Invasive Shrub Research Articles

Current status of the invasive shrub Berberis julianae C.K. Schneid. (Berberidaceae) in Golden Gate Highlands National Park (Free State Province, South Africa)

• Berberis julianae is an alien invasive evergreen shrub in South Africa. • Surveys were conducted to determine effectiveness of previous control interventions. • Cut-stump and chemical treatment were effective for controlling adult plants. • Seedling numbers increased significantly over 6 years after initial control. • Follow-up control should be implemented immediately to stop spread. Berberis julianae commonly known as Wintergreen barberry or Chinese barberry, is an evergreen shrub species native to China which has been introduced into South Africa and has become invasive in a few locations. In 2015, management measures were taken in an attempt a control a population in Golden Gate Highlands National Park (GGHNP) in the Free State Province. After assessing the plant demographics within the park, the following management options were implemented: cut stump treatments of larger shrubs, foliar spray herbicide applications and hand pulling of seedlings. It was recommended that follow-up research be conducted to check if control measures were successful or not. This study aimed to map and determine the current distribution of B. julianae in GGHNP and to investigate the change in B. julianae population demographics to that recorded previously. The study showed that the number of seedlings had multiplied from 6 seedlings in 2014 to 588 in 2020, whereas the number of mature shrubs had decreased in the same time period. In conclusion, the control measures conducted have been successful in reducing the adult population, however, additional follow-up control of seedlings is urgently required to stop further spread.

Habitat management to reduce competitive interactions: case study of native and invading cottontails

AbstractHabitat management recommendations are often based on best available science determined through retroductive and inductive hypotheses. Such recommendations are not frequently tested, potentially resulting in the implementation of unreliable practices for management of imperiled species. The New England cottontail (Sylvilagus transitionalis) is an imperiled shrubland‐obligate species whose recovery efforts include habitat management and restoration. Researchers suggest former best management practices for the species may result in ecological traps and new recommendations have been developed. We evaluated these newly revised best management practices designed to retain higher tree canopy closure to promote New England cottontails without encouraging eastern cottontails (Sylvilagus floridanus). We compared New England and eastern cottontail density between management plots (tree canopy thinned with all downed trees left on the ground, with or without invasive shrub treatment) and control plots (unmanaged) and examined the influence of management on resource selection and survival. Management strategies retaining higher canopy closure promoted stronger selection by New England cottontails than by eastern cottontails. Catch per unit effort of New England cottontails was greater than for eastern cottontails in management plots (P = 0.002). For both species, the proportion of the 95% home range overlapping managed areas was greater than the proportion of managed area in the habitat patch; however, for the 50% core area of the home range, this was only true for New England cottontails. When post‐treatment canopy cover was >75%, New England cottontails selected canopy‐thinning treatments without invasive shrub removal over unmanaged areas, but selection by eastern cottontails was unaffected by management treatment or canopy cover. Survival probability of both species was high and uncorrelated with time spent in management areas. Survival probability decreased as the average distance a rabbit moved in a 7‐day period increased. Our results illustrate the need to revise management strategies that emphasize eliminating canopy cover when improving New England cottontail habitat is an objective, particularly where they are sympatric with eastern cottontails.

Trait responses of a grassland shrub invader to altered moisture regimes

PurposeWe sought to identify plant traits important for initial establishment of a globally invasive shrub, Prosopis spp. (mesquite), by quantifying morphological and ecophysiological responses of seedlings to contrasting moisture regimes. Our model plant was Prosopis velutina, a prominent invader of North American semi-desert grasslands.MethodsSeedlings received one of three watering levels corresponding to regional ‘ambient’ (100%), ‘dry’ (−65%; 65% reduction of ambient), and ‘wet’ (+165%; 65% increase above ambient) growing season precipitation regimes. A total of 32 plant performance (e.g., biomass and growth) and functional (e.g., morphological and physiological) traits were assessed when seedlings reached 11- and 22-days old.ResultsGermination under dry conditions was high (72%) and only slightly reduced compared to ambient and wet conditions with subsequent seedling survival unaffected. High trait variation enabled early recruitment over the range of soil moisture conditions, including extreme drought. Root volume, surface area, tips, tap root length, and leaf length functional traits were top predictors of seedling performance, with fresh weight, absolute growth rate, and root mass secondarily contributing to establishment.ConclusionNo physiological functional traits were significant in predicting performance or discriminating between moisture regimes; suggesting morphological traits for maintaining metabolic and hydraulic function are key to early establishment. Dry conditions reduced germination and slowed P. velutina seedling growth but did not prevent early establishment. Thus, recruitment of certain dryland shrubs may not be episodic with respect to above-average rainfall. Indeed, early recruitment of P. velutina and functionally similar species can potentially occur even in moisture conditions well below-average.

