Remote sensing of macrophyte morphological traits: Implications for the management of shallow lakes

Abstract

Macrophytes are important elements of freshwater ecosystems, fulfilling a pivotal role in biogeochemical cycles. The synoptic capabilities provided by remote sensing make it a powerful tool for monitoring aquatic vegetation characteristics and the functional status of shallow lake systems in which they occur. The latest generation of airborne and spaceborne imaging sensors can be effectively exploited for mapping morphologically -and physiologically -relevant vegetation features based on their canopy spectral response. The objectives of this study were to calibrate semi-empirical models for mapping macrophyte morphological traits (i.e., fractional cover, leaf area index and above-water biomass) from hyperspectral data, and to investigate the capabilities of remote sensing in supporting macrophyte monitoring and management. We calibrated spectral models using in situ reflectance and morphological trait measures and applied them to airborne hyperspectral imaging data, acquired over two shallow european water bodies (lake hídvégi, in hungary, and Mantua lakes system, in italy) in two key phenological phases. Maps of morphological traits were produced covering a broad range of aquatic plant types (submerged, floating, and emergent), common to temperate and continental regions, with an error level of 5.4% for fractional cover, 0.10 m 2 m -2 for leaf area index, and 0.06 kg m -2 for abovewater biomass. Based on these maps, we discuss how remote sensing could support monitoring strategies and shallow lake management with reference to our two case studies: i.e., by providing insight into spatial and species-wise variability, by assessing nutrient uptake by aquatic plants, and by identifying hotspot areas where invasive species could become a threat to ecosystem functioning and service provision.

Aspects of invasiveness of Ludwigia and Nelumbo in shallow temperate fluvial lakes

“…The system is characterized by high nutrient and organic matter loads and low water flow rates, resulting in its tendency towards infilling and heightened risk of hypoxia (Bolpagni et al, 2014;Pinardi et al, 2011). For this reason, since 2004, N. nucifera and T. natans macrophyte stands are controlled by cutting and occasionally harvesting (Pinardi et al, 2011;Villa et al, 2017).…”

Canopy Reflectance Modeling of Aquatic Vegetation for Algorithm Development: Global Sensitivity Analysis

“…Aquatic vegetation is a key element in the sustainability of wetland ecosystems [1,2]. According to growth habitat, aquatic vegetation can be divided into three groups: emergent vegetation, whose roots grow in the sediment underwater but whose leaves and stems emerge out of water; floating vegetation, which has leaves floating just above the water surface; and submerged vegetation, which lives entirely below the water surface [3].…”

Plant–environment interactions through a functional traits perspective: a review of Italian studies

“…Furthermore, some studies coupled the remote sensing approaches with field sampling to appreciate macrophyte's growth forms distribution at different spatial scales along time or water feature gradients in lakes (Bolpagni et al 2014;Villa et al 2015Villa et al , 2017. This constitutes a step forward for macrophyte's traits mapping going beyond the local scale, and can be used for supporting regional to continental monitoring of spatial and temporal dynamics of primary producers in freshwater ecosystems (Villa et al 2015(Villa et al , 2017.…”