Analysis of polyphenols,phytosterols, and bitter principles in <Emphasis Type="Italic">Teucrium</Emphasis> L. species

Total polyphenols, tannins, β-sitosterol, and bitterness values were determined in native and cultivated populations of Teucrium L. species from Croatia (T. arduini L., T. botrys L., T. chamaedrys L., T. flavum L., T. montanum L., T. polium L., and T. scordium L. subsp. scordioides Schreb.). Teucrium species have long been present in folk medicine for diverse medicinal uses, but little is known about polyphenols, phytosterols, and bitter principles. Spectrophotometrically determined contents of total polyphenols (TP) and tannins (T) significantly varied among investigated Teucrium species and were somewhat higher in native populations. The highest TP and T contents were measured in native specimens of T. montanum (TP: 13.68%; T: 3.48%). Scanning densitometry was used for measurements of β-sitosterol levels in plant samples ranged from 0.056% (T. montanum) to 0.129% (T. botrys), and it was not significantly different between native and cultivated specimens of the same plant species. Bitterness values were similar for native and cultivated samples of the same plant species; the highest was measured for T. montanum (15659). The present study suggests that Teucrium species growing in Croatia have potential for cultivation and might be a valuable source of natural bioactive compounds.     

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

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 non‐alkali soil. In contrast, Hemizonia, in the absence of competition, performed significantly better on the non‐alkali 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.     

Capsule Treatments to Enhance Seedling Emergence of Gaura neomexicana ssp. coloradensis

Management of riparian vegetation is difficult because these communities are frequently impacted by herbivores, invasive weeds, and altered hydrologic regimes. Multiple and intertwined factors affecting rare species recruitment are particularly difficult to identify. Gaura neomexicana ssp. coloradensis Munz (Gaura) is a short‐lived perennial forb endemic to riparian areas in mixed‐grass prairies of Wyoming, Nebraska, and Colorado, U.S.A. It became a federally listed threatened species in October 2000. Because the species is a recruitment‐limited monocarpic perennial, we studied the effects of six capsule‐collection dates, a 2‐month cool‐moist stratification, 24‐hr leaching, and 24‐hr imbibition on Gaura seedling emergence. Seedling emergence did not vary with collection date. Capsules collected from Gaura plants grown at the Bridger Plant Materials Center in Montana exhibited greater emergence than capsules harvested from endemic populations near Cheyenne, Wyoming, suggesting that maternal plant growing conditions impact dormancy. Because cool‐moist stratification enhanced seedling emergence of Gaura and leaching did not, sufficient moisture during cool temperatures may be more critical than leaching of germination inhibitors as might occur with normal stream flows. Spring flooding may enhance Gaura recruitment by increasing the availability of riparian sites that are inundated during periods of cool temperatures. If so, hydrologic and climatic regimes must be considered in restoring the unique conditions needed for germination of this rare riparian endemic.     

Biological activities of Teucrium flavum L., Teucrium fruticans L., and Teucrium siculum rafin crude extracts

The genus Teucrium (Lamiaceae) includes 300 species widespread all around the world, which are perennial herbs or shrubs commonly, named germanders. In Italy, Teucrium flavum L., Teucrium fruticans L., and Teucrium siculum Rafin are mostly present in Liguria, Sicily, and Sardegna. Teucrium species are characterized by mono and sesquiterpene hydrocarbons, flavonoids, fatty acid esters, and essential oils. Many species of this genus show antioxidant, antimicrobial, and antifungal activities, rendering them useful as natural preservative ingredients. In view of the interesting biological properties reported for Teucrium spp., in this study we determined the total phenol and flavonoid content of inflorescence extracts of T. flavum L., T. fruticans L., and T. siculum Rafin. In addition, we investigated the in vitro antioxidant and antibacterial activities of inflorescence extracts against pathogenic bacteria. Obtained results demonstrated that extracts had in vitro antioxidant activity and showed antimicrobial ability against Gram-positive and Gram-negative strains albeit with different effectiveness probably due to the different qualitative/quantitative composition of the extract also suggesting that these extracts might be useful in preventing several diseases in which oxidative stress may represent an important pathogenic mechanism.     

