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Vegetation recovery in western USA and Alaska coniferous forest ecosystems a decade after major wildfires

Status: 
Action
Dates: 
August, 2014 to July, 2018

Although post-fire vegetation recovery after 1-3 years has been relatively well studied, vegetation conditions a decade post-fire are less studied, yet likely more relevant for assessing ecosystem response and resilience to fire and implications for managers. The free availability of the entire Landsat image archive has stimulated development of powerful image time series analysis techniques such as Landsat-based Detection of Trends in Disturbance and Recovery (LandTrendr) to map multiple disturbances and post-disturbance vegetation recovery. Quantifying post-fire vegetation recovery rates as a function of burn severity is important if we are to plan effective strategies for fuel and fire management of post-fire landscape mosaics. Severe fire reduces not only fuel loads available for subsequent fires but also understory plant cover and diversity and tree regeneration. The time required for recovery of these and other metrics of ecosystem condition of interest to land managers differs between different vegetation types but are poorly quantified. Longer-term field measures are needed to better understand these ecological trajectories. Links to remotely sensed data are needed to upscale these measures to the landscape level where fuel and fire management decisions are made.

Approach

Fig. 1. Wildfires (n=15) included in our long-term vegetation recovery project.
Fifteen wildfires are included in this long-term vegetation recovery project.

  • We are collecting vegetation data 8-15 years following fifteen fires distributed across five different vegetation types: boreal, moist mixed conifer, dry mixed conifer, and ponderosa pine forests, and chaparral (Fig. 1).

  • Field site selection was based on a stratified random sampling design using one-year post-fire dNBR burn severity data retrieved from the national Monitoring Trends in Burn Severity (MTBS) project, elevation, and transformed aspect (Fig. 2).

  • We will relate field plot measures to LandTrendr image products to assess landscape-level implications of large fires on fuel loads, fuel treatment longevity, vegetation cover, and plant community composition.

  • We will produce maps of recovery rates for fuels and vegetation conditioned on recent fire history, vegetation type, burn severity and geographic location.

  • We will hold a workshop in McCall, Idaho and a webinar through the Northern Rockies Fire Science Consortium to inform fuel and fire managers on how post-fire fuel and vegetation trajectories influence fuel and fire management options, focused on effectiveness in limiting fire extent and burn severity of subsequent fires and furthering vegetation management goals.

Key Findings

  • Less common species show effects of burn severity thirteen years post-fire

  • Higher burn severity increases the persistence of non-native plant cover

  • Post-fire mulching treatments do not affect seedling densities but do affect seedling species composition ten years post-fire

  • Density of regenerating seedlings depends more on distance to seed source than burn severity

  • Recovery rates as characterized from Landsat image time series are similar regardless of burn severity, but higher burn severity requires a longer recovery time

  • Cover fractions of green vegetation, non-photosynthetic vegetation, soil, and char are useful variables for monitoring because they can be estimated both in the field and remotely

     

Fig. 2. Example of landscape stratification for field sampling (2002 Hayman fire shown).
Field site selection was based on a stratified random sampling design using one-year post-fire burn severity data, elevation, and transformed aspect.

Other

Related Documents

LandTrendr: http://geotrendr.ceoas.oregonstate.edu/landtrendr/

University of Idaho work on the project is described here: https://www.frames.gov/partner-sites/long-term-recovery/home/



Project Contact: 

Principal Investigators:
Co-Investigators:
Eva Strand - University of Idaho
Penny Morgan - University of Idaho
Beth Newingham - Agricultural Research Service

Collaborators:
Alistair M.S. Smith - University of Idaho
Jan Eitel - University of Idaho
Robert Kennedy - Oregon State University

Research Staff:
Funding Contributors:
Joint Fire Science Program