Species Composition Of Grasslands Research Articles

Species richness and composition of shrub-encroached grasslands in relation to environmental factors in northern China

Shrub encroachment has taken place in many of China’s northern grasslands. This study attempts to answer the following questions: which plant communities are present in these shrub-encroached grasslands (SEGs)? What are the species richness and composition of these communities? Which environmental factors determine the spatial distribution thereof? We investigated the community characteristics of 255 SEG plots with a size of 20 m × 20 m at 69 locations across grasslands in northern China. In each plot, paired 1-m² quadrats were established within shrub patches and the neighbouring grassy matrix to record herb species composition. The quantitative characteristics (abundance, coverage and height) of herbs were measured in 0.25-m² subquadrats, and soil samples were collected in the quadrats. Two-way indicator species analysis (TWINSPAN), detrended canonical analysis (DCA) and canonical correspondence analysis (CCA) were used for community clustering and ordination. The DCA and TWINSPAN results suggested that the SEGs in northern China can be divided into six community types: Potentilla fruticosa + Carex atrofusca, Spiraea hypericifolia + Festuca ovina, Caragana acanthophylla + Stipa sareptana, Caragana microphylla + Leymus chinensis, Caragana microphylla + Stipa klemenzii and Caragana tibetica + Cleistogenes songorica. At a regional scale, climate and soil nutrients controlled the spatial patterns of species richness and community composition of the SEGs in northern China. Temperature exerted a negative impact, whereas precipitation and nutrients had positive effects on species richness. Among the environmental factors used, climate was the major controller of the variations in community structure. These results provide new insights into the community composition of SEGs in China and enrich the global dataset of SEGs.

ENVIRONMENTAL FACTORS AFFECTING SEED GERMINATION OF COMMON TEASEL (Dipsacus fullonum)

ABSTRACT Common teasel is a widespread, invasive species that has been introduced in Buenos Aires province, Argentina, where it alters the species composition of protected areas and native grasslands. A better understanding of seed germination behavior is essential for predicting its invasion potential in new areas and would be useful for developing effective management strategies. This research, conducted under laboratory conditions, evaluated the influence of several environmental factors such as pH, constant temperature, osmotic stress, salt stress and dry storage, on germination and rate of germination of common teasel seed. Between-year variation in germination responses was also examined. Seed germination was not affected by different pH levels. Although common teasel seeds germinated over a range of temperatures from 6 to 36 oC, the optimum temperature was 22 oC. Common teasel seed germination showed moderate tolerance to osmotic stress and a relatively high tolerance to salt stress. No seed germination was observed at - 1 MPa and 640 mM of osmotic potential and salt concentration, respectively. Seed germination remained high (> 90%) after all the dry storage treatments. Besides, the response of seeds to germination parameters showed between-year variation. It was shown that common teasel is able to germinate over a broad range of environmental conditions. This capacity would explain, at least partially, why this species is so widely distributed and its great potential to invade new areas.

Mapping plant species in mixed grassland communities using close range imaging spectroscopy

Grasslands are one of the ecosystems that have been strongly affected by anthropogenic impacts. The state-of-the-art in monitoring changes in grassland species composition is to conduct repeated plot-based vegetation surveys that assess the occurrence and cover of plants. These plot-based surveys are typically limited to comparably small areas and the quality of the cover estimates depends strongly on the experience and performance of the surveyors. Here, we investigate the possibility of a semi-automated, image-based method for cover estimates, by analyzing the applicability of very high spatial resolution hyperspectral data to classify grassland species at the level of individuals. This individual-oriented approach is seen as an alternative to community-oriented remote sensing depicting canopy reflectance as the total of mixed species reflectance. An AISA+ imaging spectrometer mounted on a scaffold was used to scan 1m2 grassland plots and assess the impact of four sources of variation on the predicted species cover: (1) the spatial resolution of the scans, (2) complexity, i.e. species number and structural diversity, (3) the species cover and (4) the share of functional types (graminoids and forbs). Classifications were conducted using a support vector machine classification with a linear kernel, obtaining a median Kappa of ~0.8. Species cover estimations reached median r2 and root mean square errors (RMSE) of ~0.6 and ~6.2% respectively. We found that the spatial resolution and diversity level (mainly structural diversity) were the most important sources of variation affecting the performance of the proposed approach. A spatial resolution below 1cm produced relatively good models for estimating species-specific coverages (r2=~0.6; RMSE=~7.5%) while predictions using pixel sizes over that threshold failed in this individual-oriented approach (r2=~0.17; RMSE=~20.7%). Areas with low inter-species overlap were better suited than areas with frequent inter-species overlap. We conclude that the application of very high resolution hyperspectral remote sensing in environments with low structural heterogeneity is suited for individual-oriented mapping of grassland plant species.