Comparison of a common and rare species of Mimosa (Mimosaceae) in Central Brazil

Abstract The aim of this study was to verify differences in the biology of a common widespread species (Mimosa claussenii Benth.) and three rare endemics (Mimosa decorticans Barneby, M. heringeri Barneby, and M. setosissima Taub.). We studied three populations of M. claussenii and one population of each rare species at four localities in central Brazil. We compared the population structure, phenology, fruit set, seed predation, germination, establishment and root/shoot ratio in these six populations. The endemic species occurred in higher densities and smaller individuals were more abundant. When in sympatry, the rare and common species showed a significant negative correlation of density. Mimosa claussenii occurred in drier and rocky environments, whereas M. decorticans and M. setosissima occurred in moister habitats. Rare species had higher levels of fruit set, more viable seeds per individual, and heavier seeds. Mimosa setosissima had the highest level of germination and establishment rate, but did not survive away from its endemism centre. The common species had a higher root/shoot ratio. Overall, the biological aspects studied indicated an advantage in reproductive biology for the rare in relation to the common species. The small geographical range of the rare species may be related to edaphic isolation and climatic changes in the Quaternary.     

Translocation trials confirm specific factors affecting the establishment of three endangered plant species

Summary Experimental translocations of three endangered plants undertaken in South Australia confirmed the impact of specific factors thought to affect the survival and establishment of seedlings of each species. A trial involving Prostanthera eurybioides planted into several different microsites, found microsite to be a critical determinant of survival and growth. Herbivore grazing and weed competition adversely affected survival and growth of Acacia cretacea and Acacia whibleyana translocants, respectively. While these findings may not necessarily extrapolate to all species, common sense suggests that these three factors should be important considerations when planning other plant translocations. For example, attention needs to be given to the exact placement of individuals in relation to suitable edaphic, biotic and climatic factors around the receptor site. Where weeds threaten the population, they need to be controlled either before or at the time of planting. Furthermore, protection of new plantings from herbivores is likely to be crucial, particularly during the first few months after planting.     

Anatomy, palynology and nutlet micromorphology of Turkish endemic Teucrium sandrasicum (Lamiaceae)

In this study, the anatomical features of the leaf and stem, besides the pollen and nutlet characteristics of Teucrium sandrasicum are investigated. T. sandrasicum, belonging to sect. Teucrium, is an endemic perennial herb growing on serpentine around Muğla province. The anatomical studies on T. sandrasicum revealed that the stem shares the general characteristics of the Labiatae family. The leaves clearly exhibit xeromorphy due to features such as the distribution of stomata on the lower surface (hipostomatic), the occurrence of guard cells below the epidermis (xeromorphic type), inrolled margins, thick cuticle layer, thick outer epidermal cell wall, a high density of trichomes and thick palisade layer of the mesophyll. The anatomical studies showed that the upper epidermal cells of the leaf include many spherocrystals. The pollen grains are prolate, medium in size, 3-colpate with verrucate ornamentation. The nutlets are ellipsoid with a reticulate-verrucate surface. The results have proven that T. sandrasicum is different from the other species of the sect. Teucrium because of the branched trichomes on the stem and the lack of eglandular trichomes on the nutlets.     

Tree species distribution in temperate forests is more influenced by soil than by climate

Knowledge of the ecological requirements determining tree species distributions is a precondition for sustainable forest management. At present, the abiotic requirements and the relative importance of the different abiotic factors are still unclear for many temperate tree species. We therefore investigated the relative importance of climatic and edaphic factors for the abundance of 12 temperate tree species along environmental gradients. Our investigations are based on data from 1,075 forest stands across Switzerland including the cold‐induced tree line of all studied species and the drought‐induced range boundaries of several species. Four climatic and four edaphic predictors represented the important growth factors temperature, water supply, nutrient availability, and soil aeration. The climatic predictors were derived from the meteorological network of MeteoSwiss, and the edaphic predictors were available from soil profiles. Species cover abundances were recorded in field surveys. The explanatory power of the predictors was assessed by variation partitioning analyses with generalized linear models. For six of the 12 species, edaphic predictors were more important than climatic predictors in shaping species distribution. Over all species, abundances depended mainly on nutrient availability, followed by temperature, water supply, and soil aeration. The often co‐occurring species responded similar to these growth factors. Drought turned out to be a determinant of the lower range boundary for some species. We conclude that over all 12 studied tree species, soil properties were more important than climate variables in shaping tree species distribution. The inclusion of appropriate soil variables in species distribution models allowed to better explain species' ecological niches. Moreover, our study revealed that the ecological requirements of tree species assessed in local field studies and in experiments are valid at larger scales across Switzerland.     

