Is habitat selection by the Cabrera vole (Microtus cabrerae) related to food preferences?

The Cabrera vole (Microtus cabrerae) is an Iberian endemism considered threatened both in Portugal and Spain. This vole is often referred to as a tall perennial grassland community specialist. However, a recent study revealed that the Cabrera vole exploits a wide variety of grasslands in south Portugal. The major aim of the present study was to test the palatability of 21 plant species of this region occurring within or outside typical perennial grassland colonies in order to assess vole's food preferences. Results showed a major consumption of monocotyledons and annual plants (such as Festuca ampla, Agrostis castellana, Brachypodium distachyon, B. phoenicoides and Vulpia geniculata), but no relationship was found between diet selection and perennial grassland plant communities. The preference of voles for annual species, occurring more abundantly outside the colonies, raises the hypothesis that the establishment of a colony might be determined by plant species abundance and persistence over the year, rather than by their palatability. This seems to be particularly evident in this region, where summer meteorological conditions make vegetation unavailable outside the colonies.     

The role of below-ground competition during early stages of secondary succession: the case of 3-year-old Scots pine (Pinus sylvestris L.) seedlings in an abandoned grassland

In abandoned or extensively managed grasslands, the mechanisms involved in pioneer tree species success are not fully explained. Resource competition among plants and microclimate modifications have been emphasised as possible mechanisms to explain variation of survivorship and growth. In this study, we evaluated a number of mechanisms that may lead to successful survival and growth of seedlings of a pioneer tree species (Pinus sylvestris) in a grass-dominated grassland. Three-year-old Scots pines were planted in an extensively managed grassland of the French Massif Central and for 2 years were either maintained in bare soil or subjected to aerial and below-ground interactions induced by grass vegetation. Soil temperatures were slightly higher in bare soil than under the grass vegetation, but not to an extent explaining pine growth differences. The tall grass canopy reduced light transmission by 77% at ground level and by 20% in the upper part of Scots pine seedlings. Grass vegetation presence also significantly decreased soil volumetric water content (Hv) and soil nitrate in spring and in summer. In these conditions, the average tree height was reduced by 5% compared to trees grown in bare soil, and plant biomass was reduced by 85%. Scots pine intrinsic water-use efficiency (A/g), measured by leaf gas-exchange, increased when Hv decreased owing to a rapid decline of stomatal conductance (g). This result was also confirmed by δ ¹³C analyses of needles. A summer ¹⁵N labelling of seedlings and grass vegetation confirmed the higher NO₃ capture capacity of grass vegetation in comparison with Scots pine seedlings. Our results provide evidence that the seedlings' success was linked to tolerance of below-ground resource depletion (particularly water) induced by grass vegetation based on morphological and physiological plasticity as well as to resource conservation.     

Plant communities and phytogeographical position of a large depression in the Great Chaco,Argentina

A survey is presented of the vegetation of the central region of the Santafesinian Chaco (Argentina), a scarcely populated flat area of 20 000 km², with seasonal flooding. Soils have a strong halo-hydromorphic character and vegetation is basically halophilous. Trees are scarce and most communities are savannas, grasslands or swampy vegetation. Twenty-three communities are described, some of them with several variants. The most widespread communities areSpartina argentinensis grasslands,Elyonurus muticus savannas and a complex of hygrophilous communities. The most important communities are distributed in relation to a topographical gradient, and their structure is shaped by recurrent flooding and fire disturbance. Most of the area is virgin land with very little human interference. The phytogeographical position of the area is discussed. Nomenclature: Burkart, A. 1969, 1974, 1979. Flora ilustrada de Entre Rios, INTA, Buenos Aires, and Cabrera, 1963, 1965a, b, 1967, 1968, 1970. Flora de la Provincia de Buenos Aires, INTA, Buenos Aires.     

