Effects Of Patch Size Research Articles

Patch spatial attributes and time to disturbance affect the emergence of source local populations within ephemeral habitats

Understanding the demography of local populations within ephemeral habitat patches is crucial for effective local (site-based) conservation management in spatially and temporally heterogeneous environments. Evidence suggests that species persisting in networks of ephemeral patches often exhibit source-sink dynamics, where certain local populations act as temporary sources at some time between initial colonization and patch disappearance due to disturbance. Here we present an individual-based demographic model inspired by Cabrera voles (Microtus cabrerae) in dynamic agricultural mosaics to test the hypothesis that the emergence of a source local population within an ephemeral habitat patch is largely driven by the combined effects of the patch spatial attributes (size, internal quality and connectivity to other hypothetical patches) and the time to disturbance (i.e. the patch lifespan). We focused on two key emergent demographic metrics quantifying the source-sink status of local populations based on their self-sustainability and potential contribution to other patches. We used sensitivity analyses to estimate the strength of linear associations between these metrics and the patch spatial attributes, and to quantify the main and interaction effects across different patch lifespans since initial colonization. Our model revealed that considerable spatial and temporal variation may emerge in local populations’ source-sink status based on differences in patch size, internal quality, connectivity, and lifespan. According to predictions, patch internal quality correlated positively with local population self-sustainability and potential contribution to other patches, though the strength of these relationships was mostly relevant only after about three vole generation times (ca. one year) since initial colonization, and only in combination with the positive effects of patch size and connectivity. Accordingly, results also supported the prediction that the emergence of a temporary source local population is conditional to the longevity of the habitat patch, with short patch lifespans (less than about three vole generation times) greatly limiting local population self-sustainability and potential contribution to other patches. While empirical testing is needed to confirm these findings, our study strengthens the view that local management efforts focusing on reducing or mitigating disturbance (e.g. severe droughts, human farming activities) at large and well-connected high-quality patches will likely promote the occurrence of temporary source local populations, which should be crucial for long-term species persistence over larger spatial scales.

Research on the Inversion of Chlorophyll-a Concentration in the Hong Kong Coastal Area Based on Convolutional Neural Networks

Chlorophyll-a (Chl-a) concentration is a key indicator for assessing the eutrophication level in water bodies. However, accurately inverting Chl-a concentrations in optically complex coastal waters presents a significant challenge for traditional models. To address this, we employed Sentinel-2 MSI sensor data and leveraged the power of five machine learning models, including a convolutional neural network (CNN), to enhance the inversion process in the coastal waters near Hong Kong. The CNN model demonstrated superior performance with on-site data validation, outperforming the other four models (R2 = 0.810, RMSE = 1.165 μg/L, MRE = 35.578%). The CNN model was employed to estimate Chl-a concentrations from images captured over the study area in April and October 2022, resulting in the creation of a thematic map illustrating the spatial distribution of Chl-a levels. The map indicated high Chl-a concentrations in the northeast and southwest areas of Hong Kong Island and low Chl-a concentrations in the southeast facing the open sea. Analysis of patch size effects on CNN model accuracy indicated that 7 × 7 and 9 × 9 patches yielded the most optimal results across the tested sizes. Shapley additive explanations were employed to provide post-hoc interpretations for the best-performing CNN model, highlighting that features B6, B12, and B8 were the most important during the inversion process. This study can serve as a reference for developing machine learning models to invert water quality parameters.

Lizard abundance in forest fragments: effects of patch size, patch shape, thermoregulation, and habitat quality

