Low-elevation Plains Research Articles

Regional variation in the distribution of patterned fens in the montane-boreal regions of Alberta, Canada

Peatlands represent an important part of the landscape of boreal western Canada, occupying some 365,157 km2. Sixty-three percent of these are minerogenous fens. Scattered among these fens are landscape features that have unique and distinctive patterns—pools and carpets (flarks) separated by raised linear ‘strings’. These patterned fens harbor rare and uncommon species and serve as habitats for endangered wildlife (e.g., woodland caribou, whooping cranes). In this study, utilizing Google Earth Pro (1) we documented 1083 ribbed fens and 250 reticulate fens in the province of Alberta, Canada; (2) determined the regional variation in patterned fen occurrences; (3) described the various morphological forms of patterned fens; and (4) recognized these as six distinctive peatland site-types. Patterned fens are not randomly arranged on the landscape. Ribbed fens are concentrated on regional high elevational uplands and montane benchlands with morainal deposits, while reticulate fens are more numerous on low elevation plains with glacial-fluvial and glacial-lacustrine deposits. Patterned fens vary along minerotrophic vegetation and chemical gradients and have a complex set of morphological types. To our knowledge, this is the first study that provides base line information on the abundance and distribution of patterned fens in Alberta and associates morphological patterned fen types with environmental or geological characteristics. The digital files and maps provide a permanent record against which future change can be compared.

Temporal and spatial evolution of ecosystem service value in Ili Valley and its driving factors

Ili Valley is an important ecological barrier in western China and an important economic zone of the Belt and Road Initiative. Exploring the driving factors of ecosystem service value (ESV) based on land use change is of great significance for optimizing regional ecological environment and coordinating human-land relationship. Based on three periods of land use data from 2000 to 2020 in Yili Valley, we used ArcGIS 10.8 and Origin to analyze the characteristics of land use change, temporal and spatial variations of ESV, and the synergy and trade-offs of ecosystem services, and explored the driving factors affecting the spatial differentiation of ESV and the interaction among factors by using Geo-Detector. The results showed that land use change in the study area was obvious from 2000 to 2020, with the area of grassland and water area being greatly reduced and the largest increase for the area of construction land. The ESV of grassland and water area and the service function of water resource supply decreased significantly. ESV high value areas were transformed to low value areas. Synergy was the dominant relationship among ecosystem services in the study area, which showed an increasing trend. Elevation was the main driving factor of ESV spatial differentiation in Yili Valley, and the low elevation plain area suitable for human activities on both sides of the basin was the low ESV value area. The interaction between all factors was manifested as enhanced relationship, while the explanatory power of natural factors was higher than that of social and economic factors.

Exploring the emergence and changing dynamics of a new integrated rice-crawfish farming system in China

Crop-aquaculture systems are widely adopted around the world as they can provide high protein and energy outputs per unit of land and raise farm incomes, particularly for smallholder farmers. Recently, a new crop-aquaculture system, which combines rice production with crawfish breeding (integrated rice-crawfish farming), has emerged and rapidly expanded in China. However, the spatial extent and temporal dynamics of this integrated farming system largely remain unclear, which prohibits rigorous impact assessments to support its sustainable development. Here we use time series of Landsat satellite data, for the first time, to explore the emergence and the changing dynamics of this rice-crawfish farming system for the period of 2013–2021 in five provinces (805 600 km2) of China, where 90% of the global crawfish are produced. Our analysis reveals that the total area of rice-crawfish farming in these five provinces increased steadily from 0.11 Mha in 2013 to 0.70 Mha in 2019, then sharply contracted by a third in 2020 and rebounded in 2021. Spatially, rice-crawfish system is located primarily in low-elevation plain areas with abundant water resources, where paddy rice cultivation has traditionally dominated agriculture. More concentrated rice-crawfish distribution is observed in Jianghan Plain, and regions around Dongting Lake and Poyang Lake. The spatial distribution of rice-crawfish cultivation experienced considerable expansion towards the east and north from 2013 to 2021, with the largest expansion found in Jiangsu and Anhui after 2018. At the county level, over 6% of counties experienced notable area increases of more than 60 km2 from 2017 and 2019, but 20% of counties have decreased from 2019 to 2021. Among the converted land use types, irrigated cropland is the largest contributor to rice-crawfish expansion with a contribution of 56%, followed by water bodies (25%) and rainfed cropland (13%). The spatial and temporal information provided in this study helps to understand the evolution of rice-crawfish cultivation in China and facilitates more efficient management of land resources under the rapid development of this farming system.

