Turnover Metrics Research Articles

Slower but deeper community change: Intrinsic dynamics regulate anthropogenic impacts on species temporal turnover.

Understanding the mechanisms behind biodiversity dynamics is central to assessing and forecasting anthropogenic impacts on ecological communities. However, the manner in which external environmental drivers act in concert with intrinsic ecological processes to influence local temporal turnover is currently largely unexplored. Here, we determine how human impacts affect multiple metrics of bird community turnover to establish the ecological mechanisms behind compositional change. We used US Breeding Bird Survey data to calculate transect-level rates of three measures of temporal species turnover: (1) "short-term" (initial rate of decline of Sørensen similarity), (2) "long-term" (asymptotic Sørensen similarity), and (3) "throughput" (overall species accumulation rate from species-time relationship exponents) over 2692 transects across 27 regional habitat types. We then hierarchically fit linear models to estimate the effect of anthropogenic impact on these turnover metrics, using the Human Modification Index proxy, while accounting for observed species richness, the size of the species pool, and annual environmental variability. We found broadly consistent impacts of increased anthropogenic pressures across diverse habitat types. The Human Modification Index was associated with greater turnover at long timescales, but marginally slower short-term turnover. The species "throughput" (accumulation rate) was not notably influenced. Examining anthropogenic impacts on different aspects of species turnover in combination allows greater ecological insight. Observed human impacts on short-term turnover were the opposite of existing expectations and suggest humans are disrupting the background turnover of these systems, rather than simply driving rapid directed turnover. The increased long-term turnover without concurrent increases in species accumulation implies human impacts lead to shifts in species occurrence frequency rather than simply greater arrival of "new" species. These results highlight the role of intrinsic dynamics and caution against simple interpretations of increased species turnover as reflections of environmental change.

Spatial patterns and drivers of native plant diversity in Hainan, China

AbstractHainan Island has the most extensive and well‐preserved tropical forests in China. With rapid economic development of Hainan, biodiversity is increasingly at risk. Determining the spatial patterns of plant diversity in Hainan and explaining the drivers behind plant diversity are important considerations in assessing and maximizing the effectiveness of national parks, such as the newly designated Hainan Rainforest National Park. We assessed phylogenetic diversity patterns, and species richness using 106,252 georeferenced specimen records and a molecular phylogeny of 3,792 native plant species. Based on phylogenetic range‐weighted turnover metrics, we divided Hainan flora into four major floristic units. The Grade of Membership model was used to further verify the four units, and to understand their boundaries and the internal structure of each floristic unit. Finally, the best combination model was used to explore the driving mechanisms underlying the division. Our results reveal that central Hainan is the most important hotspot for plant endemism and diversity, followed by the southern area. Environmental energy is the main factor determining the spatial patterns of native plant diversity on the island, and accessibility has the greatest impact on native plant diversity among social factors. We explore patterns of spatial phylogenetics and biogeography to identify potential priorities for management and conservation drivers of plant diversity patterns across Hainan, to provide the basis for the effective protection of native plant diversity and the improvement of national parks of Hainan Island.

ANALISIS MANAJEMEN RANTAI PASOKAN PLASTIK STUDI PADA UMKM EDI PLASTIK KABUPATEN BANDUNG

There is uncertainty in the quality of raw materials delivered by suppliers to MSMEs Edi Plastik Bandung Regency, uncertainty in the quality of products delivered to consumers, information processing barriers regarding the decline in product prices in the market. The research was conducted at MSMEs Edi Plastik Bandung Regency which processed plastic waste into semi-finished goods. The research method used, namely descriptive methods with data collection techniques, namely through interviews and observations. The result of this study is that there are four actors involved in the supply chain. The flow of goods flows from upstream to downstream in the form of distribution of plastic waste raw materials from collectors and suppliers and distribution of products to consumers in the form of semi-finished products, while from downstream to upstream about returns and repairs. The flow of money uses two transactions, namely in cash, and transfers. The flow of information from downstream to upstream regarding capacity, delivery status, while from upstream to downstream regarding stock and ordering. Supervision of raw materials will overcome the uncertainty of raw material quality, the determination of product quality standards that can overcome the uncertainty of the products produced. The performance of MSMEs Edi Plastik Bandung Regency in the attributes of responsiveness, agility, and cost has achieved good performance. As for the reability and asset management attributes for asset turnover metrics are in the parity category.

Anthropogenic drivers of avian community turnover from local to regional scales.

