Grassland Restoration Projects Research Articles

Introduction of “the ASO grassland-restoration project”, to maintain and restore the ASO semi-natural grassland”

Introduction of “the ASO grassland-restoration project”, to maintain and restore the ASO semi-natural grassland”

Activity report of “the ASO grassland-restoration project" 2017

Activity report of “the ASO grassland-restoration project" 2017

Abandonment of croplands: problem or chance for grassland restoration? case studies from hungary

In Central‐ and Eastern Europe, the collapse of socialist regimes resulted in a transformation of state‐owned agricultural cooperatives to privately owned lands from the early 1990s onwards. These socioeconomic processes resulted in landscape‐scale changes in biodiversity, ecosystem services and agricultural production. In parallel, large‐scale abandonment of croplands, especially on sandy, salty or frequently inundated areas, became common. Abandoned croplands are usually sensitive to species invasions, and are hotspots of noxious weeds, posing threats both to agriculture and nature conservation. Grassland restoration on former croplands can be an effective strategy for suppressing these species. Thus, a common goal of nature conservation and agriculture can be the restoration of grasslands on former croplands to (1) suppress weed and/or invasive species in line with the policy “Good Farming Practices”, (2) support animal husbandry by creating meadows or pastures, and to (3) recover biodiversity and ecosystem services. In the present paper we report “best practices” of grassland restoration projects from Hungary. Our aim was to compare the effectiveness of spontaneous grassland recovery vs. active grassland restoration by seed sowing in terms of the recovery of biodiversity and ecosystem services, such as weed control and biomass production. Our results showed that grassland restoration on abandoned fields offers a viable solution for restoring biodiversity and ecosystem services. Seed sowing ensures higher weed control and biomass production, but results in lower biodiversity compared to spontaneous recovery. Both restoration methods can be cost‐effective, or even profitable even within a relatively short period of a nature conservation project.

A synthesis of the effect of grazing exclusion on carbon dynamics in grasslands in China.

Grazing exclusion (GE) is considered to be an effective approach to restore degraded grasslands and to improve their carbon (C) sequestration. However, the C dynamics and related controlling factors in grasslands with GE have not been well characterized. This synthesis examines the dynamics of soil C content and vegetation biomass with the recovery age through synthesizing results of 51 sites in grasslands in China. The results illustrate increases in soil C content and vegetation biomass with GE at most sites. Generally, both soil C content and vegetation biomass arrive at steady state after 15years of GE. In comparison, the rates of increase in above- and belowground biomass declined exponentially with the age of GE, whereas soil C content declined in a milder (linear) way, implying a lagged response of soil C to the inputs from plant biomass. Mean annual precipitation (MAP) and the rate of soil nitrogen (N) change were the main factors affecting the rate of soil C content change. MAP played a major role at the early stage, whereas the rate of soil N change was the major contributor at the middle and late stages. Our results imply that the national grassland restoration projects in China may be more beneficial for C sequestration in humid regions with high MAP. In addition, increased soil N supply to grasslands with GE at the latter recovery stage may enhance ecosystem C sequestration capacity.

Micro-topographic heterogeneity increases plant diversity in old stages of restored grasslands

It is a truism in ecology that environmental heterogeneity increases diversity. Supporting field studies are mostly concerned with a large-scale topographic heterogeneity, ranging from a couple of metres to landscape-scale gradients. To test the role of fine-scale micro-topography on plant diversity, we studied the initial vegetation of recently filled (1-year-old), and established vegetation on old (7-year-old) soil-filled channels in an alkali landscape, East-Hungary. We hypothesised that (i) recently filled channels are characterised by a high cover of ruderal species and high species diversity and (ii) high micro-topographic heterogeneity increases the diversity of species and plant strategy types (mixed C–S–R categories) in early stages but later on this effect diminishes. We found that diversity of species and plant strategy types was higher in recently filled channels compared to old filled channels. Micro-topographic heterogeneity had no effect on the studied vegetation parameters in recently filled channels. Conversely, in old filled channels higher micro-topographic heterogeneity resulted in higher diversity and lower cover of the dominant grass Festuca pseudovina. Higher micro-topographic heterogeneity resulted in increased ruderality and decreased stress-tolerance, but it did not increase the diversity of plant strategy types. In contrast with former studies, we found that a couple of centimetres of micro-topographic heterogeneity had no effect on vegetation in recently filled channels, but supported a high diversity in old filled channels. An important practical implication of our study is that in grassland restoration projects, micro-topographic heterogeneity has a crucial role in sustaining biodiversity.

