FLORISTIC AND COMMUNITY DIVERSITY OF SUB-ALPINE AND ALPINE GRASSLANDS AND GRAZED DWARF-SHRUB HEATHS IN THE ROMANIAN CARPATHIANS

Floristic diversity at community level and community diversity at landscape level are presented for the main grassland and dwarf-shrub communities in the sub-alpine and alpine zones in five mountain ranges of the Romanian Carpathians. The 30 plant communities studied had their floristic composition and distribution determined by geological substratum and pedo-climatic factors. The most diverse grasslands fOxytropido-Elynehxm, Seslerio haynaldianae-Caricetuxn) were on calcareous substratum and on the mountain slopes (Testucetum pictaej, whilst the lowest diversity was in the oligo-mesotrophic sub-alpine grasslands (ScorzoneroFestucetum nigricantis, Alchemillo-Poetum alpinae, Violo-Nardetum). The Shannon-Weaver diversity index for the communities increased almost linearly with the number of species per community, whilst community diversity in the five mountain ranges was a function of the number of communities per mountain range.

SUMMARY.-Floristic diversity at community level and community diversity at landscape level are presented for the main grassland and dwarf-shrub communities in the sub-alpine and alpine zones in five mountain ranges of the Romanian Carpathians.The 30 plant communities studied had their floristic composition and distribution determined by geological substratum and pedo-climatic factors.The most diverse grasslands fOxytropido-Elynehxm, Seslerio haynaldianae-Caricetuxn) were on calcareous substratum and on the mountain slopes (Testucetum pictaej, whilst the lowest diversity was in the oligo-mesotrophic sub-alpine grasslands (Scorzonero-Festucetum nigricantis, Alchemillo-Poetum alpinae, Violo-Nardetum).The Shannon-Weaver diversity index for the communities increased almost linearly with the number of species per community, whilst community diversity in the five mountain ranges was a function of the number of communities per mountain range.

Introduction
Sub-alpine and alpine grasslands and dwarf-shrub heath communities occur at altitudes between 1700-2500 m a.s.l. in the Romanian Carpathians.In the Eastern Carpathians they can descend about 150 m lower than in the Southern Carpathians because of the more northerly latitude of the former.Sub-alpine and alpine grasslands and dwarf-shrub communities are distinctly different in physiognomy from the saxicolous or chionophilous communities of the alpine zone.Their distribution and diversity are influenced by geological and edaphic factors, topography, and climate (temperature, rainfall and wind).
The areal cover of sub-alpine and alpine grasslands and dwarf-shrub heath has been estimated at 120000 ha (PUÇCARU-SOROCEANU, 1963), which is 2% of the area of the Romanian Carpathians and 0.5% of Romania's surface area.
The sub-alpine and alpine grasslands are defined for the purposes of this study as all plant communities dominated by species of the Poaceae and Cyperaceae which are used in the summer as pastureland for sheep and horses.They comprise four main groups, namely sub-alpine grassland {Calamagrostion villosae), oligo-mesotrophic sub-alpine grasslands (Potentillo-Nardion), acid alpine grassland {Caricion curvulae) and calcicole alpine grassland {Festuco-Seslerion bielzii).Dwarf-shrub heath communities include sub-alpine dwarfshrub and alpine prostate dwarf-shrub heath {Rhododendro-Vaccinion).
Community is used inter-changeably with vegetation association in this paper.Floristic (species) diversity is used to describe floristic diversity within communities and community diversity is used to compare the diversity of individual functional vegetation groups and mountain ranges on the basis of the areal cover of the communities.All species names follow POPESCU & SANDA (1998); community names are after COLDEA (1991).
The aims of the present paper were to (a) compare species diversity among 30 sub-alpine and alpine plant communities (classified into five functional vegetation groups), (b) compare the vegetation diversity among five mountain ranges (Bucegi, Pagaras, Parang, Retezat and Rodna Mountains) and (c) compare the overall diversity of the functional vegetation types over the five mountain ranges.

Material and Method
The sub-alpine and alpine grasslands and dwarf-shrub heaths in the Rodnei, Bucegi, Pagaras, Parang and Retezat Mountains of the Romanian Carpathians (Figure 1) were selected because the vegetation types cover large areas and had been mapped to scales of 1:50000 and 1:100000 in the above ranges.This made them amenable to estimating areal cover for each community directly from the maps as opposed to other vegetation types of the alpine belt (e.g.saxicolous and chionophilous types) which tend to form only small patches of only some tens of square metres.
We chose one representative relevé for each community from published data for each of the five mountain ranges (PUÇCARU, 1956;BORZA, 1934;GHI^A, 1941;BUIA, 1962;BOÇCAIU, 1971;COLDEA 1990).Altogether 150 releves from 43 sites were included and classified into 30 communities using Sorensen similarity coefficient (COLDEA, 1991).Species diversity for individual communities was calculated by using the Shannon-Weaver index (H).For each relevé we replaced the Braun-Blanquet scores (5, 4, 3, 2, 1 and +) by the corresponding mean percentage cover values (87.5%, 62.5%, 37.5%, 17.5%, 5% and 0.1%) after TÜXEN & ELLENBERG (1937).For each community the H values were derived by averaging the diversity indices of corresponding relevés.Thereby the diversity index of a community depended on the number of the species per community and the percentage cover of each species.
The area of every community was determined by planimetry from vegetation maps at scales of either 1:50000 or 1:100000.The 30 communities were divided into five functional vegetation types.Four of these corresponded to phytosociological alliances {Canción curvulae, Calamagrostion villosae, Potentillo-Nardion and Festuco-Seslerion bielzii), whilst the fifth (Rhododendro-Vaccinion) contained the dwarf-shrub communities of three different alliances [Loiseleurio-Vaccinion, Rhododendro-Vaccinion and Junipero-Bruckenthalion (BOÇCAIU, 1971;COLDEA 1991).When calculating community diversity, we used the area measurements for each community in proportion to the total area of each functional vegetation type over the five mountain ranges, or the total area occupied by the sub-alpine and alpine communities in each mountain range after THOMPSON & BROWN (1992).The Shannon-Weaver index was calculated for every mountain range/functional vegetation group according to the formula: where s is the range of communities present at each functional vegetation group, or mountain range and P. is the proportion of the areal coverage of community i within the total area of the functional group over the five mountain ranges, or to the total area within each mountain range.

