Hyperspectral Monitoring of Green Roof Vegetation Health State in Sub-Mediterranean Climate: Preliminary Results

Abstract

In urban and industrial environments, the constant increase of impermeable surfaces has produced drastic changes in the natural hydrological cycle. Decreasing green areas not only produce negative effects from a hydrological-hydraulic perspective, but also from an energy point of view, modifying the urban microclimate and generating, as shown in the literature, heat islands in our cities. In this context, green infrastructures may represent an environmental compensation action that can be used to re-equilibrate the hydrological and energy balance and reduce the impact of pollutant load on receiving water bodies. To ensure that a green infrastructure will work properly, vegetated areas have to be continuously monitored to verify their health state. This paper presents a ground spectroscopy monitoring survey of a green roof installed at the University of Calabria fulfilled via the acquisition and analysis of hyperspectral data. This study is part of a larger research project financed by European Structural funds aimed at understanding the influence of green roofs on rainwater management and energy consumption for air conditioning in the Mediterranean area. Reflectance values were acquired with a field-portable spectroradiometer that operates in the range of wavelengths 350–2500 nm. The survey was carried out during the time period November 2014–June 2015 and data were acquired weekly. Climatic, thermo-physical, hydrological and hydraulic quantities were acquired as well and related to spectral data. Broadband and narrowband spectral indices, related to chlorophyll content and to chlorophyll–carotenoid ratio, were computed. The two narrowband indices NDVI705 and SIPI turned out to be the most representative indices to detect the plant health status.

Next-Generation Metabolomic Profiling of Basil Leaves in Senescence by Mass Spectrometry with a Combined Approach by Fourier Transform Infrared Spectroscopy and Hyperspectral Reflectance

“…The spectral indices analyzed from the reflectance values reflect the health status of leaves, which is mostly influenced by environmental factors, developmental factors, physical factors, and biochemical factors, in which the chemical constituents play a major role in the physiological state of the leaves . In this study, two specific indices, namely, narrowband and broadband indices, are used to estimate the stress level of plants . Narrowband indices represent specific wavelengths linked to plant pigments, and changes in the values are related to the health status of the plant.…”

“…19 In this study, two specific indices, namely, narrowband and broadband indices, are used to estimate the stress level of plants. 20 Narrowband indices represent specific wavelengths linked to plant pigments, and changes in the values are related to the health status of the plant. Broadband indices are based on specific wavelengths associated with green, red, visible, and NIR regions, which reveals the metabolic response during development and under stress conditions (Table S1).…”

Design of a Remote-Controlled Platform for Green Roof Plants Monitoring via Hyperspectral Sensors

“…The spectra of plants in a healthy and unhealthy state for the three species monitored in this study (not shown) highlighted that spectral signatures of plants in a healthy state presented the characteristic behaviour of vegetation described in Reference [20] and briefly described in the introduction. In Reference [25], a preliminary investigation of the trend of a limited number of vegetation indices within the monitoring period for all the species under investigation is presented. All trends revealed an initial suffering period (December 2014-March 2015) after which the vegetation health improved.…”

“…To this aim, the field-portable spectroradiometer FieldSpec 4-ASD was employed. For a detailed description of the site under investigation and data acquisition refer to References [13,25], respectively. Within the monitoring period (December 2014-June 2015) two canopies of each plant species, for a total of six plants, were monitored.…”

“…The study area was equipped with suitable devices for the monitoring of climatic, thermo-physical, hydrological and hydraulic quantities [25]. Solar radiation and air temperature were recorded during the sampling time by the monitoring system the green roof was equipped with.…”