Cold Temperate Research Articles

The intermingling of benthic macroinvertebrate communities during a period of shifting range: The “East of Nantucket” Atlantic Surfclam Survey and the existence of transient multiple stable states

AbstractA survey of the region eastward of Nantucket provided an opportunity to examine the cold temperate–boreal boundary along the high‐energy Great South Channel. Here described are the benthic macroinvertebrate community types encountered, with a focus on the influence of climate change on the range boundaries of the benthic biomass dominants and the potential existence of transient multiple stable states. The survey identified three primary community types. The shallowest sites were occupied by a surfclam‐dominated community, comprising an abundance of large (≥150 mm) surfclams, and a few common attached epibiota primarily attached to exposed surfclam shell. Two communities exist at intermediate depths, one dominated by submarket and small market‐size surfclams (<150 mm) and the other, created by mussel mats and their attendant epibiota, crabs, sea urchins, and other mobile epifauna. Mussels are a foundational species, establishing a hard‐bottom terrain conducive to these other denizens in soft‐bottom habitat. Cobbles were nearly ubiquitous, rocks were routinely recovered, and boulders were encountered occasionally. Slow growing attached epibionts were exceedingly rare and mobile epifauna were not obviously associated with these large sedimentary particles; nor were the surfclam or mussel communities. The frequency of barnacle scars suggests sediment scour under the high‐flow regime characteristic of the surveyed region, which voids the habitat potential of these sedimentary particles. The abundance of surfclam shell indicates that surfclams have inhabited the shoaler depths for an extended time; limited shell at deeper sites supports the inference from the absence of large animals that these sites are relatively newly colonized and represent further evidence of an offshore shift in range brought on by increasing bottom water temperatures. The dichotomous nature of the two primary community types at mid‐depths suggests that these two communities represent multiple stable states brought on by the interaction of an invading cold temperate species with the receding boreal fauna resulting in a transient intermingling of species, which, however, structure the habitat into exclusionary stable states rather than overlapping in a co‐occurrence ecotone.

Ecological meta-analysis of bloom-forming planktonic Cyanobacteria in Argentina

The aim of the present research was to summarize the main reasons that explain the distribution of harmful blooms of cyanobacteria in Argentina. It is a large territory with climates ranging from humid tropical to cold temperate. We performed a meta-analysis of the published data and information in technical reports published from 1945 to 2015, and included additional data from personal non-published studies. A total of 122 water bodies affected by planktonic cyanobacterial blooms were recorded and geo-referenced. The analysis showed that blooms, defined as events exceeding 5000 cells/mL, occurred in different types of water bodies, including shallow lakes, rivers, streams, reservoirs, estuaries and storage facilities. Maximum bloom abundance and species and ecological strategies (dispersive, scum-forming, nitrogen fixer) responsible for each event were related to the geographic and climatologic characteristics and type and origin of water bodies. The Puna and the Andean Patagonia eco-regions were mostly free of blooms. The most impaired aquatic systems were shallow lakes and reservoirs (46.7 and 24.6%, respectively). Deep lakes had no reports of blooms and rivers were mainly affected at the regulated reaches, with intensities generally decreasing downstream the dams. Besides, 74.3% of the blooms reported in Argentina exceeded WHO Alert Level 2 for drinking and bathing waters (100,000 cells/mL). Thirty-nine species, identified by Komárek’s polyphasic approach to taxonomy, were responsible for the blooms. Microcystis aeruginosa, Dolichospermum spiroides, Dolichospermum circinale, Raphidiopsis mediterranea and Cylindrospermopsis raciborskii were frequently found participating in either mixed or single species blooms. The species distribution was associated with the eco-region and aquatic system typologies and affected by seasonality and climatological and geographic variables. The eco-strategies of cyanobacterial species showed stronger associations with the qualitative and quantitative indicators used in the meta-analysis, and appeared as useful tools for management measures.

