Invasive Tree Research Articles

Established Invasive Tree Species Offer Opportunities for Forest Resilience to Climate Change

Established Invasive Tree Species Offer Opportunities for Forest Resilience to Climate Change

1118. Dendrocacalia crepidifolia (Nakai) Nakai: Compositae

SummaryThe monotypic genus Dendrocacalia (Nakai) Nakai, with the species Dendrocacalia crepidifolia (Nakai) Nakai, a large shrub or small tree from the Bonin Islands or Ogasawara of Japan, is described and illustrated. Its ecology, pollination, dioecy and conservation are discussed; a detailed description is given. The species is now apparently restricted to the Haha‐jima island group, where the largest number of populations exist on Haji‐jima itself. Threats to its conservation are from two invasive trees, Ficus microcarpa and Psidium littorale.

A biosecurity perspective on urban trees in public and private spaces and trees available from nurseries

Urban trees are of high importance for healthy urban ecosystems. However, some trees are invasive plants that may ‘escape’ from urban areas into natural environments. Furthermore, invasive forest pests often arrive and establish in urban environments before they spread to forest ecosystems. Therefore, knowledge of tree species composition in urban areas is important for the biosecurity of cities and surrounding forests. Despite this, urban tree inventories often lack information on trees on private properties. To assess the potential role of urban areas as a source of invasive trees as well as invasive pests of trees, we compared the species composition of urban trees in public and private spaces in several Swiss cities and in tree nurseries (henceforth: ‘nurseries’) in Switzerland. We analysed the various data sets we compiled regarding invasive tree species, and examined how many trees are potential hosts for invasive quarantine pests of trees. We found no statistically significant difference in tree species composition in public and private urban areas, but the proportion of non-native trees was higher in private than in public spaces. Tree species available in nurseries and those present in cities were not significantly different, with larger urban tree inventories having a greater overlap with the species available in nurseries. Five of eight tree species considered invasive whose sale was banned since September 2024 were still on sale ten months before the ban came into force. All eight tree species were present in urban tree inventories. Importantly, between 91 % and 97 % of all urban trees in public and private spaces were suitable hosts for at least one quarantine forest pest. Given the pivotal role that urban trees play for the health of urban and peri-urban ecosystems, knowledge of tree species composition is essential from a biosecurity perspective. Our findings suggest that the combination of public urban tree inventories and trees available from nurseries can provide an estimate of the composition of private urban trees and can be useful for invasive species monitoring.

Effects of the control of an invasive tree on the structure of a plant-frugivore network.

Invasive non-native species are one of the main causes of degradation of ecosystems worldwide. The control of invasive species is key to reducing threats to ecosystem viability in the long term. Observations of structural changes in ecological interaction networks following invasive species suppression can be useful to monitor the success of ecological restoration initiatives. We evaluated the structure of plant-bird frugivory interaction networks in a plant community invaded by the guava tree (Psidium guajava L.) by comparing network metrics before and after control actions. Psidium guajava was relevant in all metrics for the unmanaged network in this study, with high degree centrality and high nestedness contribution. Based on the asymmetry of species interactions, we found that birds were highly dependent on the invasive plant before suppression. Once P. guajava trees were eliminated, bird and plant species richness, total number of interactions, and modularity increased, whereas nestedness and interaction strength asymmetry decreased. The diet of the bird community became more diversified once P. guajava was no longer available and relevant species roles in community structure emerged. Our results corroborate the fact that ecological restoration interventions should include the control of non-native plant species that attract frugivorous animals in order to diversify plant-frugivore interactions and thus maintain biodiversity in natural ecosystems.

Not seeing the wood for the (invasive) trees: Visitors’ perceptions of invasive wilding conifers in the New Zealand landscape

Currently we know little about how visitors perceive invasive species, nor how this may vary across visitor cohorts. Previous research suggests that visitors to natural areas have a low awareness of the impact of invasive species. This note reports on a survey of domestic and international visitors (n = 231) in New Zealand, investigating their awareness of invasive wild conifers and attitudes toward their control. Awareness of the wild conifer problem was generally low, especially among international visitors. There were significant differences between domestic and international visitors, and among visitors of different nationalities for how wild conifers were perceived. International visitors, and particularly those from China or other Asian countries were more accepting of wild conifers in the landscape and less supportive of eradication. The findings have implications for management of invasive species, which requires the support of all stakeholders, including tourists, recreationists and their associated sectors.

