[...]... and hence drainage of water through soil Soil aggregation and structure is of concern to the soil ecologist, not only because the activity of the soil biota strongly affects it, but also because the structure of soil determines the physical nature of the living space Aggregation determines the pore distribution of soil, which affects both the distribution of water in soil (specifically the degree to which... do sandy soils, which have larger pores that are more easily drained 1.4.4 Soil pH A large proportion of the Earth’s soils are acidic, especially in the tropics, where ecosystems persist at soil pH values of 4 or less (pH here is a measure 22 THE BIOLOGY OF SOIL of the concentration of Hϩ ions in soil water) Many northern ecosystems also have very acidic soils: the pH values of the soils of Boreal... erode the rock surface Leaching refers to the downward movement of materials in soil solution, usually from one soil horizon to another The mobility of elements depends on their solubility in water, the effect of pH on that solubility, and the rate of water percolation through the soil Podzolization involves the leaching of Al and Fe from upper soil horizons and their deposition deeper in the soil These... differently aged, but otherwise similar, geologic substrates exists Glacier Bay, on the coast of southeast Alaska, is one of the 12 THE BIOLOGY OF SOIL best known places for research on soil and ecosystem development because of the continuous retreat of the glaciers since 1794 Furthermore, records of the retreat, over some 100 km, have been maintained since this time, so the age of the glacial moraines... properties of decomposition and nutrient cycling Variation in soil properties, especially the physical matrix of the soil, also greatly influences the movement of water and associated materials both 18 THE BIOLOGY OF SOIL within and between ecosystems This section examines some of the key soil properties that most strongly influence the soil biota and their activities, and the nature of ecosystems 1.4.1 Soil. .. are central to understanding the variability in soils at the landscape level and at the level of the individual soil profile Being the central forces responsible for creating variety in soil conditions, and hence variations in the habitat of the soil biota, these factors require further consideration The biota themselves, along with vegetation, constitute one of the main soil- forming factors; both can... proportions of sand, silt, and clay), which in turn affects many soil properties, such as the ability of the soil to retain cations (its cation exchange capacity), the moisture retaining capacity, and soil profile drainage Such variation in the mineralogy of rocks, therefore, strongly influences the type of soils that are formed and the character of the vegetation that they support (Fig 1.4) Soils formed... influence the biota that dwell therein, we must first consider some of the factors that lead to variations in soils and soil properties within the landscape One of the most fascinating features of the terrestrial world is the tremendous variety in its landforms, reflecting a diversity of geological processes that have occurred 2 THE BIOLOGY OF SOIL over millions of years; more recent as factors in the variation... Glacier Bay, southeast Alaska Many glaciers in the Northern Hemisphere have been retreating during the past 200 years Glacier Bay, on the coast of southeast Alaska, is one of the best known places for research on primary succession because of the continuous retreat of the glaciers since 1794 Furthermore, records of the retreat, over some 100 km, have been kept since this time, so the age of the glacial... hence the accumulation of organic matter on the soil surface 1.3.3 Topography Variations in topography influence soil development, largely through effects on soil drainage and erosion Soil drainage is primarily affected by the position of a soil on a slope; soils at or near the top of a slope tend to be freely 10 THE BIOLOGY OF SOIL drained with a water table at some depth, whereas those at or near the . and Björn Malmqvist The Biology of Mangroves Peter F. Hogarth The Biology of Soft Shores and Estuaries Colin Little The Biology of the Deep Ocean Peter Herring The Biology of Lakes and Ponds,. habitat. The Biology of Rocky Shores Colin Little and F. A. Kitching The Biology of Polar Habitats G. E. Fogg The Biology of Lakes and Ponds Christer Brönmark and Lars-Anders Hansson The Biology of. Roy Montgomery, then deepened my interest in the land further. However, my fascination with soil biology really grew when I worked for Professor Keith Syers, the then Head of the Department of Soil Science