Effects of kangaroo rat exclusion on vegetation structure and plant species diversity in the Chihuahuan Desert

Long-term (1977–90) experimental exclusion of three species of kangaroo rats from study plots in the Chihuahuan Desert resulted in significant increases in abundance of a tall annual grass (Aristida adscensionis) and a perennial bunch grass (Eragrostis lehmanniana). This change in the vegetative cover affected use of these plots by several other rodent species and by foraging birds. The mechanism producing this change probably involves a combination of decreased soil disturbance and reduced predation on large-sized seeds when kangaroo rats are absent. Species diversity of summer annual dicots was greater on plots where kangaroo rats were present, as predicted by keystone predator models. However, it is not clear whether this was caused directly by activities of the kangaroo rats or indirectly as a consequence of the increase in grass cover. No experimental effect on species diversity of winter annual dicots was detected. Our study site was located in a natural transition between desert scrub and grassland, where abiotic conditions and the effects of organisms may be particularly influential in determining the structure and composition of vegetation. Under these conditions kangaroo rats have a dramatic effect on plant cover and species composition.     

Dry grassland plant diversity conservation using low-intensity sheep and goat grazing management: case study in Prague (Czech Republic)

After abandonment, dry grassland (Festuco-Brometea) areas decline due to gradual overgrowing by woody species and the expansion of perennial tall grass species. Dry grassland vegetation was formed by extensive livestock grazing, thus grazing is considered one of the most natural methods for managing this type of vegetation. Six years after introducing low-intensity sheep and goat grazing in seven nature reserves in Prague (Czech Republic), the following impact of this management on dry grassland vegetation was observed: The cover of expansive woody species, particularly Ligustrum vulgare, and to a smaller extent Cornus sanguinea and Prunus spinosa declined. In addition, a significant, long-term declining trend of the expansive species Arrhenatherum elatius was also observed. Also the cover of Pimpinella saxifraga and Allium senescens declined significantly with regard to statistical evaluation. On the contrary, the cover of Achillea millefolium, Centaurea stoebe, Securigera varia, Elytrigia repens, Erysimum crepidifolium, Falcaria vulgaris, Fallopia convolvulus and Verbascum lychnitis increased. The cover of species characteristic of dry grasslands (Festuco-Brometea) increased significantly. No changes were observed in the number and cover of the Red List species. In addition, the presence of nitrophilous and ruderal species increased. Species diversity also significantly increased. From our findings we can conclude that managing dry grasslands with low-intensity grazing can help to keep dry grassland vegetation in good condition and conserve its plant diversity. Nomenclature: Kubát et al. (2002) for taxa and Moravec et al. (1995) for syntaxa.     

Regeneration of threatened alkali steppe vegetation after a heavy disturbance by disk tillage

Several methods of tillage are among the practices most destructive to inland saline grasslands, and can result in their complete deterioration. Despite the high frequency of habitat destruction by these means, the recovery of the saline vegetation and regeneration abilities of halophytes are still not sufficiently known. The reaction of inland saline grasslands to disk tillage was studied on the Jatov site located in the Pannonian bioregion of Central Europe. Changes in species composition were tested using ordination methods (DCA, CCA). Although the species composition recovered to a certain extent after the 4 years following the disturbance, the original zonation of halophytic vegetation was disturbed and did not recover. Disturbance primarily suppressed perennial halophytes and promoted the occurrence of species with a ruderal strategy. Testing of halophyte reaction to tillage showed the contracting responses of various halophytic species. The species Atriplex littoralis, Plantago maritima and Matricaria recutita reacted positively to tillage due to the reduced competition. The species Artemisia santonicum subsp. patens and Dichodon viscidum were suppressed by tillage in initial stages, but later recovered their populations. Only A. santonicum subsp. patens was able to return to the abundance seen before the disturbance. The only halophytic species which was unable to recover was a shallow-rooted grass Puccinellia distans. Our study showed that a Pannonian alkali steppe is able to recover quite quickly after tillage, if the soil disturbance is shallow and subsequent management takes place. Some halophytes may even profit for a short time from tillage, but the original species composition cannot be restored in the short term.

