scholarly journals Assessing the Population Status of a Tree Species Using Distance Sampling:Aquilaria crassna(Thymelaeaceae) in Northern Laos

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Anders Jensen ◽  
Henrik Meilby
Keyword(s):  
Tree Species ◽  
Conservation Status ◽  
Distance Sampling ◽  
Average Density ◽  
Survey Method ◽  
Line Transect ◽  
Population Status ◽  
Wide Range ◽  
Nontimber Forest Product ◽  
Present Case Study

Lack of reliable and accurate field data affect assessments of population status of tree species, especially tropical taxa with broad distributions. Use of distance sampling techniques may help to overcome the problem. This paper describes a method for estimation of absolute density of a rare tree species with scattered and clumped distribution, using line transect distance sampling. The method was applied to previously harvested populations ofAquilaria crassnaPierre ex H. Lec. (Thymelaeaceae) at four sites in Northern Laos. This species is destructively harvested to yield agarwood, probably the world’s most valuable nontimber forest product and categorised as ”critically endangered“. The average density of felledA. crassnatrees at the four sites was 2.2 ha−1, indicating that harvesting has been extensive. However, the estimated densities of living saplings, 10.9 ha−1, small trees (DBH < 10 cm), 10.6 ha−1, and larger trees (DBH ≥ 10 cm), 1.7 ha−1, suggest that populations are not wiped flat. The survey method should stand a good chance of wider use as a tool in management and conservation of a wide range of tree species. Results of the present case study could suggest that the conservation status ofA. crassnashould be re-categorised.

State of Conservation and Population Structure of Bird Species Inhabiting in Various Subtropical Urban Forests

2021 ◽  
Author(s):  
M. N. Rajpar ◽  
M. Zakaria
Keyword(s):  
Population Structure ◽  
Conservation Status ◽  
Distance Sampling ◽  
Bird Species ◽  
Urban Forests ◽  
Avian Species ◽  
Bird Diversity ◽  
Line Transect ◽  
Distance Analysis ◽  
Wide Range

Abstract To determine the conservation status and population structure of avian species living in various subtropical broadleaved urban forests, namely Dob Ghar, Kamal Khan, Kityari, Palamar, Seya Sar and Shahabad of Pakistan, we aimed to use the distance sampling line transect process. To avoid double counting of the same bird individual, a total of 180 counting points were set at 250 m from each other. In all, between December 2017 and November 2018, 2,879 individuals representing 53 species, 28 families and 9 orders were detected. One species was vulnerable (VU) out of 53 bird species, while the remaining 52 species were the least concerned (LC). In particular, the results of the distance analysis indicate that, in six subtropical broad-leaved forests, the bird population can vary. For eg, Palamar (0.954 ± 0.221 birds/ha) and Kityari (0.938 ± 0.162 birds/ha) were densely populated by bird species, while Kamal Khan (0.102 ± 0.178 birds/ha) was less concerm. Similarly, the CAP findings showed that bird species in Dob Ghar were more diverse (H’ = 33.92 ± 1.368) and equally distributed (E = 0.9657 ± 0.004) and that the Shahabad ecosystem was rich in bird species (R1 = 8.007 ± 0.053) compared to other habitats. In addition, the length of the twigs and topological changes in the dendrogram have shown that bird diversity may vary from habitat to habitat. The bird species were classified into eight foraging guilds. Insectivores were the most abundant bird species using all habitats in abundance. By cons, Carnivore/Piscivore/Insectivore averted to use the forest habitats Dob Ghar and Frugivore Kamal Khan and Dob Ghar. The findings of this study revealed that broad-leaved subtropical urban forests are home to a wide range of avian species. However, habitat selection among bird species varied across habitats according to vegetation structure and composition, food resources, adjoining habitats, and human settlements.

scholarly journals Subtropical Broad-Leaved Urban Forests as the Foremost Dynamic and Complex Habitats for a Wide Range of Bird Species

2021 ◽  
Vol 13 (23) ◽  
pp. 13021
Author(s):  
Muhammad Nawaz Rajpar ◽  
Shahab Ali Khan ◽  
Allah Ditta ◽  
Hayssam M. Ali ◽  
Sami Ullah ◽  
...  
Keyword(s):  
Anthropogenic Activities ◽  
Conservation Status ◽  
Distance Sampling ◽  
Bird Species ◽  
Urban Forests ◽  
Line Transect ◽  
Current Conservation ◽  
Diverse Range ◽  
Bird Density ◽  
Wide Range

