(CRAM) For Wetlands User's Manual Version 5.0.2

California Rapid Assessment Method for Wetlands v. 5.0.2 – Chapter 4
Non-native species owe their occurrence in California to the actions of people ever since shortly
before Euro American contact. “Invasive” species are non-native species that tend to dominate
one or more plant layers within an AA. CRAM uses the California Invasive Plant Council (Cal-
IPC) list to determine the invasive status of plants, with augmentation by regional experts.
B. Rationale: The functions of whole-wetland systems are optimized when a rich native flora
dominates the plant community, and when the botanical structure of the wetland is complex in
3-dimensional space, due to species diversity and recruitment, and resulting in suitable habitat
for multiple animal species. Much of the natural microbial, invertebrate, and vertebrate
communities of wetlands are adjusted to the architectural forms, phenologies, detrital materials,
and chemistry of the native vegetation. Furthermore, the physical form of wetlands is partly the
result of interactions between plants and physical processes, especially hydrology. A sudden
change in the dominant species, such as results from plant invasions, can have cascading effects
on whole-system form, structure, and function.
C. Seasonality: This suite of metrics is ideally assessed during the latter third of the growing
season, when all plant layers have developed to their full extent.
D. Field Indicators: The Plant Community Metric is assessed in terms of the similarity between
the dominant species composition of the plant community and what is expected based on
CRAM verification and validation studies, regional botanical surveys, and historical resources.
This metric requires the ability to recognize the most common and abundant plants species of
wetlands. When a CRAM field team lacks the necessary botanical expertise, voucher specimens
will need to be collected using standard plant presses and site documentation. This can greatly
increase the time required to complete a CRAM assessment.
4.4.1.1 Number of Plant Layers Present
The first submetric of the Plant Community Metric is the Number of Plant Layers Present in the
AA. This submetric does not pertain to Vernal Pools or Playas. Plant layers play a large role in
the assessment of the biotic structure attribute. They are distinguished from one another by the
differences in average maximum heights of their co-dominant plant species. For the Other
Depressional Wetlands, plus Estuarine, Lacustrine, and Non-confined Riverine Wetlands a
maximum of five plant layers are recognized by CRAM. For Slope Wetlands and Confined
Riverine Wetlands, a maximum of four layers are recognized. To be counted in CRAM, a layer
must cover at least 5% of the portion of the AA that is suitable for the layer (see Appendix II). This
would be the littoral zone of lakes and depressional wetlands for the one aquatic layer, called
“floating.” The “short,” “medium,” and “tall” layers might be found throughout the non-aquatic
areas of each wetland class, except in areas of exposed bedrock, mudflat, beaches, active point
bars, etc. The “very tall” layer is usually expected to occur along the backshore, except in
forested wetlands.
It is essential that the layers be identified by the actual plant heights (i.e., the approximate
maximum heights) of plant species in the AA, regardless of the growth potential of the species.
For example, in a riverine system a young sapling redwood between 0.5 m and 0.75 m tall would
belong to the “medium” layer, even though in the future the same individual redwood might
belong to the “very tall” layer. Some species might belong to multiple plant layers. For example,
groves of red alders of all different ages and heights might collectively represent all four non-
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