Influence of building envelopes, climates, and occupancy patterns on residential HVAC demand

Heating, ventilation and air-conditioning (HVAC) demand accounts for 40% of household energy use. While the impacts of local climates, building characteristics, and occupancy patterns on HVAC demand are all well-known, the interplay between these factors has not been systematically studied. This paper provides a quantitative analysis of the complex interplay between these parameters on the annual and peak HVAC demand of residential buildings. Australia is used as a case study because the building construction practices are similar to many other countries, particularly in Europe and the USA, and the Australian climates span the majority of climates found in the world. The wall types considered are cement render, timber clad, brick veneer, reverse brick veneer, and cavity brick. The climates range from tropical in the north of the country, to cold temperate in the south of the country. The occupancy patterns are modeled using six common Occupancy Scenarios. The results show the highest energy reductions are observed in the climates with high diurnal temperature variation, such as Melbourne (51%) and Hobart (54%). The effect of thermal inertia is less in the climates with low diurnal temperature variation such as Darwin (19%). Occupancy scenarios that include unoccupied periods result in lower annual HVAC demand, yet they increase the peak cooling and heating demand. Increasing the indoor thermal mass by using brick veneer internal walls is shown to reduce the demand by approximately 10–15%.

Distribution and Driving Factors of Forest Swamp Conversions in a Cold Temperate Region.

Forest swamps are widely distributed in cold temperate regions, with important landscape and ecological functions. They are prone to conversion caused by complex factors. Forest swamp conversions involve forest swamping, meadow swamping, water body swamping, and conversion to farmland. An understanding of the landscape characteristics and primary environmental factors driving forest swamp conversions is imperative for exploring the mechanism of forest swamp conversions. We investigated the landscape characteristics of forest swamp conversions and quantified the relative importance of environmental factors driving these conversions for the period from 1990 to 2015 in the Great Xing’an Mountains of China. We found that forest swamping displayed high patch numbers (34,916) and density (8.51/100 ha), commonly occurring at the edge of large areas of forests. Meadow swamping was localized with low patch numbers (3613) and density (0.88/100 ha) due to lack of water recharge from ground water. Water body swamping had complex shapes (perimeter area ratio mean = 348.32) because of water table fluctuations and helophyte growth during this conversion process. Conversions to farmland presented fairly regular (perimeter area ratio mean = 289.91) and aggregated (aggregation index = 67.82) characteristics affected by agricultural irrigation and management. We found that climatic and geomorphic factors were relatively important compared to topographic factors for forest swamp conversions. Negative geomorphic conditions provided the waterlogging environment as a precondition of swamp formation. Sufficient precipitation was an important source of water recharge due to the existence of permafrost regions and long-term low temperature reduced the evaporation of swamps water and the decomposition rate of organisms. These wet and cold climatic conditions promoted forest swamp development in cold temperate regions. Humans exerted a relatively important role in forest swamping and conversions to farmland. Fire disturbance and logging accelerated the conversion from forest to swamp. This study provides scientific information necessary for the management and conservation of forest swamp resources in cold temperate regions.

Marine sublittoral benthos fails to track temperature in response to climate change in a biogeographical transition zone

Abstract Species ranges are shifting globally to track temperature changes in response to climate warming, with substantial variability among taxa. In the English Channel, a biogeographical transition zone between the cold temperate and warm temperate provinces of the North-East Atlantic, distribution shifts have been relatively well documented for plankton, fish and intertidal benthic organisms, but little information is available on sublittoral benthos. Following a description of the magnitude of the sea bottom temperature (SBT) rise, the changes in the distribution and occupancy of 65 benthic invertebrate species were analysed by comparing data collected throughout the English Channel at more than 200 stations sampled during a cool period in the 1960s–1970s and at present in 2012–2014. A non-uniform rise in SBT for the last three decades was observed at the regional scale, varying from 0.07 to 0.54°C per decade. This rise differs from that reported for sea surface temperature (SST) in stratified areas suggesting that SBT should be used rather than SST to analyse responses of subtidal organisms to climate change. Despite shifts in both minimum and maximum sea bottom isotherms (2.5 and 3.2 km.year−1, respectively), the distribution centroid shift of most species remained <1.0 km.year−1, regardless of the average temperatures they usually experience. Conversely, decreases were observed in the occurrence of most cold-water species and increases were found in the occurrence of most warm-water species. These results suggest that ongoing climate change could lead to a decrease in benthic biodiversity at range limits, especially where connection routes are lacking for new migrants.

