Soil Plant Species Research Articles

Increasing soil microplastic diversity decreases community biomass via its impact on the most dominant species

Ecosystems experience strong microplastic pollution and the ecological impacts of microplastic pollution have received increasing attention. While an ecosystem can be contaminated by different numbers of microplastics, no study has tested the impacts of the diversity of microplastic types on plant communities. We constructed an experimental plant community with six plant species in soils with three levels of microplastic diversity (1, 2 and 4 microplastic types) using six types of common microplastics differing in chemical composition and/or morphology, i.e., polystyrene foams (EPS), polyethylene fibers (PET), polypropylene fibers (PP), polyethylene beads (HDPE), polylactic beads (PLA), and polyamide beads (PA6). Different microplastic types in the soil differed significantly in their impacts on total and shoot biomass of the plant community, but not on its species evenness. Interestingly, total, shoot and root biomass of the plant community decreased significantly with increasing soil microplastic diversity. This was because shoot biomass of the dominant species Lolium perenne decreased significantly with increasing soil microplastic diversity. Consequently, species evenness of the plant community tended to be higher in the treatment with two and four microplastic types than in the treatment with only one type. Therefore, microplastic diversity in the soil can influence productivity of plant communities. These results highlight the importance of taking microplastic diversity into account when testing the ecological impacts of microplastics.

Assessment of Phytoremediation Potential of Three Weed Plant Species in Soil Contaminated with Lead and Chromium

The study aimed to compare the tolerance capacity of Cyperus iria, Achyranthes aspera, and Eruca sativa to lead-contaminated and chromium-contaminated soils and to check their phytoremediation potential by pot culture experimentation. The experiment was conducted in three replicates in pots having 4 kg of sieved soil mixed with different doses of chromium, 0, 50, 100, 150, 200, 250, 300, and 350 mg·kg−1, and lead, 0, 100, 200, 300, 400, 500, 600, 700, and 800 mg·kg−1. The experiment was conducted for 80 days, and roots were harvested two times, i.e., at 40 days and 80 days after sowing. Metal accumulation in the roots was determined by the atomic absorption spectrophotometry method. The result of the study indicated that C. iria has the maximum potential to accumulate both the metals in its roots than other two plants. The order of chromium metal accumulation was found to be C. iria > E. sativa > A. aspera. On the other hand, the order of lead metal accumulation was found to be C. iria > A. aspera > E. sativa.

Spatial variations of plant species diversity in urban soil seed banks in Beijing, China: Implications for plant regeneration and succession

The near-to-nature urban forestry concept and practices are widely recognized for urban greening, urban ecosystem restoration, urban greenspace management for biodiversity conservation and ecosystem services provision. However, the regeneration and succession of urban vegetation are rarely studied due to the complex settings of the urban environment. To this end, we conducted a large-scale field investigation in the metropolitan area of Beijing, China to explore the spatial variations in plant species composition and diversity in soil seed banks, and their similarity to the aboveground vegetation to assess the potential of urban plant regeneration. Overall, 657 vegetation and soil sampling plots from 219 grids, measuring 2 km × 2 km each, were investigated within two perpendicular 10 km wide transects running across the urban center in north-south and east-west directions within the 6th Ring Road of the city. We recorded a total of 102 plant species in soil seed banks, including 13 tree species, 10 shrub species, and 79 herb species. We found that the soil seed bank species diversity and its similarity to that of the aboveground vegetation communities decreased significantly with the urbanization intensity. Higher urbanization intensity is typically associated with increased human management and a reduction in Greenspace Area (GSA). Soil seed bank species richness increased significantly when GSA exceeded 45 % and the similarity of species composition and diversity between soil seed banks and aboveground vegetation communities was the highest in forest parks. This suggests that habitats under forest park management are more conducive to plant regeneration. Soil seed bank species diversity first increased and then decreased significantly with increased distance to the city center, whereas the species similarity between the soil seed banks and the aboveground vegetation communities showed little change with the ring roads going out. The results of this study have important implications for further understanding the potential for urban vegetation regeneration and sustainability, which have significant implications for urban biodiversity conservation and restoration.

