Presence Of Alien Species Research Articles

The potential role of an alien tree species in supporting forest restoration: Lessons from Shiretoko National Park, Japan

Restoring forests has recently received considerable attention in the context of sequestering carbon and supporting biodiversity. Although considering alien species as a tool for natural forest restoration still remains controversial, harnessing alien species when they are already present in an ecosystem might result in overall benefits for nature and society. In this study we evaluated whether the presence of an alien tree species supports or hinders the establishment of naturally regenerating forests in Shiretoko National Park, Japan. In particular, we focused on Larix kaempferi, which is widely present yet non-native to the region, and examined how this alien species affects two factors influencing the success of restoration: wind disturbance and deer herbivory. We examined the following effects of L. kaempferi plantations on natural regeneration: (1) the windbreak function for protecting native tree growth and (2) the nursery function to promote the regeneration of native tree saplings and seedlings under high herbivory pressure. We assessed tree height and regeneration, using large-scale remotely sensed data and terrestrial inventory data in five major vegetation types. We found that L. kaempferi plantations can protect native species from predominant winds. Additionally, L. kaempferi canopy cover promoted abundance and species richness in understory saplings and seedlings compared to other vegetation types such as primary and secondary forests, even under excessive browsing pressure. No regenerating L. kaempferi individuals were observed during the field census, suggesting the species is likely not invasive in our study system. The positive relationship between alien tree species and the regeneration of native tree assemblages emphasizes that existing alien species have the potential to act as nurse plants. Our findings imply that the presence of alien species can contribute to natural forest restoration by improving the local environmental conditions for native species in the short-term. Given the multiple ecological and social needs in our changing world, careful consideration is required to evaluate the long-term consequences of alien species. Especially in ecosystems in which alien species have already established, using their positive functions rather than swiftly eradicating them from the landscape might be beneficial for long-term restoration goals. We conclude that managers need to be aware of the context-dependency of alien species to make restoration more effective.

Plant diversity and conservation value of wetlands along a rural–urban gradient

Background: Wetlands are the most threatened ecosystem in South Africa despite the range of ecosystem goods and services they provide. A significant cause of wetland destruction and degradation is a lack of understanding, by planners, policymakers and developers, of their ecological and socio-economic importance.Objectives: This study assessed the floristic composition and diversity of wetlands in the former Tlokwe Municipal area along a rural–urban gradient.Methods: Fourteen wetland sites were surveyed along an urbanisation gradient. Vegetation surveys were done in quadrats along transects in each wetland recording the cover-abundance of each species. The data were analysed by using ordinations, similarity percentages, and the adjusted Floristic Quality Assessment Index.Results: Overall, the proportional species composition of urban and rural wetlands was mainly similar. Trends indicated that the alpha diversity increased with both habitat size and heterogeneity along a rural–urban gradient. In all wetlands, indigenous species were the most abundant, with the highest score in the largest urban wetland. The floristic quality varied widely along the gradient with none of the sites in pristine condition.Conclusion: The similarity in species composition and floristic quality of the wetlands, as well as the high levels of indigenous species richness, indicated that urban wetlands are worthy of conservation. However, the signs of disturbances and the presence of alien species means that restoration strategies need to be implemented to improve the quality of the wetlands.

Invasive species in the grasslands of the Central Caucasus

Biological invasions and grassland transformation are significant problems in pasture ecosystems of the Central Caucasus. The aim was to study the main patterns of invasive processes in grasslands and included identification the main vegetation parameters and abiotic factors affecting the invasion and distribution of alien species (Erigeron annuus,Ambrosia artemisiifolia, andXanthium albinum) in plant communities. We assessed vegetation parameters of steppe grasslands with the presence of alien species within 122 model plots on plains, in foothills and low mountains (250-1000 m above sea level). We also modeled the current habitats of the species in grasslands of the Central Caucasus by using the Maxent method. The most suitable for invasion and distribution ofErigeron annuusare productive grasslands (NDVI is 0.25 and more) of the foothills and low mountains with a moderately warm humid climate (average annual temperature is 5-10°C; precipitation of the most humid quarter is 240-300 mm). The most suitable forAmbrosia artemisiifoliaare medium-productive grasslands (NDVI is 0.25-0.38) of the foothills and low mountains with low vegetation coverage (65-85%) and moderately humid climate (precipitation of the most humid quarter is 225-275 mm). The most suitable forXanthium albinumat present are dry unproductive disturbed grasslands of plains.

