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Invasive species is a phrase with several definitions. The first definition expresses the phrase in terms of non-indigenous species (e.g., plants or animals) that adversely affect the habitats they invade economically, environmentally or ecologically. It has been used in this sense by government organizations as well as conservation groups such as the IUCN. The second definition broadens the boundaries to include both native and non-native species that heavily colonize a particular habitat. The third definition is an expansion of the first and defines an invasive species as a widespread non-indigenous species. This last definition is arguably too broad as not all non-indigenous species necessarily have an adverse effect on their adopted environment. An example of this broader use would include the claim that the common goldfish (Carassius auratus) is invasive. Although it is common outside its range globally, it almost never appears in harmful densities. This new book presents important recent research in the field from around the world.

Short Communication 1 - Ailanthus (Ailanthus altissima) is an exotic invasive tree species that is becoming an increasingly common threat to native forest communities in the eastern United States. The species spreads aggressively by both seed and sprouts and produces allelopathic chemicals that may enable its spread. The authors tested two chemical control methods on Ailanthus (cut stump application with an aqueous 50% formulation of triclopyr vs. basal bark application using a 20% ester formulation of triclopyr). Each application was applied to replicated groups of trees in the spring following budbreak or in the fall before leaf fall. The cut stump application resulted in 100% control of Ailanthus (no resprouting) in both spring and fall, while the basal bark application was >90% effective (complete crown mortality). Spring applications were slightly more effective than fall applications for basal bark treatments. While chemical control appears to be an effective method for killing Ailanthus trees, abundant germination from the soil seed bank surrounding controlled trees will require long-term control efforts.

Short Communication 2 - Invasion of the Mediterranean Sea by alien species is getting increasingly prominent every day. These alien species are probably transported in with ballast waters or by attaching themselves onto vessels. Furthermore, many species have been brought into the Mediterranean for aquaculture purposes or inadvertantly introduced from public aquariums. But, most of the alien taxa recorded in the Mediterranean are originated from Indo-Pacific, indicating that the Suez Canal is considered to be the major vector in introducing alien species into the Levantine Basin. More than five hundered alien species have been recorded so far and each year new arrivals are reported (Galil, 2008). Alien invasion is considered to be a major problem worldwide, especially if the native coastal ecosystems are polluted and disturbed by the anthropogenic activities, such as observed in the Mediterranean. The aliens can deplete food sources, change the habitat structure and environmental conditions, in which the native species cannot survive. However, the aliens with an economical value constitute an important portion of the fisheries in the Eastern Mediterranean.

Short Communication 3 - Invasive alien species can have a detrimental economic impact on human enterprises such as agriculture, grazing, forestry and tourist activities. Invasive species have been identified as one the major threats to ecosystems and biodiversity, as well as human well-being. The main objective of our study is to determine whether regeneration of the exotic Pinus pinea is able to compete with the regeneration of the native P. canariensis. The study area is located in the Natural Park of Tamadaba, 1400 m asl., in the NW of Gran Canaria island (Canary Islands). Stems and regeneration of P. canariensis and P. pinea were mapped in five randomly selected plots where both species were planted together around 45 years ago. Densities and basal areas of both species were also recorded. A monitoring of the survivorship of seedlings of both species was carried out during two years. A group of individuals of P. canariensis were excluded from grazing to determine the effect of grazing in the survivorship of the species.

Although the dispersal ability of P. canariensis was more effective, once the individuals of P. canariensis and P. pinea had been established, there was not difference in survivorship. Also, we did not find differences in survivorship for individuals excluded vs. non-excluded from grazing.

Despite the stability of the exotic species, this can change with the introduction of a dispersal vector of the seeds, a squirrel, Atlantoxerus getulus, which was introduced in Fuerteventura (the closest island to Gran Canaria) with an estimated population of 1 million of individuals. Gran Canaria is also suitable for the establishment of this exotic disperser of

Pinus pinea.

Applying a precautionary principle, control of the species will be recommended in order to avoid future problems of invasiveness of P. pinea, as has been found after the introduction of the dispersal vector with another squirrel in South Africa.