Phytoremediation potential of spontaneous plant species in soils contaminated by hexavalent chromium in Djelfa city (Algeria)

This study aims to quantify hexavalent chromium in wastewater, plants and topsoil in Djelfa city (South of Algeria) in order to better understand the bioaccumulation and phytoremediation potential of eight spontaneous plant species growing in a polluted environment, namely Sisymbrium Irio, Spinacia oleracea, Avena Sativa, Silybum Eburneum, Euphorbia Bupleuroides, Thapsia Garganica, Hertia Cheirifolia and Marrubium Vulgare. Wastewater, soil and spontaneous plant samples were collected near Djelfa’s Oued Mellah valley. Spectrophotometric measurements of hexavalent chromium concentration were used to determine pollution levels and to assess the accumulation potential of studied spontaneous plants. The results showed that in wastewater, soil and plant samples, Cr(VI) concentrations near the tannery upstream were 0.6 mg/L, 44 mg/kg and 6.2 mg/kg respectively. The most significant bioaccumulation potential was recorded with Thapsia Garganica while the highest translocation factor (TF) was found in Marrubium Vulgare. These species could be considered as a promising phytoremediation solution for chromium-polluted soils. According to plant sample enrichment factor (EF), the roots of almost all tested plants were found to be more effective to accumulate Cr(VI) than shoots.

Can locally sourced inoculum and biochar synergistically improve the establishment of mycorrhizal fungi in mine tailings?

The severely degraded soils at abandoned mine lands present several environmental challenges, including extreme pH, nutrient deficiency, and compaction, which can limit plant growth. Amending soils with biochar and/or mycorrhizal fungi may attenuate these constraints. However, the efficacy of amendments for improving the establishment of native plant species in restorations can be context dependent; pairing the right plant species with the right amendment is crucial to the success of restoration goals. In a greenhouse experiment, we evaluated the growth responses of two native plant species in soils collected from the Formosa Mine Superfund Site (Riddle, OR, U.S.A.). Seedlings of Elymus glaucus and Pseudotsuga menziesii were grown in tailings amended with biochar, locally collected rhizosphere soil containing a suite of soil microorganisms including mycorrhizal fungi, a combination of biochar and rhizosphere soil, or were unamended. We hypothesized that (1) individual amendments would increase plant biomass compared to controls and (2) that the co‐amended treatments would have a synergistic effect on plant growth. Instead, we detected no effect of rhizosphere soil or the co‐amendment on the growth of either plant species and found that biochar reduced the shoot biomass and leaf chlorophyll content of E. glaucus. Despite the lack of growth response, we observed significant rates of mycorrhizal colonization in the plants amended with local rhizosphere soil, demonstrating that locally sourced fungi can survive and proliferate in the amended Formosa tailings. Thus, inoculated seedlings of native plant species could provide essential ground cover and long‐term habitat for developing mycorrhizal communities in mine tailings.

Seed bank longevity and germination ecology of invasive and native grass species from Mediterranean wetlands

Most Mediterranean wetlands are overexploited and degraded by different factors and are especially vulnerable to alien and invasive species. Currently, there is still a lack of knowledge on certain aspects of plant invasions, especially from an applied point of view, as key tools in restoration and conservation programmes. In this sense, Cortaderia selloana has showed a rapid expansion in the western Mediterranean Basin, threatening habitats of special interest such as wetlands. A comparative study between C. selloana and Saccharum ravennae, a representative plant of Mediterranean marshlands, was carried out to characterize the biological pattern that has made C. selloana a potential threat. The role of these plant species in soil seed banks and the potential competitive displacement of S. ravennae were evaluated through seed germination and viability tests under accelerated ageing conditions and seedling root development, considering seed morphological characteristics, seed maturity and plant sexuality as influential factors. Additionally, the potential allelopathic effects of C. selloana leaves on S. ravennae seed germination were evaluated. The study found differences between the species in all the tested parameters, seed morphology, germination response and longevity, adsorption isotherm curves, and allelopathic effects. All these factors establish a complex interaction that contributes to the proven invasive character of C. selloana. These results provide useful data for eradication and management programmes.

