Abundance Of Invasive Species Research Articles

Increase in the Abundance of Invasive Fish Species in the Ciliwung River, DKI Jakarta and West Java Provinces

The Ciliwung River is one of the important rivers in the Jakarta Special Capital Region (DKI Jakarta) and West Java. The existence of local fish in the Ciliwung River is threatened by the presence of invasive fish. This research aims to identify the types of invasive fish along the Ciliwung River from 2023 to 2024 and compare them with previous research in 2011. The study uses 6 segments according to Minister of Environment and Forestry Decree No. SK.298/Menlhk/Setjen/PKL.1/6/2017. Each segment consists of 3 research plots, totaling 18 research stations. The sampling method involves collecting fish using environmentally friendly fishing gear. The research results show the presence of 10 species from 5 families and 4 non-native fish orders that are invasive. The most abundant invasive fish species in the Ciliwung River are, in order, Plecostomus (Pterygoplichthys pardalis), Mosquito Fish (Gambusia affinis), Guppy (Poecilia reticulata), Platy (Xiphophorus helleri), Nile Tilapia (Oreochromis niloticus), Bristlenose Pleco (Ancistrus temminckii), Glossom (Andinoacara rivulatus), Carp (Cyprinus carpio), Red Devil (Amphilophus labiatus), and African Catfish (Clarias gariepinus). There has been a 100% increase in the number of invasive fish species in the Ciliwung River compared to the 2011 study, which identified only 5 invasive fish species.

The effects of co-invasion by three Asteraceae invasive alien species on plant taxonomic and functional diversity in herbaceous ruderal communities in southern Jiangsu, China.

Invasive alien species can affect plant taxonomic and functional diversity. Multiple invasive alien species can co-invade the same plant community. However, the effects of such co-invasion on plant taxonomic and functional diversity are currently unclear. Our study aimed to estimate the effects of co-invasion by three Asteraceae invasive alien species (i.e., Conyza canadensis (L.) Cronquist, Conyza sumatrensis (S.F. Blake) Pruski and G. Sancho, and Solidago canadensis L.) on plant taxonomic and functional diversity in herbaceous ruderal communities in southern Jiangsu, China. The effects of these three invasive alien species under seven invasion combinations (including invasion by one invasive alien species, co-invasion by two invasive alien species, and co-invasion by these three invasive alien species) on plant taxonomic and functional diversity were investigated in a comparative field study of herbaceous ruderal communities. Niche differentiation mediated the functional divergence between these three invasive alien species and natives under all invasion combinations. These three invasive alien species significantly increased plant taxonomic diversity (especially plant diversity and richness) and plant functional diversity (especially Rao's quadratic entropies) under all invasion combinations. The relative abundance of invasive alien species was significantly positively associated with plant functional diversity (especially community-weighted mean trait values and Rao's quadratic entropy). The number of invasive alien species was significantly positively associated with plant taxonomic diversity (especially plant diversity and richness) and plant functional diversity (especially Rao's quadratic entropies). Thus, co-invasion by these three invasive alien species may synergistically increase plant taxonomic diversity (especially plant diversity and richness) and functional diversity (especially Rao's quadratic entropies).

Extreme precipitation promotes invasion in managed grasslands.

Climate change is increasing the frequency and intensity of extreme events like drought and flooding, which threaten to amplify other global change drivers such as species invasion. We investigate the effect of wet and dry extreme precipitation regimes on invasive species' abundances in northern tallgrass prairies. Because soil moisture is a key determinant of prairie composition, theory and evidence suggest drought conditions will hinder invasion, whereas wetter conditions will enhance invasion. To test this hypothesis, we explored the effect of precipitation on invasive plant species abundance from 2010 to 2019 in 25 managed prairies using observations from 267 transects comprising 6675 plots throughout western Minnesota, USA. We estimated how increases in the number of extremely wet or dry months in a year altered overall invasive species abundance and the abundance of the highly invasive grasses Poa pratensis and Bromus inermis. We found that a greater occurrence of abnormally wet months increased invasive species abundance but found mixed evidence that abnormally dry conditions hindered invasion. Further, more moderately wet and dry months reduced native grass abundance. Together, these results suggest that more frequent extremely wet months may intensify invasive dominance and that dry months may not counterbalance these trends. Given the considerable uncertainty still surrounding the interactive effects of climate change and invasion on native plant communities, this research represents an important step toward quantifying the complex influence of precipitation extremes on invasion dynamics in managed ecosystems of critical conservation concern.

