Wednesday
Apr052017

CNLM's JBLM fire monitoring yields data for species conservation

Prescribed fire at Training Area 14 (Photo Credit: Adam Martin)

It is important to monitor the effects of our restoration actions to inform future management. This is certainly true with prescribed fire, and over the last two burn seasons, the Center for Natural Lands Management (CNLM), Joint Base Lewis McChord (JBLM), and partners have tracked burning conditions and outcomes. Prescribed fire is fundamental to prairie management and restoration on Joint Base Lewis-McChord (JBLM), which has one of the largest and most active burn programs in the Pacific Northwest. Importantly, restoration on JBLM is supporting recovery efforts of the streaked horned lark (Eremophila alpestris strigata), Taylor’s checkerspot (Euphdryas editha taylori), and Mazama pocket gopher (Thomomys mazama). While burn objectives evolve and adapt, initial restoration typically includes killing Scotch broom and creating bare ground for that can be seeded with native species, and therefore hotter burn temperatures are often desired. Burn objectives can shift from creating habitat to maintaining habitat after several years of restoration. Thus, prudent management necessitates understanding the variability of fire effects across weather and fuel conditions, as well as fire’s role in shaping prairie communities. This is where CNLM’s JBLM fire effects monitoring team comes in. 

Weather station set up in preparation for fire effects monitoring at Training Area 15; meanwhile, paratroopers drop into Training Area 14 across the road (Photo Credit: Kathryn Hill)

Fire effects monitoring has yielded important insights into restoration activities and objectives as well as enhanced habitat for these species. One thing the team looked at was how thatch presence moderated soil heating. Burning when air temperature was higher resulted in hotter surface burn temperatures, especially in the drought year of 2015. However, burn temperatures at 2 cm underground were higher only when very little thatch was present; this soil heating likely arises from exposed Scotch broom detritus or other organic matter burning directly on the soil surface when insulating thatch is not abundant. Diapausing Taylor’s checkerspot larvae are likely to be at or under the soil surface during the summer burn season and thus may be more likely to survive a fire under burn intervals of at least three years, which allows for moderate thatch accumulation.

The team returned in spring 2016 to conduct post-burn vegetation surveys of the 2015 burns and found that hotter burn temperatures had resulted in higher cover of exotic perennial forbs, somewhat lower cover of natives, and a slightly shorter and less diverse height structure. While lower vegetation heights can benefit streaked horned lark, overall structural diversity is beneficial for butterflies, supporting the idea that burn objectives for these species will differ. These burns occurred in a drought year, and results will vary when burning in years with a more ‘normal’ precipitation pattern. This spring, we will return to the 2016 burns to survey vegetation response.

In regards to Mazama pocket gopher occupancy, fire appeared to have a small negative impact in just-burned areas, but by summer, occupancy levels had returned. This suggests that while burning can have a marginal negative effect on gophers in the fall (especially in drought years), the long-term effect on habitat for the gopher is positive. We will begin to examine whether gophers also respond to different burn temperatures as we gather more data and amass a multi-year dataset of fire conditions and effects, vegetation response, and gopher occupancy.

Measuring pre-burn fuel conditions before a prescribed fire at Training Area 15 (Photo Credit: Kathryn Hill)