Changes in Organic Horizon Soil Properties Due to Reindeer Herding and Changing Management

Abstract

Mammalian herbivores can generally affect soil nutrients and nutrient cycling by their defecation and trampling (Fig. 12.1). The direct consumption of plants by herbivores normally enhances nutrient cycling, as urine and feces create an organic soil nutrient pool where nutrient release tends to be faster than nutrient release from litter (e.g., McKendrick et al. 1980; Zimov et al. 1995). Over time, increased nutrient turnover by grazing herbivores can improve soil fertility and thus support more fertile and grazing-tolerant plant species. This is true, for example, in the alpine/arctic environment where grazing and browsing can change both tall-herb and dwarf-shrub heath communities into ones of grass domination (Zimov et al. 1995; Olofsson et al. 2001). However, results from Uhlig et al. (2004) indicate that reindeer grazing decreases soil fertility of lichen-dominated mountain birch forests in Fennoscandia, and signs of soil erosion due to reindeer herding are repeatedly reported (Helle and Aspi 1983; Foster 1985; Vare et al. 1995; Evans 1996; Johansen and Karlsen 1998; Uhlig et al. 2004). Cryptogams, e.g., fruticose lichens, are important in the structure of tundra and taiga ecosystems, as exemplified by cover values, biomass, mineral content; significance for soil, thermal, and water household, and effect on other ecosystem components (Longton 1992; Chap. 11). Usnic acid and other sparingly mobile lichen compounds are, for example, suggested as contributing significantly to podzolation and profile development in alpine tundra soils (Dawson et al. 1984). Thus, fruticose lichens influence pedogenesis on mineral soils by contributing organic matter, through their impact on nutrient cycling, and by their stabilizing effect on soil temperature and moisture regimes (Rouse and Kershaw 1971; Edward and Miller 1977; Chap. 11) Furthermore, it is well recognized that trampling and grazing of lichens and plants by reindeers today are major factors controlling vegetation cover and