Growth Of Ferns Research Articles

The ferns of Calilegua National Park, Jujuy, Argentina: A look through their spores. Second part

This work is part of a bigger project to study the spore morphology of isosporous ferns growing in the Calilegua National Park (CNP), in the province of Jujuy, Argentina. This park belongs to the phytogeographic region of the Yungas, where climatic and terrain conditions are optimal for the growth of ferns. The aim of this work is to present the morphology of the spores of 53 taxa corresponding to 6 families of isosporate ferns that grow in this protected area. The study was carried out with herbarium material and field trips. The families studied are Hymenophyllaceae, Ophioglossaceae, Polypodiaceae, Pteridaceae, Thelypteridaceae and Woodsiaceae. According to the spore aperture type, 24 taxa are monolete and 29 trilete. The spores are yellowish, light to dark brown or brown greenish. The largest spores belong to Pleopeltis tweediana and the smallest to Polyphlebium angustatum. The ornamentation observed were echinae, folds, wings, reticles, cristae, verrucae or rugulae. The spores of 35 species are illustrated for the first time under the light microscope and five species with scanning electron microscope. An identification key of the spores is also provided. The morphological characteristics of the spores allowed the identification of 16 species, contributes to spore bank analysis, aero and palaeopalynological studies and taxonomic identifications.

A phytochrome/phototropin chimeric photoreceptor promotes growth of fern gametophytes under limited light conditions.

Many ferns thrive even in low-light niches such as under an angiosperm forest canopy. However, the shade adaptation strategy of ferns is not well understood. Phytochrome 3/neochrome (phy3/neo) is an unconventional photoreceptor, found in the fern Adiantum capillus-veneris, that controls both red and blue light-dependent phototropism and chloroplast photorelocation, which are considered to improve photosynthetic efficiency in ferns. Here we show that phy3/neo localizes not only at the plasma membrane but also in the nucleus. Since both phototropism and chloroplast photorelocation are mediated by membrane-associated phototropin photoreceptors, we speculated that nucleus-localized phy3/neo possesses a previously undescribed biological function. We reveal that phy3/neo directly interacts with Adiantum cryptochrome 3 (cry3) in the nucleus. Plant cryptochromes are blue light receptors that transcriptionally regulate photomorphogenesis; therefore, phy3/neo may function via cry3 to synchronize light-mediated development with phototropism and chloroplast photorelocation to promote fern growth under low-light conditions. Furthermore, we demonstrate that phy3/neo regulates the expression of the Cyclin-like gene AcCyc1 and promotes prothallium expansion growth. These findings provide insight into the shade adaptation strategy of ferns and suggest that phy3/neo plays a substantial role in the survival and growth of ferns during the tiny gametophytic stage under low-light conditions, such as those on the forest floor.

Applications of pteridophytes in Himachal Pradesh, Western Himalaya: An ethnobotanical perspective

Ferns exhibit wide distribution in the Indian Himalayan Region (IHR), with Himachal Pradesh providing optimal climatic conditions for diverse fern species. This study documents the ethnobotanical applications of 45 pteridophyte species, spanning 16 families and 21 genera in Himachal Pradesh. Pteridophytes hold economic importance due to their edibility, ornamental appeal, and medicinal properties. Local communities extensively employ Pteridophytes with medicinal attributes to address various health concerns, including boils, wounds, colds, coughs, gastrointestinal diseases, gonorrhea, typhoid, urinary problems, uterine disorders, and hair loss. Moreover, Pteridophytes exhibit anti-inflammatory and anti-swelling properties, where plant paste is directly applied to the skin for swelling reduction. The monsoon season sees substantial growth of ferns in moisture-rich soil. Apart from their utilitarian purposes, ferns contribute to aesthetic values and serve as outdoor and ornamental plants. Noteworthy ornamental ferns, such as Adiantum capillus-veneris, Pteris cretica, Pteris multifida, Polypodium polypodioides, and Lepisorus thunbergianus, are acknowledged for their potential to enhance air quality. Diplazium esculentum, an edible fern, stands out as a popular and nutritious cuisine in Himachal Pradesh. The article concludes with recommendations for the conservation and sustainable utilization of ethnobotanically significant Pteridophytes in Himachal Pradesh.

