Somatic mutagenesis of the moss, Physcomitrella patens

Summary Spores have been preferred for mutagenic treatment of Physcomitrella patens. Many mutant strains are, however, sexually sterile and so do not produce spores. We report here a method of somatic mutagenesis, followed by protoplast isolation, which allows a second round of mutagenesis in these mutants. This method is also a convenient technique for routine isolation of mutants in wild-type P. patens.     

Spatial distribution of epiphytes on Populus tremula in relation to dispersal mode

Abstract. We examined if the spatial distribution of epiphytes in a forest stand differs between two sexually and three asexually dispersed species. As study species we have chosen two sexually dispersed species, the lichen Collema curtisporum and the bryophyte Orthotrichum speciosum, and three asexually dispersed species, the lichens C. furfuraceum and Leptogium saturninum and the bryophyte O. obtusifolium. All of these species grow on Populus tremula. In P. tremula stands, individual trees may be regarded as distinct patches for the studied species, while the stand represents a “landscape” of discrete patches. The study was performed in two relatively homogeneous forest stands. The study revealed that the asexually dispersed species were more common than the sexually dispersed. It was also shown that the sexually dispersed species were more aggregated than P. tremula in both stands. In contrast, the distribution of the asexually dispersed species mirrors, more or less, the distribution of their host, i.e. the spatial pattern shown by P. tremula. It is unlikely that the measured environmental variables strongly influenced the observed spatial distribution. Thus, we suggest that the different dispersal and establishment strategies were important in shaping the local distribution of the species.     

苔藓植物生态功能的研究进展

苔藓植物虽然个体较小,但种类很多,约有23000多种,是生物多样性的重要组成部分．过去的研究多集中在分类和区系方面,其在生态系统中的作用,即生态功能,一直没有引起足够的认识．苔藓植物对环境有较强的适应能力,在多种极端环境下都有分布,同时对土壤有一定的改造能力．苔藓植物有很强的吸水、保水能力,尤其是树附生苔藓植物能够吸收很大部分的降水,其水文作用相当明显．苔藓植物通过体表吸收了大量的养分元素,以往常常忽略其在养分循环中的作用．在一些极端环境中苔藓植物是重要的初级生产者,泥炭藓的生物量更是相当巨大,可能是重要的C汇．苔藓植物对大气及重金属污染反应非常明显。可以作为良好的生物指示剂．本文综述了苔藓植物生态功能的研究进展,以期促进更加广泛地开展苔藓植物生态功能的研究．     

How bryophytes came out of the cold: successful cryopreservation of threatened species

The use of ex situ techniques for the conservation of threatened plants has been increasing over the past decades. Cryopreservation is often used for the long-term storage of plant germplasm where conventional methods (i.e. seedbanking) are inappropriate. Simple encapsulation–dehydration protocols were developed for the cryopreservation of bryophytes at The Royal Botanic Gardens, Kew, as part of an ex situ project for the conservation of UK threatened species. The applicability of these methods was tested on 22 species with a broad range of ecological requirements and found to be highly successful across the board. Regeneration rates from frozen material were >68% for all species tested and half had regeneration rates of 100%. The high regeneration rate and broad applicability of the protocols across a range of species was attributed to a combination of the inherent totipotency of bryophytes and the in-built recovery periods in the pre-treatment protocol. In conclusion, bryophytes are well suited to cryopreservation and such techniques would be applicable for the long-term storage of similar conservation collections across the globe.     

Are nutrient availability and acidity‐alkalinity gradients related in Sphagnum‐dominated peatlands?