Broad-leaved subtropical forests are the most productive, diversified, and complex ecosystems on the planet. Unfortunately, they are currently under severe threat from anthropogenic activities, such as. deforestation, housing settlements, and agricultural expansion. In response to these severe effects, the present study was conducted to explore the current conservation status and population structure of a wide range of bird species inhabiting different subtropical broad-leaved urban forests of Pakistan. In total, 2879 individuals comprising 53 species and 28 families were detected between December 2017 and November 2018 as revealed through the distance sampling line transect method. The habitat selection among bird species varied according to vegetation structure and composition, food resources, adjoining habitats, and human settlements. According to IUCN Red List data, one species was deemed vulnerable out of 53 bird species, while the remaining 52 species were ranked as ofleast concern. The findings of the density analysis revealed that bird density varied between six subtropical broad-leaved forests. Palamar (3.954 ± 0.221 birds/ha) and Kityari (3.138 ± 0.162 birds/ha) were densely populated, whereas Kamal Khan (1.102 ± 0.178 birds/ha) was of the least concern. Likewise, the diversity analysis showed that Kamal Khan was a more diverse habitat (Shannon–Wiener Index; H’ = 3.581 ± 0.021). Shahabad was richer (Margalef Richness Index; R1 = 8.007 ± 0.053) and Dob Ghar was evenly distributed (Pielou J Evenness Index; E = 0.940 ± 0.005) compared to other urban habitats studied. Eight foraging guilds were identified among the bird species. Insectivores were the most abundant bird species utilizing the urban dwelling habitats. carnivores/piscivores/insectivores utilized Dob Ghar forest, while more frugivores utilized Kamal Khan and Dob Ghar. Based on the data, it was concluded that subtropical broad-leaved urban forests are dynamic, complex, and of vital significance for a diverse range of bird species.

scholarly journals Tendencias poblacionales recientes de la avutarda hubara en las Islas Canarias: análisis metodológico y estado de conservación

2012 ◽  
Vol 35 (1) ◽  
pp. 125-139
Author(s):  
C. Schuster ◽  
◽  
J. J. Iglesias-Lebrija ◽  
L. M. Carrascal ◽  
◽  
...  
Keyword(s):  
Canary Islands ◽  
Conservation Status ◽  
Distance Sampling ◽  
Small Variation ◽  
Population Trends ◽  
Line Transect ◽  
Sampling Area ◽  
Average Value ◽  
Houbara Bustard ◽  
Population Sizes

Recent population trends of the houbara bustard in the Canary Islands. Methods and conservation status Determining conservation status requires rigorous and reliable data about population sizes and trends, especially if they have to be applied to islands where the species have small populations. The Canary bustard houbara (Chlamydotis undulata fuertaventurae) is catalogued as ‘in danger’ by the Red Book of the Birds of Spain. This work analyzes the value of previously published information on the species using the method of adjacent linear transects separated by 200 m, as a baseline for establishing robust population trends in 30 important areas (ranging from 1.3 to 12.8 km2) for the houbara in the islands of Lanzarote and Fuerteventura (Canary Islands). Censuses were repeated on the same dates (from November to December) and localities as those carried out in 1994, 2004 and 2006. The detection probability of the houbara was estimated by means of distance sampling, being 0.42 up to 250 m from the observer, and 0.82 in the main census belt of 100 m on either side of the line transect. The method of adjacent linear transects —counting the maximum number of hubaras detected— provides accurate figures of population densities (detection of 95.2% of the birds). The previous estimations of houbara densities can therefore be considered highly trustworthy, with a probable average underestimation of only 5 %. Nevertheless, the confidence intervals of density estimations using only one census were very large. Therefore, with only one census per sampling area and year it is not possible to obtain precise estimates of houbara densities with small variation around the average value. This raises concern when trying to obtain solid evidence about the increases–decreases of houbara populations comparing different dates or study areas. The density of the Canary Island hubara bustard decreased significantly from 2004/2006 to 2011 in eight areas of Fuerteventura (Vega Vieja, Los Alares–Pocetas, Matas Blancas, Lorenzo– Diviso, Corralejo, Lajares and Fimapaire) and in two areas of Lanzarote (Argana and La Santa). Conversely, the density of the houbara significantly increased in three areas of Lanzarote (Zonzamas, Guatiza and Llano de las Maretas). As a whole, average population density did not differ significantly between 2004/2006 and 2011 in Fuerteventura (slight decrease of 29% in 2011), but there was a significant increase in Lanzarote (increase of 60% from 2004/2006 to 2011). The change in density from 2004/2006 to 2011 tended to be an increase in areas further from paved roads, and a decrease in locations predominantly covered by loose sandy soils.

