Alien plants as mediators of ecosystem services and disservices in urban systems: a global review

Urban areas have unique assemblages of species which are governed by novel ecological processes. People living in these environments have specific needs and demands in terms of ecosystem services (ES). Urban ecosystems are transformed in many ways by human activities and their floras comprise a high proportion of alien plant species, many of which were intentionally introduced to provide, augment or restore ES. Urban environments also have novel disturbance regimes and provide colonization sites for the establishment, dispersal and proliferation of alien plant species; such conditions often generate biological invasions which may cause marked changes to ES. We review the roles that alien plants play in providing urban ES and ecosystem disservices (EDS) globally. We identify the main ES and EDS associated with alien plants, and highlight the key species involved. A literature search revealed 335 papers, representing studies in 58 cities or urban areas in 27 countries. These studies recorded 337 alien plant species, contributing to 39 different ES and 27 EDS–310 species were recorded as contributing to ES and 53 species to EDS. A small number of alien plant taxa were frequently recorded as providing multiple ES in many urban ecosystems; the 10 most recorded species accounted for 21% of the ES recorded. Some of these species also result in significant EDS; three species accounted for 30% of the EDS recorded. Cultural services (notably aesthetics) are the most reported ES provided by alien plants in urban areas of developed countries, while provisioning services (notably food production) are most reported in developing countries. The most commonly studied EDS provided by alien plants is the impact on human health (notably allergic reactions). Eighty percent of studies on alien plants and ES and EDS have been done in developed countries. To elucidate the full range of effects of alien plants, more work is needed in developing countries. Urban planners and managers need to be mindful of both the positive and negative impacts of alien plant species to maximise the provision of ES.     

The relative impacts of native and introduced predatory fish on a temporary wetland tadpole assemblage

Understanding the relative impacts of predators on prey may improve the ability to predict the effects of predator composition changes on prey assemblages. We experimentally examined the relative impact of native and introduced predatory fish on a temporary wetland amphibian assemblage to determine whether these predators exert distinct (unique or non-substitutable) or equivalent (similar) impacts on prey. Predatory fish included the eastern mosquitofish (Gambusia holbrooki), golden topminnow (Fundulus chrysotus), flagfish ( Jordanella floridae), and the introduced walking catfish ( Clarias batrachus). The tadpole assemblage included four common species known to co-occur in temporary wetlands in south-central Florida, USA: the oak toad (Bufo quercicus), pinewoods treefrog (Hyla femoralis), squirrel treefrog (Hyla squirella), and eastern narrowmouth toad (Gastrophryne carolinensis). Tadpoles were exposed to different predators in wading pools under conditions similar to those found in surrounding temporary wetlands (particularly in terms of substrate type, the degree of habitat complexity, and temperature). Native predators were similar with respect to predation rate and prey selectivity, suggesting similar energy requirements and foraging behavior. Conversely, native fish predators, especially G. holbrooki, were distinct from the introduced C. batrachus. In contrast to expectations, C. batrachus were less voracious predators than native fish, particularly G. holbrooki. Moreover, survival of G. carolinensis and H. femoralis were higher in the presence of C. batrachus than G. holbrooki. We suggest that C. batrachus was a less efficient predator than native fish because the foraging behavior of this species resulted in low predator-prey encounter rates, and thus predation rate. In combination with a related field study, our results suggest that native predatory fish play a stronger role than C. batrachus in influencing the spatial distribution and abundance of temporary wetland amphibians in the landscape.     

Exotic vertebrate and invertebrate herbivores differ in their impacts on native and exotic plants: a meta-analysis

Herbivores modify various ecological processes including interactions between native and exotic plants that may affect invasion success by the exotic plants. It is unknown whether different types of exotic herbivores have similar effects on native and exotic plants. Using two distinct data sets, we ran meta-analyses to compare exotic vertebrate and invertebrate herbivore preferences for, and effects on performance and population sizes of native and exotic plants. We found that exotic vertebrate herbivores have positive effects on exotic plant performance and population sizes, and no significant effects on native plants. Exotic invertebrates have significant negative effects on performance and population sizes of both exotic and native plants. Vertebrates prefer to feed on native plants relative to exotic plants, while invertebrates prefer the exotic plants to native plants. Thus the exotic vertebrate herbivores may aid invasiveness of exotic plants, in accordance with the invasional meltdown hypothesis, while exotic invertebrate herbivores probably have no net effect on invasion process of the exotic plants. Invertebrate herbivore preferences for exotic plants support the biotic resistance hypothesis, as the native plants probably resist the invertebrate herbivory. We also tested an evolutionary logic that posits that herbivores with similar evolutionary history as plants will affect the plants less negatively than plants with which they have not co-evolved. Our results indicate that there is no consistent pattern in effects of exotic vertebrate and invertebrate herbivores on exotic plants with or without which they have co-evolved.     

