A California grasslands alkali specialist, Hemizonia pungens ssp. pungens, prefers non‐alkali soil

Abstract

Question: Edaphically severe habitats commonly support edaphic endemics, specialized plant species that do not occur elsewhere. The endemism of native plant species in edaphically specialized habitats suggests either (a) that these native endemic species are uniquely specialized to survive and grow better under the conditions prevalent in these harsh areas, or (b) that these areas represent refuges from competition with other (often exotic) species.Location: Central Valley, California, USA. Methods:We surveyed the vegetation distribution in alkali sinks and carried out a reciprocal transplant greenhouse experiment crossed with a competition treatment to examine the interplay between interspecific competition and edaphic factors in determining relative performance of an alkali endemic forb (Hemizonia pungens ssp. pungens) and its exotic grass competitor (Lolium multiflorum).Results: Lolium consistently performed better in nonalkali soil. In contrast, Hemizonia, in the absence of competition, performed significantly better on the nonalkali soils, but in competition with Lolium, performed equally well on alkali and non-alkali soils.Conclusions: These results suggest that Hemizonia does not inherently prefer harsh alkali soil, but is better able to tolerate alkali soil and may be excluded from more moderate soils by competition. Therefore, edaphic and biotic effects may interact to determine the spatial distribution of this edaphic endemic. Our data suggest a mechanism by which competition between native and exotic species on impoverished soils leads to dominance of native species and creation of refugia for native species where exotic species are unable to thrive.

Plant communities in harsh sites are less invaded: a summary of observations and proposed explanations

“…For example, non-native Lolium multiflorum (ryegrass; now Festuca perennis ) that dominated a non-sodic matrix was virtually absent in adjacent alkali sinks, whereas native Hemizonia pungens ssp. pungens was more abundant in the alkali sinks ( Veblen and Young 2009 ). It is likely that amelioration of naturally sodic soils for the purpose of agriculture (for example, by addition of gypsum: see Qadir et al .…”

Archeological Sites and Relict Landscapes as Refuge for Biodiversity: Case Study of Alexandria City, Egypt

“…Tabieh Um Kebeba and Tabieh Kousa Basha recorded the lowest mean values of EC, Mg 2+ , Ca 2+ and TDS, and the highest mean value of CaCO 3 , but the former recorded plenty of species, as it had the highest values of Fe, Zn, Cu, Silt, SAR, OM, SP, and N. On the other hand, Atta Fortress (Anfoshy) recorded the lowest number of species because it had the highest Mn, SAR, EC, Na + , Cl − , and TDS levels, and the lowest CaCO 3 , HCO 3 − , SP, P and Fe levels. Among the different study sites, patches of edaphic uniqueness are common, and these act as refuges for native species in highly colonized ecosystems [74], as the native species can use them to escape competition and disturbance [75]. However, the scarcity of studies on the role of soil in determining the prevalence of rare and endemic plants obstructs the efforts of public and private organizations to preserve such specialized microhabitats.…”

The Role of Soil Properties in Plant Endemism – A Revision of Conservation Strategies

“…Climate limits the flora [18,19], while geological characteristics largely define habitat diversity [4]. Moreover, edaphically severe habitats commonly support edaphic endemics, which are plant species that do not occur elsewhere [20]. Although that might be not enough to recognize the endemic species, edaphological characters (macro and micro) are essential to establish phylogenetic hypothesis of endemic taxa and areas of endemism, looking for consistency with geological models [21][22][23].…”

“…The LOAs in root exudates may play an important role in the solubilization and plant availability of mineral nutrients in the rock [55]. Additionally, [20] mentioned that rock outcrop represent refuges from competition with other (often exotic) species. The edaphic endemics are now restricted to unusual and sometimes contaminated soils, but may have been able to withstand large concentrations of metals in their tissues or large quantities of calcium oxalate crystals [40].…”

“…In the Chihuahuan Desert region it was found that several Cactaceae species, particularly many members of the Cacteae tribe often inhabit extremely specialized habitats, such as gypsum and other unusual soil formations ( Figure 7) [64]. The patches of edaphic endemism also frequently exist as refuges for native species in highly invaded ecosystems [20], ultramafic substrates act as sites in which Pinus balfouriana escapes of the competition [65]. Moreover, the work with Helianthus exilis showed the need to protect specialized microhabitat found only within the large serpentine outcrops, the species cannot survived outside the narrow conditions proper of its habitat [66].…”