Flora最新文献

Biological soil crusts (biocrust hereafter) are communities structured by the interaction between bacteria, fungi, algae, cyanobacteria, lichens and bryophytes over the most superficial particles of the soil. These complex communities are mostly found in arid and semiarid regions, but they can also be conspicuous members of the vegetation in moist tropical ecosystems. This study presents the first taxonomic and ecological investigation of biocrusts in three prevalent Brazilian rocky outcrop types: ironstone, quartzite-sandstone, and limestone, while also assessing the distribution of these outcrop types across Brazil as potential biocrust habitats. We identified thirty-four bryophyte species (29 mosses, 5 liverworts), seven cyanobacteria genera, and one genus from each of the Charophyta and Chlorophyta algae groups. Twenty-four of the species (19 mosses and 5 liverworts) have never been previously reported in biocrusts associations in any ecosystem. Six microhabitats were characterized. Analysis of soil composition in the studied rocky outcrops highlighted pH, total acidity, phosphorus, organic matter, calcium, and iron concentrations as key distinguishing factors, emphasizing limestone as the most unique environment among the outcrops studied. Positive co-occurrence patterns were observed solely in ironstone and limestone outcrops, suggesting potential ecological interactions between mosses and cyanobacteria. The proportions of Brazilian rocky outcrops within Protected Areas (PAs) exhibited disparities, with ironstone and limestone outcrops being the most threatened, representing only 0.25 % and 5.11 % of PA sites, respectively. Our findings address crucial knowledge gaps within these unique ecosystems, offering valuable insights for biocrust research.

Forest degradation is a serious global-scale environmental issue which caused the loss of biodiversity in subtropical broad-leaved forests. Though more studies focus on forest succession, understanding the patterns in variations of leaf tissue structure is essential for the restoration of secondary forest communities. In this study, we compared the stomatal properties and leaf anatomical traits of plants from different succession stages of communities in a subtropical broad-leaved forest. Results showed that most of the leaf functional traits varied apparently across different succession communities, with low trait variations in narrowly distributed species and higher trait CV in those that occurred in two or more communities. Shrubs and most of the small trees from grassland and shrub-grassland displayed significant higher leaf thickness, palisade mesophyll thickness, leaf palisade: spongy mesophyll thickness ratio, tightness of leaf palisade tissue. In contrast, many trees in primary forest possessed the lowest leaf thickness, stomatal density, potential conductance index, adaxial epidermis thickness, leaf palisade: spongy mesophyll thickness ratio, etc. Our trait principal component analysis (PCA) results lacked the clear clustering of plants from different succession communities. Changes of trait syndromes facilitated plants to coexist in one or more communities along successional subtropical forest. Thus, complex species compositions within different succession communities were shaped as the result of reducing the overlap of resource requirements and the competitive intensity of co-existing plants.

We investigated the impact of both early and late fires on native plant communities of the Campo Rupestre in the Sempre-Vivas National Park (PNSV, Brazil). Everlasting flower harvesters use late fires to stimulate flowering, while park managers have been implementing early fires to reduce flammable biomass and, therefore, the risk of wildfires. We aimed to explore the effects of fire on species composition, vegetation cover, and plant and flower stalks height to evaluate post-fire vegetation recovery, especially considering Comanthera species, which are highly valued by flower harvesters. The experimental design involved two areas (A1 and A2) in PNSV from May/2019 to January/2021. We installed eight 50 × 50 m plots in each area, being half submitted to experimental burnings and the other half unburned (control plots). A1 experienced early fire in May, and A2 a late fire in September. Initial phytosociological surveys revealed differences between A1 and A2, therefore, fire effects were treated separately for each area. In both A1 and A2, fire initially impacted species richness and abundance but the effect dissipated over time, with vegetation becoming similar to unburned plots. Fire also affected vegetation cover, which returned to its original condition within a year, influenced by seasonality and plant phenology. Plant communities experienced a temporary reduction in height (∼4 cm) in the months following fire, and recovered in the subsequent rainy season. However, a tendency for smaller plants persisted, and the average height of flower stalks took almost two years to fully recover. In general, the late fire conducted in A2 led to a slower recovery trajectory. These findings indicate rapid post-fire biomass recovery and minimal impact on plant species composition, highlighting the resilience of Campo Rupestre to single fires. Further studies are crucial to understand plant response to fires at different fire frequencies.