Modelling the impacts of two exotic invasive species on a native butterfly: top-down vs. bottom-up effects

1. Exotic invasive species can influence population dynamics of native species through top-down or bottom-up forces. The present study examined separate and interactive effects of multiple exotic species invasions on the native mustard white butterfly, Pieris napi oleracea Harris (Lepidoptera: Pieridae), using a stochastic simulation model. 2. P. n. oleracea populations in North America have decreased regionally since the 1860s. Competition with an exotic congener (P. rapae L.), loss of native host plants and parasitism by the introduced broconid wasp (Cotesia glomerata L.), have been suggested to be independently responsible for its decline. The present study examined these hypotheses, as well as an alternative, invasion by an exotic crucifer, garlic mustard (Alliaria petiolata[Bieb.] Cavara & Grande). 3. A stochastic simulation model of P. n. oleracea population dynamics revealed that decreasing the number of host plants available for oviposition and larval development (i.e. habitat loss), sharply reduced the probability of populations persistence and decreased population size for those that persisted. 4. Simulated invasion by garlic mustard also substantially decreased both probability of persistence (= 0 at approximately 50% cover) and mean population size. Persistence probability never reached zero under any C. glomerata scenarios, even when larval mortality in the second generation due to parasitism was 100%. The impact of garlic mustard was intensified by the addition of C. glomerata parasitism. 5. Results suggest that bottom-up forces, loss of host plants through forest understorey loss and/or garlic mustard invasion are the most important forces driving P. n. oleracea population decline. Parasitism by C. glomerata may interact to reduce P. n. oleracea populations more rapidly, but appears insufficient alone to cause local extinction.     

Responses of native and invasive wetland plants to hydroperiod and water depth

Monotypic stands of reed canary grass, Phalaris arundinacea, replace native wetland vegetation where stormwater runoff alters hydrologic conditions, nutrient inflows, and sedimentation rates. We asked if different hydrologic conditions could explain the dominance of Phalaris and/or loss of the native grass, Spartina pectinata, and we compared the growth of each species alone and together under four hydroperiods (varying inundation frequency and duration) each at two water depths (surface saturation and flooding to 15 cm). When grown alone, aboveground biomass was similar for the two species, but Phalaris produced twice the stem length of Spartina via its low tissue density. Per unit biomass, Phalaris distributed its leaves over a larger canopy volume. Flooding reduced belowground biomass and increased total shoot length and shoot:root biomass of each species. Phalaris produced the most biomass, shoots, and total shoot length when wetter and drier conditions alternated weekly, while Spartina grew best with prolonged (4-week) inundation. When grown with Spartina, Phalaris changed its morphology by increasing its total shoot length:biomass ratio by 50%. However, ratios of Spartina:Phalaris aboveground biomass, shoot number, and total shoot length in two-species pots were not significantly affected by water depth or hydroperiod. We conclude that two plant attributes facilitate Phalaris' dominance of wetlands: its high ratio of total shoot length:biomass and its adaptable morphology (characterized herein as increased total shoot length:biomass when grown with Spartina).     

Interacting impacts of invasive plants and invasive toads on native lizards

The ecological impacts of an invasive species may be reduced by prior invasions if selective pressures imposed by earlier events preadapt the native biota to deal with the newer arrival. In northwestern Australia, invasion of the cane toad (Rhinella marina) kills many native predators if they ingest the highly toxic toads. Remarkably, the toads' defensive toxins (bufadienolides) are chemically similar to those of another invasive species: an ornamental plant from Madagascar, Bryophyllum spp. (Crassulaceae, mother-of-millions). Omnivorous lizards (bluetongue skinks, Tiliqua scincoides) are imperiled by the invasion of toads in northwestern Australia, but conspecifics from other areas of the continent (those where exotic plants were introduced and including areas where toads have yet to invade) are less affected because they exhibit higher physiological tolerance of toad toxins (and also of plant toxins). The willingness of captive bluetongues to consume both toads and these plants and the high correlation in the lizards' sensitivity to toad toxins versus plant toxins suggest that exotic plants may have imposed strong selection on the lizards' physiological tolerance of bufadienolides. As a result, populations of lizards from areas previously exposed to these alien plants may be preadapted to deal with the toxins of the more recent anuran invader.     

