Stem growth and canopy dynamics in a world-wide range of Fagus forests

Abstract. Forests dominated by Fagus (beech) occur widely in the Northern Hemisphere. Tree species dominant together with beech vary in tolerance of understorey conditions. They are deciduous broad-leaved, evergreen broad-leaved or evergreen coniferous. The frequency and intensity of events that reduce the forest canopy cover are important determinants of the ratio of beech to other species in the canopy. For trees in the understorey and the canopy, stem diameter growth rate is determined by light regime and growing space which in turn are determined by canopy cover. We evaluated increase in stem diameter growth rate as an indicator of sudden reductions in canopy cover and canopy dynamics. We used tree-ring chronologies and calculated an index of growth rate increase (GI) to compare the canopy dynamics of 11 natural beech forests. Per site, the annual average value of GI poorly reflected the effects of dry or cool summers, and it clearly reflected events like tornados and hurricanes that removed substantial canopy cover. Among groups of sites average values of GI were significantly different. In the sites with a lower level of average GI, the establishment of the more shade tolerant tree and shrub species in the understorey was favoured, and subcanopy layers became more dense. On the other hand, higher levels of average GI allowed for more light demanding tree species to reach the canopy.     

Relative genetic diversity of the rare and endangered Agave shawii ssp. shawii and associated soil microbes within a southern California ecological preserve

Shaw''s Agave (Agave shawii ssp. shawii) is an endangered maritime succulent growing along the coast of California and northern Baja California. The population inhabiting Point Loma Peninsula has a complicated history of transplantation without documentation. The low effective population size in California prompted agave transplanting from the U.S. Naval Base site (NB) to Cabrillo National Monument (CNM). Since 2008, there are no agave sprouts identified on the CNM site, and concerns have been raised about the genetic diversity of this population. We sequenced two barcoding loci, rbcL and matK, of 27 individual plants from 5 geographically distinct populations, including 12 individuals from California (NB and CNM). Phylogenetic analysis revealed the three US and two Mexican agave populations are closely related and have similar genetic variation at the two barcoding regions, suggesting the Point Loma agave population is not clonal. Agave‐associated soil microbes used significantly more carbon sources in CNM soil samples than in NB soil likely due to higher pH and moisture content; meanwhile, soil type and soil chemistry analysis including phosphorus, nitrate nitrogen, organic matter, and metals revealed significant correlations between microbial diversity and base saturation (p < 0.05, r ² = 0.3676), lime buffer capacity (p < 0.01, r ² = 0.7055), equilibrium lime buffer capacity (p < 0.01, r ² = 0.7142), and zinc (p < 0.01, r ² = 0.7136). Soil microbiome analysis within the CNM population revealed overall expected richness (H′ = 5.647–6.982) for Agave species, while the diversity range (1 − D = 0.003392–0.014108) suggests relatively low diversity marked by high individual variation. The most prominent remaining US population of this rare species is not clonal and does not seem to be threatened by a lack of genetic and microbial diversity. These results prompt further efforts to investigate factors affecting Agave''s reproduction and fitness.     

The taxonomy of Campylopus pyriformis (Schultz) Bridr and related species

Abstract

Twenty-five species of mosses collected in Costa Rica, mostly in 1965, are recorded. Leptodontium ramosum, remarkable for its peg-like gemmae borne on stout leafless branches, Sematophyllum serrulatum and Trichosteleum sarapiquensis are described as new species.     

The world-wide web and plant molecular biology

The Internet has been functional since 1967 and has been operating without interruption for over 20 years. Although local service can be lost, the network will retain its integrity and recover from almost any imaginable combination of faults, whether natural or intentional. This robustness, the global scope, the availability of quality public domain software, and the inherent democracy of the Internet, have combined to eclipse similar efforts. Many scientists have found the Internet immediately useful for communication in the form of electronic mail. Shared resources, an intrinsic benefit of networks, are now becoming apparent in the form of the World-Wide Web (WWW).     

The molecular-weight range of mucosal-heparin preparations.

A recently reported method describes the determination of the molecular-weight range of heparins by using an electrofocusing procedure to isolate individual molecular species. Commercially available heparins were fractionated on a column of polyacrylamide-agarose gel to give fractions whose molecular weights were estimated by viscometry. Fractions with mutually exclusive molecllar-weight ranges gave an appreciable number of common bands when subjected to the electrofocusing procedure; therefore, each of these bands cannot be formed from a single molecular species of heparin. Other mucopolysaccharides also gave band sequences indistinguishable from those of heparin; they differed in position and intensity with different ampholyte batches, and probably arose from individual molecular species of the ampholyte rather than the mucopolysaccharide. The molecular-weight range of the heparin was observed to be broader than that usually reported.     

The habitat range of Dicranum leioneuron Kindb.

