Researching the ancient bristlecone pines with Google Earth
— John Muir
Since the days of Charles Darwin, biologists have struggled with ways to represent our planet's incredible biological diversity on maps that convey both meaningful information and a realistic sense of scale. In recent years, this challenge has morphed into a search for mapping platforms that are available to help educate the general public, are easily accessible to both novice and established scientists, and are powerful enough to track and display biological data. Our research focuses on the population ecology of ancient bristlecone pine trees in California's White Mountain range, and we have found that Google Earth is an important tool for both expediting the everyday process of fieldwork and for educating the public about our projects. Since 2004, Google Earth has made it much easier for our team to share spatial data, to quickly view this data overlaid on aerial imagery, and has helped us discover key ecological patterns in the bristlecone pine forests.
The White Mountains of eastern California receive less attention and fewer visitors than the nearby High Sierra Range, yet they are similarly spectacular mountains capped by high peaks over 14,000 feet in elevation. Only a few dirt roads cross this surprisingly rugged terrain, where the rolling, sagebrush covered hills are populated with abundant wildflowers and where the valleys support herds of bighorn sheep. This environment is home to Earth's most ancient trees, the bristlecone pines (Pinus longaeva), and is also the site of North America's highest elevation research station, the University of California's White Mountain Research Station.
In 1953, several trees over 4500 years old were discovered in the "Methuselah Grove" area by biologist Edmund Schulman, yet older trees probably exist undiscovered throughout the range. For many scientists, the most interesting attribute of the bristlecone pines is not their extreme age, but the persistence of their dead wood. Due to slow growth in a dry, high elevation mountain range, bristlecone wood is extremely dense and filled with resin, and can thus remain un-decomposed on the ground for up to 10,000 years after a tree has died. For over 50 years, researchers from the University of Arizona's Laboratory of Tree-Ring Researchh and others have used the bristlecone tree-ring record as an important tool in studying past and present climatic changes. In 2004, we began a project (based out of the UC Santa Cruz Department of Ecology and Evolutionary Biology) to better understand the population ecology of Bristlecone pines. This project specifically seeks to examine how certain ancient bristlecone groves have grown or shrunk over the last several millennia, and how these populations may react to a changing climate. To this end, we are studying many different bristlecone groves across the White Mountain range, including both old and young trees, as well as examining aspects of cone production and wood development.
One of the greatest challenges of conducting scientific field research in a rugged mountain environment is locating sites of interest, figuring out how to get there, and communicating this information to a team of people. Before the Google Earth imagery for the White Mountains was updated, obtaining aerial imagery that clearly showed individual bristlecone pine trees for a large area was difficult and expensive. However, with the updated Google Earth imagery, each tree can be distinguished from others, the major rock types are clearly identifiable, and it is easy to tell whether the trees are located in sparse or dense groves.
How they did it
Google Earth has become invaluable for our research on several levels. Initially, we used it as a tool to view the range of these trees and to examine characteristics of different stands before hiking out into the field. Using the Google Earth polygon feature, we drew boundaries around groups of trees that were obviously large bristlecone or limber pine trees as opposed to smaller pinyon pines or bushes of mountain mahogany (see example video). To our knowledge, this is the first complete map produced of bristlecone stands in the White Mountains. Immediately, some important overall patterns emerged, such as the higher densities of trees on north-facing slopes and the locations of the rare stands that were growing on quartzite or granitic substrates as opposed to the preferred dolomite. This preliminary mapping has helped us identify promising field sites that are within a day's hike from the nearest road.
As our project grew, we began to use Google Earth on a daily basis during the field season. Our basic strategy is to keep a "master" KML file of all points or paths that we are tracking, including thousands of individual trees, that can be accessed by any member of our team or other individual at the research station. A recent improvement has been to link each point to a photograph of the tree for easy identification. To do this, we first create a text file with a list of tree names, GPS coordinates, picture names, and the data associated with each tree (such as tree age, number of cones, etc). We then use a PHP script that creates a KML file with placemarks at the location of each tree; the bubble for each placemark contains a photograph and the data associated with that tree.
In the morning before heading out into the field, we might use this master KML file to print out a map of survey points that represent one day's work for several people while at the same time uploading the coordinates of a different transect onto GPS units for a separate team. In the evening, any new data collected can be downloaded and entered into this KML so that we can plan the next day's work.
Laying out transects
One perplexing aspect of bristlecone pine biology is that there are very few young trees within the groves of ancient and dead trees. Bristlecone seeds may germinate and survive only about 1 year out of every 50 years, and this might only happen in certain areas. Therefore, part of our project involves "walking transects" through bristlecone forests of different elevations, slopes, and substrates, and measuring all small trees within 20 meters of where the observer is walking. This method of sampling young trees will help us determine the conditions that are required for bristlecone germination and survival.