Shrub encroachment drives different responses of soil respiration to increased precipitation and N enrichment

In the context of global change, changes in precipitation patterns and increases in atmospheric nitrogen (N) deposition have important impacts on grassland ecosystem processes and functions, such as soil respiration. However, most studies on the effects of increased precipitation and N enrichment on soil respiration have focused on pure grassland vegetation types (such as typical steppe), but less on grassland at different stages of shrub encroachment. Here, we examined the effects of increased precipitation and N enrichment on soil respiration and its components (heterotrophic and autotrophic respiration) in different stages of shrub-encroached steppe (i.e., no shrub invasion, light, moderate and severe encroachment) based on water and N addition experiments. Our results showed that increased precipitation greatly promoted soil respiration in typical steppe, lightly and moderately shrub-encroached steppe, but had no significant effects in severely encroached steppe; particularly, soil respiration in a wet year (2021) was significantly higher than that in a dry year (2020). However, N addition had no significant effect on soil respiration across the four stages of shrub encroachment, mainly due to the severe soil water limitation. In general, shrub encroachment significantly reduced soil respiration in Inner Mongolia steppe, mainly by increasing soil temperature, but decreasing soil moisture, microbial biomass and root biomass. We found that the driving factors of soil respiration varied with the development of shrub encroachment, especially the biological factors gradually shifted from aboveground plant community to underground microbial community. These findings have important implications for assessing carbon emissions from arid and semi-arid grasslands under global change. Considering that the effects of increased precipitation and N deposition on shrub-encroached steppe (especially severely encroached steppe) were different from those of typical steppe, the stage of shrub encroachment should be fully considered when constructing carbon cycle models to accurately evaluate the carbon emissions of degraded grassland.

Woody seedling community responses to deer herbivory, introduced shrubs, and ash mortality depend on canopy competition and site wetness

Emerald ash borer (EAB) (Agrilus planipennis), non-native shrubs, and white-tailed deer (Odocoileus virginianus) have been independently shown to affect woody seedling communities. Our objective was to determine the relative importance as well as additive and interactive-effects of these stressors in the context of two environmental factors, canopy tree competition and site wetness. We sampled 24 sites, representing three natural non-congruent gradients in ash mortality, deer browse, and introduced shrub invasion. We explored the responses of seedling species abundance, diversity and richness to an array of deer herbivory, ash mortality, and introduced shrubs and varying levels of canopy tree competition, site wetness. The effects of each stressor on the differences in the relative abundance of seedling species was also evaluated. Our results indicate a persistent negative effect of non-native shrubs in drier forest plots on native seedling abundance, richness, and diversity. In wetter forests, non-native shrubs had no effect on native seedling richness or abundance and were positively related to diversity. Deer browse had a negative effect on seedling diversity in wetter forests and no effect in drier forests. Canopy tree competition had a positive effect on seedling diversity in drier forest plots, but negatively affected diversity in wetter forest plots. Ordination analysis revealed that site wetness, non-native shrubs and the total basal area of trees in the stand had the largest impacts on the species composition of seedlings found at each site. Our results suggest that site wetness and chronic stressors like deer and introduced shrubs are interacting to shift seedling communities towards fewer native species as well as to reduce seedling species richness and diversity.