Genetic swamping by introgressive hybridisation threatens diversity, caused by climate warming particularly in mountainous regions worldwide. Recent studies resulted in a threatening perspective for Senecio hercynicus in the Bavarian Forest due to genetic swamping by introgressive hybridisation with its cogener S. ovatus. To examine the situation more closely, the distribution and hybridization of S. hercynicus and S. ovatus in high elevation regions of the Bavarian and Bohemian Forest was analyzed by restriction enzyme digestion of nrDNA ITS1 (PCR-RFLP; PCR restriction fragment length polymorphism). For a total of 706 samples from 94 different sample localities a hybrid index was inferred from the fragment band intensities after PCR-RFLP digestion. Boxplot diagrams of the hybrid indices show a tendency of western populations towards S. ovatus genotypes and for populations to the east towards S. hercynicus genotypes. When the hybrid index data was subjected to a regression analysis with nine factors (five habitat patterns inferred during sampling and four bioclimatic variables), only geographical longitude and latitude seemed to describe the observed distribution of S. hercynicus and S. ovatus significantly, arguing for the distribution and hybridisation patterns being shaped rather due to historical than to eco-climatological determinants. While a broad zone of hybridisation between the two species in the Bavarian and Bohemian Forest region was inferred, our study demonstrates that purebred S. hercynicus still exists and remnant stands of this species should be the target of species conservation measures.

One of the most prevalent plant species in the contaminated area around a sewage dumping lake at Khulais (Jeddah, Saudi Arabia) in the Arabian desert eco-region was found to be Amaranthus retroflexus L. This plant has the capacity to bioaccumulate and bioremediate heavy metals. The current study, therefore, aimed at investigating the plant's defense mechanisms by conducting metabolic and biochemical assessments. To this end, A. retroflexus plants were collected from the sewage dumping lake of Khulais, across five sites at varying distances from the lake, each exhibiting different level of heavy metal. The results indicated an increase in antioxidant defense system emerged as a protection strategy for A. retroflexus plants against soil contaminations. This, for instance, included the increased synthesis of polyamines (e.g., putrescine, spermidine, and spermine by +9–63%), flavonoids (e.g., naringenin, kaempferol, luteolin, and rutin by +10–146%), and phenolic acids (e.g., chlorogenic acid, gallic acid, caffeic acid, p-coumaric acid, chicoric acid, rosmarinic acid, and protocatechuic acid), increased by 10–254%. Additionally, plants adjusted their metabolic processes by synthesizing various low molecular weight amino acids, including proline (+19–299%), phenylalanine (+98–240%), glutamate (+34–492%), arginine (+10–64%), and ornithine (+51–210%). The activity of the metabolic enzymes involved in metabolism of these amino acids was enhanced accordingly. It can be concluded that the synthesis of polyamines and amino acids can be coordinated and complemented to improve the tolerance of A. retroflexus to cope with heavy metal accumulation in contaminated soils.

