Direct and indirect effects of copepod grazers on community structure.

Ecological theory and empirical research show that both direct lethal effects and indirect non-lethal effects can structure the composition of communities. While the direct effects of grazers on marine phytoplankton communities are well studied, their indirect effects are still poorly understood. Direct and indirect effects are inherently difficult to disentangle in plankton food webs.

Microbial network complexity drives non-linear shift in biodiversity-nutrient cycling in a saline urban reservoir.

Aquatic biodiversity is important in mediating ecosystem functioning, contributing to ecosystem sustainability and human wellbeing. However, how microbial network complexity affects the biodiversity-nutrient cycling relationship in saline freshwater ecosystems remains underexplored. Using high-resolution time-series data, we examined the relationships between microeukaryotic-bacterial community network complexity, biodiversity and multi-nutrient cycling in an urban reservoir undergoing a freshwater salinization-desalinization cycle.

We should not necessarily expect positive relationships between biodiversity and ecosystem functioning in observational field data.

Our current, empirical understanding of the relationship between biodiversity and ecosystem function is based on two information sources. First, controlled experiments which show generally positive relationships. Second, observational field data which show variable relationships.

Large seasonal and spatial variation in nano- and microphytoplankton diversity along a Baltic Sea-North Sea salinity gradient.

Aquatic phytoplankton experience large fluctuations in environmental conditions during seasonal succession and across salinity gradients, but the impact of this variation on their diversity is poorly understood. We examined spatio-temporal variation in nano- and microphytoplankton (> 2 µm) community structure using almost two decades of light-microscope based monitoring data. The dataset encompasses 19 stations that span a salinity gradient from 2.

Habitat diversity and type govern potential nitrogen loss by denitrification in coastal sediments and differences in ecosystem-level diversities of disparate N2O reducing communities.

In coastal sediments, excess nitrogen is removed primarily by denitrification. However, losses in habitat diversity may reduce the functional diversity of microbial communities that drive this important filter function. We examined how habitat type and habitat diversity affects denitrification and the abundance and diversity of denitrifying and N2O reducing communities in illuminated shallow-water sediments.

How do trees respond to species mixing in experimental compared to observational studies?

For decades, ecologists have investigated the effects of tree species diversity on tree productivity at different scales and with different approaches ranging from observational to experimental study designs. Using data from five European national forest inventories (16,773 plots), six tree species diversity experiments (584 plots), and six networks of comparative plots (169 plots), we tested whether tree species growth responses to species mixing are consistent and therefore transferrable between those different research approaches. Our results confirm the general positive effect of tree species mixing on species growth (16% on average) but we found no consistency in species-specific responses to mixing between any of the three approaches, even after restricting comparisons to only those plots that shared similar mixtures compositions and forest types.

Levels of forest ecosystem services depend on specific mixtures of commercial tree species.

Global and local ecosystem change resulting in diversity loss has motivated efforts to understand relationships between species diversity and ecosystem services. However, it is unclear how such a general understanding can inform policies for the management of ecosystem services in production systems, because these systems are primarily used for food or fibre, and are rarely managed for the conservation of species diversity. Here, using data from a nationwide forest inventory covering an area of 230,000 km, we show that relative abundances of commercial tree species in mixed stands strongly influence the potential to provide ecosystem services.

Continental mapping of forest ecosystem functions reveals a high but unrealised potential for forest multifunctionality.

Humans require multiple services from ecosystems, but it is largely unknown whether trade-offs between ecosystem functions prevent the realisation of high ecosystem multifunctionality across spatial scales. Here, we combined a comprehensive dataset (28 ecosystem functions measured on 209 forest plots) with a forest inventory dataset (105,316 plots) to extrapolate and map relationships between various ecosystem multifunctionality measures across Europe. These multifunctionality measures reflected different management objectives, related to timber production, climate regulation and biodiversity conservation/recreation.

Revisiting the biodiversity-ecosystem multifunctionality relationship.

A recent and prominent claim for the value of biodiversity is its importance for sustaining multiple ecosystem functions. The general idea is intuitively appealing: since all species are to some extent unique, each will be important for a different set of functions. Therefore, as more functions are considered, a greater diversity of species is necessary to sustain all functions simultaneously.

Habitat diversity and ecosystem multifunctionality-The importance of direct and indirect effects.

Ecosystems worldwide are facing habitat homogenization due to human activities. Although it is commonly proposed that such habitat homogenization can have negative repercussions for ecosystem functioning, this question has yet to receive explicit scientific attention. We expand on the framework for evaluating the functional consequences of biodiversity loss by scaling up from the level of species to the level of the entire habitats.

Effects of multiple dimensions of bacterial diversity on functioning, stability and multifunctionality.

Bacteria are essential for many ecosystem services but our understanding of factors controlling their functioning is incomplete. While biodiversity has been identified as an important driver of ecosystem processes in macrobiotic communities, we know much less about bacterial communities. Due to the high diversity of bacterial communities, high functional redundancy is commonly proposed as explanation for a lack of clear effects of diversity.

The influence of balanced and imbalanced resource supply on biodiversity-functioning relationship across ecosystems.

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.

Biodiversity mediates top-down control in eelgrass ecosystems: a global comparative-experimental approach.

