Permafrost distribution modelling in the mountains of the Mediterranean: Corral del Veleta,Sierra Nevada,Spain

A statistical model for automated mapping of the spatial distribution of permafrost in the area of Corral del Veleta in south-east Spain (3703' N, 322' W; 3398 m a.s.l.) was developed and applied. The model uses a relationship between permafrost occurrence as indicated by BTS measurements, and variables such as altitude, solar radiation and summer snow cover. The model was implemented within a geographical information system (GIS) and determines the spatial distribution of probable permafrost in Corral del Veleta. Validation was achieved by comparing the predicted permafrost distribution with the results of recent fieldwork, such as geomorphic mapping, geophysical soundings and ground temperature logging.     

Holocene environmental change in southern Spain deduced from the isotopic record of a high-elevation wetland in Sierra Nevada

Small lakes and wetlands from high elevation within the Sierra Nevada Range (southern Spain) preserve a complete post-glacial Holocene record. Isotopic, TOC and C/N analyses, carried out on a sediment core, show various stages in the evolution of the Borreguiles de la Virgen, which today constitute a small bog at about 2,950?m above sea level. Glacial erosion generated a cirque depression, which became a small lake during the first phase of infilling (from?8,200 to 5,100?cal?yr BP), as suggested by sedimentary evidence, including an atomic C/N ratio generally below 20, low TOC values and the highest ??¹³C and ??¹⁵N values of the record. These results imply significant algal productivity, which is confirmed by the microscopic algal remains. Drier conditions became established progressively in this area from?5,100 to 3,700?cal?yr BP. Subsequently, the lake evolved into a bog as shown by geochemical evidence (C/N ratios above 20, high TOC content and low ??¹³C values). Unstable conditions prevailed from?3,600 to 700?cal?yr BP; an extremely low sedimentation rate and scarcity of data from this period do not allow us to make a coherent interpretation. Fluctuating conditions were recorded during the last?~700?cal?yr BP, with wetter conditions prevailing during the first part of the interval (with C/N rate below 20) up to 350?years ago. In general, a gradual trend toward more arid conditions occurred since?~6,900?cal?yr BP, with a further increase in aridity since?~5,100?cal?yr BP. This evidence is consistent with other contemporaneous peri-Mediterranean records.     

Soil fertility evolution and landscape dynamics in a Mediterranean area: a case study in the Sant Llorenç Natural Park (Barcelona, NE Spain)

The cartography of land covers was used to study fertility and soil evolution in a mountainous Mediterranean area during the anthropocene period ( Crutzen P J 2002 Geology of mankind Nature 415 23). The aim was to determine changes in fertility as agricultural lands were abandoned in the 14 000 hectare area that constitutes Sant Llorenç del Munt Natural Park in a pre-coastal Catalan mountain range (north-eastern Iberian Peninsula). The analysis of land covers using vegetation maps, orthorectified images and aerial photography has allowed us to differentiate six vegetation groups: holm-oak wood, pine grove, oak wood, scrub, active agricultural fields and abandoned agricultural fields. The anthropic covers over the past 100 years were subdivided into five categories: active fields and those abandoned over four time periods. Study variables include field shape (concave, convex, flat), orientation (north, south) and slope (ranging from 12º to 24º). The parameters used for the physical-chemical soil analysis included organic material, phosphorous and potassium; fertility was classified based on groups, types and classes. The results indicate that even when the visual appearance of certain landscapes is similar, the edaphic characteristics may be very different. Changes induced by human disturbance share this phenomenon. Therefore, land management should be considered globally, taking into account vegetation, soils and water as interdependent factors, since it is their interaction that produces landscape and most affects its evolution over time.     

