(CRAM) For Wetlands User's Manual Version 5.0.2

California Rapid Assessment Method for Wetlands v. 5.0.2 – Chapter 4
4.3.1.2 Patch Type Definitions for Vernal Pool Systems
Animal mounds and burrows. Many vertebrates make mounds or holes as a consequence of
their foraging, denning, predation, or other behaviors. The resulting soil disturbance
helps to redistribute soil nutrients and thus it influences plant species composition and
abundance. To be considered a patch type there should be evidence that a population
of burrowing animals has occupied the Assessment Area. A single burrow or mound
does not constitute a patch.
Bare Soil. Areas at least 1m2 that lack at least 5% cover of vegetation are considered bare
ground. Patches of bare ground serve as resting sites for passerine birds and foraging
sites for predators.
Drainage Branches. Many vernal pool systems consist of low-gradient drainage networks
with multiple pathways or branches for surface water flow that provide alternative
ways to naturally fill and drain vernal pools.
Mima-mounds. These are regularly spaced, elliptical mounds of soil ranging in height from
about 50 cm to 2 m. They provide upland transition zones around vernal pools,
perches for ground-dwelling birds, burrowing habitat for small mammals, etc.
Hummocks. In vernal pool systems, hummocks are small mounds created by plants, such as
bunch grasses, usually along the upland margins of vernal pools or in the adjacent
upland matrix. They are usually less than 10 cm high and less than 10 cm in diameter.
Vernal Pool Types. The component pools of any given vernal pool system tend to vary in
size and shape in ways that affect the communities of plants and animals they support.
Large and Small Pools. There are no fixed, numerical criteria to identify large and small
pools. Within many vernal pool systems, some pools are obviously larger than others.
For any AA, the cutoff in size between large and small pools must result in three
replicates of each.
Simply- and Complexly-shaped Pools. Within many systems, some pools will be round
in plan form (i.e., simply-shaped), whereas others will be much longer than wide or
very irregularly shaped, with variegated shorelines.
Pool Clusters. A cluster of vernal pools is a set of three or more pools that are
hydrologically interconnected by swales or other surface flow pathways, with each pool
being no more than 10 m away from another pool in the set.
Soil cracks. Repeated wetting and drying of fine grain soil that typifies some vernal pools
can cause the soil to crack and form fissures that provide habitat for amphibians and
macroinvertebrates. Cracks must be a minimum of 1 inch deep to qualify.
Swale Types. Vernal pool systems consist of vernal pools, vernal swales (and other pathways
of surface water flow), subsurface flow, and an upland matrix that surrounds each pool
and swale. A swale is an elongate feature, slightly concave in cross-section, that
conveys surface flow but lacks a well-defined channel. Swales vary in width and length.
Large and Small Swales. There are no fixed, numerical criteria to identify large and
small pools. Within many vernal pool systems, some swales are obviously larger than
others. For any AA, the cutoff in size between large and small pools must result in
three replicates of each.
69