Dynamic heat transfer model and applicability evaluation of aerogel glazing system in various climates of China

Aerogel is a super insulation material and it has absorptivity to solar radiation. Indoor heat gain through aerogel glazing system and its temperature distribution depend strongly on the climatic conditions and geographical position of a building. In this paper, a dynamic heat transfer model and an optical model for granular aerogel glazing system are developed and validated through an experiment. By employing the validated model, the applicability of aerogel glazing system in various climates has been evaluated. By comparing the total heat loss in heating season, it is found that aerogel glazing system has great energy saving potential in Severe Cold Region and Temperate Region. The comparative analysis of total heat gain in cooling season indicates that aerogel glazing system in Hot-Summer Warm-Winter Region performs slightly better than the commonest double glazing system, but inferior to low-e double glazing system. In Cold Region and Hot-Summer Cold-Winter Region, there both have heating and cooling seasons all year round. The sum of total heat loss and total heat gain is used to evaluate the annual applicability. The results show that aerogel glazing system is suitable to apply in Cold Region and in the south and north orientations of Hot-Summer Cold-Winter Region.

Towards the Development of Perennial Barley for Cold Temperate Climates—Evaluation of Wild Barley Relatives as Genetic Resources

Perennial cereal crops could limit the negative impacts of agriculture on the environment and climate change. In cold temperate climates, perennial plants must be adapted to seasonal changes and abiotic stresses, such as frost, to be able to regrow for several years. Wild crop relatives that are perennials and already adapted to cold temperate climates may provide genetic resources for breeding new perennial cereal grain crops. Barley (Hordeum vulgare) is one of the most important cereals in northern agricultural areas, and its related perennial species may be good candidates for the development of perennial cereals. We evaluated a diverse set of 17 wild perennial Hordeum species represented by 67 accessions in field conditions with a cold winter climate and long days during summer in Central Sweden (latitude 60° N). Six species (H. brevisubulatum, H. bulbosum, H. fuegianum, H. jubatum, H. lechleri and H. secalinum) showed regrowth and formation of spikes for four seasons. The most distant perennial relative of barley, H. stenostachys, showed weak regrowth. H. bulbosum, the closest perennial barley relative, had a large number of accessions with wide geographic origins that showed good regrowth. Together with its storage bulbs and its cross-compatibility with barley, this makes H. bulbosum an important genetic resource for the development of perennial Hordeum grains using either the domestication or the wide-hybridization strategy.

Alternative pine hybrids and species to Pinus patula and P. radiata in South Africa and Swaziland

Through the collaborative efforts of companies affiliated with the International Program for Tree Improvement and Conservation (Camcore), a number of pine hybrids have been produced over the last decade. Many of these have been planted in trials across southern Africa that broadly represent winter and summer rainfall areas, with the latter ranging from warm to cold temperate sites. The five-year survival and growth of the hybrids and other pines in 12 of these trials were compared with Pinus radiata in the winter rainfall, and P. patula in the summer rainfall, regions where these species have been planted extensively. Except for the highest altitude site, where freezing conditions are common, the survival of most hybrids and tropical pines was better than P. patula or P. radiata. This was, in part, attributed to their improved tolerance to the pitch canker fungus, Fusarium circinatum, which was present in the nursery at the time of planting. In the winter rainfall area, the P. elliottii × P. caribaea hybrid, P. maximinoi and, surprisingly, the P. patula hybrids performed well. In the summer rainfall regions, hybrids with tropical parents such as P. caribaea, P. oocarpa and P. tecunumanii were more productive in the subtropical/warm temperate zone and, with increasing elevation, those hybrids crossed with P. patula performed relatively better. The P. patula × P. tecunumanii hybrid, particularly when crossed with low-elevation P. tecunumanii, performed exceptionally across most sites.

