Chapter 8 - 7 Nutrient Relations : Fertilization

Fertilization Effects We often learn about things in science by serendipity. And when it comes to learning about bryophytes in ecosystems, we often learn by what we do to their neighboring tracheophytes. Hence, when we fertilize our gardens or add fertilizers to restore impoverished land, the bryophytes respond along with the intended tracheophytic plants. In general, fertilizers are detrimental to bryophytes. This is often because added fertilizers benefit tracheophytes that were unable to grow well in their absence and once being fertilized are able to overgrow the slow-growing bryophytes (Virtanen 2000), depriving them of light. One effect of fertilizers is that they frequently change the pH, often making it more alkaline; this is especially true for lime fertilizers. Few bryophytes are favored by high pH levels (Figure 1), and at the very least, the species composition is likely to change (Miles 1968; Miles 1973). Moreover, lime often has a desiccating effect, like that of chalk dust on your hands. However, some specific nutrients may be limiting and certain fertilizers may actually benefit the bryophytes. Surprisingly, bryophytes in a polar semi-desert at Svalbard Arctic archipelago increased their cover as a benefit from applications of N, P, and K (with little effect by increased temperature), while there was a significant decrease in the cover of the flowering plants Dryas octopetala and Saxifraga oppositifolia (Robinson et al. 1998). A strong winter injury seemed to account for the ultimate decrease in Dryas octopetala. On the other hand, Hylocomium splendens and Rhytidium rugosum (Figure 2) exhibited significant reductions in growth in a combined temperature and fertilizer enhancement experiment in a subarctic-alpine community in Sweden (Jägerbrand et al. 2003).