Diversity of wetland vegetation in the Bulgarian high mountains, main gradients and context-dependence of the pH role

We fill a gap in understanding wetland vegetation diversity and relationship with environmental determinants in Bulgarian high mountains. A total of 615 phytosociological samples were taken from springs, mires, wet meadows and tall-forb habitats throughout Bulgaria, of which 234 relevés are from mire and spring vegetation above timberline. The vegetation was classified by TWINSPAN and the resulting vegetation types were reproduced by the formal definitions using the combination of Cocktail species groups based on phi-coefficient of joint co-occurrence of the species. Nine vegetation types of springs and fens have been clearly delimited above the timberline. All vegetation types include Balkan endemic species, the representation of which varies. Fens generally harbour more Balkan endemics than do springs, with the exception of species-poor high-altitude Drepanocladetum exannulati. The gradient structure of the vegetation was revealed by DCA and by CCA with forward selection of environmental factors. The major determinants of vegetation variation strongly differ above and below the timberline and likewise between springs and fens. The base-richness gradient controls the floristic variation of Bulgarian submontane fens, whereas the complete data set including both submontane and subalpine fens is governed by the altitude gradient from lowland and basin fens to subalpine fens rich in Balkan endemics. When focusing on sites above the timberline only, the first DCA axis separates fens from springs without organic matter. The major species turnover in springs follows the variation in water pH and mineral content in water, whereas fen vegetation variation is primarily controlled by succession gradient of peat accumulation. Altitude remains an important factor in all cases. Weak correlation between water pH and conductivity was found. This correlation was even statistically insignificant in fens above the timberline. Water pH is not influenced by mineral richness in Bulgarian high mountains, since it is buffered by decomposition of organic matter in fens. In springs, pH reaches maximum values due to strong aeration caused by water flow. The plant species richness decreases significantly with increasing altitude. The increase of species richness towards circumneutral pH, often found in mires, was not confirmed in Bulgarian high mountains. The correlation between species richness and pH was significant only when arctic-alpine species and allied European high-mountain species were considered separately. The richness of boreal species was independent on pH. Some of them had their optima shifted to more acidic fens as compared to regions below the timberline. Our results suggest that subalpine spring and fen vegetation should be analysed separately with respect to vegetation-environment correlations. Separate analysis of fens below and above timberline is quite appropriate.     

Vegetation diversity of salt‐rich grasslands in Southeast Europe

Question

How does the plant species composition of Pontic–Pannonian salt‐rich habitats vary on a large geographical scale? Do the floristic differences between Pannonia and the Balkans correspond to the current phytosociological classification?

Location

Pannonia (Hungary, Slovakia, Austria, Czech Republic, Croatia, Serbia, Romania) and the Balkans (Bulgaria, Macedonia, Greece).

Methods

Two thousand four hundred and thirty‐seven relevés from halophytic and sub‐halophytic habitats were classified using a modified TWINSPAN. The crispness of classification was checked. DCA and CCA with climate data as explanatory variables were applied.

Results

The classification was best interpreted at the level of 15 clusters. The vegetation changed along the salinity gradient from sub‐halophytic grasslands (including Trifolion resupinati alliance of the Molinio‐Arrhenatheretalia class and Beckmannion eruciformis and Festucion pseudovinae p. p. alliances of the Festuco‐Puccinellietea class) and reed beds (Bolboschoenion maritimi p. p. alliance; the Phragmito‐Magnocaricetea class), through steppe and wet inland halophytic vegetation (Festucion pseudovinae p. p., Puccinellion limosae, Pucinellion convolutae, Bolboschoenion maritimi p. p. and Juncion gerardii of the Festuco‐Puccinellietea class) towards the extreme halophytic vegetation of the Thero‐Salicornietea, Crypsietea and Juncetea maritimi classes. This gradient was longer in the Balkan region, where it spanned from the sub‐mediterranean salt‐rich grasslands to the extremely halophytic vegetation at the Black Sea coast. The second most important gradient coincided with the water regime. Some vegetation types appeared to be confined to either the Pannonian or the Balkan region (especially within dry sub‐halophytic and steppe halophytic grasslands), while others were distributed across the entire study area. The above‐mentioned pattern did not always correspond with current classification systems.