Зв’язки чужорідних видів птахів з адвентивними рослинами насаджень парків і ботанічних садів

Introduction. In urban conditions, alien species of biota have become an integral part of the cultural landscape. Today, an overall assessment of the influence of alien species on the functioning of ecosystems of their secondary range as is relevant. Such an assessment requires knowledge of the connections formed by alien species in the secondary habitat. The purpose of the study was to find the connections of alien bird species with alien plant species in the parks and botanical gardens of Kyiv. Methods. Assessment was carried out in 10 forest parks, 3 botanical gardens, and 14 urban parks. In parks and botanical gardens, there is a wide range of plants alien to Kyiv Region, in contrast to forest parks. The number and distribution of birds were determined using the method of transect counts. The total area under study was about 370 hectares. Principal Component Analysis of the characteristics of habitats on which the number of alien birds may depend has been carried out. In the research, α-diversity indices of bird communities; number of people (individuals/km); number of pets (individuals/km); park’s area (ha); part of the territory; under the trees (%); part of alien species on plants communities (%) were analyzed. Results. Parus major, Turdus merula, Erithacus rubecula, Fringilla сoelebs dominate in all communities. Columba palumbus, Ficedula albicollis, Turdus pilaris, Columba livia, Apus apus, Sturnus vulgaris, Passer domesticus sometimes dominate in bird communities in parks and botanical gardens. There are no alien species in forest parks. 4 alien species nest in parks and botanical gardens: Streptopelia decaocto, Dendrocopos syriacus, Phoenicurus ochruros, Serinus serinus (from the last century). Phylloscopus trochiloides was observed for the first time. Nesting of Ph. trochiloides was not confirmed. Alien birds are not evenly distributed (0–3 species). Nest density is low: S. decaocto 0.013±0.01–0.021±0.01, D. syriacus 0.031±0.01–0.043±0.04, Ph. ochruros 0–0.034±0.02, S. serinus 0.013±0.01–0.017±0.01. We assume that alien bird species is an element that replaces the species that were eliminated from the community. Their nesting in forest parks is an indicator of a disruption of the functioning of the forest ecosystem as a result of anthropogenic transformation of the forest. The presence of alien species of birds in modern parks and botanical gardens is normal. Their biotopes were created on the sites of destroyed landscapes and with using alien plant species. Conclusion. In parks and botanical gardens, a specific structure of the plant community has developed due to the introduction of alien plant species, with a tree height of 3–5 m. As a consequence, alien birds find nesting stations in communities of nesting birds, which were not occupied by native species due to the absence of many species of tree canopy nesters and ground nesters birds. Alien species of birds also get access to vacant food resources. Alien birds use vacant resources. It was found that the area of parks has the most profound positive impact on the number of species of alien birds (+0.517), as well as the ratio of alien birds (+0.227). Other important correlations observed were the following: the number of species of alien birds in the bird communities – a part of alien species in plant communities (+0.084), the ratio of alien birds – part of alien species in plant communities (+0.041). The strongest negative connection is as follows: the number of species of alien birds in the bird communities – the number of pets (-0.213), the ratio of alien birds – the number of pets (-0.384).

Biological invasions in World Heritage Sites: current status and a proposed monitoring and reporting framework

UNESCO World Heritage Sites (WHS) are areas of outstanding universal value and conservation importance. They are, however, threatened by a variety of global change drivers, including biological invasions. We assessed the current status of biological invasions and their management in 241 natural and mixed WHS globally by reviewing documents collated by UNESCO and IUCN. We found that reports on the status of biological invasions in WHS were often irregular or inconsistent. Therefore, while some reports were very informative, they were hard to compare because no systematic method of reporting was followed. Our review revealed that almost 300 different invasive alien species (IAS) were considered as a threat to just over half of all WHS. Information on IAS management undertaken in WHS was available for fewer than half of the sites that listed IAS as a threat. There is clearly a need for an improved monitoring and reporting system for biological invasions in WHS and likely the same for other protected areas globally. To address this issue, we developed a new framework to guide monitoring and reporting of IAS in protected areas building on globally accepted standards for IAS assessments, and tested it on seven WHS. The framework requires the collation of information and reporting on pathways, alien species presence, impacts, and management, the estimation of future threats and management needs, assessments of knowledge and gaps, and, using all of this information allows for an overall threat score to be assigned to the protected area. This new framework should help to improve monitoring of IAS in protected areas moving forward.