Research on land cover type classification method based on improved MaskFormer for remote sensing images.

High-resolution remote sensing images have the characteristics of wide imaging coverage, rich spectral information and unobstructed by terrain and features. All of them provide convenient conditions for people to study land cover types. However, most existing remote sensing image land cover datasets are only labeled with some remote sensing images of low elevation plain areas, which is highly different from the topography and landscape of highland mountainous areas. In this study, we construct a Qilian County grassland ecological element dataset to provide data support for highland ecological protection. To highlight the characteristics of vegetation, our dataset only includes the RGB spectrum fused with the near-infrared spectrum. We then propose a segmentation network, namely, the Shunted-MaskFormer network, by using a mask-based classification method, a multi-scale, high-efficiency feature extraction module and a data-dependent upsampling method. The extraction of grassland land types from 2 m resolution remote sensing images in Qilian County was completed, and the generalization ability of the model on a small Gaofen Image Dataset (GID) verified. Results: (1) The MIoU of the optimised network model in the Qilian grassland dataset reached 80.75%, which is 2.37% higher compared to the suboptimal results; (2) the optimized network model achieves better segmentation results even for small sample classes in data sets with unbalanced sample distribution; (3) the highest MIOU of 72.3% is achieved in the GID dataset of open remote sensing images containing five categories; (4) the size of the optimized model is only one-third of the sub-optimal model.

A westerly wind dominated Puna Plateau during deposition of upper Pleistocene loessic sediments in the subtropical Andes, South America

The Tafí del Valle depression (~27° S) in the eastern Andes of Argentina provides a record of late Pleistocene dust deposition in the subtropics of South America. We present large-n U-Pb geochronology data for detrital zircons from upper Pleistocene loess-paleosol deposits. When compared to regional data, the age spectra from the Tafí del Valle samples are most like the southern Puna Plateau, supporting derivation largely from the west and northwest. This runs counter to hypotheses suggesting these loessic sediments were derived from the low elevation plains to the east or extra-Andean Patagonia. Mapping of linear wind erosion features on the Puna Plateau yield a mean orientation of 125.7° (1 s.d. = 12.4°). These new data and existing records are consistent with a westerly-northwesterly dominated (upper- and lower-level) wind system over the southern Puna Plateau (to at least ~27° S) during periods of high dust accumulation in Tafí del Valle.

Disentangling the complex alpha taxonomy of Andean populations of Ctenomys (Rodentia: Ctenomyidae) from northern Patagonia: the need for extensive sampling in heterogeneous landscapes

Abstract In the Andean portion of northern Patagonia, populations of Ctenomys are found from low-elevation plains to high-elevation meadows and valleys. Despite their prevalence, the taxonomy of these subterranean rodents remains poorly resolved. Using genetic and morphological data obtained from museum specimens and animals collected in the field, we examined the taxonomy of Ctenomys from southwestern Mendoza Province, Argentina. Our analyses suggest the presence of at least five species of Ctenomys within the study area. The highest, innermost portion of the Andes is occupied by C. maulinus. To the east, the mountains and foothills are inhabited by two forms associated with the “mendocinus” and the “magellanicus” lineages, respectively. The former appears to be a local variant of C. emilianus, while the latter is sister to C. pontifex. Although C. pontifex was not encountered during our field sampling, it remains a valid species that likely is restricted to the isolated Valle Hermoso in westernmost Mendoza Province. In addition, we report an undescribed form from Las Leñas Valley that is associated with the “mendocinus” lineage. This complex alpha taxonomic scenario occurs within less than one degree of latitude, thereby highlighting the need to conduct detailed field collections to improve our knowledge of the systematics of Ctenomys.