Conclusions

Variation in salt‐rich vegetation predominantly follows the salinity and water regime gradients. Geographical variation, generally coinciding with climatic and historical effects, is also important, especially in drier salt‐rich habitats. Our large‐scale analysis of the floristic variation of salt‐rich habitats might be useful for the unification of classification systems that differ substantially between the countries involved. In addition, the analysis may be useful for adjustment of a classification system in the poorly explored Balkan region, where particular vegetation types were identified with, or delimited from, Central European vegetation types without detailed comparative analysis until now.

     

Local and regional patterns of species richness in Central European vegetation types along the pH/calcium gradient

We investigated the relationship between soil pH/calcium content and species richness of vascular plants in seven broadly defined Central European vegetation types, using Ellenberg indicator values for soil reaction and a phytosociological data set of 11,041 vegetation sample plots from the Czech Republic. The vegetation types included (A) broad-leaved deciduous forests, (B) meadows, (C) dry grasslands, (D) reed-bed and tall-sedge vegetation, (E) fens and transitional mires, (F) perennial synanthropic vegetation and (G) annual synanthropic vegetation. Relationships between local species richness (alpha diversity) and pH/calcium were positive for vegetation types A and C, negative for D and G, unimodal for E, and insignificant for B and F. Ellenberg soil reaction values explained 37% of variation in local species richness for vegetation type E, 24% for A, 13% for D, but only less than 4% for the others. Species pool size, i.e., the number of species that can potentially occur in a given habitat, was calculated for each plot using Beals index of sociological favourability applied to a large phytosociological database. For most vegetation types, the relationships between species pool size and pH/calcium were similar to the relationships between local species richness and pH/calcium, with the exception of meadows (weak unimodal) and perennial synanthropic vegetation (weak negative).These patterns suggest that for those types of Central European vegetation that developed independently of human influence in the Pleistocene or early Holocene (dry grasslands, deciduous forests), there are larger pools of calcicole than calcifuge species. This pattern is also found at the level of local species richness, where it is, however, less clearly pronounced, possibly due to the predominance of a few widespread and generalist calcifuges in acidic habitats. The unimodal pattern found in mires may result from similar underlying mechanisms, but in high pH environments mineral-rich spring waters probably decrease species richness by having toxic effects on plant growth. By contrast, vegetation types developed under direct human influence (meadows, synathropic vegetation) show weak negative or no relationships of local species richness or species pool to pH/calcium gradient. These results support the hypothesis ofPärtel (Ecology 83: 2361–2366, 2002) andEwald (Folia Geobot. 38: 357–366, 2003), that the modern calcicole/calcifuge disparity in the species pool of Central European flora has resulted from historical and evolutionary processes that took place on high pH soils. In the Pleistocene, calcareous soils dominated both the dry continental landscapes of Central Europe and glacial refugia of temperate flora, which were mostly situated in southern European mountain ranges with abundant limestone and dolomite. The negative pattern of species richness along the pH/calcium gradient found in reed-bed and tall-sedge vegetation, however, is not consistent with this historical explanation.     

Contribution to the knowledge of Bulgarian serpentine grasslands and their relationships with Balkan serpentine syntaxa

Serpentine areas, including those in Bulgaria, are rich in endemic taxa, and still remain to be investigated phytocoenologically. We analyse the vegetation types in various sites and compare them with those in other Balkan countries. The main objectives were (1) to explore and describe the relationships between the vegetation in the serpentine areas investigated in Bulgaria with those in the Balkan Peninsula and (2) to explore and classify the diversity of vegetation in grasslands on serpentine rocks in eastern Rhodope, Bulgaria. The classic methodology of the Braun-Blanquet school was applied to the exploration of the vegetation. Average linkage method (unweighted pair group method with arithmetic mean) and principal coordinate analysis were used to evaluate floristic and synoptic similarities. As a result, the new endemic association Onosmo pavlovae-Festucetum dalmaticae was proposed. This association can be included in the alliance Alyssion heldreichii Bergmeier et al. 2009, newly described on serpentine rocks in northern Greece. Our data confirmed the existence of similar or vicariant endemic syntaxa (associations) on isolated serpentine terrains in northern Greece and south-eastern Bulgaria.     

