Impacts of climate and river flooding on the hydro-ecology of a floodplain basin, Peace-Athabasca Delta, Canada since A.D. 1700

2005 ◽  
Vol 64 (2) ◽  
pp. 147-162 ◽  
Author(s):  
Brent B. Wolfe ◽  
Tammy L. Karst-Riddoch ◽  
Sheila R. Vardy ◽  
Matthew D. Falcone ◽  
Roland I. Hall ◽  
...  
Keyword(s):  
Lake Sediment ◽  
Climatic Variability ◽  
Ecological Status ◽  
Ring Width ◽  
Climatic Conditions ◽  
Ice Age ◽  
Water Flooding ◽  
Hydroelectric Power ◽  
Peace River ◽  
Isotopic Analyses

AbstractMulti-proxy paleolimnological analyses on lake sediment cores from "Spruce Island Lake" (58° 50.82′ N, 111° 28.84′ W), a perched basin in the northern Peace sector of the Peace-Athabasca Delta (PAD), Canada, give insights into the relative roles of flow regulation of the Peace River and climatic variability on the basin hydro-ecology. Results indicate substantial variability in basin hydro-ecology over the past 300 years ranging from seasonal to periodic desiccation in the 1700s to markedly wetter conditions during the early 1800s to early 1900s. The reconstruction is consistent with (1) dry climatic conditions that defined the peak of the Little Ice Age and subsequent amelioration evident in conventional ring-width and isotopic analyses of tree-ring records located hydrologically and climatically upstream of the PAD, and (2) Peace River flood history inferred from sub-annual magnetic susceptibility measurements from another lake sediment record in the Peace sector of the PAD. Although regulation of the Peace River for hydroelectric power generation since 1968 has long been considered a major stressor of the PAD ecosystem leading to reduced frequency of ice-jam and open-water flooding and an extended period of drying, our results show that current hydro-ecological status is not unprecedented as both wetter and drier conditions have persisted for decades in the recent past under natural climatic variability. Furthermore, paleolimnological evidence from Spruce Island Lake indicates that recently observed dryness is part of a longer trend which began some 20�"40 years prior to Peace River regulation.

scholarly journals Record of the Climatic Variability and the Sedimentary Dynamics during the Last Two Millennia at Sebkha Dkhila, Eastern Tunisia

ISRN Geology ◽  
2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Elhoucine Essefi ◽  
Jamel Touir ◽  
Mohamed Ali Tagorti ◽  
Chokri Yaich
Keyword(s):  
Little Ice Age ◽  
Climatic Variability ◽  
Low Frequency ◽  
Climatic Conditions ◽  
Ice Age ◽  
Global Changes ◽  
Medieval Climatic Anomaly ◽  
Grey Scale ◽  
Sedimentary Dynamics ◽  
The Last Two Millennia

This paper aimed to study the record of the climatic variability during the last two millennia within the sebkha of Dkhila. Six climatic stages were recognized along the 104 cm core: the Warming Present (WP), the Late Little Ice Age (Late LIA), the Early Little Ice Age (ELIA), the Medieval Climatic Anomaly (MCA), the Dark Age (DA), and the Roman Warm Period (RWP). The WP stretches along the uppermost 1 cm with a high grey scale as sign of a dry climate. The Late LIA is located between 1 cm and 6 cm. The ELIA is located between 6 cm and 40 cm. The MCA spanning from 40 cm to 72 cm is marked by a sharp increase of the GS revealing a wet period. The DA appears along the part between 72 cm and 84 cm; a shift from light to dark sediments is recorded. The RWP appears between 84 cm and 104 cm. Based on the grain size distribution, two low frequency cycles were identified indicating radical global changes of climatic conditions, the differential tectonics, and the groundwater fluctuations. On the other hand, high frequency cycles indicate local modifications of the climatic conditions.

scholarly journals The Toledo Mountains: A Resilient Landscape and a Landscape for Resilience? Hazards and Strategies in a Mid-Elevation Mountain Region in Central Spain

Quaternary ◽  
2019 ◽  
Vol 2 (4) ◽  
pp. 35 ◽  
Author(s):  
Reyes Luelmo-Lautenschlaeger ◽  
Sebastián Pérez-Díaz ◽  
Olivier Blarquez ◽  
César Morales-Molino ◽  
José Antonio López-Sáez
Keyword(s):  
Climatic Variability ◽  
Central Area ◽  
Climatic Conditions ◽  
Mediterranean Vegetation ◽  
Ice Age ◽  
Mountain Range ◽  
Taxus Baccata ◽  
Central Spain ◽  
Ilex Aquifolium ◽  
Original Distribution