     

Influence of livestock grazing on vegetation in a saline area in Northeast Thailand

The influence of grazing by water buffalo (Bubalas bufalis) and cattle (Bos taurus) was estimated for vegetation inside and outside cages in a saline area at Khon Kaen, Northeast Thailand. The home range of water buffalo and cattle shifted in response to the period of rice cultivation: during the rice-growing season these animals grazed on roadsides and abandoned places such as the study area; after rice harvest they grazed mainly rice stubble on the paddy. The vegetation in the study area was divided into three types: 1) dominated by the annual grassesChloris barbata andIschaemum rugosum; vegetational cover and plant height in the cage increase due to the increase of these grasses; 2) thorny shrub patch ofMaytenus mekongensis; other species in this patch almost died a year after experimental elimination of this shrub; this salt-tolerant shrub not only protected the co-existing species from grazing, but also suppressed salt accumulation; 3) almost pure stand ofPanicum repens; livestock preferred this perennial grass over others. Electrical conductivity (EC) of surface soil did not increase under the vegetation protected from grazing. Litter and other organic matter in the soil suppressed the upward movement of brine. Grazing led to an increase of bare ground where NaCl accumulated, and modified the heterogeneity of vegetation, which was reflected in the degree of salt accumulation.     

Restoration of species‐rich flood‐plain meadows from abandoned arable fields in NE France

Abstract. Attempts to restore species‐rich flood‐plain meadows from abandoned arable fields in the valley of the river Meuse, NE France, were studied. The study area was sown with a commercial seed mixture, composed of Phleumpratense, Festuca pratensis, Lolium perenne and Trifolium repens. The above‐ground vegetation in the study area 1, 2 and 3 yr after restoration was compared to (1) the vegetation present during the previous 5‐yr fallow stage and (2) target flood‐plain meadows. Before restoration, the above‐ground fallow vegetation was dominated by ruderal and annual species, while only very few meadow species were present. Sowing led to tall, dense vegetation, mainly dominated by the sown species. Ruderal and annual species had decreased 3 yr after restoration, but target species were still poorly represented. Species richness was significantly lower in the sown site than in the semi‐natural target meadows and the vegetation had a different composition. Analysis of the soil seed bank of the restored meadow showed that only a few meadow species were present and that it was dominated by a few ruderal species. Three years after sowing, the vegetation of our experimental site is moving slowly towards the target communities but impoverished seed sources seem to limit the success of this restoration operation and will lead to under‐saturated communities.     

Responses to fertility and disturbance in a low-diversity grassland

We examined variation in species composition in a low-diversity, anthropogenic grassland in response to 11 years of nitrogen (N) manipulation and disturbance. The species-poor grassland (2–3 species/0.5 m²) represents a wide spread vegetation type (>10 million ha in North America) dominated by the introduced perennial grasses Bromus inermis and Agropyron cristatum. Four levels of N and three of soil disturbance were applied in all combinations to plots (5 × 15 m, N = 120) in a completely randomized design each year. Seeds or transplants of 47 species were added to ensure that dispersal was not a barrier to changes in species composition. After 11 years of treatment, all but the most disturbed plots continued to be dominated by B. inermis. The cover of the second-most abundant species, A. cristatum, decreased with disturbance but did not vary significantly with N. Despite the lack of changes in the identity of the dominant species, our environmental manipulations strongly influenced ecosystem characteristics. Added N increased soil available N, and decreased the cover of bare ground and light availability. Soil disturbance decreased aboveground biomass, and increased the cover of bare ground and light availability. Sawdust application, designed to decrease N availability, significantly reduced community biomass, and increased light availability and the cover of bare ground, but did not alter nutrient availability or species composition. The results highlight the difficulty of restoring diversity in species-poor, anthropogenic communities dominated by introduced species, and thus the importance of conserving remnants of diverse natural grasslands.     