Mire vegetation of the Muránska Planina Mts — formalised classification,ecology, main environmental gradient and influence of geographical position

Mire vegetation of the Muránska planina Mts and adjacent parts of neighbouring orographical units was studied in 1998–2005 using the standard Zürich-Montpellier (Braun-Blanquet) approach. We applied the defined phytosociological species groups and national formal definitions of mire associations in data processing. Within the classes Scheuchzerio-Caricetea fuscae and Oxycocco-Sphagnetea, seven associations (Caricetum davallianae, Carici flavae-Cratoneuretum filicini, Valeriano simplicifoliae-Caricetum flavae, Caricetum goodenowii, Carici echinatae-Sphagnetum, Carici rostratae-Sphagnetum and Pino mugo-Sphagnetum) were classified using formal classification criteria. Two other communities (Sphagno warnstorfii-Caricetum davallianae and Eriophoro vaginati-Sphagnetum recurvi) were not classified due to the lack of sufficient number of diagnostic species from species groups. The first DCA axis followed the mineral richness gradient. Vegetation plots were arranged from rich fens over moderately rich fens towards poor Sphagnum fens and raised bog. This fact was confirmed by a strong and significant correlation of the DCA site scores on the first axis with the measured pH and water conductivity as a surrogate of mineral richness. The second DCA axis correlated with mean Ellenberg’s indicator values for both temperature and soil nutrients. This pattern corresponds to that found in other regions of diversified Central-European landscape. We can therefore conclude that marginal geographical position and climatic specifity of the region under study did not alter gradient structure of the mire vegetation. When diversity of mire vegetation was compared to other regions in Slovakia by applying the same formal definitions to different regions, the study region was found to be conspicuously less diverse than the distribution centres of mire habitats in Slovakia (Orava and Vysoké Tatry regions), but more diverse than most of other marginal regions of mire distribution. Relatively high beta diversity of mires was probably caused by variable bedrock and local climate.     

The Historic Square Foot Dataset – Outstanding small-scale richness in Swiss grasslands around the year 1900

Grasslands host a significant share of Europe's species diversity but are among the most threatened vegetation types of the continent. Resurvey studies can help to understand patterns and drivers of changes in grassland diversity and species composition. However, most resurveys are based on local or regional data, and hardly reach back more than eight decades. Here, we publish and describe the Historic Square Foot Dataset, comprising 580 0.09-m² and 43 1-m² vegetation plots carefully sampled between 1884 and 1931, covering a wide range of grassland types across Switzerland. We provide the plots as an open-access data set with coordinates, relocation accuracy and fractional aboveground biomass per vascular plant species. We assigned EUNIS habitat types to most plots. Mean vascular plant species richness in 0.09 m² was 19.7, with a maximum of 47. This is considerably more than the present-day world record of 43 species for this plot size. Historically, species richness did not vary with elevation, differing from the unimodal relationship found today. The data set provides unique insight into how grasslands in Central Europe looked more than 100 years ago, thus offering manifold options for studies on the development of grassland biodiversity and productivity.     

Syntaxonomy and phytogeographical differentiation of the Fagus woods in the Southwest Balkan Peninsula

