The Aim of this Review
The aim of this review is to present existing ecological knowledge of fynbos and Cyclopia spp. (with
a focus on C. intermedia), which is relevant to the development of guidelines for the sustainable
harvesting of wild honeybush. General ecological aspects that are important to understand in this
context that will be covered are ecological determinants of fynbos, biological characteristics of the
Genus Cyclopia and C. intermedia, variability within this species and responses of reseeders and
resprouters to fire and harvesting.
Fynbos ecology
The Fynbos biome (Figure 1) is the largest of the biomes in the Core Cape Floristic Region, covering
some 90 000 km2 (Manning and Goldblatt, 2012). All species of Cyclopia grow in fynbos (Schutte,
1997), the characteristic vegetation of the biome. Fynbos is associated with nutrient-poor soils, most
derived from sandstones and quartzites of the ancient Table Mountain Group. However, some
fynbos communities grow in coastal lowland settings on leached, aeolian sands and calcareous soils
derived from calcrete and limestone. Only one commercial species of Cyclopia is found in lowland
fynbos, namely C. genistoides (kustee).
Fynbos is a shrubby vegetation characterised by the presence of three plant types: proteoid shrubs,
which are usually large-leaved species in the family Proteaceae that form the overstorey (tallest
shrubs) in mature veld (i.e. veld with a post-fire age of at least 8 years); ericoid shrubs that have
small, hard leaves and comprise several thousand species in many families (