Oviposition choice and larval performance of Neomusotima conspurcatalis on leaflet types of the invasive fern,Lygodium microphyllum

Lygodium microphyllum (Cavanilles) R Brown (Lygodiaceae), Old World climbing fern, invades wildlands in central and southern Florida, USA, and causes considerable habitat disturbance. Efforts to develop an effective biological control strategy have focused on several folivorous insects and a leaf‐galling mite from southeast Asia and Australia. Neomusotima conspurcatalis Warren (Lepidoptera: Crambidae) is a foliage‐feeding moth that specializes on Lygodium species. First released in 2008, N. conspurcatalis successfully established in Florida and is dispersing throughout the L. microphyllum‐invaded range. We investigated whether N. conspurcatalis display any preference (oviposition or larval feeding) between two leaflet morphologies, i.e., fertile spore‐producing vs. sterile leaflets. Furthermore, we examined whether oviposition and no‐choice diets on either fern leaflet type conferred any possible selective advantages (e.g., weight, emergence success) to the offspring. Finally, we analyzed leaf nitrogen and carbon content and leaf volatiles to gauge differences between the leaflet types. In choice and no‐choice scenarios, larvae consume approximately the same amount of leaf area and display no preference between fertile and sterile leaflets. However, females deposited significantly more eggs on fertile than on sterile leaflets. Oviposition choice had no effect on larval development times, pupal weights, or successful eclosure. Nitrogen and carbon content did not differ between fertile and sterile samples, but sterile leaflets contain more 1‐octen‐3‐ol, which may act as an herbivory deterrent. The propagule attack imposed by N. conspurcatalis feeding on fertile leaflets is unlikely to provide adequate control, but could be beneficial as part of a suite of biological control agents and other control methods.     

Reproductive phenology of the introduced kelp <Emphasis Type="Italic">Undaria pinnatifida</Emphasis> (Phaeophyceae,Laminariales) in Port Phillip Bay (Victoria,Australia)

A thorough understanding of the reproductive phenology of introduced species is crucial for effective management and control. Undaria pinnatifida is an invasive macroalga from the Northwest Pacific which has been recently introduced into three countries in the Southern Hemisphere: Australia, New Zealand and Argentina. Reproductive phenological studies in Port Phillip Bay, Australia, were undertaken and compared with other populations in the Southern Hemisphere, especially with those from Tasmania which were suspected to be very different. The growth season began earlier in Port Phillip Bay than in Tasmanian populations, and abundance was higher. Growth rates were lower in Port Phillip Bay, but this might be due to the different morphology of both populations. The maximum spore release competency of U. pinnatifida in Port Phillip Bay was 12.1 × 10⁵ spores cm⁻² h⁻¹ which is 20 times the maximum obtained in Tasmania (0.6 × 10⁵ spores cm⁻² h⁻¹). For most of the growth season, spore release competency ranged between 2 and 3 × 10⁵ spores cm⁻² h⁻¹, 3–5 times more than in Tasmania. Undaria pinnatifida has not been established outside Port Phillip Bay in continental Australia, but a precautionary approach should be undertaken in order to avoid further spread. Monitoring for early detection and removal of immature sporophytes prior to spore release seem to be the best options. This monitoring should be continuous since new recruits may appear throughout the growth season (April–February) and it should be combined with informative programmes to reduce the chances of spread.     

Fern spore and pollen airspora profile of Singapore

Monitoring atmospheric fern spore and pollen loads in Singapore was initiated in June 1990. Aside from the more numerous fungal spores, fern spores and pollen grains made up 6.2–8.6% and 4.4–5.4% of the total airspora sampled, respectively. The most frequently encountered fern spores, in descending order, were those of Nephrolepis auriculata, Dicranopteris linearis, Stenochlaena palustris, Asplenium nidus, Pteridium aquilinum, and Dicranopteris curranii. For pollen grains, the most frequently encountered, in descending order, were Elaeis guineensis, Casuarina equisetifolia, Acacia auriculiformis, Kyllingia polyphylla, Podocarpus, and Poaceae pollen grains. Seasonal patterns for individual fern spore or pollen types were discernible despite the relatively uniform tropical climate in Singapore. The fern spore and pollen calendar for the period 1991–1995 was compared to that of 2005–2006 as a follow-up study to keep abreast with the rapidly changing landscape of Singapore. Diurnal patterns showing a late morning to afternoon peak period were seen in fern spores, while the peak period was in the morning for pollen types studied with the exception to oil palm pollen. Additionally, association between fern spore and pollen counts and local meteorological conditions were also analyzed and found to be highly correlated. This study has thus identified the fern spores and pollen airspora components, and determined the calendars, as well as diurnal profiles of the Singapore airspora and provides invaluable information for allergy studies by highlighting the trigger sources present in the environment.     

