Date of Award

2025-08-01

Degree Name

Doctor of Philosophy

Department

Biological Sciences

Advisor(s)

Vanessa L. Lougheed

Abstract

Desert wetlands are critical ecosystems that provide water, food, and habitat for many different species at different trophic levels. Additionally, they have the capacity to recharge aquifers, control floods, and purify water, among others. Unfortunately, they have been facing multiple environmental challenges due to different human activities, sometimes with disastrous consequences. There is an urgent need to better understand the structure and function of wetlands of different types and in different biomes in order to conserve, restore, and even create them so we can continue to obtain all the ecological services they provide. In this dissertation, I investigated how environmental factors and hydrologic variability affect the vegetation dynamics in two different desert wetlands of the southwest U.S: constructed and natural wetlands. The first data chapter (Chapter 2) examines how changes in water delivery in two constructed wetland cells influenced the development of plant communities over more than a decade of restoration activities (2005-2017). Here, the frequency of water delivery increased in Rio Bosque Wetlands Park (RB) in 2016, which gave us the unique opportunity to study the response of vegetation to water availability in the two ponds of RB prior to summer water delivery (2005, 2009, 2014) and after (2016, 2017). I found three significant changes in vegetation with water level increases: the relative frequency and cover of aquatic plants increased, a transition from upland to aquatic plants, and plant diversity increased. The second data chapter (Chapter 3) focused on elucidating the environmental factors that influence plant community structure and productivity in playa wetlands of the northern Chihuahuan Desert. I used 5 years of satellite imagery (2019 to 2024) to classify the playas according to their annual and inter-annual patterns in greenness (NDVI) and to select six representative playas from each group for direct sampling. The most significant results of this chapter were: plant productivity varied across the playas and years, the most productive vegetation was found in playas correlated with clay texture, abundant soil nitrogen, and situated in depressions or connected with arroyos. Conversely, the least productive playas were associated with gypsiferous sediments, and notably Red Lake (the least productive playa) showed high soil salinity. A reduction in vegetation productivity was also observed, coinciding with the decrease in rainfall during the year surveyed. This decrease in precipitation also coincides with the megadrought reported in this region. This dissertation highlights the importance of conducting long-term studies to observe the behavior of wetlands over time and how they can change depending on the availability of environmental factors. Also, how useful it can be to combine fieldwork, remote sensing, and GIS to interpret and visualize changes in vegetation dynamics over time.

Language

en

Provenance

Received from ProQuest

File Size

148 p.

File Format

application/pdf

Rights Holder

Enrique David Garcia

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