Two Seas for One Great Diversity: Checklist of the Marine Heterobranchia (Mollusca; Gastropoda) from the Salento Peninsula (South-East Italy)

The Salento peninsula is a portion of the Italian mainland separating two distinct Mediterranean basins, the Ionian and the Adriatic seas. Several authors have studied the marine Heterobranchia (Mollusca, Gastropoda) fauna composition living in the Ionian Sea, but to date further knowledge regarding this interesting group of mollusks is still needed. Recent studies have corroborated the peculiarity of the Mediterranean Sea showing high levels of endemism and cryptic diversity. On the other hand, marine sea slugs have been revealed to be important indicators of the marine ecosystem’s health, due to their species-specific diet that consist of a vast variety of sessile and benthic invertebrates. A baseline study of the marine Heterobranchia diversity is therefore a necessary step to reveal the hidden diversity and to monitor the possible presence of alien species. The present study shows results from approximately 600 scientific dives carried out during a nine-year period in all of the main submarine habitats of the studied area, while accounting for the marine Heterobranchia from both the Ionian and Adriatic Seas. With this contribution, the list of marine Heterobranchia inhabiting the Salento Peninsula rises to 160. Furthermore, it also reports, for the first time, the presence of one alien species and three new records for Italian waters. Ecological notes and geographical distribution for each added species are provided together with animal iconography, consisting mainly of in situ photographs, for species identification.

Alien plants and flower visitors disrupt the seasonal dynamics of mutualistic networks

Abstract Alien species can drastically disrupt ecological processes such as those involving plant–pollinator interactions, performing central roles that may affect the structure of native pollination networks. However, most studies to date have focused on a single trophic level of alien species, evaluating either the impacts of an alien pollinator or an alien plant species, and have neglected their joint effects on the seasonal dynamics of mutualistic networks. Here, we aim to fill this gap by investigating how alien plant and flower visitor (here used as a proxy for pollinator) species structure temporal networks, and how these species affect the beta‐diversity of interactions across a flowering season. Our study system is located in the South Island of New Zealand, where 68% of the sampled plant species and 14% of the flower visitor species that interact with them are alien. Alien flower visitor species exhibited higher interaction degree, specialization and strength than their native counterparts, while alien plant species showed the opposite pattern. We found that invader complexes (in which alien species interact significantly more with each other than with native species) were established across the season, and interactions involving alien plant species were the main connectors of the temporal networks. Both alien plant and flower visitor species increased total interaction turnover through the flowering season by promoting interaction rewiring in the case of alien plants and by increasing species turnover in the case of alien flower visitors. Synthesis. This study provides one of the first empirical reports of alien species shaping the seasonal dynamics of plant–flower visitor networks. We demonstrate that the presence of alien species may simultaneously lead to a homogenization of plant species composition and increase the diversity of plant–flower visitor interactions through a flowering season. Additionally, we highlight the importance of considering the role of different trophic levels when analysing the impact of alien species in plant–flower visitor communities. Overall, our findings suggest that management strategies should pay particular attention to the timescale at which interactions with alien species dissolve or form, and to the consequences and drivers of such seasonal dynamics.

Living with aliens: Suboptimal ecological condition in semiaquatic snakes inhabiting a hot spot of allodiversity

The presence of alien species can embody a form of disturbance for natural communities and the concomitant presence of alien species at different levels within the trophic chain may compromise ecosystem functionality. We studied the ecology of two species of snake (Natrix tessellata and N. natrix) in a system of five ponds with a high number of alien species at a Mediterranean area in central Italy. We evaluated the potential perturbations to ecological traits of snakes due to the presence of alien species, including their body size, population density, and food habits. We compared the studied populations' body size to that estimated in conspecific populations studied elsewhere, including populations at close distance from the study site. Distance sampling and Capture-Mark-Recapture techniques were used to calculate the population density. Diet was estimated using stomach contents and stable isotope ratios (δ15N and δ13C), using Bayesian stable isotope mixing models to estimate the contribution of food sources and species' isotopic niche spaces. Few prey items were found in the stomach contents of either species, with Ameiurus melas as the main prey. Based on isotope niche analyses, N. tessellata diet consisted of only alien species, and N. natrix diet mostly relied on alien species (>80%). Stomach contents revealed high overlap between the two species, although isotopes showed a random resource use (i.e. low isotopic niche space overlap). Overall, we caught a low number of individuals, indicating small population sizes. Moreover, snakes at the study site were comparatively smaller in size than most other populations found in the literature and almost all the recorded individuals were in very poor condition or injured by ingested alien prey. We suggest that the presence of rich allodiversity has negatively affected the snakes’ fitness by decreasing their foraging performance, increasing their risk of being preyed upon, or through other mechanisms.

