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Early-successional stages of woody vegetation on gravel bars were studied in an island-braided section of the River Tagliamento in northeastern Italy. We mapped landscape-level changes in the study area (125 ha) by GIS-based analysis of aerial photographs for two time periods (1984–1986, 1986–1991); we surveyed island vegetation, and estimated island age by tree ring analysis. The study area experienced considerable changes between 1984 and 1991 due to at least two major floods in 1987 and 1990. The development of woody vegetation on bars follows three distinct phases: (1) gravel bars plus large woody debris (LWD), (2) pioneer islands, and (3) established islands. Established islands have sections dominated by shrubs of Salix elaeagnos, S. purpurea, S. daphnoides and S. triandra, and tree-dominated sections with Populus nigra, Salix alba and Alnus incana. Large woody debris seems to play a key role for plant colonization on gravel bars. The succession from bars to established islands took about 10 - 20 yr, and the probability of an island being washed away decreased with island age. Erosion produced new LWD which again initiated successional processes in the active zone of the river. Most species were already present in the early-successional stages, although the number of species increased with island development. Established islands were characterized by a distinctive species composition, including an assemblage of species less tolerant of inundation. The results are discussed within the framework of island dynamics and its significance for restoration of early-successional habitats in more regulated rivers.

Phenotypic and genotypic methods were used to prove the existence of Frankia strains isolated from an Elaeagnus sp. that are able to cross the inoculation barriers and infect Alnus spp. also. Repeated cycles of inoculation, nodulation, and reisolation were performed under axenic conditions. Frankia wild-type strain UFI 13270257 and three of its coisolates did exhibit complete infectivity and effectiveness on Elaeagnus spp. and Hippophaë rhamnoides and variable infectivity on Alnus spp. Microscopical observation of host plant roots showed that these strains are able to infect Alnus spp. by penetrating deformed root hairs. Reisolates obtained from nodules induced on monoxenic Alnus glutinosa, Alnus incana, and Elaeagnus angustifolia resembled the parent strains in host infectivity range, in planta and in vitro morphophysiology, isoenzymes, and nif and rrn restriction fragment length polymorphisms, thus fulfilling Koch's postulates on both host plant genera. Alnus and Elaeagnus group-specific polymerase chain reaction DNA amplifications, DNA-DNA hybridizations, and partial gene sequences coding for 16S rRNA provided evidence for the genetic uniformity of wild-type strains and their inclusion into one and the same genomic species, clearly belonging to the Elaeagnus group of Frankia species.

Vertical distribution of soil biota is not well understood. Here we studied the development of vertical distribution of soil chemical and biological properties in two post-mining chronosequnces in heaps after open cast coal mining, one left to succession (sites 20, 35 and 60 years old) and one reclaimed by levelling and Alder (Alnus glutinosa and Alnus incana) afforestation (sites 10, 25, 40, and 60 years old) near Sokolov, Czechia. When spoil material is compacted during levelling and afforestation, as in reclaimed sites, the effect of time in soil biota development was less important than in spontaneous succession where no compaction occurs. Soil depth was a stronger explanatory factor in explaining the soil microbial biomass variations under reclamation regimes while comparatively less strong under spontaneous succession which points at the impact of spoil compaction on vertical development of organisms. Spontaneous succession encourages a more diverse and dynamic vertical, as well as horizontal, faunal community development, especially across time. Breaking down fauna into ecological subgroups, time was more of an important factor for fauna active below ground (endogeic), than for surface-dwelling fauna likely due to further soil profile development by time. Calculated depth in which 90% individuals occur shows that considering only the depth of 0–10 cm overlooks a substantial part of some faunal groups (e.g. Pauropoda and Symphylan) that are abundant in deeper layers. Soil depth is also more of a strong predictor of soil biota than soil C content, indicating that the population decrease in soil biota community with depth cannot be explained only by decreasing organic matter content.

