scholarly journals Amazon landforms and soils in relation to biological diversity

2000 ◽  
Vol 30 (1) ◽  
pp. 81-81 ◽  
Author(s):  
Wim Sombroek
Keyword(s):  
Cross Section ◽  
Vegetation Structure ◽  
Biological Diversity ◽  
Small Scale ◽  
Floristic Diversity ◽  
Forest Refuge ◽  
Schematic Cross Section ◽  
Soil Pattern ◽  
Landform Units ◽  
Refuge Areas

Thirteen main landform units are distinguished for the whole of the forested Amazon region, each with its specific soil pattern and vegetation structure. These landform-soil-vegetation units are delineated on a small-scale map and illustrated by a schematic cross-section. Floristic diversity of the gamma type is to be highest on the steepland-and-valley complexes of the Andean fringe, on the crystalline shield uplands, on the inselberg complexes, and on the eutric variant of the western sedimentary plains. Endemism is expected to be highest on the sandy plains, and parts of the table lands and inselberg complexes. Speciation, linked to the concept of forest refuge areas, is likely to be highest on the sandstone table lands, on the stretches of Amazon planalto, and in the areas of relict valleys, in view of the prolonged geomorphological stability of these units.

scholarly journals Mechanical Properties of Spruce Wood Extracted from GLT Beams Loaded by Fire

2021 ◽  
Vol 13 (10) ◽  
pp. 5494
Author(s):  
Lucie Kucíková ◽  
Michal Šejnoha ◽  
Tomáš Janda ◽  
Jan Sýkora ◽  
Pavel Padevět ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Cross Section ◽  
Negative Impact ◽  
Tensile Tests ◽  
Thermal Recovery ◽  
Bending Test ◽  
Small Scale ◽  
Spruce Wood ◽  
The Impact

Heating wood to high temperature changes either temporarily or permanently its physical properties. This issue is addressed in the present contribution by examining the effect of high temperature on residual mechanical properties of spruce wood, grounding on the results of full-scale fire tests performed on GLT beams. Given these tests, a computational model was developed to provide through-thickness temperature profiles allowing for the estimation of a charring depth on the one hand and on the other hand assigning a particular temperature to each specimen used subsequently in small-scale tensile tests. The measured Young’s moduli and tensile strengths were accompanied by the results from three-point bending test carried out on two groups of beams exposed to fire of a variable duration and differing in the width of the cross-section, b=100 mm (Group 1) and b=160 mm (Group 2). As expected, increasing the fire duration and reducing the initial beam cross-section reduces the residual bending strength. A negative impact of high temperature on residual strength has also been observed from simple tensile tests, although limited to a very narrow layer adjacent to the charring front not even exceeding a typically adopted value of the zero-strength layer d0=7 mm. On the contrary, the impact on stiffness is relatively mild supporting the thermal recovery property of wood.

Non-Linear Stress Analysis of Complex Umbilical Cross-Sections

2002 ◽  
Author(s):  
Svein Sævik ◽  
Knut I. Ekeberg
Keyword(s):  
Cross Section ◽  
Axial Force ◽  
Plastic Material ◽  
Axial Strain ◽  
Development Program ◽  
Full Scale ◽  
Small Scale ◽  
Applied Theory ◽  
Element Formulation ◽  
Material Models

Nexans Norway is, together with Marintek, currently developing a software for detailed analysis of complex umbilical cross-section designs. The software development project combines numerical methods with small-scale testing of involved materials, as well as full-scale testing of a wide variety of umbilical designs, essential for calibration and verification purposes. Each umbilical design is modelled and comparisons are made with respect to global behaviour in terms of: • Axial strain versus axial force; • Axial strain versus torsion; • Torsion versus torsion moment for various axial force levels; • Moment versus curvature for different tension levels. The applied theory is based on curved beam and curved axisymmetric thin shell theories. The problem is formulated in terms of finite elements applying the Principle of Virtual Displacements. Each body of the cross-section interacts with the other bodies by contact elements which are formulated by a penalty formulation. The contact elements operate in the local surface coordinate system and include eccentricity, surface stiffness and friction effects. The software is designed to include the following functionality: • Arbitrary geometry modelling including helical elements wound into arbitrary order; • The helical elements may include both tubes and filled bodies; • Elastic, hyper-elastic, and elastic-plastic material models; • Initial strain; • Contact elements, including friction; • Tension, torsion, internal pressure, external pressure, bending and external contact loading (caterpillars, tensioners, etc.). The paper focuses on the motivation behind the development program including a description of the different activities. The theory is described in terms of kinematics, material models and finite element formulation. A test example is further presented comparing predicted behaviour with respect to full-scale test results.

