Conceptual Restoration Plan Update: Phase I
CURRENT CONDITION OF RIPARIAN HABITAT
Restoration Projects Implemented
The Task Force has been instrumental in implementing and facilitating riparian restoration projects implemented in the Project Area. With state and federal funding, the Task Force completed its first private lands restoration projects on 6 parcels on the east side of the river in the small communities of Bosquecito and Pueblito in 1999. Following these projects, the Task Force began its long term partnership with owners of a large ranch along the river north of Bosquecito. This project began in 2006 and included invasive plant control and native plant establishment.
Beginning in 2016, the Task Force established its collaboration with the U.S. Fish and Wildlife Service’s Partners Program, which provides technical and financial assistance to private landowners in order to restore or enhance fish and wildlife habitat for the benefit of migratory birds and threatened, endangered, or declining species. Since 2016, private land in the Project Area has been restored with support from the Partners Program and others. Rio Grande Agricultural Land Trust was an instrumental partner with the Task Force in completing six projects authorized by the North American Wetland Conservation Act (NAWCA).
One of the larger restoration projects that has been a focus of the Task Force is the Rhodes property. The Rhodes property is approximately 550 acres on the east side of the Rio Grande and includes approximately 2 miles of river frontage. Restoration efforts on this property have focused on: a) restoring willow and cottonwood-willow habitat that would meet specific habitat requirements of the Southwestern Willow Flycatcher (Empidonax traillii extimus) (flycatcher), and restore the conditions and processes that would support the long-term persistence of this habitat; and b) establishing a new population of Pecos sunflower (Helianthus paradoxus) on the site as well as the conditions and processes that would support the long-term persistence of this population (Keystone Assoc. 2007). Approximately 1,200 acres of this restoration have been completed to date using various funding sources.
The Sevilleta NWR and Bosque del Apache NWR (BDANWR) have also been actively restoring and enhancing riparian habitat since before 2004. The Sevilleta NWR has actively been treating saltcedar (Tamarix spp.) and Russian olive (Elaeagnus angustifolia) as well as resprouts. They have planted riparian trees and shrubs, including cottonwood, Goodding’s willow (Salix gooddingii), and coyote willow (Salix exigua) in the riparian and upland shrubs such as fourwing saltbush (Atriplex canescens) and screwbean mesquite (Prosopis pubescens) in drier habitats. BDANWR has been engaged in similar riparian and near-upland restoration projects. Work completed here has occurred both inside and outside the levee, has improved overall ecosystem health, and improved the knowledge base of restoration practices. Since the 1980s, the Service has completed several vegetation management and habitat enhancement projects at BDANWR. Over 4,000 acres of floodplain forest and wetlands have been restored. During 2015, 2016, and 2018, fuel breaks were constructed, nonnative invasive saltcedar and Russian olive were removed, and native vegetation was allowed to naturally regenerate. The goal of this work was to improve and increase the amount of native riparian habitat available for all wildlife including sensitive species, the flycatcher, and Yellow-billed Cuckoo (Coccyzus americanus) (cuckoo). Additional work includes nonnative species removal and planting of native species following fires and partnering with Bureau of Reclamation (Reclamation) to widen and realign the Rio Grande channel to improve habitat for endangered species.
Reclamation manages the Rio Grande and delta area of Elephant Butte Reservoir within the Project Area and has engaged in riparian restoration activities in partnership with the NM Interstate Stream Commission (NMISC), the U.S. Fish and Wildlife Service (Service), New Mexico State Forestry, private landowners, and the Task Force. Work in the reach has primarily focused on maintaining the river channel, improving endangered species habitat, and addressing flood control. Reclamation has completed a number of riparian habitat restoration projects in the Task Force Project Area by removing dead or nonnative vegetation and replacing it with native vegetation, planting native vegetation in burn scars, and reconnecting floodplain and river habitat.
New Mexico State Forestry has been instrumental in treating nonnative vegetation in the Project Area to address the risk of wildfire on both private lands as well as on lands owned by NM Department of Game and Fish and New Mexico Institute of Mining and Technology. Management activities have included reducing hazardous fuels and creating residential defensible space by removing dead and burned material as well as saltcedar and Russian olive. One of the larger nonnative species treatment projects conducted in the county was the Severance Project, which totaled 648 acres. This work occurred between approximately RM 104 and RM 90 on land managed by Middle Rio Grande Conservancy District (MRGCD) and Reclamation on the west side of the river and is referred to as the Central Socorro Bosque project. Riparian bosque habitat was restored using money appropriated by the New Mexico State Legislature. Most of the other treatment projects were conducted with the Socorro Soil and Water Conservation District or under the Service’s Partners Program. Socorro County has completed planning for additional treatments, especially on private lands, and is coordinating efforts for funding for project implementation.
The NMISC has implemented restoration projects along the Rio Grande within Socorro County in 2016 (SWCA 2016). Five habitat restoration projects were constructed above the SADD and five below it. The restoration sites are managed by Reclamation and MRGCD. The projects benefit the silvery minnow, flycatcher, and cuckoo.
Fire has not historically been a major driver of low-elevation riparian vegetation in the Southwest. However, the widespread proliferation of saltcedar, the presence of the tamarisk leaf beetle (Diorhabda spp.) (TLB), other stressors such as drought, and an increase in human-caused ignitions have promoted an increase in fire frequency and severity (Smith and Finch 2017).