Developmental Morphology of Platycerium coronarium (Koenig) Desv

The growth habit and certain developmental aspects of Platyceriumcoronarium (stag's horn fern) are described. Starting from theprimordial stage, the nest and pendulous leaves develop to maturityin 90 and 80 days respectively. The fertile lobe, which is partof the pendulous leaf, reaches its maximum size in 40 days.The morphogenesis of the nest leaf is more variable, and itmatures and deteriorates earlier than the pendulous leaf. Theacrostichoid sorus formation is completed in 3 weeks from inceptionand spore dispersal takes place when the fertile lobe is about100 days old. The area of the fertile lobe and number of sporesproduced were determined. On Knop's agar medium the gametophytesdevelop in 2 months and 85 per cent of them are unisexual (bothmale and female) and 15 per cent bisexual. Less than 1 per centof the gametophytes give rise to sporophytes. The juvenile leavesare simple, displaying open dichotomous venation; the firstnest and pendulous leaves are produced 24 months after the dateof spore germination. Platycerium coronarium, stag's horn fern, leaf development, morphogenesis, spore production     

Phenology of Dryopteris affinis ssp. affinis and Polystichum aculeatum: modeling relationships to the climatic variables in a Mediterranean area

The phenology of leaves and stages from immature sori to spore release were studied in natural populations of two perennial herbaceous ferns, Dryopteris affinis ssp. affinis and Polystichum aculeatum, for 2 years in Italy. The Generalized Additive Model for Location, Scale and Shape (GAMLSS) was used to predict a particular phenological event from the climatic variables. Both fern species are evergreen with leaf lifespan of 13–14 months in D. affinis ssp. affinis and 15–24 months in P. aculeatum. Their leaf production is seasonal with most flushed in spring. In D. affinis ssp. affinis the decaying of old leaves is sudden whereas in P. aculeatum it is gradual, and in both types the decaying is accelerated just as the new leaves emerge. Temperature is the best predictor for the development of sori and spore release. The end of spore release and leaf emergence are positively affected by temperature and negatively affected by rainfall and snow cover for P. aculeatum. An almost similar response to climatic factors of emergent and senescent leaves and their phenology supportsthe hypothesis that old leaves serve as nutrient storage organs for new leaf growth. Comparison the phenological patterns between the 2 years indicated that the time lapses between each phenological event were the same within seasons for D. affinis ssp. affinis but show some differences for P. aculeatum. We also hypothesize that endogenous factors may play an important role in the phenology of P. aculeatum.     

Seasonality of mycorrhizae in coastal sand dunes of Baja California

 Populations of arbuscular mycorrhizal fungi were estimated from spores associated with seven plant species in coastal dunes at El Socorro, near Ensenada, Baja California, during six months in 1992. The seasonal patterns of percent root colonization were also described in the same species during the wet season (January–March) and the dry season (April–July). Comparisons were made between the pioneer species (Abronia maritima) in the mobile dunes and six species (Abronia umbellata, Atriplex julacea, Camissonia californica, Haplopappus venetus, Helianthus niveus and Lotus spp.) in the fixed dunes. Mycorrhizal colonization in Abronia maritima was slight (<1%) and we observed few spores (<1/g soil). All of the species in the fixed dune formed mycorrhizae with up to 80% colonization in early summer, and no more than 4 spores/g soil by late summer. The highest percentages of total colonization and abundance of spores did not coincide temporally for any of the seven species, but the percentages were higher in summer than in spring. Arbuscules were more abundant when the soil was moist, and vesicles more abundant when it was dry. Accepted: 16 August 1995     

Phenology and photosynthetic activity in sterile and fertile sporophytes of Dryopteris filix-mas (L.) Schott

