Spatial and Seasonal Variations in Soil, Litter and Ground Vegetation in some Lake District Woodlands

Abstract

The ecologist who wishes to record the chemical and physical properties of the soil in relation to a particular problem is usually confronted with a number of queries on how and when to sample. Soil properties can vary considerably in semi-natural areas and only scanty information is available on the appropriate size, number and density of samples and time of sampling. Extrapolation from published data is difficult, since the sites are often inadequately described and sampling errors are rarely recorded, so that the design of new experiments or surveys tends to depend more on arbitrary factors and available time rather than on scientific considerations. The aim of this study was to measure at different times of the year certain properties of the ground vegetation, litter and mineral soil, in three relatively homogeneous woodlands, in order to determine the magnitude of seasonal change. A single sampling procedure was adopted, but sampling intensity was much greater than normally used, so as to assess the value of different sampling intensities for adequate description of the existing conditions. Seasonal fluctuations in the properties of soils are frequently reported, but there is considerable disagreement on the timing and magnitude of these changes (Raupach 1951; Robertson & Simpson 1954). The heterogeneity of soil is often stressed and relatively large differences in the chemical content or pH of a soil, over distances of only a few centimetres, have been demonstrated (Purvis & Davidson 1948; Ferrari & Vermeulen 1955). Piper & Prescott (1949), among others, have suggested that such variations in pH from point to point are of greater significance than the seasonal trends, but the data are inconclusive. Baker & Clapham (1939) studied annual trends in the pH of woodland soils, but spatial variations were not examined in detail. On the whole, plant and soil investigations have concentrated on agricultural soils where conditions are very different from those of natural undisturbed habitats. In this investigation, the ground vegetation, litter and mineral soil of three woodlands in the Lake District of north-west England were sampled intensively at regular intervals to record spatial and monthly fluctuations in pH, total weight, moisture content and chemical composition (Na, K, Ca, Mg, P, N, Si and ash). In each woodland, areas were chosen which appeared relatively homogeneous and yet were large enough to be representative of a forest type. The selected woodland sites were, as regards topography and vegetation, probably among the most uniform to be found in the Lake District and consisted of two stands of fairly mature oak (Quercus petraea (Mattuschka) Liebl.) on mullto moder-type humus and a plantation of larch (Larix decidua Mill.) on mor humus. It is therefore possible to compare two similar and two very different types of woodland.