Major plant communities of the Carson Desert (Nevada), North America's coldest and driest desert

This paper describes the vegetation of the Carson Desert (Nevada, USA) based on a phytosociological analysis of its major plant associations, as determined by the Braun-Blanquet method. Diagnostic tables, climatic, edaphic, and biogeographical data were used to establish floristic affinities among identified plant communities and to interpret their distributions in zonal gradients. Their syntaxonomic positions in the classes Allenrolfeetea occidentalis and Artemisio tridentatae–Juniperetea osteospermae, and in the new class Sarcobatetea vermiculati were also established. Three associations (Atriplici confertifoliae–Sarcobatetum baileyi, Atriplici canescentis–Psorothamnetum polydenii, and Suaedo moquinii–Sarcobatetum vermiculati) are described here for the first time along with the order Sarcobatetalia vermiculati and the alliance Sarcobation vermiculati.     

Zonal plant distribution and edaphic and micrometeorological conditions on a coastal sand dune

Some edaphic and meteorological conditions were examined to detect environmental gradients from shoreline to inland at the Kado-ori coast, Ibaraki, Japan, in 1989. Zonal distribution patterns of coastal dune plant species, including three ubiquitous perennials,Calystegia soldanella, Carex kobomugi andIschaemum anthephoroides, were described in relation to the environmental gradients. Environmental gradients were found in water availability, evaporative demand and soil-water salinity. Water availability, evaluated by thickness of capillary water layer, increased from 10 cm at 20 m to 48 cm at 85 m from the shoreline, reflecting the percentage of fine sand. Evaporative demand, which was evaluated by the evaporation rate from a wet black filter paper, decreased with increasing distance from the shoreline. Soil-water salinity was lowest (15 mmol/L) at 85 m from the shoreline and highest (90 mmol/L) at 30m. On the coast,C. soldanella, a salt-tolerant perennial, was distributed mainly in the environmentally harsh area 40–60 m from the shoreline.Ischaemum anthephoroides andC. kobomugi, less salt-tolerant perennials, occurred mainly 70–80 m from the shoreline, where environmental conditions were more hospitable.     

Distribution of the plant communities in Tihamah coastal plains of Jazan region,Saudi Arabia

The present study provides quantitative estimates of the vegetation structure and distribution of the plant communities in Tihamah coastal plains of Jazan region. The factors affecting the species distribution and the correlations between the vegetational gradients and the edaphic variables were discussed. Eight major community types constitute the major part of the natural vegetation of the study area and are dominated by nine perennials: Ziziphus spina-christi (L.) Willd, Calotropis procera (Wild) R. Br., Leptadenia pyrotechnica (Forssk.) Decne., Suaeda monoica Forssk., Panicum turgidum Forssk., Salvadora persica L., Acacia tortilis (Forssk) Hayne, Tamarix aphylla (L.) Karst. and Cyperus conglomeratus Rottb.The results of this study confirm that the study area is a subtropical desert and belongs floristically to the Sudanian territory and also that therophytes are the most frequent life-form in this region.Analysis of the correlation between the vegetational gradients and the edaphic factors showed that soil pH, moisture, electrical conductivity, organic carbon, calcium carbonate, bicarbonate, soil cations: sodium, potassium, calcium, and the sodium adsorption ratio are the main operating edaphic factors in the area.     

Pollen assemblages as paleoenvironmental proxies in the Florida Everglades

Analysis of 170 pollen assemblages from surface samples in eight vegetation types in the Florida Everglades indicates that these wetland sub-environments are distinguishable from the pollen record and that they are useful proxies for hydrologic and edaphic parameters. Vegetation types sampled include sawgrass marshes, cattail marshes, sloughs with floating aquatics, wet prairies, brackish marshes, tree islands, cypress swamps, and mangrove forests. The distribution of these vegetation types is controlled by specific environmental parameters, such as hydrologic regime, nutrient availability, disturbance level, substrate type, and salinity; ecotones between vegetation types may be sharp. Using R-mode cluster analysis of pollen data, we identified diagnostic species groupings; Q-mode cluster analysis was used to differentiate pollen signatures of each vegetation type. Cluster analysis and the modern analog technique were applied to interpret vegetational and environmental trends over the last two millennia at a site in Water Conservation Area 3A. The results show that close modern analogs exist for assemblages in the core and indicate past hydrologic changes at the site, correlated with both climatic and land-use changes. The ability to differentiate marshes with different hydrologic and edaphic requirements using the pollen record facilitates assessment of relative impacts of climatic and anthropogenic changes on this wetland ecosystem on smaller spatial and temporal scales than previously were possible.     