Summary This study describes the phenology of sporophytes of the fern Dryopteris filix-mas in relation to whole plant development. Sterile and fertile potted sporophytes were set out at an exposed site and the seasonal development of the fronds was measured from the commencement of unfolding, through the phase of increasing length, up to discoloration. The physiological activity of the fronds was determined by measuring photosynthetic gas exchange. The fronds of sterile sporophytes unfolded in April, about a week earlier than those of fertile plants, but the colour had already begun to turn in September and their life span was 1–2 months shorter. However, between mid-June and the end of August the sterile sporophytes put out several sets of new fronds: these overwintered without changing color and were still photosynthetically active in the following spring. All types of fronds were fully expanded 1–2 months from the beginning of unfolding and, with a natural supply of CO₂, had similar maximum net photosynthetic rates of 8–9 mol/m² · s. The decline in photosynthetic performance began before symptoms of senescence were visible and was due to decreased efficiency of the mesophyll. It is concluded that the phenology of D. filix-mas changes with transition from the sterile to the fertile phase. Whereas fertile sporophytes are genuinely summergreen, the sterile sporophytes with their summer fronds remain green throughout the winter and should therefore be termed semi-evergreen. The formation of overwintering summer shoots clearly extends the period of photosynthetic productivity of sterile sporophytes.     

First report of fern (Culcita macrocarpa) spore consumption by a small mammal (Apodemus sylvaticus)

Few vertebrates are known to consume ferns regularly. Several species of mammals consume leaves to some extent but the consumption of fern spores is much rare. In Galicia (Northwest Spain) we studied the seasonal variation in the consumption of Culcita macrocarpa fertile leaves (i.e. with spores) in two populations (Capelada and Eume), assessed whether consumption rate increased with fern population size, and evaluated whether the consumer was a spore predator or a spore disperser. Consumption began in December and finished by mid February, and occurred before spore release, which happened later in Capelada than in Eume, probably influenced by differences in altitude. The consumer was identified as Apodemus sylvaticus by DNA analysis of its droppings and by capture of live animals. Throughout Galicia there was a significant increase in fern consumption rate as the population size of C. macrocarpa increased. Germination tests from droppings were carried out in 14 dishes but only in two dishes 1% and 0.3% of the spores germinated. Our results suggest that woodmouse can disperse spores of C. macrocarpa, although most of the spores were digested.     

Airborne spore loads and mesoscale dispersal of the fungal pathogens causing Sigatoka diseases in banana and plantain

The mesoscale dispersal of ascospores and conidia of the fungal pathogenMycosphaerella fijiensis, causing Black Sigatoka disease in banana and plantain, was investigated under field conditions in Costa Rica. Spores were sampled daily during the period April–August 1995, using three volumetric spore traps positioned in a 5 km straight line across the floor and up one side of a valley, to an elevation of 1000 m. The number of spores in each trap suggested that spores were not being released from nearby sources, but that they may have been transported from inoculum sources up to 40 km away. The implications of this when assessing the longer-distance transport of viable spores to new infection sites are discussed.     

Quantitative expression of fern leaf development and fertility inPolystichum tripteron (Aspidiaceae)

To elucidate the quantitative and qualitative expression of fern development, various features of leaf-size and morphology were examined on leaves ofPolystichum tripteron (Aspidiaceae) in Japan. Among ten parameters, the number of branches of the leaf midrib (NV) proved to be the most successful for discrimination between fertile and sterile leaf populations. In the phase-change from sterile to fertile leaves, the NV parameter also gave the strongest correlation, increasing with fertility (r = 0.983), and is therefore a useful tool for research into the life history characteristics of ferns.Contribution no. 2751 from the Institute of Low Temperature Science, Hokkaido University.     