Globally invasive Potamopyrgus antipodarum (Gray, 1843) – an indicator of the degraded water systems in relation to native aquatic invertebrates

Global changes in climate and human impact favour invasions of aquatic organisms. Along with habitat modification, the abundance of invasive species might increase, leading to their greater impact on ecosystems functioning in disturbed areas. The appearance of species, which are drivers for ecosystem pollution are useful tool for the indication of some environmental changes in the area. We examine the occurrence of P. antipodarum populations, a global invader that established rivers, oxbow lakes, dam reservoirs, sand pits, gravel pits, and subsidence ponds in Poland (Central Europe). The research aims were to determine the extent of invasion in anthropogenically impacted habitats and the relationship between the abundance of aquatic invertebrates and oxygen concentration, pH, N-NO2, N-NO3, chlorides, and ammonia. This investigation helps elucidate the potential of invader to adapt to adverse environmental conditions in aquatic systems in which it was found dominant. The abundance of P. antipodarum showed an unimodal distribution, being higher in disturbed conditions. In snail communities it was a supereudominant or eudominant species in rivers, gravel pits, sand pits and subsidence ponds. Its relative abundance was the highest in gravel pits, in which it constituted more than 50 percent of benthic fauna. We demonstrated that environmental disturbances and pollution increase the vulnerability of water biocoenoses to invasions and the origin of free niches and that P. antipodarum is an indicator of degraded water systems. Results support the management of aquatic systems colonized by invasive species and highlight the need to assess the level of pollution discharged to prevent their dispersion. Management priorities must include the reduction or halt of invader spread because new aquatic environments are and will be created in industrial areas of the world.

Limited top–down effects of feral cats on rodent dynamics in a seabird colony

Control of invasive predators is a priority to protect island biodiversity. Understanding the responses of other species in multi-species invaded food webs is important to avoid unintended consequences. We use an intensive 2-year cat-trapping program in the vicinity of seabird colonies on Bruny Island, Tasmania, to investigate its effectiveness in reducing feral cat density and whether cat control influenced the behaviour and abundance of native and invasive mammal species. Cat density before control was extremely high around this seasonally rich food resource, much higher than on mainlands. Cat density was reduced 5.4-fold by control showing that trapping is effective in reducing cat density in this focussed landscape context. We found no direct effect of cat reduction on the abundance or behaviour of native or invasive mammalian prey species. Recruitment of invasive black rats and native swamp rats increased on the seabird colonies after the shearwater breeding season, and cats responded by increasing their presence on the colonies relative to surrounding areas. This suggests cascading bottom-up effects from a lagged productivity pulse provided by breeding seabirds which would require nutrient sampling to confirm. Our results highlight the complexity of subsequent effects of an invasive predator control on the broader ecosystem.

Coexistence and Spatial Distribution of Invasive and Sylvatic Container-Breeding Mosquitoes in City–Forest Ecotone within the Brazilian Semi-arid

Aedes species are vectors of the most significant arboviruses in Brazil with the greatest health and economic impact in the country. However, little is known about the factors that influence the distribution of Aedes, as well as other container-breeding mosquitoes, especially on the border between urban and forest environments. Here, we tested the effect of three phytophysiognomies within the city–forest ecotone in the Brazilian semi-arid region on the spatial distribution of vector mosquitoes. We also investigated the effect of rainfall on the spatial distribution and abundance of mosquitoes and described the interspecific interactions between invasive and native mosquito species. Immatures were sampled during the rainy seasons of 2019–2020 (October 2019 to February 2020) and 2020–2021 (November 2020 to February 2021). In each sampled location, 30 ovitraps were installed in shaded areas. There was a predominance of the Aedes mosquitoes, especially Ae. albopictus and Ae. aegypti, while three species of Haemagogus (Hg. spegazzinii, Hg. janthinomys and Hg. leucocelaenus) were rarely found. The sylvatic mosquito Ae. terrens was abundant in areas with lower anthropic influence and during higher rainfall regimes with minimal pluviometric variation. This rainfall was also favorable for the presence of the predatory mosquito larvae Toxorhynchites theobaldi. The abundance of invasive Aedes species showed positive correlations with each other and negative correlations with the sylvatic Ae. terrens. Our results demonstrate that human occupation and the rainfall regime affect the interactions between invasive and sylvatic species of container mosquitoes.