Sawdust Addition Reduces the Productivity of Nitrogen‐Enriched Mountain Grasslands

Anthropogenic nutrient enrichment of mountain grasslands has boosted grasses and fast‐growing unpalatable plants at the expense of slow‐growing species, resulting in a significant loss in biodiversity. A potential tool to reduce nutrient availability and aboveground productivity without destroying the perennial vegetation is carbon (C) addition. However, little is known about its suitability under severe climatic conditions. Here, we report the results of a 3‐year field study assessing the effects of sawdust addition on soil nutrients, aboveground productivity, and vegetational composition of 10 grazed and ungrazed mountain grasslands. Of particular interest was the effect of C addition on grasses and on the tall unpalatable weed Veratrum album. After 3 years, soil pH, ammonium, and plant‐available phosphorus were not altered by sawdust application, and nitrate concentrations were marginally higher in treatment plots. However, the biomass of grasses and forbs (without V. album) was 20–25% lower in sawdust‐amended plots, whereas the biomass of V. album was marginally higher. Sawdust addition reduced the cover of grasses but did not affect evenness, vegetation diversity, or plant species richness, although species richness generally increased with decreasing biomass at our sites. Our results suggest that sawdust addition is a potent tool to reduce within a relatively short time the aboveground productivity and grass cover in both grazed and ungrazed mountain grasslands as long as they are not dominated by tall unpalatable weeds. The technique has the advantage that it preserves the topsoil and the perennial soil seed bank.     

The seedbanks of the Breckland heaths and heath grasslands, eastern England, and their relationship to the vegetation and the effects of management

The vegetation and the associated germinable seedbank of a range of heath and grass heath communities in Breckland, eastern England, were compared. The composition of vegetation and seedbank were similar for heather-dominated communities due to the predominance of Calluna vulgaris . Recent rotovation of previously heather-dominated communities invaded by Deschampsia flexuosa reduced the number of emerging C. vulgaris seedlings by more than 80%. The composition of seedbanks of calcicolous grasslands differed considerably from the vegetation, with a significant contribution from many ruderal species not present in the vegetation and an absence of important species such as Pilosella officinarum. Acidic grasslands were intermediate between calcicolous grasslands and heather-dominated heathlands, with seedbanks characterized by high densities of Rumex acetosella and a number of ruderal species that were absent or rare in the vegetation. The composition of the seedbank of more mesotrophic grasslands suggests that the imposition of some form of disturbance may recreate more open grasslands typical of Breckland.     

Population and clonal level responses of a perennial grass following fire in the northern Chihuahuan Desert

Relationships involving fire and perennial grasses are controversial in Chihuahuan Desert grasslands of southern New Mexico, USA. Research suggests that fire delays the resprouting of perennial grasses well after two growing seasons. However, such results are confounded by livestock grazing, soil erosion, and drought. Additionally, post-fire grass responses may depend on initial clone size. We evaluated the effects of fire, grazing, and clone size on Bouteloua eriopoda (black grama) in southern New Mexico grasslands. Four 2-ha plots were established in each of four sites. Fire and grazing were applied or not applied in 1999 such that four treatment combinations were assigned randomly to plots within each site. Within each plot, small (0–10 cm² basal area), medium (10–30 cm²), and large ( > 30 cm²) clones were initially mapped in five 0.91-m² quadrats where grass attributes and litter cover were evaluated before and at the end of two growing seasons following fire. Maximum fire temperature was also measured. At a population level, canopy and litter cover were each approximately 50% less in burned than unburned areas. However, compared to initial levels, canopy height had increased by 10% at the end of the study, regardless of fire. At a clonal level, basal cover reductions were attributed mostly to large clones that survived fire. Smaller clone densities had decreased by as much as 19% in burned compared to unburned areas, and fire reduced the basal cover of medium clones. Basal and canopy cover, recruitment, and clone basal area decreased with increased fire temperatures. Almost all responses were independent of grazing, and interactive effects of grazing and fire were not detected. Fire did not kill all perennial grass clones, regardless of size. However, rapid responses were likely influenced by above-average precipitation after fire. Future studies in desert grasslands should examine how perennial grass dynamics are affected by fire, precipitation patterns, and interactions with grazing.     