Chapter 1 - Spartina alterniflora Loisel., a native to the Atlantic and Gulf coasts of North America, had been deliberately introduced into many countries for the control of coastal erosion and land claim. But now, the species has extensively dispersed, and even broken out in some non-native habitats. Due to Allee effect, inbreeding depression, rapid adaptation and evolution occur in the process of invasion and natural dispersal of Spartina alterniflora, it has become a model plant for studying biological invasion from both ecological and genetic perspectives. The previous researches showed that powerful ability of hybridization and introgression has been a genetic basic, superior reproductive capability has been the sources and strong ability of anti-stress and adaptability has been an ecological and physiologic basic for S. alterniflora invasion and expansion, respectively. In most invasive habitats, the expansion of S. alterniflora, based on intentionally transplants, indicated the mode of point dispersal. The episodic and continuous dispersal pattern of seeds has been playing an important role for maintain, recruitment and outbreak of S. alterniflora population. Meanwhile, consecutive expansion of S. alterniflora populations was ensured by the trait of potently clonal growth. Therefore, prevention of seed production in all designated areas is required to help contain this species and prevent its further spread. At the same time, although it has been proven to be very difficult, expensive and even impossible to eradicate the species, the integrated strategies with exploring the economical value and other restraining growth of S. alterniflora methods should be adopt to manage and alleviate the negative impacts the biological invasion.

Chapter 2 - Ascidians are common members of benthic marine communities. Due to their strong competitive abilities and their simple trophic requirements ascidians are highly invasive. Because they only need a hard surface for attachment and abundant particulate food to flourish, ascidians are easily introduced to new locations and can readily persist once established. Invasive ascidians often have considerable impact on invaded habitats. Not only can they affect benthic communities, but they also cause major problems for humans by overgrowing aquaculture equipment and organisms and by heavily fouling ships and man-made structures. Because ascidians have traditionally been of little direct economic value, much less is known about their biology than for other marine taxa (e.g., crustaceans, bivalves and teleosts). However, this is starting to change. Due to the impact invasive ascidians have had throughout the world in the past 25-30 years, ascidians have become the focus of significant scientific attention. Over the last few years a great deal of work has been conducted to learn more about ascidian ecology, to assess the impact of invasive ascidians on invaded systems, to prevent the spread of ascidians and to control them once they have become established in new areas. This review synthesizes the latest research on invasive ascidians and highlights areas for further study.

Chapter 3 - Infestations of wildlands by invasive plants can reduce resource productivity, decrease biodiversity, displace native vegetation, and alter ecosystem processes and functions. The traditional reactive strategy of controlling established invasive plant infestations followed by restoration of the native plant community has proven to be largely ineffective at reducing the spread and negative impacts of invasive plants. This approach often fails in its attempt to restore native plant communities and is too costly to apply at the scale required to have substantial effects. While large amounts of resources are intensively spent on efforts to restore a few infested wildlands, invasive plants continue to spread via emerging populations and expanding established infestations. A proactive approach with the objective of preventing new infestations and limiting the expansion of existing infestations is a more effective and efficient strategy for managing invasive plants in wildlands because it precludes the need for restoration. However, relatively few resources are being directed towards preventing the spread of invasive species. Successful strategies to prevent infestations of invasive plants should focus on: 1) limiting the spatial dispersal of propagules (i.e., reducing propagule pressure), 2) maintaining or increasing the ability of wildland plant communities to resist invasion (i.e., biotic resistance), and 3) systematically searching for and eradicating new infestations. Propagule pressure and biotic resistance interact to determine wildland plant community invasibility. At low biotic resistance even a few propagules may result in successful invasion; however, as biotic resistance increases, greater propagule pressure is required for invasion. Thus, efforts aimed at decreasing invasive plant propagule pressure and increasing biotic resistance can greatly reduce new infestations. Systematically searching for and eradicating new infestations is also a critical element of a successful prevention strategy, because uncontrollable events may still lead to new infestations. Successful management of invasive plants in wildlands will require more efforts and resources directed at prevention. This task can be facilitated by more research developing and improving prevention strategies and demonstrating the effectiveness of proactive management.

Chapter 4 - Resource managers can benefit from improved methods for identifying invasive plant species. The utilization of hyperspectral remote sensing as a tool for species-level mapping has been increasing and techniques need to be explored for identifying species of interest. The overarching objective of this paper was to investigate three distinct processing methodologies (i.e., Derivatives, Continuum Removal, and Shape Filter) to explore their potential for delineating wetland invasive plant species within the spectral domain of typical airborne hyperspectral sensors. Field-level hyperspectral data (350-2500nm) were collected for twenty-two wetland plant species in a wetland located in the lower Muskegon River watershed in Michigan, USA. Generally, continuum removed spectra were more similar than raw reflectance for the invasive species of interest according to the Jeffries-Matusita distance measure. Second-derivative analysis showed that the wavelength locations of absorption and reflectance features were consistent for all species and emphasized the NIR region for separation. The shape-filter was useful as a method to identify invasive species and showed that useful wavelength regions can vary depending on the species of interest and approach utilized. Using the shape-filter, Lythrum salicaria, Phragmites australis, and Typha latifolia possessed maximum separation (distinguished from other species) at the red edge (700nm) and water absorption region (1350nm), the near-infrared down slope (1000 and 1100nm), and the visible/chlorophyll absorption region (500nm) and red edge (650nm), respectively.

