Spread Of Invasive Plant Species Research Articles

Can allelopathic potentialities of Mediterranean plant species reduce the spread of invasive plant species, Acacia dealbata and Ailanthus altissima?

Beyond ecological and health impacts, invasive alien plant species can generate indirect and direct costs, notably through reduced agricultural yields, restoration, and management of the invaded environment. Acacia dealbata and Ailanthus altissima are invasive plant species that cause particularly significant damage to the railway network in the Mediterranean area. The allelopathic properties of Mediterranean plant species could be used as nature-based solutions to slow down the spread of such invasive plant species along railway borders. In this context, a mesocosm experiment was set-up: (i) to test the potential allelopathic effects of Cistus ladanifer, Cistus albidus, and Cotinus coggygria leaf aqueous extracts on seed germination and seedling growth of A. dealbata and A. altissima; (ii) to evaluate whether these effects depend on the extract dose; and finally, (iii) to estimate whether these effects are modified by soil amendment. Leaf aqueous extracts of the three native plant species showed negative effects on both seed germination and seedling growth of the two invasive species. Our results show that the presence of allelochemicals induces a delay in seed germination (e.g., A. dealbata germination lasted up to 269% longer in the presence of high-dose leaf aqueous extracts of C. coggygria), which can lead to a decrease in individual recruitment. They also highlight a decrease in seedling growth (e.g., high-dose C. coggygria leaf aqueous extracts induced a 26% decrease in A. dealbata radicle growth), which can alter the competitiveness of invasive species for resource access. Our results also highlight that compost addition limits the inhibitory effect of native Mediterranean plants on the germination of invasive alien plants, suggesting that soil organic matter content can counteract allelopathic effects on invasive alien plants. Thus, our findings revealed that the allelopathic potential of certain Mediterranean plant species could be a useful tool to manage invasive plant species.

Predicting the Potential Risk Area of the Invasive Plant Galinsoga parviflora in Tibet Using the MaxEnt Model

The Tibetan plateau, with complex and diverse ecosystems, is an important ecological security barrier to China. However, climate change and the spread of invasive plant species have imperiled the once pristine and diverse ecosystem of the region. To prevent the further spread and control of invasive plants, it is important to delineate the potential distribution patterns of alien invasive plants at the regional scale across Tibet and understand their responses to climate change. Galinsoga parviflora Cav., a member of the family Asteraceae, is an annual herbaceous plant distributed globally as an invasive weed and possesses characteristics that make it highly invasive, such as a strong ability to proliferate and disperse. The species is also known to have an allelopathic effect. There has been no report on the spatial distribution of G. parviflora in Tibet. Using field survey data, we investigated the risk of G. parviflora invasion and its impacts on the ecological safety of Tibet. We employed the MaxEnt model using the R language and SPSS software to optimize and select model parameters and data. We acquired various environmental variables along with current and future climate change scenarios (two carbon emission scenarios, SSP126 and SSP585, for the years 2050 and 2090) to predict the geographic distribution and potential risk areas in Tibet that G. parviflora can invade. The MaxEnt model accurately predicted the distribution of G. parviflora in Tibet with an average AUC of 0.985. The most suitable environmental conditions in which G. parviflora performed the best in Tibet included a mean annual temperature of 6.2–10.0 °C and an elevation range of 2672–3744 m above sea level. Our results indicate that low precipitation during the coldest quarter of the year (mean temperature −2–3 °C) was the most important variable predicting G. parviflora distribution. The results also showed that the species was hardly found when precipitation in the coldest quarter exceeded 155 mm. The current potential invasion risk areas for G. parviflora included the river valleys of central, southeastern, and eastern Tibet. With future climate change scenarios (i.e., SSP126, SSP585), the suitable habitats for G. parviflora distribution will likely shift to northwest regions from the southeast. Particularly under the highest carbon emission scenario (i.e., SSP585), the potential risk area expands more rapidly, and the center of distribution shifts to northwest regions. These findings provide useful information about the current and future changes in G. parviflora distribution in Tibet, which is crucial for the comprehensive and proactive management and control of G. parviflora under future climate change.

