Ecosystem Overview



             Giant sequoias (Sequoiadendron giganteum) have an important role within the Sierra Nevada ecosystem and their majesty provides an aesthetic and cultural role within society. The trees afford visitors a glimpse at the largest living thing on the planet, including General Sherman, the largest tree on earth. Their natural distribution is limited to the western slope of the Sierra Nevada, in a narrow band of mixed conifer forests between 5,000-8,000 feet elevation. They are contained in 75 groves around the world. Today, there are about 36,000 acres of giant sequoias in the world, and they have been cultivated in Western and Southern Europe, the U.S. Pacific Northwest, Southwestern British Columbia, Southeast Australia, New Zealand, and Central Southern Chile. Still, 27,830 of those global acres lie in the tree’s natural habitat in the southwestern Sierra Nevada mountains





            Giant Sequoia trees have a long history dating back to the Mesozoic Period when their ancestors lived in much of the northern hemisphere. Soon after, more recent ancestors of the giant sequoia were pushed into the Southwestern United States due to changes in the climate. Today, the only native giant sequoia trees are found on the western slopes of the Sierra Nevada. The first time these sequoia trees came into contact with humans was most likely with Native Americans who lived in North America thousands of years ago. These Native Americans preserved the sequoias mostly in their pristine state unlike the Europeans who followed them. After the Europeans discovered the giant sequoia in 1852, they logged them until they ended up destroying about a third of the total amount of sequoias. By 1890 though, preservation of the giant sequoias became important to many including the government. That year the Sequoia, General Grant, and Yosemite National Parks were created protecting many acres of giant sequoia trees. Because these giant sequoias have the potential to live for thousands of years, and many have, the historical state of the giant sequoia has not changed that drastically except for the reduction of acreage due to logging. Because of protection from National parks, the acreage of giant sequoias present in the Sierra Nevada today is likely to continue to thrive as long as human impact and traffic over them is limited. 

General Habitat and Adaptations


            As a result of the dry summers, the species has adapted to frequent or severe fires. In fact, its only method of reproduction requires periodical fires throughout the region, which were commonly caused by lightening strikes before human fire prevention began. Larger trees have thick bark that can withstand high temperature fires, and leaves are typically far above the ground and away from ground fires. The wide trunk and great height keep a natural separation of its leaves from adjacent trees, which protects it from crown fires that could burn from one tree to the next. These adaptations promote photosynthesis and transport of food to the rest of the tree, making them integral to the tree's health

Human Impact

            Humans have impacted Sequoia forests in a variety of ways. From 1800 to 1950, logging devastated the region. During this time period, 34% of the original range of sequoia timber was lost to extraction. Though preservation efforts put an end to this destruction, humans continue to hurt natural sequoia habitats. Walking or driving over tree roots can damage them, and road and building construction in the region decimates the soil. Clearing land can also change the soil moisture in the region, negatively affecting sequoia habitats. "Modification of landforms causes water runoff from rainstorms and snowmelt to concentrate and form gullies, causing soil erosion.

            Furthermore, wetland and stream habitats are negatively affected by leaking sewage. Runoff from nearby parking lots depletes soil of organic matter and alters its structure, devastating the sequoia populations and surrounding habitats. Fire prevention strategies also focus on removing the natural duff layer from the forest surface. This absence reduces the ability of surface soils to hold water and maintain the aeration necessary for root health. The corresponding loss of organically rich topsoil causes big problems for sequoia forests.

            Fire suppression is perhaps the most dangerous issue to sequoia populations. The health of the trees requires frequent, low-intensity fires to burn and clear undergrowth in order to allow new sequoia seedlings to take root. Fire prevention strategies prevent sequoias from regenerating successfully, while allowing competitor species to proliferate. Human intervention also causes dead leaves and branches to build up which leads to larger and more destructive fires. The below graph shows the actual versus desired levels of surface fuel. 






As you can see, surface fuels build up, drastically increasing the severity of fires when they do occur. In addition, far more fires are caused by humans than natural causes. As the below graph depicts, human-caused fires have burned approximately 250,000 acres more than lightening-caused ones. 








            Today, the giant sequoia is recognized as a national treasure and as much as 90% of the population is protected. The best-known groves are found in Yosemite, Sequoia, and Kings Canyon National Parks, which attract tourists from throughout the world. "33 of the 75 natural groves of sequoias are under National Park jurisdiction," and these groves occupy approximately 11, 223 acres of giant sequoia. The National Park Service is dedicated to protecting the groves and individual trees in its care, and intensive forest fire protection provisions exist for all groves in public ownership. In order to recreate historic conditions, the National Park Service now practices controlled burning in order to proliferate the region’s sequoia populations. Still, significant research needs to be done to determine the appropriate number and length of burn days. As you can see from the graphs below, the number of burn days annually has decreased since 1973. Burn days are typically scheduled when the fuel moisture criteria is met. This is because there cannot be a controlled burn on a day in which the forests are extremely dry or else the fire will become too large and too destructive. Therefore, the decreasing amount of days on which this moisture criteria is met makes it difficult to implement controlled burns successfully without them getting out of hand. 