Chapter 5 - The authors have examined impacts of alien invasive plants on soil chemical properties, primary productivity and nutrient cycling in the plant / soil system. Specifically, they tested if impacts follow a general pattern across sites and species or, alternatively, if they are entirely idiosyncratic. The study first focused on 36 sites in Belgium invaded by one of the 7 most invasive plant species in NW Europe (Solidago gigantea, Fallopia japonica, Senecio inaequidens, Heracleum mantegazzianum, Impatiens glandulifera, Prunus serotina and Rosa rugosa). The authors compared invaded to adjacent uninvaded plots for selected parameters. Primary productivity and nutrient uptake were always higher in invaded stands compared to uninvaded plots. Magnitude and direction of impacts on soil chemical properties strongly varied depending on site. However, impacts followed a general pattern, being predictable from soil chemical properties prior to invasion. Thus, in sites with low soil nutrient contents, invasion tended to increase available nutrient pools in the topsoil while the opposite trend was observed in soils initially rich in nutrients. This suggests that exotic plant invasion could lead to the homogenization of soil nutrient concentrations across invaded landscapes.

Later on, the authors selected two species (Solidago gigantea and Fallopia japonica) to study in details the mechanisms of the impacts on soil properties.

In soil invaded by S. gigantea, soil phosphorus availability was increased. Higher turnover rates of phosphorus in belowground organs and mobilization of soil sparingly soluble P forms through rhizosphere acidification may be involved in the observed differences in soil P status between invaded and uninvaded plots.

In grassland invaded by Fallopia japonica, the carbon and nitrogen cycling were deeply modified. Due to its higher lignin/N ratio compared to resident vegetation, Fallopia litter decomposed much more slowly and immobilized a large amount of inorganic N, reducing the availability of this element in soil. On the other hand, the internal cycling of N in Fallopia was found exceptionally efficient. Indeed, about 80 % of the N present in aboveground biomass in summer is translocated to the rhizomes before leaves abscission. This process makes the plant relatively independent from soil N mineralization and possibly contributes to the high productivity and invasive success of the species. In addition, F. japonica also impacted soil fauna communities. The density of invertebrates under the canopy of F. japonica was reduced and the composition of the community shifted from a typical grassland community to typical forest groups. These changes may be explained by a reduction of food diversity, a change in soil microclimate and in organic matter quality.

Chapter 6 - Increased input of nitrate and ammonium to ecosystems is mainly responsible for eutrophication, which is related to biological invasion of aquatic exotic plant species. In order to determine the effects of different nitrogen forms on its growth and physiological responses in eutrophic water, Eichhornia crassipes plants were grown for 28 days in 5mmol/L nitrogen-contained nutrient solutions varying in NH4+:NO3- ratio (100:0, 75:25, 50:50, 25:75, 0:100) in laboratory. The results showed that the NH4+:NO3- ratio of nutrient solution dramatically affected the plant performance of E. crassipes including relative growth rate, number of generated ramets, nitrate concentration in root and leaf. Furthermore, nitrate reductase activity increased with reduction of NH4+: NO3- ratio in culture solution demonstrating preferences of N sources as nitrate in E. crassipes. However, ammonium concentration and glutamine synthetase activity in leaf did not significantly change, and those in root significantly increased when proportion of NH4+ in nutrient solution increased indicating that E. crassipes plants are able to resist ammonium toxicity by regulation of ammonium transport and assimilation. In a word, the results suggested that establishment and expansion of E. crassipes was not likely to be limited by nitrogen forms.