Mixed evidence for the cultivar vigour hypothesis: The case of calcareous grassland forbs in a matrix of Festuca rubra

According to the cultivar vigour hypothesis, cultivars are frequently selected for traits such as increased biomass and resource capture, which may hinder the establishment of non-cultivars. Despite this concern, cultivar seed material is still used in grassland restoration. An alternative is wild plant material, which is commercially produced and used in the respective region (‘regional seed’). We established a greenhouse experiment to examine the performance of cultivar and regional forb species with and without competition from cultivar and regional dominant grass species. This was conducted in order to understand the potential effects of sowing cultivar seed in grassland restoration projects. Three calcareous grassland forb species (Buphthalmum salicifolium, Dianthus carthusianorum and Linum perenne) and one dominant grass species (Festuca rubra ssp. commutata) were selected. One forb species was sown in the centre of each pot and either zero, two or four F. rubra ssp. commutata individuals were planted around it. Above-ground biomass, plant height, leaf length, leaf width, number of leaves and stems were measured. When grown without competitors, each forb species performed differently with only L. perenne exhibiting cultivar vigour. Cultivar forbs were less negatively affected by competition with F. rubra ssp. commutata than their regional counterparts, thus supporting the cultivar vigour hypothesis. Overall, regional F. rubra ssp. commutata suppressed the above-ground biomass of the forbs species more than the cultivar F. rubra ssp. commutata, thus highlighting the potential competitiveness of regional seed. Ultimately, the goals of the restoration project will determine the source of seed material to be used in the project. Due to the complex nature of the issues involved in restoration, it should be considered that the reliance on simple guidelines in relation to the source of seed material used in grassland restoration has its limitations.

Propagation protocol for early blue violet (Viola adunca Sm. [Violaceae

Early blue violet (<i>Viola adunca</i> Sm. [Violaceae]) is the key larval host plant of threatened fritillary butterflies found along the western coast of North America. This small-statured species has not been readily available in restoration seed mixes because of the time and cost investments required for collecting seeds and the irregular flower and fruit development that occurs over the course of the growing season. We have developed an efficient method for seed production that facilitates the recovery of the butterfly taxa, and it supplies seeds for grassland restoration projects. Using greenhouse produced seedling plugs and weed barrier fabric in seed production fields allows for the increase and ease of seed collection during multiple years of seed production.

Rhinanthus minor population genetic structure and subspecies: Potential seed sources of a keystone species in grassland restoration projects

Abstract In the last few decades unimproved semi-natural grasslands have been affected by intensification of land use and habitat fragmentation. Because of their biodiversity these species-rich grasslands are of high conservation importance and efforts are under way to restore such habitats. Detailed knowledge of within species diversity will aid deciding on the optimal seed source for such restoration projects, e.g. local genotypes or ecotypes. Rhinanthus minor is a species that is typically found in semi-natural grasslands and is commonly used in grassland restoration projects. This is because R. minor is a hemiparasitic plant that takes minerals and nutrients from its host, which in turn decreases the host's biomass and leads to opportunities for less competitive species in the vegetation. Here, we investigate genetic diversity within and between R. minor populations. This allowed us to test whether the six different subspecies of R. minor that have been described in the UK, based on their morphology, flowering time, and habitat, can be differentiated using molecular markers. We identified moderate levels of genetic differentiation between R. minor populations within the UK. In addition, R. minor individuals from the UK appear to be distinct from R. minor and Rhinanthus angustifolius individuals from other European countries based on microsatellite genotyping and DNA sequencing of cpDNA and rDNA ITS. The molecular markers used in the current study did not separate populations of R. minor based on either their subspecies or habitat. The implication for the use of R. minor in grassland restoration projects seems to be that it is not necessary to use local seeds or seeds from the same subspecies.