The temporal abundance-distribution relationship in a global invader sheds light on species distribution mechanisms

The geographic expansion and abundance fluctuations of invasive species offer unprecedented insights to investigate potential mechanisms underlying the distribution-abundance relationship, one of the most universal patterns in community ecology. However, the abundance of invasive species is rarely documented in the needed detail. Data from historical records, scientific and popular literature, citizen science and expert interviews were synthesized to obtain insights into the long-term expansion and abundance cycles of the Chinese mitten crab, one of the world’s 100 worst invasive species. Thus for the first time, global long-term data on population size fluctuations have been correlated with the global spatiotemporal invasion history of a non-native species. Geographic expansions and increases in abundance co-occurred in the 1930s and again since the 1990s in agreement with the distribution-abundance relationship. Furthermore, a regional case study for the German river Elbe indicates that increases in abundance may be driven by improved riverine water quality and rising sea surface temperatures. Environmental restoration and climate change therefore benefit this invasive species, and could lead to further geographic expansion and increases in abundance.

First Short-Term Study of the Relationship between Native and Invasive Earthworms in the Zone of Soil Freezing in Western Siberia—Experiments in Mesocosms

Earthworm invasions often reduce biodiversity and affect the ability of ecosystems to perform ecosystem functions. Over the past few decades, European lumbricid species have spread widely in natural habitats in Western Siberia, without completely displacing the native species. The aim of the present experiment is to study the survival, reproductive potential, vertical distribution, abundance, and biomass of Aporrectodea caliginosa and Lumbricus rubellus invasive species for the region and the native species Eisenia nordenskioldi and their influence on each other. For this purpose, winter and vegetation experiments were conducted in mesocosms simulating the real situation of invasions in the same communities on the same types of soils with the same amount and composition of litter. The authors found that the native species was significantly inferior to A. caliginosa in reproduction rate, number of offspring, and final biomass, but had an advantage over L. rubellus. The native species was positively influenced by the presence of A. caliginosa. In the experiment, there was a significant rejuvenation of the populations of the studied species, as well as an increase in abundance and relative mass under interaction conditions compared to mono variants. The native species had advantages over the invasive species in terms of winter survival. The natural volume of litter used in the experiment was insufficient for L. rubellus. According to the results of the experiment, it can be assumed that the spread of L. rubellus will continue to be limited to non-freezing biotopes rich in organic matter. A. caliginosa will spread in natural communities and agrocenoses of Western Siberia.

Stress-resistant trees are more common in urban than rural forests: A case study of Cleveland, Ohio’s natural parks

Natural parks are comprised of preserved forested natural areas that are undergoing natural ecological processes. These areas can offer a refuge for local biodiversity and contribute substantially to ecosystem services in both rural areas with relatively low population densities, as well as high-density urban areas. Forested natural parks located in urban areas should experience more stressful environmental conditions than nearby rural areas, yet we know relatively little about how urbanization impacts tree communities within these important natural habitats. To better understand the impact of urbanization on forests, we investigated the species composition, abundance, and diversity of midstory and canopy trees as well as tree seedlings in urban and rural natural parks in and around Cleveland, Ohio. We found that both urban and rural natural parks have similar tree abundance, but midstory and canopy trees as well as tree seedling communities in the urban natural parks included higher abundances of stress-tolerant species compared to rural parks. In addition, this pattern was driven by changes in native tree species, as we observed low abundance of invasive species. More stress-resistant native species in urban areas include Quercus rubra and Prunus serotina, in contrast to rural natural parks which are dominated by Acer spp. and Fagus grandifolia. Lastly, we show that urban and rural natural parks have similar species diversity within plots, but we found higher variation in community composition among urban natural parks compared to among rural parks. Furthermore, Q. rubra and P. serotina were significantly larger in rural natural parks, indicating that both environmental stress and successional stage could drive compositional differences. Thus, we show that urbanization can have unexpected effects on plant community composition and diversity. Our study refutes the idea that these are degraded habitats, highlights the need to conserve them, and suggests that characterization of local variation in self-assembled urban tree communities will provide the most accurate picture of their management needs and potential ecosystem services.

