PLS 147 Midterm: Midterm 1 Lecture 1-10 Study Questions: Plant Communities, Abiotic Bases, Ecological Gradients, Geological Setting, Paleohistory, Valley Prairie Grasslands, Vernal Pools, Marine Plant Communities, Tidal Marsh, Freshwater Marsh, Grazing, Restoration, Oak Woodlands, Riparian Forest
The Nature of Plant Communities
Describe what is meant by a community in ecological terms. You can speak to specific
theoretical constructs if you wish, but what are the broad factors that constitute a community?
●A plant community is a group of plant species that interact with each other in a certain
habitat and time period. This term also considers their characteristics such as relative
abundance and spatial distributions. An ecological community includes animals and
microbes as well.
Plant communities often have hazy boundaries. What factors contribute to clear, distinct
boundaries between plant communities?
●spatial
○abrupt change in soils or hydrology, eg serpentine soils, vernal pools, riparian
○a community dominante determines the presence/absence of many species, eg
timberline (edges of the trees b/c pine needles change the soil, etc), grasslands,
sierra conifers
●temporal, eg. succession after a fire
Describe general delineations used to classify physiognomy. Give the names and the
quantification units and ranges.
● cover, height, life forms
● forest: 60-100 nearly complete woody canopy cover (60-100%)
● woodland: 25-60% moderate canopy cover
● savanna 10-25% low canopy cover
● grassland: 0-10%, little/no woody cover
What are the layers of a canopy?
● Canopy
● Sub canopy
● Woody understory (shrubs)
● Herbaceous understory
What is a problem with mapping “pristine” vegetation (vegetation that existed prior to European
settlement) to define plant communities in CA?
● general answer: Plant communities often change gradually (continuously) across
gradients, without abrupt boundaries
● because we don't know what the pristine conditions were
Ecological Gradients, Geological Setting, Paleohistory
What is meant by the California Floristic Province. Contrast to the plants found within the
borders of State of California.
● >5800 native species
○ 25% of which are endemic
● Hotspot for rarity and richness in plant species
● California's composition of plant species, similar to other regions with a winter rainfall
and summer drought climate like the Mediterranean Basin
What determines a plant’s distribution (and richness)?
● Soils (substrate and geology)
● Large-scale climate patterns
● Local climate (maritime and topography)
● History
What is a “Mediterranean climate”? Include in your answer specific regions where this climate is
found, what these regions have in common geographically, and yearly timing of rainfall and
temperatures.
●Hot and dry summers
○ Many plants have a sclerophyll (hard leaf) in order to reduce evapotranspiration
● Cool and wet winters
●It is found only in the Mediterranean Basin, SW Africa, SW Australia, Central Chile, and
California
○the western coast of continents
What percent of the world’s land area has a Mediterranean climate? What percent of this area
does California occupy?
● 2% of world's land is Mediterranean
● CA: 10%
In what way is California an island and how might this affect non-native vegetation
●California is an island in that it’s the only area with a mediterranean climate in the region
○ isolation generates endemism
● Its latitudinal breath (smaller)
● Younger than the mediterranean basin (recall the California Assembly Line)
● Isolated by the Sierras
● island species are inherently more vulnerable
○ also, plants from mediterranean basin w/ longer evolutionary history are more
successful and outcompete natives in CA
What is the North Pacific High? (from the Mooney reading)
●A pressure system with immediate effect on California’s climate
● A subtropical anticyclone
● Creates warm and dry conditions
Describe the influence of the ocean on the climate of California.
●The coastal regions of CA benefit from the temperature stability that the ocean provides
(due to water’s high specific heat)
● The wind coming from the west brings moisture (evap from the ocean)
What is Tule Fog?
●Tule fog, often occurring each winter in the san Joaquin and sacramento valleys reduce
visibility and result in constantly cool daytime and nighttime temperatures
● In the winter, light winds are common and the ground is wet enough to moisten the
boundary layer. At night the cold air drains down the sides of the sierra Nevada to the
east and the coast ranges to the west facilitating the formation of a strong nocturnal
temperature inversion. Little wind mixing and sufficient humidity forms shallow
radiation fog overnight underneath this inversion. This radiation fog is known as tule fog
after the tule grass wetlands in the region. During the daytime, the fog reduces visibility
and reflects large amounts of incoming solar radiation, preventing the surface from
warming and aiding the persistence of the fog. Not only keeps surface cool during the
day but also keeps the surface warm at night by reabsorbing and re emitting
infrared energy. The fog is blown away by increasing winds of approaching winter
storms that mix the air and break down the thermal inversion.
What are the main types of geology in California, and how are they formed?
●All different major types of parent material are found in CA
● Geology drifted in from many places due to tectonic action
● Subduction of rocks led to the intrusion of serpentine from the mantle
● Isolation between sierra and Klamath mountains
In California, why do inland areas like the Central Valley have a drier climate than adjacent
coastal areas?
●Coastal areas get the moisture from the ocean air, but that moisture is quickly
precipitated and doesn’t always travel all the way to the Central Valley
What is the main stress that plants growing in Mediterranean climates have to endure?
●The high heat and low water conditions of the summer
Name three reasons that California has such great diversity of plant species and communities
●Diversity of soils
● Diversity of local climate
● Diversity of histories
In CA, for every 1000 ft increase in elevation, temperatures decrease
(A.)_5.3_ ̊F
and annual rainfall increases (B.) _10 inches (up to 8000 ft on the eastern slope of the Sierras).
Document Summary
Describe what is meant by a community in ecological terms. A plant community is a group of plant species that interact with each other in a certain habitat and time period. This term also considers their characteristics such as relative abundance and spatial distributions. An ecological community includes animals and microbes as well. Abrupt change in soils or hydrology, eg serpentine soils, vernal pools, riparian. A community dominante determines the presence/absence of many species, eg timberline (edges of the trees b/c pine needles change the soil, etc), grasslands, sierra conifers. Give the names and the quantification units and ranges. Forest: 60-100 nearly complete woody canopy cover (60-100%) General answer: plant communities often change gradually (continuously) across. Because we don"t know what the pristine conditions were gradients, without abrupt boundaries. What is meant by the california floristic province. Contrast to the plants found within the borders of state of california. Hotspot for rarity and richness in plant species.
