Last week, the Las Vegas BLM, Henderson USGS, and Nevada Conservation Corps teams from central NV gathered to conduct an experiment on seeding methods for the Burned Areas project. They ended up being short-handed one day, so for the first time in quite a while, I got to go out and do some field work! Outdoor work in the desert during the summer may sound like torture to many, but that day I rediscovered the joys of working outside and being immersed in one’s ecosystem of study.
Sunrise in the Las Vegas Valley.
Besides, desert conservationists are well-versed in the art of beating the heat. In the warm desert, doing fieldwork in the summer means starting at the witching hour and finishing up by noon. We set out for Red Rock Canyon National Conservation Area well before dawn, and set up our supplies under cover of darkness. Our task was to complete a few more plots for the diversionary seed aspect of the Burned Areas project. The lack of palatable vegetation most of the year makes granivory – seed predation – an important diet adaptation. In the Mojave, the chief granivores are harvester ants and rodents, such as pocket mice and kangaroo rats. I understand that seeds are an important part of these animals’ diets, but their caching efforts can throw a huge bone in desert restoration efforts! Previous studies in the Mojave have found that granivores can thieve substantial proportions of propagules from seeded disturbed sites. The diversionary seeding was an effort to distract them from the native seed that we want to keep in place.
Seeds of Joshua tree (Yucca brevifolia), carefully measured for our study plots.
Seeds of Joshua trees, white bursage, and creosote bush, all mixed up with millet and ready for broadcasting!
We mixed small portions of Yucca brevifolia, Ambrosia dumosa, and Larrea tridentata with several ounces of millet seed. The millet seed is more nutritious, and thus more attractive, for granivores. Millet is also not adapted to the Mojave’s hot, dry climate, eliminating the danger of germination of thousands of non-native seedlings. The idea is that any would-be rodent seed thieves would fill up on millet, and then be too stuffed to bother with the native seed. In conjunction with the diversionary seeding efforts, USGS wildlife biologists, along with several volunteers, conducted trapping surveys to gain an understanding of what rodent species were active in the project area.
After weighing out pounds of millet and mixing in carefully calculated quantities of the native seed, my crewmate and I trekked out to our sites. As the sun crested the ridge to the east, it burnished the conservation area’s namesake mountains into a deep crimson. The blue yucca made a lovely contrast with the rocks. Slowly, the air warmed, but a light breeze kept the morning air pleasant as we flagged and hand-seeded our plots.
Sunrise at Red Rocks Canyon NCA.
A pin flag amidst Bromus madritensis and Schismus arabicus, two invasive annual grasses that are major problems in the southwest. These grasses artificially increase the fuel load and create continuity between shrubs in an otherwise sparsely vegetated landscape.
The scenery would have been perfect if not for the haunting reminders of the fires of a decade ago. The difference in plant communities between burned and unburned areas was incredibly stark, with far fewer perennial shrubs – mainly burroweed (Gutierrezia), brittlebush (Encelia) and desert globemallow (Sphaeralcea ambigua) – growing in the disturbed areas. Bromus and Schismus carpeted our sites, and twisted stumps of dead Mojave yucca, some still blackened, dotted the landscape like desecrated statues.
Mojave yucca (Yucca schidigera) that has re-sprouted after fire. It took 12 years…but it is re-sprouting nonetheless!
At the base of many, however, emerged the new green spikes of a re-sprouting individual. The sight of these little green spears reminded me that despite the vulnerability of this ecosystem to fire, tolerance to harsh conditions has always been the name of the game here, and that many desert plants are more resilient than one might think.
Due to my office schedule and the blazing summer heat, I hadn’t had much opportunity to venture out into the Mojave over the last few months. Admittedly, since the annuals died back and the shrubs went to seed, there wasn’t as much draw for me to go outdoors as there was in the spring! However, while out in the field I was pleased to see the desert marigold (Baileya multiradiata) still going strong in the anthesis department. And to be fair, just because a plant is past flower certainly doesn’t mean that it is of no interest! Several species were still loaded down with seeds. We found plenty of desert wishbone-bushes that were bursting with cured achenes, and many creosote bushes were still covered with their iconic downey schizocarps. While I’ve learned more information that I ever thought I could about desert plants, from their phenology to palatability to seed dormancy, even the most well-written scientific paper is no substitute for getting out in the field and learning about these species hands-on.
Larrea tridentata, the iconic creosote bush, chock-full of ripe seeds.
Baileya multiradiata, a year-round bloomer in the Mojave Desert.
Monsoon season is in full swing here in the Desert Southwest. For the last week, the morning sun has been blocked from delivering his usual greeting at dawn by thick, blue-grey thunderclouds. On such mornings, the mountains are dyed a deep indigo, and the smell of creosote is thick in the air. Every Vegas Local’s commute is focused on the same goal: to make it to the office, or home, or wherever, before the rain comes down and the flash floods ensue. I for one am grateful for the reprieve from blistering heat and endless sunshine, and even more so for the promise the rain brings – that there is a second bloom happening further south! I hope that I will be able to see the spiderling, devil’s claw, and agave bloom in the Sonoran before the second dry spell of autumn comes along.