Morphology and distribution of trichomes in Italian species ofTeucrium sect.Chamaedrys (Labiatae) — a taxonomical evaluation

Micromorphology and distribution of trichomes (both secretory and not) in different parts of plants of the five Italian species belonging toTeucrium sect.Chamaedrys have been studied. These characters neatly evidence the differences between the taxa considered; of particular interest are the observations concerning the dense coverage of peltate hairs on the abaxial face of the leaves ofT. flavum subsp.glaucum and the characters contributing to a better identification ofT. marum andT. subspinosum. The importance of the calyx indumentum as distinctive taxonomical character of the genusTeucrium is confirmed, stressing at the same time the necessity of completing the observations at micromorphological level.     

Germination responses of three grassland species differ between native and invasive origins

The germination stage is critical in plant life-history and is also a key process during the expansion of species’ ranges into new environments. In this study we investigated the germination patterns of three plant species (Achillea millefolium, Hieracium pilosella and Hypericum perforatum) that are invasive to New Zealand (NZ) and native to Central Europe. We asked whether the species show differences in germination temperature requirements, germination speed and maximum germination rates, and thus, whether they display evidence of adaptation to different conditions in the invasive range. Seeds from three populations per species and region were subjected to three different temperature regimes to compare germination rates among origins and across temperature conditions. For Achillea millefolium and Hypericum perforatum, germination rates were significantly higher for invasive NZ provenances than for native German ones. Seeds from invasive populations of all three species displayed increased maximum germination at medium temperature conditions when compared to native populations, which indicates altered germination strategies in the invaded range. Changes in temporal development patterns were most conspicuous for invasive Hieracium pilosella and Hypericum perforatum populations. These findings imply that adaptation in germination patterns towards different climatic conditions in invasive populations has occurred. Our study emphasises the importance of the germination stage during plant invasion and its role in explaining range expansion of these species.     

Assessing and modeling seed germination of Mediterranean wildflowers for low input landscape restoration

Native species are recommended for use in landscape restoration because they adapt well to the local pedo‐climatic conditions. Despite the high biodiversity in the Mediterranean, the use of native plants is hampered by the limited knowledge of their seed germination. This is particularly true for a number of plants which are appropriate for creating species‐rich herbaceous communities. In this study, seeds of 35 species were collected in different roadside and degraded sites in rural and urban areas. Two experiments were carried out to determine the influence of light and thermal conditions on seed germination. In the first experiment, seeds of 17 species were tested at different temperatures (5, 15, and 25°C). At 15°C, seed germination was tested under both dark and light conditions. In the second experiment, the germination of 30 species was tested under alternating temperatures (25/15°C) and dark/light conditions. The responses of the various species differed in relation to thermal levels and light conditions, e.g., Bartsia trixago did not germinate in the dark at constant temperatures (5, 15, and 25°C), while in the light (15°C) and at alternating temperatures (25/15°C) in light and dark conditions, germination was over 60%. In both experiments, Tragopogon porrifolius and Triticum ovatum showed the highest germination rate (≥88%). With the sole exception of Medicago orbicularis, all members of the Fabaceae showed no or low germination. The definition of the germination requirements of some Mediterranean species, highlighted in these experiments, provides useful information for the creation of low input green areas and environmental restoration using these species.     

Nutlet sculpturing of selectedTeucrium species (Lamiaceae): A character of taxonomic significance

Nutlet sculpturing of 23Teucrium species belonging to six sections was studied. The nutlets of analysed species were characterized by the presence of the oil glands of various density. SectionTeucrium is well defined by very densely distributed trichomes and oil glands on nutlets. Trichomes on nutlets were absent in all other species, except inT. marum from sect.Chamaedrys. Sect.Polium is a homogeneous group, distinguished from the other sections. There are some similarities of this sect. with sect.Scordium. Species of sect.Chamaedrys are heterogeneous and overlap according to the surface sculpturing characters with the other sections. The significance of nutlet microcharacters as additional taxonomical markers in the infrageneric classification of the genusTeucrium is discussed.     

