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Federal Register / Vol. 86, No. 41 / Thursday, March 4, 2021 / Proposed Rules
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symbiotic fungi, or a particular level of nonnative species consistent with conservation needs of the listed species.
The features may also be combinations of habitat characteristics and may encompass the relationship between characteristics or the necessary amount of a characteristic essential to support the life history of the species.
In considering whether features are essential to the conservation of the species, the Service may consider an appropriate quality, quantity, and spatial and temporal arrangement of habitat characteristics in the context of the life-history needs, condition, and status of the species. These characteristics include, but are not limited to, space for individual and population growth and for normal behavior; food, water, air, light, minerals, or other nutritional or physiological requirements; cover or shelter; sites for breeding, reproduction, or rearing or development of offspring;
and habitats that are protected from disturbance.
Physiological Requirements The Arizona eryngo needs permanently moist to saturated, alkaline, organic soils. The species is a cienega obligate and grows in wetland margins. At a minimum, soil should be moist year round immediately beneath the surface, even during drought years, as adequately moist soil is required for flowering, seed germination, and seedling survival and recruitment.
Overly dry soils may allow other more drought-tolerant species to invade, or the Arizona eryngo plants may die.
Conversely, if the soil is inundated with water for long periods, other invasive plant species may take over. Alkaline and organic soils are typical of cienegas.
Based on the above information, we determine that the Arizona eryngo needs permanently moist to saturated soils. Soils should be saturated with some standing water during winter and be at least moist just below the surface during summer.
Cienegas occupied by Arizona eryngo are associated with and fed by springs and are low-gradient wetlands that serve to slow water and trap organic materials and nutrients. Spring-dominated cienegas are maintained by fault lines crossing aquifers and/or the intersection of wetland sites with shallow aquifers overlaying a deeper, impervious layer, both of which allow for groundwater to be forced to the surface Minckley et al.
2013a, p. 214; Johnson et al. 2016, pp.
8081. Cienegas are often found in the upper reaches of small drainages or above river channels in a variety of surrounding vegetation communities,
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and thus are protected from scouring floods Sivinski and Tonne 2011, p. 2.
Cienegas have water tables at or near the ground surface Norman et al. 2019, p.
4 and are therefore maintained by the discharge of groundwater from relatively shallow aquifers. A decline in groundwater inflow recharge or increase in groundwater outflow discharge e.g., from groundwater withdrawal, drought, increased evapotranspiration can lead to reductions and disruptions in springflow, or elimination of springs and wetlands altogether Johnson et al.
2016, p. 52. The hydrological processes that maintain functional cienega habitat support resilient Arizona eryngo populations.
Finally, the Arizona eryngo needs open sun conditions Stromberg et al.
2019, p. 9. The species is more abundant in open areas than in areas shaded by riparian trees. Colony boundaries at most sites are defined by the presence of native and nonnative vegetation. Plants observed in November 2019 and January 2020 under tree canopy at La Cebadilla showed a reduction in flowering that year, and leaves appeared less upright more prostrate and etiolated pale due to reduced exposure to sunlight compared to nearby Arizona eryngo plants in sunnier conditions Li 2020a, p. 11.
Summary of Essential Physical or Biological Features We derive the specific physical or biological features essential to the conservation of the Arizona eryngo from studies of the species habitat, ecology, and life history as described below.
Additional information can be found in the SSA report Service 2020, entire;
available on http www.regulations.gov under Docket No. FWSR2ES2020
0130. We have determined that the following physical or biological features are essential to the conservation of Arizona eryngo:
1 Cienegas within the Chihuahuan and Sonoran Deserts:
a That contain permanently moist to saturated, organic, alkaline soils with some standing water in winter and that are moist at or just below the surface in summer; and b That have functional hydrological processes and are sustained by springflow via discharge of groundwater.
2 Areas of open canopy throughout the cienega.
Special Management Considerations or Protection When designating critical habitat, we assess whether the specific areas within
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the geographical area occupied by the species at the time of listing contain features which are essential to the conservation of the species and which may require special management considerations or protection. The features essential to the conservation of this species may require special management considerations or protection to reduce the following threats: Physical alteration of cienegas, water loss, and changes in co-occurring vegetation. Management activities that could ameliorate these threats include, but are not limited to: Use best management practices BMPs to minimize erosion and sedimentation;
remove and control invasive, nonnative species e.g., Johnsongrass that encroach on critical habitat; selectively manage woody vegetation that encroaches on critical habitat; exclude livestock, or in some instances where such management would further the conservation of cienega habitat and the species, use highly managed grazing;
avoid or minimize groundwater withdrawal to maintain adequate springflow to maintain cienegas; and avoid springflow diversion and springhead modification to maintain springflow to cienegas.
In summary, we find that the occupied areas we are proposing to designate as critical habitat contain the physical or biological features that are essential to the conservation of the Arizona eryngo and that may require special management considerations or protection. Special management considerations or protection may be required of the Federal action agency to eliminate, or to reduce to negligible levels, the threats affecting the essential physical or biological features of each unit.
Criteria Used To Identify Critical Habitat As required by section 4b2 of the Act, we use the best scientific data available to designate critical habitat. In accordance with the Act and our implementing regulations at 50 CFR
424.12b, we review available information pertaining to the habitat requirements of the species and identify specific areas within the geographical area occupied by the species at the time of listing and any specific areas outside the geographical area occupied by the species to be considered for designation as critical habitat. We are not currently proposing to designate any areas outside the geographical area occupied by the species because we have not identified any unoccupied areas that meet the definition of critical habitat at this time.
While the Arizona eryngo needs
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