Nutrient pollution and reduced grazing each can stimulate algal blooms as shown by numerous experiments. But because experiments rarely incorporate natural variation in environmental factors and biodiversity, conditions determining the relative strength of bottom-up and top-down forcing remain unresolved. We factorially added nutrients and reduced grazing at 15 sites across the range of the marine foundation species eelgrass (Zostera marina) to quantify how top-down and bottom-up control interact with natural gradients in biodiversity and environmental forcing.

Biodiversity enhances ecosystem multifunctionality across trophic levels and habitats.

The importance of biodiversity for the integrated functioning of ecosystems remains unclear because most evidence comes from analyses of biodiversity's effect on individual functions. Here we show that the effects of biodiversity on ecosystem function become more important as more functions are considered. We present the first systematic investigation of biodiversity's effect on ecosystem multifunctionality across multiple taxa, trophic levels and habitats using a comprehensive database of 94 manipulations of species richness.

Multiple stressors and multifunctionality: limited effects on an illuminated benthic system.

The bulk of experiments that study stressor effects on ecosystem functioning consider only individual functions one at a time, and such narrow focus may well bias our understanding of the overall impact on ecosystem functioning. We used data from six published experiments in which marine illuminated sediment systems were exposed to nutrient enrichment, toxicants, sedimentation and warming, either alone or in combination. Measured functions were primary production, community respiration, inorganic nitrogen and phosphorus fluxes, and autotrophic biomass.

Higher biodiversity is required to sustain multiple ecosystem processes across temperature regimes.

Biodiversity loss is occurring rapidly worldwide, yet it is uncertain whether few or many species are required to sustain ecosystem functioning in the face of environmental change. The importance of biodiversity might be enhanced when multiple ecosystem processes (termed multifunctionality) and environmental contexts are considered, yet no studies have quantified this explicitly to date. We measured five key processes and their combined multifunctionality at three temperatures (5, 10 and 15 °C) in freshwater aquaria containing different animal assemblages (1-4 benthic macroinvertebrate species).

Consumers mediate the effects of experimental ocean acidification and warming on primary producers.

It is well known that ocean acidification can have profound impacts on marine organisms. However, we know little about the direct and indirect effects of ocean acidification and also how these effects interact with other features of environmental change such as warming and declining consumer pressure. In this study, we tested whether the presence of consumers (invertebrate mesograzers) influenced the interactive effects of ocean acidification and warming on benthic microalgae in a seagrass community mesocosm experiment.

Higher levels of multiple ecosystem services are found in forests with more tree species.

Forests are of major importance to human society, contributing several crucial ecosystem services. Biodiversity is suggested to positively influence multiple services but evidence from natural systems at scales relevant to management is scarce. Here, across a scale of 400,000 km(2), we report that tree species richness in production forests shows positive to positively hump-shaped relationships with multiple ecosystem services.

Genetic diversity and ecosystem functioning in the face of multiple stressors.

Species diversity is important for a range of ecosystem processes and properties, including the resistance to single and multiple stressors. It has been suggested that genetic diversity may play a similar role, but empirical evidence is still relatively scarce. Here, we report the results of a microcosm experiment where four strains of the marine diatom Skeletonema marinoi were grown in monoculture and in mixture under a factorial combination of temperature and salinity stress.

A global synthesis reveals biodiversity loss as a major driver of ecosystem change.

Evidence is mounting that extinctions are altering key processes important to the productivity and sustainability of Earth's ecosystems. Further species loss will accelerate change in ecosystem processes, but it is unclear how these effects compare to the direct effects of other forms of environmental change that are both driving diversity loss and altering ecosystem function. Here we use a suite of meta-analyses of published data to show that the effects of species loss on productivity and decomposition--two processes important in all ecosystems--are of comparable magnitude to the effects of many other global environmental changes.

Experimental climate change weakens the insurance effect of biodiversity.

Ecosystems are simultaneously affected by biodiversity loss and climate change, but we know little about how these factors interact. We predicted that climate warming and CO (2) -enrichment should strengthen trophic cascades by reducing the relative efficiency of predation-resistant herbivores, if herbivore consumption rate trades off with predation resistance. This weakens the insurance effect of herbivore diversity.

Effects of total resources, resource ratios, and species richness on algal productivity and evenness at both metacommunity and local scales.

The study of the interrelationship between productivity and biodiversity is a major research field in ecology. Theory predicts that if essential resources are heterogeneously distributed across a metacommunity, single species may dominate productivity in individual metacommunity patches, but a mixture of species will maximize productivity across the whole metacommunity. It also predicts that a balanced supply of resources within local patches should favor species coexistence, whereas resource imbalance would favor the dominance of one species.

The functional role of producer diversity in ecosystems.

Over the past several decades, a rapidly expanding field of research known as biodiversity and ecosystem functioning has begun to quantify how the world's biological diversity can, as an independent variable, control ecological processes that are both essential for, and fundamental to, the functioning of ecosystems. Research in this area has often been justified on grounds that (1) loss of biological diversity ranks among the most pronounced changes to the global environment and that (2) reductions in diversity, and corresponding changes in species composition, could alter important services that ecosystems provide to humanity (e.g.