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In the age of big data, scientific progress is fundamentally limited by our capacity to extract critical information. Here, we map fine-grained spatiotemporal distributions for thousands of species, using deep neural networks (DNNs) and ubiquitous citizen science data. Based on 6.7 M observations, we jointly model the distributions of 2477 plant species and species aggregates across Switzerland with an ensemble of DNNs built with different cost functions. We find that, compared to commonly-used approaches, multispecies DNNs predict species distributions and especially community composition more accurately. Moreover, their design allows investigation of understudied aspects of ecology. Including seasonal variations of observation probability explicitly allows approximating flowering phenology; reweighting predictions to mirror cover-abundance allows mapping potentially canopy-dominant tree species nationwide; and projecting DNNs into the future allows assessing how distributions, phenology, and dominance may change. Given their skill and their versatility, multispecies DNNs can refine our understanding of the distribution of plants and well-sampled taxa in general. By modelling the distribution of the entire Swiss flora using deep learning and citizen science data, this study demonstrates a method that predicts flowering phenology and potentially dominant tree species more accurately than commonly used approaches. This approach could enable investigation of understudied aspects of ecology and refine our understanding of plant distributions. [ABSTRACT FROM AUTHOR]

The influence of the Intertropical Convergence Zone (ITCZ) in the emerging South Atlantic region during the late Aptian (Early Cretaceous) is reflected in the spatio-temporal distribution of plant communities recorded in eight Brazilian sedimentary basins. The distribution of the bioclimatic groups of hygrophytes, hydrophytes, tropical lowland flora, upland flora, and xerophytes was quantified using pollen and spores. A predominance of xerophytes from the tropical xerophytic shrubland biome characterized the pre-evaporitic, evaporitic, and post-evaporitic paleoclimatic phases, in particular the evaporitic phase. The region experienced humidity events in the pre-evaporitic and post- evaporitic phases, especially near the paleoequator, where the tropical rainforest biome with two phytophysiognomies (lowland and montane rainforests) prevailed. Increasing humidity had a positive effect on plant diversity. [ABSTRACT FROM AUTHOR]

This study brings insight into interpreting forest structural diversity and explore the classification of individuals according to the distribution of the neighbours in natural forests. Natural forest communities with different latitudes and distribution patterns in China were used. Each tree and its nearest neighbours form a structural unit. Random structural units (or random trees) in natural forests were divided into different sub-types based on the uniform angle index (W). The proportions of different random structural units were analysed. (1) There are only two types of random structural units: type R1 looks similar to a dumbbell, and type R2 looks similar to a torch. These two random structural units coexist in natural forests simultaneously. (2) The proportion of type R1 is far less than that of R2, is only approximately 1/3 of all random structural units or random trees; R2 accounts for approximately 2/3. Furthermore, the proportion of basal area presents the same trend for both random structural units and random trees. R2 has approximately twice the basal area of R1. Random trees (structural units) occupy the largest part of natural forest communities in terms of quantity and basal area. Meanwhile, type R2 is the largest part of random trees (structural units). This study finds that the spatial formation mechanism of natural forest communities which is of great significance to the cultivation of planted forests. [ABSTRACT FROM AUTHOR]

Levins's asymmetrical α index quantifies between species overlap over resources more realistically than similar-purpose single-value indices. The associated community-wide $$\bar \alpha$$ index expresses the degree of 'species packing'. Both indices were formulated upon competing animal (i.e., mobile) organisms and are independent of population densities. However, overlap over resources for nonmobile organisms such as plants may have an impact even below carrying capacity. The proposed $$\hat \alpha$$ index, based on Levins's α index, quantifies spatial overlap for plants integrating information on species spatial distribution and crowding conditions. The $$\hat \alpha$$ index is specifically designed for plant distribution data collected in discrete plots with density expressed as percent coverage (%cover) of substratum. We also propose a community-wide $${\hat \alpha_{\text{c}}}$$ index, conceptually analogous to $$\bar \alpha$$ , but furnished with a measure of dispersion ( se $${\hat \alpha_{\text{c}}}$$ ). Species importance within the community is inferred from comparisons of pairwise $$\hat \alpha$$ 's with $${\hat \alpha_{\text{c}}}$$ . The $$\hat \alpha$$ and $${\hat \alpha_{\text{c}}}$$ indices correlate closely and exponentially with plant density, and correct apparent over- and underestimations of interaction intensity at low and very high crowding by Levins's α and $$\bar \alpha$$ , respectively. Index application to aquatic plant communities gave results consistent with within-community and general ecological patterns, suggesting a high potential of the proposed $$\hat \alpha$$ and $${\hat \alpha_{\text{c}}}$$ indices in basic and applied macrophyte ecological studies and management. [ABSTRACT FROM AUTHOR]

