Hasil untuk "Ecology"

N. Sotherton, P. Robertson, N. Aebischer et al.

Daniil Shirokiy, Andrey Bukaemskiy, Maximilian Henkes et al.

Abstract Cr-doped UO₂ fuels are increasingly adopted for their superior in-reactor performance compared to undoped UO₂, but their spent fuel behaviour, particularly potential Cr speciation and fission product reactivity, remains poorly understood. This investigation has used high energy resolution fluorescence detected X-ray absorption near edge structure (HERFD-XANES) spectroscopy to examine speciation of Cr and Pr/Gd within 200 ppm Cr-doped (U4.4+ 0.7Pr3+ 0.3)O2-x and 200 ppm Cr-doped (U4.4+ 0.7Gd3+ 0.3)O2-x compounds. Despite both being UO2 soluble and undersaturated, analysis indicates that Cr3+ and Pr3+/Gd3+ form perovskite type (Pr3+/Gd3+)Cr3+O3 phases, consistent with classical “grey phases” of spent fuel. The radiation tolerance of these phases was examined via swift heavy ion irradiations of PrCrO3 and GdCrO3 compounds where electron microscopy and grazing incidence synchrotron diffraction indicate significant amorphization but retention of the crystal structure. The investigation highlights the pertinence of considering the chemistry of dopants used for nuclear fuel enhancements regarding their speciation during irradiation and subsequent occurrence within spent fuel.

W. Dunson, J. Travis

P. Blake, R. Weaver, D. Hollis

Luis F. Gordillo, Priscilla E. Greenwood

We show that a simple mechanistic model of spatial dispersal for settling organisms, subject to parameter variability, can generate heavy-tailed radial probability density functions. The movement of organisms in the model consists of a two-dimensional diffusion that ceases after a random time, where the parameters that characterize each of these stages have been randomized. Our findings show that these minimal assumptions can yield heavy-tailed dispersal patterns, providing a simplified framework that increases the understanding of long-distance dispersal events in movement ecology.

Ricardo Carrizo Vergara, Marc Kéry, Trevor Hefley

We introduce the evolving categories multinomial (ECM) distribution for multivariate count data taken over time. This distribution models the counts of individuals following iid stochastic dynamics among categories, with the number and identity of the categories also evolving over time. We specify the one-time and two-times marginal distributions of the counts and the first and second order moments. When the total number of individuals is unknown, placing a Poisson prior on it yields a new distribution (ECM-Poisson), whose main properties we also describe. Since likelihoods are intractable or impractical, we propose two estimating functions for parameter estimation: a Gaussian pseudo-likelihood and a pairwise composite likelihood. We show two application scenarios: the inference of movement parameters of animals moving continuously in space-time with irregular survey regions, and the inference of vote transfer in two-rounds elections. We give three illustrations: a simulation study with Ornstein-Uhlenbeck moving individuals, paying special attention to the autocorrelation parameter; the inference of movement and behavior parameters of lesser prairie-chickens; and the estimation of vote transfer in the 2021 Chilean presidential election.

Garrett J. Knowlton, Timon T. Keller, Rupert Seidl et al.

Abstract Tree regeneration underpins forest resilience, but how pathways of postfire tree regeneration will unfold with future climate and fire regimes is difficult to anticipate. We conducted a simulation study in the Greater Yellowstone Ecosystem (GYE; United States) using a process‐based model, iLand, to ask how rates, composition, and spatial patterns of postfire tree regeneration vary with 21st‐century climate. Subalpine forest and fire dynamics were simulated through 2100 under four climate scenarios, 2 × 2 factorial of aridity (wet and dry) and temperature (warm and hot), in five GYE landscapes. We tallied postfire tree seedling density by species in simulated fires (>400 ha) at five years postfire. To assess changes in regeneration rates (total and by species) to 2100 in each landscape × climate scenario combination, we fit generalized linear models of regeneration versus time and estimated slope coefficients. To analyze spatial patterns of recovery, we compared regeneration to prefire forest state. Postfire regeneration rates were maintained through 2100 in wet scenarios but declined in the hot‐dry scenario. Seedling composition was generally consistent throughout the simulations across wet scenarios, except for declines of Engelmann spruce (Picea engelmannii). Regeneration of fire‐sensitive species declined in the hot‐dry scenario, with Engelmann spruce experiencing the steepest declines (−20% to −71%) and failing by late century. Lodgepole pine (Pinus contorta var. latifolia) and subalpine fir (Abies lasiocarpa) declined in the hot‐dry scenario, but regeneration never failed. Regeneration of fire‐tolerant Douglas‐fir (Pseudotsuga menziesii) and aspen (Populus tremuloides) was sustained or increased in dry scenarios (+4% to +6%). The proportion of burned area where regeneration failed increased in all dry scenarios but never exceeded 20%. Declining tree regeneration and shifts in dominant tree species revealed that changes in forest structure and composition—and not a conversion to non‐forest—are the dominant response to future climate across broad swaths of the simulation landscapes. Our results suggest that postfire reorganization may be widespread during the 21st century and enable forests to persist in a warming climate with more fire.

