Semester of Graduation
Spring 2024
Degree
Master of Renewable Natural Resources (SRNR)
Document Type
Thesis
Abstract
Inundated baldcypress (Taxodium distichum) trees generally respond to secondarily-treated and disinfected municipal effluent additions with increased growth rates and reduced mortality. Yet, the effects of effluent additions on the water-use and functional traits of inundated mature baldcypress are poorly understood. Because increased tree growth is associated with increased water use, effluent additions may affect the water budget in coastal swamps by increasing water uptake from the rhizosphere due to increased tree transpiration. I used sap flux density (fd) measurements to assess water-use traits and tree-level daily transpiration (E) in seven mature inundated baldcypress trees that had received effluent for 19 years (treatment site) and compared them to seven similar trees in a nearby swamp that did not receive effluent (control site). I quantified whole-tree canopy conductance standardized per unit sapwood-area (GAsw) at the reference atmospheric vapor pressure deficit (VPD) of 1 kPa (Gref), GAsw sensitivity to VPD (βvpd), maximum sap flux density (fd,max), and the VPD threshold at which fd,max was reached (VPDmax). Additionally, I measured basal area increment (BAI), wood density (WD) of branch, sapwood, and heartwood (WDbranch, WDcore,sw, and WDcore,hw, respectively), and leaf mass per area (LMA) to determine effects of effluent additions on growth rates and functional traits. I found that for any given tree size, trees at the treatment site transpire about 5.8 more L of water per day. However, none of the water-use traits varied between the treatment and control site. BAI was higher at the treatment site than the control site, suggesting that higher nutrient availability lead to higher growth in the presence of effluent discharge. WDcore,hw was significantly lower in the treatment site than the control site. Foliar N:P was positively correlated with higher Gref and βvpd, suggesting that effluent additions shifted trees to higher water use when VPD was relatively low, but that water use was more sensitive to VPD. My results suggest that when effluent additions increase forest productivity it can also increase E, but these effects may be modulated by high VPD as projected under climate change.
Date
4-4-2024
Recommended Citation
Schexnayder, Devin, "Effects of treated effluent discharge on tree water use and growth in a cypress swamp." (2024). LSU Master's Theses. 5976.
https://repository.lsu.edu/gradschool_theses/5976
Committee Chair
Brett Wolfe
Included in
Forest Biology Commons, Forest Management Commons, Other Forestry and Forest Sciences Commons, Terrestrial and Aquatic Ecology Commons