The effects of rainforest fragment area on the strength of plant-pathogen interactions.

Pathogenic interactions between fungi and plants facilitate plant species coexistence and tropical rainforest diversity. Such interactions, however, may be affected by forest fragmentation as fungi are susceptible to anthropogenic disturbance. To examine how fragmentation affects fungus-induced seed and seedling mortality, we sowed seeds of six plant species in soils collected from 21 forest fragments. We compared seedling establishment in unmanipulated soils to soils treated with fungicides. Fungicides increased germination of Toona ciliata seeds and decreased mortality of Syzygium rubicundum and Olea dioica seedlings. The fungus-induced mortality of one of these species, S. rubicundum, decreased with decreasing fragment size, indicating that its interactions with pathogenic fungi may weaken as fragments become smaller. We provide evidence that a potential diversity-maintaining plant-fungus interaction weakens in small forest fragments and suggest that such disruptions may have important long-term consequences for plant diversity. However, we emphasize the need for further research across rainforest plant communities to better understand the future of diversity in fragmented rainforest landscapes.

Biotic and abiotic plant–soil feedback depends on nitrogen‐acquisition strategy and shifts during long‐term ecosystem development

Abstract Feedback between plants and soil is an important driver of plant community structure, but it remains unclear whether plant–soil feedback (PSF): (i) reflects changes in biotic or abiotic properties, (ii) depends on environmental context in terms of soil nutrient availability, and (iii) varies among plant functional groups. As soil nutrient availability strongly affects plant distribution and performance, soil chemical properties and plant nutrient‐acquisition strategies might serve as important drivers of PSF. We used soils from young and old stages of a long‐term soil chronosequence to represent sites where productivity is limited by nitrogen (N) and phosphorus (P) availability, respectively. We grew three N‐fixing and three non‐N‐fixing plant species in soils conditioned by co‐occurring conspecific or heterospecific species from each of these two stages. In addition, three soil treatments were used to distinguish biotic and abiotic effects on plant performance, allowing measurements of overall, biotic, and abiotic PSF. In young, N‐poor soils, non‐N‐fixing plants grew better in soils from N‐fixing plants than in their own soils (i.e., negative PSF). However, this difference was not only associated with improved abiotic conditions in soils from N‐fixing plants but also with changes in soil biota. By contrast, no significant PSF was observed for N‐fixing plants grown in young soils. Moreover, we did not observe any significant PSF for either N‐fixing or non‐N‐fixing plants growing in old, P‐impoverished soils. Synthesis. The direction and strength of plant‐soil feedback (PSF) varied among N‐acquisition strategies and soils differing in nutrient availability, with stronger plant‐soil feedback in younger, N‐poor soils compared to older, P‐impoverished soils. Our results highlight the importance of considering soil nutrient availability, plant‐mediated abiotic and biotic soil properties, and plant nutrient‐acquisition strategies when studying plant‐soil feedback, thereby advancing our mechanistic understanding of plant‐soil feedback during long‐term ecosystem development.

Two grass species fail to display differing species-specific effects on soil bacterial community structures after one season of greenhouse growth

Background and aims Plant impacts on soil microbial community composition and function are believed to be important but remain poorly understood. We looked at the bacterial community effects of growing two different plant species in soils with differing plant growth histories.

Some plants like it warmer: Increased growth of three selected invasive plant species in soils with a history of experimental warming

Abstract Soil warming can affect plant performance by increasing soil nutrient availability through accelerating microbial activity. Here, we test the effect of experimental soil warming on the growth of the three invasive plant species Trifolium pratense (legume), Phleum pratense (grass), and Plantago lanceolata (herb) in the temperate-boreal forest ecotone of Minnesota (USA). Plants were grown from seed mixtures in microcosms of soils with three different warming histories over four years: ambient, ambient +1.7 °C, and ambient +3.4 °C. Shoot biomass of P. pratense and P. lanceolata and plant community root biomass increased significantly in soils with +3.4 °C warming history, whereas T. pratense responded positively but not significantly. Soil microbial biomass and N concentration could not explain warming effects, although the latter correlated significantly with the shoot biomass of P. lanceolata . Our results indicate that soil with a warming history may benefit some invasive plants in the temperate-boreal ecotone with potential impacts on plant community composition. Future studies should investigate the impact of warming-induced differences in soil organisms and nutrients on plant invasion.

