Using Mediterranean shrubs for the phytoremediation of a soil impacted by pyritic wastes in Southern Spain: a field experiment

Re-vegetation is the main aim of ecological restoration projects, and in Mediterranean environments native plants are desirable to achieve successful restoration. In 1998, the burst of a tailings dam flooded the Guadiamar river valley downstream from Aznalcóllar (Southern Spain) with sludges that contained elevated concentrations of metals and metalloids, polluting soils and waters. A phytoremediation experiment to assess the potential use of native shrub species for the restoration of soils affected by the spillage was performed from 2005 to 2007, with soils divided into two groups: pH < 5 and pH > 5. Four native shrubs (Myrtus communis, Retama sphaerocarpa, Rosmarinus officinalis and Tamarix gallica) were planted and left to grow without intervention. Trace element concentrations in soils and plants, their extractability in soils, transfer factors and plant survival were used to identify the most-interesting species for phytoremediation. Total As was higher in soils with pH < 5. Ammonium sulphate-extractable zinc, copper, cadmium and aluminium concentrations were higher in very-acid soils, but arsenic was extracted more efficiently when soil pH was >5. Unlike As, which was either fixed by Fe oxides or retained as sulphide, the extractable metals showed significant relationships with the corresponding total soil metal concentration and inverse relationships with soil pH. T. gallica, R. officinalis and R. sphaerocarpa survived better in soils with pH > 5, while M. communis had better survival at pH < 5. R. sphaerocarpa showed the highest survival (30%) in all soils. Trace element transfer from soil to harvestable parts was low for all species and elements, and some species may have been able to decrease trace element availability in the soil. Our results suggest that R. sphaerocarpa is an adequate plant species for phytostabilising these soils, although more research is needed to address the self-sustainability of this remediation technique and the associated environmental changes.     

Impact of genetically modified crops on soil- and plant-associated microbial communities

Transgenic or genetically modified plants possess novel genes that impart beneficial characteristics such as herbicide resistance. One of the least understood areas in the environmental risk assessment of genetically modified crops is their impact on soil- and plant-associated microbial communities. The potential for interaction between transgenic plants and plant residues and the soil microbial community is not well understood. The recognition that these interactions could change microbial biodiversity and affect ecosystem functioning has initiated a limited number of studies in the area. At this time, studies have shown the possibility that transgenes can be transferred to native soil microorganisms through horizontal gene transfer, although there is not evidence of this occurring in the soil. Furthermore, novel proteins have been shown to be released from transgenic plants into the soil ecosystem, and their presence can influence the biodiversity of the microbial community by selectively stimulating the growth of organisms that can use them. Microbial diversity can be altered when associated with transgenic plants; however, these effects are both variable and transient. Soil- and plant-associated microbial communities are influenced not only by plant species and transgene insertion but also by environmental factors such as field site and sampling date. Minor alterations in the diversity of the microbial community could affect soil health and ecosystem functioning, and therefore, the impact that plant variety may have on the dynamics of the rhizosphere microbial populations and in turn plant growth and health and ecosystem sustainability, requires further study.     

Insect habitat management in pasture systems

Two important habitat management strategies in pasture systems involve controlled burning and effective grazing manipulation schemes to maintain native climax grassland vegetation These climax grasslands have historically suffered less insect pest pressure than imported systems However, these types of grasslands are difficult to reestablish after relatively severe disruption by man Also, the proper diversity and stability is difficult to capture in developing imported systems. Imported pastures can exhibit substantial yields per land unit but are often composed of vegetation that rapidly mines nutrients stored by the native vegetation, and often need considerable inputs of fossil fuel, manufactured fertilizers and pesticides, because they are or become very susceptible to pestiferous insects. Habitat manipulation efforts can be effective in regulating forage pest populations below economic levels in imported pasture systems Such efforts include: 1) land use (coupled with plant diversity, grazing, and harvest manipulations), 2) sanitation (including controlled burning), 3) planting dates and harvest times (including grazing manipulations), 4) tillage methods, 5) fertilization, 6) trap crops, 7) water management, and 8) fire management for insect pest suppression and augmentation of natural enemies.     