Growth form and functional traits influence the shoot flammability of tropical rainforest species

Canopy fires are increasing globally with anthropogenic climate and land-use changes, even in fire-sensitive rainforest ecosystems. Identifying the ecological drivers that may be aiding canopy fires, such as species or growth form flammability, is crucial to recognising and mitigating fire risks. To address this, we quantified the shoot-flammability of 124 rainforest plant species using an experimental approach. We compared three flammability measures (burnt biomass, total burn time and maximum temperature reached) with plant functional traits across seven different growth forms (i.e., canopy, pioneer, and understory trees; pioneer, understory and invasive shrubs, and vines) and nine common plant families and other higher-level clades, such as conifers, hereafter abbreviated to families. From burning > 600 sun-exposed shoots, we found trees were higher in flammability than shrubs and vines, and the plant families: Sapindaceae, Proteaceae, Fabaceae, and Lauraceae, had especially high flammability, whereas Moraceae was very low. Of the functional traits examined, leaf dry matter content was consistently and significantly positively associated with species flammability. Invasive shrubs as a group were not particularly flammable, although there were exceptions, e.g., wild tobacco (Solanum mauritianum) was highly flammable. This study has two important implications for the management of fire in rainforests. First, we have demonstrated that many tropical rainforest trees may readily burn under severe fire conditions if fire were to reach the rainforest canopy. Second, a large proportion of the > 1 million rainforest trees planted in the Wet Tropics under restoration planting schemes are from our most flammable rainforest plant families, as these families are often recommended for their carbon sequestration potential. Hence, these plantings may be highly vulnerable to fire and if planted along the borders of primary forest they may carry fire into their canopies. Therefore, where fire risk is high, we recommend planting species with low flammability along borders of plantings and forests to act as ‘green firebreaks’ to reduce the risk of fire incursions.

Mapping an alien invasive shrub within conservation corridors using super-resolution satellite imagery

Alien invasive plant species are one of the main drivers of global biodiversity loss. Methods for monitoring the spread of alien invasive plants are needed to improve management and mitigate impact on local biodiversity. Recent advances in deep learning and image fusion holds great potential for mapping and managing alien invasive plants. One such method is super-resolution image reconstruction, where a neural network learns to downscale images from coarse to fine resolution. Within the commercial timber production landscape of KwaZulu-Natal, endangered grassland corridors are threatened by American bramble invasion, impacting plants, birds, arthropods, and soil restoration. Here we aim to improve our understanding of bramble invasion dynamics through using super-resolved satellite mosaics. Bramble was classified with very high accuracies (85%) from the super-resolved satellite mosaic, compared to other conventional satellite imagery with different spectral and spatial resolutions. Using landscape analyses, we identified plantation tree harvesting and prescribed burning to be major drivers increasing bramble cover within the landscape. Bramble cover was highest one year following plantation tree harvesting. Continuous prescribed burning positively influenced bramble. Bramble cover was also high close to streams, and under future invasion projections, bramble will severely impact Ensifera species alongside low priority grasshopper species habitat. Results also indicate that bramble has a significant negative impact on intermediate priority grasshoppers and plant species richness. For controlling bramble invasion within commercial timber production landscapes, we recommend the adoption rotational harvesting, as harvesting entire plantation blocks throughout the landscape will dramatically increase invasion potential of bramble. Current bramble removal programmes should prioritize riparian areas. Special attention is needed to control bramble one year after timber harvesting, as this is when bramble cover is highest. We show the benefits of using super-resolved mosaics to gain new insights into alien invasive species dynamics, while further development of this technique will aid in managing invasive alien plant species at local scales.

Potential of invasive shrubs for energy applications in Uganda

Potential of invasive shrubs for energy applications in Uganda

Fuel trait effects on flammability of native and invasive alien shrubs in coastal fynbos and thicket (Cape Floristic Region).

