Monitoring of Phragmites australis in a constructed wetland. A method for data aggregation

Abstract

A constructed wetland was built on Italian Alps in 2007; this plant was monitored for three years through surveys every two weeks, checking and examining all its components, including vegetation, composed by Phragmites australis (PA). For reed monitoring, a representative PA sample was identified, and measurements were made considering plants belonging to this sample. Many parameters were considered, depending on the season and on plants development: stems number and height during spring and summer, presence and number of inflorescences in summer. During the second and the third growing season (spring and summer 2009 and 2010) also the percentage of substratum covered by plants. Two different aggregation parameters were created both to aggregate collected data and to define a methodology for the monitoring of plants health and functionality in constructed wetlands: Development Parameter (DP) and Population Parameter (PP). Aggregation parameters were structured to contain all the collected data referred to a single phytoremediation bed, considering different weights for parameters with different importance in PA functionality into the constructed wetland. DP was calculated for 2008 growing season, when PA density was still low. It determines plants average development degree in phytoremediation beds. PP was calculated for both 2009 and 2010 growing season, when plants spread over gravel beds substratum was high. It determines plants population development, considering the vegetal component of the phytoremediation system as a whole, and each pool as an ecosystem. From DP and PP implementation, reeds into the constructed wetlands had a limited development during the first growing season, and a very good development during second and third growing season, forming a functional population in each gravel bed.