The occurrence of alien plant species in field margins in Finland

The results suggest that alien plant species comprise an important part of the biodiversity of Finnish field margins and semi-natural agricultural habitats. The role of field margins as dispersal corridors for invasive alien plants is limited for certain species

Emerging Urban Forests: Opportunities for Promoting the Wild Side of the Urban Green Infrastructure

Many cities aim to increase urban forest cover to benefit residents through the provision of ecosystem services and to promote biodiversity. As a complement to traditional forest plantings, we address opportunities associated with “emerging urban forests” (i.e., spontaneously developing forests in cities) for urban biodiversity conservation. We quantified the area of successional forests and analyzed the species richness of native and alien plants and of invertebrates (carabid beetles, spiders) in emerging forests dominated by alien or native trees, including Robinia pseudoacacia, Acer platanoides, and Betula pendula. Emerging urban forests were revealed as shared habitats of native and alien species. Native species richness was not profoundly affected by the alien (co-)dominance of the canopy. Instead, native and alien plant species richnesses were positively related. Numbers of endangered plants and invertebrates did not differ between native- and alien-dominated forest patches. Patterns of tree regeneration indicate different successional trajectories for novel forest types. We conclude that these forests (i) provide habitats for native and alien species, including some endangered species, (ii) allow city dwellers to experience wild urban nature, and (iii) support arguments for adapting forests to dynamic urban environments. Integrating emerging urban forests into the urban green infrastructure is a promising pathway to sustainable cities and can complement traditional restoration or greening approaches.BMBF, 01LC1501, Bridging in Biodiversity Science (BIBS

Alien plants

The catalogue accompanying this paper includes all those members of the Tasmanian Flora which come under Hewett C. Watson's designation of Aliens. This is a happily conceived title, first instituted by that veteran botanist; and it was intended by him to embrace such species as have been introduced either by accident or design, and which have maintained their ground more or less firmly in their adopted country. I also include a few plants which, in Mr. Watson's more extended vocabulary, would probably be named by him waifs, strays, and casuals; but the number of these is so small that I have thought it better to bring them all under the general designation of Aliens

Frequent burning promotes invasions of alien plants into a mesic African savanna

Fire is both inevitable and necessary for maintaining the structure and functioning of mesic savannas. Without disturbances such as fire and herbivory, tree cover can increase at the expense of grass cover and over time dominate mesic savannas. Consequently, repeated burning is widely used to suppress tree recruitment and control bush encroachment. However, the effect of regular burning on invasion by alien plant species is little understood. Here, vegetation data from a long-term fire experiment, which began in 1953 in a mesic Zimbabwean savanna, were used to test whether the frequency of burning promoted alien plant invasion. The fire treatments consisted of late season fires, lit at 1-, 2-, 3-, and 4-year intervals, and these regularly burnt plots were compared with unburnt plots. Results show that over half a century of frequent burning promoted the invasion by alien plants relative to areas where fire was excluded. More alien plant species became established in plots that had a higher frequency of burning. The proportion of alien species in the species assemblage was highest in the annually burnt plots followed by plots burnt biennially. Alien plant invasion was lowest in plots protected from fire but did not differ significantly between plots burnt triennially and quadrennially. Further, the abundance of five alien forbs increased significantly as the interval (in years) between fires became shorter. On average, the density of these alien forbs in annually burnt plots was at least ten times as high as the density of unburnt plots. Plant diversity was also altered by long-term burning. Total plant species richness was significantly lower in the unburnt plots compared to regularly burnt plots. These findings suggest that frequent burning of mesic savannas enhances invasion by alien plants, with short intervals between fires favouring alien forbs. Therefore, reducing the frequency of burning may be a key to minimising the risk of alien plant spread into mesic savannas, which is important because invasive plants pose a threat to native biodiversity and may alter savanna functioning

Integrated control of invasive alien plants in terrestrial ecosystems

Effective management of invading alien plants in natural and semi-natural systems is imperative if we are to prevent enormous impacts. An integrated approach involving the combined use of a range of methods is usually necessary to control invasive alien plants effectively. The various methods that are available are usually classified as: mechanical methods (felling, removing of invading alien plants, often in conjunction with burning); chemical methods (using environmentally safe herbicides); and biological control (using species-specific insects and diseases from the alien plant's country of origin). Approaches available for integrated control depend on the species under consideration (features of individual species and the number and identity of species that occur together), features of the invaded systems, the availability of resources and other factors. Mechanical and chemical control are short-term activities, whereas rigorous and disciplined follow-up and rehabilitation are necessary in the medium term. Biological control can provide effective control in the short and medium term in some cases, and it is often the only really sustainable solution in the longer term. We suggest that the biological attributes of plants represent a stable set of attributes, which enable managers to devise control approaches, but that such approaches are likely to be upset by stochastic events such as fires, floods or budget cuts. While an approach of adaptive management, based on trial, error and continual improvement is a logical way in which to progress, the advent of powerful computer simulation modelling technologies will allow managers to do hundreds of 'trial and error' runs in order to explore the consequences of certain courses of action. This should represent an improvement on the current state of affairs, and should allow for better decision-making. We present a series of simulations to illustrate this point.Resource /Energy Economics and Policy,

Cytological and molecular characterization of wheat lines with Thinopyrum intermedium chromosome additions, substitutions and translocations resistant to barley yellow dwarf virus

