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Neonicotinoid seed dressings have caused concern world-wide. We use large field experiments to assess the effects of neonicotinoid-treated crops on three bee species across three countries (Hungary, Germany, and the United Kingdom). Winter-sown oilseed rape was grown commercially with either seed coatings containing neonicotinoids (clothianidin or thiamethoxam) or no seed treatment (control). For honey bees, we found both negative (Hungary and United Kingdom) and positive (Germany) effects during crop flowering. In Hungary, negative effects on honey bees (associated with clothianidin) persisted over winter and resulted in smaller colonies in the following spring (24% declines). In wild bees (Bombus terrestris and Osmia bicornis), reproduction was negatively correlated with neonicotinoid residues. These findings point to neonicotinoids causing a reduced capacity of bee species to establish new populations in the year following exposure.

Neonicotinoid seed dressings have caused concern world-wide. We use large field experiments to assess the effects of neonicotinoid-treated crops on three bee species across three countries (Hungary, Germany, and the United Kingdom). Winter-sown oilseed rape was grown commercially with either seed coatings containing neonicotinoids (clothianidin or thiamethoxam) or no seed treatment (control). For honey bees, we found both negative (Hungary and United Kingdom) and positive (Germany) effects during crop flowering. In Hungary, negative effects on honey bees (associated with clothianidin) persisted over winter and resulted in smaller colonies in the following spring (24% declines). In wild bees (Bombus terrestris and Osmia bicornis), reproduction was negatively correlated with neonicotinoid residues. These findings point to neonicotinoids causing a reduced capacity of bee species to establish new populations in the year following exposure.

Concern over reported honeybee (Apis mellifera spp.) losses has highlighted chemical exposure as a risk. Current laboratory oral toxicity tests in A. mellifera spp. use short-term, maximum 96 hour, exposures which may not necessarily account for chronic and cumulative toxicity. Here, we use extended 240 hour (10 day) exposures to examine seven agrochemicals and trace environmental pollutant toxicities for adult honeybees. Data were used to parameterise a dynamic energy budget model (DEBtox) to further examine potential survival effects up to 30 day and 90 day summer and winter worker lifespans. Honeybees were most sensitive to insecticides (clothianidin > dimethoate ≫ tau-fluvalinate), then trace metals/metalloids (cadmium, arsenic), followed by the fungicide propiconazole and herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). LC50s calculated from DEBtox parameters indicated a 27 fold change comparing exposure from 48 to 720 hours (summer worker lifespan) for cadmium, as the most time-dependent chemical as driven by slow toxicokinetics. Clothianidin and dimethoate exhibited more rapid toxicokinetics with 48 to 720 hour LC50s changes of <4 fold. As effects from long-term exposure may exceed those measured in short-term tests, future regulatory tests should extend to 96 hours as standard, with extension to 240 hour exposures further improving realism.

Concern over reported honeybee (Apis mellifera spp.) losses has highlighted chemical exposure as a risk. Current laboratory oral toxicity tests in A. mellifera spp. use short-term, maximum 96 hour, exposures which may not necessarily account for chronic and cumulative toxicity. Here, we use extended 240 hour (10 day) exposures to examine seven agrochemicals and trace environmental pollutant toxicities for adult honeybees. Data were used to parameterise a dynamic energy budget model (DEBtox) to further examine potential survival effects up to 30 day and 90 day summer and winter worker lifespans. Honeybees were most sensitive to insecticides (clothianidin > dimethoate ≫ tau-fluvalinate), then trace metals/metalloids (cadmium, arsenic), followed by the fungicide propiconazole and herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). LC50s calculated from DEBtox parameters indicated a 27 fold change comparing exposure from 48 to 720 hours (summer worker lifespan) for cadmium, as the most time-dependent chemical as driven by slow toxicokinetics. Clothianidin and dimethoate exhibited more rapid toxicokinetics with 48 to 720 hour LC50s changes of <4 fold. As effects from long-term exposure may exceed those measured in short-term tests, future regulatory tests should extend to 96 hours as standard, with extension to 240 hour exposures further improving realism.