The Toledo Mountains are a mid-elevation mountain range that separates the Tagus and Guadiana basins in the central area of the Iberian Peninsula. The location of these mountains allows the development of typical Mediterranean vegetation with some Atlantic influence. Consequently, typical broadleaved evergreen Mediterranean vegetation currently dominates the regional landscape, with the remarkable presence of more mesophilous species in sheltered and more humid microsites such as gorges (e.g., Prunus lusitanica, Taxus baccata, Ilex aquifolium) and mires/bogs (e.g., Betula pendula susbp. fontqueri, Erica tetralix, Myrica gale). Palaeoecological studies in these mountains are essential to understand the long-term ecology and original distribution of these valuable communities and are key to assess their resilience. Understanding the hazards and opportunities faced in the past by the plant communities of the Toledo Mountains is necessary to enhance the management and protection of those species currently threatened. This study focuses on El Perro mire, a peatland on the southern Toledo Mountains (central Spain) where climatic variability has played a major role in landscape dynamics at multi-decadal to millennial timescales. Climatic events such as the 4.2 ka cal. Before Present (BP) or the Little Ice Age triggered relevant landscape changes such as the spread and latter decline of birch and hazel forests. Human communities also seemed to be affected by these events, as their resilience was apparently jeopardized by the new climatic conditions and they were forced to find new strategies to cope with the new scenarios.

Variability to sedimentary dynamics and climatic conditions during the last two millennia at sebkha Souassi in eastern Tunisia

2013 ◽  
Vol 20 (1) ◽  
Author(s):  
Elhoucine Essefi ◽  
Hayet Ben Jmaa ◽  
Jamel Touir ◽  
Mohamed Ali Tagortig ◽  
Chokri Yaicha
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Little Ice Age ◽  
Climatic Variability ◽  
Climatic Conditions ◽  
Ice Age ◽  
Global Changes ◽  
Sedimentary Dynamics ◽  
The Last Two Millennia

AbstractThis paper covers work intended to study the interplay of sedimentary dynamics and climatic variability over the last two millennia within Tunisia’s sebkha Souassi. Based on the Visual Core Description, and magnetic susceptibility, we date the core from sebkha Souassi to the last two millennia. Genetic grain-size distribution then provided a basis for the identification of six climatic stages, i.e. the Warming Present (WP), the Late Little Ice Age (Late LIA), the Early Little Ice Age (ELIA), the Medieval Climatic Anomaly (MCA), the Dark Ages (DA), and the Roman Warm Period (RWP). The WP stretches across the uppermost 3 cm, with a high grey scale indicating a dry climate. The Late LIA is located between 3 and 7 cm, and the ELIA between 7 and 28 cm. Intermediate values for GS indicate that this stage may be classified as moderate. The MCA spanning from 28 to 40 cm is marked by a sharp decrease in GS indicative of a wet period. The DA appear along the part between 40 and 79 cm, a shift from light to dark sediments being recorded. The RWP in turn appears between 79 and 114 cm. Based on the grain-size distribution, two low-frequency cycles were identified, indicating radical global changes in climatic conditions, differential tectonics and groundwater fluctuations. High-frequency cycles in turn attest to local modifications of climatic conditions.

scholarly journals Sea-ice induced growth decline in Arctic shrubs

2017 ◽  
Vol 13 (8) ◽  
pp. 20170122 ◽  
Author(s):  
Mads Forchhammer
Keyword(s):  
Sea Ice ◽  
Ring Width ◽  
Plant Productivity ◽  
Climatic Conditions ◽  
Arctic Sea Ice ◽  
Annual Growth ◽  
The Arctic ◽  
Growth Time ◽  
Sea Ice Extent ◽  
Negative Effect

Measures of increased tundra plant productivity have been associated with the accelerating retreat of the Arctic sea-ice. Emerging studies document opposite effects, advocating for a more complex relationship between the shrinking sea-ice and terrestrial plant productivity. I introduce an autoregressive plant growth model integrating effects of biological and climatic conditions for analysing individual ring-width growth time series. Using 128 specimens of Salix arctica , S. glauca and Betula nana sampled across Greenland to Svalbard, an overall negative effect of the retreating June sea-ice extent was found on the annual growth. The negative effect of the retreating June sea-ice was observed for younger individuals with large annual growth allocations and with little or no trade-off between previous and current year's growth.