Species diversity
Table 1 gives the classification of the 30 communities, with data about altitude, species richness and number of endemics in each community.
The mean H diversity index calculated for each community had values between 1.31 and 2.41 (Table 1).The lowest indices were found in the Scorzonero-Festucetum nigricantis (1.31), Alchemillo-Poetum alpinae (1.33) and Violo-Nardetum (1.53) communities in the anthropogenic grasslands, which are intensively grazed and consequently have a high sheep manure supply.Therefore, in these communities, belonging to Potentillo-Nardion alliance, the syndynamic evolution is determined by the nutrient content of soil.

Community diversity in the five mountain ranges
The H diversity index for each mountain range was a function of the prevalent geological and pedological characters and the number of plant communities present.
The highest values of the index were estimated in the Rodnei (0.725) and the Pagaras Mountains (0.692), where the highest number of plant communities were found (22 and 21, respectively) (Figure 2).In these mountains Mesozoic limestone dominates over large areas along with acid crystalline rocks.Slightly The combination of a lower number of communities ( 15) and the predominance of one of them, the Violo-Nardetum (85 %) resulted in the

Community diversity in the five grassland fiinctional groups
The relative percentage cover of each of the 30 communities combined over the five mountain ranges is shown in Figure 2. Eleven communities comprised 94.4% of the total cover with the other 19 communities covering 5.6%.The Violo-Nardetum (39.4%),Potentillo-Festucetum (18.8%) and Scorzonero-Festucetum nigricantis (13.1%) were by far the commonest types and accounted for 71.3% of the total areal cover.
The Violo-Nardetum and Scorzonero-Festucetum nigricantis belong to the oligo-mesotrophic sub-alpine grasslands which shows that this functional group was by far the most dominant vegetation type in the five mountain ranges.

The main sources of diversity
The main sources of diversity in the sub-alpine and alpine vegetation of the Romanian Carpathians are parent rock type, soil, topography and climatic factors (temperature, rainfalls, wind).These factors alone, or in combination influence species diversity and community diversity on a landscape scale.
In addition to the above primary factors, there are secondary factors which affect species and vegetation diversity {cf.CHANETON & PACELLI, 1991;KWIATKOWSKA, 1994).Human impact has had a direct influence on soil (c) Consejo Superior de Investigaciones Científicas Licencia Creative Commons 3.0 España (by-nc) http://pirineos.revistas.csic.esnutrient status and through land use has caused the appearance of new functional groups such as the Potentillo-Nardion and Calamagrostion (and the communities therein).The anthropic factor has also greatly enhanced the spreading of the dwarf-shrub communities in the sub-alpine zone following the clearing of the native woody vegetation {Rhododendro-Pinetum mugi and Bruckenthalio-Piceetum).For all the human influence over the centuries, however, the alpine and sub-alpine habitats in the Carpathians are the least altered habitats in Romania.
In conclusion, the floristic composition and community structure of the subalpine and alpine grasslands and dwarf-shrub in the Romanian Carpathians are mainly determined by geological and pedo-climatic conditions.The alpine grasslands on calcareous substratum (Festuco^Seslerion bielzii) and the typical sub-alpine ones (Calamagrostion villosae) have the highest diversity index, while oligo-mesotrophic sub-alpine grassland {Potentillo-Nardion), determined by soil trophicity have the lowest diversity index.
from the Bucegi, Pagaras, Parang, Retezat and Rodnei Mountains were used to calculate the Shannon-Weawer diversity indices for each community.The diversity values are means based on one relevé from each of the five mountain ranges.

Table 1 .
The altitudinal range, species richness (with the number of endemics per conurvunity) and the Shannon-Weawer diversity index values of the 30 sub-alpine and alpine grassland and dwarf-shrub communities identified in five mountain ranges of the Romanian Carpathians.AND COMMUNITY DIVERSITY OF SUB-ALPINE AND ALPEsIE GRASSLANDS.

Table 2 .
Shannon-Weawer diversity indices (H) for the five grassland functional groups of Romanian Carpathians