We compared the structure of microfungal communities in two contrasting microsites under Mediterranean climate in the Alma Kerem-Ben-Zimra area, eastern Upper Galilee, Israel. The sites are located within a distance of 30-50 m from one another and are characterized by strongly contrasting soils and bedrock lithology. The area is composed of Early Pleistocene basalt and tuffs interspersed with Senonian soft chalk. Pale rendzina soils formed on chalk (CR) while black soils formed on basalts (BB). The rendzina soil is covered mainly by Sarcopterium spinosum, whereas on basaltic soil, Carlina hispanica plant formations developed. The pristine Mediterranean maquis was completely destroyed by long-term modern management and ancient agricultural clearings at least since Byzantine times (Horowitz, 1979). Presently the land is used for grazing. The soil profiles were described in the field. Several soil properties (moisture, magnetic susceptibility, and some others) were measured in the laboratory. The samples for mycological analysis (48 total) were collected both in the rainy winter (January) and dry summer (August) from the A0A1 upper soil horizon in sunny, open localities and shady localities under shrubs. The microfungal communities in the drier CR soil are purer (72 species), less heterogeneous, and less even (the Shannon and evenness indexes: 2.12 and 0.513 sunny, 0.98 and 0.260 - shady) than the communities in the clayey wetter BB soil (96 species; 2.39 and 0.582 sunny, 1.69 and 0.396 - shady). In CR, differences between sunny and shady microfungal communities both at the diversity level and in structure (prevalence of melanin-containing species in the sunny localities, and Penicillium spp. in the shady) are much more pronounced than in BB (such structural variations were revealed only in the winter). All studied communities are dominated by Penicillium janthinellum in varying degrees (till 80% of all isolates in the CR shady locality), while co-dominant species are different: Phoma eupyrena in the CR soil, and Cladosporium cladosporioides, Fusarium equisetii in the BB soil.
Because one and the same species is markedly dominating in all localities, and this fungus as well as its co-dominant species are known to be distributed worldwide and are common both in virgin and arable soils (Domsch et al., 1980), we suggest that prolonged agricultural activity in the studied area has resulted in a decreasing diversity level and in the simplification of the structure of microfungal communities. These results are in accordance with a similar tendency found by mycologists working in different regions with disturbed soils (e.g., Wicklow and Whittingham, 1978; Zak, 1992, Grishkan and Nevo, 2004; Marfenina, 2005). It is known also that an anthropogenic impact may mask the pristine differentiating effect of soil diversity on the structure of microfungal communities (Marfenina, 2005). Because of this fact, similarity between studied communities (based on the relative abundances of common species) is high and exceeds 60%, thus showing a convergence in the composition of fungal complexes.
KEY WORDS: basalt soil, chalk rendzina, Mediterranean climate, microfungal communities, agricultural impact