Underplanting in anticipation of bottomland ash mortality (State of WI)

State or Province
Nearest city or town
Describe the location
Avon Bottoms Wildlife Area, is located in the southwest corner of Rock County, WI. The property follows the Sugar River through the Rock County Town of Avon, from County Highway T on the Rock/Green County line to the Illinois border.
State of Wisconsin
Cover type
Plant community detail and growth stage
Southern Forest – Floodplain Forest
Forest health threats
Adaptive silviculture options
Silviculture system
Site index
70 feet
for species
silver maple
Brief silvicultural objective
The objective for management is to preserve the bottomland hardwood stand by augmenting advance regeneration prior to overstory mortality due to emerald ash borer (EAB).
Site preparation method
Soil details
Alluvial land, wet
Stand area
659 acres
Treatment area
450 acres

42.50997, -89.27571

Bottomland Hardwoods

River or stream name: 

Sugar River

River or stream type: 

Minor river or upper reaches of major river (e.g. Cannon, Zumbro, Root, Mississippi Headwaters)

Floodplain or terrace: 


Floodplain topographic position: 

Natural levee (All river types, floodplains only)

Bottom (All river types, floodplains and terraces)


A major management focus for this project is protecting the unique native communities and the associated species in the Sugar River floodplain. The Sugar River is one of the most biologically diverse river systems in Wisconsin and has been identified as a Conservation Opportunity Area to protect the significant native aquatic communities (WDNR 2006).  The Sugar River Floodplain Forest is listed as a Wetland Gem by the Wisconsin Wetlands Association.  With overstory mortality eminent in the floodplain, this trial looks at a large scale underplanting of flood tolerant tree species.

Silviculture Objective(s)

The objective of this project is to underplant approximately 450 acres of ash poletimber and sawtimber on the Avon Bottoms Wildlife Area to non-ash bottomland hardwood seedlings.  This project occurred over 2 years (2016 & 2017) and was funded by Wisconsin DNR Turkey Stamp funds.  The first stage of this project focused on 270 acres where 120,000 seedlings were planted on a 10 X 10’ grid pattern.  Species planted include American basswood, Butternut, Hackberry, Silver maple, Bur oak, Southern pin oak, Swamp white oak, and Sycamore.  The second stage of this project occurred in Spring 2017 and 80,000 seedlings were planted on approximately 180 acres.  Due to the remote nature of this planting site, no harvesting is planned for the declining/dead ash timber.  See attached map for reference.

Pre-treatment stand description and condition

Stand establishment and management history: 

This is a native bottomland hardwood stand with no evidence of recent harvests.  Avon Bottoms Wildlife Area is included in Forest Certification from the Forest Stewardship Council (FSC) and the Sustainable Forestry Initiative (SFI). Third-party certification means management of department-owned land meets standards for ecological, social, and economic sustainability. 

Pre-treatment species composition: 

See ABWA BA Dist 03012018.pdf

Pre-treatment growth and stocking: 

Total stand basal area, 94 sq. ft.  Stand stocking is variable due to the varied nature of the Sugar River floodplain (e.g. presence of ox bows, ridges, swales, etc.).

Pre-treatment forest health issues: 

Emerald ash borer (EAB) is the primary forest health threat.  EAB is already present within the project area.  Both in and outside the project area green and black ash are beginning to show crown dieback and mortality. Dense woodpecker flecking is common in and around the project area.

Landowner objectives/situation: 

With an emphasis on providing wildlife habitat and protecting aesthetic values, the overarching objective of management is to maintain the extent and enhance the quality of Avon Bottoms bottomland hardwood stands.  Managers are also to encourage native bottomland tree species such as eastern cottonwood, sycamore, swamp white oak and silver maple.

Silviculture Prescription

Plant bottomland hardwood species to increase corridor width to one quarter mile on either side of the Sugar River, where habitat and management opportunities present themselves.  Retain and regenerate swamp white oak whenever possible.  Implement measures to protect the scenic and aesthetic qualities of woodlands bordering the Sugar River while avoiding as practicable the introduction and/or spread of invasives (especially reed canary grass) in the understory of these communities.

What actually happened during the treatment

With no site preparation for planting, trees were planted April 30 – May 4, 2016.  The underplanting in Stand 10 consisted of:

  • 1,600 American basswood (seedling)
  • 6,000 Butternut (seedling)
  • 4,000 Hackberry (1-0)
  • 3,000 Hackberry (2-0)
  • 9,000 Silver maple (1-0)
  • 25,000 Bur oak (1-0)
  • 5,000 Southern pin oak (1-0)
  • 56,400 Swamp white oak (1-0)
  • 10,000 Sycamore (1-0)

Post-treatment assessment

Figure 1: The open bottomland structure of approximately 99% of the stand and the composition in which the treatment was most effective.

Figure 2: Approximately 1% of the area was composed of reed canary chocked bottomland. 

On October 31, 2018, a portion of Stand 10 was reviewed to assess seedling abundance.  For results of this survey, see Avon Bottoms ned_report_plant_species_composition_and_diversity.pdf

Plans for future treatments

Overstory removal to release seedlings

Costs and economic considerations

Figure 3: The success of this project was also due to the hardworking handplanting crew whose knowledge and proficient work helped to strengthen the regeneration results. 

Seedlings: No cost, (sourced from Wilson State Nursery, Boscobel, WI)
Seedling Storage: $300.00
Planting: $17,598.00 Spring 2016
               $11,732.00 Spring 2017

TOTAL $29,330.00

Other notes

Additional information about the location:

Avon Bottoms features a lowland hardwood forest in the floodplain of the Sugar River. Large silver maples, swamp white oaks and green ash dominate the diverse canopy of this wet-mesic forest. Other tree species are shagbark hickory, hackberry, cottonwood, bitternut hickory, bur oak, American elm and basswood. Sycamores, at the northern limit of their range, are occasionally present and black willows are common along the river. Numerous sloughs and old oxbows wind among bottomland hardwoods, grassland and agricultural cropland.

Summary / lessons learned / additional thoughts

This was a relatively straightforward project that had results that surpassed expectations. A factor in the success of the site was the species selection. Swamp white oak was selected as approximately 60-70% of the seedling stock and ended up flourishing. Southern pin oak and sycamore also did well with basswood and hackberry doing the least best.

One of the biggest lessons learned from this project was to address the stands before the main canopy begins to disappear. Once EAB has wiped out the ash, reed canary grass begins to establish itself. Results showed that planting seedlings in reed canary grass was not effective by itself and more site prep is required. Being proactive allows the understory to be planted with something that can outcompete the grass.

This case study was developed with support from the United States Department of Agriculture's National Institute for Food and Agriculture (USDA-NIFA), Renewable Resources Extension Act (RREA). Project #MIN-44-E02, principal investigator Eli Sagor, University of Minnesota.

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