Aliens cruising in: Explaining alien fouling macro-invertebrate species numbers on recreational yachts

The extent of biofouling on recreational vessels has been used as a proxy for the presence of alien species and has been linked with vessel characteristics. However, the relationship between these factors and alien species numbers has not been examined, despite the importance of this metric for invasive species management. This study assessed physical characteristics, maintenance regimes and travel patterns of yachts and their relationship with the number of macro-invertebrate alien species present on vessels from four South African marinas. Overall, 88% of yachts were fouled with macro-invertebrate alien species. The only factor that influenced alien species numbers in the context of this study was the primary use of yachts, with cruising yachts supporting significantly more alien species than racing yachts. This is likely linked to differences in cleaning regimes, as racers are subject to rigorous and frequent cleaning. These findings suggest that cruising vessels may play a key role in the intra-regional transfer of alien species and that racing yachts likely pose a lower biosecurity threat.

ANCAMAN JENIS IKAN ASING LOUHAN TERHADAP IKAN ENDEMIK DI DANAU MATANO, SULAWESI SELATAN

Lake Matano is one of the ancient lakes in Sulawesi where some endemic fish species of Telmatherina, Mugilogobius, Oryziasand Glossogobius matanensis lived. The presence of alien species can be on threat for the loss of biodiversity in fresh waters, including endemic fish in Lake Matano. The research aim to review the threat of louhan fish as alien species to endemic fish in Lake Matano. The study was conducted in Lake Matano at five stations in April and August 2015 namely Lawa, Nuha, Petea, Pantai Impian, and Pantai Kupu-kupu. Sam-ples were collected using experimental gillnet with mesh size of ¾; 1; 1¼; 1⅟2; 2; 2,5; and 3 inches. Fouteen species were found consist of 10 endemic species and red list.These were three of genus Glossogobius, seven species of Telmatherina, and four alien species of the carp (Cyprinus carpio), louhan, gourami (Trichopodus trichopterus), and tilapia (Oreochromis niloticus). The most common species of endemic fish is T. antoniae. Louhan is the result of a hybrid species Amphilopus citrinellus x Cichlasoma trimaculatum. The abundance of louhan is 64 in April and 40 fishes in August, respectively at a time caught. The percentage ratio of louhan to endemic fish was of 8.6% and 18.3%. This indicated that the louhan fish tend to be invasive and certainly threatened endemic fish survival in this lake. The maturity of gonads of louhan is in the level of I - IV that enables the fish to reproduce quickly.

A global meta-analysis of the ecological impacts of alien species on native amphibians.

The exponential increase in species introductions during the Anthropocene has brought about a major loss of biodiversity. Amphibians have suffered large declines, with more than 16% considered to be threatened by invasive species. We conducted a global meta-analysis of the impacts of alien species on native amphibians to determine which aspects of amphibian ecology are most affected by plant, invertebrate, fish, amphibian, reptile, or mammal introductions. Measures of fitness were most strongly affected; amphibian performance was consistently lower in the presence of alien species. While exposure to alien species caused a significant decrease in amphibian behavioural activity when compared with a no species control, this response was stronger towards a control of native impacting species. This indicates a high degree of prey naiveté towards alien species and highlights the importance of using different types of controls in empirical studies. Alien invertebrates had the greatest overall impact on amphibians. This study sets a new agenda for research on biological invasions, highlighting the lack of studies investigating the impacts of alien species on amphibian terrestrial life-history stages. It also emphasizes the strong ecological impacts that alien species have on amphibian fitness and suggests that future introductions or global spread of alien invertebrates could strongly exacerbate current amphibian declines.