Shui Feng, J. E. Paguyo

The hierarchical Dirichlet process is a discrete random measure used as a prior in Bayesian nonparametrics and motivated by the study of groups of clustered data. We study the asymptotic behavior of the power sum symmetric polynomials for the vector of weights of the hierarchical Dirichlet process as the concentration parameters tend to infinity. We establish central limit theorems and obtain explicit representations for the asymptotic variances, with the latter clearly showing the impact of the hierarchical structure. These objects are related to the homozygosity in population genetics, the Simpson diversity index in ecology, and the Herfindahl-Hirschman index in economics.

Poroshat Yazdanbakhsh, Mark Anderson, Zhisheng Shuai

We introduce a new quantity known as the network heterogeneity index, denoted by $\mathcal{H}$, which facilitates the investigation of disease propagation and population persistence in heterogeneous environments. Our mathematical analysis reveals that this index embodies the structure of such networks, the disease or population dynamics of patches, and the dispersal between patches. We present multiple representations of the network heterogeneity index and demonstrate that $\mathcal{H}\geq 0$. Moreover, we explore the applications of $\mathcal{H}$ in epidemiology and ecology across various heterogeneous environments, highlighting its effectiveness in determining disease invasibility and population persistence.

Yunzhe Zhou, Giles Hooker

Integral projection models (IPMs) are widely used to study population growth and the dynamics of demographic structure (e.g. age and size distributions) within a population.These models use data on individuals' growth, survival, and reproduction to predict changes in the population from one time point to the next and use these in turn to ask about long-term growth rates, the sensitivity of that growth rate to environmental factors, and aspects of the long term population such as how much reproduction concentrates in a few individuals; these quantities are not directly measurable from data and must be inferred from the model. Building IPMs requires us to develop models for individual fates over the next time step -- Did they survive? How much did they grow or shrink? Did they Reproduce? -- conditional on their initial state as well as on environmental covariates in a manner that accounts for the unobservable quantities that are are ultimately interested in estimating.Targeted maximum likelihood estimation (TMLE) methods are particularly well-suited to a framework in which we are largely interested in the consequences of models. These build machine learning-based models that estimate the probability distribution of the data we observe and define a target of inference as a function of these. The initial estimate for the distribution is then modified by tilting in the direction of the efficient influence function to both de-bias the parameter estimate and provide more accurate inference. In this paper, we employ TMLE to develop robust and efficient estimators for properties derived from a fitted IPM. Mathematically, we derive the efficient influence function and formulate the paths for the least favorable sub-models. Empirically, we conduct extensive simulations using real data from both long term studies of Idaho steppe plant communities and experimental Rotifer populations.

Kohji Hotta, Shunsuke O. Miyasaka, Kotaro Oka et al.

Organismal transparency is an ecologically important trait that can provide camouflage advantages to diverse organisms. Transparent organisms are quite common—especially in oceans. Organismal transparency requires low absorption and scattering of light in the body across multi-scale levels. However, it is still not fully understood how such organisms achieve these requirements. Understanding this process requires multiple approaches from various fields and methods. Here, we offer recent insights on this topic from the viewpoints of evolution, developmental biology, and evaluation methodologies of organismal transparency. We also propose “organismal transparency biology” as a new interdisciplinary field of study. Furthermore, we suggest that tunicates are an ideal model animal for studying in vivo organismal transparency.