Origin and evolution of playas and blowouts in the semiarid zone of Tierra de Pinares (Duero Basin, Spain)

A large number of blowouts and playas occur in the marginal sectors of the aeolian deposits located in the southern sector of the Duero Depression (Tierra de Pinares) in Spain. The blowouts are relict landforms that were developed on sand sheets by deflation during dry periods with lower vegetation cover and a deeper water table. The studied blowouts form complexes of NW–SE and NNW–SSE elongated hollows with accompanying dunes up to 4 km long in the leeward margins. Some hollows host lakes or swampy areas related to a shallow water table. The dunes formed by NE–ENE winds show steep windward slopes and gentle leeward slopes. The studied playas, with prevalent NNW–SSE orientations, result from the aeolian excavation of terrace deposits and the underlying marly bedrock. It is probable that the formation of these depressions in an initial stage was related to deflation processes affected preferentially NNW–SSE sandy channels perpendicular to the dominant wind direction. The precipitation of salts in the playas generates aggregates of clay particles (peloids) that are easily removed by the wind. Once the bottom reached the substratum, the deepening of the depressions progressed by the deflation of particles produced by weathering of the argillaceous bedrock.     

The modern distribution of chironomid sub-fossils (Insecta: Diptera) in the Sierra Nevada, California: Potential for paleoclimatic reconstructions

Surface lake sediment was recovered from 57 lakes along an elevation gradient in the central, eastern Sierra Nevada of California. The surface sediment was analysed for subfossil chironomid remains in order to assess the modern distribution of chironomids in the region. The lakes sampled for the calibration dataset were between 2.0 and 40.0 m in depth, spanned an altitudinal gradient of 1360 m and a surface water temperature gradient of approximately 14 °C. Redundancy analysis (RDA) identified that five of the measured environmental variables – surface water temperature, elevation, depth, strontium, particulate organic carbon – accounted for a statistically significant amount of the variance in chironomid community composition. Quantitative transfer functions, based on weighted-averaging (WA), partial least squares (PLS) and weighted-averaging partial least squares (WA-PLS), were developed to estimate surface water temperature from the chironomid assemblages. The best model was a WA model with classical deshrinking, which had a relatively high coefficient of determination (r² = 0.73), low root mean square error of prediction (RMSEP = 1.2 °C) and a low maximum bias (0.90 °C). The results from this study suggest that robust quantitative estimates of past surface water temperature can be derived from the application of these models to fossil chironomid assemblages preserved in late-Quaternary lake sediment in this region.     

Oligocene to early Miocene tectono-sedimentary history of the Alicante region (SE Spain): implications for Western Mediterranean evolution

The Alicante region, situated at the intersection of major Western Mediterranean structural units, is unique in possessing a complete marine Oligocene to early Miocene record of both platform and slope deposits. Detailed analysis of three selected platform areas in the north of the region, each showing a different tectono-sedimentary history, and comparison with coeval slope deposits in the south of the region shows that: (a) during the Rupelian to early Chattian the region formed part of the Iberian microplate and can be considered the south-eastern continuation of the NW-SE-trending Iberian Chain (folding phase between 36 and 33 Ma, updoming event at 31–29 Ma, both induced by Pyrenean collision); (b) during the late Chattian to Aquitanian it was linked to the extensional, SW-NE-orientated Valencia Trough forming part of its western margin (rifting phases at 28 and 25 Ma); (c) from the Aquitanian-Burdigalian boundary (20 Ma) onward, the region underwent NW-directed compression due to Betic collision (folding phases at 20 and 17 Ma); (d) a foreland basin formed in the late Burdigalian (18–17 Ma), continuous from the Betic Cordilleras over the Alicante region to the Balearics; (e) a purely compressive regime was superseded by strike-slip tectonics at the Langhian—Serravallian boundary. The previously formulated hypotheses of coeval compression and extension with inferred hypothetical strike-slip or other faults in or near the Alicante region is rejected on the basis that compress ional and extensional tectonics are separated in time in the Alicante region.     

