Field Work in the Mojave Sky Islands

As the holidays approach, some of us will be decorating our homes with a tree native to mountains of western North America, the White fir (Abies concolor). This species is fairly common throughout the Rockies, Cascades and Sierra Nevada Mountain Ranges. It can also be found in much more unusual locations, including the mountains of the eastern Mojave Desert.

If you’ve been to Hawaii and have seen the unique native plants that grow there, you probably know that isolated islands in the middle of the ocean often harbor unique species and ecosystems. A similar effect happens in the mainland southwestern US, with high mountains ‘islands’ surrounded by an ‘ocean’ of desert. These places have been dubbed sky islands, and harbor unique ecosystems. These ecosystems often contain endemic species, meaning that they can only be found in these isolated areas. Equally interesting, sky islands also often contain disjunct populations and relict species.  Disjunct population is a term used to describe populations of species that occur far outside of their normal range.  A relict species was more common on the landscape in the past, but due to a changing climate it is now restricted to a very small area. 

Three mountain ranges in the eastern Mojave Desert within California are considered sky islands; the Kingston Mountains, The Clark Mountains, and The New York Mountains. These ranges all rise above 7000 ft. and contain ecosystems that exist nowhere else in the surrounding lower elevation desert.  This fall we took a trip to visit these sky islands and assess the disjunct, relict populations of white fir which occur in the mountains.  

The Kingston Mountains, a Mojave Desert sky island

The populations of white fir in the high elevation mountains of Mojave Desert are part of relict ecosystems which supports patches of coastal vegetation, remaining from a wetter past in the west. A number of plants which are more commonly found in the areas of California west of the mountains also have disjunct populations here. These include coffee berry (Rhamnus californica) and Mexican manzanita (Arctostaphylos pungens). These plants and other’s such as narrow leaved yerba santa (Eriodicyton angustifolium) harken back to an era when much larger areas of the southwest looked more similar to the coastal charparral vegetation that we see in California today. 

The main focus of our trip was to scout the white fir populations in the hopes that we can collect seeds next season and to record detailed information on their health. Occurring in these extreme conditions, and living a relatively long life, these trees can provide a great study system to see how climate change is affecting the mountains. A major concern is that climate change will increase the temperature of these areas and literally push the white fir, and the many other unique species that are adapted to this cooler habitat off of the top of the mountain and into oblivion.  

During our trip, we visited all three of these ranges, but due to time constraints were only able to hike to the population in the New York Mountains. Part of the challenge of working in these areas is their remoteness. They occur at the tops of rugged mountains far from any trails or roads. On our day in the New York Mountains we were joined on in the field on that day by Andrew Kaiser of the Mojave National Preserve. After a challenging hike up the steep southern face, we made it to the main ridge. The views were incredible, but as we arrived and spent some time looking, but did not see any of the large and obvious trees. 

After about an hour of searching among the treacherously steep slopes, we finally saw a large white fir crown rising above the granite boulders. We spent the next several hours taking detailed notes, GPS data and photos. In total, we counted 31 trees, the exact number that was recorded by a team who visited the population in the late 70s, which included the late RSABG herbarium curator emeritus Robert Thorne.  This, plus the fact that found plants ranging from a foot tall to 60 feet was an encouraging sign that the population is not in obvious decline. In 2016, we hope to return to this population, along with the populations in the Kingston and Clark mountains, to do more monitoring, and hopefully make a collection of seeds for the RSABG seed bank. 

A young white fir specimen in the New York Mountains is an encouraging sign that the population will persist into the future

Looking up the steep northern face of the New York Mountains at a stand of white fir

 The sky islands of the Mojave are one of the hidden treasures that exist in the California desert. With nowhere to migrate to if conditions change, a warming climate is especially threatening to the plants and animals of these isolated areas. We hope that in the coming field season, we can gather more data on these special places to help to develop a better sense of how climate change will affect the Mojave Desert Mountains.

Sky's the limit: alpine plants on a Sierra Nevada sky island

Botany is addictive.  As a kid growing up near the western foothills of the Sierra Nevada mountain range, I took numerous summer camping trips to the forests where I loved trying to identify every kind of tree and wildflower I saw.  I would religiously consult the plant pictures and descriptions in my copy of T. Storer’s Sierra Nevada Natural History, the classic guide for anyone exploring California's most glamorous mountain range. 

