A Stratified Sampling Approach

Discussion in the previous section has highlighted the problems inherent in attempting to utilize previously published data to obtain global observational trends in the SOC pool at sufficient resolution to be of use in resolving major problems in global change 

Vegetated aeolian sand bodies from the last glacial maximum are common in many parts of the world, as are sandy sediments in palaeochannels and glacial deposits. Likewise, fine-textured soils derived from basalts (or intrusive equivalents) are common and 

Such an approach neglects secondary topographic effects, but these can be avoided in the sample set by restricting sampling to locations high in the local topography. The approach therefore cannot cope, for example, with local effects such as the occurrence of peats or different SOC dynamics around watercourses, but neither can any other current approach. 

Holdridge (1947) provided a simple climatic classification of vegetation in terms of rainfall and precipitation, dividing the world into 30 life zones. While this classification has been superceded by more recent work, it can serve as a guide to the number of sample regions that might be needed to cover the globe, that is, 120 locations (fine- and coarse-textured sites duplicated in each life zone). 

A consistent set of sampling depths must be applied at each site that attempt to partly separate mostly recent SOC (0-5 cm) from deeper soil layers (5-30 cm and 30-100 cm). In temperate areas, 

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