Abstract The effects of forest fragmentation on ecosystems are pervasive, but little is known about the factors that influence lizard abundance in fragmented landscapes. We studied the roles of patch size and shape, thermal quality, and refuge availability as predictors of the relative abundance of Psammodromus algirus lizards at deciduous or evergreen forest fragments surrounded by cereal fields. Relative abundance, based on time-controlled counts, decreased from the northeast (dominated by deciduous habitat) to the southwest (with a higher cover of croplands, and dominated by evergreen habitat). Refuge availability was correlated with this gradient, decreasing from the northeast to the southwest and being larger in deciduous than in evergreen fragments. After controlling for the effects of this environmental variation, lizard abundance increased as perimeter-to-area ratio (P/A) decreased (and consequently as fragment size increased). Although the effects of thermal quality as such were negligible, our results can be interpreted in the light of thermoregulatory requirements; given the low temperatures available at shaded locations, lizards should actively select sunlit patches while they try to minimize predation risk by basking as close as possible to the nearest refuge. Although use of fragment edges as basking sites is expected to increase with P/A ratio, lizards should avoid using them as basking sites, because both exposure to predators and risk of overheating are expected to be higher at edges and croplands than inside fragments. We conclude that long and narrow forest strips with high P/A ratios could act as ecological traps rather than as dispersion-promoting corridors.

Do remnant forest patches provide microclimate buffering? A case study from Sri Lanka

Tropical forests have declined in extent considerably owing to large scale deforestation for providing land for multiple uses, and this has reduced their collective capacity to provide many important ecological functions. In the present study, conducted in the tropical island of Sri Lanka, we focus on remnant patches of two common and co-occurring vegetation types in the dry zone, Dry Mixed Evergreen Forest and Scrub Forest, to test (a) whether small remnant forest patches facilitate microclimate buffering and, if so, (b) whether the two forest types differ in terms of their potential to buffer the microclimate, and (c) whether the extent of canopy cover influences the microclimate buffering capacity. Co-occurring Grasslands were used as reference habitats. We used multiple temperature, relative humidity and vapour pressure deficit related metrics, and showed that Dry mixed Evergreen Forest and Scrub Forest had significant microclimate buffering potential, the latter to a lesser extent than the former (Dry mixed Evergreen Forest > Scrub Forest). These results are noteworthy, given that the patches of both forest types were relatively small (mean ± standard deviation: Dry Mixed Evergreen Forest = 0.63 ± 0.13 km2 and Scrub Forest = 0.10 ± 0.07 km2), intermixed and scattered across the same landscape. The study also showed that, after controlling for effects of patch size, the extent of canopy cover had a significant impact on most of the microclimate metrics. The impact of patch size on microclimate metrics was less pronounced. These findings highlight the need for conserving remnant forest patches, especially of the Dry Mixed Evergreen Forest, as refuges of biodiversity, particularly in the context of tropical forests in developing countries facing severe threats of deforestation.

Shrub and patch size of moss crusts regulate soil multifunctionality in a temperate desert of Central Asia

AbstractThe shrub and patch size of moss crusts can significantly affect plant and soil nutrients. The effects and relationships of shrubs and moss crusts on soil multifunctionality are unclear. This study aimed to understand the spatial heterogeneity of soil multifunctionality in moss crust patches and shrubs. Soil organic carbon, nutrient, and enzyme activities under moss crust patches were measured. Interestingly, the soil polyphenol oxidase (PPO) and peroxidase (POD) activities, carbon‐related soil multifunctionality index (C‐SMF), nitrogen‐related soil multifunctionality index (N‐SMF), phosphorus‐related soil multifunctionality index (P‐SMF), and soil multifunctionality index (SMF) increased with increasing patch size in moss crusts. The patch size of moss crusts had no significant effect on the C‐SMF, N‐SMF, P‐SMF, and SMF under the shrub. The soil C‐SMF, N‐SMF, P‐SMF, and SMF under shrubs were significantly higher than that in exposed areas (EAs). The soil PPO, POD, N‐SMF, P‐SMF, and SMF under dead shrubs were significantly higher than those under living shrubs and in EAs. Evaluation and composition analysis of C‐SMF, N‐SMF, and P‐SMF indicated that moss crust promotes the increase of P‐SMF, and that shrub promotes the increase of C‐SMF and N‐SMF. Moss crust patches mainly affected phosphorus functionality, increasing phosphorus cycling. Shrub promotes soil carbon and nitrogen functionality. This study elucidates the effect of moss crust patch size on soil multifunctionality influenced by shrub growth in desert ecosystems and provides further new insights into the soil processes and functions. Results are beneficial for the comprehensive utilization of fertile islands and its enhancement of beneficial ecological functions, such as maintaining soil nutrition, quality, health, and vegetation restoration, and lay a foundation for future research on nutrient absorption and utilization between mosses and shrubs.

