scholarly journals Radiocarbon Analysis Confirms the Annual Nature of Sagebrush Growth Rings

Radiocarbon ◽  
2007 ◽  
Vol 49 (3) ◽  
pp. 1231-1240 ◽  
Author(s):  
Franco Biondi ◽  
Scotty D J Strachan ◽  
Scott Mensing ◽  
Gianluca Piovesan
Keyword(s):  
Great Basin ◽  
Cross Sections ◽  
Environmental Changes ◽  
Spatially Explicit ◽  
Growth Rings ◽  
Ams Radiocarbon Dating ◽  
Big Sagebrush ◽  
Proxy Records ◽  
Annual Resolution ◽  
Wildfire Regimes

In the Great Basin of North America, big sagebrush (Artemisia tridentata Nutt.) growth rings can be used to reconstruct environmental changes with annual resolution in areas where there is otherwise little such information available. We tested the annual nature of big sagebrush wood layers using accelerator mass spectrometry (AMS) radiocarbon dating. Four cross-sections from 3 sagebrush plants were collected near Ely, Nevada, USA, and analyzed using dendrochronological methods. Ten 14C measurements were then used to trace the location of the 1963–64 “bomb spike.” Although the number of rings on each section did not exceed 60, crossdating was possible within a section and between sections. Years assigned to individual wood layers by means of crossdating aligned with their expected 14C values, matching the location of the 14C peak. This result confirmed the annual nature of growth rings formed by big sagebrush, and will facilitate the development of spatially explicit, well-replicated proxy records of environmental change, such as wildfire regimes, in Great Basin valleys.

scholarly journals Identifying Changes in Sediment Texture along an Ephemeral Gravel-Bed Stream Using Electrical Resistivity Tomography 2D and 3D

2021 ◽  
Vol 11 (7) ◽  
pp. 3030
Author(s):  
Marcos A. Martínez-Segura ◽  
Carmelo Conesa-García ◽  
Pedro Pérez-Cutillas ◽  
Pedro Martínez-Pagán ◽  
Marco D. Vásconez-Maza
Keyword(s):  
Electrical Resistivity ◽  
Cross Sections ◽  
Electrical Resistivity Tomography ◽  
Environmental Changes ◽  
Subsurface Layer ◽  
Sediment Texture ◽  
Borehole Data ◽  
Resistivity Tomography ◽  
Gravel Bed ◽  
Basin Scale

Differences in deposit geometry and texture with depth along ephemeral gravel-bed streams strongly reflect fluctuations in bedload which are due to environmental changes at the basin scale and to morphological channel adjustments. This study combines electrical resistivity tomography (ERT) with datasets from borehole logs to analyse the internal geometry of channel cross-sections in a gravel-bed ephemeral stream (southeast Spain). The survey was performed through longitudinal and transverse profiles in the upper channel stretch, of 14 to 30 m in length and 3 to 6 m in depth, approximately. ERT values were correlated with data on sediment texture as grain size distribution, effective grain sizes, sorting, and particle shape (Zingg’s classification). The alluvial channel-fills showed the superposition of four layers with uneven thickness and arrangement: (1) the softer rocky substrate (<1000 Ω.m); (2) a thicker intermediate layer (1000 to 2000 Ω.m); and (3) an upper set composed of coarse gravel and supported matrix, ranging above 2000 Ω.m, and a narrow subsurface layer, which is the most resistive (>5000 Ω.m), corresponding to the most recent armoured deposits (gravel and pebbles). The ERT results coupled with borehole data allowed for determining the horizontal and vertical behaviour of the materials in a 3D model, facilitating the layer identification.

scholarly journals Eastern Andean environmental and climate synthesis for the last 2000 years BP from terrestrial pollen and charcoal records of Patagonia

2015 ◽  
Vol 11 (3) ◽  
pp. 2121-2157 ◽  
Author(s):  
G. D. Sottile ◽  
M. E. Echeverria ◽  
M. V. Mancini ◽  
M. M. Bianchi ◽  
M. A. Marcos ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Environmental Changes ◽  
Fire Regime ◽  
Ice Age ◽  
Circulation System ◽  
Forest Steppe ◽  
Proxy Records ◽  
The Andes ◽  
Precipitation Regimes ◽  
Southern Patagonia