Spatial and climatic variables independently drive elevational gradients in ant species richness in the Eastern Himalaya.

Elevational gradients are considered important for understanding causes behind gradients in species richness due to the large variation in climate and habitat within a small spatial extent. Geometric constraints are thought to interact with environmental variables and influence elevational patterns in species richness. However, the geographic setting of most mountain ranges, particularly continuity with low elevation areas may reduce the effect of geometric constraints at lower elevations. In the present study, we test the effects of climatic gradients and continuity with the low elevation plains of the eastern Himalayan mountain range on patterns of species richness. We studied species richness of ants (Hymenoptera: Formicidae) on an elevational gradient between 600m and 2400m in the Eastern Himalaya–part of Himalaya biodiversity hotspot. Ants were sampled in nine elevational bands of 200m with four transects in each band using pitfall and Winkler traps. We used regression models to identify the most important environmental variables that predict species richness and used constrained null models to test the effects of contiguity between the mountain range and plains. We find a monotonic decline in species richness of ants with elevation. Temperature was a more important predictor of species richness than habitat complexity. Geometric constraints model weighted by temperature with a soft lower boundary and hard upper boundary best explained the species richness pattern. This suggests that a combination of climate and geometric constraints drive the elevational species richness patterns of ants.

The Prehistoric Bison of Yellowstone National Park

On the Ground • When Yellowstone National Park (YNP) was established in 1872, American bison (Bison bison) were living in the park's forests and mountains. • A study conducted in the 1960s concluded that those were Mountain bison (Bison bison athabascae), a subspecies adapted to mountain habitat. It was assumed that those historical bison occupied their native habitat and had done so in prehistoric times. • When archaeological evidence of YNP bison was discovered in the mid-1990s it seemed reasonable to assume that those bones were derived from a herd of native prehistoric bison. • However, a review of archaeological, historical, genetic, and ecological evidence suggests a different history. Namely, herds of bison were absent before 1840. Sometime between 1840 and the mid-1850s, plains bison were driven into the mountain forest in and near YNP. In those forests, bison were relatively safe from horse-mounted, bow-and-arrow-armed Native American hunters. • Archaeological evidence suggests that YNP’s prehistoric bison were bulls that left herds on the low-elevation plains that surround the park; the bulls would have traveled up mountain drainages to the Yellowstone volcanic plateau. • Bison played no significant role in the ecological processes that shaped YNP’s prehistoric landscape. YNP’s modern bison herd is causing significant changes in range condition.

Expansion dynamics of deciduous rubber plantations in Xishuangbanna, China during 2000–2010

Monoculture rubber plantations have been replacing tropical rain forests substantially in Southern China and Southeast Asia over the past several decades, which have affected human wellbeing and ecosystem services. However, to the best of our knowledge on the extent of rubber plantation expansion and their stand ages is limited. We tracked the spatiotemporal dynamics of deciduous rubber plantations in Xishuangbanna, the second largest natural rubber production region in China, from 2000 to 2010 using time-series data from the Phased Array type L-band Synthetic Aperture Radar (PALSAR), Landsat, and Moderate Resolution Imaging Spectroradiometer (MODIS). We found that rubber plantations have been expanding across a gradient from the low-elevation plains to the high elevation mountains. The areas of deciduous rubber plantations with stand ages ≤5, 6–10, and ≥11-year old were ~1.2 × 105 ha, ~0.8 × 105 ha, and ~2.9 × 105 ha, respectively. Older rubber plantations were mainly located in low-elevation and species-rich regions (500–900 m) and younger rubber trees were distributed in areas of relative high-elevation with fragile ecosystems. Economic and market factors have driven the expansion of rubber plantations, which is not only a threat to biodiversity and environmental sustainability, but also a trigger for climatic disasters. This study illustrates that the integration of microwave, optical, and thermal data is an effective method for mapping deciduous rubber plantations in tropical mountainous regions and determining their stand ages. Our results demonstrate the spatiotemporal pattern of rubber expansions over the first decade of this century.

