Bobcat Fire Burn Scar Update: 281 Days Post-Fire
Updated: Jun 27, 2021
Revisiting the hits: sagebrush & piñon pines
Seedlings of sagebrush (Artemisia tridentata) in the Bobcat Fire burn scar
NEWSFLASH: WE HAVE SAGEBRUSH SEEDLINGS!!!!
Everything I read about the fire ecology of sagebrush led me to believe that it would be decades before we saw sagebrush again. Sagebrush is an obligate reseeder, meaning that the plant is completely killed by fire, there is no surviving bank of seeds and the work of re-establishing it is done by birds, who bring in seed from outside of the burn scar. I wrote about Sagebrush's role on our ranch in Issue #6 of The Obligate Resprouter back in December 2020.
Sagebrush patch in the burn scar of the 2010 Largo Vista fire across the street from our ranch.
To investigate sagebrush re-establishment I visited the burn scar of the 2010 Largo Vista fire over the winter. In a 40 minute hike through Tucker oaks that had resprouted to nearly cover their skeletons and barkless toppled piñon snags, I found only one small patch of sagebrush. At the time, I took this as confirmation of the previously mentioned bad news about the time required for sagebrush reestablishment. But now that I see new seedlings appearing on the ranch, I'm thinking my interpretation was incorrect. On much of the ranch, the fire burned in a patchwork, turning large swaths to moonscape but also leaving strips and pockets of chaparral and forest completely intact. There is no part of our burn scar that is more than say 1/4 mile from an unburned sagebrush plant that can provide seeds. In this context, these seedling sightings are not all that surprising.
Last year's dried flowers share space with this year's developing stalks on a mature sagebrush outside the burned area.
But what about the 10 year old Largo Vista Fire burn scar? Why the dearth of sagebrush there? I suspect the answer is that it wasn't there in the first place. Although right across the street, it's also on the other side of the fault line. The North American plate is quite a bit higher than the Pacific plate at this part of Big Pines Hwy, by about 100 feet. And it just so happens that here, for sagebrush, 100 feet of elevation makes all the difference. If I hike up the hill toward Piñon Ridge until I'm level with the land across the street, I'm looking down onto chaparral but not standing in it. That higher elevation is dominated by oaks and piñons and no chaparral shrubs with the exception of an occasional mountain mahogany or spindly buckwheat.
A piñon pine sapling emerging from the protection of a dormant desert almond shrub outside the burned area. I wrote about piñon pines in Issue #7 of The Obligate Resprouter in December 2020.
The reason for my near obsession with sagebrush reestablishment is the role that it plays in supporting baby piñons. Outside of the burn scar I see tiny new piñons peaking out from under a fallen branch or reaching up from the inside of a mature sagebrush plant, but never out in the open. The need for protected nurseries is one of the factors contributing to the slow regrowth of piñon forests after fire. In our burned forest, for example, the snags have yet to fall and the ground is almost entirely bare. While they are still upright, they attract birds, accelerating the repopulation of obligate reseeders. This is the part of the story where we talk about temporary type conversion, in which the forest is temporarily replaced by scrubland that can serve as a nursery for the regrowth of the pines. But now that I'm observing the role that even small differences in elevation play, I'm starting to wonder if we will see that play out. Most of our burned piñon forest is above the "sagebrush line," at elevations equal to or higher than the Largo Vista scar. In these forests, maybe fallen snags and resprouting Tucker oaks will play a larger maternal role and we won't ever see sagebrush. Why would it grow there now, if it didn't choose to grow there in the past? At elevations near the transition from chaparral to forest, sagebrush grows contentidly amongst the pines, so the presence of the trees doesn't explain the lack of sagebrush.
Our piñons have released their pollen and are sending out fresh tips.
Piñon seeds are planted by jays who spend time on the edge of forests, perhaps for easy access to good caching sites. Thanks to their good judgement, the forest naturally expands its footprint rather than becoming increasingly dense. If you are an evangelical supporter of the sagebrush sea at the exclusion of all other ecotypes, you might call this "conifer encroachment." I wonder the extent to which the irregular shape of our burn scar might be an advantage for piñon repopulation. There's a lot of perimeter for the jays to work. When I checked the 10-year-old burn scar across the street over the winter, I didn't see any piñon seedlings. But I hiked the interior of the oval burn scar. I should have hiked the perimeter instead. I'll get back up there once it cools off and report what I see.
Despite the dry conditions, our surviving piñons are performing their seasonal tasks. They have released their pollen and are sending out bunches of fresh needles from their tips. About half of them are loaded with green cones the size of a child's fist, mostly on top. Even Big Mamma made a few cones. The only year we took a substantial harvest for storage was 2016, and looking back I wonder if that might have been a bumper crop year, which occur every 4 - 7 years. With so few remaining trees, it's difficult to judge whether it looks like a good year or a poor year, but I think it looks fair. Within days of the cones opening, they will be completely stripped of their viable seeds, over 50 at a time stuffed into the throat of each jay. They will meet up in the caching grounds and dump their harvest, working wing to wing to put them into the ground like farmers planting a field. Some of those seeds will be forgotten, and some of those will germinate, and some of those will be lucky enough to be protected from wind and trampling by a shrub, rock or fallen branch and if I live to be 100 I will get to see those trees grow to almost my height.
Current status of cones on a piñon near the barn. I like to look up at the cones and imagine picking out the seed that will become a tree.
I'm not sure why it only occurred to me this week that the post-fire plant succession playing out here might not follow the tidy narratives of my thus far elementary fire ecology studies, but instead be idiosyncratic even within the ranch's boundary. Of course that's the way it will be. After 281 days of studying and observing, it has finally hit me that this journey is like every other journey of developing expertise. I've been on a few in my almost 50 years: semiconductor physics, goat nutrition and husbandry, cheese making chemistry and practice. For me, each arc of learning lasts about 10 years, after which I feel like I know mostly enough for my purposes, and the learning doesn't end but I stop working at it so deliberately. First I learn the major threads, the broadly applicable stories. This is how I begin to develop intuition and an understanding of which questions to ask, what things to watch the most carefully. I learn how to describe what I see as examples of or deviations from those shared narratives. Eventually I come to expect, anticipate, and finally predict those deviations at least as often as the textbook examples. This learning journey is turning out to be similar to the others.
Even though I won't live long enough to see a mature forest of trees where the snags stand today, I will get to see the miracle of her maternity. I will be her midwife, her student, and her most enthusiastic cheerleader.
You can see more of my observations along with those of others in this part of the Bobcat Fire burn scar by searching zip code 93563 at https://www.inaturalist.org.