Habitat use and movement patterns by dependent and independent juvenile Grasshopper Sparrows during the post‐fledging period

The post‐fledging period is a critical life stage for young grassland birds. Habitat selection by recently fledged birds may differ from that of adults and may change as juveniles transition from the care and protection of parents to independence. To describe patterns of habitat selection during these important life stages, we studied habitat use by juvenile Grasshopper Sparrows (Ammodramus savannarum) in a Conservation Reserve Program grassland in Maryland. We used radio‐telemetry to track daily movement patterns of two age classes of Grasshopper Sparrows during the post‐fledging period. Sparrows were classified as either dependent (<32‐d‐old) or independent (≥32‐d‐old). We characterized the vegetation at 780 vegetation plots (390 plots where birds were located and 390 paired random plots). Microhabitats where dependent birds were found had significantly more bare ground, litter, and plant species richness than paired random plots. In addition, dependent birds were found in plots with less bare ground, more warm‐season grass cover, more total vegetation cover, and more forb cover than plots used by independent birds. Plots where independent birds were located also had significantly more bare ground than random plots. Dependent birds are less able to escape from predators because their flight feathers are not fully grown so they may benefit from remaining in areas of greater vegetation cover. However, juveniles transitioning from dependence to independence must forage on their own, possibly explaining their increased use of more open areas where foraging may be easier. To properly manage habitat for grassland birds, management strategies must consider the changing needs of birds during different stages of development. Our results highlight the importance of diverse grassland ecosystems for juvenile grassland birds during the transition to independence.     

Patterns of Richness and Abundance in a Tropical African Leaf‐litter Herpetofauna1

I compared species richness and habitat correlates of leaf‐litter herpetofaunal abundance in undisturbed and selectively logged forests, and an abandoned pine plantation in Kibale National Park, Uganda. I sampled 50 randomly located 25 m² litter plots in each area during the wet and dry seasons in 1997. Ten anuran, five lizard, and three snake species were captured in plots over the study. Assemblage composition was most similar at logged and unlogged sites. The logged forest herpetofauna had higher species richness and abundance than the unlogged forest, but diversity was greater in the unlogged forest due to greater evenness. In contrast, the pine plantation site had the highest richness, abundance, and evenness of the three study sites, but species composition was distinct from the other areas. Herpetofaunal densities were significantly lower in all three areas during the dry season than in the wet season. During the dry season, soil moisture, litter mass, topography, shrub cover, and number of fallen logs were significant positive predictors of herpetofaunal presence in litter plots, but only soil moisture was significant in the wet season. The interaction of moisture and topography appears to be important in determining seasonal patterns of litter herpetofaunal distribution. Comparison of litter herpetofaunal studies across the tropics have shown that mid‐elevation faunas generally support fewer species than lowland faunas. Compared with other tropical mid‐elevation litter faunas, Kibale supports an intermediate number of species, but at lower densities than observed at any other mid‐elevation site reported in the literature.     

Effects of the expansion by Hippophaë rhamnoides on plant species richness in coastal dunes

Question: Is the expansion of Hippophaë rhamnoides in coastal dunes associated with a decline in plant species richness, and is this decline best described by a hump‐backed relationship between species number and shrub cover? Location: Grey and yellow dunes on the East Frisian islands Spiekeroog and Norderney. Methods: Total plant species richness as well as the number of herbaceous and cryptogam species were determined in 2001 using plots of 16 m² size. We compared shrubland plots with varying cover of Hippophaë with neighbouring dune grassland plots without shrubs as reference sites. Soil samples were collected to determine the values of some important edaphic variables (pH, organic matter, nitrogen). Results: The shrubland plots with Hippophaë had or tended to have lower soil pH and C/N ratios and higher contents of organic matter and nitrogen than the grassland plots. Total species richness was marginally significantly related to the cover of Hippophaë in a hump‐backed manner on both islands. The pattern was more pronounced for mosses and lichens than for herbaceous species. For all species groups on Spiekeroog and for the herbaceous species on Norderney, the hump‐backed relationship was much improved when using the difference in species number between shrubland and grassland plot as a dependent variable. Relationships could be improved by including the soil parameters as co‐variables. Species richness was highest at moderate levels of shrub expansion, while it was much reduced in very dense shrubland. The decrease in species number is caused by the decline in grassland species typical of the open dunes, including some rare taxa. Conclusions: The expansion of Hippophaë rhamnoides is a serious threat to the plant species richness of open coastal dunes, and needs to be counteracted by management measures.     

