The restoration and re-creation of species-rich lowland grassland on land formerly managed for intensive agriculture in the UK

I. Summary It is well known that an increase in fertility in many semi-natural communities leads to the dominance of productive species, which brings about a loss of diversity and hence also of conservation interest. Attempts to re-establish floristically rich communities on fertile sites often flounder as a result of invasion by such dominant species. This chapter reviews the relationship between nutrient supply and conservation value in both theoretical and practical terms in an attempt to provide a synthesis that would be of practical value for conservation management. From a theoretical viewpoint it is often assumed that the relationship between diversity and fertility follows a hump-back curve. This model appears to provide a reasonable broad-brush fit to empirical data in a range of situations, but exceptions occur. One area of weakness is that it takes no account of changing fertility, and two hypothetical catastrophe models are presented which illustrate the difficulties. From a practical conservation viewpoint, the three main sources of additional nutrients (successional accumulation, pollution and fertilizer) are illustrated along with a range of potential methods for measuring soil fertility and for the production of target values for different communities, above which management action is needed. The main aim of this chapter is to consider the effects of elevated soil nutrients in a systematic way. A formal model is produced which illustrates the many ways in which (1) the nutrient supply can increase and (2) the manager can manipulate the system to reduce the supply. This process stratifies management techniques into two groups: those that involve an increase in nutrient offtake, and those that involve manipulation of eco-system stores and fluxes. The complexities of conservation management aimed at reducing fertility are highlighted, and the need for studies inte-grating applied management and nutrient cycling processes is emphasized.

Soil Fertility and Nature Conservation in Europe: Theoretical Considerations and Practical Management Solutions

Grasslands used to be vital landscape elements throughout Europe. Nowadays, the area of grasslands is dramatically reduced, especially in industrial countries. Grassland restoration is widely applied to increase the naturalness of the landscape and preserve biodiversity. We reviewed the most frequently used restoration techniques (spontaneous succession, sowing seed mixtures, transfer of plant material, topsoil removal and transfer) and techniques used to improve species richness (planting, grazing and mowing) to recover natural-like grasslands from ex-arable lands. We focus on the usefulness of methods in restoring biodiversity, their practical feasibility and costs. We conclude that the success of each technique depends on the site conditions, history, availability of propagules and/or donor sites, and on the budget and time available for restoration. Spontaneous succession can be an option for restoration when no rapid result is expected, and is likely to lead to the target in areas with high availability of propagules. Sowing low-diversity seed mixtures is recommended when we aim at to create basic grassland vegetation in large areas and/or in a short time. The compilation of high-diversity seed mixtures for large sites is rather difficult and expensive; thus, it may be applied rather on smaller areas. We recommend combining the two kinds of seed sowing methods by sowing low-diversity mixtures in a large area and high-diversity mixtures in small blocks to create species-rich source patches for the spontaneous colonization of nearby areas. When proper local hay sources are available, the restoration with plant material transfer can be a fast and effective method for restoration.

Grassland restoration on former croplands in Europe: an assessment of applicability of techniques and costs

In previous studies, limited dispersal was revealed to be the main obstacle to restoration of species-rich flood- meadows along the northern Upper Rhine in Germany. To overcome dispersal limitation we transferred freshly mown plant material from species-rich sources to a restoration site on a former arable field. Before plant material application, topsoil was removed to accelerate nutrient impoverishment and create favourable conditions for seedling recruitment. Topsoil removal led to a drastic reduction in organic matter and essential mineral nutrients to the level of target communities (P) or even below (N, K). At a removal depth of 30 cm content of the soil seed bank that comprised exclusively of annual arable weeds, ruderals and some common grassland species, declined by 60 - 80%, while at a removal depth of 50 cm the seed bank was almost completely eliminated. With few exceptions, all species recorded in source plant material were found established at the restoration site. However, the overall correlation between seed content in plant material and estab- lishment success was not very high. Vegetation development at the restoration site was charac- terized by a rapid decline in arable weeds and ruderals, while resident grassland species and species transferred with plant material increased rapidly from the third year onwards. After four years as many as 102 species were established that could be exclusively attributed to plant material transfer, among them many rare and highly endangered plants. Establishment of species from plant material was most successful in regularly flooded plots, due to the suppression of competitors as well as the creation of favourable moisture conditions for seedling emergence. Diaspore transfer with plant material proved to be an extremely successful method in restoring species-rich grass- land. However, high quality of plant material and suitable site conditions with low competition in early stages of succession seem to be essential prerequisites.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1654-109X.2003.tb00573.x

Restoration of a species-rich flood meadow by topsoil removal and diaspore transfer with plant material

We investigated the influence of the exotic nitrogen-fixing black locust (Robinia pseudoacacia) on nitrogen cycling in a pitch pine (Pinus rigida) −scrub oak (Quercus ilicifolia, Q. prinoides) ecosystem. Within paired pine-oak and adjacent black locust stands that were the result of a 20-35 year-old invasion, we evaluated soil nutrient contents, soil nitrogen transformation rates, and annual litterfall biomass and nitrogen concentrations. In the A horizon, black locust soils had 1.3-3.2 times greater nitrogen concentration relative to soils within pine-oak stands. Black locust soils also had elevated levels of P and Ca, net nitrification rates and total net N-mineralization rates. Net nitrification rates were 25-120 times greater in black locust than in pine-oak stands. Elevated net N-mineralization rates in black locust stands were associated with an abundance of high nitrogen, low lignin leaf litter, with 86 kg N ha–1 yr–1 in leaf litter returned compared with 19 kg N ha–1 yr–1 in pine-oak stands. This difference resulted from a two-fold greater litterfall mass combined with increased litter nitrogen concentration in black locust stands (1.1% and 2.6% N for scrub oak and black locust litter, respectively). Thus, black locust supplements soil nitrogen pools, increases nitrogen return in litterfall, and enhances soil nitrogen mineralization rates when it invades nutrient poor, pine-oak ecosystems.

Impacts of the exotic, nitrogen-fixing black locust ( Robinia pseudoacacia ) on nitrogen-cycling in a pine–oak ecosystem

Soil acidification—the use of sulphur and acidic plant materials to acidify arable soils for the recreation of heathland and acidic grassland at Minsmere, UK

C.S.R. Snow

Papers

Soil acidification—the use of sulphur and acidic plant materials to acidify arable soils for the recreation of heathland and acidic grassland at Minsmere, UK

Trends in soil chemistry and floristics associated with the establishment of a low-input meadow system on an arable clay soil in Essex, England.

Heathland and acid grassland creation on arable soils at Minsmere: identification of potential problems and a test of cropping to impoverish soils

Restoration of Calluna heathland on a bracken Pteridium-infested site in north west England

Soil acidification and heathland establishment on former arable land