Ferns Species Diversity in the Sekar Pudak Sari Waterfall Tourism Area, Wonosalam District, Jombang Regency, East Java, Indonesia

Ferns are significantly dominant in Indonesia. The waterfall area is one of the ferns habitats. This study aims to determine the diversity index of ferns species in the Tourism Area of Sekar Pudak Sari Waterfall Wonosalam District, Jombang Regency, East Java. This research was exploratory, descriptive. Data collection uses a single plot measuring 20x20 m at 500 masl, 700 masl, and 900 masl. Each observation plot has a sub-plot with a size of 2x2 m. Data analysis used the Shannon-Wiener diversity index (H'), the taxonomic diversity index (Δ), and dominance (Δ*). The exploration results found 28 species from 11 families, 6 epiphytes, and the rest terrestrial. The taxonomic diversity index in plot 1 was 23.36 (low category), while plots 2 and 3 were 30.58 and 31.66 (medium category). This shows that the environment in the three plots is classified as stable, as indicated by the presence of ferns at various taxonomic levels. The highest dominance diversity index (Δ*) was 2.8 in Plot 2, while Plots 1 and 3 were 2.7 (low category). The total number of individual ferns found influenced the difference in the diversity index. The ferns found in the three plots were relatively few, indicating that the environment was classified as less stable. The Shannon-Wiener diversity index (H') in the three plots was 2.9 (medium category), indicating that the distribution pattern of ferns in the environment was balanced. The Sekar Pudak Sari Waterfall Tourism Area is a suitable habitat for the growth of ferns, so conservation efforts need to be made to maintain a balance of species and stabilize the ecosystem.

Phytohormones in the regulation on growth and development of water ferns of Salviniaceae family: a review

Water ferns of the Salviniaceae family are successfully used for bioremediation and bioindication of contaminated waters. Due to intensive propagation they are able to produce a great volume of biomass enriched with natural plant growth regulators. Simultaneously, water ferns have become an impediment to the use of water resources through the fast spread. Their growth and development is under control of phytohormones, which are main chemical messengers regulating the responses to environmental changes. Today hormonal system of water ferns of the Salviniaceae family remains understudied. In this review, we analyzed and summarized the literature data and the results of our own research about the role of auxins, cytokinins, gibberellic, abscisic, salicylic and jasmonic acids in regulation of growth and development of water ferns from Salvinia and Azolla genera emphasizing the specific hallmarks of these phytohormones in ferns. We have submitted brief information about methodological approaches for endogenous phytohormones determination in water ferns of the Salviniaceae family. The effects of exogenous regulators on growth, development and tolerance of water macrophytes from Salvinia and Azolla genera were discussed, as well as the possibility of using water ferns to create ecological biofertilizers.

Composition and Diversity Variation of Ferns (Pteridophyta) at Barangay San Rafael, Prosperidad, Agusan Del Sur Philippines: Distribution and Conservation Status

Ferns (Pteridophyta) are free-sporing vascular plants with a unique life cycle with free-living gametophyte and sporophyte phases. The fern species has nearly 90% of the extant diversity, it was the first higher-level of pteridophyte classification in the world. This study aimed to assess and identify the different species composition and diversity variation of ferns found in the lower elevations at the primary forest in Barangay San Rafael, Prosperidad Agusan del Sur, Philippines. Moreover, the researchers were used the quadrat sampling method as one of the best and classic tools utilized in ecology especially determining the diversity of a specific sampling sites. Also, the study used Shannon’s diversity index method in determining the biological diversity of plant species particularly ferns (Pteridophyta). The total number of ferns that was primarily collected at Barangay San Rafael, Prosperidad, Agusan del Sur are nine (9) species from 5 families. The researchers linked the gathered data of ferns (Pteridophyta) by calculating its diversity index of 1.864, were showed medium diversity because most likely the pteridophyte communities were similar in all transects. Thus, the study area has medium species diversity results in a more complex, stable, and productive ecosystem as could be observed in San Rafael Forest. The results show that the growth and distribution of ferns was inhibited significantly by the environment properties.

