Introduction

The nutrient relations of tropical alpine areas are poorly known despite the importance of these processes for understanding spatial and temporal variation in ecosystem productivity (Speck 1983). Nitrogen mineralization – the release of inorganic nitrogen from the substrate – is of particular importance in this respect, and has proved useful in assessing ecosystem dynamics in the European Alps (Rehder 1970, 1976a, b, 1982; Rehder & Schäfer 1978). In this chapter I address the problem of nitrogen mineralization and its impact on primary productivity in the alpine zone of Mount Kenya.

Materials and methods

Samples areas were established in the two main alpine plant communities of the Teleki Valley, on the western flank of Mount Kenya: ‘Senecio keniodendron–Lobelia telekii community’ (Area 1) on steeper slopes and ‘Lobelia keniensis– Senecio brassica community’ (Area 2) on moderate slopes and valley bottoms (see Table 12.1; also Hedberg 1964; Beck et al. 1981; Rehder 1975, 1983; Rehder et al 1981, 1988). The soil at area 1 was a loamy ‘mountain brown gley soil’ while the soil at area 2 was a blackish peaty ‘mountain wet gley soil’ (Beck et al 1981). Mean maximum temperatures were lower at the soil surface in area 2 (Table 12.2).

Nitrogen mineralization was measured with a field incubation test (Ellenberg 1964, 1977; Gerlach 1973). Volumetric soil samples were taken from three depths between 0 and 15 cm, weighed, sieved (4 mm screen), mixed and homogenized by hand.