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

Chapter 3 Aboveground–Belowground Linkages, Ecosystem Development, and Ecosystem Restoration 61
restoration, and highlights the importance of considering the belowground subsystem
in both short- and long-term processes. The examples we provide above
for the interactions of herbivores, fire, and invasions in these processes each emphasizes
the importance of a combined aboveground–belowground approach
to understanding vegetation succession, the ecological role of disturbance, and
the restoration of ecological interactions and processes.
Some aspects of these aboveground and belowground interactions are clearly
predictable: aboveground communities shift through succession and ecosystem
development, from relatively rapidly growing, nutrient demanding plant
species to slower-growing, nutrient-conserving species. Parallel changes occur
in the soil subsystem, with shifts from domination by the bacterial-based
to the fungal-based energy channel, from arbuscular-mycorrhizal to ectomycorrhizal
communities, and from r-selected to K -selected soil fauna. These
corresponding shifts in aboveground and belowground communities influence
the nature of feedbacks between them, and this in turn has important consequences
for ecosystem processes such as nutrient and C fluxes, NPP, and
ecosystem C sequestration. However, at local scales, the outcome of many of
these interactions is context-dependent and hence not easily predictable; therefore
understanding these linkages may or may not be helpful for restoration
efforts depending on whether the linkages of interest are predictable over temporal
and spatial scales relevant for restoration. The challenge for future work
is to understand which aboveground–belowground linkages are important for
restoration within a given system, and in particular, understand how belowground
processes both determine and respond to restoration treatments. Below
we outline some of the key challenges and future research areas for developing
closer links between aboveground–belowground interactions, succession, and
restoration.
Belowground communities clearly play a pivotal role in successional processes,
plant community composition, and ecosystem processes (as outlined
in the sections above), but their role in restoration remains poorly understand.
A major issue that can be resolved in the short-term is determining whether
restoration efforts that focus solely on the aboveground community have the
desired effects on the belowground community. Restoration practitioners typically
focus on the aboveground components because these are visible and
amenable to manipulation. For the immediate future, soil communities will not
be widely manipulated or used to assess restoration success for the practical reason
that understanding shifts in belowground communities is relatively difficult
and requires quite specialized skills to identify or quantify soil biota. Clearly,
research is needed to determine how closely restoration efforts aboveground
are mirrored belowground; this can be accomplished in the first instance by
the inclusion of soil biologists in monitoring restoration projects. Most restoration
treatments involve either the addition of native species or the removal of
nonnative species; these adaptive management experiments can be extremely
informative if they include carefully designed controls (i.e., intact native systems
and un-manipulated, invaded reference systems), and then compare both
aboveground and belowground properties among these treatments. This approach
can be used to resolve key questions such as whether removing a weed
species from a system reverses the effects of that weed belowground, whether
there are persistent effects on the soil biota or nutrient availability in the system,
and whether these effects are minor compared to differences between intact