Climate-Smart Vegetation Treatments - Using 15 Years of SageSTEP Data to Inform Management of Resilient Ecosystems

Background

Land managers have identified a key knowledge gap that must be filled in order to promote resilient sagebrush and woodland ecosystems in the face of joint threats of wildfire and an increasingly hot, dry, and variable climate across the West. Hotter, longer droughts could negatively impact pinyon and juniper woodlands. In areas where woodlands have expanded into sagebrush ecosystems, die-offs could be beneficial and help restore vegetation. However, drought could also increase fire risks to human communities and threaten trees in long-established woodlands and forests. Sagebrush may also be more vulnerable to die-off under extreme drought, and managers may need to consider adaptive actions to support shrubland drought resilience. Although much research to date has focused on addressing these changes in the Southwest and Colorado Plateau – where the most striking pinyon-juniper and sagebrush die-off has occurred – climate change is projected to similarly impact the Great Basin, and proactive research is required to prepare land managers for potential threats.

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As managers begin to implement the Sagebrush Conservation Design framework to protect Core Sagebrush Areas and Growth Opportunity Areas, vegetation treatments such as thinning woody plants and prescribed fire are potential tools for creating more climate-resilient ecosystems. Woody plant thinning treatments could improve ecosystem drought resilience by reducing evaporative demand and increasing soil moisture available to remaining plants. We hypothesize that vegetation treatments in sagebrush and woodland habitat interact with drought and other climate variables in ways that influence plant regeneration, expansion, and persistence over time. 

Methods

We are using 15 years of observations from a large-scale experiment—SageSTEP—taking place across 19 sites in 6 states in the Great Basin, to look at how treatments and climate interact, and how soil moisture, tree and shrub recruitment, and mortality are related. Previous research in SageSTEP plots has indicated that woody thinning treatments could improve drought resilience by increasing available soil moisture for remaining plants. However, these findings have yet to be evaluated across the full time series of microclimate and vegetation data from the experiment.

We are also partnering with researchers at the USGS Southwest Biological Science Center to make use of soil water balance modeling to predict treatment-climate interactions under future changes in climate. We will provide information on how these ecosystems and their microclimates are already changing across the biome, and forward-looking guidance on how vegetation treatments may minimize drought impacts in the future.

Long-term monitoring of the SageSTEP experiment (climate, soil moisture, and vegetation responses) presents a unique opportunity to assess treatment effectiveness over a longer time period and with more detailed annual monitoring than most management and monitoring programs are able to accomplish.

Objectives

1. Analyze trends in climate and soil moisture across the SageSTEP network of meteorological stations over the last 15 years
2. Look at how fuels reduction treatments and climate interact to influence tree and shrub recruitment and mortality
3. Determine how effective treatments are at reducing the effects of drought, and how treatment effects vary across different study sites across the Great Basin

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