Biogeography of salt marsh plant zonation on the Pacific coast of South America

Aim

The aim of this study was to investigate the biogeography of plant zonation in salt marshes on the Pacific coast of South America; to examine whether salt marsh plant zonation varies with latitude; and to explore the relative importance of climatic, tidal, edaphic and disturbance factors in explaining large‐scale variation in salt marsh plant community structure.

Location

A 2,000‐km latitudinal gradient on the Pacific coast in Chile, with a climate shift from hyper‐arid at low to hyper‐humid at high latitudes.

Methods

Plant zonation was quantified in field surveys of ten marshes. Climate, tidal regimes, edaphic factors and disturbances (tsunami and rainfall floods) were determined. We used multivariate analyses to explore their relative importance in explaining large‐scale variation in salt marsh plant community structure.

Results

Across latitude, marshes were dominated by distinct plant communities in different climate regions, especially at the extreme dry and wet latitudes. Intertidal plant species zonation was present in hyper‐arid and semi‐arid climates, but not in arid, humid and hyper‐humid climates. Latitudinal variation in low‐marsh plant communities (regularly flooded at high tide) was largely a function of precipitation, while at high marshes (never flooded at high tide) latitudinal variation was explained with precipitation, temperature, tidal cycles, soil salinity and disturbances.

Main conclusions

Salt marshes on the Pacific coast of South America belong to Dry Coast and Temperate biogeographic types. Salt marsh plant zonation varies across latitude, and is explained by climatic, tidal, edaphic and disturbance factors. These patterns appear to be mechanistically explained by extrapolating experimentally generated community assembly models and have implications for predicting responses to climate change.     

Karyotypic study of titi monkeys,Callicebus moloch brunneus

A karyotypic study on a subspecies of the dusky titi,Callicebus moloch brunneus, was carried out and a third karyotype ofC. moloch was discovered. The chromosome number of this subspecies is 48. The autosomes consist of 5 subtelocentric, 5 submeta- or metacentric, and 13 acrocentric chromosome pairs. The X chromosome and the Y chromosome are submetacentric and metacentric, respectively. A comparative study with other subspecies of theC. moloch group (i.e.,C. m. cupreus andC. m. ornatus with 2n=46 andC. m. donacophilus with 2n=50) suggests that the karyotype ofbrunneus occupies a position intermediate between the two other karyotypes ofC. moloch, but nearer to that of 2n=50. The presumed total differences betweenbrunneus andcupreus comprise one Robertsonian rearrangement, one centromeric transposition and four pericentric inversions, and those betweenbrunneus anddonacophilus involve one translocation or breakage (possibly corresponding to two events, that is, one Robertsonian rearrangement and one centromeric transposition).     

Phylogenetic analysis ofUlmaceae

A phylogenetic analysis of theUlmaceae, Cannabaceae, Barbeyaceae, andBroussonetia of theMoraceae produced nine equally parsimonious trees with 127 steps. TheUlmoideae (Ulmaceae, sensuGrudzinskaya) are a monophyletic group and distinct from theCeltidoideae. The genusAmpelocera occupies an isolated taxonomic position among the celtidoids. The similarity ofAmpelocera to the fossil celtidoid flowerEoceltis of North America suggests thatAmpelocera posesses an archaic suite of characters, and occupies a primitive position among the celtidoids, theCannabaceae and theMoraceae. The relationships among the other celtidoid taxa,Cannabaceae, andBroussonetia are problematic. TheCannabaceae andBroussonetia of theMoraceae are nested within the celtidoids suggesting that this is a paraphyletic group. The close, but unresolved, relationship of the celtidoids to theMoraceae andCannabaceae observed in this analysis, and the appearance of the celtidoids in the fossil record prior to the ulmoids suggests that the evolutionary relationship of the ulmoids and celtidoids may be more distant than current taxonomic treatments reflect.     