For this part of our project, we first used Google Earth to identify promising areas. The video below shows an example of a transect at an elevation of 10,400 to 10,700 feet, crossing both dolomite and granite rock-types (other transects were laid out at different elevations, slopes, and rock types). We measured this path to be about a mile on Google Earth, which is approximately the distance our team could cover over an 8-hour day. Before hiking out to this area, we first examined this path using the Google Earth tilt feature to ensure that it did not cross any areas of loose dolomite that were too steep for safety, we also printed out several views of the aerial photographs so that different team members could locate the area. We then saved the file as a KML and used MacGPS Pro to export this path to several Garmin GPS units. In the field, we were able to roughly follow this path on the GPS units while searching for and measuring all small trees within 20 meters of the centerline. During the day's data collection, we recorded the point location of each tree and used the tracking feature on the GPS to record the actual transect we walked (which has small variations from the one laid out on Google Earth). Upon returning from the day's hike, we uploaded the actual path walked straight into Google Earth and used our PHP script to link the placemarks with photographs and data. As a result, we can click on each placemark to get an image of the tree and see the data associated with it (e.g., estimated age, height, diameter at base, and reproductive status). Therefore, if we want to return to a particular tree on this transect, any member of the team could click on the point, get a picture of the tree and return to that location.
Finding Isolated Trees
Another part of our project involves examining the growth patterns and cone production of trees that are growing at least 50 meters away from all other bristlecones as opposed to those located in dense groves. We first used Google Earth to find what appeared to be isolated trees and then to measure the distance between these trees and others. These trees are tracked in our master KML file, and linked to pictures and data in our online database.
Keeping track of individual trees within a stand
A core part of our project involves aging a set of several hundred living and dead trees within a stand. This requires us to document several hundred points within a small area, and keep each point associated with a unique number and identifying photograph. As we continue surveying each area, the number of points increases daily. We keep a list of points in our master KML file and similarly have each point linked to a picture on our online database. If a question regarding the data or age of a particular tree comes up, we can click on the point to get an image of the tree, upload that point to our GPS, and return to the site.
We created a KML with several different types of information for other scientists, educators, and the general public.The first section, labeled "For Travelers", has placemarks over key visitor sites such the campground and visitors center. The second section, "Learn About the Bristlecone Pine", is an educational tour of the bristlecone ecosystem. Here, interested parties can learn about the discovery of bristlecone pines, the science of dendrochronology, examine differences between bristlecone groves, and explore the upper tree line. This is a good example of how a KML file can be used to transmit a variety of information about the natural history of particular species. The third section, "A Week of Field Research" details a week's worth of fieldwork with our team and demonstrates how Google Earth is critical to our everyday field operations. Here, we provide layers that contain links to many pictures of our trees, show a sample vegetation transect, and provide an outline of the range of bristlecone pines across California, Nevada, and Utah. Finally, the last section is about the White Mountain Research Station, users can explore the four different substations and find links to some of the many projects based here.
For our team, Google Earth has made the process of daily fieldwork much easier, and enables us to keep track of a large amount of spatial data in a way that is accessible to many different people. Here are a few lessons that we've learned:
- Use many different levels of folders to organize your data. If you have hundreds of points, paths and polygons to keep track of, this will help keep everything organized and will keep the scroll bar in the display window short when you expand folders.
- Import custom icons to mark points that are in close proximity to each other if the standard Google Earth icons are too large and appear crowded.
- Google Earth Pro has great features like the ability to draw polygons and import shapefiles, but the free version can do many of the things described above as well.
- Explore 3rd party programs that import and export KML files. Both MacGPS Pro and KMLer are simple and inexpensive programs that have helped us manage data, but there are many, many others.
- Don't be afraid to mark a couple of points, save them as a KML and email the file to colleagues when trying to describe field locations.
In summary, if you are new to using computer-based mapping programs, then you won't find an easier method of managing and sharing your spatial data. Alternatively, for those that are familiar with more traditional GIS platforms, I recommend trying Google Earth as a way to expedite displaying and sharing your data.
Google Earth was invaluable for our research and used on a daily basis. The advantage of using Google Earth was the ease of use by different people, including undergraduate students and volunteers. As well, using KML files gave the team the ability to trade data easily between Mac and PC operating systems. They also had the flexibility to quickly print out maps, photos, or transfer the constantly growing sets of waypoints to and from different GPS units.
The Bristlecone Pine Research KML lets the public explore the White Mountains and these unique trees.
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