Linking Restoration and Ecological Succession (Springer ... - Inecol

Chapter 3 Aboveground–Belowground Linkages, Ecosystem Development, and Ecosystem Restoration 55
Figure 3.3 A forested island in Lake Hornavan in northern Sweden.
this is a marked reduction in both plant standing biomass and NPP (Wardle
et al. 2003). The island system thus represents a retrogressive succession with
prolonged absence of disturbance leading to aboveground decline in biomass
and productivity (Wardle et al. 2004b). Restoration of a natural fire regime
would reverse this succession and thus promote biomass and productivity of
these forests.
The shifts in vegetation composition aboveground have important corresponding
effects belowground. For example, soils on the small islands contain
higher concentrations of polyphenols than those on the large islands, presumably
because of domination by Picea and Empetrum (Wardle et al. 1997).
The quality of litter entering soils on the small islands is also inferior (Wardle
et al. 2003). Although N inputs from N2 fixation by cyanobacteria associated
with bryophytes (the main agent of N input to these forests; De Luca et al.
2002b) is much greater on the small islands (Lagerström, Wardle, Nilsson, and
Zackrisson, unpublished), and soils on small islands have a higher N concentration
(Wardle et al. 1997), this N is of reduced biological availability largely
because it is tightly bound in polyphenolic complexes. The net consequence of
this is reduced biomass and activity of decomposer microbes, lower rates of decomposition
and N mineralization, and lower concentrations of available forms
of N on the small islands. Concomitant with this is reduced availability of P, a
characteristic of retrogressive successions that span thousands of years (Wardle
et al. 2004b). The reduction in soil biological activity and nutrient availability
creates aboveground feedbacks, ultimately reducing plant nutrient acquisition,
standing plant biomass, and NPP (Wardle et al. 1997 and 2003). Restoration
of the natural fire regime in these forests to reverse or arrest this retrogressive
succession would in turn promote soil biological activity and nutrient supply