The abundance,distribution and structural characteristics of tree‐holes in Nothofagus forest,New Zealand

Tree‐holes provide an important microhabitat that is used for feeding, roosting and breeding by numerous species around the world. Yet despite their ecological importance for many of New Zealand's endangered species, few studies have investigated the abundance or distribution of tree‐holes in native forests. We used complementary ground and climbed tree surveys to determine the abundance, distribution and characteristics of tree‐holes in undisturbed Nothofagus forest in the Lewis Pass, New Zealand. We found that hole‐bearing trees were surprisingly abundant compared with many other studies, including Australian Eucalyptus species and American beech. In fact, we estimated as many as 3906 tree‐holes per hectare, of which 963 holes per hectare were potentially large enough to provide roost sites for hole‐nesting bats in New Zealand, while only eight holes per hectare were potentially suitable for specialist hole‐nesting birds. This was of great interest as primary cavity‐excavating animals are absent from New Zealand forests, compared with North America and Australia. Moreover, tree‐hole formation in New Zealand is likely to be dominated by abiotic processes, such as branch breakage from windstorms and snow damage. As has been found in many other studies, tree‐holes were not uniformly distributed throughout the forest. Tree‐holes were significantly more abundant on the least abundant tree species, Nothofagus fusca, than on either N. menziesii or N. solandri. In addition to tree species, tree size was also an important factor influencing the structural characteristics of tree‐holes and their abundance in this forest. Moreover, these trends were not fully evident without climbed tree surveys. Our results revealed that ground‐based surveys consistently underestimated the number of tree‐holes present on Nothofagus trees, and illustrate the importance of using climbed inspections where possible in tree‐hole surveys. We compare our results with other studies overseas and discuss how these are linked to the biotic and abiotic processes involved in tree‐hole formation. We consider the potential implications of our findings for New Zealand's hole‐dwelling fauna and how stand dynamics and past and future forest management practices will influence the structural characteristics of tree‐holes and their abundance in remnant forest throughout New Zealand.     

Is biofuel policy harming biodiversity in Europe?

We assessed the potential impacts of land-use changes resulting from a change in the current biofuel policy on biodiversity in Europe. We evaluated the possible impact of both arable and woody biofuel crops on changes in distribution of 313 species pertaining to different taxonomic groups. Using species-specific information on habitat suitability as well as land use simulations for three different biofuel policy options, we downscaled available species distribution data from the original resolution of 50 to 1 km. The downscaled maps were then applied to analyse potential changes in habitat size and species composition at different spatial levels. Our results indicate that more species might suffer from habitat losses rather than benefit from a doubled biofuel target, while abolishing the biofuel target would mainly have positive effects. However, the possible impacts vary spatially and depend on the biofuel crop choice, with woody crops being less detrimental than arable crops. Our results give an indication for policy and decision makers of what might happen to biodiversity under a changed biofuel policy in the European Union. The presented approach is considered to be innovative as to date no comparable policy impact assessment has been applied to such a large set of key species at the European scale.     

The influence of leaf litter on zooplankton in floodplain wetlands: changes resulting from river regulation

1. The loss of input of leaf litter through clearing of riparian vegetation may result in significant changes to aquatic ecosystems. River red gums (Eucalyptus camaldulensis) surrounding floodplain wetlands in the Murray–Darling Basin, Australia, contribute large quantities of leaf litter, but the quality of this resource may change depending on the timing of inundation. 2. We used experimental mesocosms to test the hypotheses that zooplankton would have a greater abundance with an input of leaf litter and that fewer zooplankton would emerge from egg banks in cleared than forested wetlands. The experiment was carried out in summer/autumn and in spring to test a third hypothesis that zooplankton would respond to changes in the timing of wetland inundation as a result of river regulation. 3. In summer/autumn, leaf litter reduced zooplankton abundance by 89% at the beginning of the experiment through its influence on water quality. Only a few taxa (Polyarthra spp., Colurella spp. and the cladoceran Family Moinidae) responded positively to leaf litter when water quality improved later in the experiment, indicating a switch in the role of leaf litter from a non‐trophic to a trophic pathway. 4. In spring, microcrustaceans emerged in smaller numbers from sediment sourced from cleared compared to forested wetlands, reflecting different communities in these two wetland types and/or disturbances to the sediment that interfere with emergence. 5. Although leaf litter appears not to be an important resource for zooplankton in floodplain wetlands, riparian clearing may have lasting effects on future emerging zooplankton communities. Additionally, river regulation may have considerable impacts on the influence of leaf litter on zooplankton, which has implications for the management of floodplain river systems.     

四步法消除SYBR GreenⅠ实时定量RT-PCR中引物二聚体的影响

为建立一种新的SYBRgreenⅠ实时定量RT PCR方法 ,使之能够有效消除引物二聚体 (PDs)对实时定量结果的影响 .对RT PCR特异性扩增产物和PDs分别进行了凝胶电泳检测和熔解曲线分析 .依据PDs和扩增产物的熔解温度 (Tm)特点 ,在通用的三步法的延伸步骤之后 ,增加一个短暂的 (5s)恒温和荧光检测步骤 ,使这个步骤的温度高于PDs的Tm,但低于扩增产物的Tm,简称该法为四步法 .PDs的Tm 通常高于 72℃ ,但低于扩增产物的Tm .将四步法第四步的温度设置在高于PDs的Tm ,但低于扩增产物的Tm 时 ,四步法能够有效地消除PDs的影响 .对三步法和四步法SYBRgreenⅠ实时定量RT PCR进行了比较 ,发现三步法根本不能用于RNA的实时定量 ,而四步法能够实现包括低丰度RNA在内的RNA的定量 .选择Tm 值尽可能小的引物 ,使PDs与扩增产物Tm 值之间有足够的差距 ,将更有利于四步法的应用 ,并可成功地用于低丰度RNA的准确定量     