Anthropogenic change has altered the composition and function of ecological communities across the globe. As a result, there is a need for studies examining observed community compositional change and determining whether and how anthropogenic change drivers may be influencing that turnover. In particular, it is also important to determine to what extent community turnover is idiosyncratic or if turnover can be explained by predictable responses across species based on traits or niche characteristics. Here, we measured turnover in avian communities across North America from 1990 to 2016 in the Breeding Bird Survey using an ordination method, and modeled turnover as a function of land use and climate change drivers from local to regional scales. We also examined how turnover may be attributed to species groups, including foraging guilds, trophic groups, migratory distance, and breeding biomes. We found that at local scales, land use change explained a greater proportion of variance in turnover than climate change variables, while as scale increased, trends in temperature explained a greater proportion of variance in turnover. We also found across the study region, turnover could be attributed to one of a handful of species undergoing strong expansions or strong declines over the study time period. We did not observe consistent patterns in compositional change in any trait groups we examined except for those that included previously identified highly influential species. Our results have two important implications: First, the relative importance of different anthropogenic change drivers may vary with scale, which should be considered in studies' modeling impacts of global change on biodiversity. Second, in North American avian communities, individual species undergoing large shifts in population may drive signals in compositional change, and composite community turnover metrics should be carefully selected as a result.

Combining economic recovery with climate change mitigation: A global evaluation of financial instruments

Although some countries are gradually returning to production and life, the COVID-19 pandemic continues to affect the world, further motivating recovery policies. Using a global computable general equilibrium (CGE) model, this study evaluates the environmental and economic impacts of COVID-19 on the world, both today and in the longer term. This study explores the post-pandemic impacts conditional on varied fiscal policies (including forgone revenue and additional spending) and their combination with a carbon tax. This study finds that the pandemic shocks in 2020 slowed regional economies worldwide, and a continued pandemic in 2021 will further stymie economic activity. Among the government’s recovery policies, indirect tax reduction has the best positive stimulus to regional economies; however, it is not conducive to low-carbon energy development and will also lead to an increase in CO2 and pollutant emissions. A post-pandemic green recovery plan could prioritize replacing indirect production taxes with taxes on GHG emissions, which would both improve economic turnover metrics and reduce environmental emissions in 2021. In the long run, this tax shift will not only minimize the economic damage to the global economy but also help governments around the world to get back on track in meeting the goals of the Paris Agreement.

Employee Turnover from a Different Perspective

Students of human resources management are all‐too‐familiar with employee turnover metrics. Low turnover equates to lower recruiting expenses, less need to engage in hiring trials and tribulations, less initial training, and the list goes on. Management theory places great value on low employee turnover… for significant reasons. Longer term employees tend to show more of a commitment to the workplace and, all other things being equal, employment satisfaction.

Spatial phylogenetics of the native woody plant species in Hainan, China.

To better identify biodiversity hotspots for conservation on Hainan Island, a tropical island in southern China, we assessed spatial variation in phylogenetic diversity and species richness using 18,976 georeferenced specimen records and a newly reconstructed molecular phylogeny of 957 native woody plants. Within this framework, we delineated bioregions based on vegetation composition and mapped areas of neoendemism and paleoendemism to identify areas of priority for conservation. Our results reveal that the southwest of Hainan is the most important hot spot for endemism and plant diversity followed by the southeast area. The distribution of endemic species showed a scattered, rather than clustered, pattern on the island. Based on phylogenetic range‐weighted turnover metrics, we delineated three major vegetational zones in Hainan. These largely correspond to natural secondary growth and managed forests (e.g., rubber and timber forests) in central Hainan, old‐growth forests and natural secondary growth forest at the margins of Hainan, and nature reserves on the island (e.g., Jianfeng and Diaoluo National Nature Reserves). Our study helps to elucidate potential botanical conservation priorities for Hainan within an evolutionary, phylogenetic framework.

Portfolio turnover and performance of equity investment funds in Brazil

ABSTRACT The purpose of this paper was to analyze the relationships between the portfolio turnover and performance of equity investment funds in Brazil. There are few published studies on the subject, but the previously identified Brazilian studies that have examined making changes to portfolios have been limited to very restricted data samples and have only worked with an ordinary least squares (OLS) model without taking into account the indications of international studies and economic theory itself of the possible endogeneity of turnover, which would make OLS estimation inadequate. The expressive growth of the fund industry in the Brazilian market shows the relevance of the object of research. Two portfolio turnover metrics were analyzed: one based on changes in the monetary values of the assets and another based on changing the weights of the assets in the portfolio. The estimations were performed for fixed effects panel data and then for a two-stage least squares model, using instrumental variables. The funds that make up the sample are those classified as “free shares” in the period from January of 2012 to January of 2018. The results showed that there is a positive relationship between the portfolio turnover and performance of the equity investment funds, showing that managers have been able to take advantage of moments of mispricing in the market and that they carry out more trades in search of higher returns. This research extends the results in the literature as it shows that there is a positive relationship between the turnover and performance of equity investment funds that is independent of the way turnover or performance are measured, which has shown inconclusive results in previous studies. Furthermore, it presents evidence for a more representative and current sample in an emerging market.