Some features of morphology of the invasive species Conyza canadensis in the Republic of Abkhazia

The spread of invasive plant species, such as Conyza сanadensis - one of the main environmental threats, as these species become massive weeds of agricultural lands and settlements. The aim of the work was to study the biological characteristics of C. сanadensis in the conditions of the coastal lowland zone of the Republic of Abkhazia. The morphological parameters of the invasive species and their variability were studied. Anthropogenic load influences the morphological parameters of plants - in the western regions of Abkhazia, which are more disturbed by humans, the parameters of plants are lower than in the less disturbed eastern ones. The maximum values of most features were noted in the Gal region, where the ecotopes are undisturbed and close to optimal. All signs have a normal degree of variation (7.0-30.9 %). Further monitoring of the species is required.

The allelochemical potential of an invasive ornamental plant, the Indian blanket flower (Gaillardia pulchella Foug.)

AbstractGlobal spread of invasive plant species threatens biodiversity significantly, with a particularly high presence of invasives in the Asteraceae family. This is partly due to their wide use as ornamental plants and their rapid reproduction and allelopathy. The Indian blanket flower (Gaillardia pulchella) is a native North American species widely used as an ornamental plant and has become invasive in other countries. Although it contains bioactive compounds, its allelopathic impact on other plants has been largely unexplored. We conducted in vitro tests on oilseed rape (Brassica napus) germination and early growth to assess blanket flower's allelopathy. Seeds were exposed to aqueous extracts at three different concentrations (10%, 20%, and 40%). The 40% extract significantly inhibited germination during the treatment. All three concentrations inhibited root growth, with the 40% treatment showing this effect from the second day. In contrast, the extracts promoted significantly shoot elongation. Fresh weight of seedlings was not affected by the extract, but the 10% treatment resulted in higher mass. These findings provide evidence of blanket flower's allelopathic effects, shedding light on its invasive potential.

The Natural Consequences of Land Use Change on Transformation and Vegetation Development in the Upper Odra Floodplain

River channels are regulated in various ways and the fertile soils of valleys are occupied for agricultural purposes, accompanied by human settlements. In many places on the floodplains, gravel or sand is mined and former pits fill with water. The consequences are changes in water relations, changes in land use and land cover. Natural riparian ecosystems gradually disappear. In addition, river valleys are susceptible places for the spread of invasive plant species. In the section of the Upper Odra Valley discussed in this article, all of the aforementioned factors have played roles in shaping modern habitats. The present study shows the impact of human-induced changes on the transformation of the plant cover of the Upper Odra Floodplain. In designated transects, we studied land use changes from 1910 to the present day and examined plant species diversity. The results show that the more heavily transformed floodplain adjacent to the channelized channel has a higher level of species diversity than agricultural areas located along a section of the river with a natural channel course. Most of the river valleys are colonized by geographically invasive alien species, such as Reynoutria japonica, Reynoutria sachalenesis and Impatiens glandulifera, which have contributed to the fact that all of the species typical of the ash, poplar and willow riparian forests characteristic of this habitat type have retreated, which is the main reason for the very low biodiversity.

Intraspecific variations of adaptive strategies of native and invasive plant species along an elevational gradient