Fish vs. Aliens: predatory fish regulate populations of Limnoperna fortunei mitigating impacts on native macroinvertebrate communities

Hydrobiologia - Limnoperna fortunei, an invasive mussel altering the structure of benthic communities, is preyed upon by several fish species in South America. To investigate the impact of...     

Proximate biochemical composition and caloric content calculated from elemental CHN analysis: a stoichiometric concept

Summary Carbohydrate, lipid, and protein compositions are stoichiometrically related to organic CHN (carbon, hydrogen, nitrogen) contents. Elemental CHN analyses of total biomass and ash, therefore, provide a basis for the calculation of proximate biochemical composition and bomb caloric value. The classical nitrogen to protein conversion factor (6.25) should be replaced by 5.8±0.13. A linear relation exists between the mass fraction of non-protein carbon and the carbohydrate and lipid content. Residual water in dry organic matter can be estimated with the additional information derived from hydrogen measurements.The stoichiometric CHN method and direct biochemical analysis agreed within 10% of ash-free dry biomass (for muscle, liver and fat tissue of silver carp; gut contents composed of detritus and algae; commercial fish food). The detrital material, however, had to be corrected for non-protein nitrogen.A linear relationship between bomb caloric value and organic carbon fractions was derived on the basis of thermodynamic and stoichiometric principles, in agreement with experimental data published for bacteria, algae, protozoa and invertebrates. The highly automatic stoichiometric CHN method for the separation of nutrient contents in biomass extends existing ecophysiological concepts for the construction of balanced carbon and nitrogen, as well as biochemical and energy budgets.Offprint requests to: Institut für Zoologie, Abt. Zoophysiologie, Universität Innsbruck, Peter-Mayr-Str. 1A, A-6020 Innsbruck, Austria     

Feral pigs in a temperate rainforest ecosystem: disturbance and ecological impacts

Feral pigs (Sus scrofa) are a widespread invasive species, and cause biotic disturbance. This study evaluated the impacts associated with ground disturbance by feral pigs in the North Island of New Zealand. Exclosure cages were erected over feral pig-disturbed ground and visually undisturbed ground (the latter as controls). Buried resin bags and litter bags were located in these plots to examine differences in soil nutrients and decomposition rates and seedling/sapling recruitment (abundance, species composition and richness) was monitored over 21 months. No difference was found in the litter decomposition between the disturbed and visually undisturbed plots. Significantly more nitrate (NO₃-N/NO₂-N) was found in the disturbed exclosures. Seedling density was not significantly affected by feral pig disturbance. However, seedling/sapling species richness was lower in disturbed areas. Species composition changes occurred at disturbed sites with species increasing and decreasing in density after feral pig disturbance. However, no pattern was observed between species that were negatively affected by feral pig disturbance. This study shows that feral pig disturbance affects vegetation through direct removal, but also indirectly through increased nitrate, potentially leading to seedling and sapling species composition changes. Feral pigs are known to return to previously disturbed areas to re-disturb. These areas may remain in a re-disturbed state if not protected, and through continued disturbance and increased nitrate, ecosystem changes may occur, especially in characteristically nutrient poor environments.     

边缘效应及其对森林生态系统影响的研究进展

边缘效应是生态学和生物保护的重要概念之一,它在研究生态系统尺度和景观生态系统尺度的能量流和物质流等生态过程中具有重要作用.本文对边缘效应的内涵、特征、定量评价(包括定量分析基础、强度、影响区、模型等)、应用研究等方面进行阐述,分析了边缘效应研究中存在的不足,总结了边缘效应对森林生态系统的影响及其研究方向,以期为森林经营、保护区管理等生产实践提供借鉴.     

Correction to: Fish vs. Aliens: predatory fish regulate populations of Limnoperna fortunei mitigating impacts on native macroinvertebrate communities

Hydrobiologia - A correction to this paper has been published: https://doi.org/10.1007/s10750-021-04580-3     

Alien and native birds in South Africa: patterns, processes and conservation

The spatial distribution of alien species richness often correlates positively with native species richness, and reflects the role of human density and activity, and primary productivity and habitat heterogeneity, in facilitating the establishment and spread of alien species. Here, we investigate the relationship between the spatial distribution of alien bird species, human density, and anthropogenic and natural environmental conditions. Next, we examined the relationship between the spatial distribution of alien bird species and native bird species richness. We examined alien species richness as a response variable, using correlative analyses that take spatial autocorrelation into account. Further, each alien bird species was examined as a response variable, using logistic regression procedures based on binary presence–absence data. A combination of human density and natural habitat heterogeneity best explained the spatial distribution of alien species richness. This contrasts with the results for individual alien species and with previous studies on other non-native taxa showing the importance of primary productivity and anthropogenic habitat modification as explanatory variables. In general, native species richness is an important correlate of the spatial distribution of alien species richness and individual alien species, with alien species being more similar to common species than to rare species.     