Changes in the benthic fauna composition in the Upper Vistula over the last 50 years – the consequences of the water pollution reduction and alien species invasion

Abstract The organic pollution of the Upper Vistula waters has been significantly reduced since the mid-20th century. Also salinity has gradually decreased, following an increase observed until the 1990s. Furthermore, the number of alien species has systematically increased. The above-mentioned changes have affected the richness and composition of the benthic fauna. They are particularly remarkable in the river stretch between the town of Oświęcim and the city of Kraków. The improvement of water quality has resulted in the increased number of taxa, mainly those characteristic of moderately polluted water, and the disappearance of taxa typical of strongly polluted or deoxygenated water. Despite the increased salinity level persisting for many years, only three benthic species of brackish waters (Gammarus tigrinus, Paranais frici and P. litoralis) were found in the Upper Vistula. Taxa considered to be euryhaline or halophilous were more numerous. In the 1960s, only one alien species (Physa acuta) was found, but the increased number of non-indigenous species in the last decades is visible, particularly among gammarid crustaceans (Amphipoda, Gammaroidea). The presence of alien species has not caused any visible changes in the species abundance of oligochaetes and mollusks.

Genetic differentiation, local adaptation and phenotypic plasticity in fragmented populations of a rare forest herb.

BackgroundDue to habitat loss and fragmentation, numerous forest species are subject to severe population decline. Investigating variation in genetic diversity, phenotypic plasticity and local adaptation should be a prerequisite for implementing conservation actions. This study aimed to explore these aspects in ten fragmented populations of Physospermum cornubiense in view of translocation measures across its Italian range.MethodsFor each population we collected environmental data on landscape (habitat size, quality and fragmentation) and local conditions (slope, presence of alien species, incidence of the herbivorous insect Metcalfa pruinosa and soil parameters). We measured vegetative and reproductive traits in the field and analysed the genetic population structure using ISSR markers (STRUCTURE and AMOVA). We then estimated the neutral (FST) and quantitative (PST) genetic differentiation of populations.ResultsThe populations exhibited moderate phenotypic variation. Population size (range: 16–655 individuals), number of flowering adults (range: 3–420 individuals) and inflorescence size (range: 5.0–8.4 cm) were positively related to Mg soil content. Populations’ gene diversity was moderate (Nei-H = 0.071–0.1316); STRUCTURE analysis identified five different clusters and three main geographic groups: upper, lower, and Apennine/Western Po plain. Fragmentation did not have an influence on the local adaptation of populations, which for all measured traits showed PST < FST, indicating convergent selection.DiscussionThe variation of phenotypic traits across sites was attributed to plastic response rather than local adaptation. Plant translocation from suitable source populations to endangered ones should particularly take into account provenance according to identified genetic clusters and specific soil factors.

Patterns of occurrence of semi-aquatic reptiles in highly invaded Mediterranean rivers

The fluvial systems in the north-east of the Iberian Peninsula are highly disturbed habitats, with widespread occurrence of alien species. Previous studies have shown that alien species have a major impact on native freshwater fauna, but it is not known what effect they have on semi-aquatic reptiles. Here the author investigated the factors that influence the occurrence of three species of semi-aquatic reptiles, one turtle (Mauremysleprosa) and two snakes (NatrixastreptophoraandNatrixmaura), at 261 sites in seven rivers/streams in Girona (north-eastern Spain). The studied semi-aquatic reptiles are habitat generalists which can occupy sections of rivers with altered regimes. The relationships of reptile presence to abiotic niche parameters and the presence of alien species were evaluated, as well as the patterns of pairwise co-occurrence between the reptiles. The presence of alien species did impact one out of three reptiles in this community. The association between both species of natricines was weakly negative, suggesting that interspecific competition does not structure their co-occurrences. The removal of alien species is the most appropriate strategy to preserve the complete diversity of native semi-aquatic reptiles.

Distribution of alien species along sand dune plant communities zonation

Background and purpose: For a fairly long period, Velika plaža in Ulcinj, Montenegro has been considered to be one of the best-preserved sites with psammophilous vegetation along the Adriatic coast. In recent years, however, this area has been significantly transformed as a result of various human disturbances (e.g., a non-sustainable approach to touristic development, illegal dumping, sand exploitation etc.), and has become prone to alien plant invasions. We made a transect survey to assess the presence of alien species in the psammophilous communities.Materials and methods: In order to make a survey of the present state of plant life on Velika plaža, its floristic composition and zonation of plant communities, 20 transects were set perpendicular to the coast, regularly every 500 m. Quadrats (2 x 2 m) were laid contiguously in the form of a belt transect starting from the area with the first colonizing plants towards the end of the sand dune system with forest vegetation. This resulted in a matrix of 1124 plots and 196 species (15 alien and 181 native), on which multivariate analysis was performed.Results: Nine plant communities were detected, arranged in zonation from sea to inland. All of them were characterised by the presence of alien species. The least affected was the plant community dominated by Cladium mariscus, while the most affected ones were dominated by Scirpoides holoschoenus and Tripidium ravennae. Psammophilous vegetation is less affected by alien species than wetland communities. Foredunes are dominated by Xanthium orientale ssp. italicum, while Oenothera species are predominant on stable dunes.Conclusions: Sand dunes are a highly invaded ecosystem, with changed plant communities, so conservation measures should be considered.

