Response of the moss Racomitrium lanuginosum to changes in sheep grazing and snow‐lie due to a snow‐fence

Question: What are the responses of Racomitrium lanuginosum moss to altered snow‐lie and sheep use? Location: ACarexbigelowii‐Racomitrium lanuginosum heath on a Scottish montane plateau affected since 1986 by a fenced ski corridor. Methods: Permanent quadrats were set up along transects 45 m long perpendicular to the snow‐fence. Cover was assessed over a 12‐year period from 1990. Pellet‐group clearance counts provided data on sheep usage between 1990 and 1996. Snow‐lie was mapped in the springs of 1991–1996. Results: The snow‐fence created a gradient in sheep use and altered the duration of snow‐lie. At the start of monitoring Racomitrium cover was lower immediately adjacent to the fence, and after 12 years its cover was significantly reduced within 10 m of the fence. Further away from the fence Racomitrium cover was relatively stable. The loss of Racomitrium was correlated both with increased snow‐lie and heavier sheep usage. Grass cover increased near the fence and was related to sheep use. Dicranum fuscescens responded differently to Racomitrium, increasing significantly near the fence. Conclusions: We found that changes in snow‐lie and grazing pressure quickly brought about vegetation change in this montane ecosystem. Racomitrium was the most sensitive species to the changes in grazing and snow‐lie caused by the fence, having the biggest initial changes. Loss of Racomitrium permitted increases of species more resistant to grazing including Dicranum fuscescens and grasses.     

Characterization of diverse plant communities in Aspen Parkland rangeland using LiDAR data

Question: How effective is high-resolution airborne LiDAR technology for quantifying biophysical characteristics of multiple community types within diverse rangeland environments? Location: Native Aspen Parkland vegetation in central Alberta, Canada. Methods: Vegetation within 117 reference plots stratified across eight types, including forest, shrubland, upland grassland and lowland meadow communities, were assessed in 2001 for the height, cover and density of vegetation within various strata (herb, shrub and tree layers). Actual ground data were subsequently compared against modelled values for each community type and strata derived from the analysis of airborne LiDAR data obtained in 2000. Results: LiDAR data were effective for quantifying vegetation height, cover and density of the overstory within closed- and open Populus forest communities. However, LiDAR measurements typically underestimated the height and cover of shrublands, as well as most of the herbaceous communities. Analysis of LiDAR intensity data indicated reflectance generally decreased as LiDAR sampling points moved upwards from the ground to the vegetation canopy. Conclusions: While LiDAR technology is useful for characterizing deciduous forest properties, the quantification of understory vegetation characteristics, as well as those of individual shrublands and grasslands, was more limiting. Further refinements in analysis methods are necessary to increase the reliability of characterizing these communities.     

黄山藓类植物区系

对黄山进行了多次实地调查、考察和标本采集,经分类鉴定,收集整理有关黄山藓类的研究资料,目前黄山藓类植物有46科、135属、401种（包括7亚种和22变种）,与20世纪50年代陈邦杰等以及后来对黄山的调查研究结果相比,藓类植物增加了4科、28属、184种;科内种数（≥15种）优势科有10个,属内种数（≥6种）的优势属有18个。黄山藓类植物地理成分类型复杂,东亚成分（包括中国特有）占37.82%,温带成分占35.13%,热带、亚热带成分占26.75%,表现出明显的由亚热带向温带过渡的特性。     

泰国和越南藓类新纪录

报道了越南藓类的２个新记录,即：海南花锦藓Ｃｈｉｏｎｏｓｔｏｍｕｍ ｈａｉｎａｎｅｎｓｉｓ Ｔａｎ ＆Ｊｉａ和毛齿匍灯藓Ｐｌａｇｉｏｍｎｉｕｍ ｔｅｚｕｋａｅ Ｔ．Ｋｏｐ．;泰国藓类的３个新纪录,即：糙叶梨果藓Ｍａｓｔｏｐｏｍａ ｓｃａｂ＃颍椋妫铮欤椋酰? Ｔａｎ ＆ Ｔ．Ｎｉｎｈ,毛尖狗尾藓Ｒｈａｐｉｄｏｓｔｉｃｈｕｍ ｐｉｌｉｆｅｒｕｍ Ｂｒｏｔｈ。,细枝羽藓Ｔｈｕｉｄｉｕｍ ｄｅｌｉｃａｔｕ     

Involvement of cyclic adenosine-3′, 5′-monophosphate in chloronema differentiation in protonema cultures of Funaria hygrometrica