Arbuscular mycorrhizal fungal diversity and species dominance in a temperate soil with long-term conventional and low-input cropping systems

The aim of this work was to study the effect of long-term contrasting cropping systems on the indigenous arbuscular mycorrhizal fungal (AMF) spore populations in the soil of a field experiment located in western Finland. Conventional and low-input cropping systems were compared, each with two nutrient management regimes. The conventional cropping system with a non-leguminous 6-year crop rotation (barley–barley–rye–oat–potato–oat) was fertilized at either full (rotation A) or half (rotation B) the recommended rate. In the low-input cropping system, plant residues were returned to the plots either as such (rotation C) or composted (rotation D). In the rotation of this system, 1 year with barley was replaced by clover, and oat was cultivated mixed with pea. Thus, the 6-year rotation was barley–red clover–rye–oat + pea–potato–oat + pea. Each rotation was replicated three times, starting the 6-year rotation in three different years, these being designated point 1, point 2, and point 3, respectively. In the low-input system, biotite and rock phosphate were used to compensate for K and P in the harvested yield, while animal manure was applied at the start only. After 13 years, rotation points 1 and 3 were studied. Barley was the standing crop in all plots of rotation point 1, while oat and oat + pea were grown in rotations C and D, respectively. AMF spores were studied by direct extraction and by trapping, sampled on 15 June and 15 August. In addition, a special assay was designed for isolation of fast colonizing, dominating AMF. The cropping system did not significantly affect AMF spore densities, although the low-input cropping system with composted plant residues had the highest density with 44 spores on average and the conventional system with full fertilization 24 spores per 100 cm³ soil in the autumn samples. Species richness was low in the experimental area. Five Glomus spp., one Acaulospora, and one Scutellospora were identified at the species level. In addition to these, three unidentified Glomus spp. were found. Species richness was not affected by cropping system, rotation point, or their interactions. The Shannon–Wiener index of AMF spore distributions was significantly higher in the fully fertilized than in the half-fertilized conventional plots. Glomus claroideum was the most commonly identified single species in the experimental area. It occurred in all the cropping systems and their various rotation points, representing about 30% of the total number of identified spores. In August, G. claroideum accounted for as much as 45–55% of the total numbers of spores identified in the conventional system with halved fertilization. In contrast, Glomus mosseae occurred more commonly in June (26%) than in August (9%). A bioassay using roots as inoculum for isolation and culture of dominating AMF was successfully developed and yielded only G. claroideum. This indicates a high probability of being able to more generally identify, isolate, and culture fast colonizing generalist AMF for use as inoculants in agriculture and horticulture.     

The Seed and Fern Spore Bank of a Recovering African Tropical Forest

Seed banks contribute to forest regeneration after disturbance, but less is known about fern spore banks, particularly in a paleotropical context. We sampled the buried seed and fern spore bank in Mabira Forest, a 300 km² forest in central Uganda, to explore the effect of time since disturbance. Soil cores (5 cm depth) were taken from 39 plots across three different classes of ‘recovery’: (1) not disturbed since 1950; (2) logged between 1950 and 1980; and (3) cleared for agriculture between 1970 and 1990 but reforested since. Plant emergence was monitored in a glasshouse. We predicted that the seed bank would reflect time since disturbance, with more pioneer species in recently disturbed stands, and that the fern spore bank would reflect stand age less closely due to greater dispersal capacity. We recorded a median 752 seeds per square meter, most of which were trees; the most abundant species was the invasive tree Broussonetia papyrifera. The fern spore bank was twice as dense, but 95 percent of fern spores were of one species, Christella parasitica. Tree seed density was significantly affected by time since disturbance with fewer seeds in the older stands. Herb seed density, fern spore density, and species richness for all groups were not significantly affected by time since disturbance. Neither seed bank nor fern spore bank closely resembled the aboveground vegetation. We compared our results to existing literature on seed banks in tropical forests, finding that our densities are relatively high for African forests, but low compared to the Neotropics and Australia.     

Long-Term Survival of <Emphasis Type="Italic">Bacillus</Emphasis> Spores in Alcohol and Identification of 90% Ethanol as Relatively More Spori/Bactericidal

This study was taken up with a view to generate basic information on spore hardiness to ethanol in various Bacillus species and related genera, and to assess the effectiveness of different levels of ethanol as a bacterial disinfectant. Predominantly spore-bearing cultures of five Bacillus spp. (B. pumilus, B. subtilis, B. megaterium, B. fusiformis and B. flexus) that were isolated from the spent-alcohol used during plant tissue culture work were challenged with aqueous ethanol (25, 50, 60, 70, 80 and 90% v/v) in 1 ml volumes at 10¹⁰⁻¹¹ CFU ml⁻¹. Monitoring the spore endurance through spotting and plating revealed prolonged tolerance (>12 months) at different alcohol levels depending on the organism except in 90% where no survival was observed beyond 2–12 months. Spores of related genera like Paenibacillus and Lysinibacillus also showed long-term ethanol survival. Alcohol tolerance of spore-forming organisms depended on the extent of spores and spore hardiness, which in turn varied with the organism, strain, age of culture, growing conditions and other factors as authenticated with ATCC strains of B. pumilus and B. subtilis. Aqueous 90% ethanol caused instant inactivation of vegetative cells in different spore formers and twelve other non-sporulating Gram-positive and Gram-negative organisms tested. Taking into account both vegetative cells and spores, the appropriate concentration of ethanol as a disinfectant emerged to be 90% followed by absolute ethanol compared with the generally recommended 70–80% level.     

