• Start-up
  • Planning
  • Action
  • Evaluation

Climate-informed reforestation in urban riparian forests and floodplain areas.

The purpose of this project is to utilize the reforestation priority area GIS analysis to determine where to best utilize fee-in-lieu funds to reforest areas and enhance floodplain depression projects. This area is a highly active stream valley park with an interconnecting trail system in the suburbs of DC. It is a heavily used and disturbed area with a large amount of infrastructure (sewer, water, gas) and surrounding development. The plan is to be used by the Parks Department, Planning Department, and citizens and the major management goals are to improve water quality, enhance forest quality, and increase biodiversity.

Project Area

Project sites
Sligo creek is a tributary in the Northwest branch of the Anacostia watershed, which eventually feeds into the Potomac River in Maryland. 75% of the watershed is in Montgomery County and the creek is approximately 9 miles long with a drainage area close to 11.5 square miles. It is one of the most heavily urbanized sub watersheds of the Anacostia with a population density of 7,081 people per square mile. Due to this high population density and urbanization, it has severely degraded water quality and has been classified as poor water quality by the Maryland Department of the Environment.

Management Goals

A floodplain area that has been restored from wet mowed turf to a stormwater holding area with native herbs, shrubs, and trees.
  • Improve stream water quality for macroinvertebrates and fish to reflect an index or biotix integrity greater than a value of 3
  • Mitigate for local tree canopy loss due to disease and pests (Emerald Ash Borer mitigation)
  • Enhance forest quality by introducing a more complex physical structure (canopy trees, midstory trees, understory shrubs, herbaceous layer) represented by the presence or absence of birds from an array of species guilds
  • Enhance forest to be more resilient to pest and climate change
  • Increase canopy cover to provide streambank stability and to mitigate flash flood events
  • Create a mosaic of habitat to provide more diverse park-user experience and increase by diversity by (x- value on Shannon-Weiner index)

Climate Change Impacts

For this project, the most important anticipated climate change impacts include:
Rising temperatures and the urban-heat-island effect could have an amplified effect. Elevated temperatures can lead to direct heatrelated stress on urban trees and increase the rate of ground-level ozone formation
Increased temperatures during the summer and fall could cause heat stress to transplanted trees.
Longer growing season could increase the susceptibility of nursery crop to pest/disease, before/during/after transplant into new planting sites.
Longer growing seasons may be beneficial to transplanted trees and crops in the first few years of growth
Project sites are located in the downstream portion of the watershed, increased storm frequency and intensity and consequent flash flooding events could disturb and wash away site materials (trees and deer-protection caging), leading to both canopy loss a
Each project location has significant stressors already (urban area, developed, lower end of the water shed, flash flood events, non-native invasive load, Ash tree die-off, urban heat-island effect) so it is unlikely forest productivity will increase here
Declining floodplain species. Species used in previous plantings may have declining habitat pawpaw, serviceberry, pin oak, swamp white oak
Drier soil conditions late in the growing season is not currently unusual in our area. However, prolonged periods of drought at the end of the growing season could cause early dormancy for some species, leading to reduced growth over time

Challenges and Opportunities

Climate change will present challenges and opportunities for accomplishing the management objectives of this project, including:

Challenges

Flash flooding may knock out tree species before establishment, flooding may also place added pressure on stream structures and increase water quality issues
Southern or more temperate species are expected to be favored by climate change in the mid-Atlantic region, possibly narrowing our list of species to chose from.
Tree regeneration and recruitment will change, but this is already low in these areas due to deer, degraded soil conditions, flash flooding events, and non-native invasive competition
Increased temperatures could lead to decreased dissolved oxygen in waterways, leading to an overall degradation of water quality for certain species that can be difficult to mitigate for.
Declining forest health due to climate change and development pressures may increase the vulnerability of this valuable open space.

Opportunities

Restoring and enhancing floodplains
Introduce more southern/temperate species into our planting cultivar to maintain a 5:10:15 species distribution
Diversify tree species selection for reforestation efforts to enhance biodiversity, increase resilience to changing conditions in floodplain forests
Warmer stream systems may increase opportunity for new habitat for currently uncommon and rare species, possibly increasing habitat.

Adaptation Actions

Project participants used the Adaptation Workbook to develop several adaptation actions for this project, including:

Area/Topic
Approach
Tactics
Water Quality
Replace a # of failing stream structures over # of years (on NPDES permit renewal time frame over the next 3 years)
Forest
Plant # trees per year until net canopy loss in sub-watershed equals zero with fee-in-lieu funds and emerald ash borer mitigation funds. (3 years to install, 10 years to evaluate)
Forest diversity
Remove non-native invasive shrub layer and replace with native shrub layer and a diverse age class of trees, at 2 acres per year beginning in North of sub-watershed and heading South using fee-in-lieu funds. (removal, replanting and evaluation over 10yrs)
Maintain and improve (with active restoration and plantings) 10% of natural areas as meadow/open space to maintain x-value on Shannon- Weiner index (restore meadows in 3 years, evaluate success in 6 years)

Monitoring

Project participants identified several monitoring items that could help inform future management, including:
Stream index of biological integrity based off fish and macro invertebrates in sites that have had stream structures replaced or improved (will be measured every 5 years on the same rotation as existing surveys)
Forest health assessment to include canopy density, non-native invasive plant cover, and variable radius plot sampling to assess both diversity and age class distribution (Surveys will be performed by summer interns if on-board staff is unable to perform)
Success of restored meadows (these values will be measured before restoration and 5 years after restoration has occurred by comparing the Shannon-weiner diversity value)

Learn More

To learn more about this project, contact
Danielle
.

Keywords

Flooding
Forest threats
Urban
Water resources

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