Land management and biodiversity maintenance: a case study in grasslands in the Coastal Plain of Rio Grande do Sul

Coastal grasslands are one of the most threatened types of grasslands in the southern Brazil. To evaluate if areas with diff erent landuse history diff er in current grassland species composition and structure, four areas were selected according to current management: Entisols areas used for extensive livestock breeding (GR1 and GR2 sites); Alfi sols areas used for rice production with fallow periods (GRC), and for rotation with soybean (GSB). In each area, soil and grassland vegetation were characterized. We verifi ed that GR1, GSB, GRC and GR2 sites followed a decreasing order of species richness. Despite the higher richness found in GSB and GRC sites, few native perennial species with high coverage were recorded, due to dominating exotics and annuals. In contrast, grasslands used for pasture presented the typical vegetation features. For eff ective conservation eff orts, we highlight the importance to keep grasslands on both soil types.

Towards a mechanistic understanding of the effect that different species of large grazers have on grassland soil N availability

Abstract Herbivore grazing has major effects on soil nutrient dynamics in a variety of grassland ecosystems. Previous studies have examined how large herbivores as a group affect nutrient cycling, but little information is available on how assemblages of different herbivore species may influence nutrient cycling, and whether herbivore assemblage effects are influenced by plant community characteristics (e.g. composition, diversity) of the grazed grassland. We conducted a 5‐year, replicated grazing experiment to test the effects of different large herbivore assemblages (cattle grazing, sheep grazing, combined cattle and sheep grazing, no grazing) under moderate grazing intensity on soil nitrogen (N) mineralization rate in two types of grassland communities (high forbs/high diversity and low forbs/low diversity) in meadow steppe habitat of northeast China. Moreover, we examined two distinctly different pathways that herbivores could influence soil N availability: directly through urine and dung deposition and indirectly by shifting grassland species composition (i.e. the grass: forb ratio), thereby the quality of plant litter available to soil decomposers. We found that grazer effects on soil N availability (indexed with anion and cation adsorption strips) depended on herbivore assemblage, and the herbivore assemblage effects varied in the two types of grasslands. In one type of grassland characterized by low diversity, grazing by each of the herbivore assemblages enhanced soil N availability compared to the ungrazed plots, and mixed species (cattle and sheep) grazing had a greater effect than single species grazing. In high diversity grassland, single species herbivore grazing significantly increased soil N availability, but mixed grazing had no effect. Mixed linear modelling revealed that soil N availability was facilitated primarily by excreta additions to the soil and secondarily by the abundance of grasses. Synthesis. Grazers increased soil N availability directly by adding readily accessible N in urine and dung to the soil. Herbivores indirectly influenced soil N availability by altering the plant composition (grass: forb cover). Both mechanisms contributed to the variation in how different herbivore assemblages affected soil N availability in the two grassland types.

Species classification using Unmanned Aerial Vehicle (UAV)-acquired high spatial resolution imagery in a heterogeneous grassland