Chromosome numbers of Western Australian species ofVillarsia (Menyanthaceae)

Chromosome numbers are reported for eight of the nine Western AustralianVillarsia species.Villarsia albiflora, V. calthifolia, V. capitata, V. congestiflora, V. lasiosperma, V. latifolia, andV. violifolia are diploid with n=9. Five populations ofV. parnassiifolia are diploid and three are tetraploid (n=18). The morphological, ecological, and breeding-system diversity of the Western Australian species is largely not associated with the tetraploidy or hexaploidy that characterizes otherVillarsia species in eastern Australia and South Africa. The majority of Western AustralianVillarsia species are restricted to the high rainfall zone of southwestern Western Australia, where favorable climatic and edaphic conditions may have existed since mid-late Tertiary times.     

基于盐分梯度的黑河中游湿地植物多样性及其与土壤因子的关系

湿地植物多样性的研究对维持湿地生态系统完整性和稳定性有着重要意义。以黑河中游湿地为研究对象,基于野外采样数据和不同盐分梯度植物群落多样性指数,重点分析不同盐分梯度植物多样性变化及其与土壤因子关系。结果表明:黑河中游湿地植物组成比较丰富,共出现植物30科71属102种;随土壤盐分梯度增加,植物群落组成发生显著变化,Margalef丰富度指数(R)和Shannon-Weiner多样性指数(H)均减小,说明研究区植物多样性随盐分增加而减少;不同盐分梯度影响植物多样性的土壤因子存在差异,低盐梯度是pH、速效钾和全氮,中盐梯度是pH、速效磷和速效钾,高盐梯度是有机质、全磷、速效钾和速效氮。该研究结果对于认识不同盐分梯度下影响植物多样性的主要土壤因子具有重要意义,同时对黑河中游湿地植物多样性的有效管理和维持具有一定的参考价值。     

Community structure on unusual habitat islands: quartz-fields in the Succulent Karoo,South Africa

Quartz fields are edaphically arid, azonal habitats occurring under different macroclimatic conditions in several arid regions of southern Africa. They are the exclusive home of 142 plant species of which ca. 70% are local or regional endemics. This paper is an analysis of the quartz-field floras and growth form-soil relationships in two quartz field regions: the Knersvlakte in the Namaqualand-Namib Domain of the Succulent Karoo, and the western Little Karoo in the Southern Karoo Domain. The Knersvlakte supported 52 quartz-field specialists of which 39 were endemic to the region. Corresponding data for the Little Karoo were 11, and 10 species, respectively. In both regions, the average canopy cover on the quartz-field relevés was ca. 8%, and more than half of this comprised contracted, succulent nanochamaephytes. Cover and vegetation stature were markedly higher on adjacent zonal habitats. Quartz fields in both regions supported a similar array of compact, subglobose and subterranean nanochamaephytes, as evidenced by convergent patterns in two distantly related genera (Argyroderma N. E. Brown and Gibbaeum (Haworth) N. E. Brown, both Mesembryanthemaceae), endemic to the Knersvlakte and largely restricted to the Little Karoo, respectively. Analyses of vegetational and edaphic data of quartz fields and adjacent, zonal habitats were carried out using multivariate direct gradient analysis (Canonical Correspondence Analysis) in order to identify those factors that control the peculiar composition of growth forms on quartz fields. The results revealed highly similar patterns of growth form composition in relation to similar edaphic gradients in both regions. In general, the soils of quartz fields were shallower compared to those of adjacent zonal habitats. In both regions, two different groups of quartz-field edaphic habitats, representing extremes of a continuum, were identified. Group 1 was characterized by high salt content, neutral to slightly acid soil pH, and low stone content. Group 2 was characterized by low salt content, low soil pH, and high stone content. Group 1 quartz fields are the most edaphically arid habitats and support the highest relative cover and diversity of subglobose and subterranean chamaephytes. The combination of reduced competition from larger growth forms, shallow soils and high soil salinity, represents a regionally unusual selective regime. Some succulent lineages in the Mesembryanthemaceae have undergone diversification which has resulted in the fine-scale discrimination of subtle edaphic gradients within the saline quartz-patch habitats. Reliable seasonal rainfall and reduced thermal stress have also played a role in the evolution of quartz patch specialists.     