Marine plants in a coral reef ecosystem

Based on a review of the literature and our own data, marine plants are shown to play an important role in the formation and sustaining of coral reefs, which are one of coastal tropical ecosystems of the World Ocean. The important ecosystem roles of marine plants include primary production and recycling of organic matter, the construction of the hard base of a coral reef, the fixation of dissolved molecular nitrogen in sea-water, the formation of an initial link in the food chain, the provision of a habitat for marine animals, and the protection of the reef against destructive wave action.     

Effects of hydromorphological impacts on river ecosystem functioning: a review and suggestions for assessing ecological impacts

Because of the serious effects of pollution on water supply much closer attention has been paid to water quality than to other aspects of river integrity. However, channel form and water flow are relevant components of river health, and recent evidences show that their impairment threatens the services derived from them. In this article, we review the literature on the effects of common hydromorphological impacts (channel modification and flow modification) on the functioning of river ecosystems. There are evidences that even light hydromorphological impacts can have deep effects on ecosystem functioning, and that different functional variables differ in their responses. Three criteria (relevance, scale and sensitivity) in the selection of functional variables are suggested as a guide for the river scientists and managers to assess the ecological impacts of hydromorphological modifications.     

Landscape transformation after irrigation development in and around a semi-arid wetland ecosystem

The objectives of this study are to determine the spatial and temporal land use/cover changes in a semi-arid agricultural basin (Develi Basin) after the implementation of an irrigation project and to understand how these changes affected the wetlands (Sultan Marshes) located in the basin. The changes were determined using multitemporal Landsat Thematic Mapper and Landsat 8 Operational Land Imager imagery taken in 1987, 1998, 2007, and 2013. The images were classified into six information classes (grasslands/shrublands, croplands, permanent wetlands, water bodies, barren, and urban/built-up) using a hybrid classification method. Post-classification change detection was applied to determine the changes between different years. Overall, the accuracy of the classified images ranged from 85 to 94%. Grasslands/shrublands covered the largest area in the basin (63% in 2013), followed by croplands (32% in 2013). The area covered by water bodies, permanent wetlands, barren, and urban/built-up was 5% (in 2013). From 1987 to 2013, croplands expanded by 56%, while grasslands/shrublands declined by 15%. The areas occupied by water bodies decreased by 88% and permanent wetlands decreased by 4%. Urban/built-up areas expanded by 140%. The hydrologic regime of the Sultan Marshes wetland changed, which resulted in declines in water volumes by 85% and in water inflows by 55% from 2000 to 2015. Climatic variations during the 1987–2013 period were low and there was no apparent trend in precipitation and air temperature, which ruled out climatic conditions as one of the drivers of wetland changes. Economic and institutional factors supported the expansion of irrigated agriculture and animal husbandry in the basin and accelerated the expansion of croplands and conversion to industrial and fodder crops and orchards from traditional non-irrigated crops. Expansion of croplands and irrigated agriculture were the major drivers of the changes in the Sultan Marshes.

     

Phosphorus cycling and partitioning in an oligotrophic Everglades wetland ecosystem: a radioisotope tracing study

1. Our goal was to quantify short‐term phosphorus (P) partitioning and identify the ecosystem components important to P cycling in wetland ecosystems. To do this, we added P radiotracer to oligotrophic, P‐limited Everglades marshes. ³²PO₄ was added to the water column in six 1‐m² enclosed mesocosms located in long‐hydroperiod marshes of Shark River Slough, Everglades National Park. Ecosystem components were then repeatedly sampled over 18 days. 2. Water column particulates (>0.45 μm) incorporated radiotracer within the first minute after dosing and stored 95–99% of total water column ³²P activity throughout the study. Soluble (<0.45 μm) ³²P in the water column, in contrast, was always <5% of the ³²P in surface water. Periphyton, both floating and attached to emergent macrophytes, had the highest specific activity of ³²P (Bq g^?131P) among the different ecosystem components. Fish and aquatic macroinvertebrates also had high affinity for P, whereas emergent macrophytes, soil and flocculent detrital organic matter (floc) had the lowest specific activities of radiotracer. 3. Within the calcareous, floating periphyton mats, 81% of the initial ³²P uptake was associated with Ca, but most of this ³²P entered and remained within the organic pool (Ca‐associated = 14% of total) after 1 day. In the floc layer, ³²P rapidly entered the microbial pool and the labile fraction was negligible for most of the study. 4. Budgeting of the radiotracer indicated that ³²P moved from particulates in the water column to periphyton and floc and then to the floc and soil over the course of the 18 day incubations. Floc (35% of total) and soil (27%) dominated ³²P storage after 18 days, with floating periphyton (12%) and surface water (10%) holding smaller proportions of total ecosystem ³²P. 5. To summarise, oligotrophic Everglades marshes exhibited rapid uptake and retention of labile ³²P. Components dominated by microbes appear to control short‐term P cycling in this oligotrophic ecosystem.     