Symbiotic and free-living Frankia were investigated for correlation between hydrogenase activities (in vivo/in vitro assays) and for occurrence and localization of hydrogenase protein by Western blots and immuno-gold localization, respectively. Freshly prepared nodule homogenates from the symbiosis between Alnus incana and a local source of Frankia did not show any detectable in vivo or in vitro hydrogenase uptake activity, as also has been shown earlier. However, a free-living Frankia strain originally isolated from these nodules clearly showed both in vivo and in vitro hydrogenase activity, with the latter being approximately four times higher. Frankia strain Cpl1 showed hydrogen uptake activity both in symbiosis with Alnus incana and in a free-living state. Western blots on the different combinations of host plants and Frankia strains used in the present study revealed that all the Frankia sources contained a hydrogenase protein, even the local source where no in vivo or in vitro activity could be measured. The 72 kilodalton protein found in the symbiotic Frankia as well as in the free-living Frankia strains were immunologically related to the large subunit of a dimeric hydrogenase purified from Alcaligenes latus. Recognitions to polypeptides with molecular masses of about 41 and 19.5 kilodaltons were also observed in Frankia strain UGL011101 and in the local source of Frankia, respectively. Immunogold localization of the protein demonstrated that in both the symbiotic state and the free-living nitrogen-fixing Frankia, the protein is located in vesicles and in hyphae. The inability to measure any uptake hydrogenase activity is therefore not due to the absence of hydrogenase enzyme. However, the possibility of an inactive hydrogenase enzyme cannot be ruled out.

During floristic and vegetational research of the region in Croatia to the north from the Sava River, Equisetum hyemale has been discovered in further 12 new localities. In the Repaš forest area, fragments of the Equiseto-Alnetum incanae association have been registered, constituting its furthermost point of expansion to the East.

We present the first estimates of speciated monoterpene emissions from the North European coniferous forests. Measured emission factors and emission profiles of boreal tree species (Picea abies, Pinus sylvestris, Betula pendula, Salix phylicifolia, Populus tremula, and Alnus incana) were used together with detailed satellite land cover information and meteorological data in an emission model based on the Guenther emission algorithms. The variation of the coniferous biomass within the boreal region (60°N to 70°N) was obtained from forest inventory data, and the seasonal variability of the deciduous biomass was taken into account through simple boreal climatology parameterisation. The annual biogenic emissions in the boreal zone are dominated by coniferous species, but in the summer months, the deciduous contribution to the monoterpene and isoprene emissions is considerable. Norway spruce (Picea abies) is the most important isoprene emitter in the north European boreal forests. The biogenic emission fluxes in the South boreal zone are approximately twice as high as fluxes in the North boreal zone. α- and β-pinene, carene, and cineole are the most abundant emitted terpenes, with a strong contribution of isoprene and linalool during the summer months.

ALTHOUGH arginine has been recognized as a constituent of higher plants for many years, both as a structural unit in the protein and as the free amino-acid, two other components of the ‘ornithine cycle’ of animals, citrulline and ornithine, were not considered to be normal constituents of these plants. Wada, in 1930, isolated citrulline from Citrullus vulgaris Schrad.; but it was not again reported in higher plants until 1952, when Virtanen and Miettinen1 detected it in Alnus incana L. and Alnus glutinosa L. Citrulline is now known to occur as a free amino-acid in plants of a number of families.

Alnus incana nodules were incubated in situ and assayed for nitrogen-fixing activity by the acetylene reduction method. The effects of air and soil temperature and light intensity (at the tree stem) on the acetylene reduction activity were examined, and diurnal and seasonl fluctuations in acetylene reducing activity were studied. Rates of acetylene reduction obtained varied between 0.4 and 84.8 Rmoles of ethylene per g dry weight of nodule per h with a seasonal average of 8.6 moles g-l h-1. Based on field assays an annual rate of fixation of 43 kg N/ha was estimated for a 30 year old A. incana stand.

Stratification caused the germination capacity of freshly collected grey alder (Alnus incana) seed rise from 29 % to 32% and that of black alder (Alnus glutinosa) from 28 % to 35 %. Germination increased to 48 % and 46 %, respectively, as a result of a three-day exposure to -20'C. Best results were obtained when the germination media had a pH of 4-5. Under natural conditions seedling survival of grey alder was considerably better in mineral soil (33 % and 36%) than in humus (3% and 15%). The classification of seed qualities on the basis of X-ray examinations gave results similar to those obtained by other methods. Pe3ioMe