Talus Instability in a Recent Deglaciation Area and Its Relationship to Buried Ice and Snow Cover Evolution (Picacho Del Veleta, Sierra Nevada, Spain)

The southernmost glacier in Europe formed during the Little Ice Age at the foot of the north wall of Picacho del Veleta (3 398 m) in Sierra Nevada, in the southeast region of the Iberian Peninsula (lat. 37δ03‘N, long. 3δ22‘W). The glacier gradually retreated during the last century, leaving a large talus slope at the base of the wall. The unconsolidated material covering the ice masses acted as a thermal insulator. Recent bottom temperature of snow (BTS) analyses and drillings indicate that the ice still exists within the talus. Evidence from field observations made during the period 1995–2001, revealed that large mass movements occurred during the driest summers (1998 and especially, 1999 and 2000) when the talus was snow free. These conditions suggest a direct relationship between talus stability and thermal insulation from the snow cover in areas where buried ice or decaying marginal permafrost exists.     

Late Glacial to Early Holocene environmental adjustment in the Mediterranean semi-arid zone of the Salines playa-lake (Alacant, Spain)

The transition from the Late Glacial to the Early Holocene in the endorheic Salines sequence, which is characterized cyclical sedimentation, occurs between 5.50 and 2.85 m depth. From 5.50-3.50 m depth the cycles are composed of a centimetre alternation of layers of dolomitic marls and gypsarenites and from 3.50-2.85 m depth by the alternation of calcitic marls and calcarenites.Pollen, biotic assemblages and geochemistry provide evidence of a gap with respect to the new hydrological conditions that characterized the beginning of the Holocene. Mesic pollen taxa increased their percentages at the beginning of the Holocene, indicating climate improvement, which coincides with the 14C radiocarbon age of 10,000 years BP. The first biotic remains (gastropods, ostracods and foraminifers) found in this sequence appeared later, at 3.80 m depth, which corresponds to 9,500 years BP, whereas the mineralogical change occurred at 3.50 m depth, which corresponds to 9,000 years BP. The advanced adaptation of the vegetation and biotic aquatic assemblages with respect to the mineralogical response corresponds to a process of a gradual increase in water availability into the lacustrine system. During the Boreal, the calcitic cycles reached their maximum thickness, suggesting a more continuous water input. This assumption has also been corroborated by the expansion of the mesic pollen taxa and the occurrence of biota taxa which depend on a permanent water body for their development.The multiproxy approach in paleoclimate scenarios is an essential tool for understanding the ecosystem adjustment during climate changes. Our results demonstrate an interval of 1000 years between the vegetal and the mineralogical reaction.     

Distribution and effectiveness of nivation in Mediterranean mountains: Peñalara (Spain)

Snow accumulation is responsible for geomorphic and biogeographic processes taking place in the southern sector of the Peñalara massif in central Spain (40°51′N, 3°57′W; max. altitude 2428 m at Pico de Peñalara). This work compares the intensity of nivation on the eastern slope, leeward of the prevailing westerly winds and heavily eroded by glacial activity during the Pleistocene, to that of the western slope on the windward side, unaffected by glacial erosion and completely covered by a thick weathering mantle. On the eastern slope, nivation is effective only where the weathering mantle is exposed or on morainic formations. It does not occur on the landforms derived from glacial erosion. In contrast, the western side shows almost no evidence of snow action except where catastrophic mass movements have altered the regularity of the slope. During the post-glacial epoch, nivation cirques formed in the scars left by mass wasting. In the last 30 years, spring temperatures have increased and this activity has diminished. The pattern of evolution observed at Peñalara can be extrapolated to other Mediterranean mountains with similar characteristics such as marginal glacial activity during the Pleistocene, unconsolidated formations on the summits caused by chemical weathering, and dry, hot summers that can increase the effectiveness of nivation.     

Primary bioproductivity of mountain landscapes in the system of regional connections (Exemplified by the greater caucasus)

A structural-functional modeling of the mountainous physical-geographical country has been carried out, based on its conceptual representation as an oroclimatic system. The study revealed a statistically reliable mapping of phytobiota productivity onto the coordinates of a multidimensional ecological space, i.e. the mountain morphostructure, hydrothermics and zonal-regional structure of vegetation cover.     