Background and Aim: Biotic and abiotic factors contribute in shaping the distribution through the soil profile of elements released by mineral weathering; among them, leaching and biocycling dominate in temperate environments. We evaluated if the intensity of leaching and biocycling of nutrients can be modulated by element deficiencies linked to the abundance of serpentine in the soil parent material, i.e. if the most deficient elements are more efficiently retained. Methods: We selected twelve poorly developed soils from Northern Italian beech stands, with variable amounts of serpentinites in the parent material, and determined total and exchangeable Ca, Mg and K, as well as an index of abundance of serpentine minerals. Results: The total element content depended on the abundance of serpentines, while only exchangeable Mg was related to the parent material. The vertical trend of Ca and K indicated the role of biocycling in all soils, but the relative availability of Ca (ratio between exchangeable and total content) was much higher in the top horizons of serpentine-rich soils. Conclusions: The different element availability among soils suggested that the vertical distribution of available elements was linked to the parent material and that losses were limited in serpentine-rich soils, probably because plants take up the deficient elements as soon as they are released from litter and thus limit their leaching in deeper soil horizons. [ABSTRACT FROM AUTHOR]

Climate change is driving latitudinal and altitudinal shifts in species distribution worldwide, leading to novel species assemblages. Lags between these biotic responses and contemporary climate changes have been reported for plants and animals. Theoretically, the magnitude of these lags should be greatest in lowland areas, where the velocity of climate change is expected to be much greater than that in highland areas. We compared temperature trends to temperatures reconstructed from plant assemblages (observed in 76,634 surveys) over a 44-year period in France (1965-2008). Here we report that forest plant communities had responded to 0.54?°C of the effective increase of 1.07?°C in highland areas (500-2,600?m above sea level), while they had responded to only 0.02?°C of the 1.11?°C warming trend in lowland areas. There was a larger temperature lag (by 3.1 times) between the climate and plant community composition in lowland forests than in highland forests. The explanation of such disparity lies in the following properties of lowland, as compared to highland, forests: the higher proportion of species with greater ability for local persistence as the climate warms, the reduced opportunity for short-distance escapes, and the greater habitat fragmentation. Although mountains are currently considered to be among the ecosystems most threatened by climate change (owing to mountaintop extinction), the current inertia of plant communities in lowland forests should also be noted, as it could lead to lowland biotic attrition. [ABSTRACT FROM AUTHOR]

Global change affects alpine ecosystems by, among many effects, by altering plant distributions and community composition. However, forecasting alpine vegetation change is challenged by a scarcity of studies observing change in fixed plots spanning decadal-time scales. We present in this article a probabilistic modeling approach that forecasts vegetation change on Niwot Ridge, CO using plant abundance data collected from marked plots established in 1971 and resampled in 1991 and 2001. Assuming future change can be inferred from past change, we extrapolate change for 100 years from 1971 and correlate trends for each plant community with time series environmental data (1971-2001). Models predict a decreased extent of Snowbed vegetation and an increased extent of Shrub Tundra by 2071. Mean annual maximum temperature and nitrogen deposition were the primary a posteriori correlates of plant community change. This modeling effort is useful for generating hypotheses of future vegetation change that can be tested with future sampling efforts. [ABSTRACT FROM AUTHOR]

