Publications by authors named "Joslin L Moore"

32 Publications

A framework for allocating conservation resources among multiple threats and actions.

Conserv Biol 2021 Apr 28. Epub 2021 Apr 28.

School of BioSciences, The University of Melbourne, Parkville, Victoria, Australia.

Land managers decide how to allocate resources among multiple threats that can be addressed through multiple possible actions. Additionally, these actions vary in feasibility, effectiveness, and cost. We sought to provide a way to optimize resource allocation to address multiple threats when multiple management options are available, including mutually exclusive options. Formulating the decision as a combinatorial optimization problem, our framework takes as inputs the expected impact and cost of each threat for each action (including do nothing) and for each overall budget identifies the optimal action to take for each threat. We compared the optimal solution to an easy to calculate greedy algorithm approximation and a variety of plausible ranking schemes. We applied the framework to management of multiple introduced plant species in Australian alpine areas. We developed a model of invasion to predict the expected impact in 50 years for each species-action combination that accounted for each species' current invasion state (absent, localized, widespread); arrival probability; spread rate; impact, if present, of each species; and management effectiveness of each species-action combination. We found that the recommended action for a threat changed with budget; there was no single optimal management action for each species; and considering more than one candidate action can substantially increase the management plan's overall efficiency. The approximate solution (solution ranked by marginal cost-effectiveness) performed well when the budget matched the cost of the prioritized actions, indicating that this approach would be effective if the budget was set as part of the prioritization process. The ranking schemes varied in performance, and achieving a close to optimal solution was not guaranteed. Global sensitivity analysis revealed a threat's expected impact and, to a lesser extent, management effectiveness were the most influential parameters, emphasizing the need to focus research and monitoring efforts on their quantification.
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http://dx.doi.org/10.1111/cobi.13748DOI Listing
April 2021

General destabilizing effects of eutrophication on grassland productivity at multiple spatial scales.

Nat Commun 2020 10 23;11(1):5375. Epub 2020 Oct 23.

Department of Ecology, Evolution, and Behavior, University of MN, St. Paul, MN, 55108, USA.

Eutrophication is a widespread environmental change that usually reduces the stabilizing effect of plant diversity on productivity in local communities. Whether this effect is scale dependent remains to be elucidated. Here, we determine the relationship between plant diversity and temporal stability of productivity for 243 plant communities from 42 grasslands across the globe and quantify the effect of chronic fertilization on these relationships. Unfertilized local communities with more plant species exhibit greater asynchronous dynamics among species in response to natural environmental fluctuations, resulting in greater local stability (alpha stability). Moreover, neighborhood communities that have greater spatial variation in plant species composition within sites (higher beta diversity) have greater spatial asynchrony of productivity among communities, resulting in greater stability at the larger scale (gamma stability). Importantly, fertilization consistently weakens the contribution of plant diversity to both of these stabilizing mechanisms, thus diminishing the positive effect of biodiversity on stability at differing spatial scales. Our findings suggest that preserving grassland functional stability requires conservation of plant diversity within and among ecological communities.
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http://dx.doi.org/10.1038/s41467-020-19252-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7585434PMC
October 2020

Increasing effects of chronic nutrient enrichment on plant diversity loss and ecosystem productivity over time.

Ecology 2021 02 18;102(2):e03218. Epub 2021 Jan 18.

Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, Minnesota, 55108, USA.

Human activities are enriching many of Earth's ecosystems with biologically limiting mineral nutrients such as nitrogen (N) and phosphorus (P). In grasslands, this enrichment generally reduces plant diversity and increases productivity. The widely demonstrated positive effect of diversity on productivity suggests a potential negative feedback, whereby nutrient-induced declines in diversity reduce the initial gains in productivity arising from nutrient enrichment. In addition, plant productivity and diversity can be inhibited by accumulations of dead biomass, which may be altered by nutrient enrichment. Over longer time frames, nutrient addition may increase soil fertility by increasing soil organic matter and nutrient pools. We examined the effects of 5-11 yr of nutrient addition at 47 grasslands in 12 countries. Nutrient enrichment increased aboveground live biomass and reduced plant diversity at nearly all sites, and these effects became stronger over time. We did not find evidence that nutrient-induced losses of diversity reduced the positive effects of nutrients on biomass; however, nutrient effects on live biomass increased more slowly at sites where litter was also increasing, regardless of plant diversity. This work suggests that short-term experiments may underestimate the long-term nutrient enrichment effects on global grassland ecosystems.
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http://dx.doi.org/10.1002/ecy.3218DOI Listing
February 2021

Global impacts of fertilization and herbivore removal on soil net nitrogen mineralization are modulated by local climate and soil properties.

Glob Chang Biol 2020 Dec 22;26(12):7173-7185. Epub 2020 Sep 22.