Landscape Transformation and Variation in Invasive Species Abundance Drive Change in Primary Production of Aquatic Vegetation in the Sacramento–San Joaquin Delta

Conversion of wetlands in the Sacramento–San Joaquin Delta beginning in the mid-1800s resulted in a pronounced shift from a wetland-dominated food web to one driven by open-water primary producers. Submersed and floating aquatic vegetation (SAV and FAV) now rank highest in potential net primary production (NPP) among producer groups, and provide a comparable amount of carbon to the detrital food web as marshes. However, important details of this contribution that relate to shifts in species composition and habitat extent were not understood. Here, we review how changes in aquatic vegetation influence NPP and trophic support from the historical to modern periods, within the modern period (the last 2 decades), and under future management and climate scenarios. We estimate that NPP of SAV and FAV during the historical period was approximately half that of today, before increases in open water and introduction of the highly productive water primrose. During the modern period (the last 20 years), high interannual variability in the extent and relative composition of aquatic vegetation species has driven significant variation in total NPP. This recent temporal variation is 6 to 13 times larger than projected changes in production from the potential future scenarios we modeled, including a reduction in FAV by 20% through control measures, substantial wetland restoration (and thus increased channel area that could support SAV and FAV), and increased salinity intrusion in the western Delta with climate warming, which favors native species with greater salinity tolerance. Large temporal swings in NPP of SAV and FAV cascade to influence the degree of carbon that flows to consumers through detrital pathways and herbivory. This volatility and interannual inconsistency in aquatic vegetation support of food webs make achieving wetland restoration goals for the Delta—which could lead to recovery of a portion of the NPP lost since historical times—even more imperative.

Twenty Years of Urban Reforestation: Overstory Development Structures Understory Plant Communities in Lexington, KY, USA

Urban forests provide critical ecosystem services in an increasingly urbanized global landscape. The reforestation of undeveloped parcels and serially mowed grasslands can increase urban forest cover, but plant community development in planted urban forests is poorly understood. We conducted a study to elucidate the roles of time since tree planting, invasive species abundance, and other abiotic and biotic site-level factors in structuring understory plant communities within a 20-year chronosequence of planted urban forests in Lexington, KY, USA. We assessed the percent of groundcover of all understory species in fixed-radius plots on the site. Understory herbaceous plant communities demonstrated shifts from graminoid dominance to forb dominance over time, and plant communities in successively younger sites were increasingly dissimilar from that of the 20-year-old site. Invasive plant species were abundant, representing 21% of total groundcover across all surveyed plots, and became increasingly prevalent over time. Understory plant diversity was negatively associated with invasive species abundance. Overall, site factors, including time since planting, forest canopy closure, density of tree and shrub reproduction, and soil pH, accounted for much of the variability among understory communities. Understory plant communities across the chronosequence of planted sites demonstrated apparent structural shifts with overstory canopy development, but the increasing prevalence of invasive species and their negative impacts to plant diversity warrant future management to ensure the continuation of the desired successional trajectories.

