Germinable soil seed banks of anthropogenic native grasslands and grassy forest remnants in temperate south-eastern Australia

Soil seed banks of anthropogenic native grassland and grassy forest remnants on the Gippsland Plain in south-eastern Australia were studied using the seedling emergence method. Intact examples of both ecosystems are rare, owing to extensive agricultural development. Both ecosystems are assumed to have been derived since European settlement from the same original, grassy forest ecosystem. It was hypothesised that species now restricted to grassland remnants might persist in the soil seed bank of forest remnants, and vice versa. This hypothesis was not supported. In total, 25554 seedlings of at least 155 species emerged from forest and grassland seed banks collectively. Small-seeded, annual and perennial herbs were most abundant. Forest seedbanks differed substantially in composition from grassland seedbanks, and both essentially contained a subset of the species in the vegetation. Forest seedbanks contained significantly more species and individuals of annual and perennial native dicotyledons than grassland seedbanks. Seedbanks made a major contribution to local diversity, since many species in the seed bank at each quadrat were not recorded from the vegetation, but only a minor contribution to regional diversity. Species in the seedbank that were absent from all vegetation samples were recorded at few quadrats, except Juncus species, which were widespread and abundant in the seedbank. The apparent absence from forest seed banks of species that are best represented in grassland remnants (and vice versa), suggests that there is little opportunity of recruiting grassland-restricted species in forest remnants by instigating grassland management practices.     

Restoring macrophyte diversity in shallow temperate lakes: biotic versus abiotic constraints

Although many lake restoration projects have led to decreased nutrient loads and increased water transparency, the establishment or expansion of macrophytes does not immediately follow the improved abiotic conditions and it is often unclear whether vegetation with high macrophyte diversity will return. We provide an overview of the potential bottlenecks for restoration of submerged macrophyte vegetation with a high biodiversity and focus on the biotic factors, including the availability of propagules, herbivory, plant competition and the role of remnant populations. We found that the potential for restoration in many lakes is large when clear water conditions are met, even though the macrophyte community composition of the early 1900s, the start of human-induced large-scale eutrophication in Northwestern Europe, could not be restored. However, emerging charophytes and species rich vegetation are often lost due to competition with eutrophic species. Disturbances such as herbivory can limit dominance by eutrophic species and improve macrophyte diversity. We conclude that it is imperative to study the role of propagule availability more closely as well as the biotic interactions including herbivory and plant competition. After abiotic conditions are met, these will further determine macrophyte diversity and define what exactly can be restored and what not.     

Phytodiversity of temperate permanent grasslands: ecosystem services for agriculture and livestock management for diversity conservation

Plant diversity has been reported to increase productivity. Farming practices aiming at conserving or increasing plant diversity are, however, usually less profitable than conventional ones. In this review, we aim to find reasons for this discrepancy, discuss ecosystem services of grassland phytodiversity that are useful for farmers, and ways of livestock management most beneficial for diversity. Under agricultural conditions, a clear effect of species richness on a site’s primary or secondary production has not yet been demonstrated. Reasons could be that species numbers in permanent grassland are above the threshold of five species found effective in experimental plots or that the conditions are more in equilibrium with management than in weeded experimental plots. Other diversity effects on production stability, nutrient and water retention or product quality might convince farmers to increase diversity. However, these should be tested in agricultural situations, as most research has again been carried out in experimental plots. To enhance phytodiversity, grazing has been found superior over mowing, as selective grazing, treading and excreta deposition increase the heterogeneity of a sward and thus the niches available. Especially rotational grazing with intermediate intensity may be advantageous for phytodiversity. However, complex interactions between environmental conditions, sward composition, management and livestock behaviour make it difficult to forecast grazing effects. Thus, ecological and agricultural researchers should cooperate more, e.g. either in interdisciplinary projects or by hiring researchers from the respective other profession and thus diversifying research groups, in order to integrate agricultural management into biodiversity research and biodiversity measurements into agricultural research to advance our understanding of how to make conservation and enhancement of grassland phytodiversity both feasible and sustainable.     

Climate change experiments in temperate grasslands: synthesis and future directions

The immediate need to understand the complex responses of grasslands to climate change, to ensure food supplies and to mitigate future climate change through carbon sequestration, necessitate a global, synthesized approach. Numerous manipulative experiments have altered temperature or precipitation, often in conjunction with other interacting factors such as grazing, to understand potential effects of climate change on the ecological integrity of temperate grasslands and understand the mechanisms of change. Although the different ways in which temperature and precipitation may change to effect grasslands were well represented, variability in methodology limited generalizations. Results from these experiments were also largely mixed and complex; thus, a broad understanding of temperate grassland responses to these factors remains elusive. A collaboration based on a set of globally dispersed, inexpensive experiments with consistent methodology would provide the data needed to better understand responses of temperate grassland to climate change.     