Reversal of fortune: plant suppression and recovery after vole herbivory

It is not clear how plant species preferred as forage by rodents persist in prairie vegetation. To test permanence of suppression of wet-mesic prairie vegetation by vole (Microtus pennsylvanicus) herbivory in synthetic experimental communities, access treatments were reversed after 9 years of vole exclusion or access. Between 1996 and 2004, rye grass Elymus virginicus (Poaceae) and tick-trefoil Desmodium canadense (Fabaceae) achieved mean cover of up to 30 and 25%, respectively, in plots where voles were excluded, but disappeared from plots where voles had access. To determine whether these species remained vulnerable to vole herbivory as established adults, and to determine whether the species could recover if vole herbivory were removed, access treatments were reversed at the end of the 2004 growing season and monitored through 2007. Repeated measures ANOVA demonstrated dramatic vole suppression of established E. virginicus, but not D. canadense, indicating continuing vulnerability of the grass but not of the adult legume. Release from vole herbivory resulted in re-growth of rye, but not tick-trefoil, which was apparently suppressed by established vegetation. Two additional common planted species did not respond to treatment reversal, nor did 11 much less common planted species that comprised a minor portion of the vegetation. Dominant perennial black-eyed Susan Rudbeckia subtomentosa (Asteraceae) did not change in plant numbers by year or treatment, but expanded or contracted in stems per plant and cover as E. virginicus was suppressed or released by vole herbivory or its absence. Results indicate that preferred food plants may persist through capacity to quickly recover during periods of relative vole scarcity, or reach a refuge in maturity.     

Disturbance governs dominance of an invasive forb in a temporary wetland

Dominance of invasive species is often assumed to be due to a superior ability to acquire resources. However, dominance in plant communities can arise through multiple interacting mechanisms, including disturbance. Inter-specific competition can be strongly affected by abiotic conditions, which can determine the outcome of competitive interactions. We evaluated competition and disturbance as mechanisms governing dominance of Phyla canescens (hereafter lippia), an invasive perennial forb from South America, in Paspalum distichum (perennial grass, hereafter water couch) meadows in floodplain wetlands of eastern Australia. Water couch meadows (in the study area) are listed under the Ramsar Convention due to their significance as habitat for migratory waterbirds. In the field, we monitored patterns of vegetation boundaries between the two species in response to flooding. Under controlled glasshouse conditions, we explored competitive interactions between the native water couch and lippia subject to different soil moisture/inundation regimes. We did this using a pairwise factorial glasshouse experiment that manipulated neighbor density (9 treatments) and soil moisture/inundation (4 treatments). In the field trial, inundation increased the cover of water couch. Under more controlled conditions, the invader had a competitive effect on the native species only under dry soil conditions, and was strongly inhibited by inundation. This suggests that dry conditions favor the growth of the invader and wetter (more historical) conditions favor the native grass. In this system, invader dominance is governed by altered disturbance regimes which give the invader a competitive advantage over the native species.     

Seed dispersal in the dung of large herbivores: implications for restoration of Renosterveld shrubland old fields

Species-rich, winter-rainfall, microphyllous Renosterveld vegetation in the Western Cape Province of South Africa has largely been transformed for production of wheat and wine. Remaining fragments thus have high conservation value. Abandoned old fields adjacent to natural vegetation fragments could potentially be restored as corridors and habitat for indigenous flora and fauna. We hypothesised that indigenous antelope maintained in a matrix of natural vegetation and abandoned field could play a role in restoration of Renoserveld via seed dispersal.We collected dung of indigenous ungulates in an abandoned field at various distances from natural Renosterveld vegetation, in order to assess the potential of large herbivores to contribute to restoration of plant diversity through seed dispersal. Emerged seedlings from the collected dung represented 29 forb, 13 grass, four sedge, four geophyte and one shrub species. The most abundant emerging seedlings were lawn grass Cynodon dactylon (38%), alien pasture grasses (31%) and indigenous geophyte Romulea rosea (12%). Whereas seeds of annual forbs and grasses were dispersed, only one shrub species was dispersed at very low density. We concluded that large herbivores could retard the rate of recovery of Renosterveld vegetation because viable seeds of herbaceous plants, particularly alien annual grasses and lawn-grasses were more abundant in the dung than the shrub, geophyte or perennial tussock grass species that characterise this vegetation type.     

