Hundreds of wetlands comprising thousands of hectares have been restored in the Midwestern United States. In nearly all cases, restoration consisted of simply restoring wetland hydrology. For this ...reason, the success of these restorations relies on natural colonization. We compared the structure and composition of the vegetation in two types of wetlands: 10 natural wetlands and 17 five-to-seven-year-old restored wetlands. The overall vegetative composition of restored wetlands was different from that of natural wetlands. Restored wetland flora was formed from a subset of species found in natural wetlands. The species restricted to natural wetlands tended to be native perennials and were evenly represented along the elevational gradient. The few species that were restricted to restored wetlands were largely mudflat annuals whose presence is more indicative of the presence of more unvegetated habitat in restored wetlands than of the presence of a distinctive restored wetlands flora. In addition, restored wetlands had lower vegetative cover and species richness than natural wetlands. Both wetland types had similar numbers of exotic species at the whole wetland (4.4 species per wetland) and quadrat scale (1.5 species m2), and dominance of exotics increased with elevation. The lower species richness, greater compositional variability, and lack of a distinctive flora support the hypothesis that dispersal limitation is the primary cause of the differences between the vegetation in restored and natural wetlands.
Numerous studies show that increasing species richness leads to higher ecosystem productivity. This effect is often attributed to more efficient portioning of multiple resources in communities with ...higher numbers of competing species, indicating the role of resource supply and stoichiometry for biodiversity–ecosystem functioning relationships. Here, we merged theory on ecological stoichiometry with a framework of biodiversity – ecosystem functioning to understand how resource use transfers into primary production. We applied a structural equation model to define patterns of diversity–productivity relationships with respect to available resources. Meta-analysis was used to summarize the findings across ecosystem types ranging from aquatic ecosystems to grasslands and forests. As hypothesized, resource supply increased realized productivity and richness, but we found significant differences between ecosystems and study types. Increased richness was associated with increased productivity, although this effect was not seen in experiments. More even communities had lower productivity, indicating that biomass production is often maintained by a few dominant species, and reduced dominance generally reduced ecosystem productivity. This synthesis, which integrates observational and experimental studies in a variety of ecosystems and geographical regions, exposes common patterns and differences in biodiversity-functioning relationships, and increases the mechanistic understanding of changes in ecosystems productivity.
LETTER Elser, James J; Bracken, Matthew ES; Cleland, Elsa E ...
Ecology letters,
12/2007, Volume:
10, Issue:
12
Journal Article
Peer reviewed
The cycles of the key nutrient elements nitrogen (N) and phosphorus (P) have been massively altered by anthropogenic activities. Thus, it is essential to understand how photosynthetic production ...across diverse ecosystems is, or is not, limited by N and P. Via a large-scale meta-analysis of experimental enrichments, we show that P limitation is equally strong across these major habitats and that N and P limitation are equivalent within both terrestrial and freshwater systems. Furthermore, simultaneous N and P enrichment produces strongly positive synergistic responses in all three environments. Thus, contrary to some prevailing paradigms, freshwater, marine and terrestrial ecosystems are surprisingly similar in terms of N and P limitation. PUBLICATION ABSTRACT
REVIEWS AND SYNTHESIS Mitchell, Charles E; Agrawal, Anurag A; Bever, James D ...
Ecology letters,
06/2006, Volume:
9, Issue:
6
Journal Article
Peer reviewed
Introduced plant populations lose interactions with enemies, mutualists and competitors from their native ranges, and gain interactions with new species, under new abiotic conditions. From a ...biogeographical perspective, differences in the assemblage of interacting species, as well as in abiotic conditions, may explain the demographic success of the introduced plant populations relative to conspecifics in their native range. Within invaded communities, the new interactions and conditions experienced by the invader may influence both its demographic success and its effects on native biodiversity. Here, we examine indirect effects involving enemies, mutualists and competitors of introduced plants, and effects of abiotic conditions on biotic interactions. We then synthesize ideas building on Darwin's idea that the kinds of new interactions gained by an introduced population will depend on its relatedness to native populations. This yields a heuristic framework to explain how biotic interactions and abiotic conditions influence invader success. We conclude that species introductions generally alter plants' interactions with enemies, mutualists and competitors, and that there is increasing evidence that these altered interactions jointly influence the success of introduced populations. PUBLICATION ABSTRACT
The loss of biodiversity in communities can degrade ecosystem services including productivity, stability, resilience and disease regulation. While high species richness has been often correlated with ...reduced infection and transmission risk, multiple interacting mechanisms could underlie this dilution effect. The effects of biodiversity on disease prevalence can depend on both the species loss order in community disassembly and the traits of species left in low richness communities. If host communities decay to a predictable subset of hosts in low richness communities, infection risk by generalist, vector-borne parasites may be elevated because the remaining hosts are highly susceptible as well as highly competent to transmit parasites to vectors and/or to support vector reproduction.Using grassland communities along the US West Coast as our model system, we measured the distribution and local abundance (% cover) of grass species among eleven sites across a latitudinal gradient of 15 degrees and 2000 kilometers. At each site, we monitored the prevalence of a group of generalists aphid-vectored pathogens, the Barley and Cereal yellow dwarf viruses (B/CYDVs), using two widespread grass species as sentinel hosts (Elymus glaucus and Bromus hordeaceus). We assessed in controlled conditions the ability of twenty common grass hosts to support i) viral infection after inoculation of a BYDV-PAV isolate, ii) secondary infection of new hosts and iii) reproduction of the aphid vector Rhopalosiphum padi. Finally, using a reduced set of six grass hosts, we quantified the reproductive rate of three aphid vectors of B/CYDVs (R. padi, R.maidis and Sitobion avenae), in field and/or lab experimental settings. Using these data, we show that the change in plant community composition due to biodiversity loss is associated with an altered overall competence of host species assemblages to sustain the reproduction and transmission of infectious agents, as well as the reproduction of their aphid vectors.
The loss of biodiversity in communities can degrade ecosystem services including productivity, stability, resilience and disease regulation. While high species richness has been often correlated with ...reduced infection and transmission risk, multiple interacting mechanisms could underlie this dilution effect. The effects of biodiversity on disease prevalence can depend on both the species loss order in community disassembly and the traits of species left in low richness communities. If host communities decay to a predictable subset of hosts in low richness communities, infection risk by generalist, vector-borne parasites may be elevated because the remaining hosts are highly susceptible as well as highly competent to transmit parasites to vectors and/or to support vector reproduction.Using grassland communities along the US West Coast as our model system, we measured the distribution and local abundance (% cover) of grass species among eleven sites across a latitudinal gradient of 15 degrees and 2000 kilometers. At each site, we monitored the prevalence of a group of generalists aphid-vectored pathogens, the Barley and Cereal yellow dwarf viruses (B/CYDVs), using two widespread grass species as sentinel hosts (Elymus glaucus and Bromus hordeaceus). We assessed in controlled conditions the ability of twenty common grass hosts to support i) viral infection after inoculation of a BYDV-PAV isolate, ii) secondary infection of new hosts and iii) reproduction of the aphid vector Rhopalosiphum padi. Finally, using a reduced set of six grass hosts, we quantified the reproductive rate of three aphid vectors of B/CYDVs (R. padi, R.maidis and Sitobion avenae), in field and/or lab experimental settings. Using these data, we show that the change in plant community composition due to biodiversity loss is associated with an altered overall competence of host species assemblages to sustain the reproduction and transmission of infectious agents, as well as the reproduction of their aphid vectors.
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