Water availability shapes edaphic and lithic cyanobacterial communities in the Atacama Desert

In the Atacama Desert, cyanobacteria grow on various substrates such as soils (edaphic) and quartz or granitoid stones (lithic). Both edaphic and lithic cyanobacterial communities have been described but no comparison between both communities of the same locality has yet been undertaken. In the present study, we compared both cyanobacterial communities along a precipitation gradient ranging from the arid National Park Pan de Azúcar (PA), which resembles a large fog oasis in the Atacama Desert extending to the semiarid Santa Gracia Natural Reserve (SG) further south, as well as along a precipitation gradient within PA. Various microscopic techniques, as well as culturing and partial 16S rRNA sequencing, were applied to identify 21 cyanobacterial species; the diversity was found to decline as precipitation levels decreased. Additionally, under increasing xeric stress, lithic community species composition showed higher divergence from the surrounding edaphic community, resulting in indigenous hypolithic and chasmoendolithic cyanobacterial communities. We conclude that rain and fog water, respectively, cause contrasting trends regarding cyanobacterial species richness in the edaphic and lithic microhabitats.     

Strong relationships between vegetation and two perpendicular climate gradients high on a tropical mountain in Hawai‘i

Aim We compared vegetation patterns at high elevation on a tropical mountain with edaphic properties and position along climate gradients to examine this landscape’s potential sensitivity to climate change. Location Our study covers the cloud forest, the ecotone at the cloud forest’s upper limit, and the alpine grassland, on the north‐east corner of windward Haleakalā, Hawai‘i. The study area brackets the mean trade wind inversion (TWI), encompasses a perpendicular, east–west precipitation gradient and includes multiple edaphic contexts. Methods We collected vegetation structure and composition data in 134 plots from 1900 to 2400 m elevation, stratified east to west. We used classification trees to compare species assemblage groups with spatial (elevation, easting, aspect) and edaphic (substrate age, texture, degree slope) variables derived from a 10‐m digital elevation model and a digital geological map. Results The forest line was physiognomically sharp, and a Shipley–Keddy test showed that species distributional limits were aggregated there. Forest line elevation was not consistent, but dropped nearly 200 m from east to west. Indicator taxa for positions above or below the forest line varied from east to west. Hierarchical clustering identified species assemblage groups with significantly different composition that were distributed across the TWI and/or along east–west climate gradients. Classification trees showed that edaphic properties were not well associated with species assemblage groups, but position along two perpendicular climate gradients was. Compositional turnover was detected along both elevational and east–west gradients. Turnover of the cloud forest’s epiphytic community was particularly pronounced across east–west gradients. Lichen abundance was significantly higher at the drier end of the east–west moisture gradient, and bryophyte abundance was higher at the wetter end. Main conclusions Modern spatial patterns suggest that this landscape will respond to changes in moisture balance through changes in species assemblage and structure, especially at the ecotone. Furthermore, ecotone response to climate change may vary from east to west because of differences in species‐specific constraints or climatic context.     

The response of certainTrifolium spp. to calcium in sand culture

Summary The response to calcium ofTrifolium incarnatum, T. pratense, T. repens andT. hybridum was determined over the range 4 to 128 ppm calcium in sand culture.T. incarnatum showed the greatest response to calcium and was severely affected by low levels of calcium.T. hybridum was the least responsive to calcium and showed no significant response over the range tested, although a gradual increase in yield with increasing calcium was apparent. The responses ofT. pratense andT. repens were intermediate and differed significantly from those of bothT. incarnatum andT. hybridum. There was no significant difference between the response ofT. pratense andT. repens.The results are considered in the light of the ecologically observed edaphic tolerances of the species, and it is concluded that there is a marked relationship between response to calcium and edaphic tolerance of the species.In view of the differences in response to calcium recently demonstrated within the speciesT. repens, the magnitude of the differences between species shown here may not strictly apply to all varieties or populations of those species.     

Antigenic affinities of the root-nodule bacteria of legumes

Antisera prepared against 58 strains of root-nodule bacteria and against 16 strains belonging to the genusAgrobacterium were tested against 113 strains ofRhizobium, 20 strains ofAgrobacterium and 20 strains of other, possibly related, bacteria.Three serologically distinct groups of root-nodule bacteria were noted: (1)Rh. trifolii, Rh. leguminosarum andRh. phaseoli; (2)Rh. lupini, Rh. japonicum andRhizobium spp.; (3)Rh. meliloti. Strains ofRh. meliloti showed serological affinities withA. radiobacter andA. tumefaciens. All groups showed wider flagellar than somatic agglutination, and many different serotypes were apparent.The groupings obtained from this investigation are compared with those derived from other taxonomic studies, and the use of serological methods in rhizobial classification is discussed.     

