Habitat Restoration in the Middle Rio Grande

Introduction

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The Middle Rio Grande (MRG) of New Mexico is defined as the 120-mile long reach from Cochiti Dam to Elephant Butte Reservoir. The riparian riparian
Definition of riparian habitat or riparian areas.

Learn more about riparian corridor includes cottonwood-dominated forests, locally referred to as the “bosque.”

The bosque relies on a supply of flowing freshwater and shallow groundwater for survival. These ecosystems support numerous species, including threatened and endangered species such as the southwestern willow flycatcher, western yellow-billed cuckoo, Rio Grande Silvery Minnow, and the New Mexico meadow jumping mouse, and a broad suite of other wildlife guilds and flora. 

The MRG has been a focus for multiple restoration efforts aimed at improving native bosque habitat quality and quantity via hazardous fuels reduction, exotic plant species management, and revegetation. More recent projects have emphasized reestablishing or improving floodplain connectivity between the bosque and river via overbank flows, which can also increase groundwater recharge and reduce the risk of catastrophic fires. 

The Bosque Wildfire Project was initiated in response to several major wildfires in Albuquerque. This project, implemented between 2003 and 2011 by the U.S. Army Corps of Engineers (USACE) and its collaborators, included selective thinning of areas with high fuel loads and/or non-native plant species populations; removal of jetty jacks and debris; improvement of emergency access in the form of drain crossings, levee road improvement, and construction of turnarounds; and revegetation of burned and thinned areas. Revegetation treatments were intended to increase the cover of native riparian vegetation, primarily cottonwood (Populus deltoides wislizenii) and willows (Salix gooddingii and S. exigua). 

In 2011, the USACE and its collaborators initiated the Middle Rio Grande Restoration Project (MRGRP) in a 26-mile reach of the MRG to restore bosque habitat and wetland function around Albuquerque, New Mexico. The Route 66 restoration project was the MRGRP pilot project. As for the Bosque Wildfire Project, jetty jacks were removed from the bosque. However, this project also required extensive removal of non-native vegetation such as salt cedar (Tamarix ramosissima), Russian olive (Elaeagnus angustifolia), tree of heaven (Ailanthus altissima), and Siberian elm (Ulmus pumila). The project also included re-creating three high-flow channels, enhancement of one outfall wetland at the Gonzales Drain, planting of native vegetation throughout the project area, and creation of a number of willow swales. MRGRP implementation has continued since, with similar restoration work along 26 miles of the MRG through Albuquerque.

Key features of restoration continue to include construction of wetlands and swales to serve as environments for moisture-seeking plants and animals, construction of high-flow channels and bank terracing to improve hydraulic connectivity within the bosque, and revegetation with native plants. 

Key Issues Addressed

Water management and diversions have disrupted seasonal overbank flooding and floodplain connectivity throughout the Rio Grande, promoting populations of non-native plants. Along the MRG, floodplain habitat diversity has decreased, and hazardous fuel loads have increased. The loss and degradation of riparian habitat not only decreases habitat quality for native fish and wildlife of the MRG, but also puts human welfare at risk by increasing wildfires in the bosque. Recognizing that these conditions threatened the integrity of the MRG, multiple efforts such as the MRG Restoration Program (MRGRP) have been initiated to reduce non-native species and restore native species and hydrological function.

Project Goals

• Reduce the cover of non-native vegetation
• Increase the structural diversity of floodplain vegetation communities 
• Improve river-floodplain connectivity 
• Protect, extend, and enhance areas of potential habitat for listed species 
• Reduce the risk of high severity fires in the bosque 

Project Highlights

Wildlife Benefits: As one of the largest habitat restoration efforts in the southwestern United States, the MRGRP is creating new aquatic and riparian habitat and promoting ecosystem resilience.

• Phased Restoration: TheMRGRP divided the project area into five reaches, which were restored in two phases: Phase 1 was implemented between fall 2011 and winter 2014, and Phase 2 was implemented between fall 2014 and winter 2016. 
• Enhanced Hydrology: Excavation was used to reduce depth to groundwater and promote regular, seasonal flood inundation of willows. Backwaters, scallops, grading areas, terraces, high flow channels, willow banklines, willow swales, ponds, and wet-meadow depressions were engineered to inundate during moderate flow events. Ponds were engineered to be permanently inundated with shallow water. Nearly 50 water-enhancement features were constructed.
• Fuels Reduction: In wetland construction areas,woody invasive species invasive species
  An invasive species is any plant or animal that has spread or been introduced into a new area where they are, or could, cause harm to the environment, economy, or human, animal, or plant health. Their unwelcome presence can destroy ecosystems and cost millions of dollars.
  