Understanding patterns in predator:prey systems and the mechanisms that underlie trophic interactions provides a basis for predicting community structure and the delivery of natural pest control services. The functional response of predators to prey density is a fundamental measure of interaction strength and its characterisation is essential to understanding these processes. We used mesocosm experiments to quantify the functional responses of five ground beetle species that represent common generalist predators of north-west European arable agriculture. We investigated two mechanisms predicted to be key drivers of trophic interactions in natural communities: predator:prey body size ratio and multiple predator effects. Our results show regularities in foraging patterns characteristic of similarly sized predators. Ground beetle attack rates increased and handling times decreased as the predator:prey body-mass ratio rose. Multiple predator effects on total prey consumption rates were sensitive to the identity of the interacting species but not prey density. The extent of interspecific interactions may be a result of differences in body mass between competing beetle species. Overall these results add to the growing evidence for the importance of size in determining trophic interactions and suggest that body mass could offer a focus on which to base the management of natural enemy assemblages.

Agricultural expansion and intensification have been linked with losses of biodiversity and disruption of key ecosystem services in farmed landscapes. A number of mitigation and adaptation strategies e.g. agri-environment schemes, have been implemented to counter these declines but their effectiveness has been questioned by conservationists as well as policy makers. A key concern is the lack of knowledge about how conservation efforts might best be directed; especially in terms of aligning the scale and type of implementation in different landscapes with the niche requirements and dynamics of different species and taxa. Here we focus on how the landscape context of farmed systems at different spatial scales determines the abundance of habitat generalist and specialist butterfly and moth species in southern England. We used butterfly data from 20 UK Butterfly Monitoring Scheme sites, supplemented with moth data from a light trap survey of 11 sites, in southern England where the predominant habitat type sampled is lowland calcareous grassland. Our results show that larger areas of semi-natural grassland generally support larger numbers and a greater species richness of butterflies and moths, but that the composition of the Lepidoptera fauna changes with habitat size depending on the diversity of habitats in the landscape, particularly at the larger spatial scale. Larger areas of grassland in less diverse landscapes result in a proportionally greater number and diversity of habitat specialists, whilst habitat diversity is important in maintaining numbers and diversity of more generalist wider countryside species. Large areas of single habitat types may only be economically maintained at the expense of habitat diversity. Whilst these sites may be important in promoting abundance and diversity of selected specialist species, they may be prone to lower overall species richness. This has implications for improving the design and implementation of agri-environment schemes a

Understanding patterns in predator:prey systems and the mechanisms that underlie trophic interactions provides a basis for predicting community structure and the delivery of natural pest control services. The functional response of predators to prey density is a fundamental measure of interaction strength and its characterisation is essential to understanding these processes. We used mesocosm experiments to quantify the functional responses of five ground beetle species that represent common generalist predators of north-west European arable agriculture. We investigated two mechanisms predicted to be key drivers of trophic interactions in natural communities: predator:prey body size ratio and multiple predator effects. Our results show regularities in foraging patterns characteristic of similarly sized predators. Ground beetle attack rates increased and handling times decreased as the predator:prey body-mass ratio rose. Multiple predator effects on total prey consumption rates were sensitive to the identity of the interacting species but not prey density. The extent of interspecific interactions may be a result of differences in body mass between competing beetle species. Overall these results add to the growing evidence for the importance of size in determining trophic interactions and suggest that body mass could offer a focus on which to base the management of natural enemy assemblages.

