By Jim Bishop and Connie Millar
A group of determined investigators trudge upward above the last of the bristlecone pines, climbing toward a summit that will be their workplace for the day. Cold wind urges them to close zippers and turn up collars. At their feet are hardy and beautiful alpine plants, living in a world of less wind and greater warmth than felt by hikers and trees. On the peak they’ll outline plots with string and spend the day identifying the plants, characterizing their abundance and distribution, taking photos, and burying temperature loggers. They’ll pass hours staring at the ground or hunched over windblown data sheets. If thunderstorms don’t shorten the field day much, they should complete the summit by day’s end and return to Crooked Creek Station in the White Mountains with priceless data scribbled on dozens of sheets.
The upper limit that trees reach is imposed by the average temperature of their environment. Above that point there is insufficient warmth during the growing season to allow them to persist, as basic processes of cell construction and growth are too retarded by the low temperatures. A very plausible effect of low temperature on cell development is the slowing of the “molecular motors” that convey materials throughout the cell on the cytoskeletal framework, as these are critically dependent on thermal energy for their motion.
Yet alpine plants do grow at elevations above the trees. Their main trick is to remain low in stature, taking advantage of solar heating and minimizing airflow cooling to achieve sufficient warmth for growth. Many alpine plants avoid the worst of winter’s bitter cold under the snowpack. The alpine flora prevails in microclimates of sufficient warmth and shelter, where cold air and soil keeps trees at bay. It is a very climate-sensitive ecosystem, vulnerable to the ascent of trees, the loss of habitat with upward migration, and the presence of snowpack. For the most part alpine areas are undisturbed by human influence. Worldwide, alpine zones span latitudes from polar to tropical, elevations from a few hundred meters to over 5,000 meters, and maritime as well as continental climates. They are ideal places to examine the effects of climate change on living things.
An international program to better observe the impacts of climate change on alpine flora and its diversity was born at the University of Vienna: The GLobal Observation Research Initiative in Alpine environments (GLORIA). In 2004, GLORIA was brought to the White Mountains and the central Sierra Nevada by Connie Millar of the USFS Pacific Southwest Research Station and her colleagues, making them the first sites established in the western hemisphere.
The basic GLORIA protocol involves carefully observing plant species, their coverage, and their distribution in the top ten meters of each alpine peak. The survey also incorporates temperature sensors buried ten centimeters deep capable of recording data for years, as well as extensive photographic documentation of the plants and the survey system. Presently seven summits in the White Mountains are surveyed every five years. In fact, the White Mountains have been deemed a GLORIA “world master site.”
White Mountain Research Center, part of the 39-reserve UC Natural Reserve System, is key to making the White Mountains GLORIA program successful. WMRC-related studies in alpine ecology, climate, and geomorphology supplement the GLORIA alpine plant surveys. Such studies include insects, a butterfly count, periglacial processes, detailed temperature observations over the terrain, mapping of upper treelines and shrublines, forest demography, and studies on the effects of climate on mountain mammals like pika and marmot. The overlap between field station research and GLORIA study findings offers great potential for mutually beneficial science collaborations.
Two important additions to the GLORIA methodology developed in the White Mountains are now part of the international protocol. It was realized early on that estimates of plant cover in the large survey plots were inaccurate, and that the quantitative measures in the quadrat plots covered too small an area. Thus a plot ten meters on each side was developed that contains 400 survey points on a half-meter grid. This type of plot yields good quantitative measures over a larger and more representative area. Second, while the summit plots are important, knowing more about the distribution of plants below the summits is essential to better interpret GLORIA observations. This information also helps to quantify shifts in plant population distributions. In addition to the plot developed above, the GLORIA team designed a series of “downslope surveys” on five of the slopes in the White Mountains. At each 25-meter step below a summit, a 100-meter belt transect is laid out along a contour. This lower-elevation transect duplicates the area and sample point distribution of the ten meter-by-ten-meter plots. Downslope surveys span the elevation range from the summit of White Mountain down into the bristlecone pine woodland and sagebrush shrublands.
One set of White Mountain summits has now been resurveyed at five and ten years, and the other set at five years (the ten-year resurvey there this summer). Physical climate trends (such as in temperature or humidity) emerge on decadal timescales. But even short-term GLORIA results have proven interesting. They confirm the replicability of the survey protocol, with resurveys showing essentially the same species richness–an expected result because alpine plants are predominantly long-lived perennials. They also reflect some of the short-term changes that overlay long-term trends, such as fluctuations in the occurrence of annual plants and some shrub mortality in low-snow winters. We may well uncover some ecological surprises with our five-year resurveys.