  Learn more about invasive species , mainly non-native trees, were pulverized into wood chips via mechanical mastication and chainsaw felling. At some sites, wood chips were removed from the bosque to reduce fuel loads. At other sites, wood chips were left on-site to retain soil moisture and curtail annual weed reinvasion. Based on research in previous MRG restoration projects, a 2” thickness of wood chips left on the ground is sufficient to improve soil moisture and reduce safe sites for annual weed establishment while still allowing the spread and emergence of native rhizomatous plants.
• Informed Revegetation Design: During the planning stage, a model was developed to determine an ideal habitat matrix by examining conditions in high value wildlife areas and then applying that matrix to potential restoration sites based on soil type, depth to groundwater, existing plant cover (based on Hink and Ohmart vegetation cover and structure structure
  Something temporarily or permanently constructed, built, or placed; and constructed of natural or manufactured parts including, but not limited to, a building, shed, cabin, porch, bridge, walkway, stair steps, sign, landing, platform, dock, rack, fence, telecommunication device, antennae, fish cleaning table, satellite dish/mount, or well head.
  
  Learn more about structure types), and other site characteristics. Model outputs were also used to develop planting quantities and habitat acreage goals for each of the five reaches of the MRGRP. Approximately 127,000 potted shrubs, 9,000 tree poles, and 345,000 willow cuttings were planted. Herbaceous plugs were installed in wetlands. 
• Tree poles:
  • Rio Grande cottonwood
  • Tree willow (Salix spp.)
• Shrub cuttings:
  • Coyote willow (Salix exigua)
• Potted shrubs: 
  • Seep willow (Baccharis spp.)
  • False indigobush (Amorpha fruticosa)
  • Golden currant (Ribes aureum)
  • New Mexico olive (Forestiera neomexicana)
  • Silverleaf buffaloberry (Shepherdia argentea)
  • Three-leaf sumac (Rhus trilobata)
• Invasive Species Management: Ground cover for non-native species will be monitored and maintained below target levels throughout the life of the project. Non-native species, including Russian olive and mulberry, were left in place for wildlife benefit in some locations. Non-native species treatment techniques were:
• Mechanical mastication and/or chainsaw felling in areas designated for wetland restoration:
  • Salt cedar
  • Russian olive
  • Siberian elm
  • Mulberry (Morus spp.)
• Herbicide treatments:
  • Tree of heaven
  • Siberian elm 
  • Salt cedar
  • Mulberry
  • Russian knapweed (Acroptilon repens)
  • Perennial pepperweed (Lepidium latifolium)
  • Canada thistle (Cirsium arvense)
  • Bull thistle (Cirsium vulgare)
  • Whitetop (Lepidium spp.)
  • Ravenna grass (Saccharum ravennae) 
• Manual removal: 
  • Bull thistle
  • Ravenna grass
• Elective species removed under special circumstances:
  • Black locust (Robinia pseudoacacia)
  • Honey locust (Gleditsia triacanthos)
  • Mulberry
  • Catalpa (Catalpa spp.)
  • Osage orange (Maclura pomifera)
  • Fruit trees (Prunus spp.)
  • Junipers (Juniperus spp.)
  • Cypress (Cupressus spp.)
  • Ornamental Ash (Fraxinus spp.)
• Seeded native grasses and forbs: Two mixtures of native grasses and forbs, upland and bosque mix, were seeded with 32.5 pounds of pure-live-seeds per acre over 133 acres. The bosque mix was seeded in disturbed areas such as reclaimed access roads and below the levee while the upland mix was seeded on levee slopes, higher spoil areas, and open areas. Seeding methods included hand broadcast seeding, drill seeding, hydromulching, and hydroseeding. Phase 1 was seeded in 2012 and 2014; Phase 2 was seeded in 2016 and 2017.
• Plant species in the bosque mix:
  • Indian ricegrass (Achnatherum hymenoides)
  • Sideoats grama (Bouteloua curtipendula)
  • Saltgrass (Distichlis spicata)
  • Bottlebrush squirreltail (Elymus elymoides)
  • Annual sunflower (Helianthus annuus)
  • Green sprangletop (Leptochloa dubia)
  • Hooker’s evening primrose (Oenothera hookeri)
  • Pale evening primrose (Oenothera pallida)
  • Western wheatgrass (Pascopyrum smithii)
  • Scarlet globemallow (Sphaeralcea coccinea)
  • Alkali sacaton (Sporobolus airoides)
  • Giant dropseed (Sporobolus wrightii)
  • Sand dropseed (Sporobolus cryptandrus)
  • Regreen (Triticum spp.)
• Plant species in the upland mix:
  • Indian ricegrass (Achnatherum hymenoides)
  • Sideoats grama (Bouteloua curtipendula)
  • Fourwing saltbush (Atriplex canescens)
  • Blue grama (Bouteloua gracilis)
  • Bottlebrush squirreltail (Elymus elymoides)
  • Annual sunflower (Helianthus annuus)
  • Green sprangletop (Leptochloa dubia)
  • Hooker’s evening primrose (Oenothera hookeri)
  • Pale evening primrose (Oenothera pallida)
  • Western wheatgrass (Pascopyrum smithii)
  • James’ Galleta grass (Pleuraphis jamesii)
  • Scarlet globemallow (Sphaeralcea coccinea)
  • Alkali sacaton (Sporobolus airoides)
  • Giant dropseed (Sporobolus wrightii)
  • Sand dropseed (Sporobolus cryptandrus)
  • Regreen (Triticum spp.)
• Monitoring and Mapping Vegetation Structure: Vegetation maps were developed for project sites to track the development of riparian vegetation through time. Vegetation was classified based on the six vegetation structures developed by Hink & Ohmart (1984) which look at species canopy dominance, woody plant canopy cover, and canopy height diversity. 