Fires that have occurred within the Project Area since 2004 have burned over 19,000 acres. While 2017’s Tiffany Fire in Reach 5 was ignited by a lightning strike, the other listed factors led to the largest fire seen in the Project Area or throughout the Middle Rio Grande of New Mexico, in the last 20 years. The recurrence interval on these large catastrophic fires is approximately every 10-12 years.
Native cottonwood and willow are poorly adapted to fire and lack an efficient post-fire resprouting mechanism such as those found in saltcedar (Sher and Quigley 2013). A large loss of cottonwood gallery forest has occurred over time due to these fires. Post-fire vegetation growth is highly dependent on specific site conditions. Post-fire soils have significantly higher salinity than unburned soils, which might suppress the growth of cottonwood and willow seedlings if saturated soils are present when seeding occurs and allow saltcedar seedlings to proliferate (Sher and Quigley 2013). On the other hand, following the 2017 Tiffany Fire in Reach 5, early observations suggest that site conditions are conducive to native willow and cottonwood resprouts rather than saltcedar.
Tamarisk Leaf Beetle (TLB)
The TLB was released by the U.S. Department of Agriculture in 2001 as a biocontrol agent to manage saltcedar in riparian areas in the western United States. TLB biocontrol of saltcedar occurs through repeated defoliation events that ultimately results in full or partial mortality of saltcedar stands and effective suppression. Defoliation effects also initiate changes in overall plant community composition and structure, with consequential impacts to habitat structure, wildlife population dynamics, and riparian ecosystem function. TLB biocontrol is viewed as an effective method for suppressing invasive saltcedar at a landscape scale; however, the use of the beetle as a biocontrol agent produces contradictions in ecosystem function and management objectives. For example, biocontrol of saltcedar might result in reduced plant species diversity (Harms and Hiebert 2006), secondary invasions of other exotic plant species (González et al. 2017), and reduced habitat suitability for wildlife (Bateman and Johnson 2015). Moreover, it has been assumed using TLB as a biocontrol might render post-treatment mechanical or chemical treatments unnecessary. Such presumptions, however, erroneously depict riparian successional processes under anthropogenically modified floodplain settings (DeLoach et al. 2000).
TLB arrived in the upstream end of the Project Area in approximately 2013 and has been steadily dispersing south (RiversEdge West 2018). A separate study of TLB in the Rio Grande between Escondida and San Antonio (approximately Reach 4 for this Project) indicates that the northern tamarisk beetle (D. carinulata) arrived in Reach 4 in 2015, and both the subtropical beetle (D. sublineata) and Mediterranean beetle (D. elongata) arrived in summer 2017. This particular area was targeted as a potential convergence of the three species, but implications of that activity are not yet known (Tetra Tech in press(a)). Vegetation monitoring in Reach 4 indicates the proportion of understory saltcedar that is dead or dead on live suggests saltcedar-dominated areas might shift to a different species composition over time or might be undergoing self-thinning and self-pruning, a normal process in very dense forests. This shift may be induced or accelerated by the presence of TLB and associated defoliation events and effective saltcedar suppression in the sampled locations. Under altered hydrologic conditions in which cottonwood-willow regeneration is reduced, the proportion of Russian olive may increase in TLB-impacted stands. Vegetation successional patterns in altered floodplains are of particular concern for land managers and these baseline results can provide a means of comparison as vegetation structure, composition, density, and regeneration shift under disturbance factors such as TLB and altered hydrologic and floodplain conditions.
Vegetation Class Diversity
The vegetation classification system used throughout the Middle Rio Grande is the methodology developed by Hink and Ohmart (1984), which identifies six community structure (CS) types and is used to characterize major riparian habitat types. An update to the classification is conducted every 4 years by Reclamation. The original dataset was collected in 1984, was updated in 2002, and has been updated every 4 years since 2008. Five vegetation types were derived from Hink and Ohmart vegetation mapping data: native, mixed native and nonnative, open, exotic, and saltcedar (Reclamation 2016a). Open water is also noted in reaches 4–6.
Reach 1 shows a fairly steady increase in both native and mixed stands from 2002 to 2016, with the change being attributed to exotic and saltcedar removal. There was a slight increase in native and mixed to exotic and saltcedar from 2002 to 2008, but this was reduced again by 2012.
In Reach 2, the percentage of native stands remain low, but mixed stands have increased over time. Saltcedar has been reduced by over 40 percent in this reach.
Reach 3 has almost a 50-50 split of native/mixed and exotic/saltcedar.
Reaches 4–6 all show a portion of open water that is not present in the previous reaches. These open water areas are interior to each reach (within the floodplain, not riverine open water) and are due to the open water areas present at BDANWR and the Tiffany Basin area.
Reaches 4 shows a decrease in saltcedar, increase in mixed stands and decrease in native stands which could all be attributed to fires (and saltcedar removal projects) in that reach during that time.
Reach 5 shows and increase in saltcedar, and a decrease in mixed stands. This could be attributed to saltcedar invasion during this time (and is prior to the Tiffany fire that has affected that proportion). Based upon field investigation of the Tiffany fire project area, previously native and mixed stands and returning as such with additional mixed, open and even meadows habitat (Tetra Tech in press(b)). Saltcedar patches were burned with high severity and are resprouting as saltcedar or mixed stands.
Reach 6 has approximately 40 percent each native/mixed and saltcedar, with the rest being open (almost 20 percent) and open water (~5 percent).