Reciprocal trophic niche shifts in native and invasive fish: salmonids and galaxiids in Patagonian lakes

1. Rainbow (Oncorhynchus mykiss) and brown trout (Salmo trutta) are widespread and invasive salmonids with important lethal effects as predators, although indirect effects are also possible. We used stable isotope analyses (δ¹⁵N, δ¹³C) to explore how the density of invasive trout in 25 Patagonian lakes alters the trophic niche (TN) of a widespread native fish, Galaxias platei (Galaxiidae). We also explored how the density of the galaxiid influences the TN of invasive trout. 2. We quantified two aspects of the TN: (i) the proportion of littoral carbon (PL) and (ii) trophic height (TH) (i.e. the ‘height’ at which the fish feeds in the food web). We related these measures of TN in a given species to the density of other species (as estimated by catch‐per‐unit‐effort). 3. As G. platei body size increased, their PL increased (increasing littoral feeding) in several lakes. However, none of the fish species investigated showed changes in PL with increasing density of the other fish species. TH increased with body size in all three species. In addition, the TH of large G. platei declined with increasing trout density and, reciprocally, the TH of large S. trutta decreased with decreasing G. platei density. 4. The reciprocal effects of native and the invasive fish on TH were as large as a shift of one trophic level. This pattern is consistent with an exhaustion of galaxiid prey for both piscivorous G. platei and S. trutta in lakes with high trout density. 5. These finding support the suggested management strategy of culling trout from overpopulated lakes, which should simultaneously protect native fish and enhance a lucrative sport fishery for large trout.     

Potential impacts of petroleum exploration and exploitation on biodiversity in a Patagonian Nature Reserve, Argentina

Petroleum exploration and extraction are common on the Patagonian steppe, but their impacts on the native biodiversity have not been properly evaluated. We describe both activities in a Patagonian nature reserve and consider their potential impacts on biodiversity. More than 2025 km of seismic lines inside the reserve resulted in 87.21 m²/ha (0.9%) of directly affected land, and 793 fragments of native habitats were defined with a mean area of 1.26 ± 0.74 km². Vegetation recovery on seismic lines is extremely poor. We discuss the role of seismic lines as barriers to native species, and their significance in encouraging poaching and the expansion of exotic invasive plants. There is a high degree of overlap between current petroleum activities and areas of special conservation concern (high erosion risk, vegetation diversity, abundance of endemic plant species, and habitat quality for native vertebrates). All these have a significant impact on the efficiency of the conservation area and highlight the urgent need to implement appropriate mitigating actions.     

Metal accumulation and tolerance in wetland plants

This paper briefly reviews the progress in studies of wetland plants in terms of heavy metal pollution. The current research mainly includes the following areas: (1) metal uptake, translocation, and distributions in wetland plants and toxicological effects on wetland plants, (2) radial oxygen loss (ROL) of wetland plants and its effects on metal mobility in rhizosphere soils, (3) constitutional metal tolerance in wetland plants, and (4) mechanisms of metal tolerance by wetland plants. Although a number of accomplishments have been achieved, many issues still remain unanswered. The future research effort is likely to focus on the ROL of wetland plants affecting metal speciation and bioavailability in rhizosphere soils, and the development of rhizosphere management technologies to facilitate and improve practical applications of phytoremediation of metalpolluted soils.     

Metal accumulation and tolerance in wetland plants

This paper briefly reviews the progress in studies of wetland plants in terms of heavy metal pollution. The current research mainly includes the following areas: (1) metal uptake, translocation, and distributions in wetland plants and toxicological effects on wetland plants, (2) radial oxygen loss (ROL) of wetland plants and its effects on metal mobility in rhizosphere soils, (3) constitutional metal tolerance in wetland plants, and (4) mechanisms of metal tolerance by wetland plants. Although a number of accomplishments have been achieved, many issues still remain unanswered. The future research effort is likely to focus on the ROL of wetland plants affecting metal speciation and bioavailability in rhizosphere soils, and the development of rhizosphere management technologies to facilitate and improve practical applications of phytoremediation of metal-polluted soils.