Application of Foliar Fertilizer and Planting Media On Cattleya sp. Orchid Growth

Cattleya is one of the orchid genera, it has many fans. Labellum is large and strike colors. Intergeneric crosses have been made to produce soft colored flower, such as white, pink, red, yellow and brown. Cattleya orchids are known to have large flowers, and they are commonly referred to as The Queen of Orchid. These species are cultivated by several botanists as cut flower commodities. The price of cattleya is costly, so it becomes a business opportunity that needs to be developed. This study aims to examine the types of foliar fertilizers and planting media used on the growth of cattleya orchids. It was conducted between May and August 2021 in the experimental garden of the Faculty of Agriculture, UPN Veteran Yogyakarta using a Split Plot Design with factorial. The first factor, which is foliar fertilizer, consists of quick grow, AB mix, and focus grow. The second factor of planting media includes fern roots, black moss, and kadaka roots media. The result showed that AB Mix on fern and kadaka media produced similar plant height compared to other treatments. While on kadaka media, it produced the best leaf length and width, as well as shoot length. Furthermore, the shoot emergence and the number of roots did not show a significant difference. The plants that received quick grow treatment on kadaka and black moss media had similar growth. The number of roots provided the best growth of kadaka and ferns. Further study should be conducted to test AB Mix with various concentrations and planting media.

Clonal integration and phosphorus management under light heterogeneity facilitate the growth and diversity of understory vegetation and soil fungal communities

The spatial heterogeneity of light and nutrient deficiency occurs in many forest understories. Proper fertilization management of unhealthy forests can benefit forest understory diversity and improve the stability of degraded soil; and clonal integration is a major advantage of resource sharing for many forest understory vegetation, such as pteridophytes. In this study, we tested whether understory soil fertilization and clonal integration under light heterogeneity were able to increase the performance and diversity of understory vegetation and soil microbial communities in nature. Field experiments—with or without phosphorus (P) addition, with intact or severed rhizome, and under homogeneous or heterogeneous light environments—were conducted in the understory of a typical evergreen forest in southeast China.Light heterogeneity, P addition and clonal integration promoted the growth, diversity and evenness of ferns and soil microbial biomass C, N and P (MBC, MBN and MBP) at both experimental plot and patch level. They also increased Chao1 richness and Shannon diversity of soil fungal communities at patch level, especially in the high light patches with P addition. The positive effects of P addition and clonal integration on the growth and diversity of ferns and soil microbial biomass were greatly increased under heterogeneous light. The positive effects of clonal integration on the growth were the greatest in the heterogeneous high light patches. Moreover, the interactive effect of P addition and clonal integration increased soil MBN and MBP. Clonal integration promoted the increased growth and diversity of ferns and soil MBC in the heterogeneous light environment (9.35%–35.19%), and enhanced soil MBN and MBP in the P addition treatment (9.03%–12.96%). The interactive effect of P addition and clonal integration largely led to the transition of fungal groups from slow-growing oligotrophic types to fast-growing copiotrophic types.Our results show that the interactions between clonal integration and/or P addition under light heterogeneity increase the benefits of ferns in light-rich patches, and further promote integrative performance of ferns and soil microbial communities.

