Ecological dynamics
Please refer to group concept F030XC287NV to view the provisional STM.
The amount and nature of the understory vegetation in a forestland is highly responsive of the amount and duration of shade provided by the overstory canopy. Significant changes in kinds and abundance of plants occur as the canopy changes. Some changes occur slowly and gradually as a result of normal changes in tree size and spacing. Other changes occur dramatically and quickly, following intensive harvesting, thinning or fire.
Fire Ecology:
Fire is infrequent on high-elevation sites dominated by Great Basin bristlecone pine. Fire return intervals range from 50 to 200 years. When fires do occur, they are usually small, low-severity surface fires. Individual trees are often struck by lightning but the open tree canopy and sparse understory vegetation restrict the spread of wildfire. Stand dynamics are more influenced by climate and seed dispersal patterns than by fire. Great Basin bristlecone pine, a thin-barked pine, is adapted to survive only low-severity surface fires.
Major Successional Stages of Forest Development:
HERBACEOUS: This forest community is typically not subject to naturally occurring fire. Individual trees are often struck by lightning, but the open tree canopy and sparse understory vegetation restrict the spread of wildfire. In the rare event that the woodland is burned over, the post-burn vegetation is dominated by grasses and forbs under full sunlight.
SHRUB-HERBACEOUS: Herbaceous vegetation and woody shrubs dominate the site. Various amounts of tree seedlings (less than 20 inches in height) may be present up to the point where they are obviously a major component of the vegetatal structure.
SAPLING-POLE: In the absence of disturbance, the tree seedlings develop into saplings (20 inches to 4.5 feet in height). Vegetation consists of grasses, forbs and shrubs in association with tree saplings. Tree cover ranges from 10 to 20 percent.
EARLY MATURE FOREST: The visual aspect and vegetal structure are dominated by bristlecone pine greater than 4.5 feet in height. Tree cover ranges from 20 to 30 percent.
MATURE FOREST: The visual aspect and vegetal structure are dominated by bristlecone pine that have reached or are near maximal heights for the site. Tree heights average approximately 25 feet (20 to 40 feet). Tree canopy cover ranges from 20 to 30 percent.
MATURE-DECADENT FOREST: In the absence of wildfire or other naturally occurring disturbances, the bristlecone pines on this site can become many thousands of years old. This stage is dominated by ancient bristlecone pines and standing snags of dead bristlecone. Tree cover ranges from 20 to 30 percent.
State and transition model
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State 1 submodel, plant communities
State 1
Reference Plant Community
Community 1.1
Reference Plant Community
The reference plant community is dominated by Great Basin bristlecone pine with an open canopy of trees and a sparse understory. Ross's sedge and muttongrass are the principal understory grasses and grasslike plants. Clokey's sage and Spring Mountain goldenbush are common shrubs. The visual aspect and vegetal structure are dominated by bristlecone pine that have reached or are near maximal heights for the site. Tree heights average approximately 25 feet (20 to 40 feet). Average tree spacing is 20 feet and average trees/acre is 110-115. Tree canopy cover ranges from 20 to 30 percent.
Table 5. Ground cover
| Tree foliar cover |
1-30%
|
| Shrub/vine/liana foliar cover |
1-5%
|
| Grass/grasslike foliar cover |
1-2%
|
| Forb foliar cover |
1-2%
|
| Non-vascular plants |
0-1%
|
| Biological crusts |
0-1%
|
| Litter |
5-20%
|
| Surface fragments >0.25" and <=3" |
60-80%
|
| Surface fragments >3" |
5-15%
|
| Bedrock |
0-1%
|
| Water |
0%
|
| Bare ground |
1-20%
|
Table 6. Canopy structure (% cover)
| Height Above Ground (m) |
Tree |
Shrub/Vine |
Grass/
Grasslike |
Forb |
| <0.15 |
1-5% |
1-5% |
0-1% |
0-1% |
| >0.15 <= 0.3 |
1-5% |
1-5% |
1-5% |
1-5% |
| >0.3 <= 0.6 |
1-5% |
1-5% |
– |
– |
| >0.6 <= 1.4 |
1-5% |
1-2% |
– |
– |
| >1.4 <= 4 |
5-15% |
– |
– |
– |
| >4 <= 12 |
15-20% |
– |
– |
– |
| >12 <= 24 |
0-1% |
– |
– |
– |
| >24 <= 37 |
– |
– |
– |
– |
| >37 |
– |
– |
– |
– |
Additional community tables