Grupo de Investigaciones en Biología de la Conservación, INIBIOMA (CONICET-UNCOMA), Bariloche, Argentina.

Soil nitrogen (N) availability is critical for grassland functioning. However, human activities have increased the supply of biologically limiting nutrients, and changed the density and identity of mammalian herbivores. These anthropogenic changes may alter net soil N mineralization (soil net N ), that is, the net balance between N mineralization and immobilization, which could severely impact grassland structure and functioning. Yet, to date, little is known about how fertilization and herbivore removal individually, or jointly, affect soil net N across a wide range of grasslands that vary in soil and climatic properties. Here we collected data from 22 grasslands on five continents, all part of a globally replicated experiment, to assess how fertilization and herbivore removal affected potential (laboratory-based) and realized (field-based) soil net N . Herbivore removal in the absence of fertilization did not alter potential and realized soil net N . However, fertilization alone and in combination with herbivore removal consistently increased potential soil net N Realized soil net N , in contrast, significantly decreased in fertilized plots where herbivores were removed. Treatment effects on potential and realized soil net N were contingent on site-specific soil and climatic properties. Fertilization effects on potential soil net N were larger at sites with higher mean annual precipitation (MAP) and temperature of the wettest quarter (T.q.wet). Reciprocally, realized soil net N declined most strongly with fertilization and herbivore removal at sites with lower MAP and higher T.q.wet. In summary, our findings show that anthropogenic nutrient enrichment, herbivore exclusion and alterations in future climatic conditions can negatively impact soil net N across global grasslands under realistic field conditions. This is an important context-dependent knowledge for grassland management worldwide.
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http://dx.doi.org/10.1111/gcb.15308DOI Listing
December 2020

Microbial processing of plant remains is co-limited by multiple nutrients in global grasslands.

Glob Chang Biol 2020 08 10;26(8):4572-4582. Epub 2020 Jun 10.

German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, Germany.

Microbial processing of aggregate-unprotected organic matter inputs is key for soil fertility, long-term ecosystem carbon and nutrient sequestration and sustainable agriculture. We investigated the effects of adding multiple nutrients (nitrogen, phosphorus and potassium plus nine essential macro- and micro-nutrients) on decomposition and biochemical transformation of standard plant materials buried in 21 grasslands from four continents. Addition of multiple nutrients weakly but consistently increased decomposition and biochemical transformation of plant remains during the peak-season, concurrent with changes in microbial exoenzymatic activity. Higher mean annual precipitation and lower mean annual temperature were the main climatic drivers of higher decomposition rates, while biochemical transformation of plant remains was negatively related to temperature of the wettest quarter. Nutrients enhanced decomposition most at cool, high rainfall sites, indicating that in a warmer and drier future fertilized grassland soils will have an even more limited potential for microbial processing of plant remains.
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http://dx.doi.org/10.1111/gcb.15146DOI Listing
August 2020

Global gene flow releases invasive plants from environmental constraints on genetic diversity.

Proc Natl Acad Sci U S A 2020 02 7;117(8):4218-4227. Epub 2020 Feb 7.

Biodiversity and Nature Tourism, Estonian University of Life Sciences, 51006 Tartu, Estonia.

When plants establish outside their native range, their ability to adapt to the new environment is influenced by both demography and dispersal. However, the relative importance of these two factors is poorly understood. To quantify the influence of demography and dispersal on patterns of genetic diversity underlying adaptation, we used data from a globally distributed demographic research network comprising 35 native and 18 nonnative populations of Species-specific simulation experiments showed that dispersal would dilute demographic influences on genetic diversity at local scales. Populations in the native European range had strong spatial genetic structure associated with geographic distance and precipitation seasonality. In contrast, nonnative populations had weaker spatial genetic structure that was not associated with environmental gradients but with higher within-population genetic diversity. Our findings show that dispersal caused by repeated, long-distance, human-mediated introductions has allowed invasive plant populations to overcome environmental constraints on genetic diversity, even without strong demographic changes. The impact of invasive plants may, therefore, increase with repeated introductions, highlighting the need to constrain future introductions of species even if they already exist in an area.
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http://dx.doi.org/10.1073/pnas.1915848117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7049112PMC
February 2020

Nutrient availability controls the impact of mammalian herbivores on soil carbon and nitrogen pools in grasslands.

Glob Chang Biol 2020 Feb 3. Epub 2020 Feb 3.

Department of Terrestrial Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, The Netherlands.