Investigating spatio-temporal variations of species composition in grassland is an essential step in evaluating grassland health conditions, understanding the evolutionary processes of the local ecosystem, and developing grassland management strategies. Space-borne remote sensing images (e.g., MODIS, Landsat, and Quickbird) with spatial resolutions varying from less than 1m to 500m have been widely applied for vegetation species classification at spatial scales from community to regional levels. However, the spatial resolutions of these images are not fine enough to investigate grassland species composition, since grass species are generally small in size and highly mixed, and vegetation cover is greatly heterogeneous. Unmanned Aerial Vehicle (UAV) as an emerging remote sensing platform offers a unique ability to acquire imagery at very high spatial resolution (centimetres). Compared to satellites or airplanes, UAVs can be deployed quickly and repeatedly, and are less limited by weather conditions, facilitating advantageous temporal studies. In this study, we utilize an octocopter, on which we mounted a modified digital camera (with near-infrared (NIR), green, and blue bands), to investigate species composition in a tall grassland in Ontario, Canada. Seven flight missions were conducted during the growing season (April to December) in 2015 to detect seasonal variations, and four of them were selected in this study to investigate the spatio-temporal variations of species composition. To quantitatively compare images acquired at different times, we establish a processing flow of UAV-acquired imagery, focusing on imagery quality evaluation and radiometric correction. The corrected imagery is then applied to an object-based species classification. Maps of species distribution are subsequently used for a spatio-temporal change analysis. Results indicate that UAV-acquired imagery is an incomparable data source for studying fine-scale grassland species composition, owing to its high spatial resolution. The overall accuracy is around 85% for images acquired at different times. Species composition is spatially attributed by topographical features and soil moisture conditions. Spatio-temporal variation of species composition implies the growing process and succession of different species, which is critical for understanding the evolutionary features of grassland ecosystems. Strengths and challenges of applying UAV-acquired imagery for vegetation studies are summarized at the end.

Longitudinal changes in species composition of forests and grasslands across the North Asian forest steppe zone

In the forest-steppe zone, the plant species composition under the forest, especially birch, canopy can be quite similar to that of zonal grasslands. Here we synthesize, for the first time, plant compositional data for forests and grasslands across the entire forest-steppe zone with the aim to address the questions how different are local species pools across different parts of the Asian forest-steppe zone and to what extent is the species composition of forests and grasslands similar and whether the degree of a difference between forests and grasslands is consistent along a large longitudinal gradient. To answer these questions, a transect of about 5,000 km was stretched from the west to the east, involving nine key areas. Based on 2,000 vegetation-plot records, we calculated Bray-Curtis Coefficients between forests and grasslands and between the individual areas. NMDS was used to compare species pools of forests and grasslands in the individual key areas in a gradient space. The forest and grassland floras differed in species composition in the individual areas, but the forests and grasslands of the same area displayed similar positions along the principal NMDS axis. We observed rather steep compositional changes along the longitudinal gradient, but quite a large set of species was shared between the key areas from the Ural Mountains to the Yenisei River. The North Asian forest-steppe of Western and Central Siberia can hence be considered a single entity in terms of species composition at the species pool level. Eastward from the Yenisei river, the species composition of both grasslands and forests changed suddenly, mirroring an important biogeographical boundary. Our results suggest that the forest-steppe zone should be viewed as a single biome that is characterized by an alteration of two compositionally and structurally distinct habitats, forest and grasslands, which, however, show similar patterns in terms of species pool size and local diversity.

Extended autumn drought, but not nitrogen deposition, affects the diversity and productivity of a Mediterranean grassland

Global change is affecting ecosystems worldwide. Nitrogen (N) deposition is increasing globally and climate change scenarios forecast an increase of prolonged autumn droughts particularly in the Mediterranean regions. Mediterranean grasslands occupy 1.3 million km2 of the terrestrial surface, host high biodiversity values and generate important ecosystem services. Understanding the effects of N deposition and prolonged autumn drought on the productivity and dynamics of Mediterranean grasslands is crucial to support the conservation of these ecosystems in a global change context.We assessed the effects of extended autumn drought and N deposition on the productivity, species diversity, and phenology of a Mediterranean grassland through a manipulative, greenhouse, experiment. We simulated three levels of extended drought: no drought, 50days and 100days of drought and two levels of N deposition: no N and N addition, through a factorial design experiment.Severe drought (100days) affected negatively grassland productivity, through a reduction of the growing season duration and accumulated growing degree days. Moderate drought (50days) affected productivity negatively but productivity values recovered to levels similar to those of the non-drought treatment. Severe and moderate drought delayed plant phenology decreasing significantly the number of individuals with mature flowers and with fruits or seeds. Plant functional groups responded differently to drought with productivity of forbs, but not productivity of graminoids and legumes, being negatively affected by moderate and severe drought. N addition did not affect grassland productivity, diversity or phenology.Our results anticipate effects of climate change on the productivity and species composition of Mediterranean grasslands.