Holocene eolian sand deposition linked to climatic variability, Northern Great Plains, Canada

The Holocene ◽  
2016 ◽  
Vol 27 (4) ◽  
pp. 579-593 ◽  
Author(s):  
Stephen A Wolfe ◽  
Olav B Lian ◽  
Christopher H Hugenholtz ◽  
Justine R Riches
Keyword(s):  
Great Plains ◽  
Climatic Variability ◽  
Sediment Cores ◽  
Soil Formation ◽  
Temporal Variations ◽  
Ice Age ◽  
Northern Great Plains ◽  
Eolian Sand ◽  
Sand Accumulation ◽  
Sand Deposition

The Bigstick and Seward Sand Hills are possibly two of the oldest dune fields within the late Wisconsin glaciated regions of the Northern Great Plains. As with most Northern Great Plains dune fields, source sediments are former proglacial outwash sands. Thus, Holocene dune construction is primarily related to spatial–temporal variations in surface cover and transport capacity, rather than renewed sediment input. However, eolian landscape reconstructions on the Northern Great Plains have been temporally constrained to recent periods of activity, as older episodes of deposition are typically reworked by younger events. In this study, sediment cores from shallow lacustrine basins and interdune areas provide an improved record of Holocene eolian sand deposition. Eolian sand accumulation in the interdunes and basins occurred between 150 and 270 years ago, 1.9 and 3.0 ka, 5.4 and 8.6 ka, and prior to ca. 10.8 ka. These episodes of sand accumulation were bracketed by lacustrine deposition and soil formation, which represented wetter conditions. Other than mid-Holocene dune activity, which may be related to peak warmth and aridity, most periods of eolian sand accumulation coincided with cooler but drier climatic events such as the Younger Dryas, late-Holocene cooling prior to the Medieval Climatic Anomaly, and the ‘Little Ice Age’. These depositional episodes are also spatially represented by other dune fields in the region, providing a broad-scale view of the connections between past climatic events and eolian landscape evolution on the Northern Great Plains.

scholarly journals Climatic variability and human impact during the last 2000 years in western Mesoamerica: evidence of late Classic (AD 600–900) and Little Ice Age drought events

2015 ◽  
Vol 11 (9) ◽  
pp. 1239-1248 ◽  
Author(s):  
A. Rodríguez-Ramírez ◽  
M. Caballero ◽  
P. Roy ◽  
B. Ortega ◽  
G. Vázquez-Castro ◽  
...  
Keyword(s):  
Human Impact ◽  
Little Ice Age ◽  
Climatic Variability ◽  
Seasonal Migration ◽  
Ice Age ◽  
Cultural Tradition ◽  
Late Classic ◽  
High Pressure Cell ◽  
Western Mexico ◽  
The North

Abstract. We present results of analysis of biological (diatoms and ostracodes) and non-biological (Ti, Ca / Ti, total inorganic carbon, magnetic susceptibility) variables from an 8.8 m long, high-resolution (~ 20 yr sample−1) laminated sediment sequence from Lake Santa María del Oro (SMO), western Mexico. This lake lies at a sensitive location between the dry climates of northern Mexico, under the influence of the North Pacific subtropical high-pressure cell and the moister climates of central Mexico, under the influence of the seasonal migration of the intertropical convergence zone and the North American monsoon (NAM). The sequence covers the last 2000 years and provides evidence of two periods of human impact in the catchment, shown by increases in the diatom Achnanthidium minutissimum. The first from AD 100 to 400 (Early Classic) is related to the shaft and chamber tombs cultural tradition in western Mexico, and the second is related to Post-Classic occupation from AD 1100 to 1300. Both periods correspond to relatively wet conditions. Three dry intervals are identified from increased carbonate and the presence of ostracodes and aerophilous Eolimna minima. The first, from AD 500 to 1000 (most intense during the late Classic, from AD 600 to 800), correlates with the end of the shaft and chamber tradition in western Mexico after ca. AD 600. This late Classic dry period is the most important climatic signal in the Mesoamerican region during the last 2000 years, and has been recorded at several sites from Yucatan to the Pacific coast. In the Yucatan area, this dry interval has been related with the demise of the Maya culture at the end of the Classic (AD 850 to 950). The last two dry events (AD 1400 to 1550 and 1690 to 1770) correspond with the onset of, and the late, Little Ice Age, and follow largely the Spörer and Maunder minima in solar radiation. The first of these intervals (AD 1400 to 1550) shows the most intense signal over western Mexico; however this pattern is different at other sites. Dry/wet intervals in the SMO record are related with lower/higher intensity of the NAM over this region, respectively.