Alien turf: Overfishing, overgrazing and invader domination in south‐eastern Levant reef ecosystems

Abstract Coastal reefs are highly diverse marine ecosystems that in many regions suffer today from growing pressures by human activities. Among the most highly‐stressed are those found in the Levantine basin (south‐eastern Mediterranean Sea). The Levant represents the trailing‐edge of distribution of native species where they are exposed to the most extreme temperature and salinity conditions, and the region is also fast‐warming and exposed to a great many alien species and strong fishing pressure. In this study, the ecological state of reefs in the south‐eastern Levant was assessed quantitatively (including inside a small marine reserve) using current, extensive, survey data with reference to anecdotal historical information on their more pristine past. The results of very extensive subtidal community surveys that were conducted in north Israel indicate that reefs in this area are currently dominated by turf‐forming algae and aliens, and sustain low numbers of top predators. Specifically, it was found that on these Levant reefs: (1) commercial species represent a very small part of the fish assemblage (except inside the reserve); (2) alien species constitute a considerable portion (23–44%) of the fish assemblage (including in the reserve) and 95–99% of epi‐benthic molluscs, including inside the marine reserve; and (3) turf barrens are the dominant substrate cover, while cover of native brown algae canopy is limited to small patches occurring only during winter and spring. These findings suggest that the Levant reefs have been highly transformed by overfishing and alien invasions, and probably also climate change, and that even well managed marine reserves had little effect on alien species presence. From a biogeographic‐conservation perspective, as both warming and bioinvasions continue in the Mediterranean, it is expected that this degraded reef state will gradually advance westward. Alleviating fishing pressure with marine reserves might make the reefs more resilient to these regional pressures, but alien invaders will remain a dominant feature in the system. Therefore, a more realistic conservation target might be the preservation or restoration of ecosystem functions rather than the original native biodiversity.

Management as a driver of functional patterns and alien species prominence in weed communities of irrigated orchards in Mediterranean areas

Abstract Weed communities in irrigated orchards form spontaneous vegetative cover containing a remarkable presence of alien species. This plant cover can negatively affect the growth and productivity of orchards by reducing yield, but can also play a positive role by preventing soil erosion, increasing biodiversity and providing pollination services. Compositional and functional attributes of these weed communities are configured by management practices. Therefore, it is crucial to disentangle which differences in weed communities are mediated by management practices in order to establish management that promotes weed covers that enhance benefits while reducing negative effects on the orchards. In irrigated orchards of the Mediterranean area, management is dominated by irrigation (flood/drip) and weed control (mechanical/chemical). To identify how differences in irrigation and weed control modify weed communities in orchards, floristic surveys were carried out in mowed and herbicide-treated plots on drip and flood irrigated orchards. Weed community structure was evaluated in terms of species cover, diversity and the prominence of alien species for each management regime from a floristic and a functional approach. Results showed that irrigation system is the main factor influencing weed community structure. Compared to drip, flood irrigation is associated with a denser weed community with higher presence of alien weeds. Similarly, environmental conditions created by irrigation determine taxonomical and functional composition of weed communities and modulate the effect of weed control methods Flooding favours alien species, C4, perennial grasses, clonal species, zoochorous and hydrochorous and wind-pollinated species, whereas drip irrigation selects mostly native C3 forbs, non-clonal, wind-dispersed and insect pollinated species. Therefore, this study provides insights into how modernizing irrigation method from a flood to a drip system can promote vegetative cover that maximizes benefits to the orchards and the environment while minimizing negative effects of the weeds and prominence of alien species within the weed community.