Assessing vulnerability to invasion by nonnative plant species at multiple spatial scales

Basic information on where nonnative plant species have successfully invaded is lacking. We assessed the vulnerability of 22 vegetation types (25 sets of four plots in nine study areas) to nonnative plant invasions in the north–central United States. In general, habitats with high native species richness were more heavily invaded than species-poor habitats, low-elevation areas were more invaded than high-elevation areas, and riparian zones were more invaded than nearby upland sites. For the 100 1000-m² plots (across all vegetation types), 50% of the variation in nonnative species richness was explained by longitude, latitude, native plant species richness, soil total percentage nitrogen, and mean maximum July temperature (n = 100 plots; P < 0.001). At the vegetation-type scale (n = 25 sets of four 1000-m² plots/type), 64% of the variation in nonnative species richness was explained by native plant species richness, elevation, and October to June precipitation (P < 0.001). The foliar cover of nonnative species (log) was strongly positively correlated with the nonnative species richness at the plot scale (r = 0.77, P < 0.001) and vegetation-type scale (r = 0.83, P < 0.001). We concluded that, at the vegetation-type and regional scales in the north–central United States, (1) vegetation types rich in native species are often highly vulnerable to invasion by nonnative plant species; (2) where several nonnative species become established, nonnative species cover can substantially increase; (3) the attributes that maintain high native plant species richness (high light, water, nitrogen, and temperatures) also help maintain nonnative plant species richness; and (4) more care must be taken to preserve native species diversity in highly vulnerable habitats.     

Interactions betweenLythrum salicaria and native organisms: A critical review

Seventy-one articles concerningLythrum salicaria (purple loosestrife), a European herb introduced to North America, were reviewed for evidence of utilization by North American fauna and the effect of loosestrife on native plant species. In contrast to popular claims, 29 species of organisms were found to utilize this plant, and no evidence of species declines due to purple loosestrife were found. Evidence that loosestrife out-competes cattails and other plant species was found to be lacking or contradictory. Thus detailed, quantitative data are needed to understand loosestrife's natural history, population dynamics, and impacts on native ecosystems if we are to effectively manage this plant.     

Revegetation of an abandoned uranium millsite on the Colorado Plateau, Arizona

We attempted to restore native plants on disturbed sites at a former uranium mill on the Colorado Plateau near Tuba City, AZ. Four-wing saltbush [Atriplex canescens (Pursh) Nutt.] was successfully established in compacted caliche soil and in unconsolidated dune soil when transplants were irrigated through the first summer with 20 L/plant/wk. The caliche soil was ripped before planting to improve water-holding capacity. The diploid saltbush variety, angustifolia, had higher survival and growth than the common tetraploid variety, occidentalis, especially on dune soil. The angustifolia variety grew to 0.3 to 0.4 m3 per plant over 3 yr even though irrigation was provided only during the establishment year. By contrast, direct seeding of a variety of native forbs, grasses, and shrubs yielded poor results, despite supplemental irrigation throughout the first summer. In this arid environment (precipitation = 100 to 200 mm/yr), the most effective revegetation strategy is to establish keystone native shrubs, such as four-wing saltbush, using transplants and irrigation during the establishment year, rather than attempting to establish a diverse plant community all at once.     

Conservation of indigenous plants to support community livelihoods: the MGU – Useful Plants Project

Through the MGU – Useful Plants Project (2007–2015) led by the Royal Botanic Gardens Kew, high-quality seed collections and research information have been gathered on useful indigenous plants selected by communities in Botswana, Kenya, Mali, South Africa, and Mexico. Local communities were trained in seed conservation, plant propagation, and planting activities, while revenue generation was promoted directly through the sustainable use of plants and plant products and indirectly through wider environmental and cultural services. The success of this project was determined by its participative approach, involving local communities in plant conservation activities and using plant research to support it. However, the promotion of sustainable use and income generation highlighted issues that confirmed the importance of using a ‘holistic approach’ to address the objective of poverty reduction and contribute to improved livelihoods in the communities.     

