scholarly journals Tropical ash (Fraxinus udhei) invading Andean forest remnants in Northern South America

2017 ◽  
Author(s):  
Kelly A Saavedra-Ramírez ◽  
Andrés Etter ◽  
Alberto Ramírez
Keyword(s):  
Vegetation Cover ◽  
Biological Diversity ◽  
Survival Rates ◽  
Canopy Cover ◽  
Physical Factors ◽  
Natural Environments ◽  
Demographic Structure ◽  
Tropical Mountains ◽  
Exotic Invasive Species ◽  
Forest Remnants

Exotic invasive species represent a major driver of the loss of biological diversity and services provided by ecosystems globally. An important source of species becoming invasive are the commercial afforestation projects using fast growing and adaptable exotic species, which may become invasive impacting natural environments. The Tropical Ash (Fraxinus uhdei) native to México has been widely introduced for many decades to Colombia and other countries for timber, live fences and urban greening, is now common in many areas of the tropical mountains, and has been observed expanding into native forests in Colombia. This study explores the invasion of Tropical Ash in remnant Andean forests in Colombia, to understand the invasion pattern and the demographic structure of Tropical Ash. The analysis took into account biotic and physical factors, such as distance to the propagule source, vegetation cover types, and density of the understory and canopy cover. Although the reproductive strategy of the Tropical Ash is of “r” type with low survival rates, the results show evidence for an active process of invasion characterized by an aggregated distribution pattern. The study shows the existence of an interaction between the distance to the propagule source and the vegetation cover, which has an additive effect on the demographic structure of the population.

scholarly journals Tropical ash (Fraxinus udhei) invading Andean forest remnants in Northern South America

2017 ◽  
Author(s):  
Kelly A Saavedra-Ramírez ◽  
Andrés Etter ◽  
Alberto Ramírez
Keyword(s):  
Vegetation Cover ◽  
Biological Diversity ◽  
Survival Rates ◽  
Canopy Cover ◽  
Physical Factors ◽  
Natural Environments ◽  
Demographic Structure ◽  
Tropical Mountains ◽  
Exotic Invasive Species ◽  
Forest Remnants

Exotic invasive species represent a major driver of the loss of biological diversity and services provided by ecosystems globally. An important source of species becoming invasive are the commercial afforestation projects using fast growing and adaptable exotic species, which may become invasive impacting natural environments. The Tropical Ash (Fraxinus uhdei) native to México has been widely introduced for many decades to Colombia and other countries for timber, live fences and urban greening, is now common in many areas of the tropical mountains, and has been observed expanding into native forests in Colombia. This study explores the invasion of Tropical Ash in remnant Andean forests in Colombia, to understand the invasion pattern and the demographic structure of Tropical Ash. The analysis took into account biotic and physical factors, such as distance to the propagule source, vegetation cover types, and density of the understory and canopy cover. Although the reproductive strategy of the Tropical Ash is of “r” type with low survival rates, the results show evidence for an active process of invasion characterized by an aggregated distribution pattern. The study shows the existence of an interaction between the distance to the propagule source and the vegetation cover, which has an additive effect on the demographic structure of the population.

Community characteristics of forest understory birds along an elevational gradient in the Horn of Africa: A multi-year baseline

The Condor ◽  
2021 ◽  
Author(s):  
Kyle D Kittelberger ◽  
Montague H C Neate-Clegg ◽  
Evan R Buechley ◽  
Çağan Hakkı Şekercioğlu
Keyword(s):  
Species Richness ◽  
Species Turnover ◽  
Survival Rates ◽  
Elevational Gradient ◽  
Forest Understory ◽  
Bird Abundance ◽  
Tropical Mountains ◽  
Demographic Rates ◽  
Understory Birds ◽  
Over Time

Abstract Tropical mountains are global hotspots for birdlife. However, there is a dearth of baseline avifaunal data along elevational gradients, particularly in Africa, limiting our ability to observe and assess changes over time in tropical montane avian communities. In this study, we undertook a multi-year assessment of understory birds along a 1,750 m elevational gradient (1,430–3,186 m) in an Afrotropical moist evergreen montane forest within Ethiopia’s Bale Mountains. Analyzing 6 years of systematic bird-banding data from 5 sites, we describe the patterns of species richness, abundance, community composition, and demographic rates over space and time. We found bimodal patterns in observed and estimated species richness across the elevational gradient (peaking at 1,430 and 2,388 m), although no sites reached asymptotic species richness throughout the study. Species turnover was high across the gradient, though forested sites at mid-elevations resembled each other in species composition. We found significant variation across sites in bird abundance in some of the dietary and habitat guilds. However, we did not find any significant trends in species richness or guild abundances over time. For the majority of analyzed species, capture rates did not change over time and there were no changes in species’ mean elevations. Population growth rates, recruitment rates, and apparent survival rates averaged 1.02, 0.52, and 0.51 respectively, and there were no elevational patterns in demographic rates. This study establishes a multi-year baseline for Afrotropical birds along an elevational gradient in an under-studied international biodiversity hotspot. These data will be critical in assessing the long-term responses of tropical montane birdlife to climate change and habitat degradation.