The dispersal of invasive alien plant species (IAPS) into mountains has posed great threats to local native plant species. It has been assumed that high intraspecific trait variability contributes to the spread of invasive plant species, even along mountains. Although intraspecific variability of single trait was more often investigated, Grime's competitor, stress-tolerator, and ruderal (CSR) plant strategies, representing trade-offs among multiple functional characters, provides both theoretical and methodological frameworks to inspect plant species’ adaptation to environments. Thus, considering Grime's CSR plant strategies with its intraspecific variation could improve the understanding of mechanisms of successful invasion by alien plant species. We estimated intraspecific variation of CSR plant strategies of five invasive and three native herb species and environmental characteristics (e.g., soil physiochemical variables) in their habitats along an elevational gradient ranging from 300 m to 1500 m a.s.l. We conducted linear mixed models to assess the variance explained by status (native vs. invasive), species identity and elevation, whereas linear regressions were used to link each of CSR scores of each species to elevation and environmental factors. The C- and R-score decreased, and the S-score increased along the elevational gradient, especially for invasive plant species. Species identity explained more proportion of the variation of CSR plant strategies. In addition, microhabitat variables like canopy cover and the ratio of soil ammonium nitrogen (NH4+-N) and nitrate nitrogen (NO3--N) concentrations (NH4/NO3) rather than elevation better explained the variation of CSR plant strategies of four out of the eight examined species. Our results showed that the species-specific and microhabitat-dependent factors determined the intraspecific variation of CSR plant strategies of the eight species along the elevational gradient. Furthermore, our study stresses the importance of microenvironment, particularly soil characteristics, in shaping intraspecific variation of plant species, which is essential for plant species to survive on large environmental gradient.

Invasive Plant Species in Ghana: Route of Spread, Socio-Economic and Environmental Impact

Globally, there has been a rapid increase in biodiversity loss, these losses have been attributed to habitat loss and invasive flora and fauna species. Extensive work has been done on the losses brought about by invasive fauna species, however, the impact of invasive flora species has less been explored in Ghana. This review focused on the various alien plant species found in Ghana and the factors that support their spread, establishment, and colonization. Findings indicate that the common invasive plants in Ghana are Chromolaema odorata, Calopogonium mucunoides, Cedrella ordorata, Leucaena leucocephala, Broussonetia papyrifera and Prosopis glasdulosa, Azardiracta indica, Echinochloa colona, and Leucaena leucocephala. The economic losses and environmental impact of these plant species were also reviewed. This review revealed that there is an urgent need to initiate interventions to control the rapid spread of invasive plant species, those measures should be cost-effective and eco-friendly.

Invasive plant species and their threat to biodiversity

The problem of the uncontrolled spread of alien plant species matured in the world in the second half of the 20th century, and in recent decades it has become the main threat to the biological diversity of various regions of the world. Prevention of biological Invasions is a new urgent task in the field of nature protection, which determines the relevance of the study. The purpose of the study is to determine and predict the distribution area of invasive plants, based on the use of the following methods: comparative morphological-ecological-geographical, route using determinants and atlases of plants of Ukraine, and the method of structural analysis. It is established that the characteristic features of invasive plant species are very high tolerance to habitat and climatic conditions, high rate of reproduction, simple and effective distribution by wind, water, animals, and rapid growth, which contributes to the displacement of slow-growing plants of other species and uncontrolled spread in the absence of natural enemies and restrictions. A particular danger to the biodiversity of Ukraine is the spread of invasive plant species: Sosnowsky’s Hogweed (Heracleum sosnowskyi), Canadian Goldenrod (Solidago canadensis L), American maple (Acer negundo L.), Red Oak (Quercus rubra), Common Ragweed (Ambrosia artemisiifolia L.), Common Milkweed (Asclepias syriaca L.), Silver Berry (Elaeagnus angustifolia), American pokeweed (Phytolacca Americana), Ecballium (Ecballium elaterium), Common Sandbur (Cenchrus pauciflorus Benth), Wall Barley (Hordeum murinum L.), Jerusalem Artichoke (Helianthus tuberosus), etc. The results of the study are an important scientific and practical basis for developing national and regional strategies for controlling invasive plant species

IMPROVEMENT OF REMOTE SENSING METHODS OF THE SPREAD OF INVASIVE PLANT SPECIES IN THE CONTEXT OF ASSESSING POTENTIAL DAMAGE TO THE ENVIRONMENT AND AGRICULTURE