Developing Restoration Planting Mixes for Active Ski Slopes: A Multi-Site Reference Community Approach

Downhill ski areas occupy large expanses of mountainous lands where restoration of ecosystem function is of increasing importance and interest. Establishing diverse native plant communities on ski runs should enhance sediment and water retention, wildlife habitat, biodiversity and aesthetics. Because ski slopes are managed for recreation, ski slope revegetation mixes must consist of low-stature or herbaceous plants that can tolerate typical environmental conditions on ski slopes (high elevation, disturbed soils, open, steep slopes). The most appropriate reference communities for selecting ski slope revegetation species are thus successional, or seral plant communities in similar environments (i.e., other ski slopes). Using results from a broad-scale reference community analysis, I evaluated plant communities naturally occurring on ski slopes from 21 active and abandoned ski areas throughout the northern Sierra Nevada to identify native plant species suitable for use in ski slope restoration. I constructed a baseline planting palette of regionally appropriate plant species (for restoration of either newly created or already existing ski runs) that is functionally diverse and is likely to succeed across a broad range of environments. I also identify a more comprehensive list of species for more specialized planting mixes based on site-specific goals and particular environmental settings. Establishing seral plant communities may be an appropriate restoration goal for many other types of managed lands, including roadsides, firebreaks and utility rights-of-way. This study describes an ecological (and potentially cost-effective) approach to developing restoration planting palettes for such managed lands.     

Public Lakes, Private Lakeshore: Modeling Protection of Native Aquatic Plants

Protection of native aquatic plants is an important proenvironmental behavior, because plant loss coupled with nutrient loading can produce changes in lake ecosystems. Removal of aquatic plants by lakeshore property owners is a diffuse behavior that may lead to cumulative impacts on lake ecosystems. This class of behavior is challenging to manage because collective impacts are not obvious to the actors. This paper distinguishes positive and negative beliefs about aquatic plants, in models derived from norm activation theory (Schwartz, Adv Exp Soc Psychol 10:221–279, 1977) and the theory of reasoned action (Fishbein and Ajzen, Belief, attitude, intention, and behavior: an introduction to theory and research, Addison-Wesley, Boston 1975), to examine protection of native aquatic plants by Minnesota lakeshore property owners. We clarify how positive and negative evaluations of native aquatic plants affect protection or removal of these plants. Results are based on a mail survey (n = 3,115). Results suggest that positive evaluations of aquatic plants (i.e., as valuable to lake ecology) may not connect with the global attitudes and behavioral intentions that direct plant protection or removal. Lakeshore property owners’ behavior related to aquatic plants may be driven more by tangible personal benefits derived from accessible, carefully managed lakeshore than intentional action taken to sustain lake ecosystems. The limited connection of positive evaluations of aquatic plants to global attitudes and behavioral intentions may reflect either lack of knowledge of what actions are needed to protect lake health and/or unwillingness to lose perceived benefits derived from lakeshore property.     

Biowaste effects on soil and native plants in a semiarid ecosystem

Many soils of the Mediterranean region with a semiarid climate are subjected to progressive degradation as a result of water erosion. Biosolids and municipal solid wastes (MSW) were surface-applied once at three rates (40, 80, and 120 Mg ha(-1)) to different plots in a degraded semiarid ecosystem. The study was conducted to determine the effects of such applications on soil chemical properties and native vegetation over a three-year period. Soil N, P, and K initially increased with increasing biowaste application rates, but then decreased over time. Levels of Zn and Cu were higher in MSW than biosolid-treated plots, and increased in both years after application. Concentrations of soil Cd, Pb, Ni, and Cr did not change as a result of biowaste amendment in the study period. The growth of native plants was enhanced by the addition of biowastes. Total plant canopy and plant biomass increased significantly and remained higher in all treatments than in the control plot over the three-year period. The species richness of native plants decreased with increasing biowaste rates. Differences in the development of native plant communities between treatments were observed, and were more remarkable three years after biowaste application. Tissue N, P, K, Zn, and Cu levels increased with the biowaste application rate, but concentrations of tissue Pb, Cd, Ni, and Cr did not increase significantly. Biowastes applied at the rate of 80 Mg ha(-1) gave rise to the most favorable soil and native vegetation results while avoiding environmental risks.     

