Methods
Sonoran Desert Network springs monitoring is organized into the four
modules described below (see McIntyre
et al. 2018 for additional details) and eDNA inventories. All data
have undergone certification processes to ensure they have been verified
and validated for accuracy, are complete, and are fully documented. Data
used in this report are available to park staff on the NPS DataStore
and can be provided upon request.
Site Characterization
This module provides context for interpreting change in the other
modules. We record GPS locations, draw a site diagram, and describe the
spring type (e.g., helocrene, limnocrene, rheocrene, or tinaja) and its
associated vegetation in this module. Helocrene springs emerge as
low-gradient wetlands, limnocrene springs emerge as pools, and rheocrene
springs emerge as flowing streams. This module is completed once every
five years or after significant events.
Site Condition
We estimate the level of natural and anthropogenic disturbances and
the level of stress on vegetation and soils at the spring on a scale of
1–4, where 1 = undisturbed, 2 = slightly disturbed, 3 = moderately
disturbed, and 4 = highly disturbed. Types of natural disturbances can
include flooding, drying, fire, wildlife impacts, windthrow of trees and
shrubs, beaver activity, and insect infestations. Anthropogenic
disturbances can include roads, off-highway vehicle trails, hiking
trails, livestock and feral-animal impacts, removal of invasive
non-native plants, flow modification, and other evidence of human use of
the spring site. We take repeat photographs from the same location and
perspective to show the spring and its landscape context. We note the
presence of certain obligate wetland plant species (plant species that
almost always occur only in wetlands), facultative wetland plant species
(plant species that usually occur in wetlands, but also occur in other
habitats), and invasive non-native crayfish and American bullfrog
(Rana catesbeiana). We also record the density of invasive
non-native plants using a qualitative scale (1–5 plants, scattered
patches, evenly distributed patches, or a matrix). We complete the site
condition module during each springs monitoring visit.
Water Quantity
We measure the persistence of surface water, amount of spring
discharge, and wetted extent (area that contained water). To estimate
persistence, we analyze the variance of temperature measurements taken
by two logging thermometers placed at or near the orifice (spring
opening). Because water mediates variation in diurnal temperatures, data
from a submerged sensor will show less daily variation than data from an
exposed, open-air sensor; this tells us when the spring was wet or dry.
Surface discharge is measured with a timed sample of water volume.
Wetted extent is a systematic measurement of the physical length (up to
100 m), width, and depth of surface water. It is assessed using a
technique for either standing water (e.g., limnocrene and helocrene
springs) or flowing water (e.g., rheocrene springs). We complete
discharge and wetted extent measurements during each visit when
possible. Water persistence measurements are continuous throughout the
year.
Water Quality
We measure core water quality and water chemistry parameters. Core
water quality parameters include water temperature, pH, specific
conductivity (a measure of dissolved compounds and contaminants),
dissolved oxygen (how much oxygen is present in the water), and total
dissolved solids (an indicator of potentially undesirable compounds).
Discrete measurements of these parameters are collected with a
multiparameter meter. If the meter fails calibration checks, we do not
present data. Water chemistry is assessed by collecting surface water
samples and estimating the concentration of major ions with a photometer
in the field. These parameters are collected at one or more sampling
locations within a spring, but we only present data for the primary
sampling location. Each perennial spring is somewhat unique, and Arizona
has not adopted applicable water quality standards for most perennial
springs, including Expansion Spring. Ongoing, long-term data collection
at each spring will improve our understanding of the natural range in
water quality and water chemistry parameters for a given site. We
complete the water quality module during each visit when possible. The
total number of measurements value we present in the data tables is
across all years and may reflect multiple measurements taken in a single
year and missing values in other years for a variety of reasons.
eDNA Inventory of Rare Species, Invasive
Species, and Pathogens
We inventory rare species, invasive species, and pathogens in
perennial springs using environmental DNA (eDNA) techniques. One or more
5-liter water samples are collected and filtered (using a 5 µm
self-preserving mesh filter) from Expansion Spring using a Smith Root
Citizen Science Pump. Samples are preserved in ethanol prior to DNA
extraction and analysis by the Goldberg Lab at Washington State
University.
Target Organisms for the eDNA Project
The invasive non-native American bullfrog
(Rana catesbeiana) that has been observed within Montezuma
Castle National Monument along Beaver and Wet Beaver creeks (Schmidt et
al. 2006).
The pathogen chytrid fungus
(Batrachochytrium dendrobatidis), a major threat to amphibians
globally that is currently expanding in the American Southwest but has
not been previously detected in the park.
Ranaviruses, pathogens that can infect
amphibians and produce 90–100% mortality in tadpoles and adults and can
persist in affected wetlands. Ranaviruses have not been previously
detected at the park.
The native Chiricahua leopard
frog (Rana chiricahuensis), a federally designated
threatened species with a range that historically included the
watersheds within the monument (Holycross et al. 2022). The current
known range and defined critical habitat occur south of the park
(Schmidt et al. 2006), though there have been recent detections nearby
(A. Owens, personal communication).
The native lowland leopard frog (Rana
yavapaiensis), a species of conservation concern that has
historically been found within the park (Schmidt et al. 2006) but may be
locally extirpated.
The native aquatic northern
Mexican garter snake (Thamnophis eques megalops), a
federally designated threatened species that has historically been
found within the park (Schmidt et al. 2006) and may still occur within
its boundaries in suitable wetland habitats. Designated critical habitat
includes the nearby Verde River.
The native jaguar
(Panthera onca), a federally designated endangered species
that historically was found within the park, although current designated
critical habitat for jaguar recovery is located well south of the Verde
Valley.