The adventive species community changes in the Cheboksary reservoir during 2001-2021

Generally publications devoted to invasive fish species in the Volga-Kama cascade of reservoirs represents relative indicators and do not provide data on the abundance, numbers and invasive communities’ single species dynamics. It does not allow providing a correct assessment of population’s state and changes in the nonindigenous species composition. In this work, changes in the abundance and species structure of the Cheboksary reservoir’s invasive fish community during 2001-2021 were estimated. The total fish count was determined on data of active fishing gears catches and precise reservoir area. Differentiation into mass, widespread and relatively numerous and locally found with a small average abundance species was noted. A decrease in the species evenness of the invasive community was recorded in consequence of the Black Sea-Caspian sprat Clupeonella cultriventris (Nordmann, 1840) and the round goby Neogobius melanostomus (Pallas, 1814) domination rise. The Black Sea-Caspian sprat and the round goby put together for 98.7% of the total number of invasive fish in the current period. Due to this two dominant species there is a tendency to increase the relative abundance of invasive fish species in the reservoir up to 561 unit/ha despite a significant decrease in the abundance of some other invaders.

Land use effects on plant invasion, plant communities and soil properties in Southwestern Nigeria

AimThe objective of this research was to analyze the association between evaluated level of species disturbance between sites as well as determine the abundance and diversity of invasive alien species and the physicochemical parameters of soil samples with the view to determining the impact of mining on the distribution of invasive species. MethodFour Land use types: active mining, abandoned mining, farmland and relatively undisturbed forest were selected as sampling sites for the study. Two 20 m by 20 m sampling plots were randomly selected in each land use types. Plants were identified to assess the floristic composition, the level of colonization of invasive species, and the diversity of the plant species. Soil chemical and physical properties in sites were analysed and plant-soil relationship was determined by means of Canonical correspondence analysis (CCA) and Principal Component Analysis (PCA). ResultDiversity analysis showed that the active mining site was the least diverse and abandoned mining site the most diverse. The characteristics of the populations of the invasive plant species in the mining sites were weeds (10%), shrubs (60%), and climbers (30%). Distribution of invasive species was influenced by the four land use types (active mining, abandoned mining, farming and relatively undisturbed forest). Solanum torvum, Panicum brevifolium, Centrosema pubescens, Commelina erecta were found to be associated with active mining site. Abandoned mining and farming sites had similar composition of invasive species. Soil analysis showed significant difference between total nitrogen, available phosphorus, organic carbon and CEC between undisturbed forest and the active mining sites. Canonical correspondence analysis showed that active mining site was associated with increasing acidity, Na+ and bulk density and characterised by plant species such as Solanum torvum, Panicum brevifolium, Centrosema pubescens, Commelina erecta while undisturbed site was associated with increasing available P, Ca2+, total N, Organic C, CEC and Mg2+ and characterised by species such as Cola hispida, Lecaniodiscus cupanoides, Bahia nitida, Mirodesmis puberula, Monodora tenuifolia. Principal component analysis identified Organic C, Total N and Ca2+ as the most important physico-chemical factors responsible for variations observed in the study. ConclusionThe study concluded that land use has significant effect on soil and is a driver for low plant diversity and introduction of invasive plant species.

Ontogenetic Changes in Nutrients and Stoichiometry in the Invasive Mosquito, Aedes albopictus (Diptera: Culicidae).

A variety of physiological, morphological, and behavioral changes occur throughout the life cycle of mosquitoes, which can be correlated with a shift from the aquatic to terrestrial environment. Aedes albopictus Skuse is an abundant invasive species from Asia that was introduced into the Americas in the 1980's and is responsible for transmitting several important human disease-causing pathogens. How physiological and anatomical changes within each instar and throughout the developmental stages are related to changes in carbon (C) and nitrogen (N) levels are an unexplored area of mosquito ecology. We hypothesized that these changes as well as stoichiometry (C:N) would vary with instar stage and larval diet. Cohorts of larvae were grown in three different diets: animal only (crickets), plant only (red maple leaves), and a mixture containing both types. Larval instars (1st-4th), pupae, and adults were raised in each diet and were separately analyzed for nutrient content (%C, %N) and stoichiometry (C:N). Significant changes in nutrient values occurred across the life cycle, with C:N values being lower in early instars versus adults or pupae, especially in animal only or mixed diets; few differences were detected in %C or %N across ontogeny. This knowledge may lead to a better understanding of mosquito ecology and pathogen transmission.