Abstract. Up to now the syntaxonomy of the Fagus woods of the southern Balkans is far less known than that of beech communities in the northwestern part of the Balkan Peninsula and in central and western Europe. A set of 607 phytosociological relevés from southeastern Serbia, the Former Yugoslav Republic of Macedonia, and northern and central Greece was subjected to numerical classification and ordination. These results were used for a syntaxonomic revision of Fagus, Fagus‐Abies and Fagus‐Acer woodland communities of the southwestern Balkans. The Doronico columnae‐Fagenion (seven associations from Serbia, the F.Y.R.O.M., and high altitudes in northern Greece) and the Doronico orientalis‐Fagenion (four associations from northern and central Greece) were distinguished. The results of ordination by Canonical Variates Analysis (CVA) showed a very distinct phytogeographical pattern of differentiation between community types. The floristic composition of Fagus woods changes markedly along the north‐south gradient. The share of Subbalkan, Balkan, Submediterranean and Mediterranean species increases significantly towards the south, while the Central‐European, European, Euro‐Siberian, Euro‐Asiatic and Circumpolar species decrease in the same direction. The syntaxonomic differentiation of the Fagus woodlands and their classification into regional suballiances reflects this gradient. With the rise in altitude, the number of Balkan, Mediterranean, Submediterranean, European and Euro‐Asiatic species declines.     

Species Richness, Community Specialization and Soil-Vegetation Relationships of Managed Grasslands in a Geologically Heterogeneous Landscape

The increasing importance of the conservation value of managed grasslands has led to many studies exploring edaphic determinants of grassland biodiversity. Most studies, however, come either from very large areas, where biogeographical factors such as dispersal limitation may play a role, or from small, but ecologically rather uniform, regions. In addition, few studies further distinguish between plant specialists and generalists in the interpretation of the observed patterns. Here we studied species richness in semi-natural, managed grasslands in the Strá?ovské vrchy Mountains in the West Carpathians, Slovakia, where there is a matrix of different bedrocks (crystalline, sandstone, claystone, limestone) on a steep altitudinal gradient. In 89 vegetation plots we sampled the species composition of vascular plants and bryophytes and measured soil chemistry, slope angle, heat index, altitude and soil depth. We further applied Ellenberg indicator values and classified species into community specialists or generalists based on the analysis of a large phytosociological database. Using cluster analysis, we delimited five vegetation types that clearly differed in response to soil characteristics. Species richness varied between 19 and 64 species per 16?m². The main compositional gradient correlated with measured soil pH and calcium, but species richness was not significantly correlated with these factors. Soil available phosphorus was not associated with species composition as has been found elsewhere, but it did correlate negatively with species richness and the richness of specialists. Overall, species richness was largely driven by the number of specialists in the plot and particular vegetation types differed conspicuously in their number. We further found significant effects of iron, potassium and sodium on species richness, species composition and the representation of specialists and generalists. Our results provide new insights into the determinants of diversity in managed grasslands as well as to the theoretical species pool concept, explaining species richness variation along a pH gradient.     

Ground vegetation in the Mongolian taiga forest‐steppe ecotone does not offer evidence for the human origin of grasslands

Question: Is the vegetation of meadow and mountain steppes distinct from the ground vegetation of light taiga forests in the transitional zone between these biomes? Location: Western Khentey Mountains, northern Mongolia. Methods: Vegetation was recorded from 100‐m² plots from all dominant types of light taiga forest and dry grassland. Distinctness of ground vegetation was studied with Detrended Correspondence Analysis (DCA). Results: Ground vegetation in the light taiga was significantly different from the herbal vegetation of meadow and mountain steppes. Clear separation was only absent for the Car ex amgunensis meadow steppes that occur in a narrow strip along the forest edge and are partly shaded by trees. Forest and steppe communities followed a moisture gradient according to the DCA ordination with light taiga forests at the moistest sites and steppe communities at the driest sites. Ulmus pumila open woodlands diverged from this pattern, because of their close spatial and phytosociological relationship to mountain steppes. Conclusions: The present results do not support the assumption that grasslands in Mongolia's transitional zone between forest and steppe would generally resemble the ground vegetation of light taiga forests. This contradicts a published hypothesis stating that the vegetation of meadow and mountain steppes would not clearly differ from ground vegetation of light taiga forests in the forest‐steppe transitional zone of Mongolia.     

