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Concerns about decline in soil fertility and long-term productivity of fast-growing plantations have promoted interest in using nitrogen-fixing trees in mixed species plantations. Populus deltoides and Alnus subcordata were planted in five proportions (100P, 67P:33A, 50P:50A, 33P:67A, 100A) in Noor, Iran. After 7 years, the effects of species interactions on tree growth and nutrient concentration in live and senescent leaves and soil properties were assessed. Diameter at breast height and total height of individual Populus trees were positively affected by the presence of Alnus. Nitrogen concentrations in fully expanded and senescent leaves of Populus were higher in mixed plantations than monoculture plantations. The results of nutrition and nutrient return and growth indicated that mixed plantations of these two species were more productive and sustainable than their monoculture plantations. Within the framework of this experiment, it appeared that production was maximized when these two species were grown together in the relative proportions of 50% Populus and 50% Alnus.

Humus forms are good indicators of environmental conditions and thus important in forest ecological processes. Altitudinal gradients are considered as natural laboratory for evaluating soil ecological processes and humus form distribution. The objective of this study was to evaluate the macromorphology of humus forms along an altitudinal gradient (0-2000 m a.s.l.) covered with plain forest, mixed and pure forests and forest-grassland ecotone, in Alborz Mountains in northern Iran. In total, 225 humus profiles were evaluated. Forest stand variables including tree density, basal area, crown density, and height, forest floor and soil physico-chemical properties along with biological features were measured. We found that altitudinal gradients influence both humus forms distribution and soil properties but with different mechanisms. While soil properties (i.e., temperature, pH, CaCO3, soil N content, soil C/N and microbial biomass N) were significantly correlated with altitude, the forest floor properties were more influenced by tree species composition. Particularly, the abundance of Mull was decreased in plain mixed forests compared to mountain pure forests, whereas the frequency of Amphi was increased. Moreover, Oligomull and Leptoamphi were abundant in mixed beech forests, while Eumacroamphi, Eumesoamphi and Pachyamphi were only observed in pure beech forests. Such a distribution influenced soil fertility where higher values of nitrogen (N), microbial biomass nitrogen (MBN) and pH were observed at lower altitudes under mixed forests compared to pure forests at higher altitudes. [ABSTRACT FROM AUTHOR]

The objective of the present study was to evaluate how altitudinal gradients shape the composition of soil bacterial and fungal communities, humus forms and soil properties across six altitude levels in Hyrcanian forests. Soil microbiomes were characterized by sequencing amplicons of selected molecular markers. Soil chemistry and plant mycorrhizal type were the two dominant factors explaining variations in bacterial and fungal diversity, respectively. The lowest altitude level had more favorable conditions for the formation of mull humus and exhibited higher N and Ca contents. These conditions were also associated with a higher proportion of Betaproteobacteria, Acidimicrobia , Acidobacteria and Nitrospirae. Low soil and forest floor quality as well as lower bacterial and fungal diversity characterized higher altitude levels, along with a high proportion of shared bacterial (Thermoleophilia , Actinobacteria and Bacilli) and fungal (Eurotiomycetes and Mortierellomycota) taxa. Beech-dominated sites showed moderate soil quality and high bacterial (Alphaproteobacteria, Acidobacteria, Planctomycetes and Bacteroidetes) and fungal (Basidiomycota) diversity. Particularly, the Basidiomycota were well represented in pure beech forests at an altitude of 1500 m. In fertile and nitrogen rich soils with neutral pH, soil quality decreased along the altitudinal gradient, indicating that microbial diversity and forest floor decomposition were likely constrained by climatic conditions. [ABSTRACT FROM AUTHOR]

The present study examined the effect of land covers on some of soil quality properties. For this purpose three plantation stands (i.e., Alnus subcordata L., Poplus deltoids L. and Taxadium distichum L. Rich) and an uncultivated land (control area) were considered. Soil samples were collected at two different depths (0-15 and 15-30 cm) and characterized with respect to water content, pH, texture, total organic carbon and nutrient stocks (N, P, K, Ca and Mg). Our findings showed that the highest values of sand, clay and total organic carbon were detected in Alnus subcordata L., Poplus deltoids L. and Taxadium distichum L. Rich, respectively. Whereas the highest of pH, water content and silt were observed in the control area. Measurements of soil nutrient stocks showed that fertility decreased in relation to increased soil depth, with significant differences depending on soil depth. As a conclusion, the broad-leaved species were more successful about most of nutrient stocks than needle-leaved stand and control area. [ABSTRACT FROM AUTHOR]

