Redundância funcional de plantas lenhosas residentes do subosque de dois fragmentos de Mata Atlântica

O desempenho dos organismos em determinada condição ambiental depende das estratégias ecológicas desenvolvidas ao longo da sua evolução, as quais são expressas por combinações de atributos funcionais (AF) que conferem vantagem adaptativa em um dado habitat. Este estudo avaliou o padrão de convergência funcional de espécies de subosque de duas comunidades vegetais de Mata Atlântica, Floresta Ombrófila Densa, no sul do Brasil. Para isso, foram amostradas 15 parcelas por fragmento de estudo, com seleção de 30 espécies nativas residentes de subosque que foram descritas a partir de 16 AF morfológicos, ecofisiológicos, fenológicos e reprodutivos. Radiação luminosa, conteúdo de matéria orgânica e umidade gravimétrica foram as variáveis ambientais mensuradas. A análise funcional das comunidades foi realizada por meio do software SYNCSA. Os AF que maximizam a convergência entre as espécies foram: folha simples, oposta e elíptica, a floração na primavera, a condição ciófita e secundária, a via fotossintética C3, a polinização melitofílica e a dispersão ornitocórica de frutos polispérmicos. As duas comunidades estudadas são medianamente redundantes funcionalmente devido à convergência de AF entre as espécies. A redundância funcional fornece resiliência a comunidade, em consequência das respostas compensatórias das espécies, o que reforça a importância da vegetação do subosque para a manutenção dos processos ecossistêmicos e a latente necessidade de inclusão das espécies desse estrato florestal em ações de restauração ambiental. Functional redundancy of woody plants resident in the understory of two fragments of the Atlantic Forest A B S T R A C TThe performance of organisms in each environmental condition is based on the ecological strategies developed throughout their evolution, expressed in combinations of functional traits (FA) which verifies adaptive advantage in each environment. The study evaluated the trait convergence assembly patterns of understory species in two plant communities of Atlantic Dense Forest in southern Brazil. To answer the question, 15 plots were sampled per fragment of study, with a selection of 30 native species of understory that were described by 16 morphological, ecophysiological, phenological and reproductive traits. Luminous radiation, organic matter content and gravimetric moisture were the environmental variables measured. The functional analysis of communities was measured using the software SYNCSA. The AF that maximized the convergence between species was: simple, opposite and elliptical leaf, flowering during the spring, cyophyte and secondary condition, photosynthesis c3, melitophilic pollination and ornithochoric dispersion of polyspermyc fruits. The two communities studied are moderately functionally redundant due to species functional convergence. Functional redundancy provides resilience to the community, as a result of species compensatory responses, which reinforces the importance of understory vegetation for the maintenance of ecosystem processes and the latent need for the inclusion of the understory species in restoration actions.Keywords: functional traits, functional convergence, ecological strategy, functional redundancy, resilience.

Impacts of Nicotiana glauca Graham Invasion on the Vegetation Composition and Soil: A Case Study of Taif, Western Saudi Arabia

Invasive species are considered a serious problem in different ecosystems worldwide. They can compete and interfere with native plants, leading to a shift in community assembly and ecosystem function. The present study aimed to evaluate the effects of Nicotiana glauca Graham invasion on native vegetation composition and soil of the most invaded locations in the Taif region, Western Saudi Arabia, including Alwaht (WHT), Ar-Ruddaf (RDF), and Ash-shafa (SHFA). Plant species list, life span, life form, and chorotypes were assessed. Six locations highly infested with N. glauca shrubs were selected, and the morphological parameters of the shrubs were measured. Within each location, richness, evenness, relative density of species, and soil were measured either under the canopy of N. glauca shrubs or outside the canopy. Floristic analysis revealed the existence of 144 plant species, mainly perennial. The shrubs at the SHFA1 location showed the highest values of all measured morphological parameters. The WHT 1 location showed high richness and evenness, while the WHAT 2 location showed less richness and evenness. The invaded locations showed substantial variation in the community composition. Additionally, the effect of N. glauca on the understory species varied from competition to facilitation, where most of the understory species were inhibited. As an average of all locations, 65.86% of the plant species were recorded only outside the canopy of N. glauca. The vegetation analysis revealed that the SHFA location is more vulnerable to invasion that could be ascribed to its wide range of habitats and high disturbance. The soil–vegetation relationships showed significant variations among the studied locations regarding soil composition, and thereby showed a wide ecological range of the invasive shrubs N. glauca. Therefore, the invasion of N. glauca in the Taif region altered the species interactions, nutrients, and soil properties.

Allelopathic potential of Ficus retusa L. leaf litter on understory vegetation in urban gardens

Pruning Ficus trees in urban green spaces may lead to the accumulation and spread of their leaf litter on the understory vegetation. This study was conducted to evaluate the allelopathic effect of Ficus retusa L. leaf litter on the understory species in urban gardens. A field study showed that the plant cover and species richness of litter-affected plots were lower than those of litter-free areas. The litter-affected soils had substantially lower pH and higher electrical conductivity. In a greenhouse experiment, litter-affected soil significantly inhibited the emergence and growth of understory species selected for the purpose of this study: Melilotus indicus (L.) All., Trifolium resupinatum L. and Amaranthus viridis L. Osmotic potentials equivalent to those of the litter-affected soils did not affect emergence or growth of these species. A spectrophotometric analysis indicated that the litter-affected soils contained larger amounts of phenolics and flavonoids. An HPLC analysis revealed that the litter-affected soils contained higher concentrations of free phenolic and flavonoid allelochemicals. These results demonstrate that F. retusa leaf litter may reduce plant cover and species richness. The significant inhibition in both field and greenhouse experiments could be attributed to phenolic and flavonoid allelochemicals released from the tree litter, as the osmotic potential of the litter had no effect on the understory species. The allelopathic potential of F. retusa leaf litter plays at least a partial role in reducing urban vegetation.