A parametric study on patch repaired quasi‐isotropic laminate in high‐velocity impact environment: Experimental and numerical investigation

AbstractIn this work, the post‐repair behavior of a quasi‐isotropic laminate was studied in a high‐velocity impact environment. The composite laminates were repaired using an external bonded patch repair procedure. Impact tests were performed to understand the effect of patch size and the result of filling the damaged region with a neat epoxy and hardener mixture. Two different size square patches, such as 30 and 50 mm, were used to analyze the effect of patch size. A continuum damage mechanics‐based model was developed and incorporated into a finite element model interface to estimate the optimum patch size and patch stacking sequence for the impact environment. In the finite element model, the intralaminar failure criteria were implemented using the ABAQUS‐VUMAT user subroutine, and the interlaminar failure criteria were implemented using the inbuilt cohesive contact properties. The 30 mm patch with resin filled in the damaged region performed better than the other combination patches. Also, placing 45° plies toward the outer layer of the patches showed lower damage compared to the patches in which 45° plies were placed at the inner surfaces.Highlights Post‐repair impact behavior of repaired laminates was examined. Impact of patch dimension and resin filling in the damaged area was analyzed. A 3‐D finite element model was developed to optimize patch parameters. Continuum damage mechanics model has been incorporated with VUMAT subroutine. Interface between lamina has been modeled using cohesive contact.

Mean landscape‐scale incidence of species in discrete habitats is patch size dependent

AbstractAimA pervasive negative relationship between the species richness of an assemblage and the mean global range size of the species it contains has recently been identified. Here, we test for an effect of habitat patch size on the mean landscape‐scale incidence (estimating local range size) of constituent species independent of variation in richness.LocationGlobal.Time PeriodContemporary.Major Taxa StudiedVarious.MethodsWe devised a new standardized patch‐scale metric, Mean Species Landscape‐scale Incidences per Patch (MSLIP). Positive values indicate a patch contains more widespread (high‐incidence) species than expected relative to their frequency in the landscape; negative values indicate the presence of more narrow‐range (low‐incidence) species. For 202 metacommunity datasets (archipelagos, habitat islands and fragments) we regressed MSLIP on patch size, testing four hypotheses: (i) no effect (zero slope), (ii) more widespread species in smaller patches (negative slope), (iii) more narrow‐range species in smaller patches (positive slope), (iv) a composite effect (curvilinear/unimodal).ResultsThere was a generally negative curvilinear relationship between MSLIP and patch size, consistent with smaller and larger patches respectively containing more high‐ and low‐incidence species than expected. At intermediate patch sizes, mean species incidence approximates that of the overall landscape. Relative richness mediated this relationship; species‐rich sites of any size increasingly favoured low‐incidence species, species‐poor sites high‐incidence species. Results were consistent for taxonomic groups, and metacommunity types, except aquatic habitat islands.Main ConclusionsThe dependence of mean species incidence on both patch size and relative richness has implications for biodiversity and community assembly theory, or when seeking to understand ecological processes sensitive to species composition (e.g., ecosystem functioning, trophic web structures). We propose the ‘patch size where the MSLIP regression intersects zero’ as a benchmark distinguishing smaller from larger patches, with the expectation small patches preferentially support more high‐incidence and large patches more low‐incidence species.

Experimental and simulation study on bonded repaired low-velocity impact of carbon fiber reinforced plastic laminates for rail vehicles

In this study, a high-strength carbon fiber reinforced composite laminate for rail vehicles was machined as a perforated sample and repaired by bonding a patch of the same material. The mechanical response of the repaired laminate to a low-velocity impact with energies of 25J and 30J was investigated through experiments and simulations with variations in patch thickness, size radius, and off-axis angle. The finite element simulation model was established in Abaqus/Explicit. The model integrated the progressive damage model based on the 3D-Hashin failure criterion, which can simulate the intralaminar damage of the fiber and the matrix. The cohesive zone model was used to simulate the delamination damage. According to the finite element analysis results, the mechanism and process of impact damage of the repaired laminates were analyzed. Based on the validated finite element model, the effect of patch size, thickness and off-axis angle on impact response was investigated. Patch radius reduced to 15 mm or thickness reduced to 2.1 mm can still resist low-velocity impacts with an energy of 30 J. Although the off-axis angle of the patch had little effect on the impact response of the repaired laminate, an off-axis angle of 90° was effective in suppressing delamination damage within the patch.