Estimating the population size of a threatened arboreal marsupial: use of distance sampling to dispense with ad hoc survey techniques

2010 ◽  
Vol 37 (6) ◽  
pp. 512 ◽  
Author(s):  
Paul J. de Tores ◽  
Sue Elscot
Keyword(s):  
Land Use ◽  
Population Size ◽  
Ad Hoc ◽  
Conservation Status ◽  
Distance Sampling ◽  
Potential Effect ◽  
Decision Makers ◽  
Biological Information ◽  
Line Transect ◽  
Land Use Decisions

Context. Long-term land-use decisions potentially affecting the conservation status of rare fauna are often based on a dearth of relevant biological information and population estimates are regularly derived from ad hoc methodologies. This can significantly affect the outcomes from development assessment and approval processes. Aim. Our aims were to apply distance-sampling techniques to derive robust, quantitative estimates of the population size of a threatened arboreal marsupial, the western ringtail possum (Pseudocheirus occidentalis Thomas, 1888), demonstrate the advantages of this approach and, in doing so, provide conservation managers, decision makers and consultants with a reliable framework for surveying the species. Methods. We used line-transect sampling to derive estimates of density and abundance for P. occidentalis at two sites in south-western Western Australia where estimates were previously derived through ad hoc techniques. Key results. Our findings support the assertion that previous surveys of P. occidentalis populations have underestimated the population size to a varying extent at both of our survey sites. Land-use and development-application decisions have previously been based on similar surveys. Conclusions. Distance sampling, if applied routinely when surveying P. occidentalis, will reduce the uncertainty associated with derived estimates of abundance. Implications. Appropriate use of distance-sampling methods will enable managers and decision makers to assess more quantitatively the potential effect from, and place appropriate approval conditions on, proposals that modify or destroy P. occidentalis habitat. The use of the program Distance will enable such decisions to be based on robust, repeatable estimates of population size, with quantified confidence limits and variance estimates.

scholarly journals Status assessment of the Critically Endangered Azores Bullfinch Pyrrhula murina

2011 ◽  
Vol 21 (4) ◽  
pp. 477-489 ◽  
Author(s):  
RICARDO S. CEIA ◽  
JAIME A. RAMOS ◽  
RUBEN H. HELENO ◽  
GEOFF M. HILTON ◽  
TIAGO A. MARQUES
Keyword(s):  
Population Size ◽  
Conservation Status ◽  
Distance Sampling ◽  
Iucn Red List ◽  
Range Size ◽  
Critically Endangered ◽  
Survey Method ◽  
Mountain Range ◽  
Laurel Forest ◽  
Area Of Occupancy

SummaryThe Azores Bullfinch is endemic to the island of São Miguel (Azores, Portugal). Its status was uplisted to Critically Endangered in 2005 on the basis of an extremely small and declining population that was considered to be restricted to a very small mountain range (43 km2), in a single location, within which the spread of invasive plants constituted a threat to habitat quality. Nevertheless, information was mostly inferred, or the product of, non-systematic studies. In order to carry out a complete assessment of the conservation status we analysed: (i) population trend, calculated from annual monitoring 1991–2008, (ii) population size, and (iii) range size, obtaining estimates in a single morning study in 2008 involving the simultaneous participation of 48 observers. Contrary to previous inferences, the population is no longer decreasing, although quality of laurel forest habitat continues to decline due to the persistent threat of invasive species. Population size (mean ± SE) was estimated at 1,064 ± 304 individuals using distance sampling methods, although the estimate was very sensitive to the survey method used. Range size estimates (extent of occurrence and area of occupancy) were 144 km2 and 83 km2 respectively. Given the present information, we propose the downlisting of Azores Bullfinch to Endangered on the IUCN Red List.