Abstract

The hepatic Nardia insecta Lindb. is reported from a streamside locality in the Kielder district of South Northumberland, new to Britain. It was first collected in 1964 when herbarium specimens were initially referred to N. geoscyphus. Plants of N. insecta were refound in 1993 at the same locality where it has persisted while conifer plantations have developed in the surrounding catchment. N. insecta from Northumberland is described and illustrated, and a chromosome count of n = 18 is reported. It is compared with N. geoscyphus which has been found to be represented in the British Isles by two forms that differ in morphology and geographical distribution.     

The phenotypic range of hemophilia A carriers.

We have described the study of a small kindred with X-linked hemophilia A. It was ascertained through a clinically affected female, the daughter of a man with moderately severe hemophilia. The pedigree and the proband's phenotype suggest that she may be a heterozygote in whom most of the normal alleles at the VIII-1 locus are not active. She has two sisters, also obligatory carriers. The three sisters exhibit the three phenotypes possible for heterozygous females: clinically affected, clinically normal but phenotypically abnormal as determined by laboratory tests, and clinically and phenotypically normal.     

The world-wide pandemic and drug resistance of the causative agent of Grigor'ev-Shiga dysentery

One of the factors facilitating the global pandemic of Grigor'ev-Shiga dysentery is considered in detail. All Shigella dysenteriae 1 strains, irrespective of the geographical zone of their spread, showed medicinal resistance. As pandemic developed, the spectrum of medicinal resistance constantly increased in all hyperendemic foci. The presence of pronounced relationships between the strains circulating in each of three hyperendemic foci and the strains circulating in different hyperendemic foci could be observed. The necessity of paying greater attention to this dangerous infectious disease, and especially to the problems related to the medicinal resistance of its causative agents, is emphasized.     

A world-wide study of high altitude treeline temperatures

Aim At a coarse scale, the treelines of the world's mountains seem to follow a common isotherm, but the evidence for this has been indirect so far. Here we aim at underpinning this with facts. Location We present the results of a data‐logging campaign at 46 treeline sites between 68° N and 42° S. Methods We measured root‐zone temperatures with an hourly resolution over 1–3 years per site between 1996 and 2003. Results Disregarding taxon‐, landuse‐ or fire‐driven tree limits, high altitude climatic treelines are associated with a seasonal mean ground temperature of 6.7 °C (±0.8 SD; 2.2 K amplitude of means for different climatic zones), a surprisingly narrow range. Temperatures are higher (7–8 °C) in the temperate and Mediterranean zone treelines, and are lower in equatorial treelines (5–6 °C) and in the subarctic and boreal zone (6–7 °C). While air temperatures are higher than soil temperatures in warm periods, and are lower than soil temperatures in cold periods, daily means of air and soil temperature are almost the same at 6–7 °C, a physics driven coincidence with the global mean temperature at treeline. The length of the growing season, thermal extremes or thermal sums have no predictive value for treeline altitude on a global scale. Some Mediterranean (Fagus spp.) and temperate South Hemisphere treelines (Nothofagus spp.) and the native treeline in Hawaii (Metrosideros) are located at substantially higher isotherms and represent genus‐specific boundaries rather than boundaries of the life‐form tree. In seasonal climates, ground temperatures in winter (absolute minima) reflect local snow pack and seem uncritical. Main conclusions The data support the hypothesis of a common thermal threshold for forest growth at high elevation, but also reflect a moderate region and substantial taxonomic influence.     

The pattern of runs of homozygosity and genomic inbreeding in world-wide sheep populations

Genome-wide pattern of runs of homozygosity (ROH) across ovine genome can provide a useful resource for studying diversity and demography history in sheep. We analyzed 50 k SNPs chip data of 2536 animals to identify pattern, distribution and level of ROHs in 68 global sheep populations. A total of 60,301 ROHs were detected in all breeds. The majority of the detected ROHs were <16 Mb and the average total number of ROHs per individual was 23.8 ± 13.8. The ROHs greater than 1 Mb covered on average 8.2% of the sheep autosomes, 1% of which was related to the ROHs with 1–4 Mb of length. The mean sum of ROH length in two-thirds of the populations was less than 250 Mb ranging from 21.7 to near 570 Mb. The level of genomic inbreeding was relatively low. The average of the inbreeding coefficients based on ROH (F_ROH) was 0.09 ± 0.05. It was rising in a stepwise manner with distance from Southwest Asia and maximum values were detected in North European breeds. A total of 465 ROH hotspots were detected in 25 different autosomes which partially surrounding 257 Refseq genes across the genome. Most of the detected genes were related to growth, body weight, meat production and quality, wool production and pigmentation. In conclusion, our analysis showed that the sheep genome, compared with other livestock species such as cattle and pig, displays low levels of homozygosity and appropriate genetic diversity for selection response and genetic merit gain.     

The mutation range ofBrevibacterium sp. M27

The mutation range was studied inBrevibacterium sp. M27 after UV irradiation and after treatment with N-methyl-N’-nitro-N-nitrosoguanidine. The induction of auxotrophic mutants and mutants resistant to streptomycin and tetracycline was investigated. A collection of auxotrophic mutants for the studies of genetic transfer in this model was prepared.