Dominant Grasses Suppress Local Diversity in Restored Tallgrass Prairie

Warm‐season (C₄) grasses commonly dominate tallgrass prairie restorations, often at the expense of subordinate grasses and forbs that contribute most to diversity in this ecosystem. To assess whether the cover and abundance of dominant grass species constrain plant diversity, we removed 0, 50, or 100% of tillers of two dominant species (Andropogon gerardii or Panicum virgatum) in a 7‐year‐old prairie restoration. Removing 100% of the most abundant species, A. gerardii, significantly increased light availability, forb productivity, forb cover, species richness, species evenness, and species diversity. Removal of a less abundant but very common species, P. virgatum, did not significantly affect resource availability or the local plant community. We observed no effect of removal treatments on critical belowground resources, including inorganic soil N or soil moisture. Species richness was inversely correlated with total grass productivity and percent grass cover and positively correlated with light availability at the soil surface. These relationships suggest that differential species richness among removal treatments resulted from treatment induced differences in aboveground resources rather than the belowground resources. Selective removal of the dominant species A. gerardii provided an opportunity for seeded forb species to become established leading to an increase in species richness and diversity. Therefore, management practices that target reductions in cover or biomass of the dominant species may enhance diversity in established and grass‐dominated mesic grassland restorations.     

Size of the local species pool determines invasibility of a C4-dominated grassland

The size of the local species pool (i.e., species surrounding a community capable of dispersal into that community) and other dispersal limitations strongly influence native plant community composition. However, the role that the local species pool plays in determining the invasibility of communities by exotic plants remains to be evaluated. We hypothesized that the richness and abundance of exotic species would be greater in C4‐dominated grassland communities if the local species pool included a larger proportion of exotic species. We also predicted that an increase in the exotic species pool would increase the invasibility of sites thought to be resistant to invasion (annually burned grassland). To test these hypotheses, study plots were established within two long‐term (>20 yr) fire experiments at a tallgrass prairie preserve in NE Kansas (USA). Study plots were surrounded by either a small pool of exotic species (small species pool (SSP) plots; six species) or a larger exotic species pool (large species pool (LSP) plots; 18 species). We found that richness and absolute cover of exotic species was significantly (P<0.001) lower (～70 and 90%, respectively) in annually burned compared to unburned plots, regardless of the size of the exotic species pool. As predicted, exotic species richness was higher (P<0.001) for LSP plots (3.9 per 250 m2) than for SSP plots (0.7 per 250 m2); however, absolute cover was unaffected by the size of the exotic species pool. In the absence of fire, plots with a LSP had four times as many exotic species than SSP plots. An increase in the local exotic species pool also increased the invasibility of annually burned grassland. Indeed, richness of exotic plant species in annually burned LSP plots did not differ from unburned plots with a SSP, indicating that a larger pool of exotic species countered the negative effects of fire. These findings have important implications for predicting how the invasion of plant communities may respond to human‐induced global changes, such as habitat fragmentation. Community characteristics or factors such as frequent fires in grasslands may impart resistance to invasions by exotic species in large, intact ecosystems. However, when a large pool of exotic species is present, frequent fire may not be sufficient to limit the invasions of exotic plants in fragmented landscapes.     

Management impacts on vegetation dynamics of hyper‐eutrophicated fields at Berlin,Germany

Abstract. This paper reports on vegetation dynamics on terrestrial, temperate grassland sites at the upper range of the productivity scale, i.e. on abandoned sewage fields (fields once used for waste water disposal) at Berlin‐Blankenfelde, Germany. I studied regeneration and the influence of different management practices (removal of top soil and mowing in late summer). Changes in species composition and cover were followed on permanent plots of 2m × 2m size through five years of vegetation development. At the outset of the experiment the abandoned fields were dominated by dense Urtica dioica /Elymus repens stands. Species richness was 7 species/ 4m², and it remained low on unmanaged plots during the time of observation (7.6 species/plot in year 5). Removal of 20 cm of top soil caused a severe decline of Urtica and a large increase in species richness (21 species in year 1 after disturbance). Mowing was slightly higher compared with unmown plots on both initially excavated and unexcavated plots. Total cover was always near 100 % (except immediately after top soil removal). Colonization of bare soil was very rapid and in late summer of the first year after disturbance cover already increased towards 100%. On all plots the vegetation was mostly dominated by perennial herbs and grasses. Winter season gaps are occupied by Galium aparine, a large‐seeded annual scrambling climber. Monocarpic perennials behaved as winter annuals in most cases. Woody species were inhibited by dense above‐ground biomass and litter cover. The paper questions whether succession on abandoned sewage fields may proceed towards a woodland stage and advises how vegetation of such hyper‐eutrophicated sites can be managed towards higher diversity.     