Abstract. Gradients in acidity‐alkalinity and nutrient availability were studied in 2 Sphagnum‐dominated peatlands on the southeastern Italian Alps. Decreasing concentrations of most mineral elements (Ca²⁺, Mg²⁺, Mn²⁺, Al³⁺ and Si⁴⁺) in pore water indicated a progressively lower influx of mineral‐soil water from the slightly minerotrophic conditions in the peatland margins to ombrogenous conditions in the central part of the peatlands. This was paralleled by decreasing concentrations of ash, bulk density, Ca, Fe and, partly, Mn in the peat. The nutrient gradient, as defined by pore water concentrations of N and P, was largely independent of the acidity‐ alkalinity gradient: NO^3‐ and PO₄^3‐ had similar concentrations throughout the gradient, whereas NH₄⁺ concentrations increased with increasing pore‐water pH. In contrast, the peat nutrient gradient coincided with the acidity‐alkalinity gradient, with total concentrations of N and P decreasing from the margin to the centre. Bryophytes and vascular plants had different responses along the acidity‐alkalinity gradient and the nutrient gradient. Bryophyte distribution reflected the acidity‐alkalinity gradient both in pore water and in peat. Vascular plant distribution was mainly influenced by variations in nutrient availability.     

Predictability of plant and fungal species richness of old‐growth boreal forest islands

Abstract. The fragmentation and deterioration of old‐growth forest habitat by modern forestry have become a major threat to species diversity in Fennoscandia. In order to develop a conservation strategy for the remaining diversity it is essential to identify the existing diversity and to develop appropriate conservation and monitoring programs. For these purposes indicators of conservation value for administrative prioritization are required. This study examines the predictability of plant and fungal species richness on two spatial scales on 46 isolated old‐growth forest islands (0.17 ‐ 12 ha) in a forest‐wetland mosaic. We explore (1) to what extent area, isolation and stand structure variables can explain the variation in species richness and (2) if richness patterns of individual species groups correlate. Isolation showed no relation to species richness. Area explained 50 ‐ 70% of the variation in total species richness and was positively related to the density of crustose lichens and Red‐list species in island interiors. Stand structure variables explained 28 ‐ 66% of the residual variation in total species richness after controlling for island size, and 15 ‐ 73% of the variation in density of species in island interiors. The highest predictability of species richness was found among substrate‐specific fungi and Red‐list species. Different stand structure variables were found to explain richness in the different species groups, and only among a few species groups species richness correlated. Thus, species richness of one single species group is unlikely to be a good indicator for total biodiversity. The results show that measurements of stand size and stand structure variables may be a strong complementary tool, and sometimes a substitute to extensive species inventories when one aims to estimate and monitor plant and fungal species diversity in old‐growth Picea abies forests.     

Sex expression and sex dimorphism in sporophytic populations of the desert moss Syntrichia caninervis

Ten sporophytic populations of Syntrichiacaninervis contained an average of 22 individualscm^–2, with a sex ratio of 7.9 Female:1 Male: 3.1 Nonexpressing(N = 300). In each of the populations, female individuals outnumberedmale individuals. A representative population size of 50 × 25cm was estimated to contain 27,250 organically distinct individualplants. Given the wide disparity in reproductive investment in this dioeciousspecies, sex-specific traits were investigated at the level of the individualinbiomass, total stem length, number of ramets, number of branches, length ofannual growth interval, length of longest ramet, age, number of inflorescences,number of ramets expressing sex, and consecutive seasons of sex expression. Theonly significant sex dimorphism recorded was in consecutive seasons of sexexpression, with nonsporophytic female individuals exhibiting a higherfrequencythan males. However, nonexpressing individuals had lower biomass, shorter totalstem length, fewer branches, and shorter ramets than males and females, andfewer ramets than female individuals. When the biomass of female and maleindividuals was controlled for inflorescence number, no significant differencesbetween the sexes in biomass were found. There appears to be a threshold sizefor sex expression, with all individuals above 2.0 mg dry weightexpressing sex (N = 108). Biomass and total stem length are strongpositive correlates (r = 0.88), and individual biomass is a betterpredictor of the number of inflorescences produced per individual than is stemlength (r = 0.85 vs. r = 0.69, respectively). Independent of stemlength, individual biomass had a positive and significant relationship withinflorescence number; however, independent of individual biomass, stem lengthwas not associated with inflorescence number. Overall sex expression was 0.74(individual level) and 0.65 (ramet level). The functional sex ratio wasassessedat the inflorescence level, and ranged from 9.7:1, to14.9:1 over the most recent four years. Fertilization frequencywas 0.69 (individual level) and 0.34 (perichaetial level). Over the last threeyears, 63% of all fertilized perichaetia resulted in an abortivesporophyte.     