Error in the inference of fire history from grasstrees

Abstract A method for constructing fire histories has recently been proposed for fire‐prone southern Australia based on the pattern of coloured bands in the remnant leaf‐bases on stems of grasstrees (Xanthorrhoea species; Xanthorrhoeaceae). In the absence of alternative high‐resolution techniques extending into the premodern period, this method has been utilized to construct fire histories for forest, woodland and shrubland ecosystems, principally in south‐western Australia. However, the technique has not been validated against known fire histories spanning more than one fire interval. Here we compare fire records from 100 grasstrees with a 30‐year record (1973–2002) of fire data derived from satellite imagery in a region of sandplain shrubland vegetation near Eneabba in south‐western Australia. Fires occurred in eight of the 30 years of the satellite record, with sampled grasstrees burning between zero and four times. The grasstree and satellite records agreed in terms of the overall incidence of fires experienced over the 30‐year period, with the grasstree record matching the satellite record significantly better than chance. However, comparison of the grasstree and satellite records found substantial error in the rate of both false positives and false negatives. Grasstrees failed to identify fire in 83% of fire occurrences identified by the satellite record, down to 53% if an error of ±2 years in the attribution of year of fire was allowed. A similar proportion of grasstree fire incidents were not matched in the satellite record (false positives). The rate of false positives increased with time before present, suggesting a temporal bias in the grasstree record. It is clear that the grasstree record does reflect fire history to a degree, but that it contains at least as many false as true fire records and may tend towards over‐reporting the incidence of fire in the past.     

Influence of Age of Culture and Light Intensity on Solute Concentrations in Two Dunaliella Strains

Two strains of Dunaliella, one halotolerant and one halophilic,were grown in batch culture at NaCl concentrations varying from500 mol m^–3 to 3000 mol m^–3. Measurements were madeof the following solutes: glycerol, Na⁺, K⁺, Mg²⁺, Cl^–,phosphate in the cells of logarithmic and of stationary-phasecultures. The method used was to separate the cells from thebulk of the medium by differential density centrifugation. Soluteconcentrations were calculated using Blue Dextran as a markerfor extracellular space. It was found that in log-phase cells,glycerol accounted for one-half to two-thirds of the total cellsolute concentration, the remainder being largely accountedfor by Na⁺ and Cl^–. In the stationary phase glycerol felland Na⁺, plus Cl^–, rose. Light intensity was found toaffect cell volume and solute content. The means whereby soluteconcentrations are controlled is discussed. Key words: Osmoregulation, Ion concentrations, Dunaliella     

Ion and Glycerol Concentrations in 12 Isolates of Dunaliella

Ginzburg, M., and Ginzburg, B. Z., 1985. Ion and glycerol concentrationsin 12 isolates of Dunaliella.—J. exp. Bot. 36: 1064–1074. Twelve isolates of Dunaliella with average cell volumes rangingfrom 50 to 1400x10^–18 m³ were grown in batch culture at0.5 M or 2.0 M NaCl. Glycerol and ions (Na⁺, K⁺, Mg²⁺, CI^–,phosphate) were measured in log-phase cultures. The contentsof Mg²⁺, K⁺ and phosphate per cell were found to be a functionof cell-volume. Cell glycerol, Na⁺ and Cl^– were functionsof cell-volume and of the NaCl concentration in the medium.Solute concentrations were calculated from the measured cell-volumesand from the ³H₂O content of pellets corrected for intercellularspace using Blue Dextran. Cell glycerol was found to accountfor about one-half of the expected osmolarity, the remainderbeing largely accounted for by Na⁺ and CI^–. Key words: —Dunaliella, isolates, glycerol, ion concentrations     

Stramenopile Microorganisms Associated with the Massive Coral Favia sp.

ABSTRACT. The surfaces of massive corals of the genus Favia from Eilat, Red Sea, and from Heron Island, Great Barrier Reef, are covered by a layer of eukaryotic microorganisms. These microorganisms are embedded in the coral mucus and tissue. In the Gulf of Eilat, the prevalence of corals covered by patches of eukaryotic microorganisms was positively correlated with a decrease in water temperatures (from 25–28 °C in the summer to 20–23 °C in winter). Comparisons carried out using transmission and scanning electron microscopy showed morphological similarities between the microorganisms from the two geographically distant reefs. The microorganisms found on and in the tissues were approximately 5–15 μm in diameter, surrounded by scales in their cell wall, contained a nucleus, and included unique auto‐florescent coccoid bodies of approximately 1 μm. Such morphological characters suggested that these microorganisms are stramenopile protists and in particular thraustochytrids. Molecular analysis, carried out using specific primers for stramenopile 18S rRNA genes, revealed that 90% (111/123) of the clones in the gene libraries were from the Thraustochytriidae. The dominant genera in this family were Aplanochytrium sp., Thraustochytrium sp., and Labyrinthuloides sp. Ten stramenopile strains were isolated and cultured from the corals. Some strains showed ≥97% similarity to clones derived from libraries of mucus‐associated microorganisms retrieved directly from these corals. Fatty acid characterization of one of the prevalent strains revealed a high percentage of polyunsaturated fatty acids, including omega‐3. The possible association of these stramenopiles in the coral holobiont appeared to be a positive one.