Geographical variation in frond size,rootstock density,and sexual reproduction in <Emphasis Type="Italic">Matteuccia struthiopteris</Emphasis> populations in Norway

The main aim of this study was to quantify differences in the structure of dense Matteuccia struthiopteris (L) Todaro among geographically separated populations in Norway, and to relate these differences to variation in environmental variables. A stratified random sampling procedure was applied to select 4 m² quadrats restricted to populations dominated (>75% cover) by the fern. This dimorphic fern can produce three types of leaves (fronds): fertile (sporophyll) and sterile (trophophyll), and in addition also intermediate fronds. In all, 178 populations from different parts of the country were analysed, and in total 9,346 rootstocks were measured. Fifteen percent of the rootstocks were fertile, each producing from one to eight sporophylls, and 2.0% had developed intermediate fronds. Rootstocks with five or more sporophylls were mainly found in Southern Norway. Within the plots, there were major variations in density (10–112), number of small (new) ramets (0–58), total number of sporophylls (0–94) and estimated total fern wet-weight (0.33–22.8 kg). All new additions to the populations were connected to a mother plant (ramets), and none were of sexual origin (genets). The main environmental variables associated with the variation in population structure were mean July temperature (highly correlated with altitude and latitude), mean precipitation and density of the canopy cover. The density of small ramets and number of intermediate fronds increased from south to north. The latitudinal variation in sporophyll development and maximum trophophyll height was best explained by a unimodal model. There were statistically significant differences in the population structure between the eight studied geographic areas in Norway.     

Influence of edaphic and climatic factors on dynamics of root colonization and spore density of vesicular-arbuscular mycorrhizal fungi in Acacia farnesiana Willd. and A. planifrons W.et.A.

 A study was conducted to assess the dynamics of vesicular-arbuscular mycorrhizal (VAM) fungi associated with Acacia farnesiana and A. planifrons in moderately fertile alkaline soils. The intensity of root colonization by VAM fungi and the distribution of VAM fungal structures varied with host species over a period of time. The occurrence of vesicles with varied morphology in the mycorrhizal roots indicates infection by different VAM fungal species. This was further confirmed from the presence of spores belonging to different VAM fungal species in the rhizosphere soils. Root colonization and spore number ranged from 56% – 72% and 5 – 14 g^{–  1}soil in A. farnesiana and from 60% – 73% and 5 – 15 g^{–  1} soil in A. planifrons. Per cent root colonization and VAM spore number in the rhizosphere soil were inversely related to each other in both the Acacia species. However, patterns of the occurrence of VAM fungal structures were erratic. Spores of Acaulospora foveata, Gigaspora albida, Glomus fasciculatum, G. geosporum and Sclerocystis sinuosa were isolated from the rhizosphere of A. farnesiana whereas A. scrobiculata, G. pustulatum, G. fasciculatum, G. geosporum and G. microcarpum were isolated from that of A. planifrons. The response of VAM status to fluctuating edaphic factors varied with host species. In A. farnesiana though soil nitrogen (N) was positively correlated with root colonization, soil moisture, potassium and air temperature were negatively correlated to both root colonization and spore number. Per cent root colonization and spore number in A. planifrons were negatively related to each other. Further, in A. planifrons as the soil phosphorus and N were negatively correlated with the density of VAM fungal spores, the same edaphic factors along with soil moisture negatively influenced root colonization. Received: 16 May 1995 / Accepted: 7 February 1996     