Use of vegetation classification and plant indicators to assess grazing abandonment in Estonian coastal wetlands

Question: What are the effects of grazing abandonment on the vegetation composition of Estonian coastal wetlands? Location: Vormsi Island and Silma Nature Reserve in western Estonia, Europe. Methods: Local knowledge and field reconnaissance were used to identify current and historical management levels of wetland sites within the west Estonian study area. Nine study sites, with varying management histories, were selected comprising an area of 287 ha. A total of 198 quadrats were taken from 43 distinct vegetation patches in five of the sites. TWINSPAN analysis was used to identify community type, and a phytosociological key was constructed for character taxa. This vegetation classification was then applied within a GIS‐based context to classify all the study sites, using a ground survey technique and 1:2000 scale air photos. Results: We identified 11 different brackish coastal wetland community types. Indicator species were defined with community characteristics for the seven main vegetation types readily recognisable in the field. Coastal wet grasslands were most extensive in grazed sites, or sites that had been more intensively grazed, while abandoned sites were largely composed of Phragmites australis stands, tall grassland, and scrub. Site variations based on vegetation composition were significantly correlated with past grazing intensity. Plant community types showed significant edaphic differences, with particularly low soil moisture and high conductivity and pH for open pioneer patches compared to other vegetation types. Conclusion: Abandonment of traditionally grazed coastal grasslands threatens their characteristic biodiversity. This study found that grazing abandonment reduced the extent of coastal wetland grasslands of particular conservation value. Nevertheless, plant species of conservation interest were found across the sequence of community types described. The study shows that grazing is an important factor influencing coastal wetland plant communities but suggests that vegetation distribution is affected by environmental variables, such as topography.     

Anthracological analysis from Kovacevo, southwest Bulgaria: woodland vegetation and its use during the earliest stages of the European Neolithic

Wood charcoal analysis from Kovacevo in southwest Bulgaria, one of the earliest Neolithic sites in southeastern Europe, provided information about the first stages of anthropogenic impact on vegetation during the Early Neolithic (6159–5630 cal b.c.). Deciduous oak was the most abundant and frequently used taxon in the wood charcoal assemblages. Cornus charcoal was also abundant, probably connected with the use of its twigs as building material in wattle and daub structures. The dominant deciduous oak forest was opened during the Kovacevo I period, as shown by evidence from the Kovacevo Ia and Kovacevo Ib occupation phases. Other types of vegetation, like Black pine (Pinus nigra) woodland, riverine forests and some sub-Mediterranean elements, were used only sporadically, indicating high and sustained availability of wood resources in the oak forests. Anthropogenic impacts were gradual, a pattern that matches contemporary studies elsewhere in the region.     

Syntaxonomy and biogeography of dry grasslands on calcareous substrates in the central and southern Balkans

Questions

Which major syntaxa of dry grasslands supported by carbonate bedrock occur in the central and southern Balkans? What is their position along major ecological gradients and in the context of phytogeographic patterns of the region?

Location

Central and southern Balkans, including western Bulgaria, northern Greece, Kosovo, Macedonia (FYROM) and Serbia.

Methods

We compiled a matrix of 660 relevés of dry grasslands over lime‐rich bedrock, previously classified in the Festuco‐Brometea. We applied clustering techniques to classify separately synoptic and relevé data, and applied NMDS with passive projection of indicator values, climatic data and biogeographic geo‐elements onto ordination diagrams to assist interpretation of the syntaxonomic patterns. We constructed elevation distribution profiles for alliances and classes of grasslands of several grassland classes from a broader study area to elucidate the relationship of the elevational sorting of the syntaxa in relation to latitude.

Results

The analysis revealed six major vegetation types, classified into four orders: (1) Stipo pulcherrimae‐Festucetalia pallentis, incl. (sub)montane rocky steppic grasslands of the Saturejion montanae of central Balkans, and the Koelerio‐Festucion dalmaticae – submontane rocky grasslands of southern Serbia and Kosovo; (2) Astragalo onobrychidis‐Potentilletalia represented by the Saturejo‐Thymion (low‐elevation steppic grasslands of southern Balkans); (3) Festucetalia valesiacae represented by grasslands on deep soil and low elevation of northern Greece, and finally (4) high‐elevation rocky grasslands of southern Balkans, classified as a new alliance – Diantho haematocalycis‐Festucion hirtovaginatae, that might belong to a new, yet undescribed, syntaxonomic order. Ordination suggests that the major differentiation of the high‐rank syntaxa follows north–south geographic and low–high elevation gradients.