Characterization of the complete mitochondrial genome of Stejneger’s beaked whale, Mesoplodon stejnegeri (Cetacea: Ziphiidae)

Stejneger’s beaked whale (Mesoplodon stejnegeri, True in Proc US Natl Mus 8:584–585, 1885) is one of the least known cold temperate and subarctic species of the beaked whales (Zhiphiidae) found in the North Pacific Ocean, and its complete mitogenome has yet to be investigated. Herein, we report the complete mitogenome of M. stejnegeri stranded in South Korea. Although its overall structure was similar to those from the other cetacean species, the obtained 16,349 bp mitogenome showed only 92.5% average nucleotide identity value with its closest relative, Blainville’s beaked whale, M. densirostris, and less with other species in the Zhiphiidae family. Multigene phylogeny using the whole mitogenome revealed that M. stejnegeri was well separated from other Mesoplodon species, and the overall tree topology was in accordance with recent phylogenetic analyses. These results provide information fundamental for the genetic conservation and further evolutionary studies of the beaked whales.

Dwarf shrub and grass vegetation resistant to long‐term experimental warming while microarthropod abundance declines on the Falkland Islands

AbstractDwarf shrubs are a dominant plant type across many regions of the Earth and have hence a large impact on carbon and nutrient cycling rates. Climate change impacts on dwarf shrubs have been extensively studied in the Northern Hemisphere, and there appears to be large variability in response between ecosystem types and regions. In the Southern Hemisphere, less data are available despite dwarf shrub vegetation being a dominant feature of southern South America and mountainous regions of the Southern Hemisphere. Here, we present the response of an Empetrum rubrum dwarf shrub and a Poa grass community to 12 years of experimental climate manipulation achieved using open top chambers on the Falkland Islands, a cold temperate island group in the South Atlantic. The dwarf shrub and grass vegetation did not change significantly in cover, biomass or species richness over the 12 years period in response to climate warming scenarios of up to 1°C reflecting annual warming levels predicted in this region for the coming decades. The soil microarthropod community, however, responded with declines in abundance (37%) under warming conditions in the grass community, but no such changes were observed in the dwarf shrub community. Overall, our data indicate that dwarf shrub communities are resistant to the levels of climate warming predicted over the coming decades in the southern South America region and will, therefore, remain a dominant driver of local ecosystem properties.

Beachrock morphology and genesis on a paraglacial beach

Beachrock is present in deep, stable sections of a mixed sand and gravel beach at Whitepark Bay (55o14′N) on the paraglacial coast of Northern Ireland. The beachrock was revealed following progressive and extreme beach erosion during two particularly stormy winters (2013/14 and 2014/15). It occurs as large (up to 1m diameter, 0.2m thick), rounded, disc-shaped concretions in which original beach bedding structures are preserved. Both sand and gravel beach facies are cemented. The cements are similar to those of tropical beachrocks and comprise an initial thin micrite rim, and subsequent grain rims of aragonitic needles. The cementation is attributed to saturation of beach groundwater with calcium carbonate sourced from adjacent Cretaceous chalk outcrop in cliffs behind the beach and dunes. The micrite rims suggest microbial activity in the initial cementation, possibly by scavenging from chalk and skeletal carbonate grains. Subsequent aragonite rims were formed through degassing of CO2 aided by tidal water level fluctuations. Despite similar cementation processes to low latitude beachrocks, only isolated concretions occur rather than extensive shore-parallel outcrops. Conditions necessary for cementation (and ultimately preservation) in this cold temperate and paraglacial setting include long-term beach stability, a carbonate source (in this case, adjacent chalk cliffs and stream sapping) and tidal water level fluctuations. Bacterial activity may initiate calcite precipitation. Following extreme storms and with progressive shoreline retreat prompted by rising sea levels, increased reporting of cold-water beachrocks is to be expected as formerly stable sections of beaches are exposed to wave action.