Abstract. The Southern Hemisphere Westerly Winds (SWW) constitute an important zonal circulation system that dominates the dynamics of Southern Hemisphere mid-latitude climate. Little is known about climatic changes in the Southern South America in comparison to the Northern Hemisphere due to the low density of proxy records, and adequate chronology and sampling resolution to address environmental changes of the last 2000 years. Since 2009, new pollen and charcoal records from bog and lakes in northern and southern Patagonia at the east side of the Andes have been published with an adequate calibration of pollen assemblages related to modern vegetation and ecological behaviour. In this work we improve the chronological control of some eastern Andean previously published sequences and integrate pollen and charcoal dataset available east of the Andes to interpret possible environmental and SWW variability at centennial time scales. Through the analysis of modern and past hydric balance dynamics we compare these scenarios with other western Andean SWW sensitive proxy records for the last 2000 years. Due to the distinct precipitation regimes that exist between Northern (40–45° S) and Southern Patagonia (48–52° S) pollen sites locations, shifts on latitudinal and strength of the SWW results in large changes on hydric availability on forest and steppe communities. Therefore, we can interpret fossil pollen dataset as changes on paleohydric balance at every single site by the construction of paleohydric indices and comparison to charcoal records during the last 2000 cal yrs BP. Our composite pollen-based Northern and Southern Patagonia indices can be interpreted as changes in latitudinal variation and intensity of the SWW respectively. Dataset integration suggest poleward SWW between 2000 and 750 cal yrs BP and northward-weaker SWW during the Little Ice Age (750–200 cal yrs BP). These SWW variations are synchronous to Patagonian fire activity major shifts. We found an in phase fire regime (in terms of timing of biomass burning) between northern Patagonia Monte shrubland and Southern Patagonia steppe environments. Conversely, there is an antiphase fire regime between Northern and Southern Patagonia forest and forest-steppe ecotone environments. SWW variability may be associated to ENSO variability especially during the last millennia. For the last 200 cal yrs BP we can concluded that the SWW belt were more intense and poleward than the previous interval. Our composite pollen-based SWW indices show the potential of pollen dataset integration to improve the understanding of paleohydric variability especially for the last 2000 millennial in Patagonia.

Late Quaternary Vegetational Changes in a Marsh Forest in Southeastern Brazil with Comments on Prehistoric Human Occupation

Radiocarbon ◽  
2015 ◽  
Vol 57 (5) ◽  
pp. 737-753 ◽  
Author(s):  
Walter Mareschi Bissa ◽  
Mauro B de Toledo
Keyword(s):  
Sediment Core ◽  
Environmental Changes ◽  
Human Impacts ◽  
Late Quaternary ◽  
Southeastern Brazil ◽  
Pollen Record ◽  
Important Indicator ◽  
Climate Conditions ◽  
Ams Radiocarbon Dating ◽  
Se Brazil

This article presents a palynological study carried out on a sediment core from a peat deposit in Serra de Botucatu, in SÃo Paulo State, southeastern Brazilian Plateau. This region has been covered by grassland vegetation and forest patches throughout the recorded period. AMS radiocarbon dating plus palynological analysis of 27 samples from the sediment core allowed the recognition of several environmental changes that took place during the last 33,000 yr recorded in the core. The relationship between sedimentation rates and changes in the abundance of plants recognized through their pollen record, particularly a few important indicator species, provided the paleoenvironmental history for the Serra de Botucatu region, allowing the identification of changes in climate conditions and comparison with other regions in Brazil. One of the most remarkable features of this record is the cold and humid conditions during the Last Glacial Maximum, which diverges from previous interpretations for southeastern and southern Brazil but is in good agreement with paleoclimatic data from trace elements from cave stalagmites in SE Brazil. No indications of human impacts on the vegetation were found in this record.

