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Ecological Studies on the Porton Ranges: Relationships Between Vegetation, Soils and Land-Use History

T. C. E. Wells, J. Sheail, D. F. Ball and L. K. Ward
Journal of Ecology
Vol. 64, No. 2 (Jul., 1976), pp. 589-626
DOI: 10.2307/2258775
Stable URL: http://www.jstor.org/stable/2258775
Page Count: 46
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Ecological Studies on the Porton Ranges: Relationships Between Vegetation, Soils and Land-Use History
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Abstract

(1) The traditional view that most areas of present-day chalk grassland have been used as sheepwalks for many centuries has not been supported by studies of land-use history, vegetation and soils on the Porton Ranges. Documentary evidence and the plough marks visible on air photographs indicate that over 75% of the Ranges were cultivated. The results of soil studies suggest that some forms of disturbance may have been even more extensive. (2) Six well-defined chalk grassland types were distinguished, together with four scrub communities. These vegetation types are frequently separated by linear boundaries that have been created over the past 130 years. (3) A lichen-rich grassland is identified and described from chalk downlands in southern England. The close similarity, in structure and floristic composition, with certain grassland types described from the Breckland of East Anglia offers the opportunity for comparative studies of the origin of this type of grassland to be made in two physiographically different areas. (4) Studies of the history of land use and management have made possible the grouping of the grasslands into four age-classes, and groups of plants which serve as `indicator species' have been identified. (5) The soils beneath the majority of grassland-types of different ages did not differ substantially in morphology or depth but did show significant differences in soil chemistry. These differences are considered to be a result of the influence of the grassland succession, post-cultivation management, and soil faunal activity on the build-up of soil organic matter and on other soil properties, rather than being a primary cause of the observed vegetation differences. (6) Data from seventeen transects suggest an average annual rate of accretion of organic matter content over the 0-10 cm soil depth of about 0.08% dry weight. This is comparable with the rates of organic matter accumulation reported from other humose soils of high biological activity. (7) Ants affect the size-distribution of soil aggregates and particles and influence other soil characteristics. They are an important feature in the formation of tussocks in the Festuca rubra/Helictotrichon pratense/H. pubescens grasslands. The sizes of ant-mounds provide supplementary evidence for determining the age of the communities. (8) The juniper communities on the Porton Ranges are composed of even-aged stands of two age-classes, namely those dating from the late nineteenth century and since 1954 and the spread of myxomatosis. This evenness of age has been interpreted as indicating that conditions for seedling establishment in the grasslands were unfavourable at other times due to either intense grazing pressure or the presence of a closed sward with an accumulation of dead plant material. Studies of juniper and other scrub communities help to indicate the minimum age of grassland communities. (9) The value of the Porton Ranges and similar areas for inter-disciplinary research has been demonstrated. They have not been fertilized or sprayed, and have remained unploughed for at least several decades. They are in a sense museum pieces which retain maximum information content, and their value for the ecologist cannot be overstated.

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