Following is a compilation of life history information for the principal species in all full alliance descriptions in this book. By reviewing these traits and looking at supporting evidence from fire effects tables (Appendix 2 and individual alliance treatments), we can begin to assess different strategies that indicator plants use to sustain them- selves. These plants, as the most characteristic or indicative of each of the vegetation alliances yet described, can provide useful information on what it takes to be a successful species in the state’s current array of vegetation types. In the following table of definitions, we have added a column that shows the number of diagnostic alliance indicator plants associated with the given life history category. In some cases multiple species characterize a vegetation type; for example, Typha angustifolia, T. domingensis, and T. latifolia each characterize the Typha alliance. We briefly summarize some of the relationships in the following paragraphs, but much more work can and should be done to tie the trends and relationships to the species’ current and historic ecological relationships.
Lifeform: Most alliance indicators, as currently understood, are polycarpic perennials. These species persist and can reproduce multiple times over their lives. Vines and lianas are currently not represented as alliance indicators; this is understandable since they are mostly tropical. Some 79 trees, 156 shrubs, and 127 grasses, grass-like and broadleaf herbaceous plants are alliance indicators. Shrubs and herbaceous plants are indicative of the relatively dry climate and unpredictable precipitation regime within our state. Annuals, although common in the California flora, are not well represented as alliance indicators at this time. This may have more to do with the difficulty of using them as vegetation indicators and may be a short-term artifact based on the current state of the art of California vegetation classification.
Leaf Condition: The evergreen strategy is clearly more widely adopted by alliance indicators than either the drought or winter deciduous perennial strategy. Rhizomatous, stoloniferous, and bulbiferous herbs are also relatively common indicators. Leaf and stem succulents are relatively unimportant numerically.
Seed Storage and Longevity: Both transient (short-lived and not-stored) and soil-stored seeds are common strategies, while canopy-stored (e.g., serotinous conifers) seeds are less common but are significant and indicative in many cases of fire tolerance or adaptation. Seed longevity is more heavily weighted to short-duration seeds, but long-duration (mostly soil-stored) seeds are a significant component in the alliance level indicators.
Dispersal Mechanisms: Wind, animal, gravity, and water/hydrological dispersal mechanisms are all significant, while expulsive release or tumbling are much less common. It is notable that animal dispersal involves the highest number of alliance indicators, underscoring the importance of plant/animal interactions in maintaining the largest category of California alliances.
Germination Agents: Germination for the majority of alliance indicators is not assisted by any particular trait or agent. Winter stratification is the most important single agent, suggesting that the temperate climate of California is a powerful influence on these species. Although fewer than the species requiring winter stratification, the species requiring heat or chemical treatment are significant (and may grow more with further study), suggesting the role of fire in maintaining alliances. The number of species requiring inundation also speaks to the importance of short- (e.g., vernal pools) to longer- (e.g., more permanent water bodies) duration water ponding to sustain several alliances.
Asexual Regeneration: Vegetative sprouting is a very important trait in many alliance indicators, although this number is somewhat artificially inflated because of the way the tallies were conducted (e.g., weak sprouters can still be considered as “sprouting from underground structures”).
Fire Tolerance: A large number of alliance indicators that are also dominant are considered fire hardy, although fire-sensitive species are also prevalent. Fire, though a common feature of many vegetation types, is not innately ubiquitous in California’s vegetation. Specific features of many species such as thick epidermis, high sprouting abilities, and flammability, suggest long coexistence with fire. However, a number of species are sensitive to fire and would be expected to decline under certain conditions of fire frequency and intensity. Disturbance-stimulated flowering, a specific trait of fire, flood, and other regularly physically damaged species, is not a strong trait.