The Rioja Trough (N Spain): tectosedimentary evolution of a symmetric foreland basin

ABSTRACT The Rioja Trough is the foreland basin of the western Pyrenees (to the north) and the Cameros-Demanda Massif (to the south). This E–W elongated trough is about 120×35 km. It was filled with Tertiary continental deposits (upper Eocene to upper Miocene), reaching thicknesses between 2500 and 5000 m. Both margins of the Rioja Trough are large thrusts with horizontal displacements of more than 20 km basinward. Rocks that fill the basin originated in alluvial fan and playa-lake environments, with conglomerates in the proximal sectors grading into sandstones, mudstones, lacustrine limestones and evaporites in distal sectors. The Tertiary series are horizontal in the central parts of the basin, with several E–W monoclines caused by north-verging thrusts in the basement of the basin. Near the basin margins, the Tertiary units are folded and thrusted, with several syntectonic unconformities. Calculated velocities for the Cameros-Demanda thrust range from 0.02 to1.1 mm yr^?1 (average 0.7 mm yr^?1). The sedimentation rate near the southern basin margin varies between 2 and 20 cm 1000 yr^?1 (average 10 cm 1000 yr^?1). Deposition in the Rioja Trough was strongly controlled by tectonic activity throughout the Tertiary. Eight tectosedimentary units (R1 to R8) have been characterized. These are bounded by angular unconformities at the margins and breaks in the vertical trend of the sedimentary record toward the basin centre. Every tectosedimentary unit (except R6 and R8) shows a fining-upward/coarsening-upward trend, corresponding to tectonic retrogradations and progradations, respectively. The main source area during the Palaeogene was the Cameros-Demanda Massif, whose unroofing sequence was strongly dependent on tectonic activity. During the Neogene a longitudinal WNW–ESE drainage system, with short alluvial fans in the northern and southern margins, developed. The final shape and the evolution of the Rioja Trough are the result of crustal flexure in the northern border of the Iberian plate, linked to the emplacement of the southern Pyrenean thrust system, and intraplate thrusting with basement uplift at its southern margin.     

Factors affecting vegetation and soil recovery in the Mediterranean woodland of the Canary Islands (Spain)

We investigated whether human-induced soil degradation may hinder the regeneration of a semiarid Mediterranean-type ecosystem with high biodiversity and conservation interest on the Canary Islands. To further this aim, the replacement of plant species and life-forms and the variation in soil quality were studied during the process of succession in old fields abandoned at different times and in relicts of the original thermophilous woodland by means of multivariate techniques of ordination (RDA, DCA, CCA) and clustering (k-means + IndVal). The studied ecosystem showed a limited capacity for recovery, which appears to be lower than in other similar semiarid Mediterranean ecosystems. Soil parent material exerted a considerable influence on plant reestablishment, and this process was more efficient with pumice-type rocks. Human activities have given rise to a loss of soil organic matter and an enrichment of certain nutrients, which revert to their normal levels once disturbance ceases. However, the erosion resulting from ploughing, farming and subsequent land abandonment has resulted in irreversible degradation of the soil water regime, thus severely limiting the restoration of the original ecosystem. We concluded that aridification due to soil degradation may, in certain cases, prevent the complete regeneration of thermophilous woodlands of the Canary Islands, and it must be taken into account when performing restoration activities. Pumice mulch can be useful for restoration, as it provides a suitable substrate in key stages of the plant recolonisation process.     

Historical Landscape Change in Yellowstone National Park: Demonstrating the Value of Intensive Field Observation and Repeat Photography

Although transportation and outdoor recreation are well‐recognized aspects of national parks, few studies have explored these aspects from the perspective of human geography as a means of analyzing historical landscape change. This paper offers an innovative synthesis of methods for studying cultural landscape change over time through a case study of the historical geography of transportation, tourism, and outdoor recreation along the Howard Eaton Trail (HET) in Yellowstone National Park. We conducted research through a field course that combined repeat photography, archival research, Geographic Information Systems (GIS), and traditional field methods. Results indicate that a combination of repeat photography and other methods can create an effective means of evaluating cultural landscape change; even short field courses provide opportunities for students and faculty to conduct collaborative research that provides powerful, multidimensional, situated‐learning experiences; and repeat photography creates datasets that may benefit future research and teaching.     

