Trifolium variegatum Herbaceous Alliance
White-tip clover swales
White-tip clover swales
USDA Ecological Section Map
Summary Information
- Primary Life FormHerb
- Elevation50-1000 m
- State RarityS3?
- Global RarityG3?
- DistributionCAN: BC. USA: CA, OR, WA (NatureServe)
- Endemic to CaliforniaNo
- Endemic to California Floristic Province and DesertsNo
- Date Added2009/09/01
Characteristic Species
Trifolium variegatum is dominant or characteristically present in the herbaceous layer with Aira caryophyllea, Avena barbata, Briza minor, Bromus diandrus, Bromus hordeaceus, Castilleja attenuata, Deschampsia danthonioides, Erodium botrys, Erodium cicutarium, Hedypnois cretica, Hesperevax caulescens, Hypochaeris glabra, Juncus bufonius, Leontodon saxatilis, Lolium perenne, Microseris elegans, Mimulus guttatus, Montia fontana, Soliva sessilis, Trifolium gracilentum, Trifolium microcephalum, Triphysaria eriantha and Vulpia bromoides.
Vegetation Layers
Herbs < 50 cm; cover is intermittent to continuous.
Membership Rules
- Trifolium variegatum is conspicuous (average cover > 10%, but depending on season may be merely present) in the early to mid-spring growing season in the herbaceous layer; often growing with equally conspicuous cover of non-natives such as Hypochaeris glabra, Leontodon taraxacoides, Lolium perenne, and Vulpia bromoides (Klein et al. 2007).
- Trifolium variegatum > 50% relative cover, or > 30% relative cover in the herbaceous layer with a variety of other native and non-native herbs such as Bromus spp., Juncus bufonius, Lolium perenne, Lotus spp., Plagiobothrys spp., Trifolium fucatum, and others (Buck-Diaz et al. 2021, Sikes et al. 2023).
Habitats
Vernally moist edges of pools, swales, and seeps. Soils are sandy to clay or clay loam, generally fine grained. The USFWS Wetland Inventory (1996 national list) recognizes Trifolium variegatum as a FACW- plant.
Other Habitat, Alliance and Community Groupings
| MCV (1995) | California annual grassland series, Northern basalt flow vernal pool habitat, Northern hardpan vernal pool habitat |
| NVCS (2009) | North Pacific hardpan vernal pool, Northern California volcanic vernal pool |
| Calveg | Wet grasses and forbs, Vernal pool |
| Holland | Valley and foothill grassland, Native grassland, Wildflower field, Freshwater seep |
| Munz | Freshwater marsh, Valley grassland |
| WHR | Annual grassland, Wet meadow |
| CDFW CA Code | 42.005.00 |
National Vegetation Classification Hierarchy
| Formation Class | Mesomorphic Shrub and Herb Vegetation (Shrubland and Grassland) |
| Formation Subclass | Temperate and Boreal Shrubland and Grassland |
| Formation | Temperate and Boreal Freshwater Marsh |
| Division | Western North American Freshwater Marsh |
| Macro Group | Western North America Vernal Pool |
| Group | Californian mixed annual/perennial freshwater vernal pool / swale bottomland |
Remarks
Trifolium variegatum is a small but showy purple and white-flowered native annual legume. It is common throughout cismontane California in the early to mid-spring season. Botanists have described a bewildering array of infraspecific taxa for this species (Hickman 1993).
Stands form in swales, seeps, moist grassy flats, and intermittent stream channels as a conspicuous mix of native and non-native plants (Klein et al. 2007). Barbour et al. (2005, 2007b) noted that T. variegatum occurred within a group of vernal pool vegetation types of short inundation periods distinguished by species such as Blennosperma nanum, Cicendia quadrangularis, Lasthenia californica, Trifolium variegatum, and Triphysaria eriantha. We placed several of their associations in the Eryngium aristulatum, Lasthenia glaberrima, and Montia fontana-Sidalcea calycosa alliances. Their research focused on vernal pools, but stands of T. variegatum are also in seasonally moist or saturated upland settings. The relationships between this and other alliances need investigation because this alliance extends beyond vernal pools to these other settings.
We have defined this alliance by using T. variegatum as the native indicator species that occurs regularly but varies in dominance both spatially and temporally. In some years or in certain locations, non-native annuals surpass its abundance and cover. In-depth studies (Bartolome et al. 2007a, Buck 2006, Stromberg et al. 2007) describe the value of identifying persistent native species, even at low cover, as a means to understanding restoration potentials and the natural ranges and ecological variability of these vegetation types.
Pitt and Heady (1978) identified a negative relationship between Trifolium cover and annual grass cover. More recently, D’Antonio et al. (2007) discussed seasonal variation and ecological interactions between native and non-native herbs, and Corbin et al. (2007) discussed negative interactions among native Trifolium and non-native Erodium and annual grasses. Climatic variation in some years favors the dominance of Erodium and Trifolium species; in some years Avena species or Bromus hordeaceus dominate. Annual grasses tend to be favored in years when rain starts early, temperatures are relatively warm during germination, and rainfall is regular throughout the wet season. Conversely, Erodium and Trifolium species appear to be favored during years with a late rain onset or an extended winter or spring drought.