Protostelids from German Beech forests

A survey for protostelids from old-growth beech forests of northeastern Germany resulted in 14 species found in both ground and aerial litter, constituting the first survey of these organisms from Central Europe. Additionally the myxomycete Echinostelium bisporum was recorded as new for Germany. A detailed investigation of randomly sampled dead Fagus leaves (16 leaves on ground, 16 aerial leaves, three replicate cultures per leaf) resulted in 7 species; a hyperbolic regression of the respective species accumulation curve gives the theoretical value of 8.3 species. Protostelids occurred especially at aerial leaves with a high frequency (0.94). A program simulating random spore hits was written to calculate the minimum spore fallout necessary to explain this frequency. The resulting average value of about 3 spores per leaf can well be matched by the potential spore productivity estimated to be about 1000 spores per leaf for the most common species, Protostelium mycophaga.     

Intradiurnal periodicity of fungal spore concentrations (Alternaria, Botrytis, Cladosporium, Didymella, Ganoderma) in Cracow, Poland

Aerobiological monitoring enables the definition of seasonal fungal spore concentrations and also intradiurnal time when the highest concentrations of spores could cause or increase allergy symptoms. These data are useful to estimate symptoms of disease, duration of infection and how advanced the illness is in people suffering from fungal allergens. The aim of the study was to compare the concentrations of fungal spores (Alternaria, Botrytis, Cladosporium, Didymella, Ganoderma) during dry and rainy periods and to analyse their intradiurnal changes. Average daily spore concentrations in dry and rainy periods were compared, using z test, separately for each taxon, season and for a combined 3-year period. Intradiurnal periodicity of fungal spore concentrations was analysed on the basis of three complementary diagrams. These spore concentrations were presented using three curves for all, dry and rainy days in 1997–1999 (April–November). The spore percentage in particular hours was normalized in relation to the daily spore sum accepted as 100%. Two further diagrams enabled the more precise analysis of the highest concentrations in dry days. Daily Botrytis and Cladosporium spore concentrations did not show significant differences between dry and rainy periods. In the case of Didymella and Ganoderma spore concentrations, there were no significant differences between both weather types in the single years, although there was a significant difference when a 3-year period was considered. The differences between daily concentrations of Alternaria spores in dry and rainy periods occurred in 1997 and in a 3-year period. Intradiurnal periodicity of spore concentrations was different for ‘dry’ and ‘wet’ fungal spores. Dry spores are released from the spore-producing parts of the fungus under conditions of decreasing humidity and increasing airflow. Examples of dry spores are those from Alternaria, Cladosporium and Botrytis. Wet spores, such as those from many Ascomycetes (Didymella) and Basidiomycetes (Ganoderma), are released into the atmosphere by processes related to humidity conditions or rain. The highest concentrations of ‘dry’ spores were observed early in the afternoon, while highest values of ‘wet’ spore concentrations occurred in the predawn hours. Statistically non-significant differences between daily spore concentrations in dry and rainy periods of single seasons were found except for Alternaria. Statistically significant differences could occur when the studied period was longer than one season (Alternaria, Didymella, Ganoderma). The highest concentrations of Alternaria, Botrytis and Cladosporium spores were recorded at noon and early in the afternoon. Concentrations of Didymella and Ganoderma spores were highest in the predawn hours.     

海南七仙岭7种卷柏属植物的微观形态与生境间的关系分析

为探讨生境对卷柏属(Selaginella)植物微观形态的影响,利用扫描电子显微镜对海南七仙岭采集的7种卷柏属植物的侧叶、中叶、孢子叶的叶表皮形态以及小孢子形态进行全面观察分析,并计算气孔器大小、气孔密度、孢子大小等,比较分析其微观形态的区别及微形态与生境间的关系,为卷柏属植物的分类提供依据。结果显示:(1)同种卷柏属植物的侧叶、中叶与孢子叶在叶表皮形态上具明显差异,尤其是孢子叶上的气孔与营养叶相对较小且稀疏,与孢子叶的繁殖功能相符合。(2)不同种卷柏属植物的叶表皮特征也明显不同,主要表现在叶缘刺、气孔和瘤状突起上,表明这些特征可以作为卷柏属植物种间区分的依据。(3)卷柏属植物的小孢子形态稳定,纹饰多样;部分种间的小孢子形态相似,但可通过纹饰类型、裂缝的曲直进行区分。(4)琼海卷柏的小孢子具有独特的网状纹饰,暗示其具有独特的演化途径。(5)卷柏属植物叶表皮的气孔特征、瘤状突起特征,小孢子的颜色、纹饰,与海拔、生境的湿度有一定的相关性,但其形成机理有待进一步研究。     