Invasion of Prosopis trees into arid ecosystem alters soil carbon and nitrogen processes and soil trace gases emissions

The invasion of drylands by leguminous mesquite (Prosopis spp.) is frequently associated with increases in the soil organic carbon (C) and nitrogen (N) pools. These increases stimulate soil microbial activity and accelerate soil C and N cycling. However, the impact of mesquite invasion on soil biogeochemistry, especially the emission of trace gases, in an ecosystem with an already established population of N-fixing plants is not well studied. To fill this knowledge gap, we quantified the in-situ soil trace gas emissions and the potential microbial activity in soils under invasive mesquite (Prosopis juliflora) trees (Prosopis), native acacia (Acacia tortilis) trees (Acacia), and in unvegetated soil between trees (Bare soil) on the western shore of the Dead Sea. To account for contributions of spatial and weather variabilities to the emission processes we conducted measurements across two geographic sites, 45 km apart, over two years, both under naturally dry soil conditions and after soil wetting. Before wetting, soil emissions of carbon dioxide (CO2) and nitric oxide (NOx) followed the order: Acacia > Prosopis ≥ Bare soil, while soil nitrous oxide (N2O) emissions were low and uniform across the three habitats. The soil inorganic N concentration, microbial biomass, and water-extractable organic C were significantly higher under the A. tortilis canopies compared with P. juliflora and Bare soil. After wetting, soil trace gases emissions increased up to 66, 1534, and 42 times, for CO2, N2O, and NOx, respectively, and remained higher under the native A. tortilis than under P. juliflora and Bare soil (Acacia > Prosopis > Bare soil). The potential soil microbial activity, however, was similar between the soils under the tree canopies. Our results show that the establishment of invasive leguminous trees increase soil CO2 and gaseous N emissions relative to the Bare soils, but not relative to native leguminous trees.

Germination and seedling growth of closely related native and invasive legume trees in Nepal

Germination and seedling growth of closely related native and invasive legume trees in Nepal

Occurrence of Arbuscular Mycorrhizal Herbs Decreases Selectively in Communities Dominated by Invasive Tree Acer negundo.

We tested whether one of the consequences predicted for alien plant invasion by the mutualism disruption hypothesis was true in the case of the ash-leaved maple Acer negundo L. The study aimed to determine whether the occurrences of mycorrhizal and nonmycorrhizal herbs varied similarly or differently in communities with varying degrees of A. negundo dominance. The analysis included the results of 78 vegetation descriptions carried out in Belarusian Polesia, the Middle Volga region, and the Middle Urals. Communities with or without A. negundo dominance were described in each region. The mycorrhizal status of plant species was determined using the FungalRoot Database. Species that are more likely to form arbuscular mycorrhiza were found to occur less frequently in A. negundo thickets. On the contrary, a higher probability of the nonmycorrhizal status was associated with a lower frequency of detection in A. negundo thickets. Therefore, the occurrence of arbuscular mycorrhizal herbs was found to selectively decrease in communities dominated by A.negundo.

Phenological alignment of a galling insect used as biocontrol agent for an invasive tree following hemisphere translocation

