Thursday, July 26, 2012

Hydrophytic vegetation of the San Joaquin Delta

With the revival of quasi-dormant debate over the Peripheral Canal/Tunnel,  I point out our poor understanding of Delta flora and vegetation in relation to salinity gradients.  Marsh salinity in the Delta region is suspected to have undergone a strong, directional increase associated with anthropogenic hydrologic modification.  I have not yet found a comprehensive analysis of existing vegetation salinity gradient relationships, and consequently wonder if any such study has been undertaken.  Predicting future vectors of marsh ecosystem change, and any but feeble hope for restoration, needs to account for pre-settlement flora and vegetation conditions in the Delta.

On July 17, 1896 Willis Jepson collected yellow pond lily (Nuphar polysepala) at Stockton.  Nuphar polysepala is a scattered, important member of the hydrophytic flora of Sierran lakes, mainly at about 7000 ft.  Nuphar does occur at low elevations, such as in Marin County, and other coastal lakes.  The occurrence of N. polysepala in the deltaic Great Valley is significant because this taxon is a indicator of water salinity: it is salt intolerant (1). 

Nuphar polysepala was still extant near Stockton at least until the early 1970s.  In the mid-1960s, it was still present in Pixley Slough.  In the 1970s, it was present near Snodgrass Slough near Locke, although this latter site was not recorded by Bowcutt (2).   Very probably, if salt water intrusion has taken its toll on the Delta hydrophyte flora, Nuphar would now be extirpated.  Is it? 

Several other hydrophytes are known from >60-100 yr old historical records in the Delta: Carex comosa near Holt in 1928, Meneyanthes trifoliata (3), Potamogeton nodosus in 1928, P. zosteriformis in 1949 etc etc.  Lycopus americanus, another non-saline hydrophyte, is apparently still present as of 2002. 

These non-saline hydrophytes are indicators of delta water quality and their local distribution, and their placement in a data-based gradient analysis of Delta marsh vegetation is needed.  

I poist that saline intolerant hydrophytes have been eliminated from much of the Delta region associated with the inland intrusion of brackish or saline waters.  If these non-halophytic halophytes persist today, their communities become a model for restoration.  Where might this persistent, original hydrophytic vegetation remnants be ?

1.  Padget, D. et al. 1999. American Journal of Botany 86(9): 1316–1324.
2.  Bowcutt, F.  1996. Madrono Vol. 43, no. 3, pp. 417-431.
3.  Mason, H.  1957. Flora of the Marshes of California. UC Press

Sunday, July 22, 2012

Northern distributional limit of Juniperus californica

Over expansive portions of North America, juniper dominated vegetation is afforded ‘formation’ status: that is, a dominant, zonal ecosystem characterized by a single species (dominant in biomass and of trophic cascades), extensive, climatically-correlated vegetation type on a continent-wide scale.  In California, a Juniperus californica community has not been recognized at the higher-syntaxon level: in southerly California, Thorne (1) did not distinguish a Juniperus californica vegetation type where it is most abundant.  Certainly at lower syntaxonomic levels (associations), J. california communities are of ecological interest. California juniper rarely forms extensive stands in the northerly part of its geographic range.

The geographic range of J. californica has been little discussed in classical conifer synchorological literature: Jim Griffin and Bill Critchfield did not map Junperus california (2) probably because these foresters considered it to be 'not a tree'.  Conifer distribution maps offered up by Little (3), using his characteristic method whereby a radius envelope was drawn encircling each known site, shows the range of J. californica becoming more discontinuous  northward in California.  The range map in Adams (4) is generalized.

I will leave aside the fact that southerly Junipers related to J. californica should probably be afforded taxonomic segregation (perhaps as subspecies):  J. cedrociana on Cedros Island;  J. ‘californica’ on Guadalupe Island, which is considered extirpated; might be distinct, given the density of unique endemics in that flora.  Others in far south Baja?

Of considerable interest is the single specimen attributed to J. californica from the Klamath River canyon, Siskiyou County (SD51279), fully 100 miles north of Ash Creek.  What species is this?  A Juniper plexus-nexus might be indicated in the Klamath-Siskiyou ‘knot’ which perhaps still has some untying to do: Juniperus californica var. klamathensis L.F. Henderson, described from near Mt. Ashland, and considered a synonym of J. occidentalis (4), is at the far westerly extent of that arid, cold-interior tree.  Also of note is a disjunct outlier also being called J. occidentalis (2) in Trinity County.  All of these, again, indicate a Klamath-knot that merits study to untie; Vasek (6) found some of these westerly outliers to be chemically distinct.