Managing open habitats by wild ungulate browsing and grazing: A case‐study in North‐Eastern Germany

Question: Can wild ungulates efficiently maintain and restore open habitats? Location: Brandenburg, NE Germany. Methods: The effect of wild ungulate grazing and browsing was studied in three successional stages: (1) Corynephorus canescens‐dominated grassland; (2) ruderal tall forb vegetation dominated by Tanacetum vulgare; and (3) Pinus sylvestris‐pioneer forest. The study was conducted over 3 yr. In each successional stage, six paired 4 m²‐monitoring plots of permanently grazed versus ungrazed plots were arranged in three random blocks. Removal of grazing was introduced de novo for the study. In each plot, percentage cover of each plant and lichen species and total cover of woody plants was recorded. Results: Wild ungulates considerably affected successional pathways and species composition in open habitats but this influence became evident in alteration of abundances of only a few species. Grazing effects differed considerably between successional stages: species richness was higher in grazed versus ungrazed ruderal and pioneer forest plots, but not in the Corynephorus sites. Herbivory affected woody plant cover only in the Pioneer forest sites. Although the study period was too short to observe drastic changes in species richness and woody plant cover, notable changes in species composition were still detected in all successional stages. Conclusion: Wild ungulate browsing is a useful tool to inhibit encroachment of woody vegetation and to conserve a species‐rich, open landscape.     

Use of sheep grazing in the restoration of semi‐natural meadows in northern Finland

Abstract. The biodiversity of species‐rich semi‐natural meadows is declining across Europe due to ceased management. In this study we aimed to find out how successfully the local species richness of an overgrown semi‐natural mesic meadow could be restored by sheep grazing after a long period of abandonment. The cover of vascular plant species in grazed plots and ungrazed exclosures was studied for five years and the responses of different functional plant groups were followed (herbs vs grasses, tall vs short species, species differing in flowering time, species representing different Grime's CSR strategies and species indicative of rich vs poor soil). Grazing increased species number by nearly 30%. On grazed plots the litter cover practically disappeared, favouring small herbs such as Rhinanthus minor, Ranunculus acris, Trifolium pratense and the grass Agrostis capillaris. Grazing decreased the cover of the late flowering tall herb Epilobium angustifolium but had no effect on the abundance of the early flowering tall herbs Anthriscus sylvestris or Geranium sylvaticum. We suggest that to succeed in restoration it is useful to determine the responses of different functional plant groups to grazing. Grassland managers need this information to optimize the methods and timing of management used in restoration. Additional management practices, such as mowing, may be needed in mesic meadows to decrease the dominance of tall species. The availability of propagules seemed to restrict further increase of species richness in our study area.     

Direct and indirect effects of land‐use intensification on ant communities in temperate grasslands

Land‐use intensification is a major driver of local species extinction and homogenization. Temperate grasslands, managed at low intensities over centuries harbored a high species diversity, which is increasingly threatened by the management intensification over the last decades. This includes key taxa like ants. However, the underlying mechanisms leading to a decrease in ant abundance and species richness as well as changes in functional community composition are not well understood. We sampled ants on 110 grassland plots in three regions in Germany. The sampled grasslands are used as meadows or pastures, being mown, grazed or fertilized at different intensities. We analyzed the effect of the different aspects of land use on ant species richness, functional trait spaces, and community composition by using a multimodel inference approach and structural equation models. Overall, we found 31 ant species belonging to 8 genera, mostly open habitat specialists. Ant species richness, functional trait space of communities, and abundance of nests decreased with increasing land‐use intensity. The land‐use practice most harmful to ants was mowing, followed by heavy grazing by cattle. Fertilization did not strongly affect ant species richness. Grazing by sheep increased the ant species richness. The effect of mowing differed between species and was strongly negative for Formica species while Myrmica and common Lasius species were less affected. Rare species occurred mainly in plots managed at low intensity. Our results show that mowing less often or later in the season would retain a higher ant species richness—similarly to most other grassland taxa. The transformation from (sheep) pastures to intensively managed meadows and especially mowing directly affects ants via the destruction of nests and indirectly via loss of grassland heterogeneity (reduced plant species richness) and increased soil moisture by shading of fast‐growing plant species.     