Grasslands are subject to considerable alteration due to human activities globally, including widespread changes in populations and composition of large mammalian herbivores and elevated supply of nutrients. Grassland soils remain important reservoirs of carbon (C) and nitrogen (N). Herbivores may affect both C and N pools and these changes likely interact with increases in soil nutrient availability. Given the scale of grassland soil fluxes, such changes can have striking consequences for atmospheric C concentrations and the climate. Here, we use the Nutrient Network experiment to examine the responses of soil C and N pools to mammalian herbivore exclusion across 22 grasslands, under ambient and elevated nutrient availabilities (fertilized with NPK + micronutrients). We show that the impact of herbivore exclusion on soil C and N pools depends on fertilization. Under ambient nutrient conditions, we observed no effect of herbivore exclusion, but under elevated nutrient supply, pools are smaller upon herbivore exclusion. The highest mean soil C and N pools were found in grazed and fertilized plots. The decrease in soil C and N upon herbivore exclusion in combination with fertilization correlated with a decrease in aboveground plant biomass and microbial activity, indicating a reduced storage of organic matter and microbial residues as soil C and N. The response of soil C and N pools to herbivore exclusion was contingent on temperature - herbivores likely cause losses of C and N in colder sites and increases in warmer sites. Additionally, grasslands that contain mammalian herbivores have the potential to sequester more N under increased temperature variability and nutrient enrichment than ungrazed grasslands. Our study highlights the importance of conserving mammalian herbivore populations in grasslands worldwide. We need to incorporate local-scale herbivory, and its interaction with nutrient enrichment and climate, within global-scale models to better predict land-atmosphere interactions under future climate change.
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http://dx.doi.org/10.1111/gcb.15023DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7155038PMC
February 2020

Evaluating conservation dogs in the search for rare species.

Conserv Biol 2020 04 3;34(2):314-325. Epub 2020 Mar 3.

School of Biological Sciences, Monash University, 25 Rainforest Walk, Clayton, VIC, 3800, Australia.

Detecting rare species is important for both threatened species management and invasive species eradication programs. Conservation scent dogs provide an olfactory survey tool that has advantages over traditional visual and auditory survey techniques for some cryptic species. From the literature, we identified 5 measures important in evaluating the use of scent dogs: precision, sensitivity, effort, cost, and comparison with other techniques. We explored the scale at which performance is evaluated and examined when field testing under real working conditions is achievable. We also identified cost differences among studies. We examined 61 studies published in 1976-2018 that reported conservation dog performance, and considered the inconsistencies in the reporting of scent dog performance among these studies. The majority of studies reported some measure of performance; however, only 8 studies reported all 3 aspects necessary for performance evaluation: precision, sensitivity, and effort. Although effort was considered in 43 studies, inconsistent methods and incomplete reporting prevented meaningful evaluation of performance and comparison among studies. Differences in cost between similar studies were influenced by geographical location and how the dog and handler were sourced for the study. To develop consistent reporting for evaluation, we recommend adoption of sensitivity, precision, and effort as standard performance measures. We recommend reporting effort as the total area and total time spent searching and reporting sensitivity and precision as proportions of the sample size. Additionally, reporting of costs, survey objectives, dog training and experience, type of detection task, and human influences will provide better opportunities for comparison within and among studies.
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http://dx.doi.org/10.1111/cobi.13431DOI Listing
April 2020

Leaf nutrients, not specific leaf area, are consistent indicators of elevated nutrient inputs.

Nat Ecol Evol 2019 03 4;3(3):400-406. Epub 2019 Feb 4.

Forest Research Centre, School of Agriculture, University of Lisbon, Lisbon, Portugal.

Leaf traits are frequently measured in ecology to provide a 'common currency' for predicting how anthropogenic pressures impact ecosystem function. Here, we test whether leaf traits consistently respond to experimental treatments across 27 globally distributed grassland sites across 4 continents. We find that specific leaf area (leaf area per unit mass)-a commonly measured morphological trait inferring shifts between plant growth strategies-did not respond to up to four years of soil nutrient additions. Leaf nitrogen, phosphorus and potassium concentrations increased in response to the addition of each respective soil nutrient. We found few significant changes in leaf traits when vertebrate herbivores were excluded in the short-term. Leaf nitrogen and potassium concentrations were positively correlated with species turnover, suggesting that interspecific trait variation was a significant predictor of leaf nitrogen and potassium, but not of leaf phosphorus concentration. Climatic conditions and pretreatment soil nutrient levels also accounted for significant amounts of variation in the leaf traits measured. Overall, we find that leaf morphological traits, such as specific leaf area, are not appropriate indicators of plant response to anthropogenic perturbations in grasslands.
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http://dx.doi.org/10.1038/s41559-018-0790-1DOI Listing
March 2019

Automating analysis of vegetation with computer vision: Cover estimates and classification.

Ecol Evol 2018 Jun 15;8(12):6005-6015. Epub 2018 May 15.