Variability of the <Emphasis Type="Italic">Molinion</Emphasis> meadows in Slovakia

Nine vegetation types were distinguished using cluster analysis within Molinion meadows in Slovakia. Vegetation of cluster 1 occurs on most acidic soils and is characterized by the occurrence of species of the Caricion fuscae alliance and of the Nardus grasslands. Vegetation of cluster 2 is also found on rather acidic soils but in contrast to cluster 1 vegetation it contains species of base-rich sites, such as Betonica officinalis, Galium boreale or Serratula tinctoria. Vegetation of cluster 3 occurs in wet base-rich habitats and often contains species of the Caricion davallianae alliance. Species of dry and Nardus grasslands are typical for vegetation of cluster 4, which is found at the driest sites and is confined to oligotrophic sandy soils. Vegetation of clusters 5 and 6 occurs on moist mesotrophic soils. Their species composition is quite similar, the main difference being that the former includes species-poor relevés and the latter includes species-rich relevés. Relevés of cluster 7 include species of dry grasslands and some ruderal species and represent degraded types of inundated floodplain meadows of the Deschampsion alliance. Vegetation of clusters 8 is characterized by species of the Phragmito-Magnocaricetea class and of the Deschampsion alliance, and occurs in wet nutrient-rich habitats. Vegetation of cluster 9, which usually develops from vegetation of cluster 8 due to decrease in the ground-water table, often contains species of dry grasslands and mesic meadows. Except for relevés of clusters 1 and 7, all others can be assigned to the Molinietum caeruleae Koch 1926 association. Cluster 1 corresponds to the Junco effusi-Molinietum caeruleae Tüxen 1954 association. Average Ellenberg indicator values for relevés, which were passively projected on the ordination biplot of detrended correspondence analysis, showed that the first ordination axis correlates with nutrients, soil base status and temperature, and second axis with moisture.     

Food Preference of Wireworms Analyzed with Multinomial Logit Models

Many species of wireworms (larvae of click beetles, Elateridae) are poly- phagous root herbivores. In grasslands under restoration succession with various grass species, we aim to determine the role of wireworms in aboveground vegetation succession. Therefore, it is crucial to know whether wireworms prefer some food plants to others. We have investigated the root preference to different grass species for Agriotes obscurus and Athous haemorrhoidalis and whether these preferences can be explained by covariates. In Experiment 1, individual wireworms could choose between four different plants, one of each species (Anthoxanthum odoratum, Festuca rubra, Holcus lanatus, and Lolium perenne). In Experiment 2, groups of wireworms were released into the soil in the center of 16 plants (4 from each species). We used multinomial logit models (MLMs) to analze the data. In the appendix the use of multinomial response models is clarified with a fictitious example, using the SAS statistic software package. No preference was found in Experiment 1. In Experiment 2 we found differences in attractiveness of plant species depending on wireworm species: A. obscurus preferred grass species from nutrient-rich grasslands (L. perenne and H. lanatus). Both wireworm species disliked F. rubra. The distance from the release point influenced the probability of being found at a certain place at the end of the experiment: wireworms tended to stay in the proximity of the release point. A. haemorrhoidalis was more often found farther from the point of release than A. obscurus. Dispersal was farther from the release point in experiments with young plants (6 weeks) compared to older ones (9 weeks). Results are discussed in a broad ecological context.     

The effects of mowing and fertilization on carbohydrate reserves and regrowth of grasses: do they promote plant coexistence in species-rich meadows?