Projection of Climate Change Scenarios in Different Temperature Zones in the Eastern Monsoon Region, China

The Eastern Monsoon Region of China is sensitive to climate change because of its special location. In this study, the Automated Statistical Downscaling (ASD) tool was used to simulate and project future climate change scenarios in different temperate zones in the Eastern Monsoon Region of China. The performances of the single General Circulation Model (GCM) and the GCMs ensemble from Coupled Model Inter-comparison Project Phase 5 (CMIP5) were compared, and the capability of the ASD model was evaluated. The simple mathematical averaging ensemble of GCMs is superior to the single GCM and to the other two weighted ensembles. The ASD model was capable of presenting the temporal and spatial variation of four variables (precipitation, mean air temperature, maximum and minimum air temperature) during both the calibration and validation periods. The performance of the ASD model varied among the different temperate zones. In the simulated future scenarios, the air temperature in the four zones showed an upward trend. Except for the subtropical zone, there was a tendency for increased precipitation in both the warm temperate zone and the cold temperate and middle temperate zones. Of particular interest is that, in the subtropical zone, the precipitation will decline in the future, whereas the air temperature (especially the maximum air temperature) will increase, which may put more pressure on water resource situations in this area.

Comparison of Nitrogen Removal in Floating Treatment Wetlands Constructed with Phragmites australis and Acorus calamus in a Cold Temperate Zone

The selection of emergent plants is of primary importance during the construction of floating treatment wetlands (FTWs). Focusing on the comparison of the nitrogen removal, pot-culture experiments were carried out in floating treatment wetlands constructed with Phragmites australis and Acorus calamus in northeast China, a cold temperate zone. Nitrogen removal and transformation processes were investigated to explore the pathways and factors that influence the nitrogen removal. FTWs showed a high capacity for nitrogen removal. In water with TN concentrations of 9.63 and 4.58 mg L−1, the average TN removal efficiencies of the FTWs constructed with P. australis were 91.5 and 84.2%, respectively, and those of FTWs constructed with A. calamus were 84.2 and 82.8%, respectively. Plant uptake accounted for 36.4 to 77.1% of total N removal. The average TN removal rates of P. australis systems in the first 2 days were 4.20 and 1.77 mg L−1 day−1 for treatments with TN concentrations of 9.36 and 4.58 mg L−1, respectively, significantly higher than those of the A. calamus system, which were 1.75 and 1.04 mg L−1 day−1, respectively. Our results suggested that plant uptake was the main pathway for nitrogen removal in FTWs, and P. australis was a suitable emergent plant species for use in FTW construction in a cold temperate zone.

A Hybrid Method for Generation of Typical Meteorological Years for Different Climates of China

Since a representative dataset of the climatological features of a location is important for calculations relating to many fields, such as solar energy system, agriculture, meteorology and architecture, there is a need to investigate the methodology for generating a typical meteorological year (TMY). In this paper, a hybrid method with mixed treatment of selected results from the Danish method, the Festa-Ratto method, and the modified typical meteorological year method is proposed to determine typical meteorological years for 35 locations in six different climatic zones of China (Tropical Zone, Subtropical Zone, Warm Temperate Zone, Mid Temperate Zone, Cold Temperate Zone and Tibetan Plateau Zone). Measured weather data (air dry-bulb temperature, air relative humidity, wind speed, pressure, sunshine duration and global solar radiation), which cover the period of 1994–2015, are obtained and applied in the process of forming TMY. The TMY data and typical solar radiation data are investigated and analyzed in this study. It is found that the results of the hybrid method have better performance in terms of the long-term average measured data during the year than the other investigated methods. Moreover, the Gaussian process regression (GPR) model is recommended to forecast the monthly mean solar radiation using the last 22 years (1994–2015) of measured data.

Phylogeography and pigment type diversity of Synechococcus cyanobacteria in surface waters of the northwestern pacific ocean.

The widespread unicellular cyanobacteria Synechococcus are major contributors to global marine primary production. Here, we report their abundance, phylogenetic diversity (as assessed using the RNA polymerase gamma subunit gene rpoC1) and pigment diversity (as indirectly assessed using the laterally transferred cpeBA genes, encoding phycoerythrin-I) in surface waters of the northwestern Pacific Ocean, sampled over nine distinct cruises (2008-2015). Abundance of Synechococcus was low in the subarctic ocean and South China Sea, intermediate in the western subtropical Pacific Ocean, and the highest in the Japan and East China seas. Clades I and II were by far the most abundant Synechococcus lineages, the former dominating in temperate cold waters and the latter in (sub)tropical waters. Clades III and VI were also fairly abundant in warm waters, but with a narrower distribution than clade II. One type of chromatic acclimater (3dA) largely dominated the Synechococcus communities in the subarctic ocean, while another (3dB) and/or cells with a fixed high phycourobilin to phycoerythrobilin ratio (pigment type 3c) predominated at mid and low latitudes. Altogether, our results suggest that the variety of pigment content found in most Synechococcus clades considerably extends the niches that they can colonize and therefore the whole genus habitat.