School of Earth Environmental and Biological Sciences, Queensland University of Technolgy (QUT) Brisbane Qld Australia.

This study develops an approach to automating the process of vegetation cover estimates using computer vision and pattern recognition algorithms. Visual cover estimation is a key tool for many ecological studies, yet quadrat-based analyses are known to suffer from issues of consistency between people as well as across sites (spatially) and time (temporally). Previous efforts to estimate cover from photograps require considerable manual work. We demonstrate that an automated system can be used to estimate vegetation cover and the type of vegetation cover present using top-down photographs of 1 m by 1 m quadrats. Vegetation cover is estimated by modelling the distribution of color using a multivariate Gaussian. The type of vegetation cover is then classified, using illumination robust local binary pattern features, into two broad groups: () and . This system is evaluated on two datasets from the globally distributed experiment, the Nutrient Network (NutNet). These NutNet sites were selected for analyses because repeat photographs were taken over time and these sites are representative of very different grassland ecosystems-a low stature subalpine grassland in an alpine region of Australia and a higher stature and more productive lowland grassland in the Pacific Northwest of the USA. We find that estimates of treatment effects on and cover did not differ between field and automated estimates for eight of nine experimental treatments. Conclusions about total vegetation cover did not correspond quite as strongly, particularly at the more productive site. A limitation with this automated system is that the total vegetation cover is given as a percentage of pixels considered to contain vegetation, but ecologists can distinguish species with overlapping coverage and thus can estimate total coverage to exceed 100%. Automated approaches such as this offer techniques for estimating vegetation cover that are repeatable, cheaper to use, and likely more reliable for quantifying changes in vegetation over the long-term. These approaches would also enable ecologists to increase the spatial and temporal depth of their coverage estimates with methods that allow for vegetation sampling over large spatial scales quickly.
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http://dx.doi.org/10.1002/ece3.4135DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6024135PMC
June 2018

Spatial heterogeneity in species composition constrains plant community responses to herbivory and fertilisation.

Ecol Lett 2018 09 27;21(9):1364-1371. Epub 2018 Jun 27.

Department of Biology, Duke University, Durham, NC, 27708, USA.

Environmental change can result in substantial shifts in community composition. The associated immigration and extinction events are likely constrained by the spatial distribution of species. Still, studies on environmental change typically quantify biotic responses at single spatial (time series within a single plot) or temporal (spatial beta diversity at single time points) scales, ignoring their potential interdependence. Here, we use data from a global network of grassland experiments to determine how turnover responses to two major forms of environmental change - fertilisation and herbivore loss - are affected by species pool size and spatial compositional heterogeneity. Fertilisation led to higher rates of local extinction, whereas turnover in herbivore exclusion plots was driven by species replacement. Overall, sites with more spatially heterogeneous composition showed significantly higher rates of annual turnover, independent of species pool size and treatment. Taking into account spatial biodiversity aspects will therefore improve our understanding of consequences of global and anthropogenic change on community dynamics.
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http://dx.doi.org/10.1111/ele.13102DOI Listing
September 2018

Addition of multiple limiting resources reduces grassland diversity.

Nature 2016 09 24;537(7618):93-96. Epub 2016 Aug 24.

Swiss Federal Institute for Forest, Snow and Landscape Research, Community Ecology, Birmensdorf 8903, Switzerland.

Niche dimensionality provides a general theoretical explanation for biodiversity-more niches, defined by more limiting factors, allow for more ways that species can coexist. Because plant species compete for the same set of limiting resources, theory predicts that addition of a limiting resource eliminates potential trade-offs, reducing the number of species that can coexist. Multiple nutrient limitation of plant production is common and therefore fertilization may reduce diversity by reducing the number or dimensionality of belowground limiting factors. At the same time, nutrient addition, by increasing biomass, should ultimately shift competition from belowground nutrients towards a one-dimensional competitive trade-off for light. Here we show that plant species diversity decreased when a greater number of limiting nutrients were added across 45 grassland sites from a multi-continent experimental network. The number of added nutrients predicted diversity loss, even after controlling for effects of plant biomass, and even where biomass production was not nutrient-limited. We found that elevated resource supply reduced niche dimensionality and diversity and increased both productivity and compositional turnover. Our results point to the importance of understanding dimensionality in ecological systems that are undergoing diversity loss in response to multiple global change factors.
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http://dx.doi.org/10.1038/nature19324DOI Listing
September 2016

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

Philos Trans R Soc Lond B Biol Sci 2016 05;371(1694)

Graduate School of Life Sciences, Tohoku University, Aoba 6-3, Aramaki, Aoba-ku, Sendai 982-0011, Japan.

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.
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http://dx.doi.org/10.1098/rstb.2015.0283DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4843703PMC
May 2016

Climate modifies response of non-native and native species richness to nutrient enrichment.

