scholarly journals Classification and mapping of the composition and structure of dry woodland and savanna in the eastern Okavango Delta

Koedoe ◽  
2013 ◽  
Vol 55 (1) ◽  
Author(s):  
Michelle J. Tedder ◽  
Kevin P. Kirkman ◽  
Craig D. Morris ◽  
Winston S.W. Trollope ◽  
Mpaphi C. Bonyongo
Keyword(s):  
Woody Species ◽  
Hierarchical Cluster ◽  
Okavango Delta ◽  
Background Information ◽  
Grass Species ◽  
Panicum Maximum ◽  
Vegetation Types ◽  
Agglomerative Hierarchical Cluster Analysis ◽  
Dry Woodland ◽  
Mopane Woodland

The dry woodland and savanna regions of the Okavango Delta form a transition zone between the Okavango Swamps and the Kalahari Desert and have been largely overlooked in terms of vegetation classification and mapping. This study focused on the species composition and height structure of this vegetation, with the aim of identifying vegetation classes and providing a vegetation map accompanied by quantitative data. Two hundred and fifty-six plots (50 m × 50 m) were sampled and species cover abundance, total cover and structural composition were recorded. The plots were classified using agglomerative, hierarchical cluster analysis using group means and Bray-Curtis similarity and groups described using indicator species analysis. In total, 23 woody species and 28 grass species were recorded. Acacia erioloba and Colophospermum mopane were the most common woody species, whilst Urochloa mossambicensis, Panicum maximum, Dactyloctenium gigantiumand Eragrostis lehmanniana were the most widespread grasses. Eleven vegetation types were identified, with the most widespread being Short mixed mopane woodland, Tall mopane woodland and Tall mixed mopane woodland, covering 288.73 km2 (28%), 209.14 km2 (20%) and 173.30 km2 (17%) of the area, respectively. Despite their extensive area, these three vegetation types were the least species-rich, whilst Palm thornveld, Short mixed broadleaf woodland and Open mixed Acacia woodland were the most taxonomically variable. By contrast, Closed mixed Acacia woodland and Closed Acacia–Combretum woodland had the most limited distribution, accounting for less than 1% of the mapped area each.Conservation implications: The dry woodland and savanna vegetation of the Okavango Delta comprises a much wider suite of plant communities than the Acacia-dominated and Mopane-dominated classifications often used. This classification provided a more detailed understanding of this vegetation and essential background information for monitoring, management and research.

scholarly journals Constraint-Based Hierarchical Cluster Selection in Automotive Radar Data

Sensors ◽  
2021 ◽  
Vol 21 (10) ◽  
pp. 3410
Author(s):  
Claudia Malzer ◽  
Marcus Baum
Keyword(s):  
Moving Objects ◽  
Hierarchical Cluster ◽  
Autonomous Driving ◽  
Radar Data ◽  
Background Information ◽  
Automotive Radar ◽  
Data Set ◽  
Radar Sensors ◽  
Small Clusters ◽  
Cluster Level

High-resolution automotive radar sensors play an increasing role in detection, classification and tracking of moving objects in traffic scenes. Clustering is frequently used to group detection points in this context. However, this is a particularly challenging task due to variations in number and density of available data points across different scans. Modified versions of the density-based clustering method DBSCAN have mostly been used so far, while hierarchical approaches are rarely considered. In this article, we explore the applicability of HDBSCAN, a hierarchical DBSCAN variant, for clustering radar measurements. To improve results achieved by its unsupervised version, we propose the use of cluster-level constraints based on aggregated background information from cluster candidates. Further, we propose the application of a distance threshold to avoid selection of small clusters at low hierarchy levels. Based on exemplary traffic scenes from nuScenes, a publicly available autonomous driving data set, we test our constraint-based approach along with other methods, including label-based semi-supervised HDBSCAN. Our experiments demonstrate that cluster-level constraints help to adjust HDBSCAN to the given application context and can therefore achieve considerably better results than the unsupervised method. However, the approach requires carefully selected constraint criteria that can be difficult to choose in constantly changing environments.

scholarly journals Do Sandy Grasslands along the Danube in the Carpathian Basin Preserve the Memory of Forest-Steppes?