Purpose. The aim of the article is to increase the efficiency of methods of spread of invasive plant species remote sensing to assess potential economic damage to the environment and agriculture through the use of intelligent surveillance systems. Methodology of research. The following methods were used in the study: monographic – for studying literature sources; machine learning method – for model training; three-way data split method for assessing model accuracy and statistical analysis for comparing recognition results; basic (traditional) methods for image enhancement; gradient image processing (Poisson mixing) – for image fusion. Findings. A model for improving the efficiency of methods for remote recognition of the spread of invasive plant species was developed and proposed. The performance of the proposed model was compared with the model based on traditional image augmentation methods. It was found that the CAIPIS method, which is the basis of the model, achieves significantly higher results in detecting invasive plant species, especially when the data set is limited. In addition, the method helps to increase the reliability and generalization of deep-learning models for detecting the spread of invasive plant species. The CAIPIS method provides means to create more diverse and realistic training samples, which helps to improve the generalization ability of the deep learning model in detecting invasive plants in aerial imagery of agricultural fields and ecosystems obtained using unmanned aerial vehicles. Originality. A new method for enhancing (augmenting) aerial images of crop fields is presented, which aims to improve the performance of invasive plant detection models by creating diverse and realistic training samples and increasing the variability of the training dataset to improve the performance of such models. Practical value. The application of the aerial images enhancement (augmentation) method will increase the effectiveness of controlling the spread of invasive pests in ecosystems. Key words: invasive species, phytoinvasion, augmentation, recognition, remote sensing.

COMPETITIVE ABILITY OF INVASIVE WEED SPECIES AND THEIR INFLUENCE ON PHYTOCENOSE BIODIVERSITY

The global threat from the spread of invasive plant species leads to an imbalance of plant living conditions in the agrocenosis and depletion / destruction of biodiversity. Ukrainian scientists are conducting a research on the impact of alien species of flora in the context of environmental threats to phytoinvasions. Invasive plants are especially dangerous both for the integrity of natural ecosystems and for various areas of economic activity. Invasive plant species cause significant damage to agriculture, forestry and water management, nature reserve areas.
 Less common invasive plant species create one of the biggest environmental problems in the world. This is a scientifically proven fact, which is legally reflected both in international conventions and in the legislation of individual countries.
 The foundation of an ecosystem is made by its flora. Therefore, invasive plant species are a blow to its foundation. If climatic conditions are suitable for invasive plants, they have a huge competitive advantage over native species, as they have no or limited natural enemies/consumers and diseases in the local ecosystem that could deter their spread. Therefore, they simply squeeze out local species from the territories, dooming them to extinction.
 The extinction of native plant species leads to extinction of native species of animals, fungi and many microorganisms that have built ties with the aboriginal flora for thousands or millions of years. They are directly dependent on it and are organically interconnected. That is why the invasion of an alien species does not increase the number and activity of local biodiversity, but, on the contrary, leads to the death of a significant number of species of flora and fauna dominated by only one or more species of invasive plants.
 In Ukraine, the impact of non-native plants on the environment is growing every year. In terms of Adventist flora, Ukraine ranks first among other flora in the world. The spontaneous fraction of adventive flora of Ukraine has 830 species of vascular plants (including 18 % – archeophytes and 82 % – kenophytes), which is about 14 % of the total flora of the country, which has more than 6,000 species of vascular plants (including all aboriginal and adventitious species), as well as the main cultivated and wild plants.

Bioethanol Production Potential and Other Biomass Energy Properties of Invasive Reynoutria, Solidago, and Spiraea Plants

Due to the threat posed by the spread of invasive plant species, there is an urgent need to develop effective methods of eradicating and managing their biomass. The aim of the study was to examine selected invasive plants in terms of their use for energy purposes and to find out whether they can be a raw material for the production of second-generation biofuels. First, their chemical compositions were determined. The higher heating value (HHV) and lower heating value (LHV) were also calculated. High values of the higher heating value, ranging from 18.490 MJ∙kg−1 to 19.900 MJ∙kg−1, indicate the possibility of using the biomass of invasive plants for energy purposes (combustion). All investigated invasive plant species were also subjected to the process of obtaining ethanol. This included an alkaline pretreatment with 1% sodium hydroxide, followed by a simultaneous saccharification and fermentation (SSF) process. The highest ethanol yield per ha of plants was obtained at 2.6 m3∙ha−1 for the Reynoutria × bohemica biomass. The remaining species showed an ethanol yield below 2 m3∙ha−1. The conducted research allows for the conclusion that the studied invasive plants can be a promising raw material for the production of bioethanol.