Species introduction – a major topic in vegetation restoration

Holzel, N. (corresponding author, nhoelzel@uni-muenster.de): Institute of Landscape Ecology, University of Munster, Robert-Koch-Str. 28, 48149, Munster, Germany Buisson, E. (elise.buisson@univ-avignon.fr) & Dutoit, T. (thierry.dutoit@univ-avignon.fr): Institut Mediterraneen d’Ecologie et de Paleoecologie (UMR CNRS/IRD), IUT, Universite d’Avignon et des Pays de Vaucluse, site Agroparc BP 61207, 84 911, Avignon Cedex 09, France

Grassland restoration to conserve landscape‐level biodiversity: a synthesis of early results from a large‐scale project

AbstractQuestionEuropean landscapes have long been influenced by intensifying use by humans. Although habitat restoration can reverse this process, it is often limited in scope by socioeconomic constraints. Here we present a grassland restoration project that is exceptional in spatial scale in Europe.LocationA total area of 760 ha of arable land was restored in the Egyek‐Pusztakócs unit (50 km2) of Hortobágy National Park, east Hungary, between 2005 and 2008.MethodsRestoration targeted alkali steppes and loess grasslands by sowing seeds of either two (alkali) or three (loess) foundation grass species. In 2009, we surveyed the vegetation in restored and target grasslands and quantified the factors influencing restoration success in a space‐for‐time substitution design.ResultsWe recorded 100 species of flowering plants, of which 37 species were non‐weed, ‘target’ species. Annual weeds dominated 1‐yr‐old fields but had decreased dramatically by the third year due to a developing perennial grass cover. Former alfalfa fields had proportionally fewer weeds than former cereal and sunflower fields. The diversity of common species and the cover of target species increased from 1‐ to 4‐yr‐old restored fields. Alkali‐restored fields had more heterogeneous vegetation and more species than loess‐restored fields. Distance to the target vegetation did not directly affect vegetation variables. There was significant spatial variability in vegetation development, possibly suggesting several local pathways of succession.ConclusionsGrassland restoration was generally successful in accelerating secondary succession towards alkali steppes and loess grasslands. However, further management is necessary to counter the homogenizing effects of litter accumulation, to reduce perennial weeds and to enhance the colonization of target species. Our project provides useful practical insights into grassland restoration and in applying restoration at a number of sites within a larger area to conserve biodiversity at the landscape scale.

Effects of Four Different Restoration Treatments on the Natural Abundance of 15N Stable Isotopes in Plants

δ15N signals in plant and soil material integrate over a number of biogeochemical processes related to nitrogen (N) and therefore provide information on net effects of multiple processes on N dynamics. In general little is known in many grassland restoration projects on soil–plant N dynamics in relation to the restoration treatments. In particular, δ15N signals may be a useful tool to assess whether abiotic restoration treatments have produced the desired result. In this study we used the range of abiotic and biotic conditions provided by a restoration experiment to assess to whether the restoration treatments and/or plant functional identity and legume neighborhood affected plant δ15N signals. The restoration treatments consisted of hay transfer and topsoil removal, thus representing increasing restoration effort, from no restoration measures, through biotic manipulation to major abiotic manipulation. We measured δ15N and %N in six different plant species (two non-legumes and four legumes) across the restoration treatments. We found that restoration treatments were clearly reflected in δ15N of the non-legume species, with very depleted δ15N associated with low soil N, and our results suggest this may be linked to uptake of ammonium (rather than nitrate). The two non-legume species differed considerably in their δ15N signals, which may be related to the two species forming different kinds of mycorrhizal symbioses. Plant δ15N signals could clearly separate legumes from non-legumes, but our results did not allow for an assessment of legume neighborhood effects on non-legume δ15N signals. We discuss our results in the light of what the δ15N signals may be telling us about plant–soil N dynamics and their potential value as an indicator for N dynamics in restoration.

Does diversity influence soil nitrate, light availability and productivity in the establishment phase of Australian temperate grassland reconstruction?