The present study involves the soil seed bank flora of the Sisangan Box tree (Buxus hyrcanus Pojark) reserve by using seedling emergence method. 150 soil samples were collected during late June and early November by hammering a hollow metal frame 400 cm2 to a depth of 5 cm. Results showed 67 species, representing 63 genera and 38 families germinated from soil seed bank. 45 species belonging to 28 families and 59 species belonging to 32 families were recorded in June and November soil seed bank respectively. The largest families were Asteraceae (7 species, 10.5%), Lamiaceae (6 species, 9%), Poaceae (5 species, 7.5%) and Rosaceae (4 species, 6%) which compromised 32.8% percent of the total species in the soil seed bank. Results also showed that Hemicrptophytes (28.4%) and Euro-Sibria elements (23/9%) were the most important biological spectrum and phytochorion respectivly in the soil seed bank of Sisangan forest. From the total number of species recorded in seed bank, 30 species (44.6 %) were found only in the seed bank and never observed in above-ground vegetation. In this regard, seeds of 10 woody species including Albizia julibrissin, Ficus carica, Morus alba, Diospyrus lotus, Celtis australis, Gleditsia caspica, Buxus hyrcana, Ulmus minor, Zelkova carpinifolia and Carpinus betulus were found in the soil seed bank, from which only 6 species were able to produce persistent soil seed bank. This condition confirmed low similarity between above-ground vegetation and persistent soil seed bank and it also reiterated the importance of soil seed bank study for introducing more accurate capacity of plant biodiversity. [ABSTRACT FROM AUTHOR]

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Copyright of Botanica Serbica is the property of University of Belgrade, Institute of Botany & Botanical Garden Jevremovac and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The phytosociological studies were performed for an identification of the indicator fern the species of beech forests in the central Caspian Hyrcanian forests in Iran. For data analysis the Braun-Blanquet method with Ellenberg table was used. The results show that these beech forest have six associations; two sub associations and one variant. 12 fern species exist in the study area out of which 6 are indicator species of beech vegetation association. Pteridium aquilinum and Asplenium adianthum nigrum are indicator species of the Fageto-Carpinetum association. Polystichum acleatum is an indicator species of the Fagetum orientalis typical sub association. Polystichum ofilliricum is an indicator species of the Fagetum orientalis lathyretosum sub association. Phyllitis scolopondrium and Asplenium adianthum are indicator species of the Buxo-Fagetum association. [ABSTRACT FROM AUTHOR]

Wild almond (Amygdalus scoparia) is a dominant shrub species in mountain forests of the Irano‐Turanian region. Dieback and decline symptoms of wild almond shrubs were first observed in Harat protected forest (Yazd, Iran) in the autumn of 2014. Since then, the incidence and severity of the disease have increased. To study the aetiology and estimate losses from the disease, field studies were conducted in 2016 and 2017. For this purpose, eight stands were selected, in which 24%–99% of the trees were wild almond in their species composition. In total, 50 cankers and 50 infected twigs of wild almond shrubs were collected. Fungal isolates were identified based on morphological and cultural characteristics, as well as sequence data of ITS1 + 5.8S + ITS2 rDNA. Pathogenicity of fungi was checked on detached shoots and evaluated after 40 days by measuring the discoloured lesion length at the inoculation site. Among 681 wild almond shrubs checked, 84.44% showed decline symptoms with different severities; only 15.56% did not show observable disease symptoms. The most frequent colonizers of infected tissues taken from cankers were Wilsonomyces carpophilus (56%), Thyrostroma cornicola (40%) and Collophorina paarla (30%). Infected twigs were extensively colonized by W. carpophilus (36%), Th. cornicola (24%) and Ulocladium consortiale (24%). Other species, such as Endoconidioma populi, Microsphaeropsis olivacea, Trichoderma asperellum, Paecilomyces formosus, Saccothecium rubi, Preussia sp. and Chaetomium globosum, had lower isolation frequencies. W. carpophilus, Th. cornicola, C. paarla and U. consortiale were found as pathogens on detached wild almond shoots. Based on the frequency of the isolates and the pathogenicity tests, four fungi, such as W. carpophilus, Th. cornicola, C. paarla and U. consortiale, are considered serious contributing agents playing a significant role in the dieback and decline of wild almond. All isolated species are reported for the first time on the wild almond shrubs of the world. [ABSTRACT FROM AUTHOR]