Now as a graduate student in the research department at RSABG I am still fascinated with native plants. I am currently working on a floristic inventory of the Rock Creek drainage in Inyo National Forest on the eastern side of the Sierra Nevada, about 50 air miles southeast of Yosemite National Park.  On a topographic map the upper Rock Creek watershed appears as an eggplant-shaped hollow about 30 sq. miles in area, surrounded by steep granite ridges and peaks, many reaching 12000 feet and higher.  In the course of my research I have found there is little documentation about the biodiversity of the high mountain summits around Rock Creek, which are physically challenging to reach.

Rock Creek, Inyo NF

I'm inspired by the work of botanists whose insatiable curiosity has led them on searches for plants in wild remote places.  Long before before I was born, an accomplished botanist named John Thomas Howell made a challenging climb up a high mountain in the Rock Creek drainage that had no record of previous botanical exploration.  Howell—who earlier in his career had been the first botanist hired on staff at RSABG—described the flat-topped mountain as a “sky island” looming high above Rock Creek Lake.  It had no geographic name, so he called it Mono Mesa.  He originally saw it while on a botanical collecting trip through Mono Pass.  Howell climbed to the top of Mono Mesa in July 1946, collected representative samples of as many different plants as he could find, and shortly thereafter published a list of species.  He found 73 taxa, which he considered an impressive number for a high summit with ¼ sq. mile of land area.  Howell recounted his fascination with the barren yet beautiful landscape he described as a “velvet-textured monotony.”  He wrote that Mono Mesa was unusual, that unlike the surrounding jagged ridge tops it had never been glaciated, never changed by eroding effects of melting and moving ice.

Sky island: Mono Mesa's flat surface visible from the Mono Pass area

Sixty seven years later in summer 2013 I stood at our base camp at Summit Lake near the top of Mono Pass, impressed by the monumental view of Mono Mesa rising into the sky two miles to the north.  I contemplated my quest to resurvey the mesa, which had been many months in planning, preparation and no small measure of uncertainty.  Local folks in the Rock Creek valley had assured me that a day hike to the summit (12260 ft.) was very doable but there seemed no clear consensus on which route was best and no established trail to follow. 

We set out from camp the morning of July 12, a two-person team consisting of myself and RSABG colleague Travis Columbus.   It took us several hours to make our way cautiously along a narrow knife ridge of piled boulders leading up to the mesa edge and after many heart-pounding moments negotiating our way around gigantic boulders and sheer drop-offs we arrived at the summit in early afternoon.  I spent the remainder of the day collecting plant samples, recording GPS data and taking field notes as we surveyed the wide plateau.

Sky pilot (Polemonium eximium) is endemic to the Sierra Nevada

I was struck by the barren expanse of sandy rocky plain, practically devoid of trees and shrubs except for a few small, scraggly whitebark pines (Pinus albicaulis) clinging to the south rim.  A closer inspection revealed an assortment of small colorful plants with cushion- or mat-like growth forms, hugging the ground or sheltering under lichen-covered rocks as if to take refuge from the unforgiving alpine environment.  Plants have to be tough survivors up here.  Many species I happily observed still thriving on Mono Mesa decades after Howell documented them, including Davidson’s penstemon (Penstemon davidsonii), alpine gold (Hulsea algida), dwarf alpine Indian paintbrush (Castilleja nana) and sky pilot (Polemonium eximium): arguably the flashiest most charismatic alpine plant that only grows in the Sierra Nevada.

Alpine gold (Hulsea algida)

My curiosity to resurvey the mesa was especially keen because of the potential impacts of climate change. Warming temperatures are a significant threat to alpine plant communities especially on the highest summits where plants cannot disperse any higher to find cooler microclimates. Perhaps there are species still unknown to science persisting on Mono Mesa and atop other Sierra sky islands where the chance of discovering them is getting slimmer as the climate warms.  It was an unforgettable experience seeing the wonderful flora of Mono Mesa; hopefully my ongoing work to identify the plants I collected there will contribute to understanding life on these magnificent islands in the sky.