Acacia longifolia is one of the most widespread invasive alien plant species along coastal areas in Portugal. In South Africa, this species is also invasive and has been controlled for over 40 years by the Australian gall wasp Trichilogaster acaciaelongifoliae. This biological control agent was introduced in Portugal in 2015, being released immediately after import, i.e., without a laboratory rearing period to adjust the life cycle, and is now established in many locations along the coast. When released in the northern hemisphere, the agent came from the austral spring, with the host-plants having tiny buds, and faced boreal winter with host-plants having large buds. As such it had to synchronize its life cycle with the seasons and phenology of the host-plant in this new location. Both locations have mild summer Mediterranean climates. The present work aims to better understand the life cycle of T. acaciaelongifoliae in the northern hemisphere and how it has aligned its phenology to these new conditions, namely different host-plant phenology and seasons. Two sites were selected (Pataias and São Jacinto), and monitored monthly, from November 2021 to October 2022, to: i) describe the early stages of the life cycle, since oviposition, by collecting and dissecting A. longifolia buds of 5 branches/five trees/site; ii) characterize the stages of the life cycle of T. acaciaelongifoliae inside the developing galls, by collecting and analysing 50 galls/site; and iii) monitoring the development of galls on 10 A. longifolia marked branches/ five trees, in the field. The results suggest that T. acaciaelongifoliae in the northern hemisphere has a univoltine life cycle, but the generations are not completely synchronized at the two sites and even within each site. It is not excluded that two generations may occur throughout the year, i.e., a bivoltine cycle, in some individuals. The alignment of the life cycle may not yet be stabilized. The life cycle seems to be more advanced in the site located further south, Pataias, where adults emerged earlier. Reproductive galls dominated in almost all months, as in South Africa. The present work advances the knowledge on the life cycle of T. acaciaelongifoliae, especially in the northern hemisphere, providing details about the timings and duration of each life cycle stage in this new location. These results are relevant for the management of A. longifolia, stressing the plasticity of the agent life cycle which can facilitate the planning of the biocontrol agent releases in new locations.

Resprouting Control of Ailanthus altissima by Means of Cut and Stump Covering: Experimental Evidence for a Promising Technique

Ailanthus altissima is an invasive tree threatening the biodiversity in natural and disturbed habitats of temperate regions, primarily because of its high resprouting vigor. To test the effect of light exclusion on stem and root sprouting, black covers were applied on the cut stumps of 3-year-old saplings grown in pots. The treatments were as follows: SL, stumps exposed to light; SH, only stumps covered; SPH, the entire pot covered; C, intact control plants. The covers were removed when the root sprouts appeared. The emergence of stem and root sprouts was checked weekly, and their number and biomass were determined at the growth peak (cut I and III) and the end (cut II and IV) of two seasons after cutting. Stem sprouts were produced only in the first growth season in SL and SH and never in SPH and the controls. The number and biomass of the root sprouts were the highest in SH at cut I and in SL in the following cuts. In SH, the sprouting ceased completely after cut I, suggesting a rapid consumption of root reserves, while in SL and SPH, repeated cutting progressively reduced the sprouting vigor. We concluded that covering the stems after cutting is a promising technique to control ailanthus resprouting without the use of herbicides.

Localization and Quantification of UV-Absorbing Compounds in an Invasive Deciduous Tree Species, Chinese Tallow (Triadica sebifera)

Localization and Quantification of UV-Absorbing Compounds in an Invasive Deciduous Tree Species, Chinese Tallow (<i>Triadica sebifera</i>)

The Goldilocks Dilemma: the optimal management strategy for invasive trees in the Atlantic Forest

The Goldilocks Dilemma: the optimal management strategy for invasive trees in the Atlantic Forest

Urban Biodiversity Index for Trees: A Climate Adaptation Measure for Cities Based on Tree Inventories

A historically large percentage of the world’s population has moved to urban areas in the past few decades, causing various negative effects for the environment, such as air, noise, water, and light pollution; land degradation; and biodiversity loss. Under the current climate crisis, cities are anticipated to play an essential part in adaptation strategies to extreme atmospheric events. This study aims at developing indicators at an urban scale that can highlight adaptation progress by investigating relevant data (especially in situ) and statistics at a pan-European level in support of the EU’s strategy for adapting to the impacts of climate change. The proposed indicator, Urban Biodiversity Indicator for Trees (UBI4T), which can be derived from city tree inventories, assesses one essential component of urban biodiversity by computing the proportion of native, alien, invasive, and toxic tree species spatially across a city. According to our findings (applying the UBI4T for Amsterdam and exploring its policy potential for Barcelona), the UBI4T can offer crucial information for decision and policy makers, as well as stakeholders of a city, with the aim of conducting dedicated and effective strategic initiatives to restore, improve, and protect nature in the urban environment, thus contributing to adaptation and resilience to extreme atmospheric events in cities.