Rebooting strategic human resource management: integrating technology to drive talent management

This study of the literature explores how organisations innovatively integrate technology into strategic human resource management (SHRM) practices, which are driving talent management and creating greater competitive advantages. SHRM ensures the company has the number of employees and systems with the levels and types of skills required to promote and achieve the goals of the company's strategic plan. Talent management considers the people and talent acquisition analytics consisting of recruitment and succession planning. The playbooks and platforms analytics involve incorporating technologies in workflows, retention and turnover metrics, collaborations, and training and development initiatives. Combining technology with SHRM processes leads to higher organisational performance. Innovative ways of using technologies to recruit, hire, train and develop, and retain high-potential human capital pools are sources of competitive advantages. Human resource departments and technologies are the most influential players in the strategic planning of an organisation. Therefore, management should engage in stronger complementary and autonomous roles within SHRM.

Plant diversity changes in a nature reserve: a probabilistic sampling method for quantitative assessments

Species pool conservation is critical for the stability of ecosystem processes. However, climate and land use changes will likely affect biodiversity, and managers of protected areas are under increasing pressure to monitor native species diversity changes by approaches that are scientifically sound and comparable over time. Here we describe a plant diversity monitoring system in use since 2002 in the “Montagna di Torricchio” Nature Reserve (LTER_EU_IT_033), a Central Apennines representative area of 317 ha, most of which is under strict protection. The aim of this paper was to assess changes in plant species richness over time and to deduce the patterns of species assemblage. The monitoring system was based on a probabilistic sampling design representative of the different physiognomic vegetation types occurring in the Reserve. A total of 34 plots (10×10m) were sampled in 2002, 2003 and 2015, and their species presence/absence and relative coverage were estimated. Repeated measure ANOVA was used to test for plot-level and ecosystem-based changes in species richness along the study period. Temporal nestedness and temporal turnover metrics were used to assess patterns of species’ compositional changes. The results showed significantly different levels of species richness depending on the year, with the lowest value in 2003, probably linked to extreme drought events. Forest systems were comparatively stable, demonstrating the capacity to buffer interannual climate variability. Regarding compositional changes along the entire period (2002–2015), we found random patterns of both temporal nestedness and turnover, indicating stability in species composition. However, we also showed the contemporary occurrence of species loss and species replacement processes, considering the dry year 2003, a finding which should be further explored through fine-scale studies to unravel mechanisms of community assembly under drought. The use of a probabilistic sampling design representative of the different physiognomic vegetation types proved to be advantageous in monitoring the Nature Reserve vegetation and collecting reliable quantitative information. This data, in turn, provides the basis for improvements in management practices and proposed adaptation measures.

Range‐weighted metrics of species and phylogenetic turnover can better resolve biogeographic transition zones

Summary Understanding changes of biodiversity across the landscape underlies biogeography and ecology and is important in land management and conservation. Measures of species and phylogenetic turnover used to estimate the rate of change of assemblages between sets of locations are more often influenced by wide‐ranging taxa. Transition zones between regions that are associated with range‐restricted taxa can be obscured by wide‐ranging taxa that span them. We present a set of new range‐weighted metrics of taxon and phylogenetic turnover, as modifications of conventional metrics, where the range‐restricted components of the assemblages are assigned greater weight in the calculations. We show how these metrics are derived from weighted endemism and phylogenetic endemism and demonstrate their properties using a continent‐wide data set of Australian Acacia. The range‐weighted metrics result in better delineated transition zones between regions, in that the rate of turnover is steeper than with conventional turnover measures. These metrics provide important complementary information for the interpretation of spatial turnover patterns derived from conventional turnover metrics. Additionally, the phylogenetic variant incorporates information about phylogenetic relatedness while also not saturating at high values of turnover, thus remaining useful for comparisons over greater distances than conventional turnover metrics.

The Effects of Increasing Ocular Surface Stimulation on Blinking and Tear Secretion.