Nitrogen supply effects on leaf dynamics and nutrient input into the soil of plant species in a sub-arctic tundra ecosystem

Global warming will lead to increased nitrogen supply in tundra ecosystems. How increased N supply affected leaf production, leaf turnover and dead leaf N input into the soil of Empetrum nigrum and Andromeda polifolia (evergreens), Eriophorum vaginatum (graminoid) and Betula nana (deciduous) in a sub-arctic tundra in northern Sweden between 2003 and 2007 was experimentally investigated. There was considerable interspecific variation in the response of leaf production to N addition, varying from negative, no response to a positive response. Nitrogen addition effects on leaf turnover also showed considerable variation among species, varying from no effect to increased leaf turnover (up to 27% in Eriophorum). Nitrogen addition resulted in a four to fivefold increase in N content in the dead leaves of both evergreens and a 65% increase in Eriophorum. Surprisingly, there was no increase in Betula. The response of dead leaf P contents to N addition was rather species specific. There was no response in Empetrum, whereas there were significant increases in Andromeda (+214%) and Eriophorum (+32%), and a decrease of 47% in Betula. As an overall result of the changes in leaf production, leaf turnover and dead leaf N and P contents, nitrogen addition increased in all species except Betula the amount of N and, for Andromeda and Eriophorum the amount of P transferred to the soil due to leaf litter inputs. However, the way in which this was achieved differed substantially among species due to interspecific differences in the response of the component processes (leaf production, leaf turnover, dead leaf nutrient content).

Selenium and Sulfur Accumulation and Soil Selenium Dissipation in Planting of Four Herbaceous Plant Species in Soil Contaminated with Drainage Sediment Rich in Both Selenium and Sulfur

Four selenium (Se) nonaccumulator plant species, including a forage grass species, Tall Fescue (Festuca arundinacea Schreb.), a forage legume species, Alfalfa (Medicago sativa L.), a wetland species, Rush (Juncus tenuis Wild.), and a dry-land alkaline soil species, Saltgrass (Distichlis spicata L.), were grown in soil contaminated by agricultural drainage sediment having elevated levels of Se and sulfur (S). The above-ground plant tissues were consecutively harvested five times and examined for Se and S accumulation. Plant tissue Se concentrations ranged from 23.0 mg kg−1 to 8.3 mg kg−1. Tissue S concentrations ranged from 3239 mg kg−1 to 7034 mg kg−1. Both tissue Se and S concentrations were significantly different between harvests, species, and species/harvest interactions. Total Se accumulation by the plant biomass harvested ranged from 0.3 to 1.3 mg per soil column and total S accumulations ranged from 87.5 to 321.1 mg per soil column.The reduction in the percentage of total soil Se after 24 weeks growth of the plant species ranged from 12.0% in the Tall Fescue planting to 17.3% in the Rush planting. Over 90% of the soil Se losses were unidentified losses and leaching of Se was prevented. The accumulations of Se and S in the plant biomass were very small compared with the total soil Se and S losses, but substantial amounts of total soil Se (12.0 to 15.0%) and S (28.0 to 50.9%) inventories were dissipated by the growing and harvesting of the plants. The soil S concentration was several hundred times higher than the soil Se concentration, but Se accumulation by the plants and Se dissipation from the soil were not impaired by the high level of soil sulfur. For natural grassland habitat restoration, such as at the Kesterson Wildlife Refuge in the Central Valley of California, or for restoration of large-scale Se contaminated agricultural lands, Se nonaccumulator plant species are favorable candidates, because the possibility of introducing Se toxicity into the food chain can be minimized.