A new multi-proxy record of environmental change over the last 1000 years on Chiloé Island: Lake Pastahué, south-central Chile (42°S)

The Holocene ◽  
2018 ◽  
Vol 29 (3) ◽  
pp. 421-431
Author(s):  
J Max Troncoso Castro ◽  
Carolina Vergara ◽  
Denisse Alvarez ◽  
Gustavo Díaz ◽  
Pablo Fierro ◽  
...  
Keyword(s):  
Anthropogenic Activities ◽  
Biological Indicator ◽  
Climatic Conditions ◽  
Ice Age ◽  
Forest Composition ◽  
Central Chile ◽  
Lake Ecosystems ◽  
South Central ◽  
Recent Part ◽  
Patagonian Forest

Knowledge of past environmental and climatic conditions of lake ecosystems on Chiloé Island on a millennial scale is limited. Hence, this study fills a gap in our understanding of this part of southern Chile. The aim of this study was to reconstruct the environmental and climatic history of the last 1000 years of Lake Pastahué through a multi-proxy sediment core analysis. The 1-m-long core was subsampled every centimeter for the organic matter, magnetic susceptibility, grain-size distribution, and biological indicator (pollen, chironomids) analyses. The age model was constructed from 210Pb, 137Cs, and 14C activity. Pollen results revealed a North Patagonian forest composition represented by Nothofagus, Weinmannia, Drimys, Tepualia, Myrtaceae, Poaceae, and Pteridophyta. The abundance of Rumex and Pinus in the most recent part of the pollen assemblage reflects a clear anthropogenic impact. The sedimentological parameters and chironomid assemblage show similar variations, which highlight changes in the trophic state of the lake. The changes observed in all proxies suggest the influence of climate events such as the ‘Medieval Climate Anomaly’ (MCA) and ‘Little Ice Age’ (LIA). The variations observed since the beginning of the 20th century could be the result of the combined effect of anthropogenic activities and the increase in temperature recorded in south-central Chile and Patagonia.

scholarly journals BIOLOGICAL METHOD OF STRUGGLE AGAINST THE BASIC WRECKERS OF THE SWEET CORN IN R. OF MOLDOVA

1970 ◽  
Vol 62 ◽  
Author(s):  
Asea Timus ◽  
N. Croitoru
Keyword(s):  
Sweet Corn ◽  
Ecological Status ◽  
Climatic Conditions ◽  
Biological Method ◽  
Trichogramma Evanescens ◽  
Biological Methods ◽  
Year 2000 ◽  
Different Cultures ◽  
The Given ◽  
Harmful Species

Every year, the demand of ecological products in the world is increasing more and more. Republic of Moldova also aspires to expand the areas of agricultural crops to get production with the "ecological" status. The sweet corn, is one of these cultures and every year the areas increase. However, because of the considerable develop of harmful insects on cultural fields, the damage reaches up to 15-20 % and more it is necessary to take measures of struggle. One of these, is a biological method and in this case it has appeared effective. For the period of sweet corn cultivation, excepting for the technology observance of cultivation of the given culture, there have been used biological methods of struggle against harmful insects. Depending on climatic conditions of each zone of the country where it is grown up this culture, different species of harmful insects develop. In R. Moldova, begining with year 2000, have been registered the following harmful species of insects on sweet corn: Aphis spp. (Aphididae); Agrotis spp. (Elateridae); Blaps halophila Fisch. (Tenebrionidae); Phylotreta spp. (Chrysomelidae); Helicoverpa armigera Hubner (Noctuidae) Ostrinia nubilalis Hb. (Pyraustidae). The constant useful fauna which develops due to these harmful species is: Nabis spp. (Miridae); Chrysopa spp., (Chrysopidae); Coccinella spp. (Coccinelidae) and others. That is why, annually are let out individuals from species Trichogramma evanescens W., to reduce the number of harmful species H. armigera Hubner. This species annually damages on different cultures, including on sweet corn. The results on released trichogrammas in 2005, for struggle against harmful species H. armigera Hubner, are presented in this work.

scholarly journals Different Wood Anatomical and Growth Responses in European Beech (Fagus sylvatica L.) at Three Forest Sites in Slovenia

