Plant-Soil Feedbacks for the Restoration of Degraded Mine Lands: A Review

Much effort has been made to remediate the degraded mine lands that bring severe impacts to the natural environments. However, it remains unclear what drives the recovery of biodiversity and ecosystem functions, making the restoration of these fragile ecosystems a big challenge. The interactions among plant species, soil communities, and abiotic conditions, i.e., plant-soil feedbacks (PSFs), significantly influence vegetation development, plant community structure, and ultimately regulate the recovery of ecosystem multi-functionality. Here, we present a conceptual framework concerning PSFs patterns and potential mechanisms in degraded mine lands. Different from healthy ecosystems, mine lands are generally featured with harsh physical and chemical properties, which may have different PSFs and should be considered during the restoration. Usually, pioneer plants colonized in the mine lands can adapt to the stressful environment by forming tolerant functional traits and gathering specific soil microbial communities. Understanding the mechanisms of PSFs would enhance our ability to predict and alter both the composition of above- and below-ground communities, and improve the recovery of ecosystem functions in degraded mine lands. Finally, we put forward some challenges of the current PSFs study and discuss avenues for further research in the ecological restoration of degraded mine lands.

An Assessment of the Phytoremediation Potential of Planted and Spontaneously Colonized Woody Plant Species on Chronosequence Fly Ash Disposal Sites in Serbia—Case Study

In this study, the potential of planted (Tamarix tetrandra Pall. ex M.Bieb. and Robinia pseudoacacia L.) and spontaneously colonized (Amorpha fruticosa L. and Populus alba L.) woody species for the phytoremediation of potentially toxic trace elements (TEs) such as As, B, Cr, Cu, Mn, Ni, Se, and Zn, from the chronosequence fly ash (FA) deposit lagoons (L1 and L2) at the ‘Nikola Tesla A’ Thermal Power Plant (TENT-A) in Serbia were analyzed. The differences in the pseodototal and bioavailable (DTPA-extractable) concentrations and mobility (AR index) of TEs in FA at the examined lagoons are a result of the time-conditioned influence of weathering (3 and 11 years respectively) and vegetation development on changing the basic physical and chemical properties of FA (texture, pH, EC, CEC, C, N, and bioavailable P and K) and its toxicity. This resulted in differences in the concentration of TEs in the roots and leaves of the examined plants at L1 and L2. All examined species accumulated Cr the most in the root (BAF > 1 and TF < 1), which suggests that they are good stabilizers of this element. Biological indices for As (BAF > 1 and TF < 1) identified T. tetrandra and A. fruticose as good stabilizers of As. P. alba stood out as accumulating the highest levels of B, Ni, and Zn, T. tetrandra the highest levels of Cu, Mn, and Se, and R. pseudoacacia the highest levels of As and B in leaves (BAF > 1; TF > 1), which makes them good extractors of these elements from the FA at TENT-A. However, due to toxic concentrations of As, B, Se, and Zn in their leaves, they are not recommended for the phytoremediation of the investigated lagoons through the process of phytostabilization. Under conditions of elevated total Cu and Ni concentration in FA, the content of these elements in the leaves of A. fruticosa at both lagoons were within the normal range. This, in addition to a good supply of essential Zn, the stabilization of As and Cr in the roots, an increase in BAF, and a decrease in TF for B with a decrease in its mobility in ash over time, singles this invasive species out as the best candidate for the phytostabilization of TEs in FA at the TENT-A ash deposit site.

Post fire ground vegetation development over 25 years

Fire has been a part of natural disturbance regime in boreal and to some extent also hemiboreal forests, affecting soil and light conditions, seedbanks, trees and ground vegetation. The most significant factors affecting occurrence, severity and size of forest fires are anthropogenic, weather and the environment, all of which are changing due to human-caused climate change. This paper discusses medium term (25 years) vegetation development in five different biotopes after fire disturbance. Sample plots were established in Slitere Reserve (now National park) in north-western Latvia on areas affected by large fire in 1992. Data were collected in 1993, 2002 and 2017. The aim of the study was to characterize the regeneration and succession of ground vegetation after the fire. In 1993, species such as bog-rosemary (Andromeda polifolia), heather (Calluna vulgaris) and cloudberry (Rubus chamaemorus) were observed in the ground vegetation a year after the fire. In 2002 liverworts appeared, indicating that the bog has acquired more stable and wetter conditions, but in 2017, liverwort mosses were no longer present and the percentage cover of Rubus chamaemorus decreased significantly and Calluna vulgaris, sphagnum sp., and Betula pendula were present in large quantities in the bog. Comparing these studied years, it can be concluded that all these years the biotopes and species have continuously developed and are regenerating.

Initial carbonate weathering is linked with vegetation development along a 127-year glacial retreat chronosequence in the subtropical high mountainous Hailuogou region (SW China)

Aims The retreat of glaciers is exposing new terrains to primary plant succession around the globe. To improve the understanding of vegetation development along a glacier retreat chronosequence, we (i) evaluated a possible link between base metal (Ca, Mg, K, Na) supply and vegetation establishment, (ii) determined the rates of the establishment of soil and plant base metal stocks, and (iii) estimated the size of the main base metal fluxes. Methods We determined base metal stocks in the soil organic layer, the mineral topsoil (0–10 cm), and in leaves/needles, trunk, bark, branches and roots of the dominating shrub and tree species and estimated fluxes of atmospheric deposition, plant uptake and leaching losses along the 127-yr Hailuogou chronosequence. Results Total ecosystem Ca and Mg stocks decreased along the chronosequence, while those of K and Na were unrelated with ecosystem age. Fortyfour and 30% of the initial stocks of Ca and Mg, respectively, were leached during the first 47 years, at rates of 130 ± 10.6 g m−2 year−1 Ca and 35 ± 3.1 g m−2 year−1 Mg. The organic layer accumulated at a mean rate of 288 g m−2 year−1 providing a bioavailable base metal stock, which was especially important for K cycling. Conclusions We suggest that the initial high Ca bioavailability because of a moderately alkaline soil pH and carbonate depletion in 47 years, together with the dissolution of easily-weatherable silicates providing enough Mg and K to the pioneer vegetation, contributed to the establishment of the mature forest in ca. 80 years.