Reconstructing recent environmental changes using non-biting midges (Diptera: Chironomidae) in two high mountain lakes from northern Patagonia,Argentina

Remote lakes of northern Patagonia are ideal sites for examining climate- and non-climate-driven changes in aquatic ecosystems because there is little evidence of human influence and there is no detailed information on recent environmental trends in the region (i.e. the last 200 years). Subfossil chironomids (Diptera: Chironomidae) are useful paleoindicators due to their specific response to numerous environmental factors. Here, we analyze the chironomid subfossil assemblages from two remote lakes located in different environmental settings in Nahuel Huapi National Park of northern Patagonia, Argentina. Chironomids combined with sedimentary pigments (chlorophyll derivatives and total carotenoids) and organic matter provided information on the environmental history of the lakes for the last ca. 200 years. The ²¹⁰Pb chronology and tephra layers are used to establish the chronology of changes in the chironomid assemblages associated to different environmental factors that impacted the area during the period covered by the study. The deposition of volcanic ash affected the abundance and composition of chironomid assemblage throughout the record of both lakes. However, changing climate conditions and human activities are also responsible for chironomid changes in the last 50 years.     

Erosion surfaces and Neogene landscape evolution in the NE Duero Basin (north-central Spain)

We present a chronological model of erosion surface development in the Iberian and Cantabrian Ranges of north-central Spain. We map four erosion surfaces and interpret these to be related to Duero basin continental sediments and tectonic activity from Upper Oligocene to Plio-Pleistocene. The oldest erosion surface, SE1, formed across Upper Oligocene–Lower Miocene synorogenic deposits; while surface SE2 was contemporaneous with the Middle Miocene alluvial systems, ending with an uplift stage in the Astaracian. The two most recent erosion surfaces, SE3 and SE4, developed during extensional tectonic episodes and are associated with the deposition of Upper Páramo sedimentary units at the end of the Miocene (Upper Turolian) and alluvial fan deposits, known as rañas (Plio-Pleistocene). With the exception of SE1, which seems to be associated with a relatively wet climate, the surfaces formed during periods of marked aridity and generally warm temperatures. Through geostatistical reconstruction of the best preserved surface (SE2), applying ordinary kriging method to the topography (DEM) of the erosion surface and its correlating sedimentary plains, we identify the deformation processes which occurred on this surface after its formation.     

中纬度荒漠区河西走廊沙丘地貌的演化特征及其环境指示

北半球中纬度地区的沙丘地貌变化和粉尘活动历史是探索全球环境变化与景观响应问题的良好档案。本文从风沙地貌学、粒度沉积学、地球化学和气候学等方面综合分析了中纬度典型荒漠区河西走廊的典型沙丘动态变化、物质来源、粉尘活动历史及其影响因素等。结果表明,20世纪60年代以来研究区典型新月形沙丘和新月形沙丘链等发生了较大的移动或摆动,平均移动速度介于0.8~6.2 m/a之间。沙丘的动态变化主要受年降水量、年平均风速和年大风日数的影响,表明气候是沙丘地貌变化的首要影响因素。沙丘沙（三段式）与戈壁沉积物的两段式粒度曲线模式明显不同,揭示了后者在沉积学上的“不成熟性”而前者经历了高效的风成分异作用且非局地起源。古地理、沉积学和地球化学综合证据揭示沙丘沙的母源物质主要是冲洪积物和古河流沉积物等,包括南北山麓剥蚀带的碎屑沉积等。地表细颗粒物质的比例、表层盐结皮的覆盖率和可蚀性砂质物质含量等指标指示了西部戈壁区不是中东部风尘的主要来源区。沙丘移动方向与区域性主导风向在空间分布上具有相似性,表明河西走廊东、西部间之间在沙丘地貌动态演化上的差异应受控于区域尺度的环流风系,即受控于动力机制而不是物质来源上的差异。区域气候的暖湿化是对全球增温和亚洲夏季风增强的同步响应,也是研究区沙尘暴减少的主要原因,同期河西走廊潜在的逆沙漠化过程亦受控于气候变化;但绿洲区沙漠化过程还是起因于人类活动影响的地下水波动。     