The role of litter in an old-field community: impact of litter quantity in different seasons on plant species richness and abundance

Summary We studied the effect of removing and adding plant litter in different seasons on biomass, density, and species richness in a Solidago dominated old-field community in New Jersey, USA. We removed all the naturally accumulated plant litter in November (658 g/m²) and in May (856 g/m²) and doubled the amount of litter in November and May in replicated plots (1 m²). An equal number of plots were left as controls. Litter removal and addition had little impact on total plant biomass or individual species biomass in the growing season following the manipulations. Litter removal, however, significantly increased plant densities but this varied depending upon the season of litter removal, species, and life history type. Specifically, the fall litter removal had a much greater impact than the spring litter removal suggesting that litter has its greatest impact after plant senescence in the fall and prior to major periods of early plant growth in spring. Annual species showed the greatest response, especially early in the growing season. Both spring and fall litter removal significantly increased species richness throughout the study. Litter additions in both spring and fall reduced both plant densities and species richness in June, but these differences disappeared near the end of the growing season in September. We concluded than in productive communities where litter accumulation may be substantial, litter may promote low species richness and plant density. This explanation does not invoke resource competition for the decline in species richness. Finally, we hypothesize that there may be broad thresholds of litter accumulation in different community types that may act to either increase or decrease plant yield and diversity.     

Disproportionate effects of non‐colonial small herbivores on structure and diversity of grassland dominated by large herbivores

The response of semiarid grasslands to small, non‐colonial herbivores has received little attention, focusing primarily on the effects of granivore assemblages on annual plant communities. We studied the long‐term effects of both small and large herbivores on vegetation structure and species diversity of shortgrass steppe, a perennial semiarid grassland considered marginal habitat for small mammalian herbivores. We hypothesized that 1) large generalist herbivores would affect more abundant species and proportions of litter‐bare ground‐vegetation cover through non‐selective herbivory, 2) small herbivores would affect less common species through selective but limited consumption, and 3) herbivore effects on plant richness would increase with increasing aboveground net primary production (ANPP). Plant community composition was assessed over a 14‐year period in pastures grazed at moderate intensities by cattle and in exclosures for large (cattle) and large‐plus‐small herbivores (additional exclusion of rabbits and rodents). Exclusion of large herbivores affected litter and bare ground and basal cover of abundant, common and uncommon species. Additional exclusion of small herbivores did not affect uncommon components of the plant community, but had indirect effects on abundant species, decreased the cover of the dominant grass Bouteloua gracilis and total vegetation, and increased litter and species diversity. There was no relationship between ANPP and the intensity of effects of either herbivore body size on richness. Exclusion of herbivores of both body sizes had complementary and additive effects which promoted changes in vegetation composition and physiognomy that were linked to increased abundance of tall and decreased abundance of short species. Our findings show that small mammalian herbivores had disproportionately large effects on plant communities relative to their small consumption of biomass. Even in small‐seeded perennial grasslands with a long history of intensive grazing by large herbivores, non‐colonial small mammalian herbivores should be recognized as an important driver of grassland structure and diversity.     

The Relation Between Unpalatable Species, Nutrients and Plant Species Richness in Swiss Montane Pastures