Philos Trans R Soc Lond B Biol Sci 2016 05;371(1694)

Department of Ecology, Evolution, and Behavior, University of Minnesota, St Paul, MN 55108, USA.

Ecosystem eutrophication often increases domination by non-natives and causes displacement of native taxa. However, variation in environmental conditions may affect the outcome of interactions between native and non-native taxa in environments where nutrient supply is elevated. We examined the interactive effects of eutrophication, climate variability and climate average conditions on the success of native and non-native plant species using experimental nutrient manipulations replicated at 32 grassland sites on four continents. We hypothesized that effects of nutrient addition would be greatest where climate was stable and benign, owing to reduced niche partitioning. We found that the abundance of non-native species increased with nutrient addition independent of climate; however, nutrient addition increased non-native species richness and decreased native species richness, with these effects dampened in warmer or wetter sites. Eutrophication also altered the time scale in which grassland invasion responded to climate, decreasing the importance of long-term climate and increasing that of annual climate. Thus, climatic conditions mediate the responses of native and non-native flora to nutrient enrichment. Our results suggest that the negative effect of nutrient addition on native abundance is decoupled from its effect on richness, and reduces the time scale of the links between climate and compositional change.
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http://dx.doi.org/10.1098/rstb.2015.0273DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4843694PMC
May 2016

Adapting to a warming world: Ecological restoration, climate change, and genomics.

Am J Bot 2016 04 28;103(4):590-2. Epub 2016 Mar 28.

School of Biological Sciences, Building 18, Monash University, Melbourne, Victoria, Australia, 3800.

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http://dx.doi.org/10.3732/ajb.1600049DOI Listing
April 2016

Comment on "Worldwide evidence of a unimodal relationship between productivity and plant species richness".

Science 2016 Jan;351(6272):457

Department of Ecology, Environment and Evolution, La Trobe University, Kingsbury Drive, Bundoora 3086, Victoria, Australia.

Fraser et al. (Reports, 17 July 2015, p. 302) report a unimodal relationship between productivity and species richness at regional and global scales, which they contrast with the results of Adler et al. (Reports, 23 September 2011, p. 1750). However, both data sets, when analyzed correctly, show clearly and consistently that productivity is a poor predictor of local species richness.
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http://dx.doi.org/10.1126/science.aad6236DOI Listing
January 2016

Plant species' origin predicts dominance and response to nutrient enrichment and herbivores in global grasslands.

Nat Commun 2015 Jul 15;6:7710. Epub 2015 Jul 15.

Department of Entomology, University of Maryland, College Park Maryland 20742, USA.

Exotic species dominate many communities; however the functional significance of species' biogeographic origin remains highly contentious. This debate is fuelled in part by the lack of globally replicated, systematic data assessing the relationship between species provenance, function and response to perturbations. We examined the abundance of native and exotic plant species at 64 grasslands in 13 countries, and at a subset of the sites we experimentally tested native and exotic species responses to two fundamental drivers of invasion, mineral nutrient supplies and vertebrate herbivory. Exotic species are six times more likely to dominate communities than native species. Furthermore, while experimental nutrient addition increases the cover and richness of exotic species, nutrients decrease native diversity and cover. Native and exotic species also differ in their response to vertebrate consumer exclusion. These results suggest that species origin has functional significance, and that eutrophication will lead to increased exotic dominance in grasslands.
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http://dx.doi.org/10.1038/ncomms8710DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4518311PMC
July 2015

Grassland productivity limited by multiple nutrients.

Nat Plants 2015 Jul 6;1:15080. Epub 2015 Jul 6.

Department of Plant and Soil Sciences, University of Kentucky, Lexington, Kentucky 40546, USA.

Terrestrial ecosystem productivity is widely accepted to be nutrient limited(1). Although nitrogen (N) is deemed a key determinant of aboveground net primary production (ANPP)(2,3), the prevalence of co-limitation by N and phosphorus (P) is increasingly recognized(4-8). However, the extent to which terrestrial productivity is co-limited by nutrients other than N and P has remained unclear. Here, we report results from a standardized factorial nutrient addition experiment, in which we added N, P and potassium (K) combined with a selection of micronutrients (K+μ), alone or in concert, to 42 grassland sites spanning five continents, and monitored ANPP. Nutrient availability limited productivity at 31 of the 42 grassland sites. And pairwise combinations of N, P, and K+μ co-limited ANPP at 29 of the sites. Nitrogen limitation peaked in cool, high latitude sites. Our findings highlight the importance of less studied nutrients, such as K and micronutrients, for grassland productivity, and point to significant variations in the type and degree of nutrient limitation. We suggest that multiple-nutrient constraints must be considered when assessing the ecosystem-scale consequences of nutrient enrichment.
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http://dx.doi.org/10.1038/nplants.2015.80DOI Listing
July 2015

The optimal number of surveys when detectability varies.