Phytosociological and environmental gradients in a sector of the Western Desert of Egypt

Summary The climatic and physiographic features of the Western Desert of Egypt vary gradually from the Mediterranean coast inland. The present study provides an analysis of the gradients exhibited by these environmental variations and their relationships with vegetational gradients and the phytosociological behaviour of species in a sector along the Cairo-Alexandria desert road. The multivariate analyses of the vegetation lead to the recognition of six interrelated vegetational groupings which were distributed along a climatic gradient of increasing aridity, and an edaphic gradient of increasing sandiness and decreasing salinity and level of total phosphorus. These groupings were distinguished into three sets: a set ofConvolvulus-Helianthemum-Artemisia, andHelianthemum-Echiochilon, a set ofAnabasis, andSalsola-Anabasis, and a set ofAsphodelus-Noaea andThymelaea-Anabasis-Noaea groupings. The first set occupies the more arid end of the climatic gradient and the end of the coarse texture, low salinity and low levels of total phosphorus of the edaphic gradient. The second set occupies the opposite end of the edaphic gradient and the middle position of the climatic gradient and the middle position of the climatic gradient, and the third, the middle position of the edaphic gradient and the less arid end of the climatic gradient. Taxonomic nomenclature is according to T?ckholm (1974). The multivariate analyses were carried out using a Burroughs B6700 at the Computer Center of Utah State University, and supported by the U.S. Desert Biome. The authors are indebted to W. Valentine, H. C. Romesburg and K. Marshall for their assistance with data processing.     

Effects of climatic and edaphic factors on arbuscular mycorrhizal fungi in the rhizosphere of Hippophae rhamnoides in the Loess Plateau, China

In order to investigate the effects of climatic and edaphic factors on arbuscular mycorrhizal (AM) fungi in the rhizosphere of Hippophae rhamnoides in the Loess Plateau, spore density, mycorrhizal colonization and gene diversity were analyzed by using the methods of microscopy and polymerase chain reactiondenaturing gradient gel electrophoresis (PCR-DGGE) respectively. The results showed that H. rhamnoides could form strong symbiotic relationships with AM fungi. There existed obvious differences in AM fungal colonization among five sampling sites in the Loess Plateau (P < 0.05). Correlation analysis showed that AM fungal colonization and spore density were closely related with climatic and edaphic factors. 42 different species (band types) were found in the DGGE gel. Based on analysing the position and intensity of AM fungal DGGE bands, the gene diversity indices, including species richness, evenness, Simpsom’s and Shannon-Weiner index, showed significant differences among five sampling sites (P < 0.05). All the AM species could be classified into four groups in the biplot of canonical correspondence analysis (CCA), and each group had various responses to climatic and edaphic factors. Monte Carlo random test indicated that soil available phosphorus (F = 2.26, P = 0.025) and spore density (F = 1.76, P = 0.006) were the dominating factors affecting AM fungal communities. In conclusion, AM fungal colonization and community diversity in the rhizosphere of H. rhamnoides showed obvious spatial heterogeneity among the different areas of the Loess Plateau, and climatic and edaphic conditions were important factors affecting the AM fungal communities. Therefore, screening and application of AM fungal strains in the Loess Plateau need to fully consider the local climatic and edaphic conditions.     

Germination responses of <Emphasis Type="Italic">Erica andevalensis</Emphasis> to different chemical and physical treatments

Erica andevalensis Cabezudo & Rivera is a threatened edaphic endemic species of Andalusia (SW Spain). Under natural conditions, the plants produce a very large number of small seeds (0.3–0.4 mm) but very few seedlings survive. Different treatments (high temperature, cold pre-treatment, nitrogen salts, and gibberellic acid applications) were tested to assess germination patterns in different populations and to determinate the most favorable conditions for germination. Gibberellic acid was provided in five different concentrations from 0 to 400 ppm GA₃, while nitrogen was applied as 10 mM of either KNO₃ or NH₄NO₃. The effect of pH on germination was also tested. The species always showed a low germination rate (6.50–22%) that was not stimulated either by 1 or 4 months in dry cold pre-treatment, nitrogen application, acid pH medium, or by high temperature (80°C for 10 min); although gibberellic acid application (100–400 ppm) significantly enhanced germination. The highest percentage of germination (41.6%) was achieved with a mean germination time to start germination (t ₀) of 7.6 ± 0.54 days when the seeds were subjected to 400 ppm gibberellic acid treatment. The population origin did not have a significant effect on germination percentage.     