Rapid Development of Adaptive,Climate-Driven Clinal Variation in Seed Mass in the Invasive Annual Forb Echium plantagineum L.

We examined adaptive clinal variation in seed mass among populations of an invasive annual species, Echium plantagineum, in response to climatic selection. We collected seeds from 34 field populations from a 1,000 km long temperature and rainfall gradient across the species'' introduced range in south-eastern Australia. Seeds were germinated, grown to reproductive age under common glasshouse conditions, and progeny seeds were harvested and weighed. Analyses showed that seed mass was significantly related to climatic factors, with populations sourced from hotter, more arid sites producing heavier seeds than populations from cooler and wetter sites. Seed mass was not related to edaphic factors. We also found that seed mass was significantly related to both longitude and latitude with each degree of longitude west and latitude north increasing seed mass by around 2.5% and 4% on average. There was little evidence that within-population or between-population variation in seed mass varied in a systematic manner across the study region. Our findings provide compelling evidence for development of a strong cline in seed mass across the geographic range of a widespread and highly successful invasive annual forb. Since large seed mass is known to provide reproductive assurance for plants in arid environments, our results support the hypothesis that the fitness and range potential of invasive species can increase as a result of genetic divergence of populations along broad climatic gradients. In E. plantagineum population-level differentiation has occurred in 150 years or less, indicating that the adaptation process can be rapid.     

Numerical analysis of the taxonomical status ofCallithrix kuhli based on measurements of the postcanine dentition

The postcanine dentition ofCallithrix geoffroyi, Callithrix penicillata, andCallithrix kuhli was compared metrically to determine whetherC. kuhli is a hybrid population ofC. geoffroyi andC. penicillata or not. Many measurements showed significant differences (p<0.01 orp<0.05) among the three marmosets. The dental variability inC. kuhli was not greater than those inC. geoffroyi andC. penicillata. Based on canonical analysis, the three marmosets are discriminated, andC. kuhli did not occupy a middle position betweenC. geoffroyi andC. penicillata on the first two canonical axes. In the projection of the first two principal components,C. penicillata tended to be distinguished fromC. geoffroyi andC. kuhli, andC. kuhli does not exhibit intermediacy betweenC. geoffroyi andC. penicillata. The present statistical analysis failed to provide evidence thatC. kuhli constitutes a population hybridized fromC. geoffroyi andC. penicillata, although the three marmosets were discriminated from each other. This may provide support for the hypothesis thatC. kuhli is not a hybrid population ofC. geoffroyi andC. penicillata but a distinct species.     

Middle to Late Holocene vegetation history of the Upper Engadine (Swiss Alps): the role of man and fire

To reconstruct the vegetation and fire history of the Upper Engadine, two continuous sediment cores from Lej da Champfèr and Lej da San Murezzan (Upper Engadine Valley, southeastern Switzerland) were analysed for pollen, plant macrofossils, charcoal and kerogen. The chronologies of the cores are based on 38 radiocarbon dates. Pollen and macrofossil data suggest a rapid afforestation with Betula, Pinus sylvestris, Pinus cembra, and Larix decidua after the retreat of the glaciers from the lake catchments 11,000 cal years ago. This vegetation type persisted until ca. 7300 cal b.p. (5350 b.c.) when Picea replaced Pinus cembra. Pollen indicative of human impact suggests that in this high-mountain region of the central Alps strong anthropogenic activities began during the Early Bronze Age (3900 cal b.p., 1950 b.c.). Local human settlements led to vegetational changes, promoting the expansion of Larix decidua and Alnus viridis. In the case of Larix, continuing land use and especially grazing after fire led to the formation of Larix meadows. The expansion of Alnus viridis was directly induced by fire, as evidenced by time-series analysis. Subsequently, the process of forest conversion into open landscapes continued for millennia and reached its maximum at the end of the Middle Ages at around 500 cal b.p. (a.d. 1450).     