To investigate the effect of varying levels of ocular surface stimulation on the timing and amplitude of the blink and tear secretion. Following instillation of fluorescein dye, increasing levels of air flow were directed toward the central corneas of 10 healthy subjects. Interblink interval (IBI), tear meniscus height (TMH), and fluorescence intensity were measured simultaneously. Because blinking can obscure changes in TMH, we developed novel measures of tear secretion by calculating tear meniscus fluorescein concentration (TMFC) from intensity using a mathematical model. The change of TMH and TMFC over trials and the slope of the TMFC within each IBI (IBI-TTR) were further calculated. The mean IBI was decreased by 8.08 ± 8.54 seconds from baseline to maximum air stimulation. The TMH increase was highly variable (0.41 ± 0.39 mm) among subjects, compared to the fluorescence tear turnover metrics: decrease in TMFC of 2.84 ± 0.98 natural logarithm or ln(%) and IBI-TTR of 0.065 ± 0.032 ln(%)/sec. Ocular surface stimulation was highly correlated with the TMFC and IBI-TTR, but less so with TMH (Pearson's r = 0.71, 0.69, and 0.40, P < 0.01, respectively). Blinking and tearing were significantly correlated with each other (Pearson's r = 0.56, P < 0.01), but tearing lagged behind by an average of 6.54 ± 4.07 seconds. Blinking and tearing share a common origin with sensory stimulation at the ocular surface. Both showed a dose-response increase with surface stimulation and were correlated with each other. These methods can potentially be used to understand alterations in ocular surface sensory function and associated protective responses in dry eye and other disorders of the ocular surface.

Resource availability shapes fire‐filtered savannas

AbstractQuestionsHumid savannas can be considered fire‐filtered landscapes because fire is very frequent (&lt;10 yr return intervals) and only fire‐resistant species can occur. This flammable vegetation can be functionally heterogeneous, structurally and floristically patchy. We hypothesized that resource availability (mainly water and nutrient availabilities) accounted for most of the functional and phylogenetic spatial structure of communities across these savanna landscapes.LocationEmas National Park, central Brazil.MethodsWe used individual‐based functional trait, phylogenetic and environmental data combined with spatial information to assess the main drivers and mechanisms of community functional change (turnover) in a large fire‐filtered savanna landscape. We used Mantel correlograms and a maximum rank correlation approach to assess the spatial structure and the subset of landscape factors that best predict compositional, phylogenetic, species‐based and individual‐based functional community turnovers and the mechanism by which they do operate.ResultsCommunities were spatially structured across the landscape, presenting functional convergence at shorter distances and divergence at larger distances. All of the turnover metrics presented unique spatial structures and were correlated with a unique set of landscape predictors. Soil texture accounted for the largest fraction of the spatial structure, but soil N availability, pH, altitude and fire frequency were also important.ConclusionsOur results support the idea that the patchy distribution of water and nutrients mediated by clay content shape community membership in fire‐filtered savannas, whereas current variations in fire frequency interact with resource availability to shift community attributes from species average trait values (intraspecific variability).

Quantifying Phytogeographical Regions of Australia Using Geospatial Turnover in Species Composition

The largest digitized dataset of land plant distributions in Australia assembled to date (750,741 georeferenced herbarium records; 6,043 species) was used to partition the Australian continent into phytogeographical regions. We used a set of six widely distributed vascular plant groups and three non-vascular plant groups which together occur in a variety of landscapes/habitats across Australia. Phytogeographical regions were identified using quantitative analyses of species turnover, the rate of change in species composition between sites, calculated as Simpson's beta. We propose six major phytogeographical regions for Australia: Northern, Northern Desert, Eremaean, Eastern Queensland, Euronotian and South-Western. Our new phytogeographical regions show a spatial agreement of 65% with respect to previously defined phytogeographical regions of Australia. We also confirm that these new regions are in general agreement with the biomes of Australia and other contemporary biogeographical classifications. To assess the meaningfulness of the proposed phytogeographical regions, we evaluated how they relate to broad scale environmental gradients. Physiographic factors such as geology do not have a strong correspondence with our proposed regions. Instead, we identified climate as the main environmental driver. The use of an unprecedentedly large dataset of multiple plant groups, coupled with an explicit quantitative analysis, makes this study novel and allows an improved historical bioregionalization scheme for Australian plants. Our analyses show that: (1) there is considerable overlap between our results and older biogeographic classifications; (2) phytogeographical regions based on species turnover can be a powerful tool to further partition the landscape into meaningful units; (3) further studies using phylogenetic turnover metrics are needed to test the taxonomic areas.

