Vegetation Diversity Patterns Research Articles

EFFECT OF ASPECTS, ELEVATION, AND SLOPE GRADIENT ON ZAWITA FOREST UNDERSTORY VEGETATION COMPOSITION

Vegetation diversity patterns are necessary to identify species of plants in the Zawita mountains area, Duhok Governorate, Iraq, to investigate the influence of topographical elements (aspects - north and south, elevations and slope gradients) on diagnosis, density, frequency, and species richness and diversity of species in the Zawita forest understory vegetation. Sampling vegetation was surveyed at (1 * 1 m-2), for 8 quadrats per each zigzag transect. The data were designed with a strip-strip block design, with four replicates for each transect. The results revealed significant differences in frequency, density, and Shannon index due to aspects, elevations, and slope gradient. While other measured traits, species richness, and Simpson index were not affected significantly. The highest density was recorded for the north-facing aspect at high altitude while the Shannon index diversity has existed in the south aspect at low elevation and low slope gradient.

Patterns of vegetation diversity of grasslands and pastures Crvanj Mt. (Herzegovina, Western Balkan)

This paper represents study results of patterns of structure and dynamics of grasslands and pastures communities on vertical profile of Crvanj Mt. in Herzegovina (W. Balkan. Investigated area is situated between co-ordinates N 43° and 43°30' and E 18° and 18°30'. From the orography point of view, the area is very heterogenous. It encompases numerous peaks, valleys, passages and diverse karst formations. The highest peak is Zimomor (1920 m), while the lowest point is Ulog (670 m). The area is also very heterogenous from standpoint of geology. Thus, here occur marls, calcarenits, limestones, sandstones and dolomites. From division of automorphous soils it occur calcocambisol, calcomelanosol and luvisol on limestone, while distric cambisol and ranker occur on ingenious rocks. The most frequent among hydromorphous soils here are pseudogley, eugley, histosol (peat) and fluvisol. Ecoclimate is humid and perhumid, and in terms of temperature it is moderately warm to moderately cold. Mean annual temperature varies between 8.5°C on the foot of mountain and 2.0°C in the highest zone. Annual precipitation is 1700 mm, reaching maximum values in autumn and winter. Detected are grassland and pasture communities belonging to nine different alliances, five orders and three classes. It is described new community Asphodelo-Agrostietum capillaris Redzic ass. nova hoc loco from the alliance Festuco-Agrostion capillaris, order Festuco-Agrostietalia and community of Scillo litardierei-Molinietum coeruleae Redzic ass. nova hoc loco of the class Molinio-Arrhenatheretea and community Eriophoro latifolii-Menyanthetum trifoliati Redzic ass. nova hoc loco from the alliance Caricion davallianae, order Caricetalia davallianae of the class Scheuchzerio-Caricetea fuscae. Other important communities are endemic and relict, such as: Carici caryophyllei-Scabiosetum leucophylae, Bromo-Plantaginetum mediae „subalpinum“, Saturejo-Edraianthetum, Danthonio-Scorzoneretum villosae, Molinietum coeruleae„ illyricum“ and Hypochoereto-Crepidetum conyzifoliae. Key words: Biodiversity, syntaxonomy, habitat classification, wetland, calcareous grasslands, Dinaric Alps.

How does forest landscape structure explain tree species richness in a Mediterranean context?

Although the strong relationship between vegetation and climatic factors is widely accepted, other landscape composition and configuration characteristics could be significantly related with vegetation diversity patterns at different scales. Variation partitioning was conducted in order to analyse to what degree forest landscape structure, compared to other spatial and environmental factors, explained forest tree species richness in 278 UTM 10 × 10 km cells in the Mediterranean region of Catalonia (NE Spain). Tree species richness variation was decomposed through linear regression into three groups of explanatory variables: forest landscape (composition and configuration), environmental (topography and climate) and spatial variables. Additionally, the forest landscape characteristics which significantly contributed to explain richness variation were identified through a multiple regression model. About 60% of tree species richness variation was explained by the whole set of variables, while their joint effects explained nearly 28%. Forest landscape variables were those with a greater pure explanatory power for tree species richness (about 15% of total variation), much larger than the pure effect of environmental or spatial variables (about 2% each). Forest canopy cover, forest area and land cover diversity were the most significant composition variables in the regression model. Landscape configuration metrics had a minor effect on forest tree species richness, with the exception of some shape complexity indices, as indicators of land use intensity and edge effects. Our results highlight the importance of considering the forest landscape structure in order to understand the distribution of vegetation diversity in strongly human-modified regions like the Mediterranean.

Diversity of plant communities in coastal salt marshes habitat in Kuwait

Integration phytosociology combined with traditional measures of diversity is used to describe the patterns of vegetation diversity along the coastal salt marshes of Kuwait. This study assesses the plant communities and the environmental factors that govern species diversity and distribution in the coastal salt marshes using TWINSPAN, DCA, and regression analysis. The results focus on: (1) the environmental gradients observed are very complex; (2) stressful environments support low plant species diversity but high dominance; also, (3) natural factors (substrate and climate) are important at the zonation and diversity of plant community by changing in the habitat formation. Six vegetation groups were identified at level 3 of TWINSPAN. (I)Halocnemum strobilaceum-Juncus arabicus, (II)Halocnemum strobilaceum-Suaeda vermiculata, (III)Nitraria retusa-Zygophyllum qatarense, (IV)Zygophyllum qatarense-Haloxylon salicomicum, (V)Nitraria retusa, (VI)Tamarix aucherana. The community diversity is negatively correlated with soil salinity, moisture, organic matter, fine texture, minerals, and plant cover and positively correlated with sand. Community diversity is consistently affected by the result of active sand deposition and process of hummock formation (Nabkas). These results are discussed in terms of competition adaptation theory.