Barley yellow dwarf virus (BYDV) is the most serious viral disease affecting wheat and genes for BYDV resistance have not been found in wheat. BYDV-resistant alien addition and alien substitution lines produced from a wheat × Thinopyrum intermedium (species of Agropyron complex) cross were characterized. Chromosome pairing in the hybrids between two substitution lines showed that they had the same Th. intermedium chromosome. Likewise, two addition lines involved the same alien chromosome. In situ hybridization of chromosomes, confirmed that line P29 is a disomic substitution line. Double monosomic seeds and self-pollinated seeds from monosomic addition plants were irradiated to induce translocations between wheat and Th. intermedium chromosomes. Putative translocations were selected on the basis of BYDV resistance and studied by chromosome analysis, Southern hybridization using Thinopyrum specific probe and RFLP markers. A BYDV-resistant translocation was identified

Hydrological impacts of invasive alien plants

It is now well recognised that invasive alien species, particularly tree species, often have much increased water usage compared with native vegetation. Perhaps less well understood are the reasons for this increased water use and whether such increases should be expected from all species of invading alien trees under all environmental conditions. This paper examines the reasons for increased water use from trees as compared with short crops. From a knowledge of these reasons and a knowledge of the limiting processes (the Limits Concept) governing alien tree and native tree and short crop water use, (derived from case studies in India and RSA), we suggest that it is now possible to assess under what conditions high water use by aliens may occur. Inverse solutions based on knowledge of growth rates are also suggested as another approach for assessing alien and native tree water use under water limited conditions. We conclude that in dry climates the greatest increase in water use from aliens, in both absolute and percentage terms, may occur in water limited rather than riparian (water unlimited) conditions. Hydrological models which can predict the spatially distributed increase in water use by aliens within catchments, coupled with ecological models which can predict controlled and uncontrolled invasion, can assist the evaluation and design of improved cost-effective eradication programmes. Such coupled models, linked with an economic evaluation component, should indicate in what circumstances the value of the extra streamflow released may alone be sufficient to cover the costs of the eradication programme and under what circumstances the ecological (protection of indigenous communities) and other socio-economic benefits also need to be taken into account to justify the costs of the programme.Resource /Energy Economics and Policy,

Effects of canopy gap size on recruitment and invasion of the non-indigenous Rubus alceifolius in lowland tropical rain forest on Réunion

An important challenge of invasion biology is to understand how interactions between species traits and ecosystem properties enable alien species to become invasive at particular locations. We investigated how gap dynamics in a tropical rain forest on the island of Réunion affected the invasiveness of alien plants. In the 12 000-m2 study area, alien plants occupied 24.9% of the area of gaps, which represented 5.62% of the forest area, but only 0.8% of the understorey area. The most abundant invasive species was Rubus alceifolius, which formed dense, monospecific stands in the largest gaps (> 25 m2). Although plants could persist in the shade, a germination experiment revealed that canopy openings were essential for seedling establishment. A cyclone that struck the study area in 2002 caused a temporary thinning of the canopy, increasing light levels to above the threshold needed for germination of R. alceifolius and also stimulating the growth of established plants. We conclude that the ability of this and other alien species to colonize intact lowland tropical rain forest is strongly influenced by the prevailing gap dynamics. Because gaps are also essential for the regeneration of many native trees in our study area, there is a real danger of the forest being progressively degraded by alien plants. There are no simple solutions to controlling species such as Rubus alceifolius, but efforts should be focused mainly upon the larger gaps where the species are most invasiv

Cisgenesis, a new tool for traditional plant breeding, should be exempted from the regulation on genetically modified organisms in a step by step approach

Modern potato breeding requires over 100,000 seedlings per new variety. Main reasons are (1) the increasing number of traits that have to be combined in this tetraploid vegetatively propagated crop, and (2) an increasing number of traits (e.g., resistance to biotic stress) originates from wild species. Pre-breeding by introgression or induced translocation is an expensive way of transferring single traits (such as R-genes, coding for resistance to biotic stress) to the cultivated plant. The most important obstacle is simultaneous transfer of undesired neighbouring alien alleles as linkage drag. Stacking several genes from different wild sources is increasing this linkage drag problem tremendously. Biotechnology has enabled transformation of alien genes into the plant. Initially, transgenes were originating mainly from microorganisms, viruses or non-crossable plant species, or they were chimeric. Moreover, selection markers coding for antibiotic resistance or herbicide resistance were needed. Transgenes are a new gene source for plant breeding and, therefore, additional regulations like the EU Directive 2001/18/EC were developed. Because of a strong opposition against genetic modification of plants in Europe, the application of this Directive is strict, very expensive, hampering the introduction of genetically modified (GM) crops and the use of this technology by small and medium-sized enterprises (SMEs). Currently, GM crops are almost the exclusive domain of multinationals. Meanwhile, not only transgenes but also natural genes from the plant species itself or from crossable plant species, called cisgenes, are available and the alien selection genes can be avoided in the end product. This opens the way for cisgenic crops without alien genes. The existing EU directive for GM organisms is not designed for this new development. The cisgenes belong to the existing breeders¿ gene pool. The use of this classical gene pool has been regulated already in agreements regarding breeders¿ rights. We are proposing a step by step approach starting with a crop and gene specific derogation and monitoring towards a general exemption of cisgenic plants from the Directive. Two examples, i.e. development of cisgenic potato for resistance to Phytophthora infestans and cisgenic apple for resistance to Venturia inaequalis are discussed shortly for illustration of the importance of cisgenesis as a new tool for traditional plant breeding. Cisgenesis is simplifying introgression and induced translocation breeding tremendously and is highly recommended for SMEs and developing countrie