In agriculturally marginal areas, the control of unpalatable weeds on species rich pastures may become problematic due to agricultural and socio-economic developments. It is unclear how increased dominance of unpalatable species would affect the botanical diversity of these grasslands. We investigated whether there was any relationship between plant species diversity and the abundance of unpalatable species and whether soil conditions affected this relationship. In three species-rich montane pastures in western Switzerland, we related plant species richness to soil attributes, the relative cover of all unpalatable species and the relative cover of the locally dominant, toxic Veratrum album in 25 plots of 4 m². We furthermore determined species richness in small transects through patches of V. album. Species richness was significantly lower in and near (≤ 0.3 m) patches of V. album. At the field scale, plant species richness was best described by total soil N:P ratio (positive relation) in one site and the relative abundance of unpalatable species (negative relation) and soil N:P ratio (positive relation) in a second site. In the third site, species richness was not significantly related to any measured variable. Vegetation diversity (Simpson's D) was negatively related to the relative abundance of unpalatable species in one site and positively related to pH in another site. The results suggest that no single factor can explain plant species richness and diversity in montane pastures. At very high densities unpalatable species can have adverse effects but soil nutrient status appears to be a more general determinant of plant species richness. Conservation efforts should give priority to the prevention of intensification of these pastures.     

Long‐term phosphite application maintains species assemblages,richness and structure of plant communities invaded by Phytophthora cinnamomi

The impact of the plant pathogen Phytophthora cinnamomi and the fungicide phosphite on species assemblages, richness, abundance and vegetation structure was quantified at three sites in Kwongkan communities in the Southwest Australian Floristic Region. Healthy and diseased vegetation treated with phosphite over 7–16 years was compared with non‐treated healthy and diseased vegetation. After site differences, disease had the greatest effect on species assemblages, species richness and richness within families. Disease significantly reduced cover in the upper and lower shrub layers and increased sedge and bare ground cover. Seventeen of 21 species assessed from the families Ericaceae, Fabaceae, Myrtaceae and Proteaceae were significantly less abundant in non‐treated diseased vegetation. In diseased habitats, phosphite treatment significantly reduced the loss of shrub cover and reduced bare ground and sedge cover. In multivariate analysis of species assemblages, phosphite‐treated diseased plots grouped more closely with healthy plots. Seven of 17 susceptible species were significantly more abundant in phosphite‐treated diseased plots compared with diseased non‐treated plots. The abundance of seven of 10 Phytophthora‐susceptible species was significantly higher along transects in phosphite‐treated vegetation. Comparison of the floristics of healthy non‐treated with healthy‐treated plots showed no significant differences in species assemblages. Of 21 species assessed, three increased in abundance and only one decreased significantly in phosphite‐treated healthy plots. In three Kwongkan communities of the SWAFR, P. cinnamomi had a profound impact on species assemblages, richness, abundance and vegetation structure. There was no evidence of adverse effects of phosphite treatment on phosphorus‐sensitive species, even after fire. Treatment with phosphite enhanced the survival of key susceptible species and mitigated disease‐mediated changes in vegetation structure. In the absence of alternative methods of control in native communities, phosphite will continue to play an important role in the protection of high priority species and communities at risk of extinction due to P. cinnamomi.     

Effects of fire on the vegetation of a lowland heathland in North-western Italy

This study focuses on the effect of fire on lowland heathlands at the extreme southern edge of their European distribution (Vauda Nature Reserve, NW Italy). Forty-nine plots (50 m radius) were surveyed between 1999 and 2006. Each year, fire occurrences were recorded and per cent cover of four vegetation types (grassland, heath, low shrubland, and tall shrubland) was estimated in each plot. Vascular plant species richness was also recorded in 255, 1 m² quadrats. After a fire, grassland vegetation expanded, but then declined rapidly as heath and shrubland recovered: 7 years after a fire, tall shrubland encroached on to more than 40% of the plots, and grassland declined from 50% to 20% cover. Between 1999 and 2006, Betula pendula shrubland greatly expanded, while grassland decreased over most of the Reserve, even where fire frequency was high. Tall shrubland had low plant diversity and was dominated by widespread species of lower conservation value. By contrast, early successional vegetation (grassland and low shrubland) had higher richness and more narrowly distributed species, indication that the development of tall shrubland causes significant species loss in the heathland. Italian lowland heathlands are characterized by high rates of shrubland encroachment that threatens both habitat and species diversity. Burning frequencies of once in 3–6 years seem appropriate in this habitat, but burning alone might not suffice without actions to increase herbivore grazing.     