Agricultural expansion and intensification have been linked with losses of biodiversity and disruption of key ecosystem services in farmed landscapes. A number of mitigation and adaptation strategies e.g. agri-environment schemes, have been implemented to counter these declines but their effectiveness has been questioned by conservationists as well as policy makers. A key concern is the lack of knowledge about how conservation efforts might best be directed; especially in terms of aligning the scale and type of implementation in different landscapes with the niche requirements and dynamics of different species and taxa. Here we focus on how the landscape context of farmed systems at different spatial scales determines the abundance of habitat generalist and specialist butterfly and moth species in southern England. We used butterfly data from 20 UK Butterfly Monitoring Scheme sites, supplemented with moth data from a light trap survey of 11 sites, in southern England where the predominant habitat type sampled is lowland calcareous grassland. Our results show that larger areas of semi-natural grassland generally support larger numbers and a greater species richness of butterflies and moths, but that the composition of the Lepidoptera fauna changes with habitat size depending on the diversity of habitats in the landscape, particularly at the larger spatial scale. Larger areas of grassland in less diverse landscapes result in a proportionally greater number and diversity of habitat specialists, whilst habitat diversity is important in maintaining numbers and diversity of more generalist wider countryside species. Large areas of single habitat types may only be economically maintained at the expense of habitat diversity. Whilst these sites may be important in promoting abundance and diversity of selected specialist species, they may be prone to lower overall species richness. This has implications for improving the design and implementation of agri-environment schemes a

Restoration of semi-natural calcareous grassland needs to overcome dispersal limitation and microsite limitation. The effectiveness of sowing a mix of ten target species in combination with various pre-sowing disturbance techniques and post-establishment management regimes in overcoming these limitations, and in promoting vegetation change towards the restoration target was tested in a field experiment. Our results illustrate the importance of bare ground for introducing target species of calcareous grassland into species-poor grassland, and the slowness of colonisation by additional target species from outside even when a site is situated close to high-quality grassland that could serve as source for additional target species.

Restoration of semi-natural calcareous grassland needs to overcome dispersal limitation and microsite limitation. The effectiveness of sowing a mix of ten target species in combination with various pre-sowing disturbance techniques and post-establishment management regimes in overcoming these limitations, and in promoting vegetation change towards the restoration target was tested in a field experiment. Our results illustrate the importance of bare ground for introducing target species of calcareous grassland into species-poor grassland, and the slowness of colonisation by additional target species from outside even when a site is situated close to high-quality grassland that could serve as source for additional target species.

The Hillesden experiment has proved to be a valuable, practical test of the effectiveness of the Entry Level Stewardship scheme for a range of taxa at the farm-scale. The experiment was a large scale, randomised block experiment with three treatments applied to replicated land areas of c. 50-60 ha: i) Cross compliance (CC, conventional intensive arable management subject to the EU rules of cross compliance), ii) Entry Level Stewardship (ELS, a small suite of options selected to replicate a ‘standard’ agreement comprising 1% area out of production), iii) Entry Level Stewardship Extra (ELS X, a more extensive selection of options targeted at farmland wildlife of conservation interest comprising 5% area out of production). The results show that over a five year period (2006-2011) the effects on (i) habitat quality and food resources, and (ii) the abundance, diversity and population dynamics of some key farmland taxa were significantly enhanced by both targeted local management and enhancements at the landscape scale. However there were clear effects of scale on the responses of different taxa (see Table 1.1). Mobile species like bumblebees, moths, birds and small mammals were more subject to the effects of wider landscape context and showed a net response to the whole farm manipulation. The response of other taxa e.g. plants and some invertebrate groups, were more influenced by local environmental effects and plot level manipulations. In general resource quality was higher in the more ‘targeted’ ELSX options. However there was high variability in results reflecting species specific responses to habitats at both local and landscape scales. Critical to the success of any ELS agreement is the quality of plot establishment and maintenance. Often if a sown option is not doing well after the first year, it will be unlikely to improve and should be abandoned. Both ground conditions at establishment and subsequent weather conditions contributed to the high plot variability obs

In a four-year experimental study, the effects of various pre-sowing disturbance treatments (band-spraying with herbicide; soil harrowing; creation of ridge and furrow structures) and of post-establishment sward management regimes on the performance of habitat specialist plant species known to perform poorly in the restoration of lowland calcareous grassland was tested. It was found that as with generalist species, pre-sowing disturbance is key to successful establishment. Ridge and furrow appeared to be a good alternative to more traditional means of pre-sowing disturbance such as soil harrowing in particular for low-statured species of low competitive ability with a known preference in ancient grassland for south-sloping sites and ant hills. It appears that three years of experimental sward management may have been too short a period to allow solid conclusions on the effects of various alternative options.