Flooding effects on grassland species composition in the Azul creek basin, Argentina

From a hydrological point of view, the characteristic of the water behaviour in catchments so depressed as the Azul creek basin (centre of Buenos Aires province, Argentina) is water accumulation above the land surface. Thus, water on the ground does not have a single runoff direction, but moves in a disorderly, indefinite and unpredictable way. Considering that periodic floods are a typical disturbance of the region, the objective of this study is to analyse, under field conditions, the transformative effect of prolonged flooding on floristic composition, taking into account the different vegetation patches and their relative position over the relief, the chemical characteristics and the groundwater fluctuation, and some edaphic properties in each site. Vegetation samplings were performed during three consecutive springs, when the grassland was on different hydrological conditions due to very different rainfall precedent histories. A digital terrain model of the study area was built and a flow accumulation map was created from it. Pits were dug to describe edaphic variables and shallow wells were drilled for monitoring the groundwater characteristics. Flooding, in relation with surface and groundwater dynamics and soil characteristics, is the factor that determines and promotes the differentiation among sites that are relatively close, contiguous and even topographically in almost identical positions. So, some patches of vegetation get their differentiation through the limiting conditions of their soils, while others receive greater influence from the hydrodynamics to which they are subject. Thus, in this study it becomes evident how certain stands are floristically homogenised or differentiated over time according to their flooding conditions and, hence, according to the area from which they receive surface and groundwater flow. Also, results corroborate the way the water regime determines the structure and heterogeneity of plant communities in such environments.

Management intensity and temporary conversion to other land‐use types affect plant diversity and species composition of subtropical grasslands in southern Brazil

AbstractQuestionsWe investigated the effects of grassland management intensity and temporary conversion to other land uses on abiotic and biotic properties of subtropical grasslands. We used species‐rich permanent grasslands of medium management intensity (PG‐M) as a reference, and asked the following questions: (1) do permanent grasslands with low and high management intensities (PG‐L and PG‐H, respectively) have different plant diversity and species composition than reference grasslands; and (2) do secondary grasslands recovering from conversion to arable fields (SG‐A) or pine plantations (SG‐P) differ from permanent grasslands in their plant species composition and abiotic conditions?LocationHighland grasslands, Campos de Cima da Serra, Rio Grande do Sul (RS), Brazil.MethodsWe analysed variation in plant species composition and diversity among 80 grassland sites, including three types of permanent grassland and two types of secondary grassland. An indicator species analysis was used to identify characteristic species for the different land‐use types. We used a linear discriminant analysis to investigate differences in soil conditions among land‐use types.ResultsBoth PG‐L and PG‐H differed from PG‐M regarding plant species composition. Although PG‐L shared many typical grassland species with PG‐M, their communities were generally less diverse. PG‐H, on the other hand, not only had fewer species but also deviated from PG‐M in species composition. Secondary grasslands on former arable fields and plantations differed from PG‐M in species composition and showed lower diversity. Soil conditions of SG‐P were similar to those of PG‐L and PG‐M, but they were distinct from those of PG‐H and SG‐A.ConclusionsAll land‐use types showed deviations from reference grasslands (PG‐M). The decrease in the number of species in PG‐L may be reversed if traditional management intensity is re‐introduced, whereas strong compositional changes in SG‐P may require the re‐introduction of grassland species. This is also true for PG‐H and SG‐A: both showed marked deviations from reference grasslands in biotic and abiotic components. Overall, restoration of altered land‐use types to near‐natural subtropical grassland seems feasible, but suitable techniques have to be developed.

Mountain Nardus stricta grasslands as a relic of past farming – the effects of grazing abandonment in relation to elevation and spatial scale

The decline of grazing management in mountains has resulted in a dramatic decrease of areas occupied by semi-natural grasslands with Nardus stricta. In order to effectively protect existing fragments, it is important to understand the mechanisms governing the organization of communities with Nardus. The aim of this study was to quantify the relative impact of the time span of abandonment and also of topographic and spatial factors on the species composition of montane and subalpine grasslands. Old and recent phytosociological data from three distinct regions in the northern part of the Carpathians were compared by indirect and direct ordination methods. The majority of the explained variation at the supraregional scale was associated with the joint effect of spatial trends and elevation above sea level. At the intraregional scale, the contribution of land use abandonment was much greater, particularly at low elevations with warmer and drier environmental conditions. The results suggest that the effects of grazing abandonment depend on natural factors such as elevation and climate. Conservation programmes for Nardus grasslands should take into consideration their position along the elevational gradient. In the lower montane zone, management measures should ensure a low nutrient level to restrict the spread of nitrophilous plant species.