Effects of fire on the structure and diversity of a Spartina argentinensis tall grassland

Question: What are the effects of fire on the structure and the diversity of a Spartina ar gentinensis tall grassland in the short and medium run. S. argentinensis is the dominant species of tall grasslands on inland marshes of the Chaco‐Pampean region (Argentina), where spontaneous or man‐made fires are very frequent. Location: Federico Wildermuth Reserve (31°57′S; 61°23′W), Province of Santa Fe, Argentina, an area never ploughed that supported cattle until its exclusion in 1988. Methods: Vegetation was surveyed in randomly placed permanent plots using the Braun‐Blanquet cover‐abundance scale. The data were analysed by multivariate methods (PCA and MRPP) for synthesizing information and testing hypotheses. Results: Fire did not have a long‐lasting effect on the tall grassland. There was only a temporarily reduction of cover‐abundance of S. argentinensis which allowed an increase in the number of accompanying species such as Heliotropium curassavicum, Pluchea sagittalis, and Verbena litoralis and of some naturalised or weed species, such as Melilotus alba and Cirsium vulgare, respectively. Fire increased diversity, which remained relatively high for two to three years. Three years after the fire there were no significant differences on the amount of litter accumulated on burned and unburned plots. Conclusion: Fire should be considered an intrinsic part of the dynamics of S. argentinensis tall grassland.     

Effects of the litter layer of Pteridium aquilinum on seed banks under experimental restoration

Questions: Does the litter layer of Pteridium aquilinum (bracken) act as a barrier to certain species in the seed bank? Does bracken control/restoration treatment affect seed transfer through the litter layer? Location: Five experiments at three sites across the UK covering two major vegetation types; acid‐grassland and heath‐land. Methods: At each experiment a range of bracken control and vegetation restoration treatments were applied for about ten years. The seed bank was sampled in both the bracken litter and the soil. The cover (%) of each species in the vegetation and the bracken litter abundance (cover and depth) was also estimated. Results: The bracken litter layer acts as an inert barrier as it contained a large proportion of seeds available in the litter‐soil profile (38%– 67% of the total). Bracken litter depth and cover also influenced significantly the seed bank composition in both the bracken litter and the soil. These effects were site‐specific, and species‐specific. The application of treatments changed significantly the balance between seed inputs and outputs in the bracken litter layer for some species. This was either a positive or negative response relative to the untreated control plots. Conclusion: For heathland and acid‐grassland restoration, the bracken litter layer may be an important seed source, but it must be disturbed particularly before seed addition.     

Ecological parameters of the leaf‐litter frog community of an Atlantic Rainforest area at Ilha Grande,Rio de Janeiro state,Brazil

Abstract The Atlantic Rainforest originally covered much of the Brazilian coast and is now reduced to approximately only 7% of its original area. Data on abundance distribution and microhabitat characteristics of anuran amphibians living on the forest floor leaf litter in the Atlantic Rainforest are scarce. In this study, we analysed the effect of litter depth and structure on the abundance and species richness of leaf‐litter frogs in an area of Atlantic Rainforest at Ilha Grande, Rio de Janeiro State, south‐eastern Brazil. We performed monthly samples (nocturnal and diurnal) from August 1996 to October 1997 using small (2 m × 1 m) plots. We sampled 234 plots, totalling 468 m² of forest leaf litter. We estimated leaf‐litter depth and the proportion of leaves in the plot and tested their effect on the total abundance of frogs and species richness using multiple regression analysis. We found 185 frogs from eight species: Brachycephalus (=Psyllophryne) didactylus (Izecksohn, 1971) (Brachycephalidae), Dendrophryniscus brevipollicatus Jiménez de la Espada 1871 (Bufonidae), Adenomera marmorata Steindachner 1867, Eleutherodactylus parvus (Girard 1853), Eleutherodactylus guentheri (Steindachner 1864), Eleutherodactylus binotatus (Spix 1824) and Zachaenus parvulus (Girard 1853) (Leptodactylidae), and Chiasmocleis sp. (Microhylidae). Brachycephalus didactylus was the most abundant species, with 91 individuals, whereas Dendrophryniscus brevipollicatus was the rarest, with two individuals. Mean litter depth and the proportion of leaves in the leaf litter were significantly related to frog abundance (R² = 0.17; F_2,107 = 10.779; P = 0.0001) and species richness (R² = 0.11; F_2,107 = 6.375; P = 0.002) indicating that microhabitat characteristics may affect local distribution and abundance of frogs in the forest floor.     