scholarly journals Habitat associations and conservation status of an endemic forest dwarf chameleon (Bradypodion sp.) from South Africa

Oryx ◽  
2006 ◽  
Vol 40 (2) ◽  
pp. 183-188 ◽  
Author(s):  
Walter J. Reisinger ◽  
Devi M. Stuart-Fox ◽  
Barend F.N. Erasmus
Keyword(s):  
South Africa ◽  
Conservation Status ◽  
Canopy Cover ◽  
Iucn Red List ◽  
Habitat Associations ◽  
Suitable Habitat ◽  
Area Of Occupancy ◽  
Forest Interior ◽  
Forest Remnants ◽  
Iucn Red List Criteria

We quantified habitat associations and evaluated the conservation status of a recently identified, undescribed species of dwarf chameleon, Bradypodion sp. nov. Dhlinza, endemic to scarp forest remnants in KwaZulu-Natal Province, South Africa. At the microhabitat scale the Dhlinza dwarf chameleon was found more often in forest gaps and near paths than highly disturbed edges or forest interior. Chameleon presence was not explained by forest physiognomic variables such as vine cover, shrub and tree density, or canopy cover. Presence near gaps may be better explained by the combined effects of the thermal microenvironment and food availability. The species is moderately common where it occurs, with estimated densities of 4.7, 8.7 and 29.7 individuals per ha within forest interior, edges and gaps respectively. At the landscape scale, the chameleon occurs only in three remnant forests: the Dhlinza, Entumeni and Ongoye Forests. The species' extent of occurrence was estimated to be 88 km2 and its area of occupancy 49 km2. Based on the small area of remaining suitable habitat, this species meets the requirements for categorization as Endangered according to IUCN Red List criteria.

scholarly journals Vital signs: An ecosemiotic perspective on the human ecology of Amazonia

2001 ◽  
Vol 29 (1) ◽  
pp. 121-152
Author(s):  
Alf Hornborg
Keyword(s):  
Human Ecology ◽  
Biological Diversity ◽  
Vital Signs ◽  
Human Populations ◽  
Natural Environments ◽  
Semiotic Analysis ◽  
Face To Face ◽  
Sign Systems ◽  
Environmental Relations

Ecosemiotics represents a theoretical approach to human ecology that can be applied across several disciplines. lts primary justification lies inthe ambition to transcend "Cartesian", conceptual dichotomies such as culture/nature. society/nature, mental/material. etc. It argues that ecosystems areconstituted no less by flows of signs than by flows of matter and energy. This paper discusses the roles of different kinds of hmnan sign systems in the ecologyof Amazonia, ranging from the phenomenology of unconscious sensations. through linguistic signs such as metaphors and ethnobiological taxonomies, to money and the political economy of environmental destruction. Human-environmental relations mediated by direct, sensory and (oral) linguistic communication have tended to enhance biological diversity, suggesting modes of calibrating the long-term co-evolution of human and non-human populations. Economic sign systems, on the other hand, have rapidly and drastically transfonned human-environmental relations in Amazonia to the point where the entire rainforest ecosystem is illlder threat. In detaching themselves from the direct, "face-to-face" communication between humans and their natural environments, flows of money and commodities - and the decontextualized knowledge systems that they engender - have no means of staying geared to the long-term negotiation of local, ecological co-existence. It is argued that the ongoing deterioration of the biosphere can be viewed as a problem of communication, deserving semiotic analysis.

A global perspective on tropical montane rivers

Science ◽  
2019 ◽  
Vol 365 (6458) ◽  
pp. 1124-1129 ◽  
Author(s):  
Andrea C. Encalada ◽  
Alexander S. Flecker ◽  
N. LeRoy Poff ◽  
Esteban Suárez ◽  
Guido A. Herrera-R ◽  
...  
Keyword(s):  
Biological Diversity ◽  
Ecosystem Processes ◽  
High Elevation ◽  
Global Perspective ◽  
Model Systems ◽  
Flow Disturbance ◽  
Tropical Mountains ◽  
Rapid Changes ◽  
Rapid Temperature ◽  
Biodiversity And Ecosystem Function

Tropical montane rivers (TMR) are born in tropical mountains, descend through montane forests, and feed major rivers, floodplains, and oceans. They are characterized by rapid temperature clines and varied flow disturbance regimes, both of which promote habitat heterogeneity, high biological diversity and endemism, and distinct organisms’ life-history adaptations. Production, transport, and processing of sediments, nutrients, and carbon are key ecosystem processes connecting high-elevation streams with lowland floodplains, in turn influencing soil fertility and biotic productivity downstream. TMR provide key ecosystem services to hundreds of millions of people in tropical nations. In light of existing human-induced disturbances, including climate change, TMR can be used as natural model systems to examine the effects of rapid changes in abiotic drivers and their influence on biodiversity and ecosystem function.