The role of purine and pyrimidine ribosides, nucleotides and substituted xanthines in the differentiation of chloronema filaments in suspension cultures of protonema of the moss Funaria hygrometrica Hedw. has been examined. Cyclic adenosine-3,5-monophosphate (cAMP) and mono-and dibutyryl cAMP evoked the maximum response in wild-type protonema. ADP and ATP also enhanced chloronema differentiation but were less active than cAMP; pyrimidine derivatives were completely inactive. Inhibitors of cyclic-nucleotide phosphodiesterase aminophylline, theophylline and ICI 58, 301 (3-acetamido-6-methyl-8-n-propyl-s-triazolo-(4,3a)-pyrazine)-mimicked the effect of cAMP. A leaky, chloronema-repressed mutant was isolated and in this mutant cAMP was much more active than cyclic guanosine monophosphate and ADP in enhancing chloronema differentiation. These results strongly indicate that cAMP is involved in chloronema differentiation in Funaria, and a hypothesis on growth regulation in protonema cell cultures is proposed.Abbreviations cAMP, cyclic AMP cyclic adenosine-3, 5-monophosphate - cCMP, cGMP, cIMP cyclic cytosine-, guanosine-and inosine-3, 5-monophosphates, respectively - IAA indole-3-acetic acid - ICI 58,301 3-acetamido-6-methyl-8-n-propyl-s-triazolo-(4,3a)-pyrazine     

Purification and identification of a cytokinin from moss callus cells

A cytokinin was isolated from the culture medium of callus cells of the moss hybridFunaria hygrometrica (L.) Sibth xPhyscomitrium piriforme Brid. The purification procedure included ethyl-acetate extraction, silver-salt precipitation, crystallization as picrate, and ion exchange chromatography. The structure of the cytokinin was confirmed as N⁶–(²-isopentenyl)adenine by means of gas chromatography and mass spectrometry. The concentration of the compound in the culture medium was determined at ca. 10^-6 M.Abbreviation 2iP N⁶–(²-isopentenyl) adenine     

CO2 environment,microclimate and photosynthetic characteristics of the moss Hylocomium splendens in a subarctic habitat

Summary In order to document the natural CO₂ environment of the moss Hylocomium splendens, and ascertain whether or not the moss was adapted to this, and its interactions with other microenvironmental factors, two studies were carried out. Firstly, the seasonal variations of CO₂ concentration, photosynthetically active radiation (PAR), tissue water content and temperature were measured in the natural microenvironment of H. splendens in a subarctic forest during the summer period (July–September). Secondly, the photosynthetic responses of the species to controlled CO₂ concentrations, PAR, temperature, and hydration were measured in the laboratory. CO₂ concentrations around the upper parts of the plant, when PAR was above the compensation point (30 mol m^–2 s^–1), were mostly between 400 and 450 ppm. They occasionally increased up to 1143 ppm for short periods. PAR flux densities below saturating light levels for photosynthesis (100 mol m^–2 s^–1), occurred during 65% (July), 76% (August) and 96% (September) of the hours of the summer period. The temperature optimum of photosynthesis was 20° C: this temperature coincided with PAR above the compensation point during 5%, 6% and 0% of the time in July, August and September, respectively. Optimal hydration of tissues was infrequent. Hence PAR, temperature and water limit CO₂ uptake for most of the growing season. Our data suggest that the higher than normal ambient CO₂ concentration in the immediate environment of the plant counteracts some of the limitations in PAR supply that it experiences in its habitat. This species already experiences concentrations of atmospheric CO₂ predicted to occur over the next 50 years.     

Moss Communities and Their Characteristics in Ice-free Areas of the Windmill Islands,Wilkes Land,Continental Antarctica

The moss vegetation of the Windmill Islands can be classified into the following seven communities: 1.Grimmia antarctici community; 2. G. antarctici-Ceratodon purpureus community; 3. Bryum pseudotriquetrum community; 4. G. antarctici-B, pseudotriquetrum community; 5. Ceratodon purpureus community; 6. C. purpureus-G, antarctici community; 7. C. purpureus B. pseudotriquetrum community. Communities 1, 3, 4 and 7 occur in wet habitats while communities 5 and 6 are found in rather dry habitats, community 2 distributes between dry and wet habitats. Microtopography governs the distribution of water supply and therefore community types. Stable moss communities usually form moss hummocks and hollows. Species composition, colour and height of the hummocks determines the vertical structure of the moss community layers with 2-3 strata being discernible and level structure forming mosaic. Other phytocoenological characteristics of the moss communities, such as the dense moss cushions, asexual reproduction (although antheridia or archegonia have been found in each of the species), abundance of epiphytic algae and lichens growing on the surface of moss hummocks, the colour change of some species in different habitats, appear related to moisture availability, light intensity, wind exposure and temperature.