Impact of fertilisation on phenol content and growth rate of Cladina stellaris: a test of the carbon-nutrient balance hypothesis

Abstract

Responses of concentrations of usnic (UA) and perlatolic (PA) acids and the relative growth rate (RGR) of a mat-forming lichen, Cladina stellaris, to enhanced N and P input were studied in a fertilisation experiment. It was predicted on the basis of carbon-nutrient balance (CNB) hypothesis that the concentrations of these phenolics would decline and the growth rate increase in response to increased nutrient uptake. The concentration of UA showed a convex response pattern to increased N input whereas the concentration of PA was non-responsive. An ecologically realistic, "moderate", N treatment clearly lowered the level of UA both with and without the P application. Applying P alone caused a significant increase in the level of UA. The RGR of C. stellaris did not respond to nutrient addition. The results indicate that even though the CNB hypothesis may be applicable in explaining concentrations of lichen secondary metabolites, it may be applied under a relatively narrow set of conditions. Especially inherited constraints in the growth of lichen fungi may seriously limit the responsiveness of lichens to short-time changes in the availability of resources. These limitations may also apply to other perennials adapted to nutrient-poor conditions.

The Influence of Environmental Factors on the Growth of Lichens in the Field

“…Hence, this species doubled its annual biomass after a single 20-min immersion in a phosphorus solution suggesting that phosphorus is an important stimulant to growth. Growth of the fruticose lichen Cladonia stellaris (Opiz) Brodo was studied in relation to levels of fertilisation, and growth not responding to nutrient additions suggesting that some fruticose species may not respond to short-term changes in the availability of nutrients (Hyvarinen et al 2003). In a further study of C. stellaris, Makkonen et al (2007) found that both nitrogen and phosphate could limit the growth of fruticose lichens with phosphate having a greater effect than nitrogen.…”

Effects of Modern Forest Management on Winter Grazing Resources for Reindeer in Sweden

“…Reindeer avoidance of lichens in fertilized forest stands may be caused by the presence of breakdown products of fertilizers in the ground, in the air close to the ground, or in air diffusing through the snow pack. Furthermore, nitrogen fertilization affects the amounts of the lichen compounds usnic and perlatolic acid (Hyvärinen et al 2003), and this can alter the taste of lichens and make them less palatable to reindeer. The results of fertilization trials by Å hman and Å hman (1984) have, however, shown that the concentrations of nitrate in fertilized lichens are significantly below the level that could be considered injurious to reindeer.…”

Assessment of Nitrogen deposition effects and empirical critical loads of Nitrogen for ecoregions of the United States

“…Th ey concluded that internal recycling of N improves N use effi ciency in lichens and is likely ecologically important in N-limited environments typical of the undisturbed arctic. Th ese and other studies have repeatedly shown a direct correlation between N application or N availability and concentrations of N in lichen thalli (Hahn et al 1993;Hyvärinen andCrittenden 1998a, 1998b;Hyvarinen et al 2003;Walker et al 2003;Weiss et al 2005). …”

“…Nitrogen, P, and N:P ratios infl uenced the proportion of the medullary layer volume occupied by the algal cells, the thallus volume occupied by the internal lumen, and the algal cell-wall area covered by fungal hyphae, indicating that ecologically realistic changes in the availability of key macronutrients can alter the growth of symbionts. Hyvärinen et al (2003) showed that a moderate N treatment (3 kg ha -1 against a background of 0.5 kg ha -1 wet deposition in 3 months) lowered usnic acid (C 18 H 16 O 7 ) concentrations in the star reindeer lichen with and without P application; P alone increased usnic acid, and higher N (10 kg ha -1 ) had no eff ect on usnic acid. None of the treatments increased growth rate.…”

“…Aquatic systems in arctic drainages ) and indicator species among the shrubs, grasses, lichens, and mosses appear to be responding to N deposition at low levels of ambient atmospheric or experimental N inputs. Cellular ultrastructure and pigment production are sensitive to deposition loading of ≤3 kg N ha -1 yr -1 (Hyvärinen et al 2003, Makkonen et al 2007). …”