Cryptogam communities on fallen logs in the Duke Forest,North Carolina

Abstract. I studied cryptogam (i.e. bryophyte and lichen) communities on fallen logs in the Duke Forest, Durham and Orange Counties, North Carolina, USA, to determine the relationship of log characteristics and microsite to community composition. Species composition and abundance were estimated for 111 randomly selected fallen logs. Interior wood samples were used to identify the tree species. I determined physical and chemical characteristics for each log, and described the log microsite. Canonical Correspondence Analysis (CCA) detected a clear gradient in cryptogam species composition which is correlated with the species of log and the presence of bark. Communities on hardwood bark, hardwood wood, and pine substrates were the most distinct. CCA also revealed that the microsite is not as closely related to species composition as are substrate pH and density. The majority of the cryptogam species encountered on the fallen logs are commonly reported from other substrates in the forest. However, within the habitat type of fallen logs, several species were apparently restricted to certain substrate types.     

北京东灵山苔藓植物区系研究

在野外调查和采集标本的基础上,对北京东灵山苔藓植物区系成分及特点进行研究。结果显示,该地区共有苔藓植物27科64属150种(含2变种),其中32种为北京苔藓植物新记录。优势科为青藓科(Brachytheciaceae)、丛藓科(Pottiaceae)、灰藓科(Hypnaceae)、真藓科(Bryaceae)和绢藓科(Entodontaceae)5科;优势属为青藓属(Brachythecium)、绢藓属(Entodon)、紫萼藓属(Grimmia)、真藓属(Bryum)、金灰藓属(Pylaisia)、凤尾藓属(Fissidens)、美喙藓属(Eurhynchium)和毛口藓属(Trichostomum)8属。区系分析表明,东灵山苔藓植物区系地理成分以北温带成分为主(占36.7%)、东亚成分次之(占18.0%)。通过与我国15个地区苔藓植物区系谱主成分分析发现,东灵山苔藓植物区系成分与雾灵山、小五台山与贺兰山相近,与云蒙山最为接近。     

Higher acidification rates in fens with phosphorus enrichment

Question: Why is bryophyte succession in eutrophicated fens faster than in natural fens? Location: Mineral‐rich fens in The Netherlands and NW Europe. Methods: Literature review on the ecology of four bryophyte species in various successional types as observed in Dutch fens. Results: Bryophyte succession in eutrophicated fens from the brown moss Calliergonella cuspidata to Sphagnum squarrosum is much faster than in natural fens with species shifts from Scorpidium scorpioides to Sphagnum subnitens. Under P‐poor conditions, the brown moss stage is stabilized as long as mineral‐rich water is supplied. This is because S. scorpioides is tolerant of rainwater, is a strong competitor and can counteract acidification to some extent while S. subnitens is intolerant to groundwater and has low growth rates and low acidification capacity. In contrast, the Sphagnum stage is stable after rapid succession from rich‐fen mosses under P‐rich conditions. Calliergonella cuspidata has suboptimal growth in rainwater, possibly due to ammonium toxicity, while the high growth rates of S. squarrosum in nutrient‐rich and highly acidic groundwater allow early establishment and rapid expansion. Conclusions: If measures to improve fen base status occur in environments of increased nutrient (P) availability, the management may not lead to the desired restoration of brown moss stages, but instead to rapid acidification by S. squarrosum.