H. Patrick Roberts, Lori Erb, Lisabeth Willey et al.

Turtle populations are declining globally, yet limited attention has been directed toward understanding the conservation status of species perceived to be widespread and common. The goal of this study was to contribute to the understanding of the conservation status of the eastern box turtle (Terrapene carolina), a wide-ranging terrestrial generalist, in the northeastern United States (Maine to Virginia) by (1) characterizing relationships between occurrence and anthropogenic land use and (2) estimating the extent of land-use driven habitat impairment for the region. We used a regional dataset of occurrence records combined with pseudo-absences to develop species distribution models to first estimate the potential distribution in the northeastern United States and then predict habitat suitability within that distribution. We observed a strong positive relationship between probability of occurrence and canopy cover (within 180 m) and a strong negative relationship with hay/pasture fields (360 m), cultivated crops (180 m), impervious surface (360 m), and forest loss (since 2000; 1440 m). We estimate that approximately 51% of eastern box turtle habitat in the northeastern United States may be impaired by land use, with the majority of impairment predicted from Pennsylvania and Delaware south to Virginia. This study, in combination with previous long-term studies documenting population declines, suggests that greater attention to the conservation status of the eastern box turtle is warranted.

Chunmei Mao, Junjun Niu

IntroductionThe Yangtze River Delta is where “the Belt and Road” and China’s Yangtze River Economic Belt converge, which plays a crucial strategic location. However, with the demands of economic growth, environmental issues are frequently present in the Yangtze River Delta as a result of human and exploitation of ecological resources, and there is an urgent need to coordinate the relationship between human development and ecology.MethodsThe Yangtze River Delta region is used as the research subject, quantitatively analyzing various ecosystems within the region from three dimensions: ecosystem services value, ecological carrying capacity, and ecological footprint, and analyzing various factors that affect economic and environmental balance. Then calculate eco-compensation and its payment order based on this information, in order to build a foundation for coordinating ecological interests and safeguarding the environment in the Yangtze River Delta region.Results and discussion(1) Jiangsu Province was the main provider of ecosystem services in the Yangtze River Delta; the Yangtze River Delta’s three main ecosystems-waters, forests, and wetlands-accounted for 90% of the ecosystem services valued in the area and must be preserved. (2) The Yangtze River Delta as a whole belonged to an ecological deficit area, showing varying degrees of unsustainable development; In terms of ecological deficits, cultivated land and fossil energy had the worst, and both need to be treated severely. (3) The Yangtze River Delta was a region that paid ecological compensation. The payment order and total amount was 6825.596 billion yuan in Shanghai, 6412.264 billion yuan in Jiangsu, 12088.852 billion yuan in Zhejiang, and 3675.637 billion yuan in Anhui. At the same time, considering the current state of Anhui, the amount of eco-compensation can be appropriately reduced. Finally, recommendations are made based on the findings above, in order to improve the overall ecological benefits of the Yangtze River Delta region and foster ecological integration, all provincial and municipal governments should take reasonable action to reverse the ecological deficit of fossil energy and cultivated land, and also aim to achieve an ecological surplus in both land uses.

Chenfeng Xu, Baojing Wei, Yike Hu et al.

Rapid industrialization and urbanization in canal areas have led to significant conversion in production-living-ecological space (PLES), yielding short-term social-economic benefits but causing serious ecological degradation. However, the complex and dynamic interactions between PLES and ecosystem function remain underexplored, despite their importance for guiding sustainable canal development. Therefore, we analyzed the dynamic changes in PLES and ecosystem service value (ESV) in the Jiangsu section of the Beijing-Hangzhou Grand Canal, along with their interrelationships. By optimizing the ESV evaluation model to incorporate natural, social, and economic factors, we examined the spatiotemporal evolution of PLES and ESV from 2000 to 2020. Finally, we quantified the dynamic response of ESV to PLES using contribution rate factors and identified trade-offs and synergies among ESV indicators. Over the past two decades, ecological space (ES) expanded by only 5.31 %, yet contributing 94.36 % of total ESV growth. Despite fluctuations during 2005–2010, synergies among various ESV types remained largely stable. The regulation service shows the most significant response to the conversion of PLES, with an increase in ES’s ESV of CNY 67.87 billion over 20 years, representing 75.34 % of total ESV growth. Notably, the hydrologic regulation contributes substantially, with an increase in ES’s ESV of CNY 60.87 billion, accounting for 67.57 % of total ESV growth. Our findings provide a scientific basis for the sustainable development and resource management in canal areas.