Shrub encroachment influences herbaceous communities in flooded grasslands of a neotropical savanna wetland

AbstractQuestionThe encroachment of woody species has been globally reported over much of arid and semi‐arid biomes, and has been associated with a decrease in cover and number of herbaceous species. How does the encroachment of a woody shrub affect herbaceous community structure and species composition in grasslands of a wetland ecosystem?LocationSeasonally flooded grasslands in a Neotropical Hyperseasonal Savanna, the Pantanal wetland, Brazil.MethodsWe investigated the effect of the encroaching plant Combretum laxum on a herbaceous community from seasonally flooded grasslands in the Pantanal wetland using 29 vegetation samples representing encroachment at different spatio‐temporal stages. The point quadrat method was used to acquire vegetation data, as plant cover, species richness (S) and Shannon‐Wiener diversity index (H’). We evaluated the existence of stages of encroachment related to differences in vegetation structure and species composition using non‐metric multidimensional scaling ordination and analysis of similarity. The response of the herbaceous community to shrub advance was analysed using linear and quadratic polynomial regression models. Model fitness was tested using the ACI.ResultsThe advance of the woody encroaching plant C. laxum over the seasonally flooded grassland occurs in three stages: grassland stage, shrub islands stage and shrubland stage. The initial advance of C. laxum over the grassland, represented by the shrub islands stage was correlated to an increase in species richness and a decrease in important native forage grasses. Critical changes in the herbaceous community were observed when the encroaching plant covered >30% of the periodically flooded grassland, when the richness of herbaceous species dropped from 22 to four.ConclusionsWoody encroachment causes impoverishment and simplification of the herbaceous community. The shift from a grass‐ to a shrub‐dominated state is related to the reduction in important grassland‐obligate species, forage resources for herbivore livestock and wild animals, affecting the ecological dynamics and the economy of rangelands. Conservation of these grassland ecosystems depends on rangeland management practices guided by scientific knowledge on the causes and consequences of plant community changes.

The nearest-plant method is robust and powerful enough for different survey teams to monitor change in mesic grassland species composition

A long-term rangeland monitoring programme needs to employ a field survey technique that is practicable, precise, powerful enough to distinguish change, not prone to worker bias, and able to distinguish real change from operator error arising from staff turnover. These criteria were used to evaluate a widely used grassland sampling technique in South Africa – the nearest-plant (with 200 points) method (NP) – against common alternatives, namely NP excluding forbs (NP-nf), the plant number scale (PNS; a cover-abundance method) and quadrat frequency (QF), using multivariate ordination and permutation tests. Four trained teams surveyed four grasslands using each method. PNS took more than twice as long as the other techniques, which were similarly rapid. Estimates of composition using NP methods were the most precise and PNS was least repeatable, with QF intermediate. Compositional differences between sites were most finely distinguished using NP-nf, followed by NP and QF. PNS was able to detect only marked differences and had the greatest potential for surveyor bias. The NP method, with or without including forbs, is therefore recommended for monitoring the species composition of mesic, dense grassland. Some suggestions for monitoring agencies on how best to use multivariate methods are presented.

Plant species composition and potential feed value of permanent grasslands in the central part of Drahanská vrchovina Upland

In multifunctional agriculture, permanent grasslands (PG) present an important culture which keeps the soil in the continuous production status while helping to shape the landscape and protecting biodiversity, plus it has a number of other non-productive functions. The aim of the study was to evaluate, using the “Inventory and Classification of PG” method, species composition and the feed value of fodder in permanent grasslands in a specific farming company (ZEMSPOL Sloup a.s.) located in the area of the Drahanská vrchovina Upland. Multivariate analysis of PCA identified four categories of sites in the area: meadows/pastures with a higher proportion of legumes and grass species and potentially higher quality of fodder; meadows/pastures with a low proportion of grass species, a high proportion of other herbs and a very low potential feed value of fodder, etc. Most of PG are completely lacking legumes which supply nitrogen to the vegetation and are a major improvement for fodder production and its quality. Infestation with broad-leaf sorrels (Rumex acetosa /L./ and Rumex obtusifolius /L./) may be potential risk in the future. Additional seeding of grass-clover mixtures seems to be a useful way to improve the botanical composition of meadows and pastures in the area of interest, whether it would involve applying a strip or harrow seeder.