Population dynamics of the biennial plant Tragopogon pratensis have been monitored in the Park Grass Experiment at Rothamsted Research, Harpenden, UK, over many years. Observations of diseased T. pratensis, systemically infected by the autoecious demicyclic rust Puccinia hysterium, were made over the period 1995–2008, and confirmed an outbreak pattern of dynamics, characterised by an increase to a relatively high incidence followed by a reduction to low almost indiscernible levels. An epidemiological model was developed taking into account the biennial habit of the host plant, and the systemic nature of infection during the winter period, and the partial sterilisation of infected second year plants. Seedling emergence rate and natural mortality between seasons and within season were key parameters affecting host performance. The transmission rate between infected second year plants and susceptible first year seedlings, and the probability that the fungus would survive the winter systemically as mycelium producing aecia and telia on emerging second year plants, were key parameters associated with pathogenicity. Furthermore the possibility of pathogen-induced additional mortality was modelled. The model predicted that outbreak dynamics of T. pratensis would occur with high pathogenicity and medium or high host performance. In the former case the population dynamics would be cyclical with, in some cases, infected plants going to extinction. In the latter case both host and pathogen would go to extinction. The model predicted that the two pathogenicity parameters were critical in determining whether the pathogen would invade a healthy population; whereas pathogen-induced mortality had little influence, a result also obtained in some limited potted plant experiments. Fitting the model to the field data indicated that there was little or no density-dependence in seedling emergence rate, and again that pathogen-induced mortality played little role in the observed populatio

The Hillesden experiment has proved to be a valuable, practical test of the effectiveness of the Entry Level Stewardship scheme for a range of taxa at the farm-scale. The experiment was a large scale, randomised block experiment with three treatments applied to replicated land areas of c. 50-60 ha: i) Cross compliance (CC, conventional intensive arable management subject to the EU rules of cross compliance), ii) Entry Level Stewardship (ELS, a small suite of options selected to replicate a ‘standard’ agreement comprising 1% area out of production), iii) Entry Level Stewardship Extra (ELS X, a more extensive selection of options targeted at farmland wildlife of conservation interest comprising 5% area out of production). The results show that over a five year period (2006-2011) the effects on (i) habitat quality and food resources, and (ii) the abundance, diversity and population dynamics of some key farmland taxa were significantly enhanced by both targeted local management and enhancements at the landscape scale. However there were clear effects of scale on the responses of different taxa (see Table 1.1). Mobile species like bumblebees, moths, birds and small mammals were more subject to the effects of wider landscape context and showed a net response to the whole farm manipulation. The response of other taxa e.g. plants and some invertebrate groups, were more influenced by local environmental effects and plot level manipulations. In general resource quality was higher in the more ‘targeted’ ELSX options. However there was high variability in results reflecting species specific responses to habitats at both local and landscape scales. Critical to the success of any ELS agreement is the quality of plot establishment and maintenance. Often if a sown option is not doing well after the first year, it will be unlikely to improve and should be abandoned. Both ground conditions at establishment and subsequent weather conditions contributed to the high plot variability obs

In a four-year experimental study, the effects of various pre-sowing disturbance treatments (band-spraying with herbicide; soil harrowing; creation of ridge and furrow structures) and of post-establishment sward management regimes on the performance of habitat specialist plant species known to perform poorly in the restoration of lowland calcareous grassland was tested. It was found that as with generalist species, pre-sowing disturbance is key to successful establishment. Ridge and furrow appeared to be a good alternative to more traditional means of pre-sowing disturbance such as soil harrowing in particular for low-statured species of low competitive ability with a known preference in ancient grassland for south-sloping sites and ant hills. It appears that three years of experimental sward management may have been too short a period to allow solid conclusions on the effects of various alternative options.