Conclusions

Because of the transitional biogeographic position of the studied region, as well as considerable large elevation span across latitudes, the diversity of vegetation types is high. The indication a putative new dry grassland order, the mid‐high altitudes of the southern Balkans points to a need to re‐assess the Balkan vegetation occupying the community niche between the low‐elevation dry grasslands (Festuco‐Brometea) and those typical of high elevations (Elyno‐Seslerietea and Daphno‐Festucetea), seeking parallels to patterns described from the western Alps, Pyrenees, and Apennines. This syntaxonomic unit is poised to expand the concept of the Festuco hystricis‐Ononidetea striatae to the Balkans.

     

Cumulative nitrogen input drives species loss in terrestrial ecosystems

Aim Elevated inputs of biologically reactive nitrogen (N) are considered to be one of the most substantial threats to biodiversity in terrestrial ecosystems. Several attempts have been made to scrutinize the factors driving species loss following excess N input, but generalizations across sites or vegetation types cannot yet be made. Here we focus on the relative importance of the vegetation type, the local environment (climate, soil pH, wet deposition load) and the experimentally applied (cumulative) N dose on the response of the vegetation to N addition. Location Mainly North America and Europe. Methods We conducted a large‐scale meta‐analysis of in situ N addition experiments in different vegetation types, focusing on the response of biomass and species richness. Results Whereas the biomass of grasslands and salt marshes significantly increased with N fertilization, forest understorey vegetation, heathlands, freshwater wetlands and bogs did not show any significant response. Graminoids significantly increased in biomass following N addition, whereas bryophytes significantly lost biomass; shrubs, forbs and lichens did not significantly respond. The yearly N fertilization dose significantly influenced the biomass response of grassland and salt marshes, while for the other vegetation types none of the collected predictor variables were of significant influence. Species richness significantly decreased with N addition in grasslands and heathlands [Correction added on 23 March 2011, after first online publication: ‘across all vegetation types’ changed to ‘in grasslands and heathlands’]. The relative change in species richness following N addition was significantly driven by the cumulative N dose. Main conclusions The decline in species richness with cumulative N input follows a negative exponential pathway. Species loss occurs faster at low levels of cumulative N input or at the beginning of the addition, followed by an increasingly slower species loss at higher cumulative N inputs. These findings lead us to stress the importance of including the cumulative effect of N additions in calculations of critical load values.     

Edaphic relationships among Cirsio-Molinietum and related wet grassland communities in lowland Wales

Abstract. Soil properties are characterized for a range of the Molinietalia vegetation types in lowland Wales. In this oceanic region there is overlap in the distribution of various forms of wet pasture dominated by Molinia caerulea and Juncus acutiflorus. There is subtle and continuous variation in species composition among four communities investigated; this has been analysed by Detrended Correspondence Analysis and partitioned between subcommunities recognized in Rodwell (1991). Canonical Variates Analysis indicated that the main differences in soil conditions between the vegetation classes are related to gradients in base-status; apparent variation in soil fertility may also be significant and requires further investigation. In general, Molinia-Cirsium dissectum fen-meadow soils have higher pH, higher Ca-levels, greater base saturation and lower acidity than Molinia-Potentilla erecta wet grasslands; those of Juncus-Galium palustre rush-pasture and Molinia-Crepis paludosa mire had relatively high levels of inorganic N. The findings are discussed with reference to ecological and phytosociological relationships, and also in the context of nature conservation.     

