PLS 147 Lecture 4: Vernal Pools
Vernal Pool
● seasonal (ephemeral) wetland underlain with a layer impermeable to water
○ seasonable bc it's over a layer of soil that doesn't allow the water to percolate
away
○ standing water until it dries away
○ vernal: Latin for "springtime"
● almost everything in central valley is non-native except vernal pools
● can be surrounded by grassland or lodgepole pine forest, or blue oak woodland, or
sagebrush steppe, or by coastal scrub, or prairie aka anywhere!
○ not really about overall climate but more about these temporary pools
● characteristics of Med climates bc wet winter to build pool and dry in summer so pool
disappears (or else it would just be a wetland)
● claypan, hardpan, or otherwise impermeable layer (aquitard)
○ this flat layer makes the water table build up when it rains
○ claypan: super super small soil particles so it packs very tightly
hydrology
● pools become inundated
● water does not drain and stands for 10-65 days
● usually not more than 50 cm deep
● water recedes
● stays long enough to keep out grasses (preclude colonization by upland species)and
other species that cant stand water, but not long enough to support aquatic species
● low in dissolved nutrients and soils and also bad things
○ different from other ephemeral wetlands like alkali
seasonal variation
● inundated phase
● flowering phase
● dry phase
○ almost all annuals so die in summer
zonation
● zonation of vegetation within vernal pools. depends on time it is inundated (edges are
exposed earlier)
● different plants have different tolerance level of inundation duration
islands of native species in a highly invaded 'grassland' landscape
● almost all the species are native vs just outside the boundary almost all species are
non-native
Vernal Pool Flora
Document Summary
Seasonal (ephemeral) wetland underlain with a layer impermeable to water. Seasonable bc it"s over a layer of soil that doesn"t allow the water to percolate away. Almost everything in central valley is non-native except vernal pools. Can be surrounded by grassland or lodgepole pine forest, or blue oak woodland, or sagebrush steppe, or by coastal scrub, or prairie aka anywhere! Not really about overall climate but more about these temporary pools. Characteristics of med climates bc wet winter to build pool and dry in summer so pool disappears (or else it would just be a wetland) Claypan, hardpan, or otherwise impermeable layer (aquitard) This flat layer makes the water table build up when it rains. Claypan: super super small soil particles so it packs very tightly hydrology. Water does not drain and stands for 10-65 days. Usually not more than 50 cm deep.