In June 2017, extreme fires along the southern Cape coast of South Africa burnt native fynbos and thicket vegetation and caused extensive damage to plantations and residential properties. Invasive alien plants (IAPs) occur commonly in the area and were thought to have changed the behaviour of these fires through their modification of fuel properties relative to that of native vegetation. This study experimentally compared various measures of flammability across groups of native and alien invasive shrub species in relation to their fuel traits. Live plant shoots of 30 species (10 species each of native fynbos, native thicket, and IAPs) were sampled to measure live fuel moisture, dry biomass, fuel bed porosity and the proportions of fine-, coarse- and dead fuels. These shoots were burnt experimentally, and flammability measured in terms of maximum temperature (combustibility), completeness of burn (consumability), and time-to-ignition (ignitability). Multiple regression models were used to assess the relationships between flammability responses and fuel traits, while the Kruskal-Wallis H test was used to establish if differences existed in flammability measures and fuel traits among the vegetation groups. Dry biomass significantly enhanced, while live fuel moisture significantly reduced, maximum temperature, whereas the proportion of fine fuels significantly increased completeness of burn. Unlike other similar studies, the proportion of dead fuels and fuel bed porosity were not retained by any of the models to account for variation in flammability. Species of fynbos and IAPs generally exhibited greater flammability in the form of higher completeness of burn and more rapid ignition than species of thicket. Little distinction in flammability and fuel traits could be made between species of fynbos and IAPs, except that fynbos species had a greater proportion of fine fuels. Thicket species had higher proportions of coarse fuels and greater dry biomass (~fuel loading) than species of fynbos and IAPs. Live fuel moisture did not differ among the vegetation groups, contrary to the literature often ascribing variation in flammability to fuel moisture differences. The fuel traits investigated only explained 21–53% of the variation in flammability and large variation was evident among species within vegetation groups suggesting that species-specific and in situ community-level investigations are warranted, particularly in regard fuel moisture and chemical contents.

Livestock Grazing Impact on Species Composition and Richness Understory of the Pinus cembroides Zucc. Forest in Northeastern Mexico

In the pine forests of Mexico, disturbances are primarily due to cattle, horses, goat, and sheep grazing, particularly in communal grazing lands. The most evident disturbances are low tree recruitment, invasive shrubs establishment, species composition changes, and invasion of weeds dispersed mainly by livestock. The Sierra de Zapalinamé is a mountain range and natural protected area of northeast Mexico. We conducted the current study in this area in a forest stand of Pinus cembroides excluded from grazing in the last 25 years (1200 ha with pine forest vegetation and mountain chaparral) and another area nearby subjected to livestock grazing. Forest structure (basal area and density), tree species richness, total understory species richness, and understory species composition were analyzed at the control and grazed sites. Our results revealed that grazing has modified the understory species composition and reduced the evenness in the control plots. Therefore, to maintain species diversity and forest structure, we concluded that extensive grazing should be restricted for some areas or the number of animals reduced in zones of high ecological value.

Plant invasion modifies isohydricity in Mediterranean tree species

Abstract Understanding of plant hydraulic strategies (i.e. the degree of iso‐/anisohydricity) is crucial to predict the response of plants to changing environmental conditions such as climate‐change induced extreme drought. Several abiotic factors, including evaporative demand, have been shown to seasonally modify the isohydricity of plants. However, the impact of biotic factors such as plant–plant interactions on hydraulic strategies has seldom been explored. Here, we investigated adaptations and changes in hydraulic strategies of two woody species in response to seasonal abiotic conditions, experimental drought and plant invasion in a Mediterranean cork oak (Quercus suber) ecosystem with a combined shrub invasion (Cistus ladanifer) and rain exclusion experiment. From the dry to wet season, Q. suber shifted from a partial isohydric to an anisohydric behaviour while C. ladanifer shifted from strict anisohydric to partial isohydric. During drought, water competition by plant invasion significantly modified the hydraulic strategy of invaded Q. suber, which was accompanied by lower pre‐dawn leaf water potentials, sap flow density, leaf area index and trunk increment rates. This altered isohydricity of invaded Q. suber trees was most likely caused by interspecific competition for water resources by water spending C. ladanifer shrubs. Both species do have the highest proportion of fine roots in the topsoil and thus, an additional water consumer, such as C. ladanifer can lead to more stressful conditions for Q. suber during times of water scarcity. Further underlying mechanisms of the altered isohydricity of Q. suber, such as potential allelopathic effects of C. ladanifer exudates on root growth of Q. suber, have to be investigated in the future. In conclusion, we demonstrate that the degree of isohydricity of two woody Mediterranean plant species is dynamically determined by the interplay of species‐specific hydraulic traits and their abiotic and biotic environment. Read the free Plain Language Summary for this article on the Journal blog.