Population dynamics of the biennial plant Tragopogon pratensis have been monitored in the Park Grass Experiment at Rothamsted Research, Harpenden, UK, over many years. Observations of diseased T. pratensis, systemically infected by the autoecious demicyclic rust Puccinia hysterium, were made over the period 1995–2008, and confirmed an outbreak pattern of dynamics, characterised by an increase to a relatively high incidence followed by a reduction to low almost indiscernible levels. An epidemiological model was developed taking into account the biennial habit of the host plant, and the systemic nature of infection during the winter period, and the partial sterilisation of infected second year plants. Seedling emergence rate and natural mortality between seasons and within season were key parameters affecting host performance. The transmission rate between infected second year plants and susceptible first year seedlings, and the probability that the fungus would survive the winter systemically as mycelium producing aecia and telia on emerging second year plants, were key parameters associated with pathogenicity. Furthermore the possibility of pathogen-induced additional mortality was modelled. The model predicted that outbreak dynamics of T. pratensis would occur with high pathogenicity and medium or high host performance. In the former case the population dynamics would be cyclical with, in some cases, infected plants going to extinction. In the latter case both host and pathogen would go to extinction. The model predicted that the two pathogenicity parameters were critical in determining whether the pathogen would invade a healthy population; whereas pathogen-induced mortality had little influence, a result also obtained in some limited potted plant experiments. Fitting the model to the field data indicated that there was little or no density-dependence in seedling emergence rate, and again that pathogen-induced mortality played little role in the observed populatio

The global decline of insect pollinators, especially bees, is cause for concern, and there is an urgent need for cost-effective conservation measures in agricultural landscapes. While landscape context and habitat quality are known to influence species richness and abundance of bees, there is a lack of evidence from manipulative field experiments on bees’ responses to adaptive management across differently structured landscapes. We present the results of a large-scale study that investigated the effects of a targeted agri-environment scheme (AES) on bumble bees (Bombus spp.) over three years in the United Kingdom. Forage patches of different sizes were sown with a conservation flower mixture across eight sites covering a broad range of agricultural land use types. Species richness and worker densities (especially of the longer-tongued Bombus species for which the mixture was targeted) were significantly higher on sown forage patches than on existing non-crop control habitats throughout the three-year study, but the strength of this response depended on both the proportions of arable land and abundance of herbaceous forb species in the surrounding landscape. The size of sown patches also affected worker density, with smaller patches (0.25 ha) attracting higher densities of some species than larger patches (1.0 ha). Our models show that a targeted AES can deliver greater net benefits in more intensively farmed areas, in terms of the number and species richness of bumble bees supported, than in heterogeneous landscapes where other foraging habitats exist. These findings serve to strengthen the evidence base for extending agri-environment schemes to boost declining pollinator populations to a larger number of agricultural landscapes across the globe.

It is widely recognised that healthy ecosystems can provide considerable benefits to people, including food, timber, freshwater, protection from floods and much of what we call quality of life. A global review of these ecosystem services carried out as part of the Millennium Ecosystem Assessment (MA) provided a framework for national and local studies. Using the MA approach, this paper reviews the ecosystem services provided by the Somerset Levels and Moors wetland system in south-west England. This wetland provides a series of important services that are beneficial locally, regional and globally, including grazing for cattle, potential carbon sequestration, flood water storage, recreation and archaeology. Some services are synergistic and reinforcing; for example, maintaining wet conditions supports wetland bird life that maintains biological diversity, attracts tourists, protects archaeological artefacts and reduces CO2 emissions. Other services are potentially conflicting, for example raising water levels may reduce potential flood water storage and increase methane emissions. Comparison of the services of the wetland with those of drier habitats reveals for example that carbon sequestration, bird habitat provision and hay production is greater in wetlands, whilst grazing quality and plant diversity may be reduced and distributions of disease vectors may be altered by wetland restoration through raising water levels. Management decisions affecting wetlands may necessitate a trade-off of ecosystem services.

