Climate smart management strategies for dryland shrublands and woodlands

Photo Credit

USDA Forest Service photo

The collaborative working group developing climate smart management strategies for dryland shrublands and woodlands, taken in the Pine Valley District of the Dixie National Forest. The group is made up of people from the district, national forest, Rocky Mountain Research Station, Utah State University, and University of Nevada, Las Vegas.

Catastrophic wildfire has escalated across the Western U.S. in recent decades with devastating consequences for human communities and native ecosystems. Managing ecosystems to reduce fire risk and prevent loss of ecosystem services requires ecological knowledge on the types of changes that are occurring and the drivers of those changes. A collaborative team developed an approach for evaluating the ongoing changes in climate and vegetation and using that information to determine appropriate fuels and other vegetation management strategies for dryland shrubland and woodland landscapes. We illustrated the approach for a landscape in Dixie National Forest that is experiencing widespread invasion of invasive annual grasses, expansion of pinyon and juniper trees, and extensive wildfires. The group found that large changes had occurred in these ecosystems in recent decades (1980 to 2019) even in the absence of fire.

The perennial grasses and forbs needed to sustain these ecosystems following wildfires and management treatments were decreasing, but the annual forbs and grasses that elevate wildfire spread and degrade ecosystems were increasing. The pinyon and juniper trees that increase woody fuels and cause more severe fires were also increasing. Although most wildfires were likely burning within expected time intervals, the areas burned during a single event were likely larger than in the past and post-fire outcomes had changed with many areas converting to invasive annual grasses. An increase in temperature between 1980-1999 and 2000-2019 resulted in an 11 percent decrease in the areas resilience to wildfire and resistance to the invasive annual grasses.

This work shows that climate warming in Southwest shrublands and woodlands has been associated with changes in vegetation and fuels and decreases in resilience to wildfire and management actions. An approach is provided for managers to quantify the ongoing changes in these ecosystems at management appropriate scales. Climate smart management strategies are suggested to help direct ecosystems into conditions that can decrease fire risk, increase resistance to plant invasions, and reduce vulnerability to climate change.  These include monitoring the ongoing changes in both climate and vegetation to identify where shifts in climate are resulting in decreases in resilience and resistance and loss of climate suitability for native species.

Management actions to maintain or increase perennial grasses and forbs are essential for minimizing expansion of invasive annual grasses and include activities such as postfire restoration and improved livestock management. Woody fuel treatments can reduce the risk of high severity fire and help maintain desirable understory species in shrublands and woodlands. Information on high value resources, such as wildlife habitat, combined with an understanding the relative resilience and resistance of the potential treatment area, can be used to determine the most effective types of treatments and prioritize their locations. Climate smart management strategies such as these can be used to facilitate change that limits transitions to undesirable ecological states and prevents collapse of ecosystem functions and services.