the hauling of pebbles, as well as for the flattening, smoothing or furrowing of each
plot. Additional costs were the use of Stockabsorb (calculated using the amount
used per plant), windbreaks, which included material and labor, the cost of
employing a consultant and technician at an average daily rate for 40 days. Costs
were worked out per combination of treatment, which was then multiplied by the
number of plots of that treatment and then reworked to the area covered by those
plots, which yielded a cost for each treatment in (N$)/m
2 (Table 13.3). Note that
the erection of nets as windbreaks caused the largest difference in costs.
13.2.2.5 Conclusions
Results suggest that transplanting dwarf shrubs and leaving the area to recover
naturally by spontaneous restoration (succession of wind-blown seeds of plants
into the mined areas) can result in a community composition similar to that of the
pre-mining state, provided that a viable and appropriately positioned seed source is
kept intact. Factors limiting establishment and survival of seedlings in coastal dune
systems include nutrient deficiency, lack of moisture, predation, and salt spray
(Maun 1994). Rapid seedling recruitment is usually triggered by increased moisture events. Seedlings are able to survive partial burial and exhibit increased
growth in conjunction with sand accumulation. Thus, rehabilitation sites should be
established in the ‘‘wet’’ winter period, as was the case in these trials.
Table 13.3 Arrangement of Plots, Plot Numbers and other details in the Toliara Sands Rehabilitation Trials on the Pilot Plant sites
cost (N$) area(m
2 ) N$cost/m
2
netted
nets, pebbles, transplants+stockosorb
5620
750
7.49
nets, pebbles, transplant+no stockosorb
5608
750
7.48
nets, landscaped, transplants+stockosorb
5400
750
7.20
nets, landscaped, transplant+no stockosorb
5388
750
7.18
nets, flat, transplants+stockosorb
4860
750
6.48
nets, flat, transplant+no stockosorb
4848
750
6.46
nets, pebbles, no transplants
11140
1500
7.43
nets, landscaped, no transplants
10700
1500
7.13
nets, flat, no transplants
9620
1500
6.41
un-netted No nets, pebbles, transplants+stockosorb
2736
750
3.65
No nets, pebbles, transplant+no stockosorb
2724
750
3.63
No nets, landscaped, transplants+stockosorb
2516
750
3.35
No nets, landscaped, transplant+no stockosorb 2504
750
3.34
No nets, flat, transplants+stockosorb
1976
750
2.63
No nets, flat, transplant+no stockosorb
1964
750
2.62
nets, pebbles, no transplants
5372
1500
3.58
nets, landscaped, no transplants
4932
1500
3.29
nets, flat, no transplants
3852
1500
2.57
13 Restoration of Dune Ecosystems Following Mining in Madagascar and Namibia
213
plot. Additional costs were the use of Stockabsorb (calculated using the amount
used per plant), windbreaks, which included material and labor, the cost of
employing a consultant and technician at an average daily rate for 40 days. Costs
were worked out per combination of treatment, which was then multiplied by the
number of plots of that treatment and then reworked to the area covered by those
plots, which yielded a cost for each treatment in (N$)/m
2 (Table 13.3). Note that
the erection of nets as windbreaks caused the largest difference in costs.
13.2.2.5 Conclusions
Results suggest that transplanting dwarf shrubs and leaving the area to recover
naturally by spontaneous restoration (succession of wind-blown seeds of plants
into the mined areas) can result in a community composition similar to that of the
pre-mining state, provided that a viable and appropriately positioned seed source is
kept intact. Factors limiting establishment and survival of seedlings in coastal dune
systems include nutrient deficiency, lack of moisture, predation, and salt spray
(Maun 1994). Rapid seedling recruitment is usually triggered by increased moisture events. Seedlings are able to survive partial burial and exhibit increased
growth in conjunction with sand accumulation. Thus, rehabilitation sites should be
established in the ‘‘wet’’ winter period, as was the case in these trials.
Table 13.3 Arrangement of Plots, Plot Numbers and other details in the Toliara Sands Rehabilitation Trials on the Pilot Plant sites
cost (N$) area(m
2 ) N$cost/m
2
netted
nets, pebbles, transplants+stockosorb
5620
750
7.49
nets, pebbles, transplant+no stockosorb
5608
750
7.48
nets, landscaped, transplants+stockosorb
5400
750
7.20
nets, landscaped, transplant+no stockosorb
5388
750
7.18
nets, flat, transplants+stockosorb
4860
750
6.48
nets, flat, transplant+no stockosorb
4848
750
6.46
nets, pebbles, no transplants
11140
1500
7.43
nets, landscaped, no transplants
10700
1500
7.13
nets, flat, no transplants
9620
1500
6.41
un-netted No nets, pebbles, transplants+stockosorb
2736
750
3.65
No nets, pebbles, transplant+no stockosorb
2724
750
3.63
No nets, landscaped, transplants+stockosorb
2516
750
3.35
No nets, landscaped, transplant+no stockosorb 2504
750
3.34
No nets, flat, transplants+stockosorb
1976
750
2.63
No nets, flat, transplant+no stockosorb
1964
750
2.62
nets, pebbles, no transplants
5372
1500
3.58
nets, landscaped, no transplants
4932
1500
3.29
nets, flat, no transplants
3852
1500
2.57
13 Restoration of Dune Ecosystems Following Mining in Madagascar and Namibia
213