Chapter 7 - Warm-season perennial legumes, as a plant functional group, hold considerable promise for use as forage plants in the warm, humid southeastern U.S., where infertile soils and low-protein forage grasses are common. This plant group is large with tremendous ranges in growth forms and propagation methods. Despite the overall promise, only a few species have been, are currently, or even appear to be potentially useful forage plants. The few species of this group which are widely adapted across the Southeast are also considered, at least by some, to be invasive. Included are a vine (kudzu, Pueraria montana var. lobata), a tree (mimosa, Albizia julibrissin), and a herb (sericea lespedeza, Lespedeza cuneata). Rather casual observation can quickly provide evidence of the invasiveness of kudzu. Determination of the invasiveness of sericea lespedeza depends to some extent on the evidence assessed. With mimosa, the question may be about forage value rather than invasiveness. Most of the seemingly unstoppable spread of kudzu is from rapid vegetative extension, while seed provide the means for increase in range of the other two. Simple single-application treatments of various defoliation procedures or even the most effective herbicide have either had minimal or rather temporary effects on kudzu and sericea lespedeza. Long-term strategies, rather than single control treatments, are required for success. Knowledge of basic mechanisms of plant dispersal and ecosystem susceptibility to invasion by sericea lespedeza are needed to allow appropriate decisions about control and prevention of problem populations of this species. Developing technology holds promise for future use of mimosa as an intensively managed forage legume despite invasiveness. The greatest potential forage use of introduced, perennial, warm-season legumes in the southeastern U.S. in general may well be through the use of grazing livestock as part of carefully planned control strategies.

Chapter 8 - Making simple improvements on traditional fishing gear and methods can be applied to develop effective eradicating tools that can be integrated with other strategies used to combat invasive aquatic species. Swimming crabs are the target choice; they travel widely by swimming, attached to the hulls of ships or as larvae suspended in ballast water. They represent a valuable fisheries resource and are consumed as food. They are however also carriers of pathogens that may damage fisheries and aquaculture industries, which results in the need of effective eradication methods.

Traps make good eradicating gear because they are light, inexpensive, small, easily stacked onboard, keep the catch alive, and permit the release of non-target organisms undamaged. They are passive gear, so the target organism has to be lured into the traps with the promise of food, shelter, company or even a mating partner.

Improving luring methods, such as common baits or pheromone emitting decoys, is just as important as research on new trap design for increasing the catch. Determining the taste preferences of the target crab, and making bait combinations of fish plus sugarcane have demonstrated a synergistic effect that doubled the catch. Alternative bait made from fish mince inside teabags was as effective as ordinary bait, and allowed enrichment of the bait with attractants and the use of fish byproducts as raw material, which reduces cost and conserves valuable food resources. Pheromones offer attracting potential, have been found in swimming crabs and are emitted by the live decoys employed in their trap fishery. This fishing method eliminates the non-target catch by attracting only crab conspecifics. Specially designed traps containing live decoy crabs were more effective than baited traps, and eliminated unwanted organisms that feed on bait.

When designing eradicating gear, the quantity of the catch is more important than its size or quality; consequently, traps must be fitted with smaller meshed netting to additionally retain juvenile crabs. Observations on crab behavior around different trap designs showed that they search larger areas around traps with oval bases than those with rectangular ones, and this gives them more access to the trap entrances. Open funnel entrances allowed entry of most crabs contacting the traps and were superior to tight slit entrances because being open they permitted escape, thus reducing the non-target catch and the negative impact that lost gear causes on the aquatic resources by ghost fishing.

Chapter 9 - The state of Florida has among the two worst invasive species problems in the United States. Besides the sheer numbers of established exotic species in Florida, many present novel difficulties for management, or have other characteristics making effective management extremely challenging. Moreover, initiation of management action requires more than recognition by experts that a potentially harmful species has become established. It also requires the political will along with concomitant resources and appropriate personnel to develop effective methods and apply them. The authors illustrate various aspects of the situation in Florida with examples of invasive vertebrates, the problems they pose(d), and management approaches to the problems.

The problems described include long-established widespread and destructive species requiring intensive localized management (feral swine, feral cats); recently established species with potentially severe repercussions, but no broad operational removal programs yet in place (Nile monitor lizards, Burmese pythons), highly prolific mammals that could rapidly invade wide areas without containment/eradication (Gambian giant pouched rats, black-tailed jackrabbits); recently established, potentially destructive birds that might still be eradicated (purple swamp hens); species where sufficient public outcry resulted in control programs (black spiny-tailed iguanas); and rapidly expanding aggressive species for which no practical management actions are available (northern curlytail lizard). A species subset is used here to exemplify in more detail the array of invasive vertebrate species situations in Florida, including routes of introduction, impacts, surrounding politics, and management actions. These examples not only demonstrate the breadth of the terrestrial invasive vertebrate problems in the state, but they also show the diversity in resolve and response among the many species and the motivating factors.

In: Invasive Species: Detection, Impact and Control ISBN 978-1-60692-252-1

Editors: C.P. Wilcox and R.B. Turpin © 2009 Nova Science Publishers, Inc.

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