The Intermontane Western Tradition

1962 ◽  
Vol 28 (2) ◽  
pp. 144-150 ◽  
Author(s):  
Richard D. Daugherty
Keyword(s):  
Conceptual Framework ◽  
Sierra Nevada ◽  
Great Basin ◽  
Rocky Mountains ◽  
Environmental Changes ◽  
Glacial Period ◽  
Western Tradition ◽  
The West ◽  
Northern Mexico ◽  
The North

AbstractThe hypothesis of an Intermontane Western tradition is advanced as a conceptual framework within which it is possible to achieve a greater understanding of the cultural histories of the Plateau, Great Basin, and Southwest culture areas, including broad and specific relationships and also the developing differences.Geographically, the Intermontane Western tradition extended throughout the intermontane region between the Cascade-Sierra Nevada ranges on the west, and the Rocky Mountains on the east, and from southern British Columbia on the north to northern Mexico on the south. Temporally, the Intermontane Western tradition existed throughout the post-glacial period.Within the major tradition, the Southwest Agricultural, Desert, and Northwest Riverine Areal traditions are seen developing, partly in response to environmental changes.

scholarly journals First Report of Rust Caused by Puccinia similis on Artemisia tridentata in Idaho and Oregon

Plant Disease ◽  
2010 ◽  
Vol 94 (3) ◽  
pp. 380-380
Author(s):  
R. K. Sampangi ◽  
M. C. Aime ◽  
S. K. Mohan
Keyword(s):  
Great Basin ◽  
Large Subunit ◽  
Artemisia Tridentata ◽  
Canopy Cover ◽  
Home Garden ◽  
Infected Leaf ◽  
Usda Forest Service ◽  
First Report ◽  
Big Sagebrush ◽  
Herbarium Data

Artemisia tridentata Nutt. (Asteraceae), commonly called sagebrush or big sagebrush, is a coarse, hardy, silvery-gray bush growing in arid sections of the Great Basin Desert of intermountain plateau covering portions of California, Idaho, Nevada, Oregon, Utah, and Wyoming in the western United States. Sagebrush is a key component of these ecosystems, providing canopy cover, nesting habitat, and a food source for numerous species of small animals and birds (4). During a plant disease survey in the Treasure Valley Region of southwestern Idaho and eastern Oregon, symptoms and signs of rust were observed on leaves of sagebrush in July 2007. Ten of fifteen plants (~70%) observed at the site were infected. Leaf samples of sagebrush with rust were also collected from a hedge in a home garden in Canyon County, ID in May 2006 and September 2007. Symptoms on both samples included cinnamon-brown, raised uredinia, primarily on the adaxial leaf surfaces. Initially, sori were scattered, increasing in density and becoming confluent. Urediniospores were thick walled, subglobose to obovoid, golden brown, echinulate, with three +/– equatorial germ pores, and measured 28 to 32 × 23 to 27 μm. Telia appeared late in the season (July to August) and were mostly scattered, becoming confluent and forming raised, ovoid, brown-to-dark red streaks on leaves and stems. Teliospores were brown to dark red, two-celled, averaging 45 × 26 μm, thick walled (average 0.75 to 1.5 μm), thickening at the apex, ellipsoid to broadly ellipsoid, with thin-walled, hyaline pedicels, 26 to 31 μm broad at attachment, tapering below, equal to or up to twice as long as the spore. On the basis of morphology, this pathogen was identified as Puccinia similis Ellis & Everh. (2), an autoecious rust previously reported from Arizona and Wyoming on A. tridentata and A. nova A. Nels. (3). To confirm the identification of the specimens from Idaho, an ~1,000 bp of DNA from the ribosomal 28S large subunit was amplified and sequenced with rust-specific primers (1) (GenBank No. GU168942). Since there are no sequences of P. similis available in GenBank for comparison, a sequence of the same gene was also obtained from a specimen of P. similis that had been collected on A. cana Pursh in Utah in 1995 by C. T. Rogerson and deposited in the U.S. National Fungus Collections (BPI 863644; GenBank No. GU168943). The sequences shared 100% identity and did not match any other species of rust in GenBank. To our knowledge, this is the first report of P. similis in Idaho and Oregon on sagebrush, and the first report, based on herbarium data, of this rust on A. cana in Utah. Voucher specimens from Idaho have been deposited in BPI (878064) and the Bernard Lowy Mycological Herbarium (LSUM). References: (1) M. C. Aime. Mycoscience 47:112, 2006. (2) G. B. Cummins. Rust Fungi on Legumes and Composites in North America. University of Arizona Press, Tucson, 1978. (3) D. F. Farr et al. Fungal Databases. Systematic Botany and Mycology Laboratory, Online publication. USDA-ARS, 8 July 2009. (4) B. L. Welch and C. Criddle, USDA Forest Service Res. Pap. RMRS-RP-40. 2003.