Impacts of Livestock Grazing on Vegetation and Soil in Lowland Grassland Ecosystem of Nepal

Livestock grazing is one of the largest sectors for land use globally, and contrasting impacts (negative, neutral, and positive) of livestock grazing on vegetation and soil have been observed. In Koshi Tappu Wildlife Reserve (KTWR), livestock grazing is one of the major problems but has been feebly addressed in previous research. This study, therefore, aims to determine the impacts of livestock grazing on vegetation and soil quality in grasslands of core and buffer zones of KTWR. Less grazing intensity was observed at the core zone compared to the buffer zone. Livestock grazing was observed with negative impacts on the richness and diversity of the plant species causing changes in the community assemblages. Invasive plant species richness, however, was found higher in the low grazed areas. Differences in soil pH, phosphorus, and potassium content between high and low grazed areas were not observed. In contrast, soil electrical conductivity, bulk density, and nitrogen content were significantly higher in the high grazed areas. Controlled grazing is recommended at buffer zone grasslands of KTWR to enhance plant diversity and nutrient availability. The core areas of the reserve should be managed for reducing the abundance and distribution of invasive alien plant species.

Predicting the impact of invasive trees from different measures of abundance

Biological invasions produce negative impacts worldwide, causing massive economic costs and ecological impacts. Knowing the relationship between invasive species abundance and the magnitude of their impacts (abundance-impact curves) is critical to designing prevention and management strategies that effectively tackle these impacts. However, different measures of abundance may produce different abundance-impact curves. Woody plants are among the most transformative invaders, especially in grassland ecosystems because of the introduction of hitherto absent life forms. In this study, our first goal was to assess the impact of a woody invader, Pinus contorta (hereafter pine), on native grassland productivity and livestock grazing in Patagonia (Argentina), building abundance-impact curves. Our second goal, was to compare different measure of pine abundance (density, basal area and canopy cover) as predictors of pine's impact on grassland productivity. Our third goal, was to compare abundance-impact curves among the mentioned measures of pine abundance and among different measures of impact: total grassland productivity, palatable productivity and sheep stocking rate (the number of sheep that the grassland can sustainably support). Pine canopy cover, closely followed by basal area, was the measure of abundance that best explained the impact on grassland productivity, but the shape of abundance impact curves differed between measures of abundance. While increases in pine density and basal area always reduced grassland productivity, pine canopy cover below 30% slightly increased grassland productivity and higher values caused an exponential decline. This increase in grassland productivity with low levels of pine canopy cover could be explained by the amelioration of stressful abiotic conditions for grassland species. Different measures of impact, namely total productivity, palatable productivity and sheep stocking rate, drew very similar results. Our abundance-impact curves are key to guide the management of invasive pines because a proper assessment of how many invasive individuals (per surface unit) are unacceptable, according to environmental or economic impact thresholds, is fundamental to define when to start management actions.

Abundance of invasive alien species of teklan (Ageratina riparia (Regel) R. M. King & H. Rob.: Asteraceae) on floor vegetation in “Eka Karya” Botanical Garden, Bali

Ageratina riparia is an invasive alien species that get a particular attention in “Eka Karya” Bali Botanical Garden. This study aims to determine the abundance of invasive alien species A. riparia on forest floor vegetation in “Eka Karya” Bali Botanical Garden, and the factors that influence its abundance. Ageratina riparia is an invasive herb that can disrupt the balance of the ecosystem. The advantages of this plant in reproducing and adapting to the environment, make this plant very easy to grow and develop in a habitat. The purposive sampling method was used with the plot that placed systematically. The research area divided into five research stations with 10 plots (2 x 2 m) for each station. Vegetation data were analyzed to determine the density, relative density, frequency, relative frequency, and important value index (INP), then completed with Shannon-Weiner diversity index (H'), dominancy index (C), evenness index (E) and visualization abundance of species A. riparia of with Non-metric Multi Dimensional Scaling (NMDS). Environmental data is calculated analyses in Detrended Correspondence Analysis (DCA). The results showed that A. riparia at station 1 (Kawasan Kepala Burung) had an INP of 62.50%, station 2 (Taman Usada) with an INP of 52.40%, station 3 (Taman Cyathea) with an INP of 89.09%, station 4 (middle open area) with an INP of 110.25%, and the highest is at station 5 (Taman Upacara Panca Yadnya) with an INP value of 118.92%. The presence of A. riparia can be influenced by all environmental factors measured such as air humidity, soil moisture, soil pH, air temperature and soil temperature, altitude, land slope, and light intensity.