We updated the floristic checklist of the Nizanda region, Isthmus of Tehuantepec (southern Mexico), characterized the occurring plant communities based on dominant species, and described the region’s flora according to life form, growth form, growth type, and growth habit spectra. Ten years of botanical exploration, along with surveys in 188 100-m2 samples from different vegetation types, provided the baseline floristic information. Ordination and classification analyses were performed to examine the degree of differentiation between communities. Geographical ranges of all species were used to assess biogeographical relationships of this flora. The inventory includes 920 species (553 genera, 124 families). More than one-third of the families were represented by a single species, whereas the 10 richest families had 43% of the species richness. Dendrograms showing plot classification at three taxonomic levels (species, genus and family) revealed savannah as the most strongly differentiated community amid seven vegetation types. Regarding growth forms, forbs and trees prevailed. Phanerophytes were the most common life form category, whereas herbs and woody plants were the dominant growth types. The largest richness for all taxonomic levels was recorded in the tropical dry forest. The expanded floristic knowledge gained for the Nizanda region provided better criteria to revise the classification scheme of its vegetation. Our preliminary biogeographical analysis illustrates the role of the Isthmus of Tehuantepec as a corridor for thermophilous floras between two oceanic watersheds, and as a natural distributional limit for several Mesoamerican plant species. [ABSTRACT FROM AUTHOR]

This study focuses on a phytosociological system of the extensive Larix gmelinii and Larix cajanderi dominated forests and woodlands that span the nemoral, boreal and subarctic zones in northeast Asia in the Russian Far East, Eastern Siberia and northern China, an area that covers more than 5 million km2. A total of 299 relevés representing different parts of the larch forest range were used to classify communities in this area into the boreal Rhytidio rugosi-Laricetea sibiricae and Vaccinio-Piceetea and to the nemoral Querco mongolicae-Betuletea davuricae. The hierarchical system of lower syntaxa of larch forests and woodlands of northeast Asia includes 24 associations and nine subassociations. Nineteen associations and two alliances – Rhododendro aurei-Laricion cajanderi and Rhododendro daurici-Laricion gmelinii – are described for the first time. Two associations were classified into Dictamno dasycarpi-Quercion mongolicae of Lespedezo bicoloris-Quercetalia mongolicae representing the nemoral class Querco mongolicae-Betuletea davuricae. All larch communities in the nemoral zone represent different post-fire-event stages. Eleven associations occurring in humid conditions of the boreal zone and in the areas influenced by the Pacific Ocean are classified into Abieti nephrolepidis-Piceion jezoensis, Piceion jezoensis and Pino pumilae-Piceion jezoensis representing boreal forests of humid maritime regions belonging to the order Abieti veitchii-Piceetalia jezoensis. In this area seral larch communities occupy zonal sites, and primeval larch forests may occur only in edaphic conditions restricting the distribution of zonal dominants, Picea jezoensis and the species of Abies. The area of continuous permafrost within the boreal zone having continental and ultracontinental climate conditions is occupied by primeval larch forests united in Ledo palustris-Laricion cajanderi and Rhododendro aurei-Laricion cajanderi of Ledo palustris-Laricetalia cajanderi, and on sites with dry soils with a deeper frozen horizon in Lathyro humilis-Laricion cajanderi of Lathyro humilis-Laricetalia cajanderi. [ABSTRACT FROM AUTHOR]

Through tabular and average linkage cluster analyses, 737 phytosociological relevés were classified. Based on these relevés, we described and typified the associations, alliances, orders, and classes grouping the coastal plant communities of the Baja California peninsula. Diagnostic tables, classification by average linkage clustering, and climatic, edaphic, and biogeographical data were used to establish floristic affinities among these syntaxa and to interpret their distributions. Syntaxa were characterized by their floristic composition, physiognomy, and biogeographical distribution, along with their positions in halophilous and psammophilous gradients. Thirty-three associations were identified, of which 22 are here described for the first time. Our syntaxonomical proposal includes descriptions of nine new alliances, seven new orders and four new classes: Allenrolfeetea occidentalis, Atriplici julaceae–Frankenietea palmeri, Euphorbio leucophyllae–Sporoboletea virginici and Achyronichio cooperi–Abronietea villosae. [ABSTRACT FROM AUTHOR]