Salinity and temperature tolerances of Neomysis americana (Crustacea: Mysida) sub adults: Perspectives on vulnerability, and distribution in South America

Mysid Neomysis americana links the benthic and pelagic food webs of numerous estuaries of the Western Atlantic. Aim was to understand the vulnerability of one of their recruitment stages i.e. sub adults to realistic ranges of salinity and temperature. Such may help to understand their present and predict future latitudinal distribution. Sub adults of N. americana were collected from Laguna de Rocha estuary, Uruguay and exposed to salinities 5, 10, 15, 20, 25, and 30 at each of four experimental temperatures: 10°C, 20°C, 25°C and 30°C, for 72h. Irrespective of temperature, survival was lowest in salinity 5. Survival was overall high in salinity 15 but in higher salinities such as 25, 30 mysids struggled to survive. Survival was particularly low in 10°C, highest in 20°C; and did not improve significantly in 25°C and 30°C. Results indicate that the recruits of N. americana can only withstand intermediate salinities and temperatures. Their vulnerability during seasonal anomalies, floods and droughts cannot be ruled out. Narrow range of temperature tolerance of the recruits may be a reason of absence of N. americana in cold temperate and warm tropical Atlantic coasts of South America. In the context of climatic warming, N. americana may extend its distribution along the southern coasts of Argentina but not towards northern Brazil.

Determination of the Optimal Tilt Angle of Solar Collectors for Different Climates of China

The tilt angle with the horizon (with respect to the ground) of the solar energy system affects the amount of solar radiation received. This paper suggests a simple and universal method to obtain the optimum tilt angles by estimating the monthly mean daily global solar radiation on tilted surfaces facing directly towards the equator, which is based on monthly average daily global solar radiation data produced from Typical Meteorological Year (TMY) data. The monthly, seasonal, and yearly optimum tilt angles for photovoltaic panels are calculated at six stations of different climatic types (Tropical Zone (TZ), Subtropical Zone (SZ), Warm Temperate Zone (WTZ), Mid Temperate Zone (MTZ), Cold Temperate Zone (CTZ) and Tibetan Plateau Zone (TPZ)). The results indicate that changing the monthly, seasonal, and yearly optimum tilt angles causes a significant yearly gain in the solar radiation for the region. In addition, general correlations are generated to estimate the optimum tilt angle of solar collectors at six typical climatic stations of China. The performances of the proposed models are compared using statistical error tests such as the mean absolute bias error (MABE), the root mean square error (RMSE) and the correlation coefficients (R).

Phosphorus and micronutrient dynamics during gymnosperm and angiosperm litters decomposition in temperate cold forest from Eastern Canada

Molybdenum (Mo) and phosphorus (P) limitation and co-limitation of asymbiotic dinitrogen (N2) fixation has been reported in many ecosystems, from tropical to boreal. However, the mechanisms leading to these limitations remain elusive. In cold temperate forests Mo and P limitation of asymbiotic N2 fixation has been observed in gymnosperm litter but not in angiosperm litter suggesting an important role of the vegetative cover. In gymnosperm litters, P and Mo limitation is characterized by a strongly seasonality; P limitation was observed early in the growing season while Mo limitation appears midway in the growing season. This discrepancy between gymnosperm and angiosperm litters and the strong seasonality suggest that the quality of the litter and decomposition dynamics play an important role in the emergence of Mo and P limitation in gymnosperm litters from cold temperate ecosystems. While the dynamics of macronutrients (i.e. C, N) during decomposition are well documented, our understanding of micronutrient (i.e. trace metals) dynamics during litter decomposition remains limited. Here, we measured nutrient concentrations (P, Mo and others) during litter decomposition in various angiosperm and gymnosperm litters and their combinations (2 and 4 species) using litter bags. Results showed that angiosperm litter achieves higher nutrient concentrations (P and metals) than gymnosperm litter. The concentration of most elements increased in both litter types over a 6-month period of decomposition (Al, Co, Cu, Fe, Mn, V, Ti, and Zn), with the exception of P and Mg which decreased over time. During decomposition, the concentration of Mo increased by ~300% in angiosperm litter but decreased by ~50% in gymnosperm litter. Together, these results suggest that the litter can concentrate metals from the surrounding environment (i.e. soil and atmospheric deposition) except for Mo in gymnosperm litter. Litter quality (nutrient concentration) and nutrient dynamics during litter decomposition likely play an important role in P and Mo limitation of asymbiotic N2 fixation.

