scholarly journals Ecological and Structural Characteristics of Riparian Forest in Omo Biosphere Reserve

2020 ◽  
Vol 24 (9) ◽  
pp. 1687-1691
Author(s):  
O.R. Olatidoye ◽  
O.J. Oyelowo ◽  
O.D. Akinyemi ◽  
C. Kambai ◽  
A.A. Ayodele
Keyword(s):  
Riparian Forest ◽  
Structural Characteristics ◽  
Biosphere Reserve ◽  
Basal Area ◽  
Riparian Forests ◽  
Diameter Class ◽  
Species Dominance ◽  
The Core ◽  
Class Distribution ◽  
Major River

An investigation on the structural characteristics of the riparian forest in Omo Biosphere Reserve was carried out. The structure was analyzed  through diameter class distribution, basal area and breast height. Riparian forest showed a major characteristic in the physiognomy of forests along major river, streams and Upland vegetation and the Core, Buffer and Transition zones that is highly variable in the diameter class distribution  (reserve J type), Mean basal area per hectare for major river is 294,089.30 cm2/ ha, Stream 613.027 cm2/ha, and Upland 205,648 cm3/ha. Mean basal area for core is 507,399.50 cm2/ha, buffer had 340,699 cm2/ha and transition 264,656 cm2/ha. While mean volume per hectare for core is 7955.2 m3/ha, buffer 7260 m3/ha and Transition 6254.4 m3/ha. Maximum dbh of 246 cm was obtained in the core species. Many stands of riparian forests are facing various levels of structural and floristic simplification, which include fundamental transformations in vegetation physiognomy from dense stands to riparian scrub or bare land. Keyword: Riparian forests, structure, diameter, basal area, species dominance, Omo

scholarly journals Frost Crack Incidence in Northern Hardwood Forests of the Southern Boreal–North Temperate Transition Zone

2008 ◽  
Vol 25 (3) ◽  
pp. 133-138 ◽  
Author(s):  
Julia I. Burton ◽  
Eric K. Zenner ◽  
Lee E. Frelich
Keyword(s):  
Structural Characteristics ◽  
Regional Climate ◽  
Small Diameter ◽  
Basal Area ◽  
Selective Logging ◽  
Tree Level ◽  
Diameter Class ◽  
Northern Hardwood ◽  
Second Growth ◽  
Small Diameter Trees

Abstract Frost cracks are common in northern hardwood stands near their northern range limits. Although they have long been attributed to the regional climate, temperature fluctuations result in surface cracks largely when internal wounds are present. We examined the relationship between the proportion of trees with frost cracks and both tree-level diameter class and stand structural characteristics in primary stands with a history of minimal logging (n = 4) and 67- to 97-year-old second-growth stands subjected to past heavy partial cuts and high grading (n = 8). We hypothesized that frost crack incidence would (1) be greater in the second-growth stands and (2) be associated with differences in structural attributes between the two stand types. High levels of frost cracking in primary stands indicated that cracks are not completely avoidable. However, the proportion of trees with frost cracks was significantly higher in second-growth than primary stands, particularly on small-diameter trees. For example, the odds for frost cracking were 1.66–3.74 times greater in second-growth than in primary stands in the 15-cm diameter class, but were not different in the 45+-cm diameter class. Frost cracking was positively associated with increasing diameter in both stand types. Structural characteristics reflecting tree size, stand basal area, and basal area of hardwoods were positively associated with the proportion of trees with frost cracks in second-growth stands but not in primary stands. Although the basal area of conifers was negatively associated with frost cracking, the effect was likely due to a reduction in hardwood basal area in the vicinity of conifers. We suggest that greater frost crack incidence in second-growth stands is likely a consequence of injuries to residual trees during selective logging.

scholarly journals Structural Characteristics of Natural Limestone Forests in Cat Ba Biosphere Reserves, Vietnam

2020 ◽  
pp. 161-172
Author(s):  
Tran Hai Long ◽  
I. M. Sangjun ◽  
Trieu Thai Hung ◽  
Qiwen Li ◽  
Ninh Viet Khuong ◽  
...  
Keyword(s):  
Species Richness ◽  
Sustainable Forest Management ◽  
Structural Characteristics ◽  
Biosphere Reserve ◽  
Basal Area ◽  
Diameter Distribution ◽  
Height Distribution ◽  
Natural Forests ◽  
Clear Cut ◽  
Anthropogenic Intervention

An ecological understanding of natural forests after anthropogenic intervention is important for sustainable forest management. This study analyzed the overstory characteristics (species composition, growth, and diameter distribution) and regeneration (species richness, density, and height distribution) in natural limestone forests in Cat Ba Biosphere Reserve, Vietnam. Data were collected in nine study plots established in selective-logged (SLF), clear-cut (CCF), and unlogged (UF) forests. Results indicated that the overstory characteristics of SLF and CCF were lower than that of UF (species richness was 33 in UF, 20 in SLF, and 16 in CCF; DBH was 20.6 ±13.7 cm in UF, 16.9 ±9.7 cm in SLF, and 10.5 ±3.8 cm in CCF; Basal area was 38.2 m2 ha-1 in UF, 24.0 m2 ha-1 in SLF, and 11.4 m2 ha-1 in CCF). For regeneration, species richness also varied from UF (25) to SLF (13) and CCF (5), while seedling density reversely increased. We concluded that a 20-year restoration was insufficient for artificially disturbed forests to recover their ecological functions, regardless of logging intensities and techniques applied.