scholarly journals The effects of grazing and mowing on large marsh grasshopper, Stethophyma grossum (Orthoptera: Acrididae), populations in Western Europe: a review

2018 ◽  
Vol 27 (1) ◽  
pp. 91-96 ◽  
Author(s):  
Jacqui Miller ◽  
Tim Gardiner
Keyword(s):  
Vegetation Structure ◽  
Western Europe ◽  
Conservation Management ◽  
Life Stages ◽  
Negative Effects ◽  
Habitat Types ◽  
The Uk ◽  
Grassland Habitats ◽  
Intensity Grazing ◽  
Refuge Areas

The large marsh grasshopper, Stethophymagrossum L. (Orthoptera: Acrididae), has undergone a significant range contraction in the UK and is now restricted to the bogs and mires of the New Forest and Dorset Heaths. In other parts of Western Europe, the species makes use of a wider range of wetland habitat types. Traditionally, many of these habitats would be managed through low intensity grazing, mowing, or both, and these measures are now often employed in the conservation management of wet grassland habitats. This paper reviews the effects of mowing and grazing on S.grossum populations, through looking at the potential impacts (both positive and negative) on different life stages of the grasshopper. Both techniques are valuable in the maintenance of an open and varied vegetation structure which is known to benefit S.grossum in all its life stages. However, grazing on very wet sites or at high intensity can result in trampling of vegetation and S.grossum eggs, and mowing which is too frequent may negatively affect populations through repeated losses of nymphs. Recommendations are given regarding the suitability of mowing and grazing for different habitats and intensity of management to generate the required vegetation structure. Measures are also outlined, such as the provision of unmown or ungrazed refuge areas, which can help reduce negative effects.

scholarly journals Impact of small-scale vegetation structure on tephra layer preservation

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Nick A. Cutler ◽  
Olivia M. Shears ◽  
Richard T. Streeter ◽  
Andrew J. Dugmore
Keyword(s):  
Vegetation Structure ◽  
Small Scale ◽  
Tephra Layer

scholarly journals Living Links Connecting the United Nations Sustainable Development Goals: Small-scale Farmers and Agricultural Biodiversity

2019 ◽  
Vol 6 (3) ◽  
pp. 95-110
Author(s):  
Susan H. Bragdon
Keyword(s):  
Sustainable Development ◽  
Sustainable Development Goals ◽  
Biological Diversity ◽  
Critical Role ◽  
Small Scale ◽  
Agricultural Biodiversity ◽  
Agenda 2030 ◽  
Explicit Mention ◽  
Development Goals ◽  
Small Scale Farmers

The 17 Sustainable Development Goals (SDGs) and Agenda 2030 adopted by the global community in September 2015 are applicable to all countries with the commitment “that no one is left behind.” As an agenda for “people, planet, prosperity, peace and partnership”, Agenda 2030 provides a vision for people and planet-centered, human rights-based, and gender-sensitive sustainable development. It promises “more peaceful and inclusive societies” which are free from fear and violence. Small scale farmers and agricultural biodiversity are critical to the achievement of aspects of most of the SDGs. In addition to being essential for the resilience and stability of agricultural production systems and our ability to adapt to climate change and other stressors; agricultural biodiversity is fundamental to the livelihoods, health and nutrition of billions Despite its importance to the health of both people and the planet, this broad understanding of what agricultural biological diversity is and the critical role played by its custodians, gets no explicit mention in the SDGs. In fact, awareness of this is low outside specialized institutions and agreements and explicit mention of both is rare in the context of sustainable development This paper uses the example of small-scale farmers and agricultural biodiversity to illustrate how they are the living links amongst the SDGs as well as being critical components in their achievement and to the vision of Agenda 2030.  