The combined effects of habitat fragmentation and life history traits on specialisation in lichen symbioses

Abstract Interactions between organisms are determined by life‐history traits. Ecological strategies regarding species specialisation range from generalist to highly specialised relationships. Although it is expected that habitat fragmentation's effect on species abundance and survival depends on their degree of specialisation and life‐history traits, few studies have delved into the interplay between interaction specialisation, life‐history traits and habitat fragmentation. Here, we investigate the combined effect of habitat fragmentation, forest structure and life‐history traits (growth form and reproductive mode) on the specialisation of lichen‐forming fungi (mycobionts) toward their photosynthetic partners (photobionts) in lichen symbioses. We studied mycobiont specialisation in epiphytic lichen communities present in 10 fragments of Quercus rotundifolia forest embedded in an agricultural matrix. Both mycobionts and photobionts were identified DNA barcoding and mycobiont specialisation was measured through interaction parameters calculating the relative number of interactions (normalised degree; ND) and the specialisation of each species based on its discrimination from a random selection of partners (d'). Phylogenetic generalised linear mixed models were used to analyse the effect of patch size as well as the life history traits growth form (crustose, foliose, fruticose) and reproduction mode (sexual vs. asexual) on mycobiont specialisation. Both mycobiont and photobiont richness along the patch size gradient followed a hump‐back pattern, which was more pronounced in photobionts. Mycobionts forming crustose thalli established the largest number of interactions. Mycobiont specialisation (d') was larger for fruticose and foliose forms and species with vegetative reproduction. Along the gradient of fragment size, the relative number of interactions decreased and the specialisation of mycobionts with vegetative reproduction increased. Synthesis. The study of mycobiont specialisation towards their photobionts in epiphytic lichen communities in a fragmented Mediterranean forest revealed a complex interaction between species' life history traits and habitat fragmentation. In particular, this interplay had a significant impact on the specialisation of mycobionts. The results show the ability of some species to modulate their specialisation according to habitat conditions, suggesting that some species may be more resilient to abiotic changes than expected.

A vehicle-bridge interaction model considering contact patch size and vehicle self-generated excitation – A theoretical study

This paper presents an improved theoretical damped single-axle vehicle-bridge dynamic interaction model to consider the effect of the contact patch size and motor-induced vehicle excitation. The contact patch issue is critical as it determines the minimum time step for simulation and maximum identifiable frequency, while the inclusion of the motor-induced vehicle excitation benefits the design of autonomous self-driven rather than towed vehicles. Estimations of the contact patch size for both the pneumatic tire and solid wheel scenarios are discussed. The contact patch responses, which degenerate into contact point responses when the contact patch size is assumed to be infinitely small, were derived for the first time both from the vehicle and bridge responses to confirm their equivalence. The minimum time step, which determines maximum identifiable frequency but is arbitrarily chosen in literature, is proposed to be determined by the vehicle speed and contact patch length. The procedures to extract multiple bridge triad information including natural frequencies, mode shapes, and damping ratios from the vehicle responses are also presented. Based on extensive parametric analyses, the sinusoidal vehicle excitation becomes more prominent as its amplitude and/or frequency increase and may overshadow the analysis of bridge frequencies of interest. The vehicle acceleration leads to a more accurate extraction of bridge mode shapes and damping ratios than the vehicle displacement since the displacement is dominated by the fundamental mode of bridge vibration. The damping ratio extraction shows an average error of 0.28% from the instantaneous amplitude of the vehicle acceleration signal.

The importance of patch shape at threshold occupancy: functional patch size within total habitat amount.