Riparian forest conditions along three northern Michigan rivers following Emerald Ash Borer invasion

2020 ◽  
Vol 50 (8) ◽  
pp. 800-810
Author(s):  
Patrick J. Engelken ◽  
Deborah G. McCullough
Keyword(s):  
Riparian Forest ◽  
Emerald Ash Borer ◽  
Basal Area ◽  
Agrilus Planipennis ◽  
Riparian Forests ◽  
Tree Seedlings ◽  
Fraxinus Pennsylvanica ◽  
Fraxinus Nigra ◽  
The Stability ◽  
Three Rivers

Emerald Ash Borer (EAB; Agrilus planipennis Fairmaire (Coleoptera, Buprestidae)) has killed millions of ash (Fraxinus spp.) trees since its 2002 detection in southern Michigan and Ontario. Effects of EAB in riparian forests, where ash species are often abundant, could influence terrestrial and aquatic conditions but are largely unknown. We surveyed vegetation and coarse woody material within and between three gaps in riparian forests along stretches of three rivers in northwestern Michigan. Gaps were originally dominated by Fraxinus pennsylvanica Marsh. and Fraxinus nigra Marsh., which comprised 46%–71% of total basal area, while ash comprised <10% of basal area in forests between gaps. More than 95% of overstory ash were killed by EAB. Fraxinus pennsylvanica saplings were abundant in gaps but F. nigra regeneration was minimal. Few tree seedlings occurred in gaps, which were dominated by dense sedge mats. Aerial imagery showed the EAB invasion has resulted in 3.6–7.1 canopy gaps·km−1 and dead ash account for 13%–21% of total basal area within 100 m of the banks of all three rivers. Long-term monitoring will be useful to evaluate persistence of ash, particularly F. nigra, the stability of riparian buffers, and potential indirect effects of EAB invasion on the adjacent aquatic systems.

Nauwkeurige methode voor de aanwasbepaling van het grondvlak met behulp van de Pressler-boor

1968 ◽  
Vol 12 ◽  
Author(s):  
R. Goossens
Keyword(s):  
Basal Area ◽  
Precise Determination ◽  
Maximum Diameter ◽  
Precise Method ◽  
Maximum Radius ◽  
The Core ◽  
Two Parameters

A precise method for the determination of the increment of the  basal area using the PressIer bore. Refering to  previous research showing that the basal area of the corsica pine could be  characterized by an ellips, we present in this paper a precise method for the  determination of the increment of the basal area. In this method we determine  the direction of the maximum diameter, we measure this diameter and we take a  core in one of the points of tangency of the caliper with the measured tree.  The determination of the diameter perpendicular to the maximum diameter  finishes the work wich is to be done in the forest. From the classical  measurements effectuated on the core and from the measured diameters we can  then determine the form (V) and the excentricity (e). Substituting these two  parameters in the formula 2 or 2', we can also calculate the error of a  radius measured on the core with respect to the representative radius, This  error with them allow us to correct the measured value of the minimum or the  maximum radius and we will be able to do a precise determination of the  increment.

scholarly journals Water-use dynamics of an alien-invaded riparian forest within the Mediterranean climate zone of the Western Cape, South Africa

2017 ◽  
Vol 21 (9) ◽  
pp. 4551-4562 ◽  
Author(s):  
Bruce C. Scott-Shaw ◽  
Colin S. Everson ◽  
Alistair D. Clulow
Keyword(s):  
South Africa ◽  
Water Use ◽  
Sap Flow ◽  
Riparian Forest ◽  
Riparian Forests ◽  
Ratio Method ◽  
Natural State ◽  
Indigenous Species ◽  
Western Cape ◽  
Selection Of

