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

Chapter 4 Retrogressive Succession and Restoration on Old Landscapes 75
manipulate rainfall absorption at a range of scales and understand the magnitude
and location of water and energy flows through the landscape, including
the coupling with groundwater. Research approaches include identification and
quantifying the main system drivers and various forms of ecohydrological modeling.
Modeling how water moves in and through a heterogeneous landscape
and how it is modified by various management or restoration actions is extremely
difficult due to inherent spatial variability in soil properties (Hatton
2002, Williams et al. 2006). Soil tracer methods are useful in small uniform
plots but suffer from spatial variability. A number of process-based ecohydrological
models are available to simulate how changed land-use and restoration
affects ground water recharge, for example, the WAVES model Zhang and
Dawes (1998) and Silberstein et al. (1999). Other relevant models that range
in spatial scales from plots to regions and with various levels of complexity
are reviewed by Walker et al. (2002). But one has to accept that these processbased
approaches involve broad approximations, and because of the lack of
lateral flow across the polygons or cells of most models, extrapolation beyond
the research plot is difficult. The most appropriate use of process-based modeling
involves the development of possible scenarios that are amenable to field
verification. Likewise, the partitioning of rainfall excess into various forms of
predicted outflow is highly uncertain given variable patterns of plant water use
and seasonal differences in rainfall (Dunin 2002). Spatial heterogeneity exists
at many scales from preferred pathways of water through soils at a given site
to patterns at regional scales (Williams et al. 2001). At the broadest scales,
the overall control of salinization is through topography, because in a general
sense topography integrates lateral and vertical water movement. This link
with topography is used in the FLAG model (Summerell et al. 2000) using
detailed terrain data and a fuzzy logic approach to identify areas of potential
salinization.
Given that the key mechanisms changed by agricultural development are associated
with the surface soil layers, we suggest that the principal restoration
objectives in salinized lands at the farm scale should be: First, develop a buffer
or series of buffers in the surface soil that store and slowly release water. Practices
that improve soil organic matter content and improve soil fauna activity
would appear to be instrumental in developing such a buffer. Second, ensure
that excess water is of high quality and is able to move to where it can be utilized
or stored. Third, develop the agricultural landscape around a vegetation mosaic
based on different functionality, including phases of succession from grassland
to shrubland to woodland. In this scenario the vegetation mix includes pasture,
crop, shrub, and tree species with various rooting depths and architecture
selected to utilize water and nutrient resources from various soil layers.
The question now posed is: do any currently used restoration approaches
meet these broad objectives?
4.4 Restoration Methods Used in Australia in Salt-Affected Landscapes
4.4.1 Widespread Tree Planting for Salinity Management
At the broad scale, the thinking that underpins the vast majority of investments
in research and development programs, community projects, or commercial
forestry, focuses on a tree planting solution. The idea is that deforestation caused