Rainfall fluctuations and vegetation patterns in alkali grasslands - using self-organizing maps to visualise vegetation dynamics

Knowledge about the drivers of vegetation dynamics in grasslands is fundamental to select appro-priate management for conservation purposes. In this study, we provide a detailed analysis of vegeta-tion dynamics in alkali grasslands, a priority habitat of the Natura 2000 network. We studied vegetation dynamics in five stands of four alkali grassland types in the Hortobagy National Park (eastern Hunga-ry), between 2009 and 2011. We analysed the effect of fluctuations in precipitation on both the overall vegetation composition and on the cover of each species using Self Organizing Map neural networks (SOM). We found that SOM is a promising tool to reveal plant community dynamics. As we analysed species cover and overall vegetation composition separately, we were able to identify the species re-sponsible for particular vegetation changes. Fluctuations in precipitation (a dry season, followed by a wet and an average season) caused quick shifts in plant species composition because of an increasing cover of halophyte forbs, probably because of salinisation. We observed a similar effect of stress from waterlogging in all studied grassland types. The species composition of Puccinellia grasslands was the most stable over the three years with varying precipitation. This was important as this grassland type contained many threatened halophyte species. Self-organising maps revealed small-scale vegetation changes and provided a detailed visualisation of short-term vegetation dynamics, thus we suggest that the application of this method is also promising to reveal community dynamics in more species-rich habitat types or landscapes.

Rastlinski Svet Dolomitov

In Europe, the management of semi-natural grasslands is changing steadily in extent and intensity. These changes represent a serious threat to one of the most species-rich habitats in Europe; therefore, the related shifts in species composition should be assessed by means of sound scientific. We describe a new methodology aimed at: (i) quantifying the temporal changes in vascular plant species composition of semi-natural grasslands; (ii) identifying the environmental and management variables that drive patterns of change. Our approach consists of a diachronic analysis based on historical phytosociological data associated with detailed vegetation maps. To describe and test our methodology, in 2013 we re-visited 24 historical plots of Bromus erectus grasslands that were first sampled in 1982. To designate the new sampling sites, we combined the topographic and typological information available for the historical plots with the spatial information of the associated map. The degree of change in species composition was calculated through ordination techniques; multivariate distances were used in a regression analysis to identify the environmental variables responsible for patterns of compositional change. Our worked example demonstrated that species composition has changed significantly in the last 30 years, with patterns that have been substantially influenced by topography and landscape structure.

Sward-height patches under intensive and extensive grazing density in an Agrostis capillaris grassland

Patchiness is one of the important features of grazed temperate grasslands, but little is known about the structure of sward height patches under different grazing intensities. The present study examined the effect of continuous intensive and extensive stocking of heifers on the proportions of sward-height patch categories (short ≤ 5cm, moderate 5.5–10 cm, tall ≥ 10.5 cm) and their plant species composition in an Agrostis capillaris grassland. A four-year study was performed on an upland grassland maintained under a long-term grazing experiment in the Jizerske hory Mts (Jizera Mountains), Czech Republic. The contrasting stocking densities form the differences in the proportion of sward-patch categories and generated a similar level of patch heterogeneity, which was mainly affected by the proportion of tall- and short-sward patches. The floristic composition of patches within the same sward height category depended upon stocking density. Moderate and tall patches under a given stocking density had similar botanical composition. Vegetation within short patches differed considerably from that of other patches under extensive grazing whereas under intensive grazing the differences between short, moderate and tall sward-height patches were small. The findings show that grazing intensity is a key driver of the proportion as well as the floristic composition of sward-height patches in grasslands dominated by A. capillaris. These findings have implications for nature conservation, as they support the recommendation for extensive management of upland grasslands.