Abstract. In South Africa, the invasion of riparian forests by alien trees has the potential to affect the country's limited water resources. Tree water-use measurements have therefore become an important component of recent hydrological studies. It is difficult for South African government initiatives, such as the Working for Water (WfW) alien clearing program, to justify alien tree removal and implement rehabilitation unless hydrological benefits are known. Consequently, water use within a riparian forest along the Buffeljags River in the Western Cape of South Africa was monitored over a 3-year period. The site consisted of an indigenous stand of Western Cape afrotemperate forest adjacent to a large stand of introduced Acacia mearnsii. The heat ratio method of the heat pulse velocity sap flow technique was used to measure the sap flow of a selection of indigenous species in the indigenous stand, a selection of A. mearnsii trees in the alien stand and two clusters of indigenous species within the alien stand. The indigenous trees in the alien stand at Buffeljags River showed significant intraspecific differences in the daily sap flow rates varying from 15 to 32 L day−1 in summer (sap flow being directly proportional to tree size). In winter (June), this was reduced to only 7 L day−1 when limited energy was available to drive the transpiration process. The water use in the A. mearnsii trees showed peaks in transpiration during the months of March 2012, September 2012 and February 2013. These periods had high average temperatures, rainfall and high daily vapor pressure deficits (VPDs – average of 1.26 kPa). The average daily sap flow ranged from 25 to 35 L in summer and approximately 10 L in the winter. The combined accumulated daily sap flow per year for the three Vepris lanceolata and three A. mearnsii trees was 5700 and 9200 L, respectively, clearly demonstrating the higher water use of the introduced Acacia trees during the winter months. After spatially upscaling the findings, it was concluded that, annually, the alien stand used nearly 6 times more water per unit area than the indigenous stand (585 mm a−1 compared to 101 mm a−1). This finding indicates that there would be a gain in groundwater recharge and/or streamflow if the alien species are removed from riparian forests and rehabilitated back to their natural state.

A Constructivist Framework for Understanding Entrepreneurship Performance

1993 ◽  
Vol 14 (4) ◽  
pp. 549-570 ◽  
Author(s):  
Hamid Bouchikhi
Keyword(s):  
Structural Characteristics ◽  
Complex Interaction ◽  
Entrepreneurial Process ◽  
The Core ◽  
Prior Performance ◽  
Chance Events

This paper outlines a constructivist framework for understanding the outcomes of the entrepreneurial process. The core thesis of the paper is that, taken alone, neither the personality of the entrepreneur nor the structural characteristics of the environment determine the outcome. Rather, it is argued that the outcome of the entrepreneurial process is emergent from a complex interaction between the entrepreneur, the environment, chance events and prior performance. The framework is illustrated with evidence from biographies of six entrepreneurs involved in successful processes.

Relationship between Morphology and Trophic Ecology in an Assemblage of Passerine Birds in Riparian Forests of the Paraná River (Argentina)

2018 ◽  
Vol 11 (1) ◽  
pp. 44-53 ◽  
Author(s):  
Virginia Quiroga ◽  
Rodrigo E. Lorenzón ◽  
Gisela Maglier ◽  
Ana L. Ronchi-Virgolini
Keyword(s):  
Trophic Ecology ◽  
Riparian Forest ◽  
A Priori ◽  
Bird Species ◽  
Morphological Characteristics ◽  
Paraná River ◽  
Riparian Forests ◽  
Phylogenetic Constraint ◽  
Parana River ◽  
Coexisting Species

We describe the ecomorphology of an assemblage of bird species found in riparian forests of the Middle Paraná River, Argentina. We sought to determine (1) the more important morphological characteristics that separate coexisting species, (2) whether such separation was related to the trophic ecology of each species and (3) whether a priori guilds showed morphological similarity. We tested the hypotheses that (a) a species’ morphology is related to the trophic ecology of that species and (b) that species of a priori guilds are morphometrically more similar to each other than to species of different a priori guilds. For this, we considered an assemblage of 29 species of birds from riparian forest that were sampled with mist nets during the 2011 and 2014 breeding seasons. We obtained morphometric measurements of captured individuals and supplemented those data with measurements from museum specimens. Trophic characterisation (diet and trophic microhabitat) was based on a literature review. Results showed a separation of bird species as a function of variables related to trophic ecology (diets and trophic microhabitats) and morphology. After controlling for phylogenetic constraint, species’ morphology partially reflected the trophic ecology of the species, supporting the central hypothesis of the ecomorphological discipline and showing that the use of trophic and morphometric data provides complementary data to improve the guild organisation of riparian bird assemblages.

scholarly journals Long-term challenge to mangrove in the National park Xuanthuy – data released from shallow subsidence monitoring

2018 ◽  
Vol 34 (3) ◽  
Author(s):  
Le Xuan Thuyen
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
National Park ◽  
Low Cost ◽  
River Mouth ◽  
Biosphere Reserve ◽  
The United States ◽  
Red River ◽  
United States Geological Survey ◽  
The Core