Nitrogen deposition and reduction of terrestrial biodiversity: Evidence from temperate grasslands

Biodiversity is thought to be essential for ecosystem stability, function and long-term sustainability. Since nitrogen is the limiting nutrient for plant growth in many terrestrial ecosystems, reactive nitrogen has the potential to reduce the diversity of terrestrial vegetation and associated biota through favouring species adapted to quickly exploiting available nutrients. Although the potential has long been recognised, only recently has enough evidence come together to show beyond reasonable doubt that these changes are already occurring. Linked together, experimental, regional/empirical, and time-series research provide a powerful argument that enhanced deposition of reactive nitrogen across Great Britain, and potentially the rest of Europe, has resulted in a significant and ongoing decline in grassland species richness and diversity.     

Restoring grassy woodland diversity through direct seeding: Insights from six ‘best‐practice’ case studies in southern Australia

Ecological restoration of grassy woodland ecosystems is now a significant landscape‐scale conservation objective throughout southern Australia. Technological improvements in direct seeding are now sufficiently well‐advanced to examine whether cost‐effective restoration of grassy woodlands is feasible. Consideration of six ‘best practice case studies shows substantial evidence of success. Further refinement of direct seeding techniques, in combination with native seed production systems, however, will be required into the future to meet the scale of woodland conservation targets and restore ecological function.     

Fire season and intensity affect shrub recruitment in temperate sclerophyllous woodlands

The season in which a fire occurs may regulate plant seedling recruitment because of: (1) the interaction of season and intensity of fire and the temperature requirements for seed release, germination and growth; (2) post-fire rainfall and temperature patterns affecting germination; (3) the interaction of post-fire germination conditions and competition from surrounding vegetation; and (4) the interaction of post-fire germination conditions and seed predators and/or seedling herbivores. This study examined the effects of different fire intensities and fire seasons on the emergence and survival of shrubs representing a range of fire response syndromes from a summer rainfall cool climate region. Replicated experimental burns were conducted in two seasons (spring and autumn) in 2 consecutive years and fuel loads were increased to examine the effects of fire intensity (low intensity and moderate intensity). Post-fire watering treatments partitioned the effects of seasonal temperature from soil moisture. Higher intensity fires resulted in enhanced seedling emergence for hard-seeded species but rarely influenced survival. Spring fires enhanced seedling emergence across all functional groups. Reduced autumn recruitment was related to seasonal temperature inhibiting germination rather than a lack of soil moisture or competition. In Mediterranean-type climate regions, seedling emergence has been related to post-fire rainfall and exposure of seeds to seed predators. We think a similar model may operate in temperate summer rainfall regions where cold-induced dormancy over winter exposes seeds to predators for a longer time and subsequently results in recruitment failure. Our results support the theory that the effect of fire season is more predictable where there are strong seasonal patterns in climate. In this study seasonal temperature rather than rainfall appears to be more influential.     

Nitrogen deposition and reduction of terrestrial biodiversity: Evidence from temperate grasslands

Biodiversity is thought to be essential for ecosystem stability, function and long-term sustainability. Since nitrogen is the limiting nutrient for plant growth in many terrestrial ecosystems, reactive nitrogen has the potential to reduce the diversity of terrestrial vegetation and associated biota through favouring species adapted to quickly exploiting available nutrients. Although the potential has long been recognised, only recently has enough evidence come together to show beyond reasonable doubt that these changes are already occurring. Linked together, experimental, regional/e.rnpirical, and time-series research provide a powerful argument that enhanced deposition of reactive nitrogen across Great Britain, and potentially the rest of Europe, has resulted in a significant and ongoing decline in grassland species richness and diversity.     

Nitrogen deposition and reduction of terrestrial biodiversity: Evidence from temperate grasslands

Biodiversity is thought to be essential for ecosystem stability, function and long-term sustainability. Since nitrogen is the limiting nutrient for plant growth in many terrestrial ecosystems, reactive nitrogen has the potential to reduce the diversity of terrestrial vegetation and associated biota through favouring species adapted to quickly exploiting available nutrients. Although the potential has long been recognised, only recently has enough evidence come together to show beyond reasonable doubt that these changes are already occurring. Linked together, experimental, regional/empirical, and time-series research provide a powerful argument that enhanced deposition of reactive nitrogen across Great Britain, and potentially the rest of Europe, has resulted in a significant and ongoing decline in grassland species richness and diversity.     