The habitat amount hypothesis (HAH) stresses the importance of total patch amount over the size of individual patches in determining species richness within a local landscape. However, the absence of some species from patches too small to contain a territory would be inconsistent with the HAH. Using the association of territory size with body size and the circle as optimal territory shape, we tested several HAH predictions of threshold patch occupancy and richness of 19 guilds of primarily insectivorous breeding birds. We characterized 16 guild-associated patch types at high spatial resolution and assigned one type to each guild. We measured functional patch size as the largest circle that fit within each patch type occurring in a local landscape. Functional patch size was the sole or primary predictor in regression models of species richness for 15 of the 19 guilds. Total patch amount was the sole or primary variable in only 2 models. Quantifying patch size at high resolution also demonstrated that breeding birds should be absent from patches that are too small to contain a territory and larger species should occur only in larger patches. Functional patch size is a readily interpretable metric that helps explain the habitat basis for differences in species composition and richness between areas. It provides a tool to assess the combined effects of patch size, shape and perforation on threshold habitat availability, and with total patch amount can inform design and/or evaluation of conservation, restoration or enhancement options for focal taxa or biodiversity in general.

Using high-throughput sequencing to investigate summer truffle consumption by chipmunks in relation to retention forestry

Intensive management of forests for wood modifies forest biodiversity, affecting the composition of plant and animal communities as well as microorganisms such as bacteria and fungi. Ectomycorrhizal fungi (EMF) form mutualistic relationships with trees, but there is evidence that the abundance and diversity of EMF declines under intensive forest management. The dispersal of some EMF, including that of truffles, depends on small mammals consuming their fruiting bodies and dispersing spores through feces. To better understand provisioning of this ecosystem service within intensively managed forests, we applied high-throughput, DNA amplicon sequencing to scat collected from Townsend’s chipmunks (Neotamias townsendii) inhabiting retention patches in recently clearcut-conifer stands. Across two summers, we collected 165 chipmunk scat samples from 43 clearcut-conifer stands in the Pacific Northwest (USA). We identified 81 truffle species representing 16 families, which included many rare and uncommon taxa. Retention patch sizes varied from 9 to 222 trees (0.002–0.83 ha) but we did not detect an effect of retention patch size on the richness of truffles in chipmunk scat samples. However, truffle richness was slightly higher in scat samples collected from chipmunks in retention patches compared to individuals sampled in adjacent clearcuts. Furthermore, the abundance of certain truffle species in chipmunk scat varied in relation to retention patch size and location (riparian or upland), suggesting retention forestry practices may influence truffle community composition. Throughout the sampling season, we detected a 44% decline in truffle species richness and a significant reduction in abundance (i.e., sequence reads) for > 50% of common truffle taxa. Our application of high-throughput sequencing of scat effectively captured variation in truffle species consumption by chipmunks. Our results confirm that common small mammals play an important role in the dispersal of EMF across recently logged forests (<8 years since harvest) and indicate that retaining relatively small (∼10 tree) green-tree patches may promote truffle dispersal by providing small mammal habitat.

Vibration control of a cantilever plate immersed in water using shunted piezoelectric patches

Minimizing structural vibrations is an important engineering requirement in many applications. This study theoretically investigates the vibration control of an in-water cantilever plate using piezoelectric patches and resonant shunt circuits (including a resistance R and an inductance L in series or parallel). To do this, an analytical model for predicting the point-forced vibration response of a fluid-loaded cantilever plate with two piezoelectric patches is developed. The electromechanical coupling factor and optimum values for R and L are then estimated by considering the dynamics of the system in short-circuit and open-circuit conditions. The effect of piezoelectric patch size, location and electromechanical properties on the vibration response of the plate is also investigated through numerical examples. The results from this study show that optimized piezoelectric patches could provide a significant vibration reduction for underwater applications.