The recent evolution of dune landforms and its environmental indications in the mid-latitude desert area (Hexi Corridor)

Journal of Geographical Sciences - The history of dune landform changes and dust activity at mid-latitudes is a good archive for exploring environmental changes and related landscape response. In...     

The Pinjaur dun (intermontane longitudinal valley) and associated active mountain fronts, NW Himalaya: Tectonic geomorphology and morphotectonic evolution

The Himalayan orogenic belt, formed as a result of collision tectonic processes, shows abundant evidence of neotectonic activity, active tectonics, and the occurrence of historical earthquakes. Its frontal deformation zone is characterized, in some segments, by intermontane longitudinal valleys (duns). Such frontal segments of the Himalaya are marked by the occurrence of multiple mountain fronts.In one such segment of the foothills of the NW Himalaya, the Pinjaur dun is developed and marked by three mountain fronts: MF1A and MF1B associated with the southernmost Himalayan Frontal Thrust (HFT), MF2 associated with the Sirsa fault, and MF3 associated with the Barsar thrust along the southern margin of the relatively higher main part of the sub-Himalaya. Geomorphic responses to the tectonic activity of these and related structural features have been analyzed through the use of geomorphic indices, drainage density, stream longitudinal profiles, drainage anomalies, and hypsometric analysis. Also, fault and fold growth and their expression on landform development was studied using a combination of surface profiles and field observations.The values of valley floor width to height ratio (V_f) for valleys associated with MF1 ranged between 0.07 and 0.74, and for valleys associated with MF2 ranged from 1.02–5.12. V_f for the four major valleys associated with MF1B ranged from 1.1–1.7. The asymmetry factor for 26 drainage basins related to MF1A indicate these have developed under the influence of a transverse structure. These results taken together with those obtained from the Hack profiles and SL index values, hypsometry, drainage density, and drainage anomalies suggest that the faults associated with the mountain fronts and related structures are active.Active tectonics and neotectonic activity have led to the formation of four surfaces in the Pinjaur dun. In addition, an important drainage divide separating the Sirsa and Jhajara drainage networks also developed in the intermontane valley. Surface profile analysis helped in deciphering the growth history of the fault bend fold structures of the outermost Siwalik hills. The effects of tectonic activity on the proximal part of the Indo-Gangetic plains are interpreted from the remarkable river deflections that are aligned linearly over tens of kilometers in a zone about 10 km south of the HFT.Based on these integrated structural and tectonic geomorphological approaches, a morphotectonic evolutionary model of the dun has been proposed. This model highlights the role of uplift and growth history of the fault bend fold structures of the outermost Siwalik hills on (i) the depositional landforms and drainage development of the Pinjaur dun, and (ii) valley development of the outermost Siwalik hills.Importantly, this study postulates the formation of an incipient mountain front that is evolving ahead of the HFT and the outermost Siwalik hills in the Indo-Gangetic plains.     

湖南东江湖湿地公园的资源(产)服务功能与价值研究

分析了拟建的湖南东江湖国家湿地公园的资源(产)与服务功能体系,主要包括物质生产、生态、旅游休闲功能和科研文化功能4个方面,并对其价值进行了定量估算,得出东江湖湿地公园总价值不完全估计可达1057070.74万元/a。定量化价值估算能更好地为东江湖湿地公园的规划和建设服务,以确保东江湖这一具有人类资源文化遗产价值的森林—湿地复合生态系统得到有效保护与可持续利用。