A small mangrove colony growing for several decades on a mud flat on the left side of Balat River mouth has become today a large and healthy forest, containing a high ecosystem service value in the core of the Red River biosphere reserve. As a pioneer ecosystem located at land– water interface in the tropic, there exist always risks to mangroves, especially due to climate change and sea level rise. Sea level rise is a worldwide process, but subsidence is a local problem that can exacerbate these geo-hazards. A monitoring of shallow subsidence has been carried out by using SET-MH technique (developed by the United States Geological Survey) to track the both accretion and land sinking in the core zone of the National Park. The measurement shows the average sedimentation rate of 2.9 cm / yr and the sinking rate of 3.4 cm / yr, since Dec. 30th 2012. This is the first ground-based observation of shallow subsidence under mangroves in the Tonkin Gulf. As a simple and low cost method, so further expansion of this monitoring could provide more useful information to help identify the generally sinking trend of coastal areas in the Red River Delta and also to protect its own biosphere reserve.

Structure and composition of unmanaged riparian forests in the coastal mountains of Oregon, U.S.A.

1999 ◽  
Vol 29 (10) ◽  
pp. 1557-1573 ◽  
Author(s):  
Robert J Pabst ◽  
Thomas A Spies
Keyword(s):  
Spatial Scales ◽  
Canopy Cover ◽  
Basal Area ◽  
Tree Regeneration ◽  
Riparian Forests ◽  
Stream Order ◽  
Third Order ◽  
First Order ◽  
Hardwood Tree ◽  
Stand Attributes

We characterized the structure and composition of unmanaged riparian forests in three river basins in Oregon's coastal mountains. Our objective was to evaluate stand attributes at three spatial scales: streamside (site), drainage network (stream order), and basin (subregion). Data on basal area, species composition, snag density, canopy cover, and tree regeneration were collected along transects at 124 sites. Conifer basal area increased with distance from stream, a trend similar among subregions, and was highest at sites along first-order streams. Hardwood basal area was relatively constant with distance from stream and was proportionally higher at sites along second- and third-order streams than at sites along first-order streams. Conifer and hardwood tree regeneration occurred infrequently and varied by topographic position, stream order, and subregion. Conifer regeneration was associated with basal area of shade-tolerant conifers and appeared to be limited by shrub competition. The unmanaged forests we studied were characterized by a patchy mosaic of structure and composition. Hardwoods and shrubs were major components of the near-stream environment in these forests, whereas dominance of conifers was limited to hillslopes. It appears that fine-scale patterns associated with proximity to the stream are influenced by coarser scale factors such as valley-floor width and climate.

scholarly journals Electron Cryotomography Studies of Maturing HIV-1 Particles Reveal the Assembly Pathway of the Viral Core

2014 ◽  
Vol 89 (2) ◽  
pp. 1267-1277 ◽  
Author(s):  
Cora L. Woodward ◽  
Sarah N. Cheng ◽  
Grant J. Jensen
Keyword(s):  
Viral Genome ◽  
Virus Assembly ◽  
Structural Characteristics ◽  
Hexagonal Lattice ◽  
The Body ◽  
The Core ◽  
Assembly Pathway ◽  
Viral Particles ◽  
Electron Cryotomography ◽  
Hiv 1

ABSTRACTTo better characterize the assembly of the HIV-1 core, we have used electron cryotomography (ECT) to image infected cells and the viral particles cryopreserved next to them. We observed progressive stages of virus assembly and egress, including flower-like flat Gag lattice assemblies, hemispherical budding profiles, and virus buds linked to the plasma membrane via a thin membrane neck. The population of budded viral particles contains immature, maturation-intermediate, and mature core morphologies. Structural characteristics of the maturation intermediates suggest that the core assembly pathway involves the formation of a CA sheet that associates with the condensed ribonucleoprotein (RNP) complex. Our analysis also reveals a correlation between RNP localization within the viral particle and the formation of conical cores, suggesting that the RNP helps drive conical core assembly. Our findings support an assembly pathway for the HIV-1 core that begins with a small CA sheet that associates with the RNP to form the core base, followed by polymerization of the CA sheet along one side of the conical core toward the tip, and then closure around the body of the cone.IMPORTANCEDuring HIV-1 assembly and release, the Gag polyprotein is organized into a signature hexagonal lattice, termed the immature lattice. To become infectious, the newly budded virus must disassemble the immature lattice by proteolyzing Gag and then reassemble the key proteolytic product, the structural protein p24 (CA), into a distinct, mature hexagonal lattice during a process termed maturation. The mature HIV-1 virus contains a conical capsid that encloses the condensed viral genome at its wide base. Mutations or small molecules that interfere with viral maturation also disrupt viral infectivity. Little is known about the assembly pathway that results in the conical core and genome encapsidation. Here, we have used electron cryotomography to structurally characterize HIV-1 particles that are actively maturing. Based on the morphologies of core assembly intermediates, we propose that CA forms a sheet-like structure that associates with the condensed viral genome to produce the mature infectious conical core.

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