Abundance and seasonal growth of epiphytic ferns at three sites along a rainfall gradient in Western Europe

Vascular epiphytes in temperate zones are allegedly rare due to climatic constraints, such as drought and freezing temperatures during winter. Here, we investigate how abundance and seasonal growth of epiphytic polypod ferns in Western Europe are influenced by annual rainfall and temperature. We recorded abundances and growth of epiphytic polypod ferns over two years at three sites along a rainfall gradient from Southwest Ireland to Northwest Germany, spanning a two-fold difference in annual rainfall. We also investigated plant maturation and recorded key climate characteristics (rainfall and temperature). Abundance of epiphytic polypod ferns strongly decreased from the wetter end of the rainfall gradient in Ireland towards the drier end in Germany. Yet, frond turnover was equally high at all study sites during summer months, and equally low during winter. Plants showed only little to no expansive growth during the study period, except for the study site in France in the middle of the gradient, where the total number of fronds strongly increased. Similarly, we found an increase in the proportion of spore-bearing fronds at the French study site, whereas there was hardly any change between years at the other two sites. The observed growth patterns are inconsistent with the current differences in abundance of epiphytic ferns. We suggest that these differences are due to poor germination of spores under drier conditions and that small differences in annual growth have contributed to the current abundances over an extended time period. Surprisingly, seasonal frond productivity appeared to be unaffected by the amount of annual rainfall and average temperatures, although it seems likely that these factors do play a role during gametophyte establishment.

Endogenous phytohormone profiles in Pteris fern species differing in arsenic accumulating ability

Physiological and biochemical processes in plants are regulated by phytohormones. Phytohormone profiles are unknown in the fern family Pteridaceae. In this work, we analysed phytohormones in fronds and roots of three Pteris fern varieties with differing abilities in arsenic (As) accumulation. The ferns (hyperaccumulating P. cretica var. Albo-lineata and var. Parkerii, and non-hyperaccumulating P. straminea) were cultivated in a pot experiment with low contaminated soil (Astotal 16 mg kg−1, Aswater soluble 0.15 mg kg−1) for 185 days and harvested four times during growth. Phytohormone profiles were determined using high-performance liquid chromatography coupled to a hybrid triple quadrupole/linear ion trap mass spectrometer. We found twenty-five phytohormones and their structural and functional analogues (including growth and stress hormones) at detectable levels in fronds and roots. Interactions between growth hormones promoted the growth of ferns in the absence of environmental stress. Cytokinins of cis-zeatin type affected biomass yield, especially in the non-hyperaccumulator P. straminea. Phytohormone correlations between fern fronds and roots indicate a significant role for xylem-phloem transport and highlight the importance of transport in stress response. We observed similarities in phytohormone correlation profiles in the hyperaccumulators P. cretica var. Albo-lineata and var. Parkerii. In P. cretica var. Albo-lineata, interaction between jasmonic and abscisic acids was demonstrated, representing significant feedback of the defence response against oxidative stress by As. On the other hand, we did not find significant correlation among stress phytohormones in P. straminea. Profiling of growth and stress hormones in ferns confirms that they have specific phenotypic regulation. Hormonal regulations in the hyperaccumulator P. cretica var. Albo-lineata significantly differed from the non-hyperaccumulator P. straminea. A greater number of phytohormone correlations in the two hyperaccumulators suggests they use biosynthesised phytohormones more effectively.

Air humidity as key determinant of morphogenesis and productivity of the rare temperate woodland fern Polystichum braunii

(1) Most ferns are restricted to moist and shady habitats, but it is not known whether soil moisture or atmospheric water status are decisive limiting factors, or if both are equally important. (2) Using the rare temperate woodland fern Polystichum braunii, we conducted a three-factorial climate chamber experiment (soil moisture (SM)×air humidity (RH)×air temperature (T)) to test the hypotheses that: (i) atmospheric water status (RH) exerts a similarly large influence on the fern's biology as soil moisture, and (ii) both a reduction in RH and an increase in air temperature reduce vigour and growth. (3) Nine of 11 morphological, physiological and growth-related traits were significantly influenced by an increase in RH from 65% to 95%, leading to higher leaf conductance, increased above- and belowground productivity, higher fertility, more epidermal trichomes and fewer leaf deformities under high air humidity. In contrast, soil moisture variation (from 66% to 70% in the moist to ca. 42% in the dry treatment) influenced only one trait (specific leaf area), and temperature variation (15°C versus 19°C during daytime) only three traits (leaf conductance, root/shoot ratio, specific leaf area); RH was the only factor affecting productivity. (4) This study is the first experimental proof for a soil moisture-independent air humidity effect on the growth of terrestrial woodland ferns. P.braunii appears to be an air humidity hygrophyte that, whithin the range of realistic environmental conditions set in this study, suffers more from a reduction in RH than in soil moisture. A climate warming-related increase in summer temperatures, however, seems not to directly threaten this endangered species.