The US freshwater supply shortage: Experiences with desalination as part of the solution

Parts of the USA are facing impending shortages of freshwater. One proposed solution is the construction of desalination plants to turn seawater into freshwater. Although seawater desalination plants are widely used in the Middle East, especially Saudi Arabia, there are few desalination plants in the USA. In 2003, Tampa Bay Water built the largest desalination plant in North America. Persistent operating problems and escalating costs have caused the utility to re-evaluate its reliance on the seawater desalination plant as part of a long-term regional water supply strategy. In addition, environmental effects of the plant are uncertain. Advances in reverse osmosis technology have significantly reduced desalination costs. However, desalination of seawater is still more expensive than other freshwater supply sources and demand management measures. With time and research, seawater desalination may prove to be a sustainable, cost-effective source of new freshwater supplies, especially if plants are coupled with renewable energy sources. Until then, the development of small-scale groundwater desalination plants, the re-use of water, water conservation, and a more efficient allocation of water through higher prices and rising block rates will be important strategies in meeting growing water demand. Moreover, it is important to improve the coordination between water supply planning and land use planning as populations continue to increase.     

Honeybees Increase Fruit Set in Native Plant Species Important for Wildlife Conservation

Honeybee colonies are declining in some parts of the world. This may have important consequences for the pollination of crops and native plant species. In Spain, as in other parts of Europe, land abandonment has led to a decrease in the number of non professional beekeepers, which aggravates the problem of honeybee decline as a result of bee diseases In this study, we investigated the effects of honeybees on the pollination of three native plant species in northern Spain, namely wildcherry Prunus avium L., hawthorn Crataegus monogyna Jacq., and bilberry Vaccinium myrtillus L. We quantified fruit set of individuals from the target species along transects established from an apiary outwards. Half the samples were bagged in a nylon mesh to avoid insect pollination. Mixed-effects models were used to test the effect of distance to the apiary on fruit set in non-bagged samples. The results showed a negative significant effect of distance from the apiary on fruit set for hawthorn and bilberry, but no significant effects were detected for wildcherry. This suggests that the use of honeybees under traditional farming practices might be a good instrument to increase fruit production of some native plants. This may have important consequences for wildlife conservation, since fruits, and bilberries in particular, constitute an important feeding resource for endangered species, such as the brown bear Ursus arctos L. or the capercaillie Tetrao urogallus cantabricus L.     

Grassland Plant Composition Alters Vehicular Disturbance Effects in Kansas,USA

Many “natural” areas are exposed to military or recreational off-road vehicles. The interactive effects of different types of vehicular disturbance on vegetation have rarely been examined, and it has been proposed that some vegetation types are less susceptible to vehicular disturbance than others. At Fort Riley, Kansas, we experimentally tested how different plant community types changed after disturbance from an M1A1 Abrams tank driven at different speeds and turning angles during different seasons. The greatest vegetation change was observed because of driving in the spring in wet soils and the interaction of turning while driving fast (vegetation change was measured with Bray-Curtis dissimilarity). We found that less vegetation change occurred in communities with high amounts of native prairie vegetation than in communities with high amounts of introduced C₃ grasses, which is the first experimental evidence we are aware of that suggests plant communities dominated by introduced C₃ grasses changed more because of vehicular disturbance than communities dominated by native prairie grasses. We also found that vegetation changed linearly with vehicular disturbance intensity, suggesting that at least initially there was no catastrophic shift in vegetation beyond a certain disturbance intensity threshold. Overall, the intensity of vehicular disturbance appeared to play the greatest role in vegetation change, but the plant community type also played a strong role and this should be considered in land use planning. The reasons for greater vegetation change in introduced C₃ grass dominated areas deserve further study.     

