Direct transfer, or community translocation, comprises
salvage and replacement of intact sods' of vegetation together with underlying
soil. It has been applied to New Zealand mine
sites restoration of native grasslands, wetlands, scrub lands, and forest. It is
an equivalent technique to instant lawn or tree garden', commonly used in urban
landscaping. Two to six m2 scoops of vegetation, with up to 0.7 m of
soil attached, and including root plates of trees and shrubs, are relocated from
stripped areas ahead of mining to sites prepared for restoration. Direct
transfer uses hydraulic excavators or face shovels and dump trucks, possibly
with the aid of bulldozers and other earthmoving machinery.
The main advantages of direct transfer, compared with
sowing or planting systems for mine site restoration, are the recycling of plant
and soil materials which were often wasted by burying under overburden
materials, a significantly faster revegetation process, and restoration of the
whole ecosystem (plants, animals, birds, invertebrates, and microbes). The main
disadvantages are higher costs of stripping and dumping, a greater degree of
machine operator skill required, and scheduling becomes critically
important.
To
illustrate the key principles, this paper gives examples of successes and
failures of the technique for a variety of New Zealand
mining situations. Direct transfer has been successful for a range of
communities, from fern wetland and sub-alpine tussock grasslands to 5 m-tall
beech forest under storey and seral shrub land, and from temperate to sub-alpine
climates. Successful examples show both rapid recovery of indigenous vegetative
cover and conservation of habitat for birds and invertebrates. Failures have
resulted from excessive death of plants because of inadequate soil salvage
depths, acidic leachates, inappropriate handling of stripped sods by
inexperienced machinery operators, or prolonged drought conditions immediately
following relocation. Change in plant species composition has occurred where
clumps of vegetation are too far apart, or shifted plants were too small - in
both cases invasive weeds have smothered the original vegetation. Changes in
hydrology can also have significant impacts. Our experience indicates that the
advantages of direct transfer far outweigh the disadvantages and is now used as
the preferred restoration method,
where practicable, at mines where it has been trialled.