After the cessation of regular management and after fertilization a single clonal species tends to dominate in many types of grasslands, whereas in regularly managed meadows these potential dominants usually attain a low cover. It has been hypothesized that plants reaching a high dominance in abandoned and fertilized meadows are selectively suppressed by mowing so that a balanced competition is maintained and competitive exclusion is postponed. We compared regeneration capacity and carbohydrate reserves accumulated by three species of clonal grasses, which markedly increase their dominance in irregularly mown, un-mown or fertilized meadows. Above-ground biomass and the amount of storage carbohydrates of the two largest species, (Molinia arundinacea, Calamagrostis epigejos) were reduced in a mown meadow. This effect was weaker in Bromus erectus, which produces smaller shoots. Shoots of Molinia were most impacted by mowing but their regeneration was efficient due to the large carbohydrate reserves in the shoot bases. Fertilization did not affect Bromus and Calamagrostis. In contrast, fertilized plants of Molinia produced larger storage organs and accumulated more carbohydrates. We conclude that plant size and growth form are important features promoting the ability of potential dominants to tolerate mowing and regenerate after it. Our results confirm that taller plants are selectively suppressed by this type of disturbance, thereby potentially promoting plant coexistence.     

Are ecological compensation areas attractive hunting sites for common kestrels (Falco tinnunculus) and long-eared owls (Asio otus)?

Common kestrels (Falco tinnunculus) and long-eared owls (Asio otus) in intensively farmed areas in Switzerland decreased markedly as a result of declining vole (Microtus spp.) populations. In order to counteract the loss of biodiversity in intensively farmed areas, the Swiss agri-environment scheme stipulates several types of ecological compensation areas, which together should take up 7% of the farmland. Among them are wild flower and herbaceous strips, which are not mown every year and which in summer support up to 8 times more small mammals than ordinary fields and grassland. This study investigates whether kestrels and long-eared owls preferentially hunt on ecological compensation areas and whether preferred hunting areas are related to the density of small mammals or to the density and height of the vegetation. Both kestrels and long-eared owls mainly hunted on freshly mown low-intensity meadows and artificial grassland, despite low densities of small mammals. Therefore, vegetation structure was more important for the selection of hunting sites than prey abundance. However, both predators preferred to hunt on freshly mown grassland and meadows bordering a wild flower or herbaceous strip. Voles from these strips probably invaded the adjacent freshly mown grassland and became an easy prey for kestrels and owls. In intensively farmed regions, ecological compensation areas, particularly those not mown each year, are an important refuge for small mammals, although in summer the small mammals are not directly accessible to hunting birds. Hence, a mosaic of different habitat types with grassland mown at different times of the year together with undisturbed strips is best suited to provide a year-round supply of accessible food for vole hunters.     

Plant species responses along a grazing disturbance gradient in Australian grassland

Abstract. Floristic data from paired roadside-paddock analyses from grassland in central Queensland, Australia, were ordinated. The mean direction of the vectors between these pairs was almost perfectly aligned with the indirect gradient represented by the first axis of Non-metric Multi-dimensional Scaling. It confirms anecdotal evidence of a trend from infrequently grazed roadsides to constantly grazed paddocks. The increasing abundance of annual herbs and grasses along this putative gradient is consistent with documented trends from elsewhere in the world. The response patterns of individual species along the disturbance gradient is consistent with ecological theory predicting unimodal peaks in abundance along physical environmental gradients. The ancestral perennial dominants of the grasslands, Dichanthium sericeum and D. queenslandicum, exhibited a declining response to grazing disturbance. Even the generally unpalatable perennial grass Aristida leptopoda declined considerably in the upper segments of the grazing disturbance gradient. A suite of herbaceous trailing legumes had peaks in their abundance near the middle of the grazing disturbance gradient, trends that can be readily explained by the combination of their palatability and intolerance to competition from tall perennial grasses. Several species including the noxious exotic herb Parthenium hysterophorus showed increasing abundance along the grazing disturbance gradient. The methodology may have application as a rapid method of assessing disturbance impacts elsewhere, and is most suited where a management differential between paired plots can be reliably generalized and where the physical environment is relatively monotonous.