Responses of Two Invasive Plants Under Various Microclimate Conditions in the Seoul Metropolitan Region

The possible consequences of global warming on plant communities and ecosystems have wide-ranging ramifications. We examined how environmental change affects plant growth as a function of the variations in the microclimate along an urban-suburban climate gradient for two allergy-inducing, invasive plants, Humulus japonicus and Ambrosia artemisiifolia var. elatior. The environmental factors and plant growth responses were measured at two urban sites (Gangbuk and Seongbuk) and two suburban sites (Goyang and Incheon) around Seoul, South Korea. The mean temperatures and CO(2) concentrations differed significantly between the urban (14.8 °C and 439 ppm CO(2)) and suburban (13.0 °C and 427 ppm CO(2)) sites. The soil moisture and nitrogen contents of the suburban sites were higher than those at the urban sites, especially for the Goyang site. The two invasive plants showed significantly higher biomasses and nitrogen contents at the two urban sites. We conducted experiments in a greenhouse to confirm the responses of the plants to increased temperatures, and we found consistently higher growth rates under conditions of higher temperatures. Because we controlled the other factors, the better performance of the two invasive plants appears to be primarily attributable to their responses to temperature. Our study demonstrates that even small temperature changes in the environment can confer significant competitive advantages to invasive species. As habitats become urbanized and warmer, these invasive plants should be able to displace native species, which will adversely affect people living in these areas.     

The possibility of in situ heavy metal decontamination of polluted soils using crops of metal-accumulating plants

The decontamination of soils and wastes polluted with heavy metals presents one of the most intractable problems for soil clean-up. Present technology relies upon metal extraction or immobilization processes, both of which are expensive and which remove all biological activity in the soil during decontamination. They may only be appropriate for small areas of valuable redevelopment land. In this paper the use of metal-accumulating plants is explored for the removal of metals from superficially-contaminated soils such as those resulting from the long-term application to land of metal-contaminated sewage sludges. Green remediation employs plants native to metalliferous soils with a capacity to bioaccumulate metals such as zinc and nickel to concentrations greater than 2% in the aerial plant dry matter (hyperaccumulators). Growing such plants under intensive crop conditions and harvesting the dry matter is proposed as a possible method of metal removal and for ‘polishing’ contaminated agricultural soils down to metal concentrations below statutory limits. Not only are the biological activity and physical structure of soils maintained but the technique is potentially cheap, visually unobtrusive and offers the possibility of biorecovery of metals. The limitations of the process are reviewed and the future requirements for the development of efficient phytoremediators are outlined.     

Energy production and sustainability: A study of Belo Monte hydroelectric power plant

The increase in energy demand due to economic and population growth necessitates the expansion of the Brazilian energy supply. Hydropower energy, a renewable energy source, arguably clean, presents an energy solution for many countries such as Brazil, with large hydric reservoirs, which help them reduce energy dependence on fossil and imported fuel sources. However, it must be emphasized that without careful planning, the creation of hydropower plants will cause severe social and environmental damage due to the large areas that need to be flooded for the implementation of these plants. The installation of hydropower plants floods vast forest areas, causing loss of biodiversity, displacement of native Brazilian people and riverside populations, and changes to the water acid levels and the natural course of rivers. To mitigate these effects, authorities must first conduct a study on installation possibilities and potential socio‐environmental consequences, to be interpreted and used by the agents involved. Aiming to analyze the social‐environmental impacts of the hydropower plants, this research seeks to investigate the capacity of mitigation of the negative effects of the implementation of the hydropower plants, specifically with regard to the Belo Monte plant, Brazil.     

Measuring Plant Diversity in the Tall Threetip Sagebrush Steppe: Influence of Previous Grazing Management Practices

In July 2000, a 490-ha wildfire burned a portion of a long-term grazing study that had been established in 1924 at the US Sheep Experiment Station north of Dubois, Idaho, USA. Earlier vegetation measurements in this tall threetip sagebrush (Artemisia tripartita spp. tripartita) bunchgrass plant community documented significant changes in vegetation due to grazing and the timing of grazing by sheep. A study was initiated in May 2001 using 12 multiscale modified Whittaker plots to determine the consequences of previous grazing practices on postfire vegetation composition. Because there was only one wildfire and it did not burn all of the original plots, the treatments are not replicated in time or space. We reduce the potential effects of psuedoreplication by confining our discussion to the sample area only. There were a total of 84 species in the sampled areas with 69 in the spring-grazed area and 70 each in the fall- and ungrazed areas. Vegetation within plots was equally rich and even with similar numbers of abundant species. The spring-grazed plots, however, had half as much plant cover as the fall- and ungrazed plots and the spring-grazed plots had the largest proportion of plant cover composed of introduced (27%) and annual (34%) plants. The fall-grazed plots had the highest proportion of native perennial grasses (43%) and the lowest proportion of native annual forbs (1%). The ungrazed plots had the lowest proportion of introduced plants (4%) and the highest proportion of native perennial forbs (66%). The vegetation of spring-grazed plots is in a degraded condition for the environment and further degradation may continue, with or without continued grazing or some other disturbance. If ecosystem condition was based solely on plant diversity and only a count of species numbers was used to determine plant diversity, this research would have falsely concluded that grazing and timing of grazing did not impact the condition of the ecosystem.     

