Overview
A single population in Solano County, the historical range of San Joaquin Valley Orcutt grass, is believed to be in the Southern Sierra Foothills Vernal Pool Region, which includes parts of Stanislaus, Merced, Madera, Fresno and Tulare counties.
This species was listed as threatened on March 26, 1997.
Threats to the San Joaquin Valley Orcutt grass include small population size, competition from weedy non-native plants and habitat loss and degradation due to agricultural land conversion and other uses, as well as climate change climate change
Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's climate system and caused change on a global scale.
Learn more about climate change .
Scientific Name
Identification Numbers
Characteristics
Life Cycle
Seeds of this genus typically germinate underwater in the spring when the standing water begins to evaporate from the pool and after they are colonized by aquatic fungi. Plants emerge underwater, forming a basal rosette of juvenile leaves that are maintained for roughly three months. As the water temperatures increase, floating leaves form and remain until the standing water has evaporated, at which point terrestrial leaves are formed. Flowering begins within a few days after the pool has dried and typically peaks in mid-June but may be extended into August or September depending on growth conditions. Seed production in Orcuttia species can vary two- to three-fold among years.
Habitat
San Joaquin Valley orcutt grass is a highly specialized plant with an evolutionary adaptation that facilitates photosynthesis in arid and semi-arid climates. It is dependent on deep vernal pools for survival. Typical landforms upon which it occurs include remnant alluvial fans and stream terraces. It is known to occur in acidic soils with textures ranging from clay to sandy loam. San Joaquin Valley orcutt grass requires inundated soils for at least part of the year for seed germination, seed bank storage and its juvenile aquatic growth stage. The species has adaptations that promote the dominance of it and other Orcuttia species in vernal pool environments for a month or more after the pools have dried.
Land on which the natural dominant plant forms are grasses and forbs.
Environments influenced by humans in a less substantial way than cities. This can include agriculture, silvaculture, aquaculture, etc.
Physical Characteristics
Orcuttia species produce three different types of leaves during their life cycle:
- Submerged basal rosette of five to eight cylindrical, juvenile leaves
- Intermediate leaves in which the submerged portion is cylindrical, but the upper portion has a flat, floating blade
- Terrestrial leaves with a flattened blade and loosely sheathing base, which develop after the pools dry
Mature plants of San Joaquin Valley orcutt grass grow in tufts of several erect stems, each of which ranges from 2.0 to 11.8 inches (5 to 30 centimeters) in length. The entire plant is grayish-green, due to the long hairs on the stem and leaves. Terrestrial leaves are 0.08 to 0.16 inch (2 to 4 millimeters) wide. Each spikelet of the inflorescence is flattened and contains four to 30 florets. Both rows of spikelets grow towards one side. The spikelets are crowded near the top one-third of the stem, producing a head-like inflorescence 0.8 to 1.4 inches (2 to 3.5 centimeters) long.
There is anecdotal evidence of two different morphological variations of San Joaquin Valley orcutt grass, with differences in plant stature and seed head appearance. These different types have been observed in multiple locations with both types present in the same pool, but an individual plant with both characteristics has not been observed in the field.
Timeline
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