While the area is classified as vulnerable on the International Union for Conservation of Nature Red List 2007, the human impact on giant sequoia groves is luckily not disastrous. The protection and conservation of groves of sequoias has ensured this, but humans still have the capacity to destroy these forests due to the above impacts. If logging, road and building construction, and fire prevention continue to occur, human impact will remain mostly bad, if not ugly. Therefore, it is vital to continue to devise plans for preserving these giant sequoias for the esthetic and scientific purposes we as humans value them for.

Future of the Sequoia

           The future prospects for the sequoia ecosystem are mixed, with indications for modest, managed growth. On the positive side, the National Park Service and the National Forest Service are both working to help expand groves through seedling plantings, controlled burns, and undergrowth clearing. But a variety of threats to continued growth of the groves include uncontrolled burns, disease, infestations and human traffic. By instituting controlled burning instead of outright fire suppression, the National Park Service has made significant strides to improve the welfare of the Sequoia National Forest. In the future, the sequoia population in the region should remain constant through careful monitoring of forest conditions. Hopefully, the future of this ecosystem includes not only the preservation and continual growth of the already protected sequoias, but also the human aided development of new seedlings into full grown trees. Growth and expansion of this ecosystem may be possible but it will take time and human dedication to conservation to achieve this feat. But it is important to note that the limited size of protected areas limits the extent to which these efforts can assure growth of the overall grove population.

            In order to improve human impacts on on this ecosystem, the federal government, through the National Forest Service, National Park Service, and endangered tree species legislation should work with the scientific and conservation communities to develop a single, comprehensive management plan for long-term Sequoia grove survival within and outside protected areas. This comprehensive plan should seek to resolve ongoing concerns, including:

• Ongoing monitoring of growth and loss due to fire, climate, infestation, overuse, and human contamination
• Further studies to examine causes of premature tree death
• Enhanced public education and outreach to improve care and advocacy for the ecosystem
• Increased park and forest surveillance to help avoid accidental wildfires caused by cigarettes, campfires, etc.
• A fire management plan that balances planned, controlled burns with wildfire containment strategy and lost acreage due to wildfires
• Legislation providing stronger protection of this endangered tree species on private and public land outside the protected park and forest areas
• Strict management of recreational human traffic in terms of both volume and areas to assure that the most vulnerable “new growth” areas can expand without interference.
• Fully examine the impact on indigenous wildlife species before implementing ecological restoration treatments.

            By establishing a single comprehensive management plan for the Sequoia National Forest, we can alleviate these issues by setting precedents for the ecosystem’s welfare now and in the future.


           

References

"California, Sequoia Forest Fire, 1995, Photo of the Day, Picture, Photography, Wallpapers - National Geographic." Photography and Photos of the Day - National Geographic. National Geographic. Web. 13 Nov. 2011. <http://photography.nationalgeographic.com/photography/enlarge/sequoia-forest-fire_pod_image.html>. 
Carsey, Eugene. Sequoia Sign. Photograph. Eugene Carsey. Eugene Carsey. Web. 13 Nov. 2011. <http://www.eugenecarsey.com/camp/sequoia/sequoia01sign01.jpg>.
Dunn, Anthony. "Giant Sequoia Groves - Map of the Natural Range of the Giant Sequoia." Sierra Nevada Photos - Home Page. Web. 13 Nov. 2011. <http://www.sierranevadaphotos.com/geography/giant_sequoia/index.asp>.
Harvey, Thomas. “Evolution and History of Giant Sequoia.” Web. 27 Nov. 2011.
           <http://www.fs.fed.us/psw/publications/documents/psw_gtr095/psw_gtr095_harvey
           .pdf>
Hiking in Sequoia National Park. Photograph. Nature-Talk. Nature-Talk. Web. 13 Nov. 2011. <http://nature-talk.com/photos/images/789-    hiking-in-sequoia-national-park.jpg>. 
Parsons, David. “Objects or Ecosystems? Giant Sequoia Management in National Parks.”
            National Park Service, Department of the Interior, nps.gov. Web. 27 Nov. 2011.
            < http://www.nps.gov/seki/naturescience/fic_obj_eco.htm>
Piirto, Douglas. “Giant Sequoia Insect, Disease, and Ecosystem Interactions.” Web. 27
            Nov. 2011. < http://works.bepress.com/dpiirto/12/>
“Sequoiadendron Giganteum.” The IUCN Red List of Threatened Species. Web. 27 Nov.
            2011. < http://www.iucnredlist.org/apps/redlist/details/34023/0>
"Sequoia & Kings Canyon National Park - The Sequoia Ecosystem (U.S. National Park Service)." U.S. National Park Service - Experience Your America. U.S. National Park Service. Web. 13 Nov. 2011. <http://www.nps.gov/seki/historyculture/gfecosystem.htm>. 
"Tunnel Log." Tunnel Log. American Southwest. Web. 13 Nov. 2011. <http://www.americansouthwest.net/california/photographs450/tunnel-log.jpg>. 
United States. Department of Agriculture. Forest Service. Giant Sequoia National Monument. Vol. 1. Giant Sequoia National Monument. United States Department of Agriculture. Web. 13 Nov. 2011. <http://www.fs.fed.us/r5/sequoia/gsnm/deis/Chapter3.pdf>. 
United States. Giant Sequoia National Monument. Sequoia National Forest. Sequoia National Forest. Giant Sequoia National Monument. Web. 13 Nov. 2011. <http://www.fs.fed.us/r5/sequoia/publications/forest-overview2010.pdf>.