Lowland boreal forests characterization in Algonquin Provincial Park relative to beaver (Castor canadensis) foraging and edaphic factors

Beaver (Caster canadensis) foraging and edaphic conditions can modify the vegetational characteristics of woody plant community in lowland boreal forests. Effective management of these areas requires an understanding of the relative contribution of these factors in shaping the woody plant community structure. Our objective was to quantify the effects of herbivory by beavers and edaphic conditions on woody plant community organization of lowland boreal forests surrounding beaver ponds. Woody vegetation and soils were sampled at 15 ponds occupied by beavers and one other pond abandoned by them in southern Algonquin Park, Ontario. We measured spatial variation in plant diversity, foraging rates and sapling recruitment of trees and shrubs along gradients of beaver foraging intensity and soil moisture, P, K, Mg, and pH. Beavers fed preferentially on a small number of deciduous species and the number of cut stems declined sharply with increasing distance from ponds. Conifers increased in relative dominance to deciduous species in the presence of beavers. Plant species richness and stem and basal area diversity peaked at intermediate distances (about 25 m) from ponds. Sapling recruitment by non-preferred species was positively related to foraging intensity. Total stem abundance and basal area and sapling recruitment by four preferred species (Populus tremuloides, Acer rubrum, Acer saccharum and Corylus cornuta) were negatively related to foraging intensity. However, by including Alnus rugosa and Salix bebbiana (also preferred by beavers) these patterns changed, becoming positively related to foraging intensity. There was also a pronounced gradient in soil moisture, which also decreased with distance from ponds. The other measured edaphic variables did not vary consistently with distance from ponds. Sapling recruitment in mesic versus xeric species varied consistently with hydrid conditions along the moisture gradient, such that variation in moisture also could produce the observed pattern of plant diversity. Diversity patterns changed three years after beaver abandonment of a pond, though sapling recruitment patterns in preferred and non-preferred species around the abandoned pond were similar to the occupied ponds. These observations suggest spatial variation in woody plant richness and diversity could be determined by combined effects of both herbivory (disturbance by beavers) and variable responses of different species to edaphic conditions.     

Seed germination and seedling emergence of Euryodendron excelsum H. T. Chang: implications for species conservation and restoration

Euryodendron excelsum H. T. Chang is a critically endangered plant from the family Theaceae that is endemic to China. It is now present in only one remnant population in a very narrow range and with a highly isolated and fragmented distribution pattern. The species is distributed close to the local villages and faces extinction because of the high level of anthropogenic disturbance. Thus, conservation and restoration of this species is urgent. The species reproduces by seed, but its germination requirements and seedling emergence are rarely understood. In this study, the germination requirements, desiccation tolerance and seedling emergence of the species were studied under controlled laboratory conditions. The results indicated that seeds of E. excelsum were non‐dormant. Optimal temperatures for germination were 15°C to 25°C; the germination percentage decreased and the mean germination time increased at high temperature. Seed germination was inhibited in the dark, suggesting that the seeds were positive photoblastic. Water stress also significantly inhibited germination percentage; no seeds germinated at 15% polyethylene glycol 6000. The fresh seeds had moderate moisture content of 28.6% and showed strong tolerance of dehydration. Thus, the seeds of E. excelsum tended to be orthodox. Seeds on the soil surface had the highest emergence percentage, which declined with depth of burial. Soil types significantly affected seedling emergence; seeds had higher emergence percentage in sandy soil than in mixed soil and clayed soil. Our study demonstrated that ex situ conservation and reintroduction of E. excelsum using seedling propagation from seeds is feasible.     

