Common (Translated Scientific) Name: White-tip Clover Vernal Pool Alliance

Colloquial Name: White-tip Clover Vernal Pool

Hierarchy Level:  Alliance

Type Concept: This alliance consists of intermittent to continuous cover of herbs <50 cm in height. 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 taraxacoides, Lolium perenne, Microseris elegans, Mimulus guttatus, Montia fontana, Soliva sessilis, Trifolium gracilentum, Trifolium microcephalum, Triphysaria eriantha, and Vulpia bromoides. This alliance occurs in California at 50-1000 m elevation along vernally moist edges of pools, swales, and seeps. Soils are sandy to clay or clay loam, and generally fine-grained.

Diagnostic Characteristics: 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. 2007b).

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: 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 Trifolium 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. Several of their associations are placed in Eryngium aristulatum, Lasthenia glaberrima, and Montia fontana - Sidalcea calycosa alliances. Their research focused on vernal pools, but stands of Trifolium variegatum are also in seasonally moist or saturated upland settings. The relationships between this and other alliances needs investigation because this alliance extends beyond vernal pools to these other settings.

This alliance is defined using Trifolium 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 (Buck 2006, Bartolome et al. 2007, 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.

Similar NVC Types: No Data Available

note: No Data Available