scholarly journals Influence of climate and environment on post-fire recovery of mountain big sagebrush

2014 ◽  
Vol 23 (1) ◽  
pp. 131 ◽  
Author(s):  
Zachary J. Nelson ◽  
Peter J. Weisberg ◽  
Stanley G. Kitchen
Keyword(s):  
Great Basin ◽  
Recovery Rate ◽  
Fire Regime ◽  
Seedling Survival ◽  
High Elevation ◽  
Deep Soil ◽  
Big Sagebrush ◽  
Survival Percentage ◽  
Water Recharge ◽  
Recovery Times

In arid and semi-arid landscapes around the world, wildfire plays a key role in maintaining species diversity. Dominant plant associations may depend upon particular fire regime characteristics for their persistence. Mountain shrub communities in high-elevation landscapes of the Intermountain West, USA, are strongly influenced by the post-fire recovery dynamics of the obligate-seeding shrub, mountain big sagebrush (Artemisia tridentata Nutt. ssp. vaseyana [Rydb.] Beetle). This species is a short-distance disperser with a short-lived seedbank, leading to highly variable post-fire recovery times (15–100 years). We investigated the relative importance of site productivity and seasonal climate in explaining the variance in recovery time for 36 fires, comprising a fire chrono-sequence (from 1971 to 2007) for the Great Basin and Colorado Plateau. A. t. vaseyana recovery was positively related to precipitation in the cool season immediately following fire, likely because deep soil-water recharge that persists throughout the growing season enhances first-year seedling survival. Percentage sand fraction positively correlated with recovery rate yet negatively correlated with live cover in unburnt stands. Our data support the hypothesis that post-fire recovery rate of A. t. vaseyana depends on the climatically controlled ephemerality of the regeneration niche, as is likely true for many arid-land shrub species.

scholarly journals Technical Note: Water flow routing on irregular meshes

2007 ◽  
Vol 11 (4) ◽  
pp. 1243-1247 ◽  
Author(s):  
D. Bänninger
Keyword(s):  
Water Flow ◽  
Cross Sections ◽  
Technical Note ◽  
Spatially Explicit ◽  
Hill Slope ◽  
Digital Elevation ◽  
Irregular Meshes ◽  
Elevation Model ◽  
Local Gradient ◽  
Flow Cross

Abstract. For spatially explicit hydrological modelling an algorithm was required that works as a cellular automata on irregular meshes. From literature it was found that the usual algorithms applied for this purpose do not route the water flow correctly between adjacent cells. In this study the hydraulic linking between mesh cells is done by calculating the flow cross section between the mesh cells. The flow cross sections are positioned in the centre of the mesh edges and are perpendicular to the local gradient of the digital elevation model. The presented algorithm is simple in its implementation and efficient in computation. It is shown that the proposed algorithm works correctly for different synthesised hill slope shapes.

Anthropogenic transformations in the glaciotectionical area in the Polish part of the Muskau Arch

2021 ◽  
Author(s):  
Ewa Warchala ◽  
Miłosz Becker ◽  
Jan Blachowski ◽  
Anna Buczyńska ◽  
Natalia Bugajska ◽  
...  
Keyword(s):  
Brown Coal ◽  
Cross Sections ◽  
Land Surface ◽  
Environmental Changes ◽  
Gravity Anomalies ◽  
Geological Structure ◽  
Geophysical Research ◽  
Natural Factor ◽  
Multi Stage ◽  
Natural Terrain