The global decline of insect pollinators, especially bees, is cause for concern, and there is an urgent need for cost-effective conservation measures in agricultural landscapes. While landscape context and habitat quality are known to influence species richness and abundance of bees, there is a lack of evidence from manipulative field experiments on bees’ responses to adaptive management across differently structured landscapes. We present the results of a large-scale study that investigated the effects of a targeted agri-environment scheme (AES) on bumble bees (Bombus spp.) over three years in the United Kingdom. Forage patches of different sizes were sown with a conservation flower mixture across eight sites covering a broad range of agricultural land use types. Species richness and worker densities (especially of the longer-tongued Bombus species for which the mixture was targeted) were significantly higher on sown forage patches than on existing non-crop control habitats throughout the three-year study, but the strength of this response depended on both the proportions of arable land and abundance of herbaceous forb species in the surrounding landscape. The size of sown patches also affected worker density, with smaller patches (0.25 ha) attracting higher densities of some species than larger patches (1.0 ha). Our models show that a targeted AES can deliver greater net benefits in more intensively farmed areas, in terms of the number and species richness of bumble bees supported, than in heterogeneous landscapes where other foraging habitats exist. These findings serve to strengthen the evidence base for extending agri-environment schemes to boost declining pollinator populations to a larger number of agricultural landscapes across the globe.

It is widely recognised that healthy ecosystems can provide considerable benefits to people, including food, timber, freshwater, protection from floods and much of what we call quality of life. A global review of these ecosystem services carried out as part of the Millennium Ecosystem Assessment (MA) provided a framework for national and local studies. Using the MA approach, this paper reviews the ecosystem services provided by the Somerset Levels and Moors wetland system in south-west England. This wetland provides a series of important services that are beneficial locally, regional and globally, including grazing for cattle, potential carbon sequestration, flood water storage, recreation and archaeology. Some services are synergistic and reinforcing; for example, maintaining wet conditions supports wetland bird life that maintains biological diversity, attracts tourists, protects archaeological artefacts and reduces CO2 emissions. Other services are potentially conflicting, for example raising water levels may reduce potential flood water storage and increase methane emissions. Comparison of the services of the wetland with those of drier habitats reveals for example that carbon sequestration, bird habitat provision and hay production is greater in wetlands, whilst grazing quality and plant diversity may be reduced and distributions of disease vectors may be altered by wetland restoration through raising water levels. Management decisions affecting wetlands may necessitate a trade-off of ecosystem services.

This study investigated how local habitat type and landscape structure affects the biomass, species richness and functional diversity of ground beetles sampled from a 1000 ha UK arable farm. At a local scale habitat type was either crop (winter wheat and oilseed rape) or one of five field margin habitats. Surrounding each of these sampling areas, landscape structure was defined using remote sensed data from Specim AISA Eagle (400–970 nm) and Hawk (970–2450 nm) hyperspectral sensors. Ground beetles were divided into predatory and phytophagous trophic levels. Local habitat type only affected phytophagous ground beetle biomass, which was lowest within crops. Total biomass of predatory beetles was negatively correlated, and species richness positively correlated, with landscape habitat diversity. Only the functional diversity of predatory ground beetles responded to landscape structure, showing positive correlations with the proportion of Tussock Grass field margins. Predatory ground beetles show a greater dependence on landscape structure than phytophagous species, a response that is attributed to their high mobility needed for movement between dynamically variable food resources.

Analysis of seeds collected from rust (Puccinia hysterium) infected and uninfected Tragopogon pratensis, located within the Park Grass Experiment at Rothamsted Research, has shown a significant difference in the number of seeds produced and also in the subsequent number of successful germinations between seeds set by infected and uninfected plants. This supports the hypothesis that P. hysterium significantly suppresses reproduction in T. pratensis. Furthermore, seeds from infected individuals have significantly shorter pappi and seed mid-lengths whilst having no significant difference in seed mass, indicating that seeds from infected hosts have altered growth form.

