Spatial prioritization techniques are applied in conservation-planning initiatives to allocate conservation resources. Although typically they are based on ecological data (e.g., species, habitats, ecological processes)

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An accepted criterion for measuring the success of ecosystem restoration is the return of biodiversity relative to intact reference ecosystems. The emerging global carbon economy has made landscape-scale restoration of severely degraded Portulacaria afra (spekboom)-dominated subtropical thicket, by planting multiple rows of spekboom truncheons, a viable land-use option. Although large amounts of carbon are sequestered when planting a monoculture of spekboom, it is unknown whether this is associated with the return of other thicket biodiversity components. We used available carbon stock data from degraded, restored, and intact stands at one site, and sampled carbon stocks at restored stands at another site in the same plant community. We also sampled plant community composition at both sites. The total carbon stock of the oldest (50 years) post-restoration stand (250.8 ± 14 t C ha −1 ) approximated that of intact stands (245 t C ha −1 ) and we observed a general increase in carbon content with restoration age (71.4 ± 24 t C ha −1 after 35 and 167.9 ± 20 t C ha −1 after 50 years). A multiple correspondence analysis separated degraded stands from stands under restoration based on ground cover, floristic composition, and total carbon stock. Older post-restoration and intact stands were clustered according to woody canopy recruit abundance. Our results suggest that spekboom is an ecosystem engineer that promotes spontaneous return of canopy species and other components of thicket biodiversity. The spekboom canopy creates a cooler micro-climate and a dense litter layer, both likely to favor the recruitment of other canopy species.

It has been hypothesised that high-intensity fires prevent fire-dependent fynbos from being replaced by fire-avoiding subtropical thicket on dune landscapes of the Cape Floristic Region (CFR). Recent extensive fires provided an opportunity to test this hypothesis. We posit that (1) fire-related thicket shrub mortality would be size dependent, with smaller individuals suffering higher mortality than larger ones; and (2) that survival and resprouting vigour of thicket shrubs would be negatively correlated with fire severity. We assessed survival and resprouting vigour post-fire in relation to fire severity and pre-fire shrub size at two dune landscapes in the CFR. Fire severity was scored at the base of the shrub and categorised into four levels. Pre-fire size was quantified as an index of lignotuber diameter and stem count of each shrub. Resprouting vigour consisted of two variables; resprouting shoot count and resprouting canopy volume. A total of 29 species were surveyed. Post-fire survival of thicket was high (83–85%). We found that smaller shrubs did have a lower probability of post-fire survival than larger individuals but could detect no consistent relationship between shrub mortality and fire severity. Fire severity had a positive effect on resprouting shoot count but a variable effect on resprouting volume. Pre-fire size was positively related to survival and both measures of resprouting vigour. We conclude that thicket is resilient to high-severity fires but may be vulnerable to frequent fires. Prescribed high-intensity fires in dune landscapes are unlikely to reduce the extent of thicket and promote fynbos expansion.

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