Stands form in swales, seeps, moist grassy flats, and intermittent stream channels as a conspicuous mix of native and non-native plants (Klein et al. 2007). Barbour et al. (2005, 2007b) noted that T. variegatum occurred within a group of vernal pool vegetation types of short inundation periods distinguished by species such as Blennosperma nanum, Cicendia quadrangularis, Lasthenia californica, Trifolium variegatum, and Triphysaria eriantha. We placed several of their associations in the Eryngium aristulatum, Lasthenia glaberrima, and Montia fontana-Sidalcea calycosa alliances. Their research focused on vernal pools, but stands of T. variegatum are also in seasonally moist or saturated upland settings. The relationships between this and other alliances need investigation because this alliance extends beyond vernal pools to these other settings.
We have defined this alliance by using T. variegatum as the native indicator species that occurs regularly but varies in dominance both spatially and temporally. In some years or in certain locations, non-native annuals surpass its abundance and cover. In-depth studies (Bartolome et al. 2007a, Buck 2006, Stromberg et al. 2007) describe the value of identifying persistent native species, even at low cover, as a means to understanding restoration potentials and the natural ranges and ecological variability of these vegetation types.
Pitt and Heady (1978) identified a negative relationship between Trifolium cover and annual grass cover. More recently, D’Antonio et al. (2007) discussed seasonal variation and ecological interactions between native and non-native herbs, and Corbin et al. (2007) discussed negative interactions among native Trifolium and non-native Erodium and annual grasses. Climatic variation in some years favors the dominance of Erodium and Trifolium species; in some years Avena species or Bromus hordeaceus dominate. Annual grasses tend to be favored in years when rain starts early, temperatures are relatively warm during germination, and rainfall is regular throughout the wet season. Conversely, Erodium and Trifolium species appear to be favored during years with a late rain onset or an extended winter or spring drought.
Life History Traits of the Principal Species
| Trifolium variegatum | |
|---|---|
| Life forms | Annual; herb |
| Seed storage | Soil |
| Seed longevity | Long |
| Mode of dispersal | Animal; wind |
| Germination agents | None |
| Mode of sprouting | N/A |
| Survivability after fire/disturbance | Fire-sensitive; thin epidermis |
| Disturbance-stimulated flowering | No |
| Reproductive range | One growing season |
| Recruitment | Low to high |
| Regional variation | Low |
Fire Characteristics
Trifolium variegatum and other clovers likely coevolved with fire in cismontane California. However, the relative influence and optimal frequency of such fires are speculative (Wills 2006).
| Fire return interval | — |
| Seasonality | — |
| Size/extent | — |
| Complexity | — |
| Intensity | — |
| Severity | — |
| Type | — |
| Regional knowledge | — |
Regional Status
- Central California Coast Ranges (M262Aa, Ae). Stands of Trifolium variegatum adjacent to stock pond at Blue Oak Ranch Preserve (Sikes et al. 2023). Stands of Trifolium variegatum or other white-tipped clovers occur in mesic meadows of Monterey Co., including stands at Fort Hunter-Liggett and at Wagon Caves cRNA (Keeler-Wolf 1989b, see Cheng 2004).
- Great Valley (262Ab, Ae, Ag, Ao). Stands occur in vernally moist areas and short-inundated vernal pool edges (Barbour et al. 2005, Klein et al. 2007).
- Northern California Coast (263Al). Stands exist in seasonally moist or temporary wetland settings at Mount Tamalpais in Marin Co. (Evens and Kentner 2006).
- Northern California Interior Coast Ranges (M261Ca-b). Stands in this section include those in Napa Co.
- Sierra Nevada Foothills (M261Fa-c). Stands throughout the northern two subsections include four associations (Evens et al. 2004, Klein et al. 2007). Stands also express themselves in the southern subsection in vernal pools as the Hesperevax caulescens-Trifolium gracilentum association (Barbour et al. 2007b). These are mostly small (< 0.25 ha) and adjacent to ephemeral streams and swales, although some are on moist terraces and slopes. Adjacent vegetation includes various associations of Quercus douglasii or Q. lobata woodlands, as well as stands of the Lasthenia glaberrima, Layia fremontii-Achyrachaena mollis, Nassella pulchra, and Lasthenia californica-Plantago erecta-Vulpia microstachys alliances.
Management Considerations
Anderson (2005) described Native American uses of clover. In good clover years, many tribes throughout California relied heavily upon the foliage of Trifolium variegatum and other native clovers as a source of nutritious fresh greens. Certain areas within each tribal jurisdiction supplied reliable clover patches.
Restoration issues include introduction of native seed to relatively degraded grasslands dominated by non-natives (Corbin et al. 2007). These introductions may be expensive and unpredictable depending on seasonal rainfall and temperature conditions.
Associations
- Trifolium gracilentum - Hesperevax caulescens [1], [3]
- Trifolium variegatum [2], [3], [4], [5], [6], [7]
- Trifolium variegatum - Juncus bufonius [2], [3], [4], [5]
- Trifolium variegatum - Lolium perenne - Leontodon saxatilis [2]
- (Trifolium variegatum - Vulpia bromoides) - Hypochaeris glabra - Leontodon saxatilis [2], [3]
References
- [1] Barbour, M.G.;Solomeshch, A.I.;Buck, J.J. 2007b
- [2] Klein, A.;Crawford, J.;Evens, J.;Keeler-Wolf, T.;Hickson, D. 2007
- [3] Buck-Diaz, J.;Batiuk, S.;Evens, J.M. 2012
- [4] Buck-Diaz, J.;Harbert, B.;Evens, J. 2011
- [5] Buck-Diaz, J.;Ratchford, J.;Evens, J. 2013
- [6] Buck-Diaz, J.;Sikes, K.;Evens, J.M. 2021
- [7] Sikes, K.;Buck-Diaz, J.;Vu, S.:Evens, J. 2023
- Evens, J.M.;Kentner, E. 2006