Manual weeding of Rumex obtusifolius and its effects on plant species composition in organically managed grassland

Rumex obtusifolius is a troublesome weed especially in organically managed grasslands. Manual weeding is commonly used for R. obtusifolius control, but its effectiveness and effect on plant species composition in upland grassland has never been investigated. Therefore the aim of our study was to reveal the effect of manual weeding by digging out R. obtusifolius taproots to depths of 5 or 15 cm, either once or twice, in: (i) presence of R. obtusifolius plants; (ii) plant species composition. Additional treatments were grazed and unmanaged grassland (both without digging out R. obtusifolius taproot). Digging out taproots twice, to 15 cm, reduced the presence of R. obtusifolius significantly. Grazing without digging out taproots was the treatment that was most favourable for R. obtusifolius plants. Manual weeding had no significant effect on species richness. The empty spaces after plant removal were filled by nutrient-demanding species (Poa pratensis, Poa trivialis, Festuca pratensis and Lolium perenne, Trifolium repens and Taraxacum sp.). On unmanaged grassland the number of R. obtusifolius plants decreased, species richness was reduced, but this allowed the spread of other tall weedy species (Urtica dioica, Galium album and Elytrigia repens). Digging out taproots to a depth of 15 cm, performed twice, can be an effective method for R. obtusifolius control in organically managed grasslands, as this procedure eliminated the majority of R. obtusifolius plants. However, the use of this weeding method over large areas of grassland is limited due to time-consuming and hard physical work.

Parthenium hysterophorus in Nepal: a review of its weed status and possibilities for management

SummaryThe rapid expansion of the alien invasive Parthenium hysterophorus is a new agricultural and environmental problem for Nepal. Although the weed was first recorded in 1967, the most significant expansion has occurred in the last 20 years. The weed is thought to have entered Nepal from India and currently is found in the Tarai, Siwalik and hill regions of Nepal. A CLIMEX modelling projection has shown these regions to be climatically suitable for the growth of P. hysterophorus, both under the present and a future projected increased temperature. From the initially invaded roadside vegetation, the weed has now spread into cropping land and forests. Vehicle movement and transportation of agriculture products are the main means by which its seed is spreading. The weed has reduced plant species richness and changed species composition in grasslands, while fodder collectors have developed contact dermatitis from the plant. To date, no sustainable management strategy has been developed for this weed. However, the fortuitous arrival of the biological control agents Zygogramma bicolorata and Puccinia abrupta var. partheniicola has had some impact upon the weed's growth and abundance. A CLIMEX modelling projection identifies many suitable locations for Z. bicolorata outside of its present range and within areas where the weed is likely to spread, both under the present and under a future projected climate of increased temperature. Mapping of the currently invaded areas, management through community involvement and further releases of new and redistribution of current biological control agents are required to manage P. hysterophorus in Nepal.

Vpliv prostoživečih velikih rastlinojedov na travniške ekosisteme

Free-ranging large herbivores are keystone species in terrestrial ecosystems, and have an important ecological role by affecting both the structure and the function of plant communities and other groups of organisms. Large herbivores often increase plant diversity especially in more productive grasslands such as temperate grasslands in Europe. Additionally, other important effects of ruminants are redistribution of nutrients by feeding and subsequent excretion of urine and dung, soil compaction and erosion via trampling and dispersal of seeds, respectively. In Europe, populations of several ruminants species are increasing both in number and geographical distribution, and problems connected with effects of grazing of red deer (Cervus elaphus L.) on grassland in some locations in Slovenia have been increasing as well. Several areas of the Inner Carniola and Kočevje regions have been overgrown with forest, and these areas have the highest density of red deer. Therefore, the pressure of red deer on the remaining grasslands is increasing and may cause important economic loss for land owners. Ungulates can affect the economic profitability of grasslands also indirectly, through the impact on species composition of grasslands and by altering the overall productivity of soil. For proper management of their populations both direct and indirect ecological impacts and value of free-ranging ungulates have to be known. Therefore, an overview of foreign and Slovene studies related to the impacts of free-ranging ruminants on grassland ecosystems is presented in the paper.