Endobronchial Ultrasonography to Assess and Evaluate Tracheobronchial Tree Invasion in cT4b Esophageal Cancer Patients Treated with Definitive Chemoradiotherapy: Assessment of Resectability.

In cT4b esophageal cancer, accurate assessment of tracheobronchial tree invasion after definitive chemoradiotherapy (dCRT) aids in the selection of patients for whom an oncologic radical esophagectomy can be achieved. The current report aimed to determine the accuracy of endobronchial ultrasound in assessing tumor invasion in the tracheobronchial tree after dCRT in patients with cT4b esophageal cancer. Esophageal cancer patients with suspicion of tracheobronchial tree invasion on the diagnostic contrast-enhanced computed tomography (CT) who underwent a staging endobronchial ultrasonography (EBUS) were eligible for inclusion in this study. To assess the accuracy of the EBUS in assessing tumor ingrowthin the tracheobronchial tree after dCRT, patients who had an EBUS during restaging and underwent surgery were included in the final analysis. The final analysis included 26 patients. For 18 (90%) of 20 patients in whom the anatomy of the tracheobronchial tree was restored on the restaging EBUS and tumor invasion was considered to be absent, a radical esophagectomy was achieved. In six patients, persistent ingrowth was observed during the restaging EBUS. For these patients, the EBUS was repeated after a median of 9weeks. Tumor invasion was considered to be absent in four patients, and a radical resection was achieved in three of these patients. The EBUS provides valuable information on the assessment of tracheobronchial tree invasion in cT4b esophageal cancer patients after dCRT. This information could aid in the proper selection of patients who benefit from a curative but highly invasive esophagectomy.

Preliminary insights of the genetic diversity and invasion pathways of Cedrela odorata in the Galapagos Islands, Ecuador.

Cedrela odorata is considered the second most invasive tree species of the Galapagos Islands. Although it is listed in CITES Appendix II and there are population losses in mainland Ecuador, in Galapagos it is paradoxically a species of concern due to its invasive potential. Genetic studies can shed light on the invasion history of introduced species causing effects on unique ecosystems like the Galapagos. We analyzed nine microsatellite markers in C. odorata individuals from Galapagos and mainland Ecuador to describe the genetic diversity and population structure of C. odorata in the Galapagos and to explore the origin and invasion history of this species. The genetic diversity found for C. odorata in Galapagos (H e = 0.55) was lower than reported in the mainland (H e = 0.81), but higher than other invasive insular plant species, which could indicate multiple introductions. Our results suggest that Ecuador's northern Coastal region is the most likely origin of the Galapagos C. odorata, although further genomic studies, like Whole Genome Sequencing, Rad-Seq, and/or Whole Genome SNP analyses, are needed to confirm this finding. Moreover, according to our proposed pathway scenarios, C. odorata was first introduced to San Cristobal and/or Santa Cruz from mainland Ecuador. After these initial introductions, C. odorata appears to have arrived to Isabela and Floreana from either San Cristobal or Santa Cruz. Here, we report the first genetic study of C. odorata in the Galapagos and the first attempt to unravel the invasion history of this species. The information obtained in this research could support management and control strategies to lessen the impact that C. odorata has on the islands' local flora and fauna.

How far can it go? Tolerance of seeds and seedlings of an invasive tree to water deficit and high temperatures

How far can it go? Tolerance of seeds and seedlings of an invasive tree to water deficit and high temperatures

Higher tree species richness and diversity in urban areas than in forests: Implications for host availability for invasive tree pests and pathogens

Urban and forest trees provide valuable ecosystem services. However, they are increasingly threatened by invasive forest pests and pathogens. Trees in urban areas are often the first potential hosts non-native tree-feeding insects and tree pathogens (“pests”) encounter after introduction in a novel region. If the trees encountered are suitable hosts, these pests can establish and become invasive – eventually also in surrounding forests. Here, we compared tree species and genus composition between urban areas and surrounding forests and examined the implications for host availability for forest pests and potential effects on invasibility. We compiled and standardised 26 urban tree inventories, containing ∼ 500.000 individual trees. We used multivariate analyses to compare urban tree composition with forest tree composition from forests surrounding each municipality (10 km radius), derived from the Swiss National Forest Inventory. With > 1300 different tree species, species richness of urban trees was 17 times higher than species richness in surrounding forests. Linear models and multivariate analyses revealed that host availability for forest quarantine pests is significantly higher in urban areas than in forests, with large differences in host suitability for different quarantine pests between urban and forest tree assemblages. This indicates that differences in species composition in urban and forest trees can result in increased host availability, possibly facilitating the establishment of quarantine forest pests.