The amount of large woody debris (LWD) in Pacific Northwest estuaries has declined dramatically since Euro-American settlement in the mid 19th century. Little is known about the ecological significance of estuarine LWD. This ignorance impairs protection and restoration of habitat critical to threatened Chinook salmon (Oncorhynchus tshawytscha), as well as other fish and wildlife. This study investigates whether LWD affects the distribution of estuarine shrubs, particularly nitrogen-fixing Myrica gale L. (sweetgale), which dominates the tidal shrub community of the Skagit River estuary, Washington, U.S.A. LWD, M. gale, and other shrubs were surveyed along line transects in an oligohaline tidal marsh and in abandoned agricultural land whose dikes failed more than 50 years ago and which has reverted to marsh. The results demonstrate a strong association between LWD and M. gale. M. gale was very rare on LWD < 30 cm in diameter, increasingly more common for LWD between 30 and 75 cm, and always present on LWD ⩾ 75 cm. The marsh surface was generally 45 cm below mean higher high water (MHHW), suggesting LWD benefits M. gale by providing a growth platform at an elevation near MHHW and reducing flooding stress. The largest and most abundant tree in the marsh, Picea sitchensis, averaged only 35.8 cm in diameter, which suggests LWD recruitment from upstream sources is necessary to sustain M. gale populations in the geomorphologically dynamic Skagit marsh. By affecting the distribution and abundance of M. gale in the estuary, LWD may indirectly affect nitrogen dynamics in the marsh and secondary production of detritivores and herbivores. [ABSTRACT FROM AUTHOR]

Iberian gypsophile plant communities are considered a priority for conservation by the European Community because of their highly specialized flora in gypsum outcrops in arid and semiarid regions. Despite the ecological importance of these ecosystems, the edaphic factors that constrain plant communities on gypsiferous soils remain unclear. It has been proposed that both the chemical and physical restrictive conditions of gypsum soils determine gypsophily in plants. Here we hypothesize that the rigors of the gypsum soil environment depends on topography, decreasing from flat areas on hilltops to south-oriented slopes and finally to slopes oriented to the north. We also hypothesized that the relaxation of the rigors of the gypsum soil environment with topography affects both to individual plant and community characteristics of gypsophile vegetation: we expect a reduction of gypsophyte abundance, an increase of diversity and the amelioration of facilitative interactions of plant species. We analysed the physical and chemical properties of gypsum soils that have been proposed that determine the rigors of the gypsum soil environment (i.e.: unbalanced ion concentrations and superficial soil crust). The predicted rigor gradient along topographical locations was confirmed and was mainly caused by superficial soil crust. The decreasing rigor gradient was accompanied by a fall in the abundance of gypsophytes. However, when gypsophytes were considered separately, several patterns were observed, indicating distinct tolerance to relaxation of rigor of the gypsum soil conditions and different competition abilities between gypsophytes. Plant species were more clumped, and gypsophile communities presented higher diversity, evenness and richness values where rigor of gypsum soil conditions were maximum (flat hilltop positions). Relaxation of rigor (north-oriented slopes) was characterized by loss of facilitative interaction between species and the dominance of the gypsovag Rosmarinus officinalis L., although richness was still very high, which can be attributed to the coexistence of gypsophytes and gypsovags. We conclude that the rigor of gypsum soil environment gradient with topography is mainly determined by superficial soil crust, and it is a crucial determinant of gypsophile plant communities. [ABSTRACT FROM AUTHOR]

The aquatic plant communities in two Irish canals were examined between 1990 and 1994 to investigate the factors that influence plant species distribution and community structure. Four main aquatic plant groups were identified by TWINSPAN. Two groups were characterised by bankside vegetation, including Carex sp., Juncus bulbosus and Scirpus lacustris. Large mixed assemblages of emergent, floating leaved, free floating and submerged plant species characterised the third group. The fourth group was species poor and was dominated by Cladophora sp. Canonical Correspondence Analysis identified weed control history, total oxidised nitrogen, water colour, distance from feeder stream and distance from summit as the factors that potentially influenced the distribution of plant species. The results indicated that ongoing management practices did not significantly alter the overall structure and abundance of the plant communities during the study period. [ABSTRACT FROM AUTHOR]