Propagation of invasive plant species in the presence of a road

Invasive plant species pose a significant threat to biodiversity and the economy, yet their management is often resource-intensive and expensive, and further research is required to make control measures more efficient. Evidence suggests that roads can have an important effect on the spread of invasive plant species, although little is known about the underlying mechanisms at play. We have developed a novel mathematical model to analyse the impact of roads on the propagation of invasive plants. The integro-difference equation model is formulated for stage-structured population and incorporates a road sub-domain in the spatial domain. The results of our study reveal, that, depending on the definition of the growth function in the model, there are three distinct types of behaviour in front of the road. Roads can act as barriers to invasion, lead to a formation of a beachhead in front of the road, or act as corridors allowing the invasive species to invade the domain in front of the road. Analytical and computational findings on how roads can impact the spread of invasive species show that a small change in conditions of the environment favouring the invasive species can change the case for the road, allowing the invasive species to invade the domain in front of the road where it previously could not spread.

Geographical distribution and spatio-temporal changes in the occurrence of invasive plant species in Slovak Republic

Biological systems are subject to a dramatic increase in invading species in the 21st century due to increasing globalization around the world. In the near future, these species will cause more extensive ecological as well as socio-economic damage. Biotic invasions will result not only in a reduction of the original biodiversity, but also total loss, particularly degradation of natural habitats – especially Natura 2000 habitats. This study aims to understand the processes of spread of invasive plant species, their way of life, adaptation to environmental changes and displacement of native species. Without the local level, it is not possible to understand these processes on the regional and continental dimensions and thus implement scientific facts and findings into the prediction of the development of global biosystems. The research was conducted during the vegetation period in the years 2017–2021 in the studied areas of non-forest and forest habitats in the central part of Slovakia. We recorded 242 localities in the area with the occurrence of invasive plant species in an area of 3.057 km2 out of the total mapped area of 169.024 km2. We recorded the highest number of localities and the most expansive distribution for the species Stenactis annua, Robinia pseudoacacia, Solidago canadensis, Impatiens glandulifera and Fallopia japonica.

Study of invasive plants in tropical dry deciduous forests – biological spectrum, phenology, and diversity

Abstract Morni Hills of Panchkula district, Haryana harbor floristically important tropical dry deciduous forests and are quite enriched with the phytodiversity of medicinally important plant species. But these forests are under huge pressure due to anthropogenic activities facilitating the establishment and spread of invasive plant species. So, the present study was conducted in the forests of Morni Hills to understand the ecology of invasive alien plant species growing there. During the study, the area was colonized by many invasive alien plant species, such as Ageratum conyzoides L., A. haustonianum Mill., Chromolaena odorata (L.) R.M. King & H. Rob., Lantana camara L., etc. In terms of longevity, the annual growth form dominated over the perennial. The family Asteraceae was dominant with 11 species, followed by Malvaceae and others. The biological spectrum showed that the dominant life form was therophytes followed by phanerophytes and others, indicating vegetation disturbance while during flowering phenology assessment, maximum plant species were found to be flowering throughout the year. Using the data of flowering (presence or absence), a hierarchical cluster analysis was carried out and a heatmap was prepared. The diversity of invasive plants was calculated along an altitudinal gradient and was found to be changing along with rising altitude in a hump-shaped pattern. The invasive alien plant species cause severe threats to the forest ecosystems. Hence, by policy planning and adopting appropriate management strategies in the forests of Morni Hills, the growth of invasive alien plant species should be controlled to retain the natural ecology of the area.