Floristic characteristics of the wetland sites on dry southern slopes of the Alborz Mts., N. Iran: The role of altitude in floristic composition

The Alborz Mountains, the second largest range in Iran, is, on its southern slopes, mainly covered by steppe vegetation. These dry slopes also include ‘green islands’ of wetland. Floristic diversity and environmental characteristics of 45 of these little-studied wetland sites have been assessed along an altitudinal gradient using one-way ANOVA, Pearson r and detrended correspondence analysis/canonical correspondence analysis (DCA/CCA) analyses. The wetlands proved to be of conservation importance with 310 plant taxa, including 35 endemics or subendemics. Predictably, and consistent with the phytosociological classification of Klein [2001. La végétation altitudinale de L’Alborz Central (Iran): Entre les régions Irano-Touranienne et Euro-sibérienne. Institut Français de Recherche en Iran, Téhéran], there were parallel changes in vegetation both within wetlands and the surrounding steppes and in DCA/CCA analyses altitude appeared to be the primary determinant of floristic composition. Upper mountain wetlands are particularly species-rich and contain many endemics and other species of a narrow phytogeographical distribution. Soil pH declined with altitude, perhaps in part as a consequence of low salinity (and high pH) in the mountains. Consistent with the work of Raunkiaer [1934. The life forms of plants and statistical plant geography. Clarendon Press, Oxford], hemicryptophytes are mainly restricted to upper mountain areas. Though correlated both directly with altitude and with correlation in DCA/CCA plots, phytogeography, life-form and soil pH fail to adequately explain the ecological processes that maintain the altitudinal gradient in vegetation types and species composition. Further studies on site productivity, soil chemistry and climate-related variables are, therefore, on-going in an attempt to understand more fully the ecosystem processes maintaining the diversity of these important wetland sites.     

Phosphorus Translocation by Red Deer on a Subalpine Grassland in the Central European Alps

We examined the role of red deer (Cervus elaphus L.) in translocating phosphorus (P) from their preferred grazing sites (short-grass vegetation on subalpine grasslands) to their wider home range in a subalpine grassland ecosystem in the Central European Alps. Phosphorus was used because it is the limiting nutrient in these grasslands. When we compared P removal of aboveground biomass due to grazing with P input due to the deposit of feces on a grid of 268 cells (20 m × 20 m) covering the entire grassland, we detected distinct spatial patterns: the proportion of heavily grazed short-grass vegetation increased with increasing soil-P pool, suggesting that red deer preferably grazed on grid cells with a higher soil-P pool. Biomass consumption related to increased proportion of short-grass vegetation, and therefore P removal, increased with increasing soil-P pool. However, within the two vegetation types (short-grass and tall-grass), consumption was independent from soil-P pool. In addition, P input rates from defecation increased with increasing soil-P pool, resulting in a constant mean net P loss of 0.083 kg ha⁻¹ y⁻¹ (0.03%–0.07% of soil-P pool) independent of both soil-P pool and vegetation type. Thus, there was no P translocation between grid cells with different soil-P pools or between short-grass and tall-grass vegetation. Based on these results, it is likely that the net rate of P loss is too small to explain the observed changes in vegetation composition from tall-herb/meadow communities to short-grass and from tall-grass to short-grass on the grassland since 1917. Instead, we suggest that the grazing patterns of red deer directly induced succession from tall-herb/meadow communities to short-grass vegetation. Yet, it is also possible that long-term net soil-P losses indirectly drive plant succession from short-grass to tall-grass vegetation, because nutrient depletion could reduce grazing pressure in short-grass vegetation and enable the characteristic tall-grass species Carex sempervirens Vill. to establish.     

Distribution,species diversity and life-form spectra of plant communities along an altitudinal gradient in the northern slopes of Qilianshan Mountains,Gansu, China