Relationship between plant species diversity and soil microbial functional diversity along a longitudinal gradient in temperate grasslands of Hulunbeir,Inner Mongolia,China

Numerous experiments have been established to examine the effect of plant diversity on the soil microbial community. However, the relationship between plant diversity and microbial functional diversity along broad spatial gradients at a large scale is still unexplored. In this paper, we examined the relationship of plant species diversity with soil microbial biomass C, microbial catabolic activity, catabolic diversity and catabolic richness along a longitudinal gradient in temperate grasslands of Hulunbeir, Inner Mongolia, China. Preliminary detrended correspondence analysis (DCA) indicated that plant composition showed a significant separation along the axis 1, and axis 1 explained the main portion of variability in the data set. Moreover, DCA-axis 1 was significantly correlated with soil microbial biomass C (r = 0.735, P = 0.001), microbial catabolic activity (average well color development; r = 0.775, P < 0.001) and microbial functional diversity (catabolic diversity: r = 0.791, P < 0.001 and catabolic richness: r = 0.812, P < 0.001), which suggested thatsome relationship existed between plant composition and the soil microbial community along the spatial gradient at a large scale. Soil microbial biomass C, microbial catabolic activity, catabolic diversity and catabolic richness showed a significant, linear increase with greater plant species richness. However, many responses that we observed could be explained by greater aboveground plant biomass associated with higher levels of plant diversity, which suggested that plant diversity impacted the soil microbial community mainly through increases in plant production.     

Restoring our native woodlands: a case study on the RSPB reserve of Isle Martin

Summary

This paper is an account of small scale work in recreating native woodland in a highly degraded and exposed environment on the north-west coast of Scotland. The project is now beginning to spread its influence beyond Isle Martin 160 ha) on which the work has so far been mostly concentrated. The work is being done on some of the poorest, most eroded soils in the country with high exposure to salt spray. Soil rather than climate has been found to be the limiting factor. Nevertheless native willows (Salix spp.) and downy birch (Betula pubescens) have achieved 60–90 cm growth a year in appropriate sites while on better soils hazel(Corylus avellana), oak (Quercus petraea) and gean (Prunus avium) have grown 30 cm a year. On the poorest shallow peats only Scots pine (Pinus sylvestris) has established well and fertilization trials are in progress to release deciduous trees from check. The difficulty of obtaining genuine west coast native trees has led to the establishment of a tree nursery, the aims of which are as much educational as they are to ensure the use of local origin native trees.     

The macrolepidoptera of farm woodlands: determinants of diversity and community structure

The Farm Woodland Scheme, which provided incentives to convert agricultural land to timber production, contained an implicit assumption that farm woodlands produce important benefits for wildlife. The moth fauna of 18 farm woodlands in the Vale of York was surveyed between May and November 1991. The aims were twofold. The first was to determine if there were benefits for moth species diversity. The second was to ascertain whether concepts of island biogeography and the plant species richness of the woods were related to the moth species composition.Eleven families, 214 species and over 16 000 individuals of moths were recorded. Classification of the species presence/absence matrix indicated that small woods (less than 1ha) did not have characteristic woodland moth communities. Woods larger than 5ha were judged to be more valuable for the long-term conservation of woodland moth diversity. The best predictor of moth species richness was the herbaceous plant species richness within woodlands. Species richness of the family Geometridae was positively related to woodland area, as well as to woodland shape (compact shapes being preferable to elongated shapes). Characteristic woodland species are influenced by isolation (less isolated woods being richer in species). The implications of different powers of dispersal between moth families are discussed. Farm woodlands will be of more value for the conservation of the Macrolepidoptera if they are large, compact and incorporate remnants of existing woodland with extant herbaceous vegetation. These should be factors which are taken into consideration when providing incentives to establish and manage farm woodlands.     

