Frequent fires may alter the future composition of the boreal forest in northern Mongolia

To examine the effects of frequent fires on species composition of the boreal forest in northern Mongolia, we investigated regeneration patterns, including reproductive pathways, post-fire seed sources, and site preferences, of four common tree species (Betula platyphylla, Larix sibirica, Picea obovata, and Pinus sibirica). Regeneration patterns differed among B. platyphylla, L. sibirica, and the two evergreen conifers. B. platyphylla regenerated vigorously only after fire irrespective of the presence/absence of nearby seed sources, whereas post-fire regeneration of L. sibirica was more dependent on the presence of nearby seed sources. These two species did not regenerate in mature stands where mature trees of these species were growing. In contrast, no post-fire recruitment of P. obovata and P. sibirica was observed, whereas continuous recruitment of these species was observed in mature stands. The frequent fires that accompany illegal logging may result in larger burned areas and increase the risk of local extinctions of seed sources. The enlargement of burned areas is likely to favor post-fire recruitment of B. platyphylla. Seed dispersal limitation seems to have less effect on B. platyphylla than on the other species because of the wider seed dispersal range and vegetative reproduction capability of this species. Consequently, fires in the northern Mongolian boreal forest likely promote the relative dominance of B. platyphylla and threaten the existence of the evergreen conifers.     

Complete nucleotide sequence and latency of a novel blueberry-infecting closterovirus

A novel latent closterovirus was detected from highbush blueberry in Japan and provisionally named blueberry virus A (BVA). The BVA genome (17,798 nucleotides) contains 10 open reading frames, but no minor coat protein could be identified in the virus genome. The BVA RNA-dependent RNA polymerase (RdRp), heat shock protein 70 homolog (HSP70h), and major coat protein (CP) shared the highest amino acid sequence identities with those of viruses in the genus Closterovirus (61.2, 27.6, and 20.9 %, respectively). In a phylogenetic analysis of the RdRp, HSP70h, and CP, BVA did not cluster with any genus in the family Closteroviridae.     

Suppression of mRNAs for lipoxygenase (LOX), allene oxide synthase (AOS), allene oxide cyclase (AOC) and 12-oxo-phytodienoic acid reductase (OPR) in pea reduces sensitivity to the phytotoxin coronatine and disease development by Mycosphaerella pinodes

Using a recently developed model pathosystem involving Medicago truncatula and Mycosphaerella pinodes, causal agent of Mycosphaerella blight on pea to understand host molecular response to a fungal suppressor, we applied the suppressor to leaves of M. truncatula and identified 151 nonredundant cDNA fragments as newly expressed genes. These included genes encoding lipoxygenase (LOX) and enoyl-CoA hydratase, which are presumably involved in jasmonic acid (JA) synthesis. Potential genes encoding plastidic enzymes, including allene oxide synthase (AOS) and allene oxide cyclase (AOC), and other peroxisomal enzymes involved in β-oxidation were predicted from the Medicago Gene Index EST database and tested for altered expression by semiquantitative RT-PCR. The coordinated expression of genes encoding both plastidic and peroxisomal enzymes showed that the suppressor likely conditions certain cellular process(es) through the JA synthesis in M. truncatula. To explore the role of JA or JA-regulated cellular process(es) in conditioning susceptibility, we used an Apple latent spherical virus (ALSV)-based virus-induced gene silencing (VIGS) technology to silence pea genes including LOX, AOS, AOC and 12-oxo-phytodienoic acid reductase (OPR). In LOX-, AOS-, AOC- or OPR-silenced pea plants, disease development induced by M. pinodes was remarkably reduced. Similarly, silencing of mRNA for LOX, AOS, AOC or OPR reduced the sensitivity to a phytotoxin, coronatine, which is believed to act through a JA-dependent process. On the basis of these results, it is conceivable that M. pinodes has evolved a strategy to condition susceptibility by manipulating the physiology of host cells, in particular JA-regulated cellular process(es), to promote disease development in pea.     

Single fallout particles and zirconium-95 from the Chinese nuclear explosion of 9 May 1966

Daily fluctuations of the number of single fallout particles and activity of zirconium-95 in the groundlevel air were measured at Fayetteville (94 degrees W, 36 degrees N), Arkansas, for a period of about 3 months after the Chinese nuclear explosion of 9 May 1966. We found a cyclic pattern of variations for both zirconium-95 and fallout particles; this indicated that they were airborne for a long period and traveled far. Apparently, some of the particles circled the world more than once.     

Isolation and inhibitory effect of anti-<Emphasis Type="Italic">Vibrio</Emphasis> substances from <Emphasis Type="Italic">Pseudoalteromonas</Emphasis> sp. A1-J11 isolated from the coastal sea water of Kagoshima Bay

ABSTRACT:   Among several marine antagonistic bacteria isolated from the sea water of Kagoshima Bay, Pseudoalteromonas sp. A1-J11 was found to produce anti- Vibrio substances. The anti- Vibrio substances were extracted from the culture supernatant of the strain with chloroform and isolated using reverse-phase (Cosmosil 75C₁₈-OPN) column chromatography followed by high-pressure liquid chromatography (Mightysil RP-18 GP Aqua). Purified substances, designated as AVS-03 a , c and d showed similar ultraviolet absorption spectra with λ_max at 215, 235, 315 and 327 nm in methanol. AVS-03 d , the major anti- Vibrio substance, was thermostable up to 100°C and pH stable over a pH range higher than 4.0, and also showed strong inhibitory activities, specifically against Vibrio harveyi strains.     

Bacterial community composition shifts in sediments influenced by fish feeds

This study investigated the influence of fish feed deposition on the microbial community of sediments in a coastal lake. Microcosms were designed to simulate the addition of fish feeds to the sediment, and physicochemical factors as well as composition of microbial assemblages were analysed. Although total organic carbon and total organic nitrogen did not significantly increase, redox potential and total sulphides showed a transition of sediment environments into anaerobic condition due to the addition of fish feeds. The bacterial community composition shifted with fish feed deposition as revealed by the band profiles of denaturing gradient gel electrophoresis, Sørensen's similarity indices and cell numbers of sulphate‐reducing bacteria. Occurrence of anaerobic bacteria (sulphate and nitrate reducers) and disappearance of strictly aerobic bacteria were observed with fish feed inputs. The results clarify the succession of the microbial flora and suggest negative impact of uneaten fish feeds on the microbial community in sediment and resultant environmental deterioration of fish‐farming areas.     

毛乌素沙地凝结水动态变化及其影响因子的研究

基于2002年5~10月间运用直接称重法对毛乌素沙地臭柏(Sabina vulgaris Ant.)群落林间空地的0-1.5cm表层土壤凝结水连续观测资料,分析讨论了凝结水的日变化和季节变化特征以及影响凝结水形成的环境因子。结果表明:毛乌素沙地天然臭柏群落内各月均有凝结水发生,并且可从午后持续至翌日清晨,但各月间凝结水量和凝结持续时间有所不同。5月份凝结水持续时间最短,凝结水量也最少;而9月份凝结水持续时间最长,凝结水量也最多。影响毛乌素沙地凝结水形成的主要环境因子有风速、大气相对湿度、气-地温差及其相互作用。其中,风速与凝结量间存在较高相关性,而气温能否趋近或降至露点产生土壤凝结水是决定夜间水分凝结量的一个关键因素。