Summary The successful conservation and restoration of the temperate native grasslands of south‐eastern Australia is critical to reversing the decline in range and diversity of these threatened plant communities. Yet the goals of high native species diversity and weed management are difficult to achieve in grassland restoration projects. To increase our understanding of whether synergies exist between these goals (i.e. whether early introduction of a larger number of species might improve both outcomes in the reassembly of native grassland), we examined the relationships between plant species number, functional group number and resource use during the establishment phase of direct‐sown grassland. We did this by sowing a representative suite of species (at varying levels of species number and functional group number) into experimental plots and then measuring and analysing the extent to which the newly established assemblages captured available resources, i.e. used soil nitrate, absorbed light and produced biomass (vegetative cover). Statistically significant correlations were common between the predictor variables (species number, functional group number, percentage vegetative cover, plant number, presence of idiosyncratic (dominating) species) and responses (soil nitrate concentration, light reduction or ‘extinction’). Higher diversity was associated with lower soil nitrate, while percentage vegetative cover and the presence of idiosyncratic species best predicted light extinction. The relationship between diversity, and plant biomass (measured as vegetative cover) and plant number was positive in the first year of the study. The diversity/biomass relationship became negative in the second year due to the higher numbers and cover of ‘idiosyncratic’ species. The diversity/plant number relationship also became negative in the autumn of the second year and was reduced to a trend by the winter. We found that lower nitrate and increasing plant numbers and vegetative cover were most strongly linked to increasing species number in the early stages of this study. This suggests that introducing and maintaining high diversity early in a native grassland reassembly or enhancement project will improve the resistance (e.g. to weed) of these communities. At later stages of grassland development, this function may be provided by the more dominating idiosyncratic species. The maintenance of diversity, an important goal in its own right, will therefore necessitate managed disturbances to periodically reduce the vegetative dominance of idiosyncratic species, releasing resources for the diverse range of other species whose early introduction will have allowed them to persist in the soil seed bank or as suppressed rootstocks.

Variation in the Initial Success of Seeded Native Bunchgrasses in the Rangeland Foothills of Yolo County, California

Investigations into the causes of variation in native bunchgrass distributions in California are constrained by the rarity of extant populations, their highly invaded nature, and their diverse and often unknown historical backgrounds. In addition, the correlates of success in California grassland restoration projects are rarely monitored. While controlling for seeding densities, we investigated correlates of establishment success for a mix of native bunchgrasses seeded into a non-native annual grassland with a history of agriculture and grazing in Yolo County, California. Six native grass species— blue wildrye (Elymus glaucus), big squirreltail (Elymus multisetus), Idaho fescue (Festuca idahoensis), California melicgrass (Melica californica), purple needlegrass (Nassella pulchra), and Sandberg bluegrass (Poa secunda)—were drill seeded in the fall of 1999. In order to minimize recruitment of non-native annual grass seed, the land was prepared with a spring burn and fall application of glyphosate prior to seeding. Through the third growing season, the cover of planted native grasses was significantly greater on north-facing slopes than on slopes with southern aspects. This was likely due to more mesic conditions on such sites rather than reduced competition with non-native plants. In the first growing season, distinct dense patches of filaree (Erodium botrys) became apparent. Native bunchgrasses overall, non-native grasses, and nonnative forbs all had significantly less cover inside these patches of filaree. Purple needlegrass was an exception to both of these trends, being insensitive to both aspect and filaree patches. These results reinforce the reputation of purple needlegrass as a species with wide ecological tolerance and excellent restoration potential.

Soil microbial community composition as affected by restoration practices in California grassland

Agricultural practices have strong impacts on soil microbes including both the indices related to biomass and activity as well as those related to community composition. In a grassland restoration project in California, where native perennial bunchgrasses were introduced into non-native annual grassland after a period of intensive tillage, weeding, and herbicide use to reduce the annual seed bank, microbial community composition was investigated. Three treatments were compared: annual grassland, bare soil fallow, and restored perennial grassland. Soil profiles down to 80 cm in depth were investigated in four separate layers (0–15, 15–30, 30–60, and 60–80 cm) using both phospholipid ester-linked fatty acid (PLFAs) and ergosterol as biomarkers in addition to microbial biomass C by fumigation extraction. PLFA fingerprinting showed much stronger differences between the tilled bare fallow treatment vs. grasslands, compared to fewer differences between restored perennial grassland and annual grassland. The presence or absence of plants over several years clearly distinguished microbial communities. Microbial communities in lower soil layers were little affected by management practices. Regardless of treatment, soil depth caused a strong gradient of changing habitat conditions, which was reflected in Canonical Correspondence Analysis of PLFAs. Fungal organisms were associated with the presence of plants and/or litter since the total amount and the relative proportion of fungal markers were reduced in the tilled bare fallow and in lower layers of the grassland treatments. Total PLFA and soil microbial biomass were highly correlated, and fungal PLFA biomarkers showed strong correlations to ergosterol content. In conclusion, microbial communities are resilient to the grassland restoration process, but do not reflect the change in plant species composition that occurred after planting native bunchgrasses.