Soil VOC emissions of a Mediterranean woodland are sensitive to shrub invasion.

Many belowground processes, such as soil respiration and soil-atmosphere VOC (volatile organic compounds) exchange, are closely linked to soil microbiological processes. However, little is known about how changes in plant species cover, i.e. after plant invasion, alter these soil processes. In particular, the response of soil VOC emissions to plant invasion is not well understood. We analysed soil VOC emissions and soil respiration of a Mediterranean cork oak (Quercus suber) ecosystem, comparing soil VOC emissions from a non-invaded Q. suber woodland to one invaded by the shrub Cistus ladanifer. Soil VOC emissions were determined under controlled conditions using online proton-transfer time-of-flight mass spectrometry. Net soil VOC emissions were measured by exposing soils with or without litter to different temperature and soil moisture conditions. Soil VOC emissions were sensitive to C. ladanifer invasion. Highest net emission rates were determined for oxygenated VOC (acetaldehyde, acetone, methanol, acetic acid), and high temperatures enhanced total VOC emissions. Invasion affected the relative contribution of various VOC. Methanol and acetaldehyde were emitted exclusively from litter and were associated with the non-invaded sites. In contrast, acetone emissions increased in response to shrub presence. Interestingly, low soil moisture enhanced the effect of shrub invasion on VOC emissions. Our results indicate that shrub invasion substantially influences important belowground processes in cork oak ecosystems, in particular soil VOC emissions. High soil moisture is suggested to diminish the invasion effect through a moisture-induced increase in microbial decomposition rates of soil VOC.

Herbicide control of the invasive Amur honeysuckle (Lonicera maackii) does not alter soil microbial communities or activity

Abstract Invasive plants are a major problem for land managers and have widespread and lasting environmental impacts. The invasive shrub Amur honeysuckle (Lonicera maackii) is a pervasive and noxious plant in the Midwest region of the United States. Despite this, many land managers may be uncomfortable with herbicide control of this and other invasive plants due to unknown impacts on ecosystem components including soils. To examine if herbicide control of Amur honeysuckle impacts soil enzyme activity and soil communities, we treated Amur honeysuckle with Garlon® 4 (triclopyr) suspended in Basal Bark Oil, Basal Bark Oil alone and untreated controls, then assessed soil community, soil enzyme activity and arbuscular mycorrhizal density changes among treatments and across the subsequent growing season. We found that basal bark herbicide treatments of Amur honeysuckle do not negatively impact soil enzyme activity, nor do they impact fungal, prokaryotic or oomycotan diversity or community structure. There was a slight but likely ecologically unimportant effect on community structure associated with basal bark oil applications, but not with herbicide applications. Arbuscular mycorrhizal colonization was negatively affected by herbicide use but this is likely due to reduction in host health and/or mortality. Taken together, this suggests that herbicide control of Amur honeysuckle does not impact soils and land managers can treat these invasive plants without concern for negative soil outcomes.

Effect of Shrub Encroachment on Alpine Grass Soil Microbial Community Assembly

Shrub encroachment is a common phenomenon in grasslands all over the world. However, little is known about the consequences of shrub encroachment on soil microbial community structure in different layers. We investigated the effects of three common shrub encroachment (Potentilla fruticosa, Spiraea alpina, and Caragana microphylla) on grassland soil bacterial communities at the surface and deep layers in Qinghai–Tibetan Plateau. 16S rRNA gene sequencing was used to investigate the bacterial communities, and Fourier translation infrared spectroscopy (FTIR) was conducted to assess the soil organic carbon (SOC) chemical composition in surface and deep layers of shrub-encroached alpine grassland. Shrub encroachment has significantly increased SOC degradation in deep layer. After shrub invasion, the bacterial alpha-diversity in the surface and deep soil was higher than in grassland soil (except for the surface layer of C. microphylla). Factors driving bacterial community changes in soil surface and deep layer were different. Among the soil properties that were measured, SOC content was the primary factor that altered soil bacterial community composition in surface soil, while SOC chemical composition (aromatic and polysaccharides) was the main driver in the deep layer. A total of 39 and 42 biomarkers were found by linear discriminant analysis (LDA) effect size (LEfSe) in the surface and deep soil layer among the four sampling groups, respectively. Phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) showed that the most abundant predicted functional genes belonged to categories of metabolism (52.83%) in the primary metabolic pathway. Redundancy analysis (RDA) results also showed that the key factors affecting bacterial metabolic function appear to be SOC, pH, and aromatics, which are largely consistent with those affecting community composition. We suggest that shrub encroachment affect the structure, diversity, and predicted functions of bacterial communities, thus affecting the C cycle in this region.