Gorilla Abundance Estimations within North-East Moukalaba-Doudou National Park, Gabon

2021 ◽  
pp. 1-9
Author(s):  
Nana Ismaila ◽  
Ulrich Maloueki
Keyword(s):  
National Park ◽  
Conservation Status ◽  
Mixed Forest ◽  
Habitat Type ◽  
Survey Method ◽  
Encounter Rate ◽  
Line Transect ◽  
Sampling Effort ◽  
North East ◽  
Minimal Convex

Accurate measures of animal population densities are essential to evaluate conservation status and implement action plans to ensure species survival. Gorilla numbers were assessed using the recce survey method within Moukalaba-Doudou National Park (MDNP) in Gabon using fresh nest counts of up to 1 week old. We walked 3,592 km within a 23.01-km<sup>2</sup> study site totalling a sampling effort of 297 days. Encounter rate was 0.12 fresh nests per kilometre, and gorilla density estimates generated by home range sizes (by minimal convex polygon) ranged between 1.14 and 1.48 gorillas/km<sup>2</sup>. Gorillas preferred mixed forest for nesting over other habitats (Cheason index value 1.31). Results showed that gorilla density values within the study area concurred with previous studies that used line transect methodologies. We conclude that the choice of sampling design is dependent on environmental conditions characterised by each habitat type and target species.

scholarly journals Towards Conservation of the Remarkably High Number of Daisy Trees (Asteraceae) in Mexico

Plants ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 534
Author(s):  
Rosario Redonda-Martínez ◽  
Patricio Pliscoff ◽  
Andrés Moreira-Muñoz ◽  
Esteban Manuel Martínez Salas ◽  
Marie-Stéphanie Samain
Keyword(s):  
Tree Species ◽  
Conservation Status ◽  
Vascular Plant ◽  
Species Number ◽  
Global Level ◽  
Climatic Suitability ◽  
Plant Family ◽  
Western Mexico ◽  
Wide Range ◽  
Modelling Approach

Mexico is floristically the fourth most species-rich country in the world, and Asteraceae is the most diverse vascular plant family in this country. The species exhibits a wide range of growth forms, but the tree-like habit, appropriately named daisy trees, is heavily underestimated, even though slightly different tree definitions are handled. Very little is known about their precise species number or conservation status in Mexico, so we update here the list of known Mexican daisy tree species, summarize their very diverse uses, present a general panorama of their present and future distribution, and discuss their conservation status. A bibliographic review and herbarium study were carried out, carefully curated taxonomical ocurrence maps were prepared for each species, and a climatic suitability modelling approach was used to characterise the spatial patterns of Mexican Asteraceae trees. With 149 daisy tree species, the country ranks second at a global level; within the country, their greatest diversity is found in central and western Mexico. A decrease in diversity is estimated in areas that currently host the highest species richness, whereas the hotspot regions are estimated to show an increase in species diversity, so climate change is not a threat to all Mexican daisy tree species.

scholarly journals Population Size and Human-Grivet Monkeys (Chlorocebus aethiops) Conflict in Zegie Peninsula, Bahir Dar, Ethiopia

2020 ◽  
Author(s):  
Yibelu Yitayih ◽  
Dessalegn Ejigu ◽  
Misganaw Mola
Keyword(s):  
Population Size ◽  
Conservation Status ◽  
Population Estimate ◽  
Line Transect ◽  
Chlorocebus Aethiops ◽  
Wide Range ◽  
Significant Difference ◽  
Dry Seasons ◽  
The Impact ◽  
Wet And Dry Seasons