Nikolay S. Ivanov, Arlan Z. Abilmagzhanov, Oleg S. Kholkin et al.

This article presents the results of the study of the morphological composition of municipal solid waste (MSW) from the landfill of Atyrau city, and the waste’s energy characteristics and presence of microorganisms, including bacteria, fungi and viruses. This study was carried out under a government order to determine the feasibility of recycling accumulated and incoming waste into electricity and its hazard to the environment and the workers involved in handling it. At the moment, there is no MSW recycling in Kazakhstan, which has led to the accumulation of more than 125 million tons of waste with an annual increase of 5 million tons. The research included four major cities (Almaty, Shymkent, Atyrau and Astana), which were selected not only on the basis of population, but also because the cities were located in different climatic zones. Samples were collected at the city landfills: 10 samples with an average distance of 100 m from each other were collected to provide a maximum coverage of both recently received waste and long-time stored waste. The research showed that neither climatic conditions nor the population size had a significant impact on MSW density, the values of which ranged from 120.1 kg/m³ to 145.4 kg/m³, as this indicator directly depends on the quality of life. The mass of the combustible fraction ranged from 39.41% to 54.62% and was mainly represented by plastic, textile and paper waste. The average value for the four cities was 50.30%. The higher calorific value fell in the range of 24.22–30.49 MJ/kg, with an average value of 26.71 MJ/kg. Microbiological studies showed little difference in average composition regardless of climatic conditions. Thus, no sharp differences in MSW composition, its energy characteristics and microbiological composition were found. The results of this study may be useful for optimising MSW recycling and disposal processes, as well as for developing measures to reduce their negative impact on the environment and human health.

Marcin K. Dziuba, Kristina M. McIntire, Kensuke Seto et al.

ABSTRACT The impacts of microsporidia on host individuals are frequently subtle and can be context dependent. A key example of the latter comes from a recently discovered microsporidian symbiont of Daphnia, the net impact of which was found to shift from negative to positive based on environmental context. Given this, we hypothesized low baseline virulence of the microsporidian; here, we investigated the impact of infection on hosts in controlled conditions and the absence of other stressors. We also investigated its phylogenetic position, ecology, and host range. The genetic data indicate that the symbiont is Ordospora pajunii, a newly described microsporidian parasite of Daphnia. We show that O. pajunii infection damages the gut, causing infected epithelial cells to lose microvilli and then rupture. The prevalence of this microsporidian could be high (up to 100% in the lab and 77% of adults in the field). Its overall virulence was low in most cases, but some genotypes suffered reduced survival and/or reproduction. Susceptibility and virulence were strongly host-genotype dependent. We found that North American O. pajunii were able to infect multiple Daphnia species, including the European species Daphnia longispina, as well as Ceriodaphnia spp. Given the low, often undetectable virulence of this microsporidian and potentially far-reaching consequences of infections for the host when interacting with other pathogens or food, this Daphnia–O. pajunii symbiosis emerges as a valuable system for studying the mechanisms of context-dependent shifts between mutualism and parasitism, as well as for understanding how symbionts might alter host interactions with resources.IMPORTANCEThe net outcome of symbiosis depends on the costs and benefits to each partner. Those can be context dependent, driving the potential for an interaction to change between parasitism and mutualism. Understanding the baseline fitness impact in an interaction can help us understand those shifts; for an organism that is generally parasitic, it should be easier for it to become a mutualist if its baseline virulence is relatively low. Recently, a microsporidian was found to become beneficial to its Daphnia hosts in certain ecological contexts, but little was known about the symbiont (including its species identity). Here, we identify it as the microsporidium Ordospora pajunii. Despite the parasitic nature of microsporidia, we found O. pajunii to be, at most, mildly virulent; this helps explain why it can shift toward mutualism in certain ecological contexts and helps establish O. pajunii is a valuable model for investigating shifts along the mutualism-parasitism continuum.