Population size and fire intensity determine post‐fire abundance in grassland lichens

Questions: What is the variability in abundance of lichens on grassland soil between and within fields after prescribed fire? Is post‐fire lichen abundance an effect of pre‐fire population size? Location: Cedar Creek Natural History Area, Minnesota, USA. Methods: Lichen abundance, estimated as ground cover and dominated by Cladonia spp., was mapped in plots in two fields before prescribed burning on 06.10.2003 and 15.10.2003 for the first time since abandonment in the 1950s. The plots were resurveyed one year post‐fire. Results: Post‐fire cover of Cladonia spp. varied strongly between the fields, most likely due to different weather conditions between the burn events, which resulted in different fire intensities, one of low and one of high intensity. In the field that experienced the low intensity fire, post‐fire cover of Cladonia spp. was still relatively high, and showed a positive relationship with pre‐fire cover, while no such relationship was found after the high intensity fire. In that field Cladonia spp. experienced high mortality rates irrespective of pre‐fire cover. Conclusions: This study provides an example of how species response to disturbance can be a function of population size, but that this relationship can be non‐linear; lichens in grassland can survive a low intensity fire proportionally to pre‐fire population size, but experience high mortality rates above a fire intensity threshold. The applications of these results are that fire intensity matters to species response to prescribed fire, and that the persistence of climax lichen communities and biodiversity in the study system needs a broad range of fire intervals.     

Inferring relationships between native plant diversity and Lonicera japonica in upland forests in north Mississippi,USA

Question: Do anthropogenic disturbances interact with local environmental factors to increase the abundance and frequency of invasive species, which in turn exerts a negative effect on native biodiversity? Location: Mature Quercus‐Carya and Quercus‐Carya‐Pinus (oak‐hickory‐pine) forests in north Mississippi, USA. Methods: We used partial correlation and factor analysis to investigate relationships between native ground cover plant species richness and composition, percent cover of Lonicera japonica, and local and landscape‐level environmental variables and disturbance patterns in mature upland forests. We directly measured vegetation and environmental variables within 34 sampling subplots and quantified the amount of tree cover surrounding our plots using digital color aerial photography. Results: Simple bivariate correlations revealed that high species richness and a high proportion of herbs were associated with low Lonicera japonica cover, moist and sandy uncompacted soils, low disturbance in the surrounding landscape, and periodic prescribed burning. Partial correlations and factor analysis showed that once we accounted for the environmental factors, L japonica cover was the least important predictor of composition and among the least important predictors of species richness. Hence, much of the negative correlation between native species diversity and this invasive species was explained by soil texture and local and landscape‐level land‐use practices. Conclusions: We conclude that negative correlations between the abundance of invasive species and native plant diversity can occur in landscapes with a gradient of human disturbance, regardless of whether there is any negative effect of invasive species on native species.     

Mowing Reduces Exotic Annual Grasses but Increases Exotic Forbs in a Semiarid Grassland

Cheatgrass (Bromus tectorum) and other exotic winter‐active plants can be persistent invaders in native grasslands, growing earlier in the spring than native plants and pre‐empting soil resources. Effective management strategies are needed to reduce their abundance while encouraging the reestablishment of desirable native plants. In this 4‐year study, we investigated whether mowing and seeding with native perennial grasses could limit growth of exotic winter‐actives, and benefit growth of native plants in an invaded grassland in Colorado, United States. We established a split‐plot experiment in October 2008 with 3 mowing treatments: control, spring‐mowed, and spring/summer‐mowed (late spring, mid‐summer, and late summer), and 3 within‐plot seeding treatments: control, added B. tectorum seeds, and added native grass seeds. Cover of plant species and aboveground biomass were measured for 3 years. In March and June of 2010, 2011, and March of 2012, B. tectorum and other winter‐annual grasses were half as abundant in both mowing treatments as in control plots; however, cover of non‐native winter‐active forbs increased 2‐fold in spring‐mowed plots and almost 3‐fold in spring/summer‐mowed plots relative to controls. These patterns remained consistent 1 year after termination of treatments. Native cool‐season grasses were most abundant in spring‐mowed plots, and least abundant in control plots. There was higher cover of native warm‐season grasses in spring/summer‐mowed plots than in control plots in July 2011 and 2012. The timing of management can have strong effects on plant community dynamics in grasslands, and this experiment indicates that adaptive management can target the temporal niche of undesirable invasive species.