Sudworth (5) reported J. occidentalis from the Canyon Creek Lakes watershed in the Trinity Alps: Griffin & Critchfield (2) guessed this report to be Juniperus communis (of Sect. Juniperus):  this report needs field survey, as the Canyon Creek watershed obviously has its own entangled ‘Klamath knot” in the guise of Bochera serpenticola, Sedum paradisum and other narrow endemics which grow there.

Northern Limit at Ash Creek
The northerly distributional limit of J. californica is at the very head of the Sacramento Valley,  specifically at Ash Creek, east of Anderson, which is tributary to the Sacramento River just north of the Tehama County line.  The colony of J. californica is scattered within a foothill savannah matrix of Quercus douglasii and Pinus sabiniana on very shallow, stony, volcanic-derived ‘soils’.   Specimens attributed to another Ash Creek (specifically CAS349187) are incorrectly mapped.  Other far N specimens are mis-labeled (CAS515186), these are J. occidentalis.

The Juniperus californica stand can be seen along the county road (Ash Creek Road) for several miles beginning at the low hills that begin just east of the Sacramento River crossing at Balls Ferry.   The site has not burned in recent times, and many trees are large ‘bushes’ – that is, about 3-4 meters tall and multi-trunked. 

1. Thorne, R.F.  1976.  pp. 1-31 in Vegetation of Southern California.  Calif. Native Plant Soc.
2.  Griffin, J.R. & W.B. Critchfield. 1976 (supplement).  USDA Forest Service Res. Paper PSW-82
3.  Little, E.L.  1971.  Atlas of United States Trees. Vol. 1. USDA Forest Service Misc. Pub. 1146
4.  Adams, R.P.  2011.  Junipers of the World: the genus Juniperus.  3rd ed.
5.  Sudworth, G.B.  1901.  Forest trees of the Pacific slope.  USDA.
6.  Vasek, F.C.  1966.  The distribution and taxonomy of three western Junipers.  Brittonia 18:350-372.

Saturday, July 7, 2012

The biogeographically correct eastern border of California's Klamath bioregion

In formulating the now well known Jepson bioregions for California, Jim Hickman made one significant error: he mis-mapped the geographic setting that differentiates the Klamath Ranges (KR) region from the Cascade Ranges (CaR) region.  Hickman’s boundary concept was correctly formulated: the Cascade region he characterized as “this volcanic region..” which contrasted with the Klamath Range region geologically,  which is also correlated with strong biogeographic pattern (along an aridity gradient from toward the interior).  However, in the 1989 edition (Hickman 1989), the map depicts the border that, in the color map and text in the 1993 Jepson Manual (Hickamn 1993), is “...more or less along of Interstate 5”. 

This border is geologically and biogeographically wrong.

Both geologically and biogeographically, the Klamath Ranges region includes about 250,000 acres of non-volcanic mountainous terrain comprising the McCloud arm, Squaw Creek arm, Pit River arm of Shasta reservoir, including the highest peaks in the reigon Grizzly Peak (6252 ft) and Bald Mountain (5536 ft), a region of metamorphic rocks.  The vegetation of the region has more in common with the Klamath Ranges than the Cascade Ranges, being forests largely dominated by Douglas-fir.  The region in question is home to two endemics I have described: Shasta boneset (Agartina shastensis) and Shasta Snow-wreath (Neviusia cliftonii), both with high fidelity for calcareous, not volcanic rocks.

The first figure shows the proposed, corrected border between the KR and CaR regions (red line) imposed on the map that appears in the inside front cover of both editions of the Jepson Manual.

Essentially, the border I suggest is exactly coincident with the extent of the Eastern Klamath terrane (Irwin 1994), which to the east is bordered by Quaternary and Tertiary volcanic rocks of the true Cascade ranges (yellow eastern border of the second figure).


Hickman, J.C. 1989.  Introduction to the Jepson Manual.  Jepson Herbarium, University of California, Berkeley.

Hickman, J.C.  [Ed.].  1993.  The Jepson Manual, Higher Plants of California.  University of California Press.

Irwin, W.  1994.  Geologic Map of the Klamath Mountains, California and Oregon.  USGS Map I-2148.