Aquatic ferns from the Upper Cretaceous Loncoche Formation, Mendoza, central-western, Argentina

Herein, we report new fossil remains with marsileaceous affinity associated with dispersed microspores corresponding to Crybelosporites, different types of massulae of Salvianiaceae (Paleoazolla patagonica and Azolla circinata), and a single megaspore assigned to the fossil genus Grapnelispora. These fossils were recovered from the Late Cretaceous Loncoche Formation, at the Calmu-Co section, Malargue Group, Northern Neuquen Basin, Mendoza, Argentina. The macrofossils include scattered leaflets, rhizomes, roots, and a sporocarp-like structure. They share characters with members of the aquatic fern family Marsileaceae; however, based on the characters preserved, they could not be placed within any extant or fossil species; therefore, the fossils are better included within a new fossil-taxon, Mendozaphyllum loncochense. Dispersed spores of Crybelosporites pannuceus, also belonging to Marsileaceae, were recovered from the entire section. Additionally, abundant isolated massulae with affinity to the aquatic fern family Salviniaceae, and a single megaspore assigned to Grapnelispora loncochensis, were identified from the plant bearing layer. The presence of Marsileaceae fossils in the Campanian–Maastrichtian Loncoche Formation, Mendoza, extends towards the north the paleogeographical distribution of the family Marsileaceae in Argentina, since previous records are from Patagonia. A fluvial to deltaic environment with lacustrine episodes is suggested by the sedimentology of the lower and middle parts of the Calmu-Co section and supported by the abundant fresh water algae recovered from the palynological association. This was probably the optimum habitat for the growth of aquatic ferns related to Marsileaceae and Salviniaceae and explains its abundance in the studied sediments.

Impact of mycorrhization on the abundance, growth and leaf nutrient status of ferns along a tropical elevational gradient

Mycorrhizal fungi are crucial for the ecological success of land plants, providing their hosts with nutrients in exchange for organic C. However, not all plants are mycorrhizal, especially ferns, of which about one-third of the species lack this symbiosis. Because the mycorrhizal status is evolutionarily ancestral, this lack of mycorrhizae must have ecological advantages, but what these advantages are and how they affect the competitive ability of non-mycorrhizal plants under natural conditions is currently unknown. To address this uncertainty, we studied terrestrial fern assemblages and species abundances as well as their mycorrhization status, leaf nutrient concentration and relative annual growth along an elevational gradient in the Ecuadorian Andes (500-4,000 m). We surveyed the mycorrhizal status of 375 root samples belonging to 85 species, and found mycorrhizae in 89% of the samples. The degree of mycorrhization decreased with elevation but was unrelated to soil nutrients. Species with mycorrhizae were significantly more abundant than non-mycorrhizal species, but non-mycorrhizal species had significantly higher relative growth and concentrations of leaf N, P, Mg, and Ca. Our study thus shows that despite lower abundances, non-mycorrhizal fern species did not appear to be limited in their growth or nutrient supply relative to mycorrhizal ones. As a basis for future studies, we hypothesize that non-mycorrhizal fern species may be favoured in special microhabitats of the forest understory with high soil nutrient or water availability, or that the ecological benefit of mycorrhizae is not related to nutrient uptake but rather to, for example, pathogen resistance.