Moss patch size as a factor profoundly influencing soil nutrient characteristics and multifunctionality of temperate desert in Central Asia

Soil nutrients in desert ecosystems are influenced by various factors, and the presence of moss crust cover plays a significant role in determining the nutritional content of the surface soil. Moss crusts are distributed as patches within desert ecosystems, creating micro-ecosystems. However, the distribution pattern of soil nutrients under moss crust cover and the impact of patch size on soil nutrient content remain unclear. In this study, we assessed the patch size of mosses in field sites within the Gurbantünggüt Desert and investigated the content of total carbon (C), total nitrogen (N), total phosphorus (P), organic carbon (OC), ammonium (NH4+-N), nitrate (NO3–-N), and available phosphorus (AP) in both surface soil and sub surface soil. We employed linear and structural equation models to examine the regulatory effect of moss crust patch size on soil nutrient content. Our findings revealed that the C and N contents were significantly higher in the surface soil compared to the sub surface soil, while the AP content was significantly higher in the sub surface soil than in the surface soil. Additionally, a significant negative correlation was observed between the N content and patch area of the topsoil in 83% of the sample sites. Climate, soil properties, and moss patch size collectively influenced the multifunctionality of both surface soil and sub surface soil. Climatic factors exerted a greater impact on the surface soil, while soil properties and moss patch size had a stronger influence on the sub surface soil. These findings emphasize the variability in nutrient characteristics between the surface and sub surface soils of biocrusts, highlighting the influence of crust patch size on the nutrient characteristics and functions of desert soils. These insights have practical implications for land management and conservation strategies in arid regions, providing valuable knowledge for sustainable resource utilization and environmental preservation.

Risk factors for Lyme disease resulting from residential exposure amidst emerging Ixodes scapularis populations: A neighbourhood-level analysis of Ottawa, Ontario.

Lyme disease is an emerging health threat in Canada due to the continued northward expansion of the main tick vector, Ixodes scapularis. It is of particular concern to populations living in expanding peri-urban areas where residential development and municipal climate change response impact neighbourhood structure and composition. The objective of this study was to estimate associations of socio-ecological characteristics with residential Lyme disease risk at the neighbourhood scale. We used Lyme disease case data for 2017-2020 reported for Ottawa, Ontario to determine where patients' residential property, or elsewhere within their neighbourhood, was the suspected site of tick exposure. Cases meeting this exposure definition (n = 118) were aggregated and linked to neighbourhood boundaries. We calculated landscape characteristics from composited and classified August 2018 PlanetScope satellite imagery. Negative binomial generalized linear models guided by a priori hypothesized relationships explored the association between hypothesized interactions of landscape structure and the outcome. Increases in median household income, the number of forest patches, the proportion of forested area, forest edge density, and mean forest patch size were associated with higher residential Lyme disease incidence at the neighbourhood scale, while increases in forest shape complexity and average distance to forest edge were associated with reduced incidence (P<0.001). Among Ottawa neighbourhoods, the combined effect of forest shape complexity and average forest patch size was associated with higher residential Lyme disease incidence (P<0.001). These findings suggest that Lyme disease risk in residential settings is associated with urban design elements. This is particularly relevant in urban centres where local ecological changes may impact the presence of emerging tick populations and how residents interact with tick habitat. Further research into the mechanistic underpinnings of these associations would be an asset to both urban development planning and public health management.

Patch size and connectivity predict remnant habitat occupancy by an endangered wetland specialist, the salt marsh harvest mouse

ContextThe area-isolation paradigm of metapopulation theory predicts that larger and more connected patches have a higher probability of occupancy. Although it may be too simplistic for generalist terrestrial mammals, the area-isolation paradigm may be an effective tool for assessing patch-occupancy for habitat specialists.ObjectivesWe tested predictions of the area-isolation paradigm for the endangered salt marsh harvest mouse (Reithrodontomys raviventris), a habitat specialist living in highly fragmented salt marsh habitat in the San Francisco Estuary (California, USA).MethodsWe surveyed for salt marsh harvest mice at 47 marsh patches throughout their range using a non-invasive genetic survey technique. We used occupancy modeling to estimate the effects of patch size, patch connectivity, matrix urbanization, and several habitat characteristics on occupancy probabilities. We evaluated occupancy at both coarse (e.g., among patches) and fine (e.g., within patches) spatial scales.ResultsPatch size, connectivity, and matrix urbanization had significant effects on patch-occupancy. Within patches, occupancy was positively related to the presence of high-tide escape vegetation. Our data also revealed the extirpation of several geographically distinct populations, consistent with expectations due to reduced patch sizes and connectivity over the past century.ConclusionsPatterns of salt marsh harvest mouse patch-occupancy were consistent with the area-isolation paradigm. In addition, our models provide important guidelines of patch size and connectivity that can inform habitat conservation and restoration for this endangered species. Specifically, our data suggests that selecting restoration sites that are well-connected may be more beneficial than selecting larger, isolated sites.