Effects of slashing on native and invasive species, and community structure of a remnant natural grassland of South Australia

AbstractQuestionsWe investigated the feasibility of slashing as a management tool to reduce the abundance of the exotic invasive species Avena barbata and favour native species and diversity in remnants of semi‐arid native grasslands. We asked how slashing affects: (1) the seed production and seed bank of A. barbata, (2) the mortality of perennial native tussock grasses, and (3) plant community composition.LocationNear Burra, Mid North region of South Australia.MethodsWe established two parallel experiments in an invaded grassland: one in a stand dominated by exotic and invasive species (“poor” condition), and the other in a less‐degraded stand with an abundance of native perennial grasses (“good” condition). The experiments had a randomized block design (six blocks) with three treatments each: no slashing, slashing once a year or slashing every other year, applied over 3 years. We assessed the effects of the treatments on the number of seeds per m2 and soil seed bank of A. barbata, number of death native tussock grasses, and floristic composition and diversity.ResultsSlashing reduced seed production and the soil seed bank of A. barbata in both stands. Slashing increased the mortality of native grasses in the stand in good condition, and slightly changed floristic composition only in the stand in poor condition. Here, slashing decreased the abundance of the invasive species A. barbata and Bromus rigens but favoured other exotic species. No changes in species richness or diversity were detected.ConclusionsThe slight response of the plant community to slashing suggests that these grasslands are resistant to changes in management. However, the reduction in seed production and soil seed bank of A. barbata suggest that longer term application of slashing could reduce its abundance and allow native species to recruit. The mortality of native tussocks can, however, negate the benefit of reducing abundance of invasive species.

Does fire and herbicide benefit cattle production in invaded grassland landscapes?

Invasive species management is promoted as a general practice to maintain rangeland biodiversity and mitigate livestock performance losses (e.g., weight gain) stemming from invasive-species effects (e.g., competitive exclusion of palatable forages). It is hypothesized that altering fire-timing (e.g., moving from early to late-growing season burning) or integrating herbicide application into fire management regimes may lead to more successful reduction of certain invasive species without negatively affecting livestock weight gains. However, large-scale, replicated experimental evidence linking invasive species abundance or management practices to cattle weight gain is mostly lacking across grasslands. We manipulated eight large (333 – 766 ha) pastures managed with fire and grazing (i.e., pyric herbivory) to test how growing (i.e., August-September) and dormant (i.e., March-April) season fires, herbicide application, or invasive species abundance (namely Lespedeza cuneata) affected yearling stocker cattle weight gain – i.e., per head weight gain – from 2018 to 2020. We found that yearling stocker cattle gained significantly less weight in pastures burned during the growing season, and herbicide application did not increase weight gains overall. Moreover, we did not find a significant relationship between L. cuneata abundance and per head yearling stocker cattle weight gain. Our results add to a growing line of evidence that invasive species management does not always benefit livestock producers. The hypothesized negative relationship between invasive species abundance and cattle weight gain may be minimal (or neutral) across large grassland landscapes, particularly those managed with pyric herbivory. To date, pyric herbivory is the only management regime known to simultaneously promote biodiversity, and restrict some invasive plant species like L. cuneata.

Code and data from Boyer et al. "Landscape transformation and variation in invasive species abundance drive change in primary production of aquatic vegetation in the Sacramento–San Joaquin Delta"

Code and data from Boyer et al. "Landscape transformation and variation in invasive species abundance drive change in primary production of aquatic vegetation in the Sacramento–San Joaquin Delta"