A multitemporal series of aerial photos and cross-section topographic surveys have been used to analyze reach-scale channel evolution along a segment (length of about 22km) of the lower Trebbia River ...(Northern Italy) with the aims to investigate the relations between channel width vs. bed-level adjustments and to identify spatio-temporal patterns of stages of channel evolution. Dendrochronology was used to determine the age of tree establishment of riparian and island forests during channel evolution.
We identified a first phase of major adjustments (1954–1992) following a series of disturbances, dominated by channel narrowing and bed incision. During the final stage of narrowing, woody vegetation establishment contributed to stabilize new floodplain or island surfaces. A period of partial morphological recovery occurred from 1992 to 2010, dominated by an inversion of trend of channel width. During the phase of partial recovery, a stage of widening combined with a continuation of bed incision was identified, and a last stage characterized by widening and initial aggradation was observed on the central portion of the study reaches. Suitability and differences of existing channel evolution models (CEMs) derived in other geographical contexts were discussed, and a specific conceptual model comprising four stages of channel evolution was developed for the lower Trebbia River.
•Trajectories of change in channel width and bed elevation have been reconstructed.•Width vs. bed-level adjustments at reach-scale have been investigated.•Tree ring data allowed us to achieve additional information on channel evolution.•A conceptual model of channel evolution for Trebbia river has been proposed.
In this study, the early ecological succession patterns of Forni Glacier (Ortles-Cevedale group, Italian Alps) forefield along an 18-year long chronosequence (with a temporal resolution of 1 year) ...has been reported. Bacterial and fungal community structures were inferred by high-throughput sequencing of 16S rRNA gene and ITS, respectively. In addition, the occurrence of both herbaceous and arboreous plants was also recorded at each plot. A significant decrease of alpha-diversity in more recently deglaciated areas was observed for both bacteria and plants. Time since deglaciation and pH affected the structure of both fungal and bacterial communities. Pioneer plants could be a major source of colonization for both bacterial and fungal communities. Consistently, some of the most abundant bacterial taxa and some of those significantly varying with pH along the chronosequence (Polaromonas, Granulicella, Thiobacillus, Acidiferrobacter) are known to be actively involved in rock-weathering processes due to their chemolithotrophic metabolism, thus suggesting that the early phase of the chronosequence could be mainly shaped by the biologically controlled bioavailability of metals and inorganic compounds. Fungal communities were dominated by ascomycetous filamentous fungi and basidiomycetous yeasts. Their role as cold-adapted organic matter decomposers, due to their heterotrophic metabolism, was suggested.
We analysed the recent involution of glaciers in the Bernina group (Italy), which are shrinking thus permitting a rapid enlargement of the forelands. We delimited glacier outlines upon aerial ...photographs (1954 and 1981 stereo pairs analysed through an optical system) and orthophotos (2003 and 2007 digital imagines directly managed via GIS software). All the obtained data were overlapped and compared. The estimated glacier area change during 1954-2007 was −36.5 ± 2.4% (−16.2 ± 0.4 km
2
). The changes sped up more recently; in fact, during 1981-1954 (27 years) the variation was −0.206 km
2
/y, against −0.387 km
2
/y during 1981-2003 (22 years), and −0.535 km
2
/y during 2007-2003 (4 years). In the 1954-2007 period, the forelands experienced a continuous increase (+14.7 km
2
). Moreover, the analysis of the colour orthophotos allowed observations of: (i) changes affecting shape and geometry of glaciers (growing rock outcrops, tongue separations, increasing supraglacial debris and collapse structures) and (ii) main features of glacier forelands (bare rock exposures, debris and sediments and, in the latter case, occurrence of vegetation colonizing such pristine areas). Glacier forelands resulted also subjected to the action of melting water, debris transport, and periglacial processes, with consequences on landscape and geoheritage.
The Tyrrhenian side of the Central Apennines is located in a lively geological context, in which uplift/denudation dynamics played a key role in landscape evolution. Intense water erosion and ...gravitational processes led to the development of spectacular badlands on the widespread clayey hillslopes. The Crete d'Arbia badlands (as part of the Crete Senesi of Southern Tuscany) represent one of the most beautiful examples of these landforms developed on Pliocene clays. On the other hand, these rapidly evolving landforms endanger the artistic heritage of the area, as with the Monte Oliveto Maggiore Abbey that was constructed on the top of a badland hillslope and confers additional value to the landscape.
In the perspective of monitoring and reconstructing some significant phases of the relief evolution of this area an integrated approach has been used, which is based on dendrogeomorphology and geomorphological monitoring techniques. In particular, the correspondence between the data from dendrogeomorphological indicators and the measured denudation rates on badland hillslopes was tested. The sampling for dendrogeomorphological analysis has been performed in two stages on 45 trees of the
Pinus pinea L. species, on hillslopes affected by soil creep and shallow landslides, in order to identify annual ring growth anomalies,
compression wood and roots exposure. Trees' local behaviour is not homogeneous but some common trends have been detected on the basis of the
anomaly index and
compression wood. Since 1993 several monitoring stations at badland denudation “hot spots” have been equipped with erosion pins; quantitative data from monitoring stations, compared to pluviometric series, indicated critical phases of denudation that were supported by dendrochronological data. The integrated approach between dendrogeomorphology and geomorphological monitoring techniques allowed calibration of both tools in order to extend the analysis in the period preceding the field measurements. This kind of approach, capable of implementation in many contexts, could be particularly helpful in order to forecast the relief evolutionary trend.