Spatial Downscaling of Alien Species Presences Using Machine Learning

Large scale, high-resolution data on alien species distributions are essential for spatially explicit assessments of their environmental and socio-economic impacts, and management interventions for mitigation. However, these data are often unavailable. This paper presents a method that relies on Random Forest (RF) models to distribute alien species presence counts at a finer resolution grid, thus achieving spatial downscaling. A sufficiently large number of RF models are trained using random subsets of the dataset as predictors, in a bootstrapping approach to account for the uncertainty introduced by the subset selection. The method is tested with an approximately 8×8 km2 grid containing floral alien species presence and several indices of climatic, habitat, land use covariates for the Mediterranean island of Crete, Greece. Alien species presence is aggregated at 16×16 km2 and used as a predictor of presence at the original resolution, thus simulating spatial downscaling. Potential explanatory variables included habitat types, land cover richness, endemic species richness, soil type, temperature, precipitation, and freshwater availability. Uncertainty assessment of the spatial downscaling of alien species’ occurrences was also performed and true/false presences and absences were quantified. The approach is promising for downscaling alien species datasets of larger spatial scale but coarse resolution, where the underlying environmental information is available at a finer resolution than the alien species data. Furthermore, the RF architecture allows for tuning towards operationally optimal sensitivity and specificity, thus providing a decision support tool for designing a resource efficient alien species census.

The ability of the Arundo donax crop to compete with weeds in central Spain over two growing cycles

Nowadays there is extensive literature dealing with the cultivation of Arundo donax L. for biomass and bio-based compounds. Several agronomic aspects have been addressed while others, such as the need for weed control in the A. donax crop, have been barely investigated. In this work, the objective was to study the effect of weed competition on the A. donax crop in a Mediterranean environment over two growing cycles: the establishment year and the first maturity year of the crop. Weed diversity, weed abundance, plant traits and crop yield were determined in a field experiment with three treatments: no weed removal, weed removal in May and weed removal in June. The presence of alien species of genus Conyza Lessing was recorded throughout the field experiment. Weeds were detrimental to the A. donax crop in the two harvests under study despite the fact that A. donax competition increased from the first to the second growing cycle. In this study, the yield loss was estimated at 55% in the first harvest and decreased to 36% in the second one, showing higher A. donax competition. The results showed that weed removal should not be delayed until June for higher biomass yield.

Changes in presence of alien species in the ruderal vegetation of a representative ecosystem in a major city over 30 years: a case study from Bratislava

The study is focused on evaluating changes in the presence of alien species in ruderal vegetation. Two datasets comprising phytosociological relevés of ruderal communities during two time periods within the Bratislava City (in southwestern Slovakia) were analyzed. The old dataset consisted of 387 relevés recorded in the years 1975–1982, and the more recent dataset consisted of 308 relevés from the years 2011–2014. The relevés from both time periods were assigned to phytosociological classes via the same procedure – numerical classification (hierarchical clustering) using HIERCLUS software. The average values of the percentage number and percentage cover of the archaeophytes and neophytes as groups in the earlier and more recent relevés of each class were compared by the main effects ANOVA analysis in the STATISTICA 7.0 software. The proportion of each taxon of archaeophytes and neophytes in both datasets was also calculated. The invasive status, origin, and life forms of alien species in both datasets were compared. In total, both datasets comprised 120 archaeophytes and 71 neophytes. The old dataset contained more archeaophytes than the more recent dataset. On the contrary, the more recent dataset contained more neophytes than the old dataset. In the years 2011–2014, more invasive neophytes were recorded than in the past. The results revealed a statistically significant decrease in the average percentage number of archaeophytes in the classes &lt;em&gt;Stellarietea mediae&lt;/em&gt;, &lt;em&gt;Artemisietea vulgaris&lt;/em&gt;, and &lt;em&gt;Galio-Urticetea&lt;/em&gt;, and a decrease in the average percentage cover of archaeophytes in the class &lt;em&gt;Artemisietea vulgaris&lt;/em&gt;, compared to the past. On the contrary, a statistically significant increase in the average percentage number and cover of neophytes in the classes &lt;em&gt;Artemisietea vulgaris&lt;/em&gt; and &lt;em&gt;Galio-Urticetea&lt;/em&gt; was recorded. Some rare species of archaeophytes were only recorded 30 years ago (e.g., &lt;em&gt;Kickxia elatine&lt;/em&gt;, &lt;em&gt;Silene gallica&lt;/em&gt;). Furthermore, several species of neophytes (including some invasive taxa, e.g., &lt;em&gt;Fallopia japonica&lt;/em&gt;, &lt;em&gt;Helianthus tuberosus&lt;/em&gt;, &lt;em&gt;Juncus tenuis&lt;/em&gt;) occur only currently in the ruderal vegetation of Bratislava.