scholarly journals Spatiotemporal Patterns and Mechanisms of Chinese Tallowtree (Triadica sebifera) Spread along Edge Habitat in a Coastal Landscape, Mississippi, USA

2018 ◽  
Vol 11 (3) ◽  
pp. 117-126 ◽  
Author(s):  
Zhaofei Fan ◽  
Shaoyang Yang ◽  
Xia Liu
Keyword(s):  
Seed Dispersal ◽  
Negative Binomial ◽  
Seedling Recruitment ◽  
Light Availability ◽  
Spatiotemporal Patterns ◽  
Tree Age ◽  
Triadica Sebifera ◽  
Factors Affecting ◽  
Edge Habitat ◽  
Dispersal Mechanism

AbstractChinese tallowtree [Triadica sebifera(L.) Small] has reached unprecedented prevalence in coastal landscapes in the Gulf of Mexico, especially along edge habitat with low competition and abundant resource (e.g., light) availability. This study investigated the spatiotemporal patterns and mechanisms ofT. sebiferaspread along roadways and fire lines.Triadica sebiferaindividuals and landscape and community features were surveyed in equally spaced, spatially mapped plots. AllT. sebiferaindividuals were felled to determine tree age and status (seed trees or non-seed bearing trees), andT. sebiferaseed and seedling (≤2 yr old) densities and community and landscape features (over- and understory conditions, distance to seed trees) were measured. A zero-inflated negative binomial model was used to evaluate factors affectingT. sebiferaseed dispersal and seedling recruitment contributing to the observed spatiotemporal patterns. Introduced into the Grand Bay National Wildlife Refuge around 30 yr ago,T. sebiferatrees distribute in clustered patterns along roadways and fire lines and exhibit an exponential growth in density. HighT. sebiferaseed and seedling densities mainly occurred in sites that are ≤250 m from seed trees or have sparse overstory and high understory grass/herb coverage. With respect to the avian seed dispersal mechanism, the spatiotemporal patterns ofT. sebiferaspread along roadways and fire lines could be simply characterized by using landscape and community features that influence avian behaviors, including distance to seed trees, overstory tree density, and ground grass/herb coverage.

scholarly journals Effects of Prescribed Fire, Site Factors, and Seed Sources on the Spread of Invasive Triadica sebifera in a Fire-Managed Coastal Landscape in Southeastern Mississippi, USA

Forests ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 175 ◽  
Author(s):  
Shaoyang Yang ◽  
Zhaofei Fan ◽  
Xia Liu ◽  
Andrew Ezell ◽  
Martin Spetich ◽  
...  
Keyword(s):  
Seed Dispersal ◽  
Prescribed Fire ◽  
Negative Binomial ◽  
Marked Point ◽  
Pair Correlation ◽  
Management Tool ◽  
Simple Random Sample ◽  
Point Pattern ◽  
Site Factors ◽  
Triadica Sebifera

In the Gulf of Mexico coastal region, prescribed fire has been increasingly used as a management tool to restore declining native ecosystems, but it also increases the threat posed by biological invasion, since the treated sites are more susceptible to invasive species such as Chinese tallow (Triadica sebifera). We chose Mississippi Sandhill Crane National Wildlife Refuge (MSCNWR), a fire-managed landscape, to examine the potential effect of prescribed fire and landscape/community features on tallow invasion and spread. We took a complete survey of roadways and fire lines for tallow and measured a systematic sample of 144 10 × 3 m2 rectangular plots along two selected roadways and a simple random sample of 56 0.04-ha circular plots across burn units. We used pair correlation function for marked point pattern data, zero-inflated negative binomial models for count data, as well as multivariate Hotelling’s T2 test, to analyze the effect of prescribed fire and landscape/community characteristics on tallow invasion and spread along habitat edges and into interiors. Our results show that tallow spread along habitat edges and into interiors in a spatially clustered pattern. Tallow invasion risk decreases with the distance to seed trees and shrub coverage, and with the time since last fire if seed trees are outside the effective seed dispersal range (~300 m), but increases with the time since last fire if seed trees are within the effective seed dispersal range. Tallow seedling (≤2 years old) densities increase with the time since last fire and with increasing overstory tree basal area, but decrease with the distance to seed trees. Tallow-invaded interior plots have significantly shorter mean fire return intervals (2.7 years), lower shrub coverage (8.6%), and are closer to edges (20.3 m) than non-invaded plots (4.3 years, 18.4%, 167.6 m, respectively).