Twelve Years of Herbaceous Vegetation Change in Oak Savanna Habitat on a Maryland Serpentine Barren After Virginia Pine Removal

Herbaceous vegetation monitoring results are reported for serpentine oak savanna (Quercus marilandica and Q. stellata) in Soldiers Delight Natural Environment Area and Wildlands for the period 1992–2003. Monitoring was initiated after unexpectedly finding savanna habitat during a grassland restoration project. Two small areas (each about 0.2 ha) were discovered on the east side of adjacent northwest-facing ridges, by clearing Virginia pine forest (Pinus virginiana) during the winter of 1991/1992. Permanent plot sampling of one of the areas began in 1992, and contiguous grassland vegetation was sampled for comparison. The area was included in a prescribed burn in November 1997 (post-freeze). The herbaceous layer in the savanna was depauperate at the beginning of the study; total herbaceous species cover was only 16.4%, and half of it was produced by only two species, Dichanthelium depauperatum and D. sphaerocarpon. Before the end of the study, total species cover had almost tripled to 46.2%, and little bluestem (Schizachyrium scoparium) had become the dominant species. Species richness in the savanna increased almost 50% during the period due to taxa that also occurred in the grassland with only one exception. But 14 grassland species were not sampled in the savanna, and community indices of similarity were low suggesting important habitat differences.

Effects of timing of prescribed fire on the demography of an invasive plant, spotted knapweed Centaurea maculosa

Summary Prescribed burning is a key tool used in prairie and savanna restoration projects. The timing and frequency of prescribed fires are important variables to consider because they can differentially affect the survival of individual plant species, including noxious exotic species. We used annual censuses and population matrix analysis to evaluate the demographic consequences of burning on populations of the invasive species spotted knapweed Centaurea maculosa in a Michigan, USA, prairie restoration experiment. We compared spring, summer and autumn burns at two frequencies: annually (2000–03) and in alternate years (2001, 2003). We examined the effects of different seasons and frequencies of prescribed fire on the survival, growth and reproduction of C. maculosa populations, and used life‐table response experiments and elasticity analyses to determine how season of fire affects population growth rates. We found that annual summer burning was the only treatment that significantly reduced overall population growth rates. The life‐table response experiment analysis indicated which life stages contributed the most to changes in population growth rates under the different treatments. The summer burn treatments reduced population growth by reducing reproduction. The different burn treatments altered the elasticity structure of populations, but in general reproduction of adults as well as survival of non‐reproductive adults and juveniles remained important in all treatments. This indicates that future attempts to control C. maculosa should focus on combinations of treatments targeting these life stages. Synthesis and applications. Management decisions regarding prescribed burning in grassland restoration projects should consider the responses of individual species already present in the system. In particular, it is important to consider the effects of burning on noxious invasive species that may or may not have different life histories and responses to fire compared with native species. Population matrix modelling provides a more complete picture of the effects of management on population responses compared with other measures based only on community composition and relative abundance. Depending on the goals of a restoration, non‐traditional management options, such as summer burning in mid‐west USA prairies, may be effective management tools for the control of invasive species.

Can Establishment Characteristics Explain the Poor Colonization Success of Late Successional Grassland Species on Ex‐Arable Land?

Abstract Many grassland restoration projects on former arable land face problems because early successional grassland species establish vigorously and persistently but late successional grassland species fail to establish. Differences in establishment characteristics of early and late successional species might provide an explanation for the failure of many late successional species to colonize grasslands on ex‐arable land. I examined whether early and late successional species had different establishment rates in the initial years of a grassland succession, whether a specific establishment stage (seedling emergence, mortality or growth) could be identified as the key process controlling establishment, and what management would enhance the establishment of late successional grassland species. Seeds of three early and three late successional species were sown separately in ex‐arable plots with bare soil, 1‐year‐old vegetation, and 2‐year‐old vegetation. Emergence, mortality, and seedling growth were monitored for 1 year. Early successional species established successfully in the bare soil plots but failed to establish in plots with 1‐ and 2‐year‐old vegetation. Late successional species showed either lower establishment rates in the younger succession stages or decreased establishment with succession that nevertheless resulted in significant establishment in the oldest plots. Seedling emergence proved to be the key factor determining the establishment pattern of early and late successional species. In absolute numbers, emergence of late successional species was, however, similar or higher than that of early successional species, even in the earliest succession stage. The poor establishment of late successional species on former arable land could therefore not be explained solely by differences in establishment characteristics between early and late successional grassland species. Competitive processes between early and late successional species later in the life cycle probably play an important role. The results do point out that establishment of late successional species can be promoted by creating vegetative cover from the start of the restoration effort.