Light Condition Influences Rutin and Polyphenol Contents in Asparagus Spears in the Mother-fern Culture System during the Summer–Autumn Harvest

We investigated the variation in rutin and total polyphenol contents in asparagus spears under different conditions of mother-fern culture. Rutin and polyphenol contents were highest at early spring harvest at all test sites. The contents gradually decreased during the harvest season. In particular, a considerable decrease was observed after the growth of mother ferns. The absorption of the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical was weaker in summer. Rutin content in the spears of plants grown outdoors was generally higher than in these grown in a greenhouse, except at early spring harvest. Rutin contents decreased in the spears of plants grown under a shading net or an ultraviolet (UV) radiation-filtering film. These results suggest that cultivation conditions, especially light conditions, have a great influence on rutin and polyphenol contents. We evaluated two new methods to increase rutin content by improving light conditions. Light conditions in asparagus rows were improved by using light-reflecting sheets and net screens; however, a significant increase in rutin content was observed only when net screening was used, implying that this method is better than light reflecting sheets to increase the rutin content.

CARBOHYDRATES AND YIELD PHYSIOLOGY OF ASPARAGUS – A GLOBAL OVERVIEW

The physiology of yield determination in asparagus (Asparagus officinalis L.) is complex. Above-ground growth of spears and ferns is the ultimate indicator of performance. However, growth is driven by soluble carbohydrate (CHO), which has a well-known pattern of gain and loss in the storage root system during the crop’s annual cycle. Root CHO content is a better performance indicator, now that the relationship between above-ground growth and CHO changes is better understood. Recent research has improved the definition of the root CHO pattern, and of benchmark CHO contents at key times during the growth cycle. Detection of deviations from the ‘ideal’ pattern can help with early diagnosis of problems. The research has also led to a simple method for assessing the CHO content of roots and to an internet-based system for delivering interpretations of CHO content data. Together, these components constitute the Aspire decision support system. In this paper we review this research. In particular, we explore four topics that are crucial for the viability of the concept: (a) evaluate whether Brix% of root sap can be used as a surrogate for analytical root CHO content; (b) compare root CHO content patterns in different countries, with different climates and management systems; (c) analyse the significance of root system size; and (d) analyse the physiological capacity of crops to produce CHO during fern growth. We conclude that, provided the implications of these factors are recognised, the approach can deliver benefits to asparagus growers. The Aspire system is becoming available to increasing numbers of growers around the world. Already it is being used by growers in New Zealand and North America, supporting them in making management decisions to improve yields and the long-term sustainability of their crops.

水生シダの生長に対する水稲除草剤間の影響比較

水生シダの生長に対する水稲除草剤間の影響比較

98/01824 A study on hydrocarbon migration and accumulation in coal measures of Turpan-Hami basin : Li, W. et al. Shiyou Xuebao, 1997, 18, (2), 8–12. (In Chinese)

New data of Chinese and Soviet palaeontologists and stratigraphers allow correlation between the Triassic plant-bearing beds of Siberia, China and western Europe. The early Triassic floras of these regions were much more connected than supposed.The western European and Chinese floras with xeromorphic plants belonged to the united European-Sinian palaeofloristic area which was once part of the Laurasian kingdom. The floras of the Tunguska and Kuznetsk basins, Taimyr and Verkhoyansk belonged to the Siberian area where a more humid climate allowed luxuriant growth of ferns. Thus the ferns were different in the Siberian and European-Sinian areas, whereas the conifers and the lycopods were very similar. The maritime areas were rich in lycopods; conifers and ferns were abundant in the intracontinental parts of Eurasia.The lower part of the Triassic may be considered as a transitional period from the Palaeophytic to the Mesophytic Its peculiarity is reflected in the composition of the fossil floras as well as in their distribution. The lower Triassic differs from the Palaeozoic (which shows a degree of isolation and differentiation of the phytochoria) as well as from the Mesozoic (characterized by the homogeneity of its floras) by the vast expansion of lycopods through all the phytochoria. Already by the Middle Triassic the general plan of the phytochoria becomes similar to the recent one.