Convergence in leaf phenology traits of two understory ferns in the northwestern Iberian Peninsula

Aims Plants control leaf phenology to maximize annual photosynthetic product. Although ferns play an important ecological role in many habitats, especially forests, their phenology traits have been poorly studied. Here, we investigate the leaf phenology of two ferns of the forest understorey and analyse the relationship between the timing of leaf emergence and spore dispersal and the effect of between-year climatic variation.Methods We compared the leafing and sporing phenologies of two ferns with very large (>2 m), overwintering leaves: Culcita macrocarpa and Woodwardia radicans. We regularly monitored individuals of six populations in the northwestern Iberian Peninsula during a 3-year study. We studied eight phenology variables: leafing start date, leafing end date, leaf expansion time, number of new leaves per individual, between-individual synchrony, within-individual synchrony, percentage of fertile leaves and spore release date. We also determined leaf mass per area (LMA) and gathered data on air temperature and humidity.Important findings Both C. macrocarpa and W. radicans produce few leaves (~2 leaves individual^-1 year^-1), which expand simultaneously for a very long period (from midwinter to early summer), are retained for more than 1 year (37 and 19 months, respectively) and have relatively high LMAs. Such traits, together with large leaf size, have also been found in seed plants from the forest understorey and represent adaptations to this light-limited environment. Spores of both study ferns are simultaneously released in late winter, with little between-year variation caused by differences in air humidity. This remarkable similarity between species suggests that the convergence in timing of leaf emergence favours the convergence in timing of spore dispersal.     

Responses of the mangrove fern <Emphasis Type="Italic">Acrostichum danaeifolium</Emphasis> Langsd. &; Fisch. (Pteridaceae,Pteridophyta) to disturbances resulting from increased soil salinity and Hurricane Georges at the Jobos Bay National Estuarine Research Reserve,Puerto Rico

Mortality of plants in a mangrove forest dominated by the tree Avicennia germinans began to appear at the southern coastal edge of the forest in the central watershed of the Jobos Bay National Estuarine Research Reserve in Puerto Rico in 1977. The dieback was attributed to salinities in excess of 70 ppt and gradually continued north until some tree mortality was observed in 1995 at the forest’s landward interface with agricultural land. Mortality of the common understory mangrove fern Acrostichum danaeifolium occurred at a much slower rate than tree mortality. Remediation at the forest’s edge was recommended in 1997 and a study to monitor A. danaeifolium at 4-month intervals was begun in January 1998 to determine how the ferns would respond to hydrologic change. Hurricane Georges passed over the reserve in September 1998, so the effects of this disturbance were assessed as well. In May 1998, 4 months after tagging individual plants, the mean number of leaves plant⁻¹ at the impact site was only half that for plants in a control area in the nearby undisturbed eastern watershed. Fertile (spore-bearing) leaf production in both watersheds was very low accounting for plant fertility of 7% or less. Short leaf lengths in the impact site combined with smaller plant leaf counts and much lower leaf production rates in one area of the impact site had resulted in biomass production at the control site that was 18 times greater than in the impact site. After Hurricane Georges plant mortality in the impact area increased with individuals of A. danaeifolium found dead on every monitoring date except September 1999. However, when means for all variables measured in both sections of the forest were compared within 8 months after the hurricane there was an increase in all growth characteristics except sterile leaf length. Relative plant fertility increased from 10% before the hurricane to over 50% by May 2000. The fertile leaf production rate of these plants increased nine-fold by May 1999, and though it declined slowly thereafter it was still almost three time pre-hurricane levels at the end of the study almost 2 years later. Biomass production rates, though very low in the 4 months after the hurricane, had increased to five times pre-hurricane levels by the end of the study in January 2001. Efforts at remediation of the hypersaline conditions that were completed in May 1999 at the landward edge of the impact area appeared to have little effect on the ferns. For A. danaeifolium, plant mortality and decreases in plant size characteristics were the most notable responses to high salinity levels. In contrast, increases in fertile leaf and biomass production rates were the most significant response to hurricane disturbance.