Systemic Determinants in Surgery: Nonclinical Factors Affecting Time to Operation for Incarcerated Ventral Hernias

2021 ◽  
pp. 000313482110111
Author(s):  
David E. Wang ◽  
Paul J. Chung ◽  
Rafael Barrera ◽  
Gene F. Coppa ◽  
Antonio E. Alfonso ◽  
...  
Keyword(s):  
Operating Room ◽  
Negative Binomial ◽  
Private Insurance ◽  
Negative Binomial Regression ◽  
Outcome Variable ◽  
Hospital Size ◽  
Factors Affecting ◽  
Binomial Regression ◽  
Comorbidity Status ◽  
Ventral Hernias

Introduction We explore nonclinical factors affecting the amount of time from admission to the operating room for patients requiring nonelective repair of ventral hernias. Methods Using the 2005-2012 Nationwide Inpatient Sample, we identified adult patients with a primary diagnosis of ventral hernia without obstruction/gangrene, who underwent nonelective repair. The outcome variable of interest was time from admission to surgery. We performed univariate and multivariable analyses using negative binomial regression, adjusting for age, sex, race, income, insurance, admission day, comorbidity status (van Walraven score), diagnosis, procedure, hospital size, location/teaching status, and region. Results 7,253 patients met criteria, of which majority were women (n = 4,615) and white (n = 5,394). The majority of patients had private insurance (n = 3,015) followed by Medicare (n = 2,737). Median time to operation was 0 days. Univariate analysis comparing operation <1 day to ≥1 day identified significant differences in race, day of admission, insurance, length of stay, comorbidity status, hospital location, type, and size. Negative binomial regression showed that weekday admission (IRR 4.42, P < .0001), private insurance (IRR 1.53-2.66, P < .0001), rural location (IRR 1.39-1.76, P < .01), small hospital size (IRR 1.26-1.36, P < .05), white race (IRR 1.30-1.34, P < .01), healthier patients (van Walraven score IRR 1.05, P < .0001), and use of mesh (IRR 0.39-0.56, P < .02) were associated with shorter time until procedure. Conclusion Shorter time from admission to the operating room was associated with several nonclinical factors, which suggest disparities may exist. Further prospective studies are warranted to elucidate these disparities affecting patient care.

Dispersal ofAcaciaseeds by ungulates and ostriches in an African savanna

1996 ◽  
Vol 12 (3) ◽  
pp. 345-356 ◽  
Author(s):  
Maxine F. Miller
Keyword(s):  
South Africa ◽  
Seed Dispersal ◽  
Seedling Recruitment ◽  
Seedling Survival ◽  
Tree Crown ◽  
African Savanna ◽  
Large Herbivores ◽  
Mammalian Herbivores ◽  
Open Environments ◽  
Presence And Absence

ABSTRACTThe dispersal of AfricanAcaciaseeds in the presence and absence of large mammalian herbivores and ostriches was assessed in a savanna ecosystem in South Africa. In the absence of large herbivores,A. tortilisandA. niloticapods were mainly dispersed in the shade, directly beneath the tree crown and seeds remained in pods for over 18 months. In the presence of large herbivores,A. tortilis, A. niloticaandA. karrooseeds were freed from pods and were dispersed into open, non-shaded habitats. Impala dispersed mostA. tortilisseeds (18,900 ha−1), giraffe mostA. niloticaseeds (1060 ha−1) and giraffe and kudu mostA. karrooseeds (452 and 448 ha−1, respectively). Seedling survival in dung in open environments may exceed that of seedlings in soil shaded beneath the tree crown. It appears that seed dispersal by large herbivores may be advantageous to future seedling recruitment.

scholarly journals Factors Affecting Under-Five Mortality in Ethiopia: A Multilevel Negative Binomial Model

2020 ◽  
Vol Volume 11 ◽  
pp. 525-534
Author(s):  
Bisrat Misganew Geremew ◽  
Kassahun Alemu Gelaye ◽  
Alemakef Wagnew Melesse ◽  
Temesgen Yihunie Akalu ◽  
Adhanom Gebreegziabher Baraki
Keyword(s):  
Negative Binomial ◽  
Negative Binomial Model ◽  
Binomial Model ◽  
Factors Affecting ◽  
Under Five ◽  
Multilevel Negative Binomial Model

Vegetation responses to conifer encroachment in a western Cascade meadow: a chronosequence approach

2007 ◽  
Vol 85 (3) ◽  
pp. 285-298 ◽  
Author(s):  
Ryan D. Haugo ◽  
Charles B. Halpern
Keyword(s):  
Forest Structure ◽  
Vegetation Change ◽  
Light Availability ◽  
Basal Area ◽  
Tree Age ◽  
Long Term Effects ◽  
Conifer Encroachment ◽  
Forest Herbs ◽  
Meadow Species ◽  
Chronosequence Approach

