Monitoring the Water Stress of an Indoor Living Wall System Using the "Triangle Method".

Xu Yuan,J Antonio Guzmán Q,Arturo Sanchez-Azofeifa,Kati Laakso,Chad Daniel Davis,Qinglin Meng

doi:10.3390/s20113261

Xu Yuan, J Antonio Guzmán Q + Show 4 more

Open Access

https://doi.org/10.3390/s20113261

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Abstract

Living walls are important vertical greening systems with modular prevegetated structures. Studies have suggested that living walls have many social benefits as an ecological engineering technique with notable potential for reconciliation ecology. Despite these benefits, there are currently no mature workflows or technologies for monitoring the health status and water stress of living wall systems. To partially fill the current knowledge gap related to water stress, we acquired thermal, multispectral, and hyperspectral remote sensing data from an indoor living wall in the Cloud Forest of the Gardens by the Bay, Singapore. The surface temperature (Ts) and a normalized difference vegetation index (NDVI) were obtained from these data to construct a Ts-NDVI space for applying the “triangle method”. A simple and effective algorithm was proposed to determine the dry and wet edges, the key components of the said method. The pixels associated with the dry and wet edges were then selected and highlighted to directly display the areas under water-stress conditions. Our results suggest that the proposed algorithm can provide a reasonable overview of the water-stress information of the living wall; therefore, our method can be simple and effective to monitor the health status of a living wall. Furthermore, our work confirms that the triangle method can be transferred from the outdoors to an indoor environment.

Highlights

Vertical greening systems, the result of plants being attached to buildings using different kinds of supporting mechanisms, is one way to improve the environmental conditions of urban areas [1].The systems can be classified into green facades and living walls [2,3] based on their architecture [4].Green facades are built using climbers supported by various mechanisms.Living walls, known as green walls and vertical gardens, are modular prevegetated structures where each module contains a growing medium and piping systems for irrigation [2]
The study presents a simple and effective approach to monitor the health status of an indoor living wall entirely based on remote sensing imagery and no empirical relations
Our study suggests that the triangle method has the applicability to monitor the water stress of a living wall

Summary

Introduction

The systems can be classified into green facades and living walls [2,3] based on their architecture [4]. Known as green walls and vertical gardens, are modular prevegetated structures where each module contains a growing medium (e.g., soil; [1]) and piping systems for irrigation [2]. These systems can be continuous or modular based on their supporting structure. Continuous systems have lightweight screens where plants are potted individually, whereas modular systems have a growing substrate in a fixed vertical structure [5]

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