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Rare, Uncommon, and Significant Vascular Plants at Jasper Ridge Biological Preserve


JRBP Locally Rare vascular plants v10 10/2023 [.kmz] | Oakmead Herbarium home 

Rarity is a statement about geographic distribution and abundance (Fiedler 1995). For conservation purposes distribution can be based on state, bioregion, county or specific property (Jasper Ridge Biological Preserve in our case) frames of reference. Jasper Ridge has vascular plants with state-wide ranking [Table 1 below], plants uncommon in the county or Santa Cruz Mountains Bioregion [Table 2 below], or simply uncommon on the Preserve, frequently with only a few individuals and a single or few occurrences [Table 3 below]. 

The concept of Local Rarity references uncommon plants other than the more publicized, better appreciated, and often better surveyed State-, Federal-, and CNPS-listed Special Status Plants. The California Environmental Quality Act (CEQA) allows consideration of Locally Rare species (Wood 2014). Through the lens of Local Rarity the significance of the JRBP vascular plant assemblage is even greater than that conveyed by total taxa (species diversity) and other commonly used measures such as ecosystem diversity.In view of documented Preserve species loss and declines and the typically small population size of the Locally Rare-designated plants, one is reminded of the importance of systematic restoration and invasive plant interventions to enhance the prospects of sustaining the Preserve's biodiversity.  A remarkable insight from preliminary work (based on extensive fieldwork and a draft inventory developed from Toni Corelli's 2011 Checklist of the Vascular Plants of San Mateo and Santa Clara Countiesalong withSan Francisco and Santa Cruz Co. data)is that perhaps 17% of the flora of the Santa Cruz Mountains2 -- on the order of 360 plants -- are Locally Rare with five or fewer locations, and approximately 24% of those plants are documented for JRBP. The separate watchlist of uncommon plants includes about 100 taxa of which over half are documented for the Preserve; we expect some of these to be reclassified as the project develops and more information is available. Fifteen percent of the Preserve's native flora are Locally Rare or Special Status Plants (85 of 575 terminal aka minimum level taxa: species, subspecies, varieties). About 1/3 of the Jasper Ridge LR plants are currently not known to be extant on the Preserve, and are designated so on the provisional lists.

  • The provisional database for San Mateo Co. and the Santa Clara Co. portion of the Santa Cruz Mtns (developed from Toni Corelli's 2011 Checklist of the Vascular Plants of San Mateo and Santa Clara Counties) simply requires documentation of a taxon in 5 or fewer parks or preserves for Locally Rare status. Plants occurring in 6-10 locations are placed on a watchlist. Exceptions have been made. Data is for apr 100 properties/parks/preserves. Locally Rare status therefore indicates a plant is documented for no more than 5% of the properties. A  floristic region approach (subregions) and/or a numbered occurrences approach may be developed in the future after the example of CNPS East Bay and Santa Cruz Co. chapters.  Locally rare plants with only 1 or 2 locations number ~200 taxa. 
  • We also follow the Locality Data Convention of the CNPS Santa Cruz Co  (Neubauer 2013:11). Documentation 25 years or older is considerd a historical record; lower case jrbp signifyies a historical record for Jasper Ridge, whether voucher or other observation, and all such records are not used as verification a plant is extant. UPPER CASE ITALICS JRBP signifys plants are present on the Preserve. Multiple occurrences on the Preserve when specified are generally separated by a minimum of .25 mile.
  • Only current populations should be considered when designating a taxon locally rare. Across the bioregion data are frequently from cumulative checklists and historical records that do not answer the questions 1) is a taxon currently present on a specific preserve; and 2) is the taxon population stable, etc?  However, Jasper Ridge Biological Preserve data are supported by an active collecting program and 6000+ herbarium vouchers, thousands of  geo-referenced photo vouchers, and other documentation. Photos are archived in Flickr. Thomas (1961) is the single most complete source for what would now be considered historical records covering the entire region; his voucher-based location information has largely been aggregated by the Consortium of California Herbaria (CCH) and Calflora. Many of these old records/reports have sketchy location information.
  • There is a CNPS Santa Clara Valley Chapter resource page for listed plants of San Mateo and Santa Clara counties. 