Survival,reproduction, and recruitment of woody plants after 14 years on a reforested landfill

With the advent of modern sanitary landfill closure techniques, the opportunity exists for transforming municipal landfills into urban woodlands. While costs of fullscale reforestation are generally prohibitive, a modest planting of clusters of trees and shrubs could initiate or accelerate population expansions and natural plant succession from open field to diverse forest. However, among woody species that have been screened for use on landfills, these ecological potentials have not yet been investigated. We examined a 14-yr-old landfill plantation in New Jersey, USA, established to test tolerance of 19 species of trees and shrubs to landfill environments. We measured survivorship, reproduction, and recruitment within and around the experimental installation. Half of the original 190 plants were present, although survival and growth rates varied widely among species. An additional 752 trees and shrubs had colonized the plantation and its perimeter, as well as 2955 stems of vines. However, the great majority (>95%) of woody plants that had colonized were not progeny of the planted cohort, but instead belonged to 18 invading species, mostly native, bird-dispersed, and associated with intermediate stages of secondary plant succession. Based on this evidence, we recommend that several ecological criteria be applied to choices of woody species for the restoration of municipal landfills and similar degraded sites, in order to maximize rapid and economical establishment of diverse, productive woodlands.     

Removing Chinese Privet (Ligustrum sinense Lour.) and Establishing Native Plants in a Flooded Riparian Corridor in North‐Central Texas,USA

The objectives of this study were to evaluate the allelopathic effects of Chinese privet (Ligustrum sinense Lour.) extract on native seeds and cuttings and to assess the survivability of native plants in a flooded riparian corridor. Field sites occupied the Trinity River floodplain in southeast Dallas County, Texas. Eight native species were evaluated. They were soapberry, red mulberry, persimmon, elderberry, beautyberry, coralberry, mustang grape, and heartleaf peppervine. From this study, we concluded that:

• Truncating privet at ground level and applying equal parts of glyphosate and water to the stump effectively kills the plant;
• Once removed, privet does not curtail establishment of native plants;
• A 60‐day (d) flood killed most plants, with red mulberry being the most resilient;
• A 1% leaf and berry extract from privet significantly reduced soapberry seed germination; and
• A 1% extract from various parts of privet did not significantly affect root growth from cuttings.

     

Beyond “Second Animals”: Making Sense of Plant Ethics

Concern for what we do to plants is pivotal for the field of environmental ethics but has scarcely been voiced. This paper examines how plant ethics first emerged from the development of plant science and yet also hit theoretical barriers in that domain. It elaborates on a case study prompted by a legal article on “the dignity of creatures” in the Swiss Constitution. Interestingly, the issue of plant dignity was interpreted as a personification or rather an “animalization of plants.” This sense of irony makes sense when one realizes that on scientific grounds the plant is a “second animal,” i.e., it differs from the animal in degree of life or some ethically-relevant criterion but not in nature. From the point of view of ethics however, plants should be defended for what they are by nature and not by comparison to external references: the ethical standing of plants cannot be indexed to animals. It is thus reckoned that to circumvent this odd fetishism, the plant ethics can only be adequately addressed by changing the theory of plant science. Common sense tells us this: plants and animals belong to radically different fields of perception and experience, a difference that is commonly captured by the notion of kingdom. In this paper we remind the ethical conversation that plants are actually incommensurable with animals because they are unsplit beings (having neither inside nor outside), i.e., they live as “non-topos” in an undivided, unlimited, non-centered state of being. It is concluded that the unique ontology of plants can only be addressed through a major change from object-thinking to process-thinking and a move from ego-centric to “peri-ego” ethics.