Applied Historical Ecology: Using the Past to Manage for the Future

Applied historical ecology is the use of historical knowledge in the management of ecosystems. Historical perspectives increase our understanding of the dynamic nature of landscapes and provide a frame of reference for assessing modern patterns and processes. Historical records, however, are often too brief or fragmentary to be useful, or they are not obtainable for the process or structure of interest. Even where long historical time series can be assembled, selection of appropriate reference conditions may be complicated by the past influence of humans and the many potential reference conditions encompassed by nonequilibrium dynamics. These complications, however, do not lessen the value of history; rather they underscore the need for multiple, comparative histories from many locations for evaluating both cultural and natural causes of variability, as well as for characterizing the overall dynamical properties of ecosystems. Historical knowledge may not simplify the task of setting management goals and making decisions, but 20th century trends, such as increasingly severe wildfires, suggest that disregarding history can be perilous. We describe examples from our research in the southwestern United States to illustrate some of the values and limitations of applied historical ecology. Paleoecological data from packrat middens and other natural archives have been useful for defining baseline conditions of vegetation communities, determining histories and rates of species range expansions and contractions, and discriminating between natural and cultural causes of environmental change. We describe a montane grassland restoration project in northern New Mexico that was justified and guided by an historical sequence of aerial photographs showing progressive tree invasion during the 20th century. Likewise, fire scar chronologies have been widely used to justify and guide fuel reduction and natural fire reintroduction in forests. A southwestern network of fire histories illustrates the power of aggregating historical time series across spatial scales. Regional fire patterns evident in these aggregations point to the key role of interannual lags in responses of fuels and fire regimes to the El Niño–Southern Oscillation (wet/dry cycles), with important implications for long-range fire hazard forecasting. These examples of applied historical ecology emphasize that detection and explanation of historical trends and variability are essential to informed management.

APPLIED HISTORICAL ECOLOGY: USING THE PAST TO MANAGE FOR THE FUTURE

Applied historical ecology is the use of historical knowledge in the man- agement of ecosystems. Historical perspectives increase our understanding of the dynamic nature of landscapes and provide a frame of reference for assessing modern patterns and processes. Historical records, however, are often too brief or fragmentary to be useful, or they are not obtainable for the process or structure of interest. Even where long historical time series can be assembled, selection of appropriate reference conditions may be com- plicated by the past influence of humans and the many potential reference conditions encompassed by nonequilibrium dynamics. These complications, however, do not lessen the value of history; rather they underscore the need for multiple, comparative histories from many locations for evaluating both cultural and natural causes of variability, as well as for characterizing the overall dynamical properties of ecosystems. Historical knowledge may not simplify the task of setting management goals and making decisions, but 20th century trends, such as increasingly severe wildfires, suggest that disregarding history can be perilous. We describe examples from our research in the southwestern United States to illustrate some of the values and limitations of applied historical ecology. Paleoecological data from packrat middens and other natural archives have been useful for defining baseline conditions of vegetation communities, determining histories and rates of species range expansions and contractions, and discriminating between natural and cultural causes of environmental change. We describe a montane grassland restoration project in northern New Mexico that was justified and guided by an historical sequence of aerial photographs showing progressive tree invasion during the 20th century. Likewise, fire scar chronologies have been widely used to justify and guide fuel reduction and natural fire reintroduction in forests. A south- western network of fire histories illustrates the power of aggregating historical time series across spatial scales. Regional fire patterns evident in these aggregations point to the key role of interannual lags in responses of fuels and fire regimes to the El Nino-Southern Oscillation (wet/dry cycles), with important implications for long-range fire hazard fore- casting. These examples of applied historical ecology emphasize that detection and expla- nation of historical trends and variability are essential to informed management.