Checklists of Jasper Ridge Biological Preserve Rare, Uncommon, and Significant Vascular Plants (current and historical)

N.B. Tables 2 and 3 are based on the 6/1/2021 Provisional Working List of Locally Rare plants in the Santa Cruz Mountains. Some taxa may move from the LR list to the Watchlist or vice versa once the CNPS State LR Committee refines protocol 

Table 1. Special Status Plants [Rare.kmz and Dirca.kmz] -- CNPS-listed plants at Jasper Ridge (including historical records)
Table 2Locally Rare v10 10/2023 [.kmz] -- Plants at Jasper Ridge with 1-5 current populations in the Santa Cruz Mountains in San Mateo and Santa Clara counties, or more populations if meet other criteria.4 Abbreviations: jrbp = historical record > 25 years before the present; #V = number of locations we've been able to verify as extant; should match the number of locations in italics. (Protected by CEQA).
Table 3Watch List [.kmz]

  1. Plants at Jasper Ridge with 6 to 10 current populations in the Santa Cruz Mountains in San Mateo and Santa Clara counties, or more populations if meet other criteriaincluding species with aging populations with minimal regeneration (Not protected by CEQA).
  2. Plants uncommon at Jasper Ridge but not necessarily elsewhere (single or a few occurrences of usually a few individuals)


1In addition to number of taxa, special status (listed) plants, vegetation types, plant associations, habitats and special soils, there are other ways of characterizing the Preserve's vascular flora and its significance to our bioregion, the Santa Cruz Mountains. Ecologists and taxonomists are currently analyzing local and regional floras state-wide in terms of evolutionary diversification, divergence, and survival by combining spatial information from herbarium collections and DNA-based phylogenies (Kling et al. 2018), others are using LIDAR and other enhanced vegetation mapping techniques. Lineages of Jasper Ridge plant families can be viewed on the chart Phylogenetic guide to Jasper Ridge Vascular Plant Families.

2 The Santa Cruz Mountains, a section of California's outer Coast Range, form a distinct geographical and biological unit. They are separated from the North Coast Ranges by the Golden Gate, from the Diablo Range to the east by San Francisco Bay and the Santa Clara Valley, from the Santa Lucia Mountains and Salinas Valley by the Pajaro River, and the Pacific Ocean forms the western boundary. (Thomas, 1961: p. 4-5) The Santa Cruz Mountains region is about 1386 square miles (887,040 acres, 358,972 hectares) includes all of San Mateo, Santa Cruz, and San Francisco counties, and the western portion of Santa Clara Co. [Some workers consider San Francisco south to San Bruno mountain a different, generally formerly treeless zone that has been termed Franciscan by James Roof]. The Santa Cruz Mountains hosts three CNPS chapters. The Jepson Flora Project geographical subdivisions that include our region of the California Floristic Province are SNFrB (San Francisco Bay Area) and CCO (Central Coast). 

3 Calflora Location Quality. When GPS enhanced devices are used to make observations, the device typically produces an error radius understood as the accuracy of the device at the moment the observation was made. If an observation arrives with an error radius of 2 meters, it indicates that the plant was growing somewhere in an area of 12.5 square meters around the given coordinates.

Some specimen records from the Consortium of California Herbaria were georeferenced after the fact (eg. from written location descriptions), and are assigned a large error radius. If an observation arrives with an error radius of 2 miles, it indicates that the plant was growing somewhere in an area of 12.5 square miles (8,000 acres) around the given coordinates.

In order to integrate these diverse record types, Calflora classifies the quality of location data in several levels as follows.


Radius (meters)

Area (square meters)

Area (acres)



≤ 5.6

≤ 100

≤ 0.025



≤ 44

≤ 6,000

≤ 1.5


≤ 76

≤ 18,000

≤ 4.5


≤ 139

≤ 60,000

≤ 15



≤ 489

≤ 750,000

≤ 185


≤ 798

≤ 2,000,000

≤ 494



≤ 3090

≤ 30,000,000

≤ 7,413


> 3090

> 30,000,000

> 7,413

4 Criteria

  • Aging populations with minimal regeneration
  • Declining
  • Disjunct
  • Fire Follower
  • Limited and Threatened Habitat
  • Narrow range in the two-county area
  • Range Limit
  • Number of Regions
  • Small geographical range
  • Small populations
  • Stressed, such as weed invasion, development, grazing, trampling, water course changes, insect invasion, etc.

NOTE: Only current, naturally occurring populations are considered when determining rank. No historical or planted populations are included. Also, populations with a questionable identification are not included. 


--Tim Krantz