Forests ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 114
Author(s):  
Károly Penksza ◽  
Dénes Saláta ◽  
Gergely Pápay ◽  
Norbert Péter ◽  
Zoltán Bajor ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Carbon Content ◽  
Carpathian Basin ◽  
Grass Species ◽  
Carbonate Content ◽  
Forest Steppe ◽  
Organic Carbon Content ◽  
Vegetation Types ◽  
Sandy Grasslands ◽  
Dominant Grass

Research highlights: In the present survey we examined the sandy grasslands appearing in the steppe-forest-steppe vegetation in the central part of the Carpathian Basin along the Danube. Background and objectives: We aimed to answer the following questions: Is it possible to build a picture of the past form of the vegetation through the examination of these vegetation units based on dominant grass taxa? Is Festuca wagneri an element of open grasslands or steppes? According to our hypothesis, these surveys can help reveal the original or secondary woody, shrubby patches through clarifying dominant taxa. Materials and Methods: We studied the grasslands in terms of coenology, putting great emphasis on the dominant Festuca taxa. Based on our preliminary surveys and literature, three vegetation types can be separated based on one single dominant Festuca taxon in each. The survey was conducted in four different locations in the Carpathian Basin. The cover of dominant grass species was used as an indicator value. The pedological background was also examined. Results: F. vaginata grassland is an open vegetation type based on its coenosystematic composition and ecological values. It grows in very weakly developed calcareous soil with sandy texture, with its lowest and highest organic carbon content ranging from 0.2% to 11.3% (0.2%), and the highest carbonate content (11.3%). Where the grasslands were disturbed, F. pseudovaginata and the recently discovered F. tomanii appeared. These taxa were also found in forest patches. The soil under F. pseudovaginata was more developed, in the surface horizon with higher organic carbon content (1.1%) and lower carbonate content (6.9%). The soil profile under F. wagneri developed the most, as the presence of deep and humus rich soil material from deflation and degradation showed. Conclusions: the dominant Festuca taxa of these vegetation types are good indicators of the changes in the vegetation and their ecological background.

scholarly journals Taste Interactions between Sweetness of Sucrose and Sourness of Citric and Tartaric Acid among Chinese and Danish Consumers

Foods ◽  
2020 ◽  
Vol 9 (10) ◽  
pp. 1425
Author(s):  
Jonas Yde Junge ◽  
Anne Sjoerup Bertelsen ◽  
Line Ahm Mielby ◽  
Yan Zeng ◽  
Yuan-Xia Sun ◽  
...  
Keyword(s):  
Citric Acid ◽  
Tartaric Acid ◽  
Hierarchical Cluster ◽  
Taste Perception ◽  
Aqueous Samples ◽  
Chinese Consumers ◽  
Consumer Study ◽  
Agglomerative Hierarchical Cluster Analysis ◽  
Significant Difference ◽  
Sweetness Intensity

Tastes interact in almost every consumed food or beverage, yet many aspects of interactions, such as sweet-sour interactions, are not well understood. This study investigated the interaction between sweetness from sucrose and sourness from citric and tartaric acid, respectively. A cross-cultural consumer study was conducted in China (n = 120) and Denmark (n = 139), respectively. Participants evaluated six aqueous samples with no addition (control), sucrose, citric acid, tartaric acid, or a mixture of sucrose and citric acid or sucrose and tartaric acid. No significant difference was found between citric acid and tartaric acid in the suppression of sweetness intensity ratings of sucrose. Further, sucrose suppressed sourness intensity ratings of citric acid and tartaric acid similarly. Culture did not impact the suppression of sweetness intensity ratings of citric or tartaric acid, whereas it did influence sourness intensity ratings. While the Danish consumers showed similar suppression of sourness by both acids, the Chinese consumers were more susceptible towards the sourness suppression caused by sucrose in the tartaric acid-sucrose mixture compared to the citric acid-sucrose mixture. Agglomerative hierarchical cluster analysis revealed clusters of consumers with significant differences in sweetness intensity ratings and sourness intensity ratings. These results indicate that individual differences in taste perception might affect perception of sweet-sour taste interactions, at least in aqueous solutions.