Abstract Background: Grivet monkey (Chlorocebus aethiops) is an Old World monkey with long white tufts of hair along the sides of the face. They inhabit a wide range of habitat types. A study on population size and human-grivet monkey conflict in Zegie Peninsula was carried out from August 2019 to March 2020; the study comprised both the wet and dry seasons. The line transect method was used to collect data on the population size of grivet monkeys. Questionnaire and focus group discussions were used to study the human-grivet monkey conflict and its conservation status. Results: The estimated population of grivets in the study area was 4808. Population structure of grivets indicated that there were 634 adult males, 1236 adult females, 1733 juveniles, and 1205 infants. Grivet population estimate between the wet and dry seasons did not show significant differences (ᵡ2 = 0.938, df = 1, p > 0.05). But there was a significant difference in the population estimate of grivets among the different habitats (ᵡ2 = 238.295, df = 3, p < 0.05).Conclusion: There was a human-grivet monkey conflict in the Peninsula and grivets were damaged crops, not only crops but also predating poultry, steal an egg, and human food. Consequently, grivets were killed in response to the damage they cause to crops. Grivet’s habitat in the Peninsula is highly disturbed because the local people cut trees for sale to support their livelihood. Awareness creation of the residents about wildlife and their habitat is necessary, and people should understand the impact of deforestation, illegal hunting, and the role of grivets in the ecosystem at large. Hence there is a need to protect the forest in order to ensure sustainable conservation of biodiversity in general and grivet monkeys in particular.

scholarly journals Using encounter rates as surrogates for density estimates makes monitoring of heavily-traded grey parrots achievable across Africa

Oryx ◽  
2015 ◽  
Vol 50 (4) ◽  
pp. 617-625 ◽  
Author(s):  
Stuart J. Marsden ◽  
Emmanuel Loqueh ◽  
Jean Michel Takuo ◽  
John A. Hart ◽  
Robert Abani ◽  
...  
Keyword(s):  
Local Density ◽  
Conservation Status ◽  
Distance Sampling ◽  
Central Africa ◽  
High Mobility ◽  
Encounter Rate ◽  
Line Transect ◽  
African Countries ◽  
Density Estimates ◽  
Encounter Rates

AbstractEstimating population sizes in the heavily traded grey parrots of West and Central Africa would provide insights into conservation status and sustainability of harvests. Ideally, density estimates would be derived from a standardized method such as distance sampling, but survey efforts are hampered by the extensive ranges, patchy distribution, variable abundance, cryptic habits and high mobility of the parrots as well as by logistical difficulties and limited resources. We carried out line transect distance sampling alongside a simpler encounter rate method at 10 sites across five West and Central African countries. Density estimates were variable across sites, from 0–0.5 individuals km−2 in Côte d'Ivoire and central Democratic Republic of the Congo to c. 30 km−2 in Cameroon and > 70 km−2 on the island of Príncipe. Most significantly, we identified the relationship between densities estimated from distance sampling and simple encounter rates, which has important applications in monitoring grey parrots: (1) to convert records of parrot groups encountered in a day's activities by anti-poaching patrols within protected areas into indicative density estimates, (2) to confirm low density in areas where parrots are so rare that distance sampling is not feasible, and (3) to provide a link between anecdotal records and local density estimates. Encounter rates of less than one parrot group per day of walking are a reality in most forests within the species’ ranges. Densities in these areas are expected to be one individual km−2 or lower, and local harvest should be disallowed on this basis.

Biscogniauxia (Hypoxylon) Canker or Dieback in Trees

EDIS ◽  
2017 ◽  
Vol 2017 (6) ◽  
Author(s):  
Claudia Paez ◽  
Jason A. Smith
Keyword(s):  
Water Stress ◽  
Tree Species ◽  
Soil Compaction ◽  
Urban Areas ◽  
Root Disease ◽  
Poor Health ◽  
Green Spaces ◽  
Opportunistic Pathogens ◽  
Wide Range ◽  
Quercus Spp

Biscogniauxia canker or dieback (formerly called Hypoxylon canker or dieback) is a common contributor to poor health and decay in a wide range of tree species (Balbalian & Henn 2014). This disease is caused by several species of fungi in the genus Biscogniauxia (formerly Hypoxylon). B. atropunctata or B. mediterranea are usually the species found on Quercus spp. and other hosts in Florida, affecting trees growing in many different habitats, such as forests, parks, green spaces and urban areas (McBride & Appel, 2009).  Typically, species of Biscogniauxia are opportunistic pathogens that do not affect healthy and vigorous trees; some species are more virulent than others. However, once they infect trees under stress (water stress, root disease, soil compaction, construction damage etc.) they can quickly colonize the host. Once a tree is infected and fruiting structures of the fungus are evident, the tree is not likely to survive especially if the infection is in the tree's trunk (Anderson et al., 1995).

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