This study investigated how local habitat type and landscape structure affects the biomass, species richness and functional diversity of ground beetles sampled from a 1000 ha UK arable farm. At a local scale habitat type was either crop (winter wheat and oilseed rape) or one of five field margin habitats. Surrounding each of these sampling areas, landscape structure was defined using remote sensed data from Specim AISA Eagle (400–970 nm) and Hawk (970–2450 nm) hyperspectral sensors. Ground beetles were divided into predatory and phytophagous trophic levels. Local habitat type only affected phytophagous ground beetle biomass, which was lowest within crops. Total biomass of predatory beetles was negatively correlated, and species richness positively correlated, with landscape habitat diversity. Only the functional diversity of predatory ground beetles responded to landscape structure, showing positive correlations with the proportion of Tussock Grass field margins. Predatory ground beetles show a greater dependence on landscape structure than phytophagous species, a response that is attributed to their high mobility needed for movement between dynamically variable food resources.

Analysis of seeds collected from rust (Puccinia hysterium) infected and uninfected Tragopogon pratensis, located within the Park Grass Experiment at Rothamsted Research, has shown a significant difference in the number of seeds produced and also in the subsequent number of successful germinations between seeds set by infected and uninfected plants. This supports the hypothesis that P. hysterium significantly suppresses reproduction in T. pratensis. Furthermore, seeds from infected individuals have significantly shorter pappi and seed mid-lengths whilst having no significant difference in seed mass, indicating that seeds from infected hosts have altered growth form.

The Park Grass Experiment at Rothamsted in southeast England was started in 1856, making it the longest-running experiment in plant ecology anywhere in the world. Experimental inputs include a range of fertilizers (nitrogen, phosphorus, potassium, and organic manures) applied annually, with lime applied occasionally, and these have led to an increase in biomass and, where nitrogen was applied in the form of ammonium sulfate, to substantial decreases in soil pH. The number of species per plot varies from three to 44 per 200 m2, affording a unique opportunity to study the determinants of plant species richness and to estimate the effect sizes attributable to different factors. The response of species richness to biomass depends on the amount and type of nitrogen applied; richness declined monotonically with increasing biomass on plots receiving no nitrogen or receiving nitrogen in the form of sodium nitrate, but there was no relationship between species richness and biomass on plots acidified by ammonium sulfate application. The response to lime also depended on the type of nitrogen applied; there was no relationship between lime treatment and species richness, except in plots receiving nitrogen in the form of ammonium sulfate, where species richness increased sharply with increasing soil pH. The addition of phosphorus reduced species richness, and application of potassium along with phosphorus reduced species richness further, but the biggest negative effects were when nitrogen and phosphorus were applied together. The analysis demonstrates how multiple factors contribute to the observed diversity patterns and how environmental regulation of species pools can operate at the same spatial and temporal scale as biomass effects.

The Park Grass Experiment at Rothamsted in southeast England was started in 1856, making it the longest-running experiment in plant ecology anywhere in the world. Experimental inputs include a range of fertilizers (nitrogen, phosphorus, potassium, and organic manures) applied annually, with lime applied occasionally, and these have led to an increase in biomass and, where nitrogen was applied in the form of ammonium sulfate, to substantial decreases in soil pH. The number of species per plot varies from three to 44 per 200 m2, affording a unique opportunity to study the determinants of plant species richness and to estimate the effect sizes attributable to different factors. The response of species richness to biomass depends on the amount and type of nitrogen applied; richness declined monotonically with increasing biomass on plots receiving no nitrogen or receiving nitrogen in the form of sodium nitrate, but there was no relationship between species richness and biomass on plots acidified by ammonium sulfate application. The response to lime also depended on the type of nitrogen applied; there was no relationship between lime treatment and species richness, except in plots receiving nitrogen in the form of ammonium sulfate, where species richness increased sharply with increasing soil pH. The addition of phosphorus reduced species richness, and application of potassium along with phosphorus reduced species richness further, but the biggest negative effects were when nitrogen and phosphorus were applied together. The analysis demonstrates how multiple factors contribute to the observed diversity patterns and how environmental regulation of species pools can operate at the same spatial and temporal scale as biomass effects.