Landscape experiments unlock relationships among habitat loss, fragmentation, and patch-size effects.

Habitat loss is often considered the greatest near-term threat to biodiversity, while the impact of habitat fragmentation remains intensely debated. A key issue of this debate centers on the problem of scale-landscape or patch-at which to assess the consequences of fragmentation. Yet patterns are often confounded across scales, and experimental designs that could solve this scaling problem remain scarce. We conducted two field experiments in 30 experimental landscapes in which we manipulated habitat loss, fragmentation, and patch size for a community of four insect herbivores that specialize on the cactus Opuntia. In the first experiment, we destroyed 2088 Opuntia patches in either aggregated or random patterns and compared the relative effects of landscape-scale loss and fragmentation to those of local patch size on species occurrence. This experiment focused on manipulating the relative separation of remaining patches, where we hypothesized that aggregated loss would disrupt dispersal more than random loss, leading to lower occurrence. In the second experiment, we destroyed 759 Opuntia patches to generate landscapes that varied in patch number and size for a given amount of habitat loss and assessed species occurrence. This experiment focused on manipulating the subdivision of remaining habitat, where we hypothesized that an increase in the number of patches for a given amount of loss would lead to negative effects on occurrence. For both, we expected that occurrence would increase with patch size. We find strong evidence for landscape-scale effects of habitat fragmentation, with aggregated loss and a larger number of patches for a given amount of habitat loss leading to a lower frequency of patches occupied in landscapes. In both experiments, occurrence increased with patch size, yet interactions of patch size and landscape-scale loss and fragmentation drove species occurrence in patches. Importantly, the direction of effects were consistent across scales and effects of patch size were sufficient to predict the effects of habitat loss and fragmentation across entire landscapes. Our experimental results suggest that changes at both the patch and landscape scales can impact populations, but that a long-standing pattern-the patch-size effect-captures much of the key variation shaping patterns of species occurrence.

Effects of Variation in Tamarix chinensis Plantations on Soil Microbial Community Composition in the Middle Yellow River Floodplain

Floodplains have important ecological and hydrological functions in terrestrial ecosystems, experience severe soil erosion, and are vulnerable to losing soil fertility. Tamarix chinensis Lour. plantation is the main vegetation restoration measure for maintaining soil quality in floodplains. Soil microorganisms are essential for driving biogeochemical cycling processes. However, the effects of sampling location and shrub patch size on soil microbial community composition remain unclear. In this study, we characterized changes in microbial structure, as well as the factors driving them, in inside- and outside-canopy soils of three patch sizes (small, medium, large) of T. chinensis plants in the middle Yellow River floodplain. Compared with the outside-canopy soils, inside-canopy had higher microbial phospholipid fatty acids (PLFAs), including fungi, bacteria, Gram-positive bacteria (GP), Gram-negative bacteria (GN), and arbuscular mycorrhizal fungi. The ratio of fungi to bacteria and GP to GN gradually decreased as shrub patch size increased. Differences between inside-canopy and outside-canopy soils in soil nutrients (organic matter, total nitrogen, and available phosphorus) and soil salt content increased by 59.73%, 40.75%, 34.41%, and 110.08% from small to large shrub patch size. Changes in microbial community composition were mainly driven by variation in soil organic matter, which accounted for 61.90% of the variation in inside-canopy soils. Resource islands could alter microbial community structure, and this effect was stronger when shrub patch size was large. The results indicated that T. chinensis plantations enhanced the soil nutrient contents (organic matter, total nitrogen, and available phosphorus) and elevated soil microbial biomass and changed microbial community composition; T. chinensis plantations might thus provide a suitable approach for restoring degraded floodplain ecosystems.