Differentiation of acidophilic thiobacilli by cell density in renografin gradients

Thiobacillus acidophilus andT. ferrooxidans were separated by centrifugation on the basis of their cell density in Renografin gradients. For both species, growth history was the largest factor influencing cell density. Density was greatest forT. acidophilus andT. ferrooxidans grown with tetrathionate, followed byT. acidophilus grown with glucose.T. ferrooxidans grown with ferrous sulfate was the least dense.T. acidophilus was isolated from iron-grownT. ferrooxidans by separation in a Renografin gradient. Plasmid patterns ofT. acidophilus andT. ferrooxidans were used to confirm the separation of the two species in mixed gradients.     

Post-glacial changes in spatial patterns of vegetation across southern New England

Aim We analysed lake‐sediment pollen records from eight sites in southern New England to address: (1) regional variation in ecological responses to post‐glacial climatic changes, (2) landscape‐scale vegetational heterogeneity at different times in the past, and (3) environmental and ecological controls on spatial patterns of vegetation. Location The eight study sites are located in southern New England in the states of Massachusetts and Connecticut. The sites span a climatic and vegetational gradient from the lowland areas of eastern Massachusetts and Connecticut to the uplands of north‐central and western Massachusetts. Tsuga canadensis and Fagus grandifolia are abundant in the upland area, while Quercus, Carya and Pinus species have higher abundances in the lowlands. Methods We collected sediment cores from three lakes in eastern and north‐central Massachusetts (Berry East, Blood and Little Royalston Ponds). Pollen records from those sites were compared with previously published pollen data from five other sites. Multivariate data analysis (non‐metric multi‐dimensional scaling) was used to compare the pollen spectra of these sites through time. Results Our analyses revealed a sequence of vegetational responses to climate changes occurring across southern New England during the past 14,000 calibrated radiocarbon years before present (cal yr bp ). Pollen assemblages at all sites were dominated by Picea and Pinus banksiana between 14,000 and 11,500 cal yr bp ; by Pinus strobus from 11,500 to 10,500 cal yr bp ; and by P. strobus and Tsuga between 10,500 and 9500 cal yr bp . At 9500–8000 cal yr bp , however, vegetation composition began to differentiate between lowland and upland sites. Lowland sites had higher percentages of Quercus pollen, whereas Tsuga abundance was higher at the upland sites. This spatial heterogeneity strengthened between 8000 and 5500 cal yr bp , when Fagus became abundant in the uplands and Quercus pollen percentages increased further in the lowland records. The differentiation of upland and lowland vegetation zones remained strong during the mid‐Holocene Tsuga decline (5500–3500 cal yr bp ), but the pattern weakened during the late‐Holocene (3500–300 cal yr bp ) and European‐settlement intervals. Within‐group similarity declined in response to the uneven late‐Holocene expansion of Castanea, while between‐group similarity increased due to homogenization of the regional vegetation by forest clearance and ongoing disturbances. Main conclusions The regional gradient of vegetation composition across southern New England was first established between 9500 and 8000 cal yr bp . The spatial heterogeneity of the vegetation may have arisen at that time in response to the development or strengthening of the regional climatic gradient. Alternatively, the differentiation of upland and lowland vegetation types may have occurred as the climate ameliorated and an increasing number of species arrived in the region, arranging themselves in progressively more complex vegetation patterns across relatively stationary environmental gradients. The emergence of a regional vegetational gradient in southern New England may be a manifestation of the increasing number of species and more finely divided resource gradient.     

Soil salinity and pH in Japanese mangrove forests and growth of cultivated mangrove plants in different soil conditions

Soil conditions of mangrove forests in southern Japan were found to correlate largely with zonal distributions of the species.Kandelia candel grew in soils with low salinity and low pH,Avicennia marina, Rhizophora stylosa andSonneratia alba in soils with high salinity and high pH, andBruguiera gymnorrhiza in soil with a wide range of pH but limited range of salinity.Lumnitzera racemosa colonized soil with a wide range of pH and medium salinity. Seedlings ofKandelia candel, Bruguiera gymnorrhiza andRhizophora stylosa were planted in soils with differing salinity and pH. Optimum seedling growth ofKandelia, Bruguiera andRhizophora occurred when plants were cultivated in soils similar to those of their natural habitats, suggesting that growth of mangrove species and their zonal distributions were regulated by salinity and soil pH.