PLoS One 2014 19;9(12):e115345. Epub 2014 Dec 19.

Australian Research Centre for Urban Ecology, Royal Botanic Gardens Melbourne, Parkville, Victoria, Australia; School of Biological Sciences, Monash University, Melbourne, Victoria, Australia.

The survey of plant and animal populations is central to undertaking field ecology. However, detection is imperfect, so the absence of a species cannot be determined with certainty. Methods developed to account for imperfect detectability during surveys do not yet account for stochastic variation in detectability over time or space. When each survey entails a fixed cost that is not spent searching (e.g., time required to travel to the site), stochastic detection rates result in a trade-off between the number of surveys and the length of each survey when surveying a single site. We present a model that addresses this trade-off and use it to determine the number of surveys that: 1) maximizes the expected probability of detection over the entire survey period; and 2) is most likely to achieve a minimally-acceptable probability of detection. We illustrate the applicability of our approach using three practical examples (minimum survey effort protocols, number of frog surveys per season, and number of quadrats per site to detect a plant species) and test our model's predictions using data from experimental plant surveys. We find that when maximizing the expected probability of detection, the optimal survey design is most sensitive to the coefficient of variation in the rate of detection and the ratio of the search budget to the travel cost. When maximizing the likelihood of achieving a particular probability of detection, the optimal survey design is most sensitive to the required probability of detection, the expected number of detections if the budget were spent only on searching, and the expected number of detections that are missed due to travel costs. We find that accounting for stochasticity in detection rates is likely to be particularly important for designing surveys when detection rates are low. Our model provides a framework to do this.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0115345PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4272285PMC
December 2015

Herbivores and nutrients control grassland plant diversity via light limitation.

Nature 2014 Apr 9;508(7497):517-20. Epub 2014 Mar 9.

Instituto de Investigaciones Marinas y Costeras (IIMyC), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Mar del Plata 7600 , Argentina.

Human alterations to nutrient cycles and herbivore communities are affecting global biodiversity dramatically. Ecological theory predicts these changes should be strongly counteractive: nutrient addition drives plant species loss through intensified competition for light, whereas herbivores prevent competitive exclusion by increasing ground-level light, particularly in productive systems. Here we use experimental data spanning a globally relevant range of conditions to test the hypothesis that herbaceous plant species losses caused by eutrophication may be offset by increased light availability due to herbivory. This experiment, replicated in 40 grasslands on 6 continents, demonstrates that nutrients and herbivores can serve as counteracting forces to control local plant diversity through light limitation, independent of site productivity, soil nitrogen, herbivore type and climate. Nutrient addition consistently reduced local diversity through light limitation, and herbivory rescued diversity at sites where it alleviated light limitation. Thus, species loss from anthropogenic eutrophication can be ameliorated in grasslands where herbivory increases ground-level light.
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http://dx.doi.org/10.1038/nature13144DOI Listing
April 2014

Eutrophication weakens stabilizing effects of diversity in natural grasslands.

Nature 2014 Apr 16;508(7497):521-5. Epub 2014 Feb 16.

Swiss Federal Institute for Forest, Snow and Landscape Research, 8903 Birmensdorf, Switzerland.

Studies of experimental grassland communities have demonstrated that plant diversity can stabilize productivity through species asynchrony, in which decreases in the biomass of some species are compensated for by increases in others. However, it remains unknown whether these findings are relevant to natural ecosystems, especially those for which species diversity is threatened by anthropogenic global change. Here we analyse diversity-stability relationships from 41 grasslands on five continents and examine how these relationships are affected by chronic fertilization, one of the strongest drivers of species loss globally. Unmanipulated communities with more species had greater species asynchrony, resulting in more stable biomass production, generalizing a result from biodiversity experiments to real-world grasslands. However, fertilization weakened the positive effect of diversity on stability. Contrary to expectations, this was not due to species loss after eutrophication but rather to an increase in the temporal variation of productivity in combination with a decrease in species asynchrony in diverse communities. Our results demonstrate separate and synergistic effects of diversity and eutrophication on stability, emphasizing the need to understand how drivers of global change interactively affect the reliable provisioning of ecosystem services in real-world systems.
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http://dx.doi.org/10.1038/nature13014DOI Listing
April 2014

Predicting invasion in grassland ecosystems: is exotic dominance the real embarrassment of richness?

Glob Chang Biol 2013 Dec 16;19(12):3677-87. Epub 2013 Oct 16.

Department of Ecology, Evolution, and Behavior, University of MN, St. Paul, MN, 55108, USA.

