Filtering by
- All Subjects: southwest
- Creators: Makings, Elizabeth
I made a total of 1856 collections and reviewed past collections to produce a checklist of 729 vascular plant taxa in 403 genera and 98 families. The most species-rich family is the Poaceae, followed by Asteraceae and Fabaceae. The flora includes 159 wetland taxa, 47 endemics, and 26 taxa of conservation concern, eight of which are Federally listed. Several new populations were found in these categories and of rarely-collected taxa including one state record, three county records and several range extensions. I report on the local status of several endemics, wetland taxa with limited distributions, and relict populations of a tepary bean (Phaseolus acutifolius) that were likely transported to the region and cultivated by pre-Columbian cultures. I categorize thirteen distinct plant communities, the most abundant being Pinyon/Juniper Woodland, Chihuahuan/Apacherian Scrub, and Riparian Deciduous Forest.
Four primary factors influence floristic diversity of the Upper Verde region: 1) a location at the junction of three physiographic and floristic provinces—represented by co-occurrence of species with affinities to the Sonoran, Intermountain and Madrean regions, 2) geologic diversity—as distinct groups of species are associated with particular geologic types, 3) topographic and habitat complexity—allowing species adapted to disparate environments to co-occur, and 4) human introductions—since over 15% of the flora is composed of introduced species from Eurasia and several taxa were introduced to the region and cultivated by pre-Columbian cultures.
Interdependent systems providing water and energy services are necessary for agriculture. Climate change and increased resource demands are expected to cause frequent and severe strains on these systems. Arizona is especially vulnerable to such strains due to its hot and arid climate. However, its climate enables year-round agricultural production, allowing Arizona to supply most of the country's winter lettuce and vegetables. In addition to Phoenix and Tucson, cities including El Paso, Las Vegas, Los Angeles, and San Diego rely on Arizona for several types of agricultural products such as animal feed and livestock, meaning that disruptions to Arizona's agriculture also disrupt food supply chains to at least six major cities.
Arizona's predominately irrigated agriculture relies on water imported through an energy intensive process from water-stressed regions. Most irrigation in Arizona is electricity powered, so failures in energy or water systems can cascade to the food system, creating a food-energy-water (FEW) nexus of vulnerability. We construct a dynamic simulation model of the FEW nexus in Arizona to assess the potential impacts of increasing temperatures and disruptions to energy and water supplies on crop irrigation requirements, on-farm energy use, and yield.
We use this model to identify critical points of intersection between energy, water, and agricultural systems and quantify expected increases in resource use and yield loss. Our model is based on threshold temperatures of crops, USDA and US Geological Survey data, Arizona crop budgets, and region-specific literature. We predict that temperature increase above the baseline could decrease yields by up to 12.2% per 1 °C for major Arizona crops and require increased irrigation of about 2.6% per 1 °C. Response to drought varies widely based on crop and phenophase, so we estimate irrigation interruption effects through scenario analysis. We provide an overview of potential adaptation measures farmers can take, and barriers to implementation.
I collected soil samples from the riparian and terrestrial zones of 21 sites, placing them in growth chambers at one of two temperature regimes, and monitoring emergence of seedlings for 12 weeks. Results showed an approximately equal number of warm and cool specialists in both riparian and terrestrials zones; generalists also were abundant, particularly in the riparian zone. The number of temperature specialists and generalists in the riparian zones did not differ significantly between perennial headwater and ephemeral stream types. In montane streams, alpha diversity of the soil seed bank was highest for ephemeral reaches; in basin streams the intermittent and perennial reaches had higher diversity. Spatial turnover was primarily responsible for within stream beta-diversity—reaches had different species assemblages. The large portion of temperature specialists found in riparian seed banks indicates that even with available moisture riparian zone plant community composition will likely be impacted by changing temperatures. However, the presence of so many temperature generalists in the riparian zones suggests that some component of the seed bank is adapted to variable conditions and might offer resilience in a changing climate. Study results confirm the importance of conserving multiple hydrogeomorphic reach types because they support unique species assemblages.