2021 ◽  
Vol 12 ◽  
Author(s):  
Domen Arnič ◽  
Jožica Gričar ◽  
Jernej Jevšenak ◽  
Gregor Božič ◽  
Georg von Arx ◽  
...  
Keyword(s):  
Tree Ring ◽  
Climatic Factors ◽  
Ring Width ◽  
European Beech ◽  
Growing Season ◽  
Climatic Conditions ◽  
Maximum Temperature ◽  
Tree Ring Width ◽  
Vessel Area ◽  
Temperature And Precipitation

European beech (Fagus sylvatica L.) adapts to local growing conditions to enhance its performance. In response to variations in climatic conditions, beech trees adjust leaf phenology, cambial phenology, and wood formation patterns, which result in different tree-ring widths (TRWs) and wood anatomy. Chronologies of tree ring width and vessel features [i.e., mean vessel area (MVA), vessel density (VD), and relative conductive area (RCTA)] were produced for the 1960–2016 period for three sites that differ in climatic regimes and spring leaf phenology (two early- and one late-flushing populations). These data were used to investigate long-term relationships between climatic conditions and anatomical features of four quarters of tree-rings at annual and intra-annual scales. In addition, we investigated how TRW and vessel features adjust in response to extreme weather events (i.e., summer drought). We found significant differences in TRW, VD, and RCTA among the selected sites. Precipitation and maximum temperature before and during the growing season were the most important climatic factors affecting TRW and vessel characteristics. We confirmed differences in climate-growth relationships between the selected sites, late flushing beech population at Idrija showing the least pronounced response to climate. MVA was the only vessel trait that showed no relationship with TRW or other vessel features. The relationship between MVA and climatic factors evaluated at intra-annual scale indicated that vessel area in the first quarter of tree-ring were mainly influenced by climatic conditions in the previous growing season, while vessel area in the second to fourth quarters of tree ring width was mainly influenced by maximum temperature and precipitation in the current growing season. When comparing wet and dry years, beech from all sites showed a similar response, with reduced TRW and changes in intra-annual variation in vessel area. Our findings suggest that changes in temperature and precipitation regimes as predicted by most climate change scenarios will affect tree-ring increments and wood structure in beech, yet the response between sites or populations may differ.

scholarly journals A 406-year non-growing-season precipitation reconstruction in the southeastern Tibetan Plateau

2021 ◽  
Vol 17 (6) ◽  
pp. 2381-2392
Author(s):  
Maierdang Keyimu ◽  
Zongshan Li ◽  
Bojie Fu ◽  
Guohua Liu ◽  
Fanjiang Zeng ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Tree Ring ◽  
Tree Growth ◽  
Ring Width ◽  
Growing Season ◽  
Climatic Conditions ◽  
Forest Growth ◽  
Drought Severity ◽  
Precipitation Reconstruction ◽  
Southeastern Tibetan Plateau

Abstract. Trees record climatic conditions during their growth, and tree rings serve as proxy to reveal the features of the historical climate of a region. In this study, we collected tree-ring cores of hemlock forest (Tsuga forrestii) from the northwestern Yunnan area of the southeastern Tibetan Plateau (SETP) and created a residual tree-ring width (TRW) chronology. An analysis of the relationship between tree growth and climate revealed that precipitation during the non-growing season (NGS) (from November of the previous year to February of the current year) was the most important constraining factor on the radial tree growth of hemlock forests in this region. In addition, the influence of NGS precipitation on radial tree growth was relatively uniform over time (1956–2005). Accordingly, we reconstructed the NGS precipitation over the period spanning from 1600–2005. The reconstruction accounted for 28.5 % of the actual variance during the common period of 1956–2005. Based on the reconstruction, NGS was extremely dry during the years 1656, 1694, 1703, 1736, 1897, 1907, 1943, 1982 and 1999. In contrast, the NGS was extremely wet during the years 1627, 1638, 1654, 1832, 1834–1835 and 1992. Similar variations of the NGS precipitation reconstruction series and Palmer Drought Severity Index (PDSI) reconstructions of early growing season from surrounding regions indicated the reliability of the present reconstruction. A comparison of the reconstruction with Climate Research Unit (CRU) gridded data revealed that our reconstruction was representative of the NGS precipitation variability of a large region in the SETP. Our study provides the first historical NGS precipitation reconstruction in the SETP which enriches the understanding of the long-term climate variability of this region. The NGS precipitation showed slightly increasing trend during the last decade which might accelerate regional hemlock forest growth.

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