Invasions have increased the size of regional species pools, but are typically assumed to reduce native diversity. However, global-scale tests of this assumption have been elusive because of the focus on exotic species richness, rather than relative abundance. This is problematic because low invader richness can indicate invasion resistance by the native community or, alternatively, dominance by a single exotic species. Here, we used a globally replicated study to quantify relationships between exotic richness and abundance in grass-dominated ecosystems in 13 countries on six continents, ranging from salt marshes to alpine tundra. We tested effects of human land use, native community diversity, herbivore pressure, and nutrient limitation on exotic plant dominance. Despite its widespread use, exotic richness was a poor proxy for exotic dominance at low exotic richness, because sites that contained few exotic species ranged from relatively pristine (low exotic richness and cover) to almost completely exotic-dominated ones (low exotic richness but high exotic cover). Both exotic cover and richness were predicted by native plant diversity (native grass richness) and land use (distance to cultivation). Although climate was important for predicting both exotic cover and richness, climatic factors predicting cover (precipitation variability) differed from those predicting richness (maximum temperature and mean temperature in the wettest quarter). Herbivory and nutrient limitation did not predict exotic richness or cover. Exotic dominance was greatest in areas with low native grass richness at the site- or regional-scale. Although this could reflect native grass displacement, a lack of biotic resistance is a more likely explanation, given that grasses comprise the most aggressive invaders. These findings underscore the need to move beyond richness as a surrogate for the extent of invasion, because this metric confounds monodominance with invasion resistance. Monitoring species' relative abundance will more rapidly advance our understanding of invasions.
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http://dx.doi.org/10.1111/gcb.12370DOI Listing
December 2013

Quantifying plant colour and colour difference as perceived by humans using digital images.

PLoS One 2013 20;8(8):e72296. Epub 2013 Aug 20.

Australian Research Centre for Urban Ecology, Royal Botanic Gardens, Melbourne, Victoria, Australia.

Human perception of plant leaf and flower colour can influence species management. Colour and colour contrast may influence the detectability of invasive or rare species during surveys. Quantitative, repeatable measures of plant colour are required for comparison across studies and generalisation across species. We present a standard method for measuring plant leaf and flower colour traits using images taken with digital cameras. We demonstrate the method by quantifying the colour of and colour difference between the flowers of eleven grassland species near Falls Creek, Australia, as part of an invasive species detection experiment. The reliability of the method was tested by measuring the leaf colour of five residential garden shrub species in Ballarat, Australia using five different types of digital camera. Flowers and leaves had overlapping but distinct colour distributions. Calculated colour differences corresponded well with qualitative comparisons. Estimates of proportional cover of yellow flowers identified using colour measurements correlated well with estimates obtained by measuring and counting individual flowers. Digital SLR and mirrorless cameras were superior to phone cameras and point-and-shoot cameras for producing reliable measurements, particularly under variable lighting conditions. The analysis of digital images taken with digital cameras is a practicable method for quantifying plant flower and leaf colour in the field or lab. Quantitative, repeatable measurements allow for comparisons between species and generalisations across species and studies. This allows plant colour to be related to human perception and preferences and, ultimately, species management.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0072296PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3748102PMC
January 2015

Combining structured decision making and value-of-information analyses to identify robust management strategies.

Conserv Biol 2012 Oct 2;26(5):810-20. Epub 2012 Aug 2.

Australian Research Centre for Urban Ecology, Royal Botanic Gardens, Melbourne, c/o School of Botany, University of Melbourne, Victoria 3010, Australia.

Structured decision making and value-of-information analyses can be used to identify robust management strategies even when uncertainty about the response of the system to management is high. We used these methods in a case study of management of the non-native invasive species gray sallow willow (Salix cinerea) in alpine Australia. Establishment of this species is facilitated by wildfire. Managers are charged with developing a management strategy despite extensive uncertainty regarding the frequency of fires, the willow's demography, and the effectiveness of management actions. We worked with managers in Victoria to conduct a formal decision analysis. We used a dynamic model to identify the best management strategy for a range of budgets. We evaluated the robustness of the strategies to uncertainty with value-of-information analyses. Results of the value-of-information analysis indicated that reducing uncertainty would not change which management strategy was identified as the best unless budgets increased substantially. This outcome suggests there would be little value in implementing adaptive management for the problem we analyzed. The value-of-information analyses also highlighted that the main driver of gray sallow willow invasion (i.e., fire frequency) is not necessarily the same factor that is most important for decision making (i.e., willow seed dispersal distance). Value of-information analyses enables managers to better target monitoring and research efforts toward factors critical to making the decision and to assess the need for adaptive management.
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http://dx.doi.org/10.1111/j.1523-1739.2012.01907.xDOI Listing
October 2012

Productivity is a poor predictor of plant species richness.