Potentials and Limitations of WorldView-3 Data for the Detection of Invasive Lupinus polyphyllus Lindl. in Semi-Natural Grasslands

Semi-natural grasslands contribute highly to biodiversity and other ecosystem services, but they are at risk by the spread of invasive plant species, which alter their habitat structure. Large area grassland monitoring can be a powerful tool to manage invaded ecosystems. Therefore, WorldView-3 multispectral sensor data was utilized to train multiple machine learning algorithms in an automatic machine learning workflow called ‘H2O AutoML’ to detect L. polyphyllus in a nature protection grassland ecosystem. Different degree of L. polyphyllus cover was collected on 3 × 3 m2 reference plots, and multispectral bands, indices, and texture features were used in a feature selection process to identify the most promising classification model and machine learning algorithm based on mean per class error, log loss, and AUC metrics. The best performance was achieved with a binary classification of lupin-free vs. fully invaded 3 × 3 m2 plot classification with a set of 7 features out of 763. The findings reveal that L. polyphyllus detection from WorldView-3 sensor data is limited to large dominant spots and not recommendable for lower plant coverage, especially single plant detection. Further research is needed to clarify if different phenological stages of L. polyphyllus as well as time series increase classification performance.

Long-term forest health implications of roadlessness

The 2001 Forest Service Roadless Rule prohibits roadbuilding in forests across an area equivalent to the combined states of New York and Maine (236 000 km2). There have been recent assertions that roads are needed to prevent fire and to keep forests healthy. Despite twenty years of ongoing forest health monitoring and the unique scope and ecological significance of this network of roadless areas, there has to date been no integrated assessment of the relationship between roads and forest health. Here, this question was addressed by synthesizing different sources of nationally consistent, longitudinal monitoring data. Agency management records show that a lack of roads has not stopped fire prevention measures; fuel management activities in roadless areas have actually been more numerous on a per-square kilometer basis than elsewhere in the National Forest System, although activities in areas with roads cover larger areas. Historical fire maps indicate that forests with and without roads have burned at similar rates since the Rule took effect. The apparent neutrality of roads with respect to fire occurrence may be due to higher rates of human caused ignition near roads offsetting advantages related to more agile positioning of fire-fighting assets. Beyond the fire dimension of forest health, analysis of over 15 000 inventory plots showed that while tree root disease is only weakly correlated with proximity to roads, roads are strongly associated with the spread of invasive plant species in national forests. Non-native plants are twice as common within 152 meters (500 feet) of a road as farther away. Speculation that eliminating road prohibitions would improve forest health is not supported by nearly twenty years of monitoring data.

Future distribution of invasive weed species across the major road network in the state of Montana, USA

Invasive plant species are a significant global problem, with the potential to alter structure and function of ecosystems and cause economic damage to managed landscapes. An effective course of action to reduce the spread of invasive plant species is to identify potential habitat incorporating changing climate scenarios. In this study, we used a suite of species distribution models (SDMs) to project habitat suitability of the eleven most abundant invasive weed species across road networks of Montana, USA, under current (2005) conditions and future (2040) projected climates. We found high agreement between different model predictions for most species. Among the environmental predictors, February minimum temperature, monthly precipitation, solar radiation, and December vapor pressure deficit accounted for the most variation in projecting habitat suitability for most of the invasive weed species. The model projected that habitat suitability along roadsides would expand for seven species ranging from + 5 to + 647% and decline for four species ranging from − 11 to − 88% under high representative concentration pathway (RCP 8.5) greenhouse gas (GHG) trajectory. When compared with current distribution, the ensemble model projected the highest expansion habitat suitability with six-fold increase for St. John’s Wort (Hypericum perforatum), whereas habitat suitability of leafy spurge (Euphorbia esula) was reduced by − 88%. Our study highlights the roadside areas that are currently most invaded by our eleven target species across 55 counties of Montana, and how this will change with climate. We conclude that the projected range shift of invasive weeds challenges the status quo, and requires greater investment in detection and monitoring to prevent expansion. Though our study focuses across road networks of a specific region, we expect our approach will be globally applicable as the predictions reflect fundamental ecological processes.