Age and evolution of diachronous erosion surfaces in the Amazon: Combining (U-Th)/He and cosmogenic 3He records

(U-Th)/He geochronology of two weathered plateaus in the Carajás Mountains, Pará, Brazil, reveals a history of weathering spanning from ca. 80 Ma to the present for this high elevation (∼720 m) land surface. Cosmogenic 3He measurements of hematite pebbles and blocks cemented onto the plateaus at two sites, N1 and S11D, yield erosion rates as low as 0.09 and 0.08 m Ma−1, respectively. Thus, these results confirm that the plateau surfaces are nearly immune to physical erosion for tens of millions of years. (U-Th)/He geochronology of ferruginous duricrusts blanketing the low elevation (250–100 m) plains surrounding the Carajás Mountains yield results consistently younger than ∼10 Ma. The geochronology results also reveal that the low elevation plain is diachronous, becoming progressively younger towards the receding plateaus. The spatial distribution of (U-Th)/He ages permits reconstruction of the history of scarp retreat for the Carajás landscape, showing that scarp retreat along major river valleys may have been as fast as 20 km Ma−1 during tectonically active and humid periods in the Cenozoic. The cessation of scarp retreat at some sites suggests that metamorphosed banded iron-formations and quartzites provide effective barriers to retreating escarpments, helping to preserve some of the oldest continuously exposed land surfaces on Earth.

Spatiotemporal Changes of Reference Evapotranspiration in the Highest-Latitude Region of China

Reference evapotranspiration (ET0) is often used to make management decisions for crop irrigation scheduling and production. In this study, the spatial and temporal trends of ET0 in China’s most northern province as well as the country’s largest agricultural region were analyzed for the period from 1964 to 2013. ET0 was calculated with the Penman-Monteith of Food and Agriculture Organization of the United Nations irrigation and drainage paper NO.56 (FAO-56) using climatic data collected from 27 stations. Inverse distance weighting (IDW) was used for the spatial interpolation of the estimated ET0. A Modified Mann–Kendall test (MMK) was applied to test the spatiotemporal trends of ET0, while Pearson’s correlation coefficient and cross-wavelet analysis were employed to assess the factors affecting the spatiotemporal variability at different elevations. The results from this study showed a clear decreasing trend for annual ET0 from the low elevation plain area to the high elevation mountainous area. Over the past five decades, ET0 in Heilongjiang Province decreased in all seasons, except for the winter months, during which a steady increase in temperature was found. Elevation played an important role in estimating ET0 in this higher-latitude region, while relative humidity was the most relevant meteorological factor that affected the spatiotemporal variation of ET0 in the province. Overall, the findings from the study suggest that winter ET0 in a high altitude region will continue to increase in the future as climate change persists, which could worsen spring droughts and irrigation management for semi-arid areas in the province.

Algal community ecology of two Rocky Mountain Front Range streams

This study examined the composition and ecology of benthic algal communities within two streams of the Colorado Rocky Mountains. Algal community samples as well as physical and chemical habitat parameters were collected from Boulder Creek and St. Vrain Creek between July and August, 2013. Sampling began in the high elevation montane headwaters for each stream and continued downstream to the low elevation plains locations with a total of 41 samples collected. Algal communities from each stream were dominated by diatoms. Algal cell densities and species diversity were highly variable within each stream, and there was no difference in overall cell density or species diversity between the streams. Despite the close proximity of Boulder Creek and St. Vrain Creek, differences in algal community composition were found between the two streams. Differences in the algal communities between the two streams were found to be a result of higher conductivity, temperature, and pH and increased levels of total nitrogen in Boulder Creek compared to St. Vrain Creek.

