Abstract
Riparian habitats provide a series of ecological services vital for the balance of the environment, and are niches and resources for a wide variety of species. Monitoring riparian environments at the intra-habitat level is crucial for assessing and preserving their conservation status, although it is challenging due to their landscape complexity. Unmanned aerial vehicles (UAV) and multi-spectral optical sensors can be used for very high resolution (VHR) monitoring in terms of spectral, spatial, and temporal resolutions. In this contribution, the vegetation species of the riparian habitat (91E0*, 3240 of Natura 2000 network) of North-West Italy were mapped at individual tree (ITD) level using machine learning and a multi-temporal phenology-based approach. Three UAV flights were conducted at the phenological-relevant time of the year (epochs). The data were analyzed using a structure from motion (SfM) approach. The resulting orthomosaics were segmented and classified using a random forest (RF) algorithm. The training dataset was composed of field-collected data, and was oversampled to reduce the effects of unbalancing and size. Three-hundred features were computed considering spectral, textural, and geometric information. Finally, the RF model was cross-validated (leave-one-out). This model was applied to eight scenarios that differed in temporal resolution to assess the role of multi-temporality over the UAV’s VHR optical data. Results showed better performances in multi-epoch phenology-based classification than single-epochs ones, with 0.71 overall accuracy compared to 0.61. Some classes, such as Pinus sylvestris and Betula pendula, are remarkably influenced by the phenology-based multi-temporality: the F1-score increased by 0.3 points by considering three epochs instead of two.
Highlights
Riparian habitats are an interface between terrestrial and aquatic ecosystems along inland watercourses [1] and provide a series of ecological services important for the balance of the environments with which they come into contact [2,3]
In European countries, riparian habitats are subject to several kinds of human impact that are highly detrimental for biodiversity and, for this reason, they are included in the Directive 92/43/EEC (“Habitats Directive”)
A qualitative and quantitative assessment based on the works of Persello et al and Yurtseven et al [42,43] was applied, similar to the analysis proposed in Belcore et al [44]
Summary
Riparian habitats are an interface between terrestrial and aquatic ecosystems along inland watercourses [1] and provide a series of ecological services important for the balance of the environments with which they come into contact (buffer effect against the loss of nutrients, purification of drainage water, anti-erosion action, consolidation of the banks, etc.) [2,3]. Riparian habitats develop on gravelly-sandy riverbeds with torrential regimes, with significant variations of the water table level during the year, and on alluvial soils are often flooded, features which often may hamper the evolution of the cenosis towards mature communities [4]. Such habitats’ strong dynamism is mirrored in a high vegetation structural complexity and, in turn, in a high taxa diversity. According to the habitat heterogeneity hypothesis, such vegetation structural complexity provides several ecological niches and resources for a wide variety of species, supporting a high species. Fifteen habitats are recognized in Italy, related both to standing water (lakes and ponds, Natura 2000 codes from 3110 to 3170*) and running water (river and torrents, Natura 2000 codes from 3220 to 3290)
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call