 * Critical Finding * ECOSYSTEMS * INSECT SPECIES FOUND ONLY IN THE SIERRA ANIMALS * Land Ownership and Reserve Allocation in the Sierra Nevada The Sierra Nevada of the Future
CURRENT PAGE: 
 
|
|
* Ecosystems
Ecosystem refers to the collective entity formed by the interaction of organisms (e.g., plants
and animals) with each other and with their physical environment (e.g., soil, water,
weather) at a particular location. SNEP considers people, when they are present,
as part of ecosystems. Ecosystems exist at many, potentially overlapping, scales, from
a rotting log to the entire Sierra Nevada; they all have three fundamental attributes.
Components
are the kinds and numbers of organisms (biodiversity of genes, individuals, populations,
species, and groups of species) and physical elements (soil, rock, water) that make
up the ecosystemthe pieces. Trees and wildlife are important to Sierran ecosystems but equally important are the myriad less visable or unseen organisms, such as insects,
fungi, and bacteria. Structures
are the spatial distributions of the componentsthe way the ecosystem pieces are arranged
at a location and time in the ecosystem. Plant communities, such as the mixed conifer
forest, and forest structure, such as old-growth stands, are important examples of ecosystem structure. Processes
or functions
refer to the flow or cycling of energy, materials, and nutrients among the components
over space and through time. Processes are the work of the ecosystem; they contribute
to changes in the components and the structure of the ecosystem. Ecosystems are linked to one another, so that changes in components, structure, and function in one
ecosystem may have consequences in contiguous and noncontiguous ecosystems. The following numbers of known terrestrial endemic insect species are found in each of the major river basins in the SNEP study area. (From volume II, chapter 26)
Eagle Lake 0 Honey Lake 0 Feather 2 Upper Sacramento 0 Yuba 1 Truckee 7 American 0 Carson 2 Cosumnes 0 Mokelumne 4 Walker 2 Stanislaus 0 Calaveras 0 Mono Basin 6 Tuolumne 7 Owens 17 Merced 0 San Joaquin 3 Kings 1 Kaweah 3 Kern 3 Tule 1 Caliente 2 Mojave 0 Animals
About 400 species of terrestrial vertebrates (including mammals, birds, reptiles,
and amphibians) use the Sierra Nevada, although only a fraction are restricted to
the range. Animals that live in the Sierra Nevada depend greatly on the distribution
and quality of vegetation for their habitat and food needs. Many native Sierran species are
adapted to habitats maintained by the precontact fire regime (the regime that prevailed
before non-Indian settlement of the area). Although only a handful of species require late successional habitats, many more depend on the presence of large, old trees,
snags, and logs in Sierran woodland and forest communities for some part of their
life cycle. Late successional and riparian forests are important habitats to wildlife,
as are the low-elevation foothill woodland types. In the latter zone especially, conversion
of habitat and loss of ecological function have dramatically altered the suite of
species that flourished in these communities. A common and important pattern for
Sierran birds is their migratory patterns up and down slopes, following seasons. When
a specific habitat needed for completion of a critical life stage (e.g., foothills
for breeding) is disrupted, species may be put at risk even if they are able to use
alternative habitat for other needs. 
 
|