Tree rings as ecological indicator of geomorphic activity in geoheritage studies

Abstract

Mountain areas are characterized by geomorphic processes, especially mass wasting and avalanches, which may impact the landscape affecting also the biological component, trees included. If sites colonized by trees are characterized by geomorphic features with a high Global and Scientific Value, including Representativeness of geomorphological processes, Educational Exemplarity, and Integrity, they can be considered geomorphosites. In the framework of assessment of the Scientific Value of geomorphosites, Ecological Support Role is of great importance. Hence, tree rings derived information can be used as indicators to refine the Scientific Value of the sites and also to propose multidisciplinary approaches to understand landscape dynamics. In fact, trees colonizing sites of geomorphological interest are used for detecting past and present events and tree rings may be considered ecological indicators under different points of view. Arboreal vegetation can register growth disturbances in terms of morphological features, at macro-(particular morphologies of trunks) and micro-scale (annual growth rings, stress indicators like compression wood, traumatic resin ducts), becoming a powerful indicator of the geomorphic activity affecting the landscape. In some cases, combined with other techniques like climate data analysis, they may allow refining the often lacunose historical records of geomorphic events impacting different territories. The integrated analysis carried out in the Loana Valley (Sesia Val Grande Geopark, Western Italian Alps), considering a selection of geomorphosites affected by mass wasting processes and avalanches and located along a touristic trail, allow to detect which meteorological thresholds favour hydrogeological instability (i.e. overcome of Mean Annual Rainfalls of 6-10%). Tree rings data coming from the investigated sites provided information on the recurrence of geomorphic activity allowing filling gaps within the historical archives by individuating years during which hydrogeological or snow-related events probably occurred and that were missed (i.e. 1986, 1989, 2001, 2007), and providing details on sites for which temporal constraints had not been found before (i.e. Pizzo Stagno Complex System). Finally, investigated sites demonstrated to differently record the history of instability affecting the area and this difference is mirrored in the sites values that are adopted in the framework of geoheritage analysis (Scientific Value, Ecological Support Role and Educational Exemplarity). The proposed multidisciplinary approach, including geomorphology, dendrogeomorphology and climatology, represents, hence, a useful tool in geoheritage valorisation and management strategies.

Fieldtrips and Virtual Tours as Geotourism Resources: Examples from the Sesia Val Grande UNESCO Global Geopark (NW Italy)

“…As an example, the Vigezzo Valley represents an important geological and geomorphological spot for the geopark where it is possible to retrieve witnesses on Earth evolution at different spatio-temporal scales: (i) the effects of one of the most disastrous hydrogeological instability events in the Western Italian Alps occurred on 7th August 1978 [113]; (ii) the evidences of the tectonic activity of the Centovalli Line, related to the Simplon Line tectonic system and affecting paleoenvironmental settings, as well as current slope instabilities [124]; (iii) the mineralogical richness that allowed the identification of new mineralogical species (e.g., Vigezzite [125]).…”

“…Ecologic support role on landforms-the geomorphic processes interesting currently and during the past the Loana valley deeply affect the vegetation distribution in the area. Bollati et al [99,113] detected specific patterns of disturbance on vegetation growing on the geosites located along the valley bottom (18, SF 1; b, c, SF 4-I), and on vegetation growing on carbonate isolated reliefs modelled by glaciers in the past, near the head of the valley (17, SF 1; Figure 12b). These results were proposed in form of simple exercises, addressed to general public and schools, allowing them to relate the vegetation behavior with the geomorphological activity (Figure 9c).…”

Geoheritage in Deltaic Environments: Classification Notes, Case Example, and Geopark Implication

“…In contrast, wetlands are often characterised by significant scenic value [49][50][51][52] determined by the dominance of water objects and dense vegetation in the perceived landscape image (Figure 4). Consequently, the full-scale integration of geo-and other natural heritage features [25] that is offered by geoparks recompenses the noted deficiency of visibility of its unique geological features. This is especially important in the case of geotourism activities.…”

“…The latter is strongly tied to the resource, i.e., the socio-economic importance of the deltaic environment. This category may also include unique geological and geomorphological features (such as landforms) which facilitate the growth of wetlands and perpetuate specific habitats, i.e., features that provide ecological support [25].…”

Alpine gullies system evolution: erosion drivers and control factors. Two examples from the western Italian Alps

“…The Compression Wood (CW) is a particular, resistant, and denser kind of wood produced by the tree in response to mechanical stress induced by the tilting of the stem (Fig. 3) caused mainly to creep or other destabilising processes (e.g., Timell, 1986;Bollati et al, 2018). Traumatic Resin Ducts (TRDs) are aligned resin ducts, which are specific features that may be produced in trunks affected by traumas deriving from the impact of material caused by geomorphic processes inducing debris transport (e.g., snow avalanches, debris flows, rock falls) (e.g., Bollschweiler et al, 2008;Garavaglia and Pelfini, 2011).…”