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.