Long-term changes in biological soil crust cover and composition

Communities change over time due to disturbances, variations in climate, and species invasions. Biological soil crust communities are important because they contribute to erosion control and nutrient cycling. Crust types may respond differently to changes in environmental conditions: single-celled organisms and bryophytes quickly recover after a disturbance, while lichens are slow growing and dominate favorable sites. Community change in crusts has seldom been assessed using repeated measures. For this study, we hypothesized that changes in crust composition were related to disturbance, topographic position, and invasive vegetation. We monitored permanent plots in the Columbia Basin in 1999 and 2010 and compared changes in crust composition, cover, richness, and turnover with predictor variables of herbivore exclosure, elevation, heat load index, time since fire, presence of an invasive grass, and change in cover of the invasive grass. Bryophytes were cosmopolitan with high cover. Dominant lichens did not change dramatically. Indicator taxa differed by monitoring year. Bryophyte and total crust cover declined, and there was lower turnover outside of herbivore exclosures. Lichen cover did not change significantly. Plots that burned recently had high turnover. Increase in taxon richness was correlated with presence of an invasive grass in 1999. Change in cover of the invasive grass was positively related to proportional loss and negatively related to gain. Composition and turnover metrics differed significantly over 11 years, though cover was more stable between years. This study can be a baseline for assessing change in crust composition due to anthropogenic influences.

Evaluating patterns of biodiversity in managed grasslands using spatial turnover metrics

Market and policy incentives that encourage agricultural intensification, such as incentives for bioenergy, may contribute to biodiversity decline when they encourage a large-scale conversion of native and semi-natural ecosystems to production fields. In order to appreciate the impact of these incentives on biodiversity, it is imperative to better understand how native and semi-natural ecosystems contribute to plant diversity and composition. We studied the five most common types of managed grasslands in Northeastern Kansas, a region undergoing agricultural intensification. We analyzed plant community data recorded at three spatial scales in 98 managed grassland sites, and examined patterns of diversity and composition of plant species and functional groups; and spatial turnover of species and functional groups measured at different spatial scales. We found reduced soil quality and plant diversity as well as a lack of scale-dependent community patterns on sites that were historically cultivated. Forage management practices (haying or grazing) altered plant diversity and composition in native grassland remnants but not in non-native grasslands. We identified several opportunities where changes to existing management practices could benefit both conservation and bioenergy production objectives. Recommendations to conserve biodiversity include increasing the use of hay management or other biomass collection on native grassland remnants and improving the Conservation Reserve Program by increasing enrollment, adding more native species to seed mixes, and incorporating a periodic biomass collection. We also found that using measures of spatial turnover in community composition added important insights in understanding the effects of management decisions on biodiversity.

PHYLOGENETIC COMMUNITY ASSEMBLY OVER TIME IN EURASIAN PLIO-PLEISTOCENE MAMMALS

Phylogenetic community structure and assembly is a burgeoning field in the discipline of community ecology. An array of statistical techniques have been developed in order to study whether or not local assemblages of species are a phylogenetically random, overdispersed, or clustered subset of the regional species pool to which they belong. Phylogenetic clustering or overdispersion depends on aspects of species evolutionary ecology, such as habitat preference, limits of similarity among closely related species, and how traits are inherited in ancestor-descendant relationships. Here I applied the first analysis of phylogenetic community structure and assembly to Plio-Pleistocene large mammal communities of western Eurasia, with the additional goal of verifying if the existing statistics are suitable to be used with fossil data. The results demonstrate that (1) the use of phylogeny in the study of community evolution is feasible with a number of diverse metrics, (2) phylogenetic distance between fossil communities provides an important addition to classic turnover metrics, and (3) the phylogenetic structure of Eurasian Ice-Age mammal communities changed significantly around 1 Ma, when these communities were filled with closely related species from both carnivore and herbivore clades.

Effects of clearance and fragmentation on forest compositional change and recovery after 200 years in western New York

This study investigated the effects of widespread forest clearance and fragmentation on forest compositional change between pre-settlement and the present (ca. 1800-1993) in western New York. Forest compositional turnover metrics were calculated to evaluate whether soil conditions accounted for the forest compositional change, to investigate how forest clearance might have contributed to the change, and to compare with the amount of change noted in other studies that compared the pre-settlement land sur- veys and the current Forest Inventory and Analysis (FIA) surveys. The results suggested weak relations between the forest compositional change and soil conditions. The amount of change at the county level was positively correlated with the amount of forest clearance by the late 1800s and negatively correlated with the amount of remnant forest in the late 1800s. Furthermore, while the geographic distributions of late-successional taxa in the study area exhibited increased patchiness and decreased contagion, those of early-successional taxa exhibited decreased patch- iness and increased contagion. Comparison of taxa's changed abundances with seven life history charac- teristics commonly associated with early- and late- successional status showed that taxa's changed abun- dances were significantly related to maximum life and shade tolerance. Analysis of different-sized trees in different ages in the FIA survey indicated the possibility of the current forests trending back toward their pre-settlement composition.