We studied the distribution pattern, species diversity and life-formspectra of plant communities along an altitudinal gradient in the mid-sectionofthe northern slopes of Qilianshan Mountains by means of multivariate analyses.Two data sets (167 species × 75 plots, 10 environmental variables ×75 plots), originated from the fieldworks in 1998–1999, were subjected toTWINSPAN and DCCA, resulting in 8 major plant communities: 1)Asterothamnus centraliasiaticus–Halogetonarachnoideus desert grassland on azonal substrates from 1450 to 1600m and 2) zonal Reaumuria soogorica desertgrassland on gravels from 1470 to 1900 m; 3) Stipaprzewalskii–Stipa purpurea montane grassland from 2200 to 2900m; 4) Polygonum viviparum alpine grasslandfrom 2900 to 3700 m; 5) Caraganastenophylla–Ajaniafruticulosa dry-warm shrubland from 2350 to 2800 m; 6)Sabina przewalskii mid-wet warm forest from 2700 to 3300m; 7) Picea crassifolia cold coniferousforestfrom 2450 to 3200 m; 8) Caragana jubatawet-cold alpine shrubland from 3100 to 3700 m. Species diversityand species richness of both grasslands and forests peaked at the intermediateportion of the elevational gradient. Evenness might be strongly influenced byeither biotic or abiotic factors at a local scale, while seems quiteindependentof an elevational gradient at landscape scales. Beta-diversity decreased from1500 to 3700 m, indicating that species turnover declined withincreased elevation. Both richness of life-form and total species richness in agiven altitudinal belt (gamma-diversity) peaked at intermediate elevations,while relative species richness of different life-form varied differently alongthe altitudinal gradient.     

Species richness,alien species and plant traits in Central Argentine mountain grasslands

Abstract. Pattern of native vegetation, distribution of alien species and variation of environmental parameters were studied in mountain grasslands in a lithologically homogeneous Córdoba mountain range in Central Argentina. CCA showed that altitude was the most important factor determining the compositional variation of the vegetation, with soil nutrient status and stoniness as additional factors. Short‐grass communities, associated with the driest habitats on plateaus, showed higher small‐scale native species richness than wet‐turf communities in valleys and tall‐grass communities on slopes. Species richness was negatively correlated with soil parameters that indicate nutrient status and water availability. Also, there was a negative correlation between soil Ca‐ and Mg‐ content and richness. High native species richness coincided with high alien species richness. When smaller units – community types – were considered, it became evident that within short‐grass vegetation, the three most species‐rich community types contained significant numbers of alien species, while the other two did not. Even within one community type, the same quadrats that contained the highest number of native species, were also characterized by the highest numbers of alien species. Evidently, the same mechanism was responsible for high richness of both native and alien species. Alien species were distinguished by a greater proportion of annuals and prostrate stoloniferous plants, by lower palatability and by smaller proportion of zoochory. DCA ordination of quadrats on the basis of plant traits as attributes resulted in a clear distinction of three main vegetation types. Short‐grass vegetation was distinguished by a predomination of late flowering species, tall‐grass vegetation by the presence of high herbaceous plants and bushes, and wet‐turf vegetation by the presence of plants with storage organs, the lack of hairy leaves, and by a high proportion of cryptophytes. Quadrats with and without alien species were distinguished as well, indicating that the occurrence of aliens may be dependent on plant traits in a particular patch of a community.     

Plant diversity patterns and their relationships with soil and climatic factors along an altitudinal gradient in the middle Tianshan Mountain area, Xinjiang, China

Patterns of plant diversity along the altitudinal gradient of Tianshan in central Xinjiang, China were examined. Plant and environment characteristics were surveyed from higher, south of Bogeda peak, to lower, north of Guerbantonggute desert. There were a total of 341 vascular plant, 295 herbage, 41 shrub, and seven tree species in the sampled plots. The plant richness of vegetation types generally showed a unimodal pattern along altitude, with a bimodal change of plant species number at 100-m intervals of altitudinal samples. The two belts of higher plant richness were in transient areas between vegetation types, the first in areas from dry grass to forest, and the second from forest to sub-alpine grass and bush. The beta diversity varied with altitudinal changes, with herbaceous species accounting for most species, and thus had similar species turnover patterns to total species. Matching the change of richness of plant species to environmental factors along altitude and correlating these by redundancy analysis revealed that the environmental factors controlling species richness and its pattern were the combined effects of temperature, precipitation, soil water, and nutrition. Water was more important at low altitude, and temperature at high altitude, and soil chemical and physical characters at middle altitudes. This study provides insights into plant diversity conservation of Bogeda Natural Reserve Areas in Tianshan Mountain. Nomenclatures: the scientific name for plants follows Flora of China (Compiling Committee of Flora of China).