Gamete quality in fish: evaluation parameters and determining factors

Zygote ◽  
2013 ◽  
Vol 23 (2) ◽  
pp. 177-197 ◽  
Author(s):  
Iván I. Valdebenito ◽  
Patricia C. Gallegos ◽  
Brian R. Effer
Keyword(s):  
Water Quality ◽  
Survival Rates ◽  
Physical Factors ◽  
Male And Female ◽  
Feeding Management ◽  
Determining Factors ◽  
Water Conditions ◽  
Evaluation Parameters

SummaryThe quality of fish gametes, both male and female, are determined by several factors (age, management, feeding, chemical and physical factors, water quality, etc.) that have an impact on the survivability of embryos, larvae and/or fry in the short or long term. One of the most important factors is gamete ageing, especially for those species that are unable to spawn naturally in hatcheries. The chemical and physical factors in hatcheries and the nutrition that they provide can significantly alter harvest quality, especially from females; as a rule, males are more tolerant of stress conditions produced by inadequate feeding, management and/or poor water conditions. The stress produced on broodstock by inadequate conditions in hatcheries can produce adverse effects on gamete quality, survival rates, and the embryonic eggs after hatching.

Population dynamics of hispid cotton rats (Sigmodon hispidus) across a nitrogen-amended landscape

2003 ◽  
Vol 81 (6) ◽  
pp. 994-1003 ◽  
Author(s):  
Jay E Clark ◽  
Eric C Hellgren ◽  
Eric E Jorgensen ◽  
Susan J Tunnell ◽  
David M Engle ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Reproductive Success ◽  
Survival Rates ◽  
Canopy Cover ◽  
Sigmodon Hispidus ◽  
Old Field ◽  
Higher Plant ◽  
Population Growth Rates ◽  
Low Level ◽  
Cotton Rats

We conducted a mark–recapture experiment to examine the population dynamics of hispid cotton rats (Sigmodon hispidus) in response to low-level nitrogen amendments (16.4 kg nitrogen/ha per year) and exclosure fencing in an old-field grassland. The experimental design consisted of sixteen 0.16-ha plots with 4 replicates of each treatment combination. We predicted that densities, reproductive success, movement probabilities, and survival rates of cotton rats would be greater on nitrogen-amended plots because of greater aboveground biomass and canopy cover. Population densities of cotton rats tended to be highest on fenced nitrogen plots, but densities on unfenced nitrogen plots were similar to those on control and fenced plots. We observed no distinct patterns in survival rates, reproductive success, or movement probabilities with regard to nitrogen treatments. However, survival rates and reproductive success tended to be higher for cotton rats on fenced plots than for those on unfenced plots and this was likely attributable to decreased predation on fenced plots. As low-level nitrogen amendments continue to be applied, we predict that survival, reproduction, and population-growth rates of cotton rats on control plots, especially fenced plots with no nitrogen amendment, will eventually exceed those on nitrogen-amended plots as a result of higher plant-species diversity, greater food availability, and better quality cover.

scholarly journals Fecundity of Winged Euonymus Cultivars and Their Ability to Invade Various Natural Environments

HortScience ◽  
2012 ◽  
Vol 47 (8) ◽  
pp. 1029-1033 ◽  
Author(s):  
Mark H. Brand ◽  
Jessica D. Lubell ◽  
Jonathan M. Lehrer
Keyword(s):  
Seed Production ◽  
Seedling Survival ◽  
Germination Rate ◽  
Survival Rates ◽  
Natural Environments ◽  
Euonymus Alatus ◽  
Demographic Models ◽  
Non Invasive ◽  
Deciduous Woodland ◽  
Northern United States