► Tree growth anomalies allowed to reconstruct spatio-temporal evolution of relief in a calanchi area. ► Comparable erosion rates have been obtained using dendrogeomorphology and quantitative geomorphology. ► Erosion rates, compression wood and ring width anomalies are well correlated with thermo-pluviometric trends.
Geomorphic processes driven by water are particularly active in mountain environments, especially under the current climate conditions. Erosion and dissolution processes shape meaningful landforms, ...in different kinds of deposits and rocks, and in some cases they are classified as geomorphosites. Such landforms, especially earth pyramids and rock pillars, are usually characterized by a high scientific value (e.g., representativeness, ecologic support role) and by additional values (e.g., cultural and aesthetic value) contributing to the local geoheritage. Mountain geomorphosites are growing in importance within scientific community and their morphological evolution can affect the global value of the site itself (e.g., integrity). In this paper, after a first review on the terminology used for classifying landforms modelled by water runoff and on their meaning within the mountain environment, the results of a detailed research performed at two sample sites, included in the Swiss National Inventory of Geosites, are presented. The two study sites are representative respectively of: i) water runoff on glacial deposits shaping earth pyramids (Pyramides d'Euseigne); ii) water dissolution on gypsum rocks, modelling articulate karst landscapes (Pyramides de gypse du Col de la Croix). For each site, landforms evolution was investigated and denudation rates were estimated by means of different methods: iconographic material analysis, quantitative geomorphology and dendrogeomorphology on exposed roots. Despite the long-term, average rates obtained by means of roots exposure for both water runoff on glacial deposits (e.g., 5.8mm/y) and dissolution on gypsum rocks (5.6mm/y) are comparable. Moreover, a strict relation between the activity degree of processes, the integrity of the site and the assignment of geomorphosites to a specific category (i.e., active, passive or evolving passive) emerged from the results.
•Water driven processes in mountain environments are space and time-dependent.•Denudation rates are different depending on bedrock and geomorphic features.•Badlands-like landforms are meaningful as active/evolving passive geomorphosites.•Knowledge of geomorphic dynamics/rates is necessary to properly manage geoheritage.
Debris flows are very important and widespread mass movements, and represent a remarkable geomorphological hazard. This research deals with debris flows in an alpine environment, studied using ...dendrogeomorphological dating techniques, outlining their relation with precipitation, and analysing possible changes in their frequency and intensity over time. The study area is the upper Valle del Gallo (Northern Italy), a typical high mountain environment dominated by mass wasting processes, where many debris-flow fans occupy the valley bottom. Dendrogeomorphological research was conducted on twelve of these fans and two channels located on slopes. Tree growth anomalies (abrasion scars, compression wood and abrupt growth changes) were used as dating methods. Two hundred and thirty nine debris debris-flow events between 1875 and 2003 were dated using 757 trees (
Pinus montana Mill.). Analysis between dated events and precipitation suggests that debris flows in the study area could be triggered by 20–30 mm of rain concentrated in a few hours. The debris-flow frequency tends to increase gradually, but the highest value seems to have occurred in the period 1974–1983. This trend agrees with the historical occurrence of flooding events in Northern Italy as inferred by literature, and with similar studies conducted in the Swiss Alps. The results of this research are intended as a contribution for understanding the response of geomorphological processes to climatic changes.
Denudation processes affecting mountain slopes may vary according to different factors (e.g., lithology and structural setting of bedrock, climate, relief features), which may be very diverse at the ...local scale. Gully complex systems, characterised by morphological features similar to those developing in other climate contexts (i.e., pseudo-badlands) are also becoming common at higher altitudes and latitudes. The selected study cases of Gran Gorgia (Susa Valley) and Saint Nicolas (Aosta Valley), in the Western Italian Alps, are sites of geomorphological interest as they are specifically relevant for their scientific features. The aims of this work are (i) reconstructing the morphometric evolution of gully systems and vegetation colonisation time by means of multitemporal spatial analysis on surface morphological changes under water erosion; (ii) reconstructing in detail, through dendrogeomorphological analysis, the progressive spatial surface denudation and changes in erosion rates, by analysing trees and exposed roots and using different indicators (i.e., compression wood, traumatic resin ducts); (iii) obtaining data on successive aggradation/degradation episodes along slopes surrounding such hotspots through geopedological investigations; and (iv) identifying which control factors exert a predominant role on denudation patterns in such contexts. Multidisciplinary analyses regarding the study sites allowed for detailing of erosional history of the studied slopes detecting the prevailing drivers of their evolution. According to the results and considering the common climate and bedrock conditions, the structural background seems to have more influence on slope evolution at the Saint Nicolas site, while superficial geomorphic processes seem to be more relevant at the Gran Gorgia site. Because the sites have already been recognised as part of geoheritage by local authorities, the data obtained in the present research on their genesis, evolution, and local drivers affecting the rates of denudation (i.e., scientific relevance of the site) suggests that description of the sites for dissemination purposes should include links to the entire slope history.
•Multidisciplinary analyses allowed detailing erosional history of studied slopes.•Specific indicators of geomorphic disturbance were individuated for the study sites.•Weakly developed soils and buried surfaces testify diverse geomorphic contexts.•Erosion rates in study sites are higher than in analogous geomorphological contexts.•The local drivers of denudation were identified as both structural and geomorphic features.
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