R. Peet, M. Watts

F. Russo, A. Tenore, M. R. Mattei et al.

A multiscale mathematical model describing the genesis and ecology of algal-bacterial photogranules and the metals biosorption on their solid matrix within a sequencing batch reactor (SBR) is presented. The granular biofilm is modelled as a spherical free boundary domain with radial symmetry and a vanishing initial value. The free boundary evolution is governed by an ODE accounting for microbial growth, attachment and detachment phenomena. The model is based on systems of PDEs derived from mass conservation principles. Specifically, two systems of nonlinear hyperbolic PDEs model the growth of attached species and the dynamics of free adsorption sites; and two systems of quasi-linear parabolic PDEs govern the diffusive transport and conversion of nutrients and metals. The model is completed with systems of impulsive ordinary differential equations (IDEs) describing the evolution of dissolved substrates, metals, and planktonic and detached biomasses within the granular-based SBR. All main phenomena involved in the process are considered in the mathematical model. Moreover, the dual effect of metal presence on the formation process of photogranules is accounted: metal stimulates the production of EPS by sessile species and negatively affects the metabolic activities of microbial species. To describe the effects related to metal presence, a stimulation term for EPS production and an inhibition term for metal are included in all microbial kinetics. The model is used to examine the role of the microbial species and EPS in the adsorption process, and the effect of metal concentration and adsorption proprieties of biofilm components on the metal removal. Numerical results show that the model accurately describes the photogranules evolution and ecology and confirm the applicability of algal-bacterial photogranules systems for metal-rich wastewater treatment.

Jesús Dueñas, Iacopo P. Longo, Rafael Obaya

This paper investigates biological models that represent the transition equation from a system in the past to a system in the future. It is shown that finite-time Lyapunov exponents calculated along a locally pullback attractive solution are efficient indicators (early-warning signals) of the presence of a tipping point. Precise time-dependent transitions with concave or d-concave variation in the state variable giving rise to scenarios of rate-induced tracking are shown. They are classified depending on the internal dynamics of the set of bounded solutions. Based on this classification, some representative features of these models are investigated by means of a careful numerical analysis.

Christina M. Burnham, Erin A. McKenney, Kimberly Ange‐van Heugten et al.

Abstract The southern white rhinoceros (Ceratotherium simum simum) faces an uncertain future in the wild due to increased poaching pressure and habitat fragmentation, thus the management of reproductively successful populations is of critical importance. Successful reproductive outcomes in rhinoceros may be mediated by diet and gut microbial diversity; therefore, understanding gut microbial dynamics within and between captive and wild populations may help improve conservation efforts. Accordingly, gut microbiome preservation methods are needed that are practical for in situ field sampling of wild populations. We evaluated the efficacy of 3 different preservation methods over 2 timepoints for stabilizing microbial communities in feces from southern white rhinoceros (n = 10) at the North Carolina Zoo in Asheboro, North Carolina, USA, during July–September 2020 and January–March 2021. Samples were immediately frozen at −80°C, stored in PERFORMAbiome™·GUT (PB) tubes or stored in 95% ethanol at ambient temperatures (to simulate field conditions), and processed after 14 or 230 days post‐collection. We quantitatively compared alpha and beta diversity across microbial communities and identified taxa that were enriched in each treatment group. Samples preserved in 95% ethanol consistently harbored lower Shannon diversity index (SHDI) and Simpson's diversity (SDI) values compared to Frozen and PB samples. This trend was apparent in both Ethanol day‐14 samples (SHDI 4.94; SDI 0.98) versus Frozen day‐14 (SHDI 5.19; W = 518, P < 0.001; SDI 0.99; W = 476, P < 0.001) and PB day‐14 (SHDI 5.15; W = 430, P < 0.01; SDI 0.99; W = 1075, P = 1) samples, and in Ethanol day‐230 samples (SHDI 4.48; SDI 0.97) versus Frozen day‐230 (SHDI 5.18; W = 0, P < 0.05; SDI 0.99; W = 0, P = 0.032) and PB day‐230 (SHDI 5.23; W = 0, P < 0.05; SDI 0.99; W = 0, P = 0.032) samples. Ethanol day 230 samples differed (P < 0.05) from all other treatments in both alpha and beta diversity indices. Notably, frozen and PB preservation methods maintained compositionally similar microbial communities across both time points. Our results indicate that PB tubes stored at ambient temperatures perform similarly to freezing at −80°C, highlighting their utility for microbiome fieldwork applications. Identifying optimal and versatile microbiome preservation techniques will enable future studies of the gut microbiome in reproductively‐successful wild populations, an effort central to conservation efforts in the southern white rhinoceros and other threatened species.