&lt;p&gt;The eastern part of the transboundary UNESCO Global Geopark Muskau Arch and the southern part of the Landscape park of the same name include four areas that are the subject of research in a project financed by the OPUS National Science Centre (No. 2019/33/B/ST10/02975).&lt;/p&gt;&lt;p&gt;The Muskau Arch is a unique moraine structure created as a result of the multi-stage influence of the Scandinavian ice sheet. Its most characteristic geomorphological feature are parallel sequences of land surface depressions, separated by local moraine hills.&lt;/p&gt;&lt;p&gt;The area in question covers the former German and Polish mine &amp;#8220;Babina&amp;#8221;, active between 1920 and 1972. Brown coal, ceramic clay and glass sands deposits were exploited with underground and opencast methods, resulting in a variety of anthropogenic transformations in the entire region.&lt;/p&gt;&lt;p&gt;The internal geological structure of the Muskau Arch, identified by drilling and mining works, indicates the presence of many zones, which differ in terms of the style of glacial-tectonic sediment deformation.&lt;/p&gt;&lt;p&gt;As part of the project, geophysical research (gravimetric and seismic) and geotechnical drilling were carried out providing new information on the character and scale of anthropogenic transformations of the glaciotectonic area, as well as the origins of anthropogenic and natural terrain deformations.&lt;/p&gt;&lt;p&gt;The developed gravimetric maps combine the geomorphological forms of the terrain and surface deformations with the geological structure and anthropogenic or natural changes. The qualitative interpretation is based on the analysis of the distribution, size and amplitude of gravity anomalies reflecting the bulk density of the sediments that make up the studied medium. Negative anomalies reflect the shortage of masses, which, as a natural factor, should be associated with the presence of weathering brown coal seams, their extent and dip. They are also generated by anthropogenic processes related to mining exploitation and translate into post-mining voids, zones of continuous consolidation and subsidence trough and post-mining heaps. Anomalies with positive amplitudes show the presence of tills, glacial sands and clays.&lt;/p&gt;&lt;p&gt;The results of measurements along seismic cross-sections confirmed the high glaciotectonic involvement within the Tertiary formations, showed the framework character of the top of the underlying (Cretaceous) deposits and allowed for the interpretation of lithostratigraphic boundaries.&lt;/p&gt;&lt;p&gt;Additionally, geotechnical drilling to a depth of 12 m was carried out in selected places using an impact system (Stitz) and a geotechnical light probe (Dynamic Penetration Light). The drillings were made in places that differed in the type of human interference: heaps, surface sinkholes, as well as in places intact by mining activities. The data from the drilling will be used for the geological and engineering analysis of morphological disturbances in the next tasks, including the construction of the model using the finite element method.&lt;/p&gt;&lt;p&gt;The natural and anthropogenic geomorphological forms of various origins that co-occur in the area of the UNESCO Global Geopark Muskau Arch constitute a part of the global geological and cultural heritage of a great importance in Poland and in Europe. Research which aim at discovering the genesis of these transformations can greatly contribute to our understanding of the modern-day environmental changes.&lt;/p&gt;

7.  An Examination of the Use of Salix Arctica for Dendrochronological Studies in the Arctic

2017 ◽  
Author(s):  
Anthony Bassutti
Keyword(s):  
Climate Change ◽  
Large Scale ◽  
Annual Growth ◽  
The Arctic ◽  
Growth Rings ◽  
Proxy Records ◽  
Land Disturbance ◽  
Annual Growth Rings ◽  
Salix Arctica ◽  
Large Scale Land

Large scale land disturbances are occurring in sensitive Arctic regions as a result of climate change. These disturbances which are caused by permafrost melting and can damage fragile tundra ecosystems and have important impacts on downstream water quality. Determining the timeline of these disturbances will aid in the understanding of the effect of climate change in the Arctic. This can be performed through the analysis of environmental proxy records such as those found in the annual growth rings of trees, which express environmental stresses, such as those experienced during a land disturbance. Dendrochronology of the most northern occurring woody plant, Salix arctica (arctic willow) has been explored only a few times in the past, and its potential for paleoenvironmental studies in the Arctic have been largely over‐looked. We examined the thickness of annual growth rings from S. arctica from two areas of land disturbance on southern Melville Island, Nunavut. Common growth trends were found in both dead (snag) and living samples from the sites. Preliminary data show that a substantial disturbance in the growth of the samples is evident approximately 40 years ago and was likely due to land disturbance. These initial findings demonstrate the successful use of S. arctica as a paleoenvironmental indicator and provide useful tools to determine the timing of past permafrost disturbances and climate change in the Arctic. We are continuing to investigate additional samples from other sites to determine if the method can be used as a novel tool for understanding permafrost landscape dynamics.

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