Conifer invasion of mountain meadows is pervasive in western North America, but its consequences for plant composition and diversity have not been studied. We used a chronosequence approach to reconstruct temporal patterns of vegetation change in response to ~200 years of conifer encroachment of a dry, montane meadow in the western Cascade Range, Oregon. Tree age distributions, forest structure, light, and vegetation composition were determined for three hundred and fifty-six 10 m × 10 m samples representing a gradient from open meadow to old forest (>90 years). Nonmetric multidimensional scaling revealed strong turnover in species composition from open meadow to old forest. Ordination axes were highly correlated with light availability and density/basal area of encroaching grand fir, Abies grandis (Dougl. ex D. Don) Lindl., and lodgepole pine, Pinus contorta Dougl. ex Loud. Cover of meadow species declined steeply with establishment of A. grandis ; richness declined more gradually and extirpations of meadow species were rare. Forest herbs colonized within two decades of tree establishment and within 60–80 years dominated the understory flora. In contrast with meadow species, changes in richness and cover of forest herbs were weakly related to changes in forest structure. Rapid replacement of meadow by forest species and long-term effects of trees on soils may limit potential for restoration of these unique habitats.

scholarly journals Factors Affecting Crash Frequencies: A Negative Binomial Regression Based Analysis of Indus Highway, Pakistan

2019 ◽  
Vol 296 ◽  
pp. 01005
Author(s):  
Rafi Ullah Khan ◽  
Jingbo Yin ◽  
Faluk Shair Mustafa
Keyword(s):  
Negative Binomial ◽  
Negative Binomial Regression ◽  
Crash Frequency ◽  
Risk Recognition ◽  
Factors Affecting ◽  
Trade Routes ◽  
Vital Importance ◽  
Behavior Understanding ◽  
Binomial Regression ◽  
Spss Software

The increase in vehicular traffic have also increased the highway crash frequency with the passage of time. Improvements in highway safety is of vital importance as it could save vast life and monetary losses. The highway crash frequency analysis of major Pakistani highways is a subject less discovered and many important strategic and trade routes are not studied in this regard. This study is aimed to analyze the crash frequency and the prominent factors that cause these crashes on a 302 km section of Indus highway; one of the most important trade routes of the country. Eight years’ data from 2011 till 2018 was arranged into 19 variables where the crash frequency is set as dependent variable, while the eighteen prominent causation factors as independent variables. The tool used for analysis was negative binomial regression being run in the SPSS software. The results indicate that the driver’s behavior, understanding & risk recognition, negligence and law adherence have a significant effect on the crash frequency. Furthermore, highway crash frequency significantly increases with increase in highway segment lengths, number of lanes and lane widths. Similarly, the highway crash frequency significantly enhances when the light, pavement surface and climate condition gets deteriorated. The results of this study are of vital importance to government, transportation companies and general public in order to recognize the most important accident causing factors and devise the transport policies, rules and behaviors accordingly.

scholarly journals Edge effects alter the role of fungi and insects in mediating functional composition and diversity of seedling recruits in a fragmented tropical forest

2020 ◽  
Vol 126 (7) ◽  
pp. 1181-1191
Author(s):  
Meghna Krishnadas ◽  
Kavya Agarwal ◽  
Liza S Comita
Keyword(s):  
Tropical Forest ◽  
Functional Diversity ◽  
Seed Size ◽  
Wood Density ◽  
Edge Effects ◽  
Seedling Recruitment ◽  
Light Availability ◽  
Canopy Openness ◽  
Dry Matter Content ◽  
Forest Fragments

Abstract Background and Aims In fragmented forests, proximity to forest edges can favour the establishment of resource-acquisitive species over more resource-conservative species. During seedling recruitment, resource-acquisitive species may benefit from either higher light availability or weaker top-down effects of natural enemies. The relative importance of light and enemies for recruitment has seldom been examined with respect to edge effects. Methods In a human-modified wet tropical forest in India, we first examined how functional traits indicative of resource-acquisitive vs. resource-conservative strategies, i.e. specific leaf area (SLA), leaf dry matter content, wood density and seed size, explained interspecific differences in densities of seedling recruits with distance to the forest edge. Then, we checked whether fungicide and insecticide treatments and canopy openness (proxy for light availability) explained edge effects on trait-mediated changes in seedling density. Finally, we examined whether light availability and natural enemy activity explained edge effects on functional diversity of seedling recruits. Key Results Up to 60 m from edges, recruit densities increased with decreasing seed size, but not at 90–100 m, where recruit densities increased with higher SLA. Trait-mediated variation in recruit densities changed with pesticides only at 90–100 m: compared with control plots, fungicide increased recruit densities for low SLA species and insecticide increased smaller seeded species. For SLA, wood density and seed size, functional diversity of recruits was higher at 90–100 m than at 0–5 m. At 90–100 m, fungicide decreased functional diversity for SLA and insecticide reduced seed size diversity compared with control plots. Canopy openness explained neither variation in recruit density in relation to traits nor functional diversity. Conclusions Altered biotic interactions can mediate local changes to trait composition and functional diversity during seedling recruitment in forest fragments, hinting at downstream effects on the structure and function of human-modified forests.

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