Three species of Elodea ( Elodea canadensis Michaux, E. nuttallii St John and E. ernstiae St John) have colonized Europe from the American continent. All three arrived in the Alsatian Rhine floodplain (north-eastern France) soon after their arrival in Europe, i.e. in the mid-19th century for E. canadensis, and in the mid-20th century for E. nuttallii and E. ernstiae. The paper investigates the present distribution of Elodea spp. in the floodplain by quantifying the species’ respective occurrences and by describing their habitats. The study further focuses on E. nuttallii which is presently colonizing other parts of Europe. It analyses whether it has continued to expand in the Alsatian Rhine floodplain during recent decades, and it checks whether changes in the abundance of E. nuttallii have had an impact on species richness of water plant communities. E.␣nuttallii has been found to be at present one of the most dominant and most frequent aquatic plant species in the study sector, while E. canadensis and E. ernstiae are less abundant. The species’ distributions differ with regard to water chemistry and water temperature: E. canadensis occurs in oligo-mesotrophic, rather stenothermic habitats, whereas E. nuttallii and E. ernstiae can be encountered in meso- to eutrophic sites with little or no arrival of stenothermic ground water. By comparing successive vegetation relevés from the same sites the study revealed further that the distribution of E. nuttallii has been stable in recent decades, despite local fluctuations in abundance. No relationship could be established between those fluctuations and changes in species richness or type of local plant communities. The sum of the results suggests that the expansion of E. nuttallii in the Alsatian Rhine floodplain had been completed prior to the study period. The species’ present distribution in the study sector as well as its position in local plant communities might therefore be considered a model for what can be expected to happen in areas where E.␣ nuttallii has only recently arrived. [ABSTRACT FROM AUTHOR]

The aim of the study was to establish and verify a predictive vegetation model for plant community distribution in the alti-Mediterranean zone of the Lefka Ori massif, western Crete. Based on previous work three variables were identified as significant determinants of plant community distribution, namely altitude, slope angle and geomorphic landform. The response of four community types against these variables was tested using classification trees analysis in order to model community type occurrence. V-fold cross-validation plots were used to determine the length of the best fitting tree. The final 9node tree selected, classified correctly 92.5% of the samples. The results were used to provide decision rules for the construction of a spatial model for each community type. The model was implemented within a Geographical Information System (GIS) to predict the distribution of each community type in the study site. The evaluation of the model in the field using an error matrix gave an overall accuracy of 71%. The user’s accuracy was higher for the Crepis–Cirsium (100%) and Telephium–Herniaria community type (66.7%) and relatively lower for the Peucedanum–Alyssum and Dianthus–Lomelosia community types (63.2% and 62.5%, respectively). Misclassification and field validation points to the need for improved geomorphological mapping and suggests the presence of transitional communities between existing community types. [ABSTRACT FROM AUTHOR]

To continue our study on the chionophilous communities of western North America, this report presents a phytosociological survey of communities growing in a boreal macroclimate. Combining the Braun-Blanquet approach with numerical analysis, 378 relevés were ordered and classified by tabular and average linkage cluster analyses, revealing 11 associations in the classes Salicetea herbaceae, Loiseleurio–Vaccinietea, and Carici rupestris– Kobresietea bellardii. The following new syntaxa are described and typified: Carici podocarpae– Anemonetalia parviflorae, Solidagini arcticae– Dryadion alaskensis, Taraxaco alaskani– Salicion rotundifoliae, Vaccinio mini– Betuletalia exilis, Polygono plumosi– Cassiopion tetragonae, Arnico lessingii– Cassiopetum tetragonae, and Carici podocarpae– Betuletum exilis. [ABSTRACT FROM AUTHOR]

Through tabular and average linkage cluster analyses, 872 phytosociological relevés, including 491 obtained from the literature and 381 of our own relevés obtained in the field, were ordered and classified. Based on these relevés, we then described and typified the associations, alliances, orders, subclasses, and classes defining the chionophilous communities of the boreal, temperate and Mediterranean climates of western North America. Diagnostic tables, ordination, clustering, and climatic, edaphic, and biogeographical data were used to establish floristic affinities among these syntaxa and interpret their distributions. Syntaxa were characterized by their floristic composition, physiognomy and biogeographical distribution, along with their position on the snow gradient. Finally, we ascribed the communities growing in temperate and Mediterranean climates to the new class Hieracio gracilis-Juncetea drummondii, including 3 subclasses, 6 orders, 12 alliances and 34 associations. [ABSTRACT FROM AUTHOR]