Trait differentiation between native and introduced populations of the invasive plant Sonchus oleraceus L. (Asteraceae)

There is growing evidence that rapid adaptation to novel environments drives successful establishment and spread of invasive plant species. However, the mechanisms driving trait adaptation, such as selection pressure from novel climate niche envelopes, remain poorly tested at global scales. In this study, we investigated differences in 20 traits (relating to growth, resource acquisition, reproduction, phenology and defence) amongst 14 populations of the herbaceous plant Sonchus oleraceus L. (Asteraceae) across its native (Europe and North Africa) and introduced (Australia and New Zealand) ranges. We compared traits amongst populations grown under standard glasshouse conditions. Introduced S. oleraceus plants seemed to outperform native plants, i.e. possessing higher leaf and stem dry matter content, greater number of leaves and were taller at first flowering stage. Although introduced plants produced fewer seeds, they had a higher germination rate than native plants. We found strong evidence for adaptation along temperature and precipitation gradients for several traits (e.g. shoot height, biomass, leaf and stem dry matter contents increased with minimum temperatures, while germination rate decreased with annual precipitations and temperatures), which suggests that similar selective forces shape populations in both the native and invaded ranges. We detected significant shifts in the relationships (i.e. trade-offs) (i) between plant height and flowering time and (ii) between leaf-stem biomass and grain yield between native and introduced plants, indicating that invasion was associated with changes to life-history dynamics that may confer competitive advantages over native vegetation. Specifically, we found that, at first flowering, introduced plants tended to be taller than native ones and that investment in leaf and stem biomass was greater in introduced than in native plants for equivalent levels of grain yield. Our study has demonstrated that climatic conditions may drive rapid adaption to novel environments in invasive plant species.

Current population status of the endangered Hog Deer Axis porcinus (Mammalia: Cetartiodactyla: Cervidae) in the Terai grasslands: a study following political unrest in Manas National Park, India ­

The Endangered Hog Deer Axis porcinus has experienced drastic population declines throughout its geographical range. There is limited knowledge of its current population status, particularly from northeastern India. In this study the population density of Hog Deer was assessed in Manas National Park, which was a deer stronghold prior to the armed conflict that lasted for almost two decades, resulting in depressed deer populations. With the cessation of conflict, efforts were invested by both government and conservation organisations for the recovery and conservation of charismatic fauna in the park. Studies on Hog Deer populations, however, were lacking and thus reliable information on current status is unavailable. Current population status and threats faced by Hog Deer were assessed to aid informed conservation decisions. Distance sampling techniques (line transects) were applied in the grassland habitat during the dry season of two consecutive years. The estimated Hog Deer density was 18.22±3.32 km-2. The potential threats to Hog Deer identified in Manas include habitat loss, habitat degradation due to spread of invasive plant species, illegal hunting, and other anthropogenic disturbances. Our study suggests that the Hog Deer population, though reviving, needs immediate conservation attention.

Complex response of vegetation to grazing suggests need for coordinated, landscape-level approaches to grazing management

Management of domesticated ungulates on grasslands has the potential to affect ecosystem function at landscape to global scales. In the southwestern United States, introduction of livestock in the 1800s corresponded with grassland degradation and dramatic shifts in vegetation, including the rapid spread of invasive plant species. In contemporary grasslands, however, evidence increasingly suggests that responsible grazing may enhance plant diversity in the region, though positive effects on diversity may or may not offer corresponding benefits to ecosystem function. Here, we examined the effects of grazing on land cover and functional composition of a semiarid grassland over a 20-year period. We found that high intensity grazing increased exposed soil and shifted community composition toward a greater proportion of annual and exotic species. This was particularly apparent following a severe drought event that initiated a significant loss of perennial plant cover, especially forbs, and was followed by a nearly 4-fold expansion of exotic species. Plots that were grazed at moderate levels consistently exhibited the lowest proportion of exotic species and were similar in functional group composition to exclosure plots. However, moderate grazing did increase soil exposure relative to exclosure plots. These findings suggest that moderate grazing could provide benefits to grassland ecosystem diversity and correlated ecosystem services like invasive species control and pollination services, while simultaneously increasing erosion, reducing water infiltration and altering nutrient cycling, due to increased soil exposure and disturbance. The potential for grazing to exert antagonistic effects on ecosystem services, depending on site conditions and grazing intensity, suggests that livestock management decisions should be tailored to individual management and conservation goals that address the inherent spatiotemporal variability of arid grasslands.