Identification of Anti-Proliferative Compounds from Genista monspessulana Seeds through Covariate-Based Integration of Chemical Fingerprints and Bioactivity Datasets.

Genista monspessulana (L.) L.A.S. Johnson (Fabaceae) is a Mediterranean plant introduced to South America and other regions for ornamental purposes. However, it is considered an invasive shrub due to its reproductive vigor in many areas. Unlike other Genista plants, G. monspessulana has few studies disclosing its biologically active components, particularly cytotoxic agents against cancer cells. Thus, as part of our research on anti-proliferative bioactives, a set of ethanolic seed extracts from ten accessions of G. monspessulana, collected in the Bogotá plateau, were evaluated against four cell lines: PC-3 (prostate adenocarcinoma), SiHa (cervical carcinoma), A549 (lung carcinoma), and L929 (normal mouse fibroblasts). Extracts were also analyzed through liquid chromatography coupled with mass spectrometry (LC/MS) to record chemical fingerprints and determine the composition and metabolite variability between accessions. Using multiple covariate statistics, chemical and bioactivity datasets were integrated to recognize patterns and identify bioactive compounds among studied extracts. G. monspessulana seed-derived extracts exhibited dose-dependent antiproliferative activity on PC-3 and SiHa cell lines (>500 µg/mL < IC50 < 26.3 µg/mL). Seven compounds (1–7) were inferred as the compounds most likely responsible for the observed anti-proliferative activity and subsequently isolated and identified by spectroscopic techniques. A tricyclic quinolizidine (1) and a pyranoisoflavone (2) were found to be the most active compounds, exhibiting selectivity against PC-3 cell lines (IC50 < 18.6 µM). These compounds were used as precursors to obtain a quinolizidine-pyranoisoflavone adduct via Betti reaction, improving the activity against PC-3 and comparable to curcumin as the positive control. Results indicated that this composition–activity associative approach is advantageous to finding those bioactive principles efficiently within active extracts. This correlative association can be employed in further studies focused on the targeted isolation of anti-proliferative compounds from Genista plants and accessions.

Compositional attributes of invaded forests drive the diversity of insect functional groups

Forest canopies are important habitats for animal biodiversity globally. The structural and compositional components of canopies influence biodiversity, and recent advancements in remote sensing have given insight to these relationships. As invasive shrubs alter both the structure and composition of forests, we use handheld, mobile LiDAR to relate these elements and the overarching tree composition to insect biodiversity in Georgia, USA. Both LiDAR-derived structural metrics (vegetation density and Shannon vertical complexity index) were related to invasive shrub cover. We sampled four insect functional groups using two methods: woodboring beetles, mycophagous beetles, and bees were sampled using flight intercept traps 5 m aboveground, while litter-foraging ants were sifted from leaf-litter. From our generalized linear models, we found that tree composition strongly influenced all groups, though responses varied among functional groups. Woodboring beetles were negatively influenced more strongly by invasive shrub cover than vegetation density and also responded positively to tree and deadwood diversity. By contrast, bees and mycophagous beetles were unaffected by both the structure and composition of invasive shrubs, but were sensitive to tree composition. In the leaf-litter, ants were negatively influenced by invasive shrub cover and were sensitive to tree composition. Thus, the composition of forests is an important driver of insect diversity in our system, but with idiosyncratic responses among functional groups. Our results demonstrate the utility of LiDAR in clarifying the relationship between structure and composition on biodiversity in forest canopies, especially in regards to invasive plants.