The moss Pogonatum dentatum has expanded its distribution in Fennoscandia from mountainous areas into the lowlands. This recent expansion appears to be associated with changes in important life-history parameters in female shoots. We examined shoot age and size at first production of sex organs and mature spores in P. dentatum to investigate this phenomenon. Female shoots produced mature spores for the first time in the lowlands in their second year but in their third year in the mountains. However, sex organs were produced by second year plants in both areas. There was no size difference between the mountain and lowland female shoots at the time of spore production. Among mountain females reproducing for the first time, 41% of the shoots branched, making them potentially ‘iteroparous’. Branching was not observed among lowland females. Male shoots showed no difference in production of sex organs, and were produced by second year shoots in both areas. Female shoots in the lowlands have earlier spore production and exhibit ‘semelparous’ behaviour by not producing branches. This suggests that the lowland phenotypes of P. dentatum are more ‘invasive’ than the mountain phenotypes. Earlier studies showing high rates of diaspore establishment in lowland areas also support this observation. [ABSTRACT FROM AUTHOR]

We investigated the spatial patterns of perennial species ( Stipa tenacissima, Anthyllis cytisoides Globularia alypum, Brachypodium retusum and chamaephytes) in a 50 m × 50 m semi-arid steppe by using the combination of a linear model of coregionalization (LMC) and sampling units of varying size (1.25 m × 1.25 m, 2.5 m × 2.5 m, and 5 m × 5 m). The data-adjusted LMC showed the patchy structure of the vegetation, which was especially evident with the highest resolution grid. It also detected a periodic pattern in the distribution of S. tenacissima, as well as autocorrelation at two spatial scales for A. cytisoides and G. alypum. The latter species was negatively associated with the other species at both short and long distances. These negative associations were consistent for all sampling grids and suggest the presence of interference between G. alypum and the rest of the evaluated species. Despite species-specific differences, the LMC was fitted satisfactorily to all of them. This suggests a common variation pattern for all the species, which may be caused by an underlying environmental property driving the patterns of all the species or, alternatively, by the dominance of some species’ spatial pattern, or another kind of species association, over the rest. The spatial patterns found were profoundly affected by the observational scale. Our results reveal that the multivariate geostatistical approach introduced in this paper is a suitable technique for the spatial analysis of semi-arid plant communities. It allows plant ecologists to evaluate if the species forming the plant community of interest share a common spatial pattern, and to assess the spatial covariation between the species forming a plant community at different spatial scales independently. [ABSTRACT FROM AUTHOR]

Sierra Nevada forests have high understory species richness yet we do not know which site factors influence herb and shrub distribution or abundance. We examined the understory of an old-growth mixed-conifer Sierran forest and its distribution in relation to microsite conditions. The forest has high species richness (98 species sampled), most of which are herbs with sparse cover and relatively equal abundance. Shrub cover is highly concentrated in discrete patches. Using overstory tree cover and microsite environmental conditions, four habitats were identified; tree cluster, partial canopy, gap, and rock/shallow soil. Herb and shrub species were strongly linked with habitats. Soil moisture, litter depth and diffuse light were the most significant environmental gradients influencing understory plant distribution. Herb cover was most strongly influenced by soil moisture. Shrub cover is associated with more diffuse light, less direct light, and sites with lower soil moisture. Herb richness is most affected by conditions which influence soil moisture. Richness is positively correlated with litter depth, and negatively correlated with direct light and shrub cover. Disturbance or management practices which change forest floor conditions, shallow soil moisture and direct light are likely to have the strongest effect on Sierran understory abundance and richness. [ABSTRACT FROM AUTHOR]

