decapods is quite similar to that of freshwater vertebrates, there is a distinct lack of spatial congruence in geographical range between different taxonomic groups at this spatial scale, and a lack of congruence among three commonly used metrics of biodiversity. The risk of extinction for freshwater species was consistently higher than for their terrestrial counterparts. Main conclusions We demonstrate that broad-scale patterns of species richness, threatened-species richness and endemism lack congruence among the six freshwater taxonomic groups examined. Invertebrate species are seldom taken into account in conservation planning. Our study suggests that both the metric of biodiversity and the identity of the taxa on which conservation decisions are based require careful consideration. As geographical range information becomes available for further sets of species, further testing will be warranted into the extent to which geographical variation in the richness of these six freshwater groups reflects broader patterns of biodiversity in fresh water.
468 citations
01 Jan 2009
TL;DR: In this paper, the authors used soil microcosms to show that functional dissimilarity among detritivorous species, not species number, drives community compositional effects on leaf litter mass loss and soil respiration, two key soil ecosystem processes.
Abstract: The loss of biodiversity can have significant impacts on ecosystem functioning, but the mechanisms involved lack empirical confirmation. Using soil microcosms, we show experimentally that functional dissimilarity among detritivorous species, not species number, drives community compositional effects on leaf litter mass loss and soil respiration, two key soil ecosystem processes. These experiments confirm theoretical predictions that biodiversity effects on ecosystem functioning can be predicted by the degree of functional differences among species.
444 citations