Morphometric evaluation of the Afşin-Elbistan lignite basin using kernel density estimation and Getis-Ord’s statistics of DEM derived indices, SE Turkey

A morphometric analysis of river network, basins and relief using geomorphic indices and geostatistical analyses of Digital Elevation Model (DEM) are useful tools for discussing the morphometric evolution of the basin area. In this study, three different indices including valley floor width to height ratio (Vf), stream gradient (SL), and stream sinuosity were applied to Afşin-Elbistan lignite basin to test the imprints of tectonic activity. Perturbations of these indices are usually indicative of differences in the resistance of outcropping lithological units to erosion and active faulting.To map the clusters of high and low indices values, the Kernel density estimation (K) and the Getis-Ord Gi∗ statistics were applied to the DEM-derived indices. The K method and Gi∗ statistic highlighting hot spots and cold spots of the SL index, the stream sinuosity and the Vf index values helped to identify the relative tectonic activity of the basin area. The results indicated that the estimation by the K and Gi∗ including three conceptualization of spatial relationships (CSR) for hot spots (percent volume contours 50 and 95 categorized as high and low respectively) yielded almost similar results in regions of high tectonic activity and low tectonic activity. According to the K and Getis-Ord Gi∗ statistics, the northern, northwestern and southern parts of the basin indicates a high tectonic activity. On the other hand, low elevation plain in the central part of the basin area shows a relatively low tectonic activity.

Spatiotemporal characteristics of cultural sites and their driving forces in the Ili River Valley during historical periods

This study applies ArcGIS to analyze the spatiotemporal distribution of cultural sites in the Ili River Valley in northwestern China. It explores relationships between the sites’ spatiotemporal evolutionary characteristics, human history, and the natural environment. The results indicate that the numbers and proportions of the sites, and the frequency of their occurrence, exhibited an inverted V-shaped change trend during six historical periods. The “high in the east and low in the west” spatial distribution pattern of the first three periods shifted to the one the “high in the west and low in the east” during the latter three periods, demonstrating a change in the spatial center of gravity of human activities. The sites were mainly distributed on slopes of grades 1–5, with their proportions increasing from 75% during the Spring and Autumn Period (770 BC–476 BC)–Qin Dynasty (221 BC–207 BC) to 93.75% during the Qing Dynasty–Modern period. The concentrated distribution of site elevations shifted from grades 4–8 during the Spring and Autumn Period–Qin Dynasty, and the Western Han (206 BC–8)–Southern and Northern Dynasties (420–589), to grades 1–4 during the latter three periods. The number of sites showed a shifting trend from high-elevation mountains and hills to low-elevation plains, and from high slopes to low slopes. In particular, the sites exhibited a special “moist” evolutionary pattern of migration from middle and upstream areas to downstream areas, as opposed to the migration pattern of sites located in typical arid areas. The study also considered factors influencing the distribution and spatiotemporal evolution of cultural sites, notably, human factors and natural factors.

Crustal structure of Hubei Province of China from teleseismic receiver functions: Evidence for lower crust delamination

Western Hubei Province is at the southern end of the 3000-km-long north-south-oriented Xing'anling–Taihangshan–Wulingshan topographic step in China, which separates high-rising plateaus and mountain ranges in the west from low-elevation plains in the east. We calculated teleseismic P receiver functions of 32 permanent broadband seismic stations in Hubei Province and estimated crustal thicknesses under them using the H-κ method. We also obtained detailed crustal structural images along three profiles using the CCP stacking method. The results show an east-west crustal thickness increase in the study area from 30–35km to 45–50km in less than 20km of horizontal distance, most likely in a step-wise fashion. The thin crust beneath the Nanxiang and Jianghan basins in eastern Hubei extends into the interior of the Wuling Uplift and the Huangling Massif in western Hubei. The lack of mirror symmetry between the Moho and surface topography suggests that part of the mountain ranges in western Hubei is either compensated by non-Airy-type isostasy models or is not in isostatic equilibrium but supported by the strength of the lithosphere. The brittle or localized ductile deformation in the lower crust/uppermost mantle as indicated by the abrupt Moho steps seems to be decoupled with brittle deformation in the upper crust. The CCP images also reveal an apparent double Moho beneath the Wudang Mts. which is interpreted to be due to a partially eclogitized lower crust after the original cratonic mantle lithosphere was replaced by warm and hydrated mantle materials in eastern China in the Late Mesozoic. The Moho steps were formed when a segment of eclogitized lower crust became gravitationally unstable and foundered into the mantle.