Forest communities dominated by Picea jezoensis (Yezo spruce) are described from across their entire distributional range in eastern Asia, including the territories of the Russian Far East and Japan. A total of 476 relevés are used representing the following dominant types of spruce forests: pure P. jezoensis, mixed P. jezoensis and Abies sachalinensis, mixed P. jezoensis and Abies nephrolepis, and pure Picea glehnii communities. The vegetation is classified into 11 associations, 2 community types, 6 subassociations, 25 variants and 8 subvariants. Nine associations, including the Asaro heterotropoidis-Abietetum sachalinensis, Weigelo middendorffianae-Piceetum jezoensis, Lysichito-Piceetum glehnii, Swido albae-Piceetum obovatae, Oplopanaco elati-Piceetum jezoensis, Philadelpho tenuifolii-Piceetum jezoensis, Vaccinio-Piceetum jezoensis, Rhododendro aurei-Piceetum jezoensis, and Moneseto uniflorae-Piceetum jezoensis, are described for the first time. The ecology and structure of all communities are described and their syntaxonomy discussed. The communities are placed in three alliances, Piceion jezoensis, Abieti nephrolepidis-Piceion jezoensis and Pino pumilae-Piceion jezoensis, all. nov. All of the communities described are considered to belong to the order Abieti-Piceetalia of the class Vaccinio-Piceetea. [ABSTRACT FROM AUTHOR]

As an introduction to the special issue "Vegetation of Circumboreal Coniferous Forests", a brief history is provided of the development and present state of floristic vegetation surveys of the boreal and mountain coniferous forests of Europe, northern Asia and North America. The focus is on forests assigned to the phytosociological class Vaccinio-Piceetea and closely related vegetation types. [ABSTRACT FROM AUTHOR]

The natural geographical occurrence, carbon assimilation, and structural and biochemical diversity of species with C4 photosynthesis in the vegetation of Mongolia was studied. The Mongolian flora was screened for C4 plants by using 13C/12C isotope fractionation, determining the early products of 14CO2 fixation, microscopy of leaf mesophyll cell anatomy, and from reported literature data. Eighty C4 species were found among eight families: Amaranthaceae, Chenopodiaceae, Euphorbiaceae, Molluginaceae, Poaceae, Polygonaceae, Portulacaceae and Zygophyllaceae. Most of the C4 species were in three families: Chenopodiceae (41 species), Poaceae (25 species) and Polygonaceae, genus Calligonum (6 species). Some new C4 species in Chenopodiaceae, Poaceae and Polygonaceae were detected. C4 Chenopodiaceae species make up 45% of the total chenopods and are very important ecologically in saline areas and in cold arid deserts. C4 grasses make up about 10% of the total Poaceae species and these species naturally concentrate in steppe zones. Naturalized grasses with Kranz anatomy,of genera such as Setaria, Echinochloa, Eragrostis, Panicum and Chloris, were found in almost all the botanical-geographical regions of Mongolia, where they commonly occur in annually disturbed areas and desert oases. We analyzed the relationships between the occurrence of C4 plants in 16 natural botanical-geographical regions of Mongolia and their major climatic influences. The proportion of C4 species increases with decreasing geographical latitude and along the north-to-south temperature gradient; however grasses and chenopods differ in their responses to climate. The abundance of Chenopodiaceae species was closely correlated with aridity, but the distribution of the C4 grasses was more dependent on temperature. Also, we found a unique distribution of different C4 Chenopodiaceae structural and biochemical subtypes along the aridity gradient. NADP-malic enzyme (NADP-ME) tree-like species with a salsoloid type of Kranz anatomy, such as Haloxylon ammodendron and Iljinia regelii, plus shrubby Salsola and Anabasis species, were the plants most resistant to ecological stress and conditions in highly arid Gobian deserts with less than 100 mm of annual precipitation. Most of the annual C4 chenopod species were halophytes, succulent, and occurred in saline and arid environments in steppe and desert regions. The relative abundance of C3 succulent chenopod species also increased along the aridity gradient. Native C4 grasses were mainly annual and perennial species from the Cynodonteae tribe with NAD-ME and PEP-carboxykinase (PEP-CK) photosynthetic types. They occurred across much of Mongolia, but were most common in steppe zones where they are often dominant in grazing ecosystems. [ABSTRACT FROM AUTHOR]