Lessons Learned

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After restoration, the vegetation structure is transitioning from an open cottonwood forest to a multi-canopy forest co-dominated by cottonwood galleries interspersed with a diverse assemblage of native understory species, along with native shrublands, and willow wetlands. 

Although the survival of outplanted vegetation in some areas was lower than the 80% goal established at the project outset, the survival of New Mexico olive, seep willow, and false indigobush was relatively high across most project sites, between 62% and 79%. To achieve 20% cover, seep willow, silverleaf buffaloberry, and/or New Mexico olive should be planted at a density of 110 shrubs per acre.

Restoration did not eliminate non-native plant species. The non-native species ravenna grass, tree of heaven, and Siberian elm maintained high ground cover, challenging adaptive monitoring goals. Cover of both annual non-native weeds kochia and tumbleweed varied seasonally and was higher than the cover of the seeded grass species. Conversion of annual weed dominated communities into native grasslands is difficult without subsequent irrigation and it takes years to gauge success in the arid Southwest. As an elected species removed only under special circumstances, Russian olive was the most widespread and abundant woody species at the project sites. 

Alkali sacaton was the most abundant seeded grass. The most abundant forbs were scarlet globemallow, pale evening primrose, and annual sunflower. Along with alkali sacaton, the other Sporobolus spp. spike dropseed, giant dropseed, and sand dropseed were the most frequently observed grass species. 

Burying seed (e.g. drilling) was preferential to broadcasting seed as well as seeding during the local rainy season as opposed to other times of the year. Highest seeded plant cover (26%) resulted from drill seeding during monsoon season. Seeded sites that are re-disturbed by grading, foot traffic, and vehicular paths had the highest annual weed cover and lowest grass cover.

Next Steps

• Optimize planting rates and densities for individual plant species 
• Control encroachment of non-native species and annual weeds at a local and regional level to minimize potential for invasion and spread into MRG project sites
• Continue effectiveness and validation monitoring to observe long-term trends and improve adaptive management strategies
• Monitor the natural recruitment of plants, height and canopy growth rates to aid both adaptive management and planning for future projects
• Re-map Hink and Ohmart vegetation structure types every 3 to 5 years
• Strengthen communication with the City of Albuquerque Open Space Division, Middle Rio Grande Conservancy District, and/or Corrales Bosque Advisory Committee for continuous and timely control of invasive species and noxious weeds to meet performance standards

Resources

• U.S. Army Corps of Engineers Albuquerque District Website
• Army Corps of Engineers Fact Sheet. Middle Rio Grande Ecosystem Restoration Project, New Mexico
• Presentation at the 2013 National Conference on Ecosystem Restoration: Site Attributes and Planting Techniques for Growing Dense Willow Habitat along the Middle Rio Grande, NM
• GeoSystems Analysis, Inc. Project Profile
• Hink, V. & Ohmart, R. (1984). Middle Rio Grande Biological Survey
• Presentation at the 2015 Lower Colorado River Multi-Species Conservation Program Colorado River Terrestrial and Riparian (CRTR) Meeting. Middle Rio Grande Restoration Projects in the Albuquerque Reach: Overview and Lessons Learned

Contacts

• Danielle A. Galloway, Biologist, US Army Corps of Engineers: danielle.a.galloway@usace.army.mil
• Lynette M. Giesen, Program Manager, US Army Corps of Engineers: lynette.m.giesen@usace.army.mil
• Chad Mckenna, Ecologist/GIS Analyst, GeoSystems Analysis, Inc., chad@gsanalysis.com

Case Study Lead Author

• Andrea Lopez, Graduate Research Assistant, University of New Mexico

Suggested Citation

Lopez, A. (2018). “Habitat Restoration within the Middle Rio Grande of New Mexico.” CART. Retrieved from https://www.fws.gov/project/habitat-restoration-middle-rio-grande.