Molecular data and ecological niche modeling reveal population dynamics of widespread shrub Forsythia suspensa (Oleaceae) in China's warm-temperate zone in response to climate change during the Pleistocene.

BackgroundDespite its high number of endemic deciduous broad-leaved species in China’s warm-temperate zone, far less attention has been paid to phylogeographic studies in this region. In this work, the phylogeographic history of Forsythia suspensa endemic to China’s warm-temperate zone was investigated to explore the effect of climate change during the Pleistocene on the distribution of this deciduous broad-leaved species in China.ResultsThe cpDNA data revealed seven phylogeographical groups corresponding to geographical regions. By contrast, the nrDNA data supported the samples clustered into three groups, which was inconsistent with separate geographical regions supported by cpDNA data. Ecological niche modeling showed that the climatically suitable area during the cold period was larger than that during the warm period.ConclusionsBoth molecular data and ecological niche modeling indicated that F. suspensa expanded to nearby low-elevation plains in the glacial periods, and retreated to mountaintops during interglacial warmer stages. This study thus supported that F. suspensa persisted in situ during the glacial of the Pleistocene with enlarged distribution area, contrary to the hypothesis of long distance southward migration or large-scale range contraction.

Transpiration characteristics of a rubber plantation in central Cambodia

The rapid and widespread expansion of rubber plantations in Southeast Asia necessitates a greater understanding of tree physiology and the impacts of water consumption on local hydrology. Sap flow measurements were used to study the intra- and inter-annual variations in transpiration rate (Et) in a rubber stand in the low-elevation plain of central Cambodia. Mean stand sap flux density (JS) indicates that rubber trees actively transpire in the rainy season, but become inactive in the dry season. A sharp, brief drop in JS occurred simultaneously with leaf shedding in the middle of the dry season in January. Although the annual maxima of JS were approximately the same in the two study years, the maximum daily stand Et of ∼2.0 mm day(-1) in 2010 increased to ∼2.4 mm day(-1) in 2011. Canopy-level stomatal response was well explained by changes in solar radiation, vapor pressure deficit, soil moisture availability, leaf area, and stem diameter. Rubber trees had a relatively small potential to transpire at the beginning of the study period, compared with average diffuse-porous species. After 2 years of growth in stem diameter, transpiration potential was comparable to other species. The sensitivity of canopy conductance (gc) to atmospheric drought indicates isohydric behavior of rubber trees. Modeling also predicted a relatively small sensitivity of gc to the soil moisture deficit and a rapid decrease in gc under extreme drought conditions. However, annual observations suggest the possibility of a change in leaf characteristics with tree maturity and/or initiation of latex tapping. The estimated annual stand Et was 469 mm year(-1) in 2010, increasing to 658 mm year(-1) in 2011. Diagnostic analysis using the derived gc model showed that inter-annual change in stand Et in the rapidly growing young rubber stand was determined mainly by tree growth rate, not by differences in air and soil variables in the surrounding environment. Future research should focus on the potentially broad applicability of the relationship between Et and tree size as well as environmental factors at stands different in terms of clonal type and age.