Impacts of climate and humans on the vegetation in northwestern Turkey: palynological insights from Lake Iznik since the Last Glacial

Abstract. The Marmara region in northwestern Turkey provides a unique opportunity for studying the vegetation history in response to climate changes and anthropogenic impacts because of its location between different climate and vegetation zones and its long settlement history. Geochemical and mineralogical investigations of the largest lake in the region, Lake Iznik, already registered climate-related changes of the lake level and the lake mixing. However, a palynological investigation encompassing the Late Pleistocene to Middle Holocene was still missing. Here, we present the first pollen record of the last ca. 31 ka cal BP (calibrated kilo years before 1950) inferred from Lake Iznik sediments as an independent proxy for paleoecological reconstructions. Our study reveals that the vegetation in the Iznik area changed generally between (a) steppe during glacials and stadials indicating dry and cold climatic conditions, (b) forest-steppe during interstadials indicating milder and moister climatic conditions, and (c) oak-dominated mesic forest during interglacials indicating warm and moist climatic conditions. Moreover, a pronounced succession of pioneer trees, cold temperate, warm temperate, and Mediterranean trees appeared since the Lateglacial. Rapid climate changes, which are reflected by vegetation changes, can be correlated with Dansgaard-Oeschger (DO) events such as DO-4, DO-3, and DO-1, the Younger Dryas, and probably also the 8.2 event. Since the mid-Holocene, the vegetation was influenced by anthropogenic activities. During early settlement phases, the distinction between climate-induced and human-induced changes of the vegetation is challenging. Still, evidence for human activities consolidates since the Early Bronze Age (ca. 4.8 ka cal BP): cultivated trees, crops, and secondary human indicator taxa appeared, and forests were cleared. Subsequent fluctuations between extensive agricultural uses and regenerations of the natural vegetation become apparent.

Production, exportation and preservation of silicoflagellates in Alfonso Basin, Gulf of California

Limited areas of sea floor have the physiochemical conditions that allow for the formation and preservation of high resolution (yearly or close to yearly) laminated sediments that can function as a historic proxy for past oceanographic and climate conditions. We evaluated and established the fidelity of the sedimentary record in recording these signals by analyzing silicoflagellates production, changes in species composition, skeletal settling and their subsequent burial in bottom sediments at Alfonso Basin. The data series from December 2005 to February 2008 showed similar tendencies in both the vertical flux and overlying euphotic zone (Zeu) production of silicoflagellates. Both series were numerically dominated by Octactis pulchra with maxima values being recorded for the mixed water column period. Observed differences occurred during the studied years in both magnitude and in flux composition. The presence of a mixed assemblage with (warm–temperate–cold) species such as Dictyocha fibula var. robusta, Dictyocha epiodon and Distephanus speculum could be explained by a synchronization of trends between a predominantly positive Pacific Decadal Oscillation and a positive North Pacific Gyre Oscillation climate phases that were the background conditions underlying the early 2006 through 2007 El Niño event. A Morisita's similarity index value of 97.5% between winter trap and Zeu samples combined with an annualized settling factor of 0.45, suggests that Alfonso Basin is a favorable settling environment for silicoflagellates. However, core-top sediments showed an attenuation of record fidelity (burial factor=0.25) resulting in a modified record for the production and settling of skeletons. O. pulchra that were not preserved in sediments as the dominant species and with this removal, the signal was also lost of the highest silicoflagellate production season (Mixing-cyclonic eddy periods) from the sedimentary record of the Alfonso Basin.