Science 2011 Sep;333(6050):1750-3

Department of Wildland Resources and the Ecology Center, Utah State University, 5230 Old Main, Logan, UT 84322, USA.

For more than 30 years, the relationship between net primary productivity and species richness has generated intense debate in ecology about the processes regulating local diversity. The original view, which is still widely accepted, holds that the relationship is hump-shaped, with richness first rising and then declining with increasing productivity. Although recent meta-analyses questioned the generality of hump-shaped patterns, these syntheses have been criticized for failing to account for methodological differences among studies. We addressed such concerns by conducting standardized sampling in 48 herbaceous-dominated plant communities on five continents. We found no clear relationship between productivity and fine-scale (meters(-2)) richness within sites, within regions, or across the globe. Ecologists should focus on fresh, mechanistic approaches to understanding the multivariate links between productivity and richness.
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http://dx.doi.org/10.1126/science.1204498DOI Listing
September 2011

Estimating detection-effort curves for plants using search experiments.

Ecol Appl 2011 Mar;21(2):601-7

Applied Environment Decision Analysis CERF, School of Botany, University of Melbourne, Parkville 3010, Victoria, Australia.

Recent studies suggest that plant detection is not perfect, even for large, highly visible plants. However, this is often not taken into account during plant surveys where failing to detect a plant when present can result in poor management and biodiversity outcomes. Including knowledge of imperfect detectability into survey design and evaluation is hampered by the paucity of empirical data, and in particular, how detectability will change with search effort, plant size and abundance, the surrounding vegetation, or observer experience. We carried out a search experiment to measure the detection-effort curve for the invasive species orange hawkweed (Hieracium aurantiacum) in Victoria, Australia. The probability that hawkweed was detected increased with increasing search effort and the number of plants at the location. While detection probability varied between observers, experience appeared to have little effect. Accounting for imperfect detectability in plant surveys holds much promise for improved survey design and biodiversity outcomes, and we encourage other researchers to undertake similar experiments to further our understanding of plant detectability.
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http://dx.doi.org/10.1890/10-0590.1DOI Listing
March 2011

Abundance of introduced species at home predicts abundance away in herbaceous communities.

Ecol Lett 2011 Mar 1;14(3):274-81. Epub 2011 Feb 1.

CSIRO Ecosystem Sciences, St. Lucia, Qld 4067, Australia.

Many ecosystems worldwide are dominated by introduced plant species, leading to loss of biodiversity and ecosystem function. A common but rarely tested assumption is that these plants are more abundant in introduced vs. native communities, because ecological or evolutionary-based shifts in populations underlie invasion success. Here, data for 26 herbaceous species at 39 sites, within eight countries, revealed that species abundances were similar at native (home) and introduced (away) sites - grass species were generally abundant home and away, while forbs were low in abundance, but more abundant at home. Sites with six or more of these species had similar community abundance hierarchies, suggesting that suites of introduced species are assembling similarly on different continents. Overall, we found that substantial changes to populations are not necessarily a pre-condition for invasion success and that increases in species abundance are unusual. Instead, abundance at home predicts abundance away, a potentially useful additional criterion for biosecurity programmes.
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http://dx.doi.org/10.1111/j.1461-0248.2010.01584.xDOI Listing
March 2011

Active adaptive conservation of threatened species in the face of uncertainty.

Ecol Appl 2010 Jul;20(5):1476-89

Centre for Applied Environmental Decision Analysis, School of Biological Sciences, University of Queensland, St Lucia, QLD 4069, Australia.

Adaptive management has a long history in the natural resource management literature, but despite this, few practitioners have developed adaptive strategies to conserve threatened species. Active adaptive management provides a framework for valuing learning by measuring the degree to which it improves long-run management outcomes. The challenge of an active adaptive approach is to find the correct balance between gaining knowledge to improve management in the future and achieving the best short-term outcome based on current knowledge. We develop and analyze a framework for active adaptive management of a threatened species. Our case study concerns a novel facial tumor disease affecting the Australian threatened species Sarcophilus harrisii: the Tasmanian devil. We use stochastic dynamic programming with Bayesian updating to identify the management strategy that maximizes the Tasmanian devil population growth rate, taking into account improvements to management through learning to better understand disease latency and the relative effectiveness of three competing management options. Exactly which management action we choose each year is driven by the credibility of competing hypotheses about disease latency and by the population growth rate predicted by each hypothesis under the competing management actions. We discover that the optimal combination of management actions depends on the number of sites available and the time remaining to implement management. Our approach to active adaptive management provides a framework to identify the optimal amount of effort to invest in learning to achieve long-run conservation objectives.
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http://dx.doi.org/10.1890/09-0647.1DOI Listing
July 2010