Winged euonymus [Euonymus alatus (Thunb.)] is an important landscape shrub that has demonstrated its potential to be invasive in numerous states across the central and northern United States. Nine cultivars were evaluated for their potential to produce fruits and seeds in a randomized, replicated field planting. Seeds from all cultivars were evaluated for germination rate and initial survival in a deciduous woodland. Seeds collected from ‘Compactus’ were also sown in five natural environments (full sun meadow, edge of woods, moist woods, dry woods, pine woods) to determine which habitat types support its germination and establishment. Seed production for cultivars varied from 981 to 6090 seeds per plant. The dry deciduous woods and pine woods were the only environments that supported significant germination rates that could be as high as 37.8%. Seedling survival was at least 77% in the deciduous dry woods and at least 55% in the pine woods. In the first replication, establishment rates for cultivars in the dry deciduous woods ranged from a low of 6.5% for ‘Odom’ Little Moses™ to a high of 42.5% for ‘Monstrosus’. In the second replication, all cultivars achieved over 30% establishment and most exceeded 40% establishment. An estimate of the annual seedling contribution per plant per cultivar was calculated by combining seed production data with establishment data for each cultivar. This estimate was predicted to range from 588 to 3763 and therefore none of the nine cultivars evaluated should be considered non-invasive based on our findings. Our findings show that germination and seedling survival rates are high for E. alatus and because the species is long-lived, cultivars will likely have to be completely seed-sterile to be considered non-invasive according to demographic models.

scholarly journals Online appendix 1:Exploring an extensive dataset to establish woody vegetation cover and composition in Kruger National Park for the late 1980s

Koedoe ◽  
2014 ◽  
Vol 56 (1) ◽  
Author(s):  
Gregory A. Kiker ◽  
Rheinhardt Scholtz ◽  
Izak P.J. Smit ◽  
Freek J. Venter
Keyword(s):  
Species Richness ◽  
Vegetation Cover ◽  
National Park ◽  
Large Scale ◽  
Plant Cover ◽  
Canopy Cover ◽  
Woody Species ◽  
Kruger National Park ◽  
Tree Cover ◽  
Woody Vegetation

Woody plant cover and species composition play an important role in defining the type and function of savanna ecosystems. Approximately 2000 sites in the Kruger National Park (KNP) were surveyed by F.J. Venter over a period from 1985 to 1989, recording vegetation, soil and topological characteristics. At each of these sites (approximately 20 m × 20 m each), woody vegetation cover and species were recorded using a rapid, Braun-Blanquet classification for three height classes: shrub (0.75 m – 2.50 m), brush (2.50 m – 5.50 m) and tree (> 5.50 m). The objective of this study was to re-analyse the vegetation component of the field data, with a specific focus to provide a spatially explicit, height-differentiated, benchmark dataset in terms of species occurrence, species richness and structural canopy cover. Overall, 145 different woody species were recorded in the dataset out of the 458 species documented to occur in the park. The dataset describes a woody layer dominated by a relatively small number of widely occurring species, as 24 of the most common woody species accounted for all woody species found on over 80% of all sites. The less common woody species (101) were each recorded on 20 sites or less. Species richness varied from 12 to 1 species per site. Structural canopy cover averaged 9.34%, 8.16% and 2.89% for shrub, brush and tree cover, respectively. The dataset provides a useful benchmark for woody species distribution in KNP and can be used to explore woody species and height class distributions, as well as comparison with more recent or future woody vegetation surveys.Conservation implications: The results provided evidence that large-scale, woody vegetation surveys conducted along roads offer useful ecosystem level information. However, such an approach fails to pick up less common species. The data presented here provided a useful snapshot of KNP woody vegetation structure and composition and could provide excellent opportunities for spatio-temporal comparisons.

Neonatal survival: an overview

1992 ◽  
Vol 15 ◽  
pp. 1-7 ◽  
Author(s):  
M. A. Varley
Keyword(s):  
Medical Profession ◽  
Survival Rates ◽  
Farm Animals ◽  
Physical Factors ◽  
High Survival ◽  
Animal Agriculture ◽  
Factors Affecting ◽  
Neonatal Deaths ◽  
Probability Of Survival ◽  
Use Of Resources

AbstractMortality in neonates has always represented significant economic wastage and slow progress has been made in the understanding of the factors influencing the probability of survival or death. There is also increasing pressure in the animal agriculture sphere to pursue improved welfare and in the situation where neonatal deaths are a high proportion of the liveborn offspring, then this becomes not only an economic concern but also a welfare issue. This paper highlights principal problems within the neonatal area in order to introduce the ensuing text dealing with specific technical challenges.The magnitude of loss for different species including humans is given and the factors affecting mortalities are discussed. The major components include: human factors, pathogenic agents, immunological factors, temperature and thermoregulation, nutrition, behaviour and physical factors.Although single factors are often ascribed as the cause of death, the reality is that there are usually multifactorial components involved which interact and contribute to the final mortality of the individual.The approach to the practical management of neonates varies widely between the different animal industries and the techniques deployed depend on relative economic values. In human health care every available resource is used to ensure very high survival rates because of the incalculable value of each individual delivered. With farm animals the use of resources is at a much lower level and survival rates are lower. It ought to be possible in animal agriculture to adopt some of the methods used in the medical profession to assess high risk situations and to divert resources appropriately.

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