Effects of Patchwise Sampling Strategy to Three-Dimensional Convolutional Neural Network-Based Alzheimer’s Disease Classification

In recent years, the rapid development of artificial intelligence has promoted the widespread application of convolutional neural networks (CNNs) in neuroimaging analysis. Although three-dimensional (3D) CNNs can utilize the spatial information in 3D volumes, there are still some challenges related to high-dimensional features and potential overfitting issues. To overcome these problems, patch-based CNNs have been used, which are beneficial for model generalization. However, it is unclear how the choice of a patchwise sampling strategy affects the performance of the Alzheimer's Disease (AD) classification. To this end, the present work investigates the impact of a patchwise sampling strategy for 3D CNN based AD classification. A 3D framework cascaded by two-stage subnetworks was used for AD classification. The patch-level subnetworks learned feature representations from local image patches, and the subject-level subnetwork combined discriminative feature representations from all patch-level subnetworks to generate a classification score at the subject level. Experiments were conducted to determine the effect of patch partitioning methods, the effect of patch size, and interactions between patch size and training set size for AD classification. With the same data size and identical network structure, the 3D CNN model trained with 48 × 48 × 48 cubic image patches showed the best performance in AD classification (ACC = 89.6%). The model trained with hippocampus-centered, region of interest (ROI)-based image patches showed suboptimal performance. If the pathological features are concentrated only in some regions affected by the disease, the empirically predefined ROI patches might be the right choice. The better performance of cubic image patches compared with cuboidal image patches is likely related to the pathological distribution of AD. The image patch size and training sample size together have a complex influence on the performance of the classification. The size of the image patches should be determined based on the size of the training sample to compensate for noisy labels and the problem of the curse of dimensionality. The conclusions of the present study can serve as a reference for the researchers who wish to develop a superior 3D patch-based CNN model with an appropriate patch sampling strategy.

Carbon storages and sequestration potentials in remnant forests of different patch sizes in northern Ethiopia: an implication for climate change mitigation

Abstract Background Forests provide various ecosystem services. They are natural capitals that enhance nature to regulate itself via carbon sinks. However, anthropogenic and natural factors have altered their CO2 sequestration and carbon storage potentials. This study is aimed for examining the effect of patch size and biomass extraction on carbon stocks in northern Ethiopia. A total of 61 sample plots measuring 20 m × 20 m size each (0.04 ha) had been systematically assigned on patches classified into three size categories. However, the numbers of plots taken per patch were different with their sizes. Moreover, stump density has been computed at each plot to estimate the difference in the level of disturbance among patches. Carbon stocks had been estimated via models previously developed. One-way ANOVA was used to examine a variation in carbon stocks and sequestration potentials. Besides, a linear regression analysis was discretely done to examine the relationship between patch sizes, disturbance level, and carbon stocks. Results The overall aboveground biomass (ton ha−1) for the studied patches was 2059.13. There was a statistically significant variation in carbon stocks (ton ha−1) among patch size categories. The mean levels of disturbance ranges from 10.83% ± 1.30 to 30.8% ± 4.04. However, statistically significant difference in the level of disturbance was observed between large and small patch size categories, respectively (p &lt; 0.05). Besides, a regression analysis confirmed a significant and negative relationship between patch size and patch disturbances (R2 = 0.65, p &lt; 0.05). However, significant positive relation between carbon stocks (ton ha−1) and patch size (R2 = 0.53, p &lt; 0.05) had observed. Conclusions In general, patch size and biomass extinction significantly influenced carbon stocks and CO2 sequestration potentials of forests. Consequently, with the pressing need to mitigate the effects of rising atmospheric CO2, maximizing carbon storage in the forest ecosystem is increasingly considered a viable management strategy. Therefore, disturbed land restoration, increasing forest patch size, sustainable management, and conservation of the existing remnant forest patch is needed to enhance carbon stocks and CO2 sequestration potentials.