Time for 3D: UAV-based lidar for modelling splash erosion under vegetation

2021 ◽  
Author(s):  
Johannes Antenor Senn ◽  
Steffen Seitz ◽  
Fabian Ewald Fassnacht ◽  
Zahra Hosseini ◽  
Jannika Schäfer
Keyword(s):  
Kinetic Energy ◽  
Leaf Litter ◽  
Vegetation Structure ◽  
Plant Traits ◽  
3D Structure ◽  
Protective Layer ◽  
Point Clouds ◽  
Small Scale ◽  
Initial Results ◽  
Covering Vegetation

<p>Rain throughfall under vegetation is determined by characteristics of the vertical structure and the associated plant traits. It goes both ways: A protective layer of ground covering vegetation or leaf litter can decrease throughfall kinetic energy (TKE), whereas the formation of large drips in the canopy layers has been found to increase TKE. Abstracting the three-dimensional vegetation structure into usable quantitative metrics is challenging, and therefore these processes have not yet been sufficiently integrated into spatial erosion models. The vegetation splash factor (VSF) was designed to close this gap (Senn et al. 2020, DOI: 10.1002/esp.4820). The VSF quantifies the influence of vegetation on TKE and can be calculated from aerial lidar point clouds. In the first step, we derive the vegetation cover in a voxel space, which then allows modelling the proportional contribution of drips per layer to reach the ground. Hence, the approach is strictly based on the 3D structure rather than conventional forestry parameters, e.g. crown diameter or leaf sizes. Here, we present the result of the first application of the VSF in a small scale field study using splash cup measurements to validate and refine the concept.</p><p>We implemented the experiment in a mixed-broadleaf forest near Bretten, Germany with a beech and an oak-dominated plot to cover a variety of vertical forest structure configurations and a diverse composition of species. Each plot comprised two transects of ten splash cups to measure sand loss - as a proxy for TKE - during six individual rainfall events. In addition, we used micro-scale runoff plots to determine the effect of soil covering layers such as leaf litter or biological soil crusts in comparison to bare soil. The VSF was calculated in R with a voxel resolution of 0.5 x 0.5 x 0.25 m using a UAV lidar dataset. </p><p>Initial results from the splash cup measurements showed that young oak induced about 70 % higher TKE than adult beech trees. Among the individual cup positions, the lowest energy values were measured without canopy influence as freefall kinetic energy (FKE), TKE at positions with an intermediate young growth and shrub layer showed medium values. In near-trunk and mid-positions without intermediate layers, we measured TKE values more than twice as high as FKE. This resulted in significant sediment removal beneath the tree layer when the ground covering vegetation layer was removed, which is in accordance with studies from other ecosystems. Grouped according to these conventional vegetation structural criteria, we found that the calculated VSF values clustered around similar values and correlated with sand loss from splash cups. From these initial results, we assume general suitability of the VSF to reflect the influence of vegetation structure on TKE. Further, more detailed analysis will now be done to adjust and calibrate the VSF model to produce more indicative results. The preliminary findings presented here will be further expanded to be presented at vEGU21.</p>

Meandering channels over ice: Cooler and unique?

2021 ◽  
Author(s):  
Roberto Fernández
Keyword(s):  
Cross Section ◽  
Experimental Work ◽  
Small Scale ◽  
Field Observations ◽  
Meandering Channels ◽  
Ongoing Work ◽  
Similarities And Differences ◽  
Coefficient Of Skewness ◽  
Cross Section Geometry

<p>Experimental work on small-scale meltwater meandering channels over ice and field observations have identified similarities and differences between their planform morphologies and those of meandering channels in other media (e.g. alluvial, bedrock). Qualitatively and quantitatively, planform characteristics, including sinuosity, wavelength-to-width ratios, coefficient of skewness and fatness, suggest that most meandering channels behave in certain ways and within certain ranges. However, what makes meltwater meandering channels over ice unique? In this contribution, I highlight the different aspects that set meltwater meandering channels over ice apart from meandering channels in other media and share ongoing work focusing in their planform morphologies, curvature signals, and cross section geometry.</p>

scholarly journals Snowdrift modelling in a wind tunnel: vertical and horizontal variation of the snow flux

