community changes and related nutrient retention within an aridland constructed wastewater treatment wetland 1,3 1 2 Nicholas Weller , Daniel L. Childers , & Laura Turnbull - 1School of Sustainability, Arizona State University, Tempe, AZ., 2Institute of Hazards, Risks and Resilience, Durham University, Durham, UK., [email protected]

Introduction Results Preliminary nitrogen budget results Wetlands are increasingly used for wastewater spp. accounted for the majority of Aboveground biomass growth accounted for 19% of N treatment aboveground(AG) biomass throughout 2011 and 2012 uptake from March – July 2012 A variety of ecological processes (e.g, Total nitrogen and water flux, March – July 2012 plant & microbial nutrient uptake) 750 Total aboveground biomass Maximum peak AG biomass improve treated wastewater effluent (617,000 kg DW) occurred in S. americanus (880 kg N Average TN Total water Total N flux 600 concentration (mg/L) flux (106 m3) (103 kg) quality. retained) represented 450 July 2011; minimum AG Species-specific nutrient uptake rates biomass (93,000 kg DW) 7.9% of biomass but Inflow 7.564 ± 1.260 13.1 86 ± 3.6 kg DW DW kg 300 3 occurred in March 2012. accounted for 15% of

may influence whole system nutrient 10 150 dynamics through plant community macrophyte N retention Outflow 3.695 ± 1.034 11.1 55 ± 1.9 Figure 1. ‘Thatched’ biomass at the Tres Rios con- 0 S. acutus and S. tabernae- changes. structed wetland. Photo courtesy of Jorge Ramos during the 4 month montani’s relative abundance N retained - - 32 ± 4.0 2 3 Species specific biomass density period. Arid climates pose unique stresses to wetlands (e.g., high evapo- 1 grew through winter of 2011 transpiration rates) that are not present in temperate wetland studies. Typha spp. biomass (3579 Aboveground N retention by species 2 due to ‘thatching,’ the toppling kg N retained) accounted 4000 kg DW/m kg

Density Density of large stands of Typha spp.

3 How does plant community composition change for 11% of total system 10 1 3000 in an aridland constructed wastewater treatment Approximately 2/3 of peak AG retention and 60% of macrophyte N retention. wetland and how do those changes affect system biomass was represented by 2000 0 Typha spp. in July 2011 & 2012. nutrient dynamics? Relative abundance All aboveground biomass 1000 (5880 kg N retained) (kg) Nretained 100% S. maritimus Experimental design and methods accounted for 19% of 75% S. californicus 0 Bimonthly measurements of community composition S. americanus total N retention and 7% Schoenoplectus S. americanus Typha spp. 50% and water chemistry were taken from a 21 ha con- Schoenoplectus spp. of received N. spp. structed wetland in Phoenix, AZ starting in July 2011 25% Typha spp. Percent of biomass biomass of Percent Conclusion and Discussion 0% 1S. maritimus was not present in many 1 quadrats and was thus excluded Harvested were used to create July Sep Nov Jan Mar May July Sep Community composition varied through seasons but 2Schoenoplectus spp. refers to S. acutus species-specific multiple regression allo- 2011 2012 & S. tabernaemontani peak biomass composition remained relatively constant metric models that relate measurable plant characteristics to dry weight (DW). Typha spp. represented the majority of belowground (BG) Nitrogen content varied slightly between species Every two months, five 0.25 m2 quadrats biomass Schoenoplectus americanus had the highest N content; however, its low Above and belowground biomass, November 2011 were randomly placed along each of ten 1 average biomass density makes Typha spp. the most efficient nitrogen retaining plant per unit area. 60 m transects. Schoenoplectus spp. S. americanus S. californicus Typha spp. Total Aboveground Macrophyte community facilitated nitrogen retention is Plants were measured (using the biomass (103 kg DW) 67 25 18 113 223 characteristics found significant in Belowground a fraction of total retention 3 allometric models) at each quadrat to biomass (10 kg DW) 79 42 23 113 257 Other physical and biological process (e.g., denitrification, sedimentation) determine aboveground biomass . Above/belowground biomass 0.85 0.59 0.80 1.00 - must account reduced nitrogen export from the system.

Root cores and corresponding 1 Live S. maritimus biomass was not present in November 2011 and is thus not presented N aboveground biomass were taken to Continued monitoring and further studies will investigate calculate above- to belowground biomass Preliminary nutrient analysis shows slight variation in the role of macrophyte community changes in nutrient ratios. nitrogen content across species retention Plant and root tissue samples (harvested Continued monitoring will allow for Highest average above & Nitrogen content and density November 2011) were dried, milled, & further examination of this relationship. belowground N content was 3 40

Approx. 150 m 150 Approx. analyzed for C and N content using a 2.14% and 1.35%, respectively, S. americanus A decomposition study will examine the )

PerkinElmer 2400 CHN Analyzer. 2 Figure 2. Constructed wetland study cell for S. americanus. Schoenoplectus spp. 30 fate of nutrients retained within the with approximate locations of 10 bimonthly 2 sampled transects (denoted by red lines). Typha spp. had the lowest Typha spp. macrophyte community, an important insight in the development of biomass Seven emergent macrophyte species were present at the site: average aboveground N 20 management strategies. Schoenoplectus maritimus content (1.34%) but had the 1 Schoenoplectus tabernaemontani Typha domingensis highest nitrogen density, the 10 Development of nutrient and Figure 3. Vegetation monitoring during Schoenoplectus californicus Typha latifolia mass of nitrogen at average g/m (N Ndensity minimum live biomass in March 2012

N content (% dry(% Ncontent weight) macrophyte community dynamic Schoenoplectus americanus peak biomass per unit area, 0 0 models will aide in the understanding and management of this system. Schoenoplectus acutus, S. tabernaemontani, & S. californicus are referred to as of any species (32.2 N g/m2). AG N BG N AG peak N content content density Acknowledgements: Many thanks to the City of Phoenix, Robert Upham, CAP-LTER, the members of ASU’s Wetland Schoenoplectus spp unless otherwise noted. Typha domingensis & T. latifolia are Ecosystem Ecology Lab, & numerous field work volunteers for their assistance with this project. This research was funded referred to as Typha spp. by National Science Foundation, grant number SBE-1026865, & by the Arizona Water Resources Research Institute.