scholarly journals Recovery of Trichostrongylus colubriformis infective larvae from three grass species contaminated in the autumn

2012 ◽  
Vol 21 (4) ◽  
pp. 372-378 ◽  
Author(s):  
Raquel Abdallah da Rocha ◽  
Patrizia Ana Bricarello ◽  
Gilberto Pedroso da Rocha ◽  
Alessandro Francisco Talamini do Amarante
Keyword(s):  
Dry Matter ◽  
Cynodon Dactylon ◽  
Larval Survival ◽  
Grass Species ◽  
Panicum Maximum ◽  
Free Living ◽  
Trichostrongylus Colubriformis ◽  
Brachiaria Decumbens ◽  
Infective Larvae ◽  
Experimental Plots

This experiment aimed to assess the recovery of infective larvae (L3) of Trichostrongylus colubriformis from Brachiaria decumbens cv. Australiana, Cynodon dactylon cv. Coast-cross and Panicum maximum cv. Aruana. The experimental module comprised six plots, with two plots per herbage species. Larval survival was assessed from autumn to winter, under the effect of two herbage-paring heights (5 and 30 cm). TThe paring was carried out immediately before contamination with faces containing T. colubriformis eggs. The feces and herbage were collected at one, two, four, eight, 12 and 16 weeks after feces had been deposited in the experimental plots. In general, larvae were recovered from both herbage and feces until the 16th week. The longer persistence of these larvae in the environment was probably due to warmer temperatures. The number of L3 recovered from the pasture was not influenced by the height of plants, except for Brachiaria and Aruana herbage in the fourth week. Regarding the concentrations of larvae per kg of dry matter (L3/kg DM), recovery was higher from low pasture in all three herbage species. During the autumn, the development and survival of the T. colubriformis free-living stages were not affected by the different herbage species.

scholarly journals RESTORATION OF FORMER GRASSLAND IN SOUTH-CENTRAL TEXAS

2019 ◽  
Vol 71 (1) ◽  
Author(s):  
Wendy J. Leonard ◽  
O. W. Van Auken
Keyword(s):  
San Antonio ◽  
Plant Cover ◽  
Woody Species ◽  
Bare Soil ◽  
Grass Species ◽  
Herbaceous Plant ◽  
Percent Cover ◽  
Juniperus Ashei ◽  
South Central ◽  
Central Texas

Abstract In the past, grasslands and savannas were common in many areas of south-central Texas, including the San Antonio area. With the advent of European settlers and their livestock, much of this area was converted to agriculture and rangeland. Today, most of San Antonio is developed, but some preservation has occurred. Restored grassland, mechanically cleared of Juniperus ashei (juniper, Ashe juniper) and other woody species in 2013, was examined and compared to adjacent non-cleared woodland. The woodland examined was dominated by Diospyros texana (Texas persimmon) and Juniperus ashei. Richness in the woodland canopy was 15 species. The understory below the canopy had 25 woody species. In the restored grassland area, herbaceous plant cover was 41.8%, woody plant cover 5.8%, bare soil 2.9%, and litter cover 49.5%. Species richness was 71, with 60 herbaceous and 11 woody species (percent cover of each from <0.1–7.1%). The most common species in the restored grassland in descending order were Nassella leucotricha (Texas winter grass), Calyptocarpus vialis (straggler daisy), Carex planostachys (cedar sedge), Sporobolus crypandrus (sand dropseed), D. texana, and Verbesina virginica (frost weed). Several C4 grass species were present with low cover but may increase in abundance over time. Four of the six most common restored grassland species were present below the woodland canopy and 12 woody species were present in the restored grassland as juveniles. Cost of restoration was approximately $38,500 ($7,500 supplies, $31,000 labor).

scholarly journals Riparian Vegetation Density Mapping of an Extremely Densely Vegetated Confined Floodplain

