Marco S. Caccianiga

Alpine screes are included into two different Natura 2000 Habitat codes: Siliceous screes of the montane to snow levels (8110) and Calcareous and calcshist screes of the montane to alpine levels (8120). The two habitats are characterized by the different bedrock. The habitat 8340 (permanent glaciers) can also include scree vegetation types. Such landforms are originated by different physical processes such as gravitative phenomena and ice-related dynamics (glaciers and permafrost actions) and mainly occur at high altitude above the treeline. Different processes result in different morphology, grain size distribution and stability and thus in different ecological and biological characteristics. However, some general shared traits can be observed, such as low overall plant cover, substrate made mainly by various-sized blocks and a variable degree of substrate instability. Additional traits may include underlying ice (particularly on debris-covered glaciers) and a complex morphology made of ridges and slopes, specifically for glacier moraines. Scree habitats are normally constant over long time period, although some abiotic natural processes such as stabilization may occur causing the increase of plant cover and species turnover. The study of these habitats include the collection of both biological and physical data, given the importance of the abiotic factors on plant life in such harsh environment. Following the official guidelines, the monitoring of scree habitat to outline their conservation status involve the collection of some parameters such as total plant cover (%), vegetation patch dimension and distance, species identification, with particular reference to indicator species of disturbance and eutrophication; alien species; woody species; endemic species, cover values for each species, visual evaluation of insect (pollinators) and vertebrate occurrence, evaluation of substrate stability. Additional important parameters, not included in the guidelines but ecologically relevant, include substrate grain size distribution, surface temperature, moisture and debris thickness (on debris-covered glaciers). Scree habitats are challenging for robotic monitoring both for the identification of the requested parameters and for the logistic difficulties of their environment, with unstable substrate, holes, rocky cliffs. Identification issues may be faced with increasing resolution, from the identification of overall plant cover, to that of morpho-functional macrocategories (shrubs, herbs, forbs, mosses, lichens) to species identification of an increasing number of selected species. On the other hand, the use of robotic monitoring may be of crucial importance for overcoming logistic issues for human operators.