Type IV Pili of Streptococcus sanguinis Contribute to Pathogenesis in Experimental Infective Endocarditis

This work provides evidence that type IV pili produced by Streptococcus sanguinis SK36 are critical to the ability of these bacteria to attach to and colonize the aortic heart valve (endocarditis). We found that an S. sanguinis type IV pili mutant strain was defective in causing platelet-dependent aggregation in a 24-h infection assay but not in a 1-h platelet aggregation assay, suggesting that the type IV pili act at later stages of vegetation development.

Aspirin or Ticagrelor in Staphylococcus aureus Infective Endocarditis: Where Do We Stand?

Infective endocarditis is a challenging disease with a high mortality and morbidity rate. Antibiotic prophylaxis is currently recommended in high-risk infective endocarditis patients. However, the use of antibiotics faces the challenge of a low efficacy and contributes further to the emerging infection rate by antibiotic-resistant strains, emphasizing the need for new therapeutic strategies. Platelets are essential in the initial phase of infective endocarditis, acting as first-line immune responders. During the first phase of disease, bacteria can interact with platelets and counteract platelet antimicrobial activities. Mechanistic in vitro and animal studies on the effect of aspirin on bacteria-platelet interactions and the prevention of vegetation development showed promising results. However, data from clinical studies on the outcome of infective endocarditis patients who were receiving medically indicated aspirin therapy remain controversial. Therefore, the benefit of antiplatelet agents in infective endocarditis prevention has been questioned. Besides aspirin, it has been discovered that the platelet P2Y12 receptor antagonist ticagrelor has antibacterial properties in addition to its potent antiplatelet activity. Furthermore, a recent study in mice and a case report remarkably indicated the ability of this drug to eradicate Staphylococcus aureus bacteremia. This review will focus on current knowledge on antibacterial activity of ticagrelor, compared to aspirin, pointing out main unanswered questions. The goal is to provide food for thought as to whether a prior ticagrelor therapy might be beneficial for the prevention of infective endocarditis.

Mapping of Vegetation Development Zone to Enhance the Coastal Community Resiliency

Climate change has implications for the environment and community such as the existence of climate-related disasters. The changes of weather cycle triggers flooding in coastal areas, then high water discharge eroded the soil and caused landslides. Land conversion of upstream area causes low water absorption and high run-off which also contributes to flooding and landslides in the downstream area. Efforts to normalize rivers and urban drainage have not been able to cope with floods and landslides. Therefore, it needs an effort to minimize these disasters. The vegetative approach is an alternative for mitigating floods and landslides that are considered more comprehensive which not only conserves landscapes but also contributes to increasing green open space provision. This study aims to analyse the possibility of applying a vegetative approach to improve the physical and socio-economic community’s resiliency in coastal areas from climate-related disasters. The research method used a quantitative method with data collection techniques through literature studies, field observations, and questionnaires. The data processing stages include analysis of the physical condition to determine the physical vulnerability of the area through the physical natural map overlay technique; analysis of the climate-related disasters impact on society through descriptive statistical analysis techniques; and analysis of the possibility of applying the vegetative approach by using spatial analysis techniques to determine the level of vulnerability and priority zones for vegetation development.

Early Breeding Conditions Followed by Reduced Breeding Success Despite Timely Arrival in an Alpine Migratory Songbird

Timing reproduction to coincide with optimal environmental conditions is key for many organisms living in seasonal habitats. Advance in the onset of spring is a particular challenge to migratory birds that must time their arrival without knowing the conditions on the breeding grounds. This is amplified at high elevations where resource availability, which is linked to snowmelt and vegetation development, shows much annual variation. With the aim of exploring the effects of variability in the onset of local resource availability on reproduction, we compared key life history events in an Alpine population of the Northern Wheatear (Oenanthe oenanthe) between years of contrasting timing of snowmelt. Based on remote sensed images, we identified 2020 as an exceptionally early snowmelt and green-up year compared to the preceding year and the long-term average. Individuals tracked with light-level geolocators arrived well before the snowmelt in 2020 and clutch initiation dates across the population were earlier in 2020 compared to 2019. However, observations from a citizen science database and nest monitoring data showed that the arrival-breeding interval was shorter in 2020, thus the advance in timing lagged behind the environmental conditions. While hatching success was similar in both years, fledging success was significantly reduced in 2020. A trophic mismatch in early 2020 could be a possible explanation for the reduced reproductive success, but alternative explanations cannot be excluded. Our results show that, despite the timely arrival at the breeding grounds and a contraction of the arrival-breeding interval, Wheatears were not able to advance breeding activities in synchrony with environmental conditions in 2020. Earlier reproductive seasons are expected to become more frequent in the future. We show that the negative effects of changing seasons in Alpine migratory birds might be similar to birds breeding at high latitudes, despite their shorter migratory distance.