Plantations on Forest Gaps and Edges Disturbs the Ecology of Threatened Understory Flora: A Case of Critically Endangered Gentiana Kurroo

Background: Within biodiversity hotspots, forest habitats have been disproportionately reduced and conservation efforts are insufficient, making restoration ventures extremely important. However, the impacts of restoration efforts on native threatened understory biodiversity residing in forest gaps and open edges have been seldom investigated. The current study attempts to fill this knowledge gap by investigating the ecology of a critically endangered understory plant namely Gentiana kurroo, across different successional stages of forest plantations including, open grassland (OG), 3-5-year-old plantation (YP), 5-15-year-old plantation (OP) and a mature forest (MF).Results: The highest population of the species was observed in OG, followed by YP, OP and MF. The regeneration was blocked by the plantation as evidenced by a ‘poor’ status in MF and OP, ‘fair’ at the YP and was ‘good’ only at OG. With an increase in canopy openness, the number of regenerating individuals increased, indicating the negative effect of the closed canopy on regeneration. The ordination projections show that the species density responds negatively with the stand basal area of the woody layer, litter depth, and tree density, but responds positively with soil organic carbon, available phosphorus, and reduction in the plantation. Conclusion: The present study suggests that plantations are more likely to benefit when established on degraded land rather than a replacement of the natural ecosystems, though those systems were initially forested or not. The results have significant implications in designing forest restoration programs, particularly on sites with a high diversity of threatened understory species. Thus, we propose that the forest restoration projects should be designed in a way that favours sensitive understory species without compromising the supply of timber and other non-timber forest products.

Fuel load, stand structure, and understory species composition following prescribed fire in an old-growth coast redwood (Sequoia sempervirens) forest

Background With the prevalence of catastrophic wildfire increasing in response to widespread fire suppression and climate change, land managers have sought methods to increase the resiliency of landscapes to fire. The application of prescribed burning in ecosystems adapted to fire can reduce fuel load and fire potential while minimizing impacts to the ecosystem as a whole. Coast redwood forests have historically experienced fire from both natural and anthropogenic sources, and are likely to respond favorably to its reintroduction. Results Random sampling was conducted in three burned sites and in three unburned sites, in an old-growth coast redwood (Sequoia sempervirens [D. Don] Endl.) forest. Data were collected on fuel, forest structure, and understory species composition and compared between treatments. Downed woody fuel, duff depth, litter depth, and density of live woody fuels were found to be significantly lower on sites treated with fire compared to unburned sites. Density of the dominant overstory canopy species, coast redwood and Douglas-fir (Pseudotsuga menziesii var. menziesii [Mirb.] Franco), remained consistent between treatments, and the abundance of herbaceous understory plant species was not significantly altered by burning. In addition, both downed woody fuel and live fuel measures were positively correlated with time since last burn, with the lowest measures on the most recently burned sites. Conclusions Our results indicated that the use of prescribed burning in old-growth redwood forests can provide beneficial reductions in live and dead surface fuels with minimal impacts to overstory trees and understory herbaceous species.

Evidence for Glacial Refugia of the Forest Understorey Species Helleborus niger (Ranunculaceae) in the Southern as Well as in the Northern Limestone Alps

Glacial refugia of alpine and subnival biota have been intensively studied in the European Alps but the fate of forests and their understory species in that area remains largely unclear. In order to fill this gap, we aimed at disentangling the spatiotemporal diversification of disjunctly distributed black hellebore Helleborus niger (Ranunculaceae). We applied a set of phylogeographic analyses based on restriction-site associated DNA sequencing (RADseq) data and plastid DNA sequences to a range-wide sampling of populations. These analyses were supplemented with species distribution models generated for the present and the Last Glacial Maximum (LGM). We used exploratory analyses to delimit genomically coherent groups and then employed demographic modeling to reconstruct the history of these groups. We uncovered a deep split between two major genetic groups with western and eastern distribution within the Southern Limestone Alps, likely reflecting divergent evolution since the mid-Pleistocene in two glacial refugia situated along the unglaciated southern margin of the Alps. Long-term presence in the Southern Limestone Alps is also supported by high numbers of private alleles, elevated levels of nucleotide diversity and the species’ modeled distribution at the LGM. The deep genetic divergence, however, is not reflected in leaf shape variation, suggesting that the morphological discrimination of genetically divergent entities within H. niger is questionable. At a shallower level, populations from the Northern Limestone Alps are differentiated from those in the Southern Limestone Alps in both RADseq and plastid DNA data sets, reflecting the North-South disjunction within the Eastern Alps. The underlying split was dated to ca. 0.1 mya, which is well before the LGM. In the same line, explicit tests of demographic models consistently rejected the hypothesis that the partial distribution area in the Northern Limestone Alps is the result of postglacial colonization. Taken together, our results strongly support that forest understory species such as H. niger have survived the LGM in refugia situated along the southern, but also along the northern or northeastern periphery of the Alps. Being a slow migrator, the species has likely survived repeated glacial-interglacial circles in distributional stasis while the composition of the tree canopy changed in the meanwhile.