Evaluation of relative tectonic activity in the Tehran basin, central Alborz, northern Iran

Recent deformations in the area studied control structural expansions influenced by tectonic activities, causing transformations of geologic features and morphological landforms. The Tehran basin is located at the southern edge of the central Alborz and is the result of the Arabian–Eurasian convergence and clockwise rotation of the south Caspian basin with respect to Eurasia. Hence, assessment of the drainage pattern permutations and mountain fronts appears necessary. We used six significant morphometric indices for this evaluation: stream length gradient (SL), drainage basin asymmetry (Af), hypsometric integral (Hi), ratio of valley floor width to valley height (Vf), drainage basin shape (Bs), and mountain front sinuosity (Smf). The combined analyzed indices represented the relative active tectonics (Iat). The study area was divided into four regions according to the values of Iat. These classes include class 1 (very high activity), class 2 (high), class 3 (moderate), and class 4 (low). The regions with high relative tectonic activity mostly correspond with the active structures in the basin. The tectonic activity classes 1 and 2 coincide with the fault mountain fronts in the southern edge of the central Alborz especially the North Tehran fault. The parts of the central Mosha fault and the regions in the east, the southeast, and the west of the basin indicate the moderate class of tectonic activity (class 3). The low elevation plain in the south and southwest of the area shows the lowest relative tectonic activity (class 4).

Soil moisture-temperature feedbacks at meso-scale during summer heat waves over Western Europe

This paper investigates the impact of soil moisture-temperature feedback during heatwaves occurring over France between 1989 and 2008. Two simulations of the weather research and forecasting regional model have been analysed, with two different land-surface models. One resolves the hydrology and is able to simulate summer dryness, while the other prescribes constant and high soil moisture and hence no soil moisture deficit. The sensitivity analysis conducted for all heatwave episodes highlights different soil moisture-temperature responses (1) over low-elevation plains, (2) over mountains and (3) over coastal regions. In the plains, soil moisture deficit induces less evapotranspiration and higher sensible heat flux. This has the effect of heating the planetary boundary layer and at the same time of creating a general condition of higher convective instability and a slight increase of shallow cloud cover. A positive feedback is created which increases the temperature anomaly during the heatwaves. In mountainous regions, enhanced heat fluxes over dry soil reinforce upslope winds producing strong vertical motion over the mountain slope, first triggered by thermal convection. This, jointly to the instability conditions, favors convection triggering and produces clouds and precipitation over the mountains, reducing the temperature anomaly. In coastal regions, dry soil enhances land/sea thermal contrast, strengthening sea-breeze circulation and moist cold marine air advection. This damps the magnitude of the heatwave temperature anomaly in coastal areas, expecially near the Mediterranean coast. Hence, along with heating in the plains, soil dryness can also have a significant cooling effect over mountains and coastal regions due to meso-scale circulations.

Early Cenozoic Tectonics of the Tibetan Plateau

Abstract:Geological mapping at a scale of 1:250000 coupled with related researches in recent years reveal well Early Cenozoic paleo‐tectonic evolution of the Tibetan Plateau. Marine deposits and foraminifera assemblages indicate that the Tethys‐Himalaya Ocean and the Southwest Tarim Sea existed in the south and north of the Tibetan Plateau, respectively, in Paleocene‐Eocene. The paleo‐oceanic plate between the Indian continental plate and the Lhasa block had been as wide as 900km at beginning of the Cenozoic Era. Late Paleocene transgressions of the paleo‐sea led to the formation of paleo‐bays in the southern Lhasa block. Northward subduction of the Tethys‐Himalaya Oceanic Plate caused magma emplacement and volcanic eruptions of the Linzizong Group in 64.5–44.3 Ma, which formed the Paleocene‐Eocene Gangdise Magmatic Arc in the north of Yalung‐Zangbu Suture (YZS), accompanied by intensive thrust in the Lhasa, Qiangtang, Hoh Xil and Kunlun blocks. The Paleocene‐Eocene depression of basins reached to a depth of 3500–4800 m along major thrust faults and 680–850 m along the boundary normal faults in central Tibetan Plateau, and the Paleocene‐Eocene depression of the Tarim and Qaidam basins without evident contractions were only as deep as 300–580 m and 600–830 m, respectively, far away from central Tibetan Plateau. Low elevation plains formed in the southern continental margin of the Tethy‐Himalaya Ocean, the central Tibet and the Tarim basin in Paleocene‐Early Eocene. The Tibetan Plateau and Himalaya Mts. mainly uplifted after the Indian‐Eurasian continental collision in Early‐Middle Eocene.