Alkali meadow communities:
Alkali meadows occur in areas where the water table is shallow (one
to three meters deep), and soils are alkaline. They are probably the most
distinctive native plant communities in Owens
Valley. In California,
outside the Eastern Sierra alkali meadows remain only in small fragments
in the southern Central Valley, and on the Modoc Plateau (Davis 1998),
and are classified as very threatened by the California Natural
Diversity Database (Sawyer and Keeler-Wolf 1995). In the Great
Basin, alkali meadow is not even recognized as a major plant
community (Cronquist 1986, Barbour and Billings 1988). In 1864,
however, William Brewer estimated meadows to cover up to 10% of the entire
Owens Valley
(Farquahr 1974), while DWP estimated that meadows occupied about 25% of
its Owens
Valley holdings in
1984.
Owens Valley meadows are distinctive due to their
topographic positions as well as their extent. While meadows typically occur
throughout the Great Basin in narrow flood plains along rivers and streams, alkali meadows
in Owens Valley also occurred in a broad zone at the toe slopes of the giant alluvial fans
coming down the west side of Owens Valley from the Sierra. According to Lee (1912):
"The
grass or meadow lands...extend well out into the level valley. The
growth is most luxuriant in the spring zone, which is about a quarter
of a mile wide and is situated at the upper edge [i.e. the upslope edge
on the west side] of the valley floor. Here are numerous small flowing
springs ... which start the meadow grass early in the season and keep
it green until late in autumn. Farther out in the valley
[i.e. to the east, approaching Owens River]
the salt grass makes a green carpet from May until late July...
In the salt grass land there is always a deposit of alkali around the
plant roots, and the soil surface is crusted. The spring zone,
however, is free from alkali."
Two
native grasses are characteristic of Owens
Valley alkali meadows:
Sporobolus airoides (sacaton) and Distichlis spicata (saltgrass).
The meadows are home to several endangered species such
as state-listed Sidalcea covillei (Covilles checkerbloom)
and CNPS-listed Calochortus excavatus (Inyo
County star tulip),
Crepis runcinata
ssp. hallii
(Hall's meadow hawksbeard), and Spartina
gracilis (alkali cordgrass).
Other common common graminoids are Leymus
triticoides (beardless wildrye) and Juncus balticus (Baltic rush), while Glycyrrhiza
lepidota (American licorice) and Haplopappus
racemosus are some of the more common perennial herbs (Manning
1997). Total grass cover in relatively unimpacted meadows ranges from
as low as 15% to as high as 100%.
In many meadows, however, the shrub species Chrysothamnus
nauseosus (rabbitbrush) and Atriplex
lentiformis ssp torreyi
(Nevada
saltbush) are present and increasing in abundance over time.
Evidence suggests that when meadows are subject to pumping-induced
water table drawdowns, they are vulnerable to conversion to alkali scrub
communities (Manning 1999). While
some shrubs were undoubtedly present in meadows at the time of European
settlement, it is interesting to not that none of the early observers
of the valley noted their presence in meadows.
Alkali meadows
provide valuable forage for livestock and without proper management may suffer grazing
impacts. They are also reliable indicators of shallow water tables and thus are the
sites of many of Los Angeles's groundwater pumps. Given the biological value of
meadows and the potential for both grazing and pumping impacts, their condition in Owens Valley
is one of the key indicators by which the effectiveness of management under the Inyo-LA
Water Agreement can be measured. To date, results show pumping management is failing
in many parcels (Manning 2002).
Citations