Quantitative prediction of the distribution and abundance of Vaccinium myrtillus with climatic and edaphic factors

Question: Can the distribution and abundance of Vaccinium myrtillus be reasonably predicted with soil nutritional and climatic factors? Location: Forests of France. Methods: We used Braun‐Blanquet abundance/dominance information for Vaccinium myrtillus on 2905 forest sites extracted from the phyto‐ecological database EcoPlant, to characterize the species ecological response to climatic and edaphic factors and to predict its cover/abundance at the national scale. The link between cover/abundance of the species and climatic (65 monthly and annual predictors concerning temperature, precipitation, radiation, potential evapotranspiration, water balance) and edaphic (two predictors: soil pH and C:N ratio) factors was investigated with proportional odds models. We evaluated the quality of our model with 9830 independent relevés extracted from Sophy, a large phytosociological database for France. Results: In France, Vaccinium myrtillus is at the southern limit of its European geographic range and three environmental factors (mean annual temperature, soil pH and C:N ratio) allow prediction of its distribution and abundance in forests with high success rates. The species reveals a preference for colder sites (especially mountains) and nutritionally poor soils (low pH and high C:N ratio). A predictive map of its geographic range reveals that the main potential habitats are mountains and northwestern France. The potential habitats with maximal expected abundance are the Vosges and the Massif central mountains, which are both acidic mountains. Conclusions: Complete niche models including climate and soil nutritional conditions allow an improvement of the spatial prediction of plant species abundance at a broad scale. The use of soil nutritional variables in distribution models further leads to an improvement in the prediction of plant species habitats within their geographical range.     

Germination responses to GA3 and short‐time chilling of three endemic species: Tripleurospermum pichleri,Cirsium leucopsis and Senecio olympicus (Asteraceae)

In the present study, the germination characteristics of three endemic species from Turkey, Tripleurospermum pichleri (Boiss.) Bornm., Cirsium leucopsis D.C and Senecio olympicus Boiss. (Asteraceae), were investigated. Germination was studied for fresh seeds, for seeds subjected to short‐time chilling (15 days, moist +4°C), to GA₃ (100, 150 and 250 ppm) and a combination of chilling and GA₃; in all cases seeds were incubated either at 20/10°C day/night with light daytime or at 20°C in darkness with daily short‐time dim light (DSDL). In C. leucopsis seeds, all GA₃ treatments enhanced the final germination percentages. The mean germination time (MGT) of C. leucopsis was lower under DSDL than with photoperiod. The chilling treatment with GA₃ in DSDL significantly increased germination in S. olympicus seeds (from 45 to 87%). Germination increased to 55% in T. pichleri by chilling under photoperiod compared with 32% by chilling followed by DSDL. In conclusion, these three co‐existing endemic Asteraceae species have different germination behaviours; something that should be taken into account for ex situ propagation. However, an efficient way to germinate all species is to use 250 ppm GA₃ and 20/10°C with photoperiod.     

Influence of Environmental Factors on Essential Oil Variability in Origanum compactum Benth. Growing Wild in Morocco

The present study aimed to evaluate the influence of environmental factors on essential oils (EOs) composition of Origanum compactum populations sampled all over the distribution area of the species in Morocco, and to determine the extent of the chemical profiles throughout the geographical distribution of the species. The chemical compositions were submitted to canonical correlation analysis and canonical discriminant analysis that indicated a significant relationship between oil components and some environmental factors. According to their chemical composition and edapho‐climatic characteristics, two major groups of populations were differentiated. The first group was composed of samples growing in regions with humid climate, clayey, sandy, and alkaline soils. These samples showed high thymol, α‐terpineol, linalool, and carvacryl methyl oxide content. The second group consisted of plants belonging to semi‐arid climate, and growing at high altitudes and silty soils. These samples were characterized by high carvacrol, α‐thujene, α‐terpinene, and myrcene content. However, populations exposed to sub‐humid climate, appeared less homogeneous and belong mainly either to the first or second group. A significant correlation between some edaphic factors (pH, K₂O content, soil texture) and the EOs yield of O. compactum plants was evidenced. In spite of the correlation obtained for the oil composition with edapho‐climatic factors and the variance explained by the environmental data set, the observed EO diversity might be also genetically determined.