Hydrology ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 176
Author(s):  
István Fehérváry ◽  
Tímea Kiss
Keyword(s):  
Riparian Vegetation ◽  
Woody Species ◽  
Submerged Vegetation ◽  
Vegetation Types ◽  
Vegetation Density ◽  
Vegetation Zone ◽  
Density Mapping ◽  
Vegetation Zones ◽  
Branch Density ◽  
Vegetation Patches

The most crucial function of lowland-confined floodplains with low slopes is to support flood conveyance and fasten floods; however, obstacles can hinder it. The management of riparian vegetation is often neglected, though woody species increase the vegetation roughness of floodplains and increase flood levels. The aims are (1) to determine the branch density of various riparian vegetation types in the flood conveyance zone up to the level of artificial levees (up to 5 m), and (2) to assess the spatial distribution of densely vegetated patches. Applying a decision tree and machine learning, six vegetation types were identified with an accuracy of 83%. The vegetation density was determined within each type by applying the normalized relative point density (NRD) method. Besides, vegetation density was calculated in each submerged vegetation zone (1–2 m, 2–3 m, etc.). Thus, the obstacles for floods with various frequencies were mapped. In the study area, young poplar plantations offer the most favorable flood conveyance conditions, whereas invasive Amorpha thickets and the dense stands of native willow forests provide the worst conditions for flood conveyance. Dense and very dense vegetation patches are common in all submerged vegetation zones; thus, vegetation could heavily influence floods.

scholarly journals A phytosociological survey of aquatic vegetation in the main freshwater lakes of Greece

2020 ◽  
Vol 1 ◽  
pp. 53-75
Author(s):  
Dimitrios Zervas ◽  
Ioannis Tsiripidis ◽  
Erwin Bergmeier ◽  
Vasiliki Tsiaoussi
Keyword(s):  
Plant Communities ◽  
Aquatic Plant ◽  
Aquatic Vegetation ◽  
Environmental Parameters ◽  
Hierarchical Cluster ◽  
Freshwater Lake ◽  
Vegetation Types ◽  
Freshwater Lakes ◽  
Lake Ecosystems ◽  
The Relationship

Aims: This study aims to contribute to the knowledge of European freshwater lake ecosystems with updated and new information on aquatic plant communities, by conducting national-scale phytosociological research of freshwater lake vegetation in Greece. Moreover, it investigates the relationship between aquatic plant communities and lake environmental parameters, including eutrophication levels and hydro-morphological conditions. Study area: Lakes in Greece, SE Europe. Methods: 5,690 phytosociological relevés of aquatic vegetation were sampled in 18 freshwater lake ecosystems during 2013–2016. The relevés were subjected to hierarchical cluster and indicator species analyses in order to identify associations and communities of aquatic vegetation, as well as to describe their syntaxonomy. Multiple regression analysis was applied to investigate the relationship between vegetation syntaxa and environmental parameters of lakes, i.e. physico-chemical parameters and water level fluctuation. Results: Ninety-nine plant taxa belonging to 30 different families were recorded. Forty-six vegetation types were identified and described by their ecological characteristics, diagnostic taxa and syntaxonomical status. Thirteen vegetation types, the largest number belonging to the vegetation class Charetea, are considered to be new records for Greece. The distribution of the vegetation types recorded in the 18 freshwater lakes was found to depend on environmental parameters and levels of eutrophication. Conclusions: An updated aquatic vegetation inventory was produced for Greek lakes, and primary results showed that the presence/absence of aquatic plant communities and the community composition in freshwater lakes can be utilized to assess the pressure of eutrophication on lake ecosystems. Taxonomic reference: Euro+Med (2006–). Abbreviations: MNT = Mean number of taxa; WFD = Water Framework Directive.

scholarly journals Enhancement of diversity, stand structure and regeneration of woody species through area exclosure: the case of a mopane woodland in northern Botswana

2018 ◽  
Vol 7 (1) ◽  
Author(s):  
Demel Teketay ◽  
Keotshephile Kashe ◽  
Joseph Madome ◽  
Monica Kabelo ◽  
John Neelo ◽  
...  
Keyword(s):  
Stand Structure ◽  
Woody Species ◽  
Mopane Woodland
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