The native avian species visiting fruiting invasive Lantana camara in KwaZulu-Natal, South Africa: Potential dispersal concerns

Alien invasive plant species are a major problem globally, threatening ecosystem functioning and biodiversity. Native bird species facilitate their spread through mutualistic relationships. Studies of seed dispersal of alien invasive plants are important for effective management. In the present study, we investigated the role of native bird species in the potential dispersal of the highly invasive shrub Lantana camara in KwaZulu-Natal, South Africa. We observed a total of 56 native bird species visiting fruiting L. camara with only 28 (50 %) species consuming the fruit. Visitation frequencies were significantly higher for small and medium-sized frugivorous species. The dark-capped bulbul Pycnonotus tricolor was the frugivorous bird species most observed visiting and is likely the main potential native avian disperser of L. camara. Interestingly, two non-frugivorous birds, the white-bellied sunbird Cinnyris talatala and the white-browed scrub-robin Cercotrichas leucophrys showed relatively high visitation frequencies to L. camara. Our study showed that L. camara benefits from seed dispersers and pollinators for seed reproduction and spread. These results emphasise the importance of evaluating the role of native bird species in the dispersal of alien invasive species.

Invasive shrub Lantana camara L. alters the flora and soils in tropical dry deciduous forests of Central India

AbstractLantana camara (hereafter Lantana) is a highly noxious invasive weed species of global concern. However, its impacts on floristic and soil properties in tropical dry deciduous forests are elusive and fragmented. We aimed to assess the changes in the flora and soil properties following the invasion by Lantana in Central Indian forest ecosystems. Three study sites were selected, and each site was further divided into two subsites: Lantana‐invaded (LI) and uninvaded (UI). In total, 60 plots of 0.25 ha each (10 plots in each subsite) were laid randomly. Within each plot, floristic structure, composition, diversity, soil organic carbon (SOC), soil total nitrogen (STN), moisture (M%), pH, and bulk density (BD) were assessed. Lantana‐invaded sites showed a significant decrease in density (D), basal area (BA), species richness (SR), and evenness (E) of saplings (&lt;3 cm diameter at breast height [DBH]), juveniles (between 3 and 9.9 cm DBH), and herbs. In LI sites, a reduction of 57% and 25% was observed in lower DBH class of trees (saplings and juveniles). In all the LI sites, significant increase in SOC, STN, and M%, and a significant decrease in pH were recorded. Lantana may greatly impact the vegetation and soil properties, and successively, these strong changes may increase its invasive potential and ability to replace native species by averting their natural regeneration potential. Therefore, a proper management strategy of this noxious weed is imperative to prevent its further expansion and future problems.

The short-term and long-term effects of honeysuckle removal on canopy structure and implications for urban forest management

Riparian forests across the continental United States are heavily invaded by Amur honeysuckle (Lonicera maackii (Rupr.)), an invasive shrub which suppresses native plants, homogenizes community structure and composition, and alters ecosystem processes. However, no studies have quantified the impacts of honeysuckle removal on forest canopy structure across the first decade of restoration. In this study we used a portable canopy LiDAR (PCL) to characterize the immediate (<1 year), short-term (1–2 years) and long-term (>10 years) impacts of honeysuckle removal on the horizontal and vertical complexity of canopy structure in 5 heavily invaded riparian forests in Ohio. Within two years of removal, forest canopies had a 40% reduction in canopy leaf volume, a greater average height of maximum canopy density, and increased aggregation of the remaining leaf area around trees than pre-removal conditions. Honeysuckle removal also prompted long-term (>10 years) increases in canopy structural complexity, but only in areas with initially high honeysuckle abundance and low native tree density. Honeysuckle cover had a much stronger influence on canopy structure than either its basal area or stem density. Our results suggest that removing honeysuckle from heavily-invaded stands can promote complex canopy structure over the long-term that is beyond the short-term accrual immediately following disturbance, but might depend on initial stand conditions.

Seed dispersal by frugivores and germination of the invasive alien shrub Pyracantha angustifolia (Franch.) C.K. Schneid. in Free State Province, South Africa

Seed dispersal by frugivores and germination of the invasive alien shrub Pyracantha angustifolia (Franch.) C.K. Schneid. in Free State Province, South Africa