In California, the majority of alliance indicators have low recruitment rates. This point suggests that some duration between disturbance events, along with some level of stability and predictability for disturbance and climatic regimes, is important to most of the vegetation alliances in California.
|LIFE FORMS||Includes duration, life form (with modifiers), and leaf condition (From CNPS Inventory)|
|Annual||Grows from seed and reproduces within a single year|
|Annual/Perennial||Variable depending on environment and conditions|
|Monocarpic perennial||Perennial species that dies after fruiting (biennials are included here).|
|Polycarpic perennial||Perennial species that does not die after fruiting.|
|Herb||Lacks above ground woody tissue|
|Shrub||Smaller woody perennials that retain most of their above ground woody tissue and are typically many-stemmed|
|Tree||Larger woody perennials that retail all of their above-ground woody tissue and are typically single-stemmed.|
|Vine||Woody perennials that require external support for growth|
|Evergreen||Retaining leaves for the entire year|
|Drought deciduous||Shedding leaves during drought/dry season|
|Winter deciduous||Shedding leaves during winter/cold season|
|Bulbiferous||Having fleshy underground storage organs (herbs)|
|Rhizomatous||Herbs with underground stems that can produce additional stems, producing populations of “individuals” that result from asexual reproduction.|
|Stoloniferous||Having above-ground runners (stolons) that typically root and produce new plants|
|Leaf succulent||Having thick fleshy leaves (shrubs)|
|Stem succulent||Having thick, fleshy stems and reduced or absent leaves (shrubs)|
|Clonal||Trees or shrubs with underground stems that can produce stems, producing populations of “individuals” that result from asexual reproduction.|
|Canopy stored||Seeds stored above ground in cones (or other structures?)|
|Soil stored||Seeds stored below ground either in seed caches or diffusely distributed|
|Transient||Seeds not stored in seed bank above or below ground|
|SEED LONGEVITY||Length of time that seed remains viable under natural conditions|
|Short||More or less equal to one year or one growing season (may last into a 2nd year in some cases)|
|Medium||> 1 year or season but < 10 years|
|Long||> 10 years|
|MODE OF DISPERSAL|
|Wind||Transported by wind|
|Animal||Transported by animals|
|Gravity||Transported by gravity|
|Water/Hydrological||Transported by water|
|Expulsion from capsule||Seed expelled a significant distance from parent plant when capsule explodes|
|Tumbling||Having morphological characteristics (such as stiff trichomes) that cause the seed to be moved with little wind action (not aloft). Example: Larrea tidentata|
|Chemical||Requiring a chemical agent for germination|
|Heat||Requiring high temperature for germination|
|Inundation||Requiring prolonged submersion in water for germination|
|Scarification||Requiring physical breaking of the seed coat prior to germination|
|Stratification—Winter||Suitable conditions of temperature and/or moisture in winter|
|Stratification—Summer||Suitable conditions of temperature and/or moisture in summer|
|MODE OF SPROUTING|
|Buds on small branches||Sprouting from buds on small above ground branches|
|Buds on large branches or trunks||Sprouting from buds on large above ground branches or trunks|
|Underground structures||Sprouting from underground structures such as lignotubers, rhizomes, roots.|
|SURVIVABILITY OF MATURE PLANTS AFTER FIRE DISTURBANCE||General ability of plants to resist disturbance (fire) due to specific biological or morphological characteristics|
|Fire-sensitive||Plant is likely to be killed by fire of average/moderate intensity|
|Fire-hardy||Plant is likely to survive fire of average/moderate intensity|
|Thin epidermis||Plant has a thin outer layer of tissue|
|Thick epidermis||Plant has a thick outer layer of tissue|
|High flammability||Plant is highly flammable|
|Low flammability||Plant is resistant to fire (firewise or fire retardant plant)|
|No/low sprouter||Plant does not typically resprout after disturbance|
|High sprouter||Plant typically resprouts after disturbance|
|Canopy architecture susceptible||Low, spreading structure|
|Canopy architecture resistant||Tall, narrow structure|
|Yes||Flowering is stimulated by fire or other disturbances|
|No||Flowering is not stimulated by fire or other disturbances|
|KNOWN REPRODUCTIVE RANGE||Age from which a plant becomes sexually reproductive to time sexual reproduction ceases or becomes very low|
|Range (in years) or Unknown|
|Low||A relatively low number of offspring survive to adulthood compared to other similar species|
|Medium||A medium number of offspring survive to adulthood compared to other similar species|
|High||A high number of offspring survive to adulthood compared to other similar species|
|Episodic||Recruitment does not normally occur annually or on other regular cycles|