1998 ◽  
Vol 26 ◽  
pp. 212-216 ◽  
Author(s):  
Florence Naaim-Bouvet ◽  
Mohamed Naaim
Keyword(s):  
Wind Tunnel ◽  
Cross Section ◽  
Critical Examination ◽  
Small Scale ◽  
Geometrical Parameters ◽  
Drifting Snow ◽  
Horizontal Variation ◽  
Storm Duration ◽  
Recent Developments ◽  
Mean Wind Speed

This paper deals with the influence of the vertical and horizontal variation of Aeolian snow flux on estimations of snow-storm duration and on snowdrift patterns simulated in a wind tunnel.First of all, we shall review recent developments, including our own simulations, concerning the horizontal increase of mass flux until drifting-snow saturation has been reached.Next, after a critical examination of various snowdrift-modelling criteria, we present the results of an experiment undertaken in our wind tunnel: We studied cross-section drill-area changes behind a small-scale snow fence as a function of time for different fetches but for the same mean wind speed at the beginning of the testing section. For each fetch, we carried out vertical profiles of sand particles using image processing and we studied the geometrical parameters of the drift. We conclude dial changes in the cross-section drift area depend on the ablation length and if particle saturation is not reached, the use of a storm-duration scale leads to Overevaluation of prototype storm duration. Moreover, we point out that drift pattern vary as a function of the concentration profiles.

scholarly journals The Role of Traditional Livelihood Practices and Local Ethnobotanical Knowledge in Mitigating Chestnut Disease and Pest Severity in Turkey

Forests ◽  
2019 ◽  
Vol 10 (7) ◽  
pp. 571 ◽  
Author(s):  
Jeffrey Wall ◽  
Coşkun Köse ◽  
Nesibe Köse ◽  
Taner Okan ◽  
Elif Başak Aksoy ◽  
...  
Keyword(s):  
Biological Diversity ◽  
Multiple Correspondence Analysis ◽  
Disease Outbreaks ◽  
Agroforestry Systems ◽  
Anthropogenic Factors ◽  
Small Scale ◽  
Multiple Factor Analysis ◽  
Tree Health ◽  
Chestnut Tree ◽  
Maintenance Of Diversity

The European chestnut population is enduring multiple compounding exotic pest and disease outbreaks across Turkey. The deeply held value of the chestnut species for the Turkish public is reflected in substantial government conservation programming. Chestnut is predominantly found on state land managed by Turkey’s General Directorate of Forestry (GDF), which generally upholds restrictive policies for chestnut-related livelihood practices other than nut collection and beehive placement. Such policies are justified by a government position that human activities and presence is likely to worsen disease dynamics. Conversely, a growing body of research findings testify that small-scale livelihood practices maintain biological diversity and, furthermore, that this traditional maintenance of diversity has been correlated with decreased pathogen pressure within agroecosystems. However, few studies have investigated this phenomenon in the context of agroforestry systems. At a global ecological moment of increasingly pervasive and severe exotic forest pathogen impact, this paper investigates the influence of diverse small-scale livelihood practices and knowledge on chestnut tree health across the highly heterogenous geography of Turkey. We conducted ethnobotanical questionnaires with 96 chestnut-utilizing households, and chestnut tree health evaluations in georeferenced forest areas they identified, throughout Turkey’s Black Sea, Marmara, and Aegean regions. Using data from 1500 trees, we characterized the effects of subsequently recorded environmental, physiological, and anthropogenic factors on tree health using multiple correspondence analysis (MCA), multiple factor analysis (MFA), and mixed models. Our results show that the traditional human management of tree physiology and ecology has a significant positive effect on tree health, especially through the acts of grafting and culling as well as the maintenance of diversity. We argue that conceptualizing such livelihood systems as human niche construction and maintenance can help forest management agencies to better understand and conserve valuable landscapes, even in increasingly common periods of severe pathogenic pressure.

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