Pasture management in semi-arid tropical woodlands: Effects on species diversity

Abstract The effects of pasture management options (sowing introduced legumes and grasses, timber treatment, applying fertilizer, cultivation before sowing, and stocking rate) on species diversity were measured at two experimental sites (Hillgrove and Cardigan) near Charters Towers, northeast Queensland. Species were divided into three groups (sown, native and exotic) and diversity was measured as species density (number of species recorded in each plot and number of species/quadrat) annually from 1982 to 1992. The responses of individual native and naturalized species to treatment were also determined. All management options affected diversity but the responses varied with site and season, and with the different measurement scales. The density of sown species either increased or was unaffected by all the management options; there were no significant decreases. The density of native species showed both positive and negative responses; it increased at high stocking rates and with tree killing at Hillgrove, and decreased with pasture sowing and cultivation. The density of exotic species increased as stocking rate was increased and decreased when pastures were sown (although not at the quadrat scale at Hillgrove). Overall the most diverse vegetation was on plots grazed at high stocking rates; at the plot scale these were native pastures but at the quadrat scale the sown pastures had more species. Among the native and naturalized species, only Portulaca spp. were more frequent on the oversown plots than the native pasture plots; 48% (Hillgrove) and 68% (Cardigan) of the species were less frequent on the oversown plots. Fertilizer application had little effect on species frequencies, while timber treatment resulted in both increases and decreases in frequency of a small number of species. The species were divided into four groups on the basis of their responses to stocking rate: a grazing-sensitive group (e.g. Themeda triandra), two grazing-tolerant groups which either slightly decreased (e.g. Chrysopogon fallax) or slightly increased (e.g. Sida spinosa) in frequency as stocking rate increased, and a fourth group of species which were frequent only at high stocking rates (e.g. Bothriochloa pertusa). There were no close relationships between herbage yield and species density.     

Long-term grazing impacts on vegetation diversity,composition, and exotic species presence across an aridity gradient in northern temperate grasslands

Little is known about the specific role of exotic species on measures of grassland plant diversity, including how this may vary with climatic conditions or large mammal herbivory. This study examined vegetation responses to long-term livestock grazing, including plant richness and diversity, as well as the contribution of exotic species to these metrics, across a network of 107 northern temperate grasslands in Alberta, Canada, spanning a broad aridity gradient. Exposure to grazing modestly increased plant richness, but did not alter Shannon’s diversity, Simpson’s diversity, or evenness, suggesting stability in floral diversity relative to grazing. However, grazing did increase grass cover while reducing shrub cover, the latter of which was only apparent in mesic grasslands. Unlike total plant diversity, exotic species richness and cover, together with exotic plant contributions to diversity, varied jointly with grazing and aridity. While long-term grazing increased exotic species, this response was most apparent in wetter areas, and non-grazed grasslands remained more resistant to the presence of exotics. Several exotic species were positive indicators of grazing in wetter grasslands, and coincided with lower native species cover, indicating grazing may be facilitating a shift from native to exotic vegetation under these conditions. Overall, our results indicate that while long-term grazing has altered the composition and cover of certain functional groups, including favoring exotics and minimizing woody vegetation in mesic areas, overall changes to plant diversity were limited. Additionally, these findings suggest that semi-arid northern temperate grasslands remain relatively resistant to grazing effects, including their susceptibility to exotic plant encroachment. These results improve our understanding of how ongoing grazing exposure may impact grassland diversity, including efforts to conserve native vegetation, as well as the important role of climate in altering fundamental grassland responses to grazing.     

Species diversity and primary productivity inMiscanthus sinensis grasslands

In an old field grassland dominated byMiscanthus sinensis Anderss. the community structures, phytomass, dominance ofM. sinensis and species diversity were measured. Species and life form composition of the stand were characterized by higher percentages of therophytes, woody and shrubby species, liana and alien species. From May so September in 1982, all the aboveground parts were harvested from each of the four quadrats (2 m×2 m) once a month. Seasonal peak of aboveground phytomass, in September, was 1027 g d.w.m⁻² to whichM. sinensis contributed as much as 96.5%. With the progress of the growing season,M. sinensis became increasingly important both in stand phytomass and in dominance, whereas species diversity based on the dry weight contributions of constituent species decreased. Our analysis of these seasonal trends showed that the diversity was largely a function of dominance of the most important species, rather than that of stand phytomass or productivity. The simultaneous measurements of 20 quadrats in late August 1983, also supported the above conclusion.     

Hidden diversity and productivity patterns in mixed Mediterranean grasslands

A detailed study of the variation in productivity across a diversity gradient in an experimental Mediterranean grassland examines the effects of a dominant perennial grass species upon the overall diversity–productivity relationship. The experiment took place at the Greek site of the European-wide BIODEPTH programme. The experimental design is characterized by the use of a number of communities containing annuals and perennials within the total set of manipulated plots. The main results are: 1) a log-linear relationship between diversity and productivity exists in Mediterranean grasslands synthesized by annuals only, 2) in mixed communities where multiple growth forms coexist, the performance of a dominant or keystone species may reverse or hide the diversity–productivity pattern of a functional or growth form group of species taken separately, and 3) the introduction of the dominant grass in the low-diversity mixtures creates an 'inverted' sampling effect which can produce as an artefact a constant productivity response across the diversity gradient.