Family Convolvulaceae is dominated by climbing species and in most of the members, radial growth is achieved by forming vascular variants. The present study compares stem anatomy and structural modifications in the secondary xylem of Ipomoea eriocarpa R.Br. (Convolvulaceae) growing at Banni (Kachchh, arid zone) and at Toranmal (Tropical dry deciduous forest). Individuals growing at both biogeographic zones showed similar ontogeny for the development of successive cambia, inter-and intraxylary phloem, intraxylary cambium, and non-lignified axial (and radial) parenchyma wedges. However, as plants grew older, stems of individuals growing at Banni became lobbed in outline and showed the development of successive cambia and bidirectional intraxylary cambium. The thickest stems of samples from Banni possessed three successive cambial rings, vessels mostly solitary and relatively narrow in diameter with a greater number of non-lignified axial parenchyma wedges. In contrast, samples collected from Toranmal showed two successive cambial rings with relatively few numbers of non-lignified axial parenchyma wedges, intraxylary cambium was unifacial and exclusively produced intraxylary phloem. The secondary xylem was diffuse-porous, vessels usually in tangential multiples or clusters. Though, the time of seed germination and establishment of seedlings remained the same; in Banni samples, initiation of successive cambia, intraxylary cambium and its derivatives (i.e. xylem and phloem) began before the individuals growing at Toranmal. Samples from both locations showed the presence of inverse cambia on the inner margin of the xylem produced by the first successive cambium. These alterations in the behaviour may be correlated with the ephemeral lifecycle of Banni plants.

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.

The genus Psittacanthus is distributed from Mexico to Argentina and contains c. 110 species. The large, lipid-rich, one-seeded fruits of Psittacanthus species frequently depend on frugivorous birds for seed dispersal; however, fruit morphology of Psittacanthus (Loranthaceae) mistletoes remain poorly studied. In this study we describe the fruit morphology of nine Psittacanthus species. Fruits were collected from the study sites in which mistletoe plants were inhabiting contrasting habitats and host tree species. The morphological characteristics of fruits by species were described and compared with the use of inclusion and staining techniques and light microscopy. Our results show that fruit size varies among species, with P. macrantherus having the largest fruits. Most fruits have an ellipsoid to ovoid shape, color of fruits transits from green when immature to red or purple before ripening to blackish or purplish black, with color variations observed in different species, and the cupular pedicel length varying among species. Fruit sections indicate the following parts: exocarp, viscin layer, seed coat and a dicotylar to polycotylar embryo, with P. schiedeanus having the highest cotyledon count. No endosperm is present in the studied species. Our results provide valuable information for further species comparisons regarding the lack of endosperm and polycotylar embryo. Additionally, interspecific variation in cotyledon number and seed coat highlights distinct processes, including the potential effects of environmental differences.

Extreme drought events, driven by the El Niño Southern Oscillation (ENSO), are linked to increased tree mortality and alterations in vegetation structure, dynamics, and floristic composition in tropical forests. Existing analyses, primarily focusing on Africa, Central America, and Amazonia, overlook the floristic impacts on biome transitions. This study evaluates the profound effects of the severe 2015/2016 ENSO event on tree density and floristic composition in the critical transition zone between Amazonia and Cerrado, South America's largest biomes. Our findings not only document significant biodiversity loss but also offer insights into species resilience, guiding conservation strategies under changing climate conditions. We inventoried long-term plots before and after the extreme drought event, sampling 12,465 individuals from 526 species, 224 genera, and 65 families, in Open Ombrophilous Forest (OF), Seasonal Forest (SF), Cerradão (CD), and Typical Cerrado (TC). We document the disappearance from our plots of 97 species after the ENSO, with only 61 new species being recorded. The total loss of individuals across the transition zone was almost 10 %. The SF and CD forest plots showed the greatest replacements, species losses, and reductions in tree density. Their markedly seasonal baseline climate probably drove these changes. In most phytophysiognomies, there was an increase in pioneer species and drier environment habitat specialist species, indicating that although many species are vulnerable to extreme climate events, others benefit, especially those with a short life cycle. We found that the vegetation of the Amazonia-Cerrado transition overall is vulnerable to climate anomalies, with widespread loss of tree density and change in floristic composition. Our study also provides a species-by-species list of the most vulnerable and resistant trees which helps point to overall climate change vulnerabilities and assist with initiatives to recover degraded areas.