Allelopathic activity of Mexican sunflower [Tithonia diversifolia (Hemsl.) A. Gray] in soil under natural field conditions and different moisture conditions

The allelopathic activity of Mexican sunflower [Tithonia diversifolia (Hemsl.) A. Gray] in soil under natural field conditions and the effect of water stress on the growth and allelopathic activity of this plant were investigated. Seed germination, shoot growth and root growth of tested plant species in soil collected from a field where Mexican sunflower had been grown for 5 years were less than those in soil from an area without the plant. Growth of young leaves, mature leaves, senescent leaves, stem and roots of Mexican sunflower was reduced with decrease in soil moisture level. The allelopathic activity of water extracts (per dry weight of starting material) from each part of the plants grown at low soil moisture levels was greater than that of the water extracts from the same part of the plants grown at high soil moisture levels. The allelopathic activity was found in the soil from the pots previously planted with Mexican sunflower to a similar extent (per plant) at different soil moisture levels. These results suggested that, in the field, under water stress conditions, the growth of Mexican sunflower was reduced but the plants contained a greater amount of allelopathic substance(s) per dry weight than in the absence of water stress. It was considered that allelopathic activity of Mexican sunflower in soil was maintained to a similar extent under various soil moisture conditions in natural fields.

Natural Establishment and Selenium Accumulation of Herbaceous Plant Species in Soils with Elevated Concentrations of Selenium and Salinity under Irrigation and Tillage Practices

The effects of irrigation and tillage practices were studied on species richness, biomass, and selenium accumulation of naturally established herbaceous plants in soils with elevated levels of selenium (Se) and salinity at Kesterson Reservoir, Merced County, California. The four different irrigation-tillage practice combinations were (1) no irrigation, no tillage; (2) irrigation, no tillage; (3) no irrigation, tillage; and (4) irrigation, tillage. The fields were allowed to become colonized naturally by herbaceous plant species. For the Mediterranean climate in the study site, irrigation was conducted biweekly through the summer months, and tillage was done in 3-month intervals. Biomass and Se accumulation of Atriplex patula L, Bassia hyssopifolia Kuntze, Rev. Gen. P1., Melilotus indica (L.) All., and Solola kali L. were substantially affected by irrigation. The degree and direction of the effects were found to be species dependent. The field plots which were tilled at 3-month intervals remained bare throughout the experiment. The total soil Se concentrations in the top 15 cm soil horizon were found to be in the range of 40 to 70 mg kg−1 dry wt. Soil Se concentrations below 25 cm soil depth were much lower and within a range of 2 to 4mg kg−1. Less than 110th of the total soil Se inventory in the top soil horizon was water extractable, and the distribution of the Se inventory did not change significantly over the period of 1990 and 1991 despite the irrigation and tillage practices suggesting that a large portion of the Se inventory was not remobilized. The water-extractable soil Se concentration was found to be significantly lower in soils with the greatest biomass production suggesting an effective bioextraction of soil selenium by the native herbaceous plants.

The Allelopathic Influence of Avena fatua: The Allelopathic Mechanism

TINNIN, R. O., anid C. H. MULLER (Uniiv. of Calif., Santa Barbara). The allelopathic inifluenee of Avena fatua: The allelopathic mechanism. Bull. Torrey Bot. Club 99: 287292. 1972.-The allelopathic mechanism associated with the straw of Avena fatua was inivestigated by bioassay and greenihouse experiments. Water leachates from the straw contained a group of phytotoxic pheniolic compounds. These compounids were inihibitory to germinationi anid seedlinig growth of other plant species in soil and are thought to be part of the toxic complex which is active in the field. We conielude that the phytotoxins are leached from the straw by the first rains of the growing season and are carried from the straw to the soil where they inhibit species with susceptible seeds or seedlinigs, e.g., Centaqtrea melitensis anid Silybunt marianum.

A study of the mechanism of soil-phosphate uptake in relation to plant species

The concept of plant ‘available’ and ‘unavailable’ soil phosphate has been examined by growing a range of plant species in soils well mixed with carrier free P32.