Allelochemicals of the invasive tree species Senna spectabilis alleviate antioxidant enzyme activities in native plants of Western Ghats

Allelochemicals of the invasive tree species Senna spectabilis alleviate antioxidant enzyme activities in native plants of Western Ghats

Трансформація оселищ і її вплив на зообіоту

The history of the use of the term “habitat” is considered. It is emphasized that this term refers to the habitat of a particular animal species or population and is determined by their ranges. The factors that lead to the destruction of habitats of many populations on the lowlands and in the highlands of the Ukrainian Carpathians are indicated. Attention is drawn to the degradation of mountain lakes and streams as habitats for aquatic hydrobionts. Among the factors that cause the destruction of habitats, the factors of both natural and anthropogenic origin are identified: climate change, absolute protection of territories, demutational processes, uncontrolled recreation activities, changes in traditional land use, water chemiсal composition and pollution, the appearance of invasive plants, urbanization, etc. The synergistic effect of these factors leads to rapid habitat change, and thus to the loss of adaptive capacity of individuals of different species to the changed conditions of their habi­tats. Among the objects of our study are such taxa as planktonic crustaceans (Cladocera), ants (Formicidae), lampreys (Cyclostomata), ray-finned fish (Actinopterygii), amphibians (Amphibia) and birds (Aves). It was found, in particular, that deciduous forest habitats are the most favorable for the existence of a significant diversity of ants. The mega-habitats for amphibians were identified as a complex of individual habitats that vary during the vegetation season and are connected by migration routes. The key habitat in Western Polissia, as an example, can be the Unychi wetland, which is home to a number of rare bird species. The nest-building behavior of birds under the influence of anthropogenic factors also undergoes changes - its species-specific appearance and composition of nesting materials are transformed in response to habitat pollution. In addition, the study showed that the use of invasive trees and shrubs for urban greenery has a negative impact on the diversity of urban bird fauna, as it paradoxically reduces the number of nesting and foraging habitats for birds. It is proposed to identify key habitats for the populations of rare and endangered animal species within the protected areas and on the non-protected ones, to indicate their locations and the type of management approach (protection, restoration, reconstruction, etc.).

Response of ectomycorrhizal fungi to full and selective removal of an invasive tree in riparian woodland

The Brazilian pepper tree (Schinus terebinthifolius) is an invasive species that requires significant disturbance to eradicate. Previous studies have identified associations between the Brazilian pepper tree and ectomycorrhizal fungi (EMF). However, limited research has explored the connection between disturbance from removal and the effect on EMF. This study investigated the sensitivity of EMF and the broader fungal community to the full and selective removal of the Brazilian pepper tree. During the selective removal of Brazilian pepper tree, we examined the mycorrhizal community of the Arroyo willow (Salix lasiolepis) to assess the influence of the restoration disturbance on native species. We used ITS2 sequencing to identify the EMF present during the restoration. Our expectation was that both removal efforts would reduce the presence of EMF. Contrary to our predictions, full removal increased EMF richness and relative abundance in the soil. As anticipated, selective removal reduced the richness and relative abundance of EMF associated with soil. Selective removal led to a decrease in the richness of EMF in arroyo willow roots with no effect on relative abundance. Moreover, fungal community composition in soil and roots shifted significantly during selective and full removal. However, the community composition of EMF, specifically, remained constant across treatment types. During full removal efforts, the application of organic soil amendments may have contributed to the increase in the diversity and relative abundance of EMF. Selective removal will require additional measures, such as soil amendments, to curtail the loss of EMF.