98/01820 Recovery of coal from coal processing intermediate products : Blaszczynski, S. Pol. PL 172,433 (Cl. B03B7/00), 30 Sep 1997, Appl. 301,699, 29 Dec 1993, 4 pp. (In Polish)

New data of Chinese and Soviet palaeontologists and stratigraphers allow correlation between the Triassic plant-bearing beds of Siberia, China and western Europe. The early Triassic floras of these regions were much more connected than supposed.The western European and Chinese floras with xeromorphic plants belonged to the united European-Sinian palaeofloristic area which was once part of the Laurasian kingdom. The floras of the Tunguska and Kuznetsk basins, Taimyr and Verkhoyansk belonged to the Siberian area where a more humid climate allowed luxuriant growth of ferns. Thus the ferns were different in the Siberian and European-Sinian areas, whereas the conifers and the lycopods were very similar. The maritime areas were rich in lycopods; conifers and ferns were abundant in the intracontinental parts of Eurasia.The lower part of the Triassic may be considered as a transitional period from the Palaeophytic to the Mesophytic Its peculiarity is reflected in the composition of the fossil floras as well as in their distribution. The lower Triassic differs from the Palaeozoic (which shows a degree of isolation and differentiation of the phytochoria) as well as from the Mesozoic (characterized by the homogeneity of its floras) by the vast expansion of lycopods through all the phytochoria. Already by the Middle Triassic the general plan of the phytochoria becomes similar to the recent one.

98/01829 Trace element geochemistry of the Obed Mountain deposit coals, Alberta Canada : Gentzis, T. and Goodarzi, F. Fuel, 1997, 76, (14/15), 1491–1501

New data of Chinese and Soviet palaeontologists and stratigraphers allow correlation between the Triassic plant-bearing beds of Siberia, China and western Europe. The early Triassic floras of these regions were much more connected than supposed.The western European and Chinese floras with xeromorphic plants belonged to the united European-Sinian palaeofloristic area which was once part of the Laurasian kingdom. The floras of the Tunguska and Kuznetsk basins, Taimyr and Verkhoyansk belonged to the Siberian area where a more humid climate allowed luxuriant growth of ferns. Thus the ferns were different in the Siberian and European-Sinian areas, whereas the conifers and the lycopods were very similar. The maritime areas were rich in lycopods; conifers and ferns were abundant in the intracontinental parts of Eurasia.The lower part of the Triassic may be considered as a transitional period from the Palaeophytic to the Mesophytic Its peculiarity is reflected in the composition of the fossil floras as well as in their distribution. The lower Triassic differs from the Palaeozoic (which shows a degree of isolation and differentiation of the phytochoria) as well as from the Mesozoic (characterized by the homogeneity of its floras) by the vast expansion of lycopods through all the phytochoria. Already by the Middle Triassic the general plan of the phytochoria becomes similar to the recent one.

Forest recovery in abandoned tropical pastures in Puerto Rico

The conversion of tropical forests into pastures has increased dramatically in the last 20 years. Once these lands are abandoned it is not clear if they will recover to forest or if they will become permanent grasslands. Economic changes in Puerto Rico have led to the abandonment of agricultural lands over the last 60 years, providing an opportunity to assess the longer term patterns of forest recovery following human disturbance. This study focuses on the changes in vegetation in abandoned pastures ranging in age from 0 to 60 years or more in two replicate chronosequences. Species richness and density of woody species were very low during the first 10 years following abandonment and woody biomass did not increase substantially until approximately 15 years post-abandonment. Recovery in pastures is greatly delayed in comparison with forest recovery following other types of human and natural disturbance. The successional trajectory is quite different in comparison to those following natural disturbances in the nearby Luquillo Mountains. In particular, the initial colonizing species are not ‘typical’ pioneer species (e.g. Cecropia sp., Scheffleria morotononi), but a group of shrubs and treelets in the Rubiaceae, Melastomataceae, and Myrtaceae. The presence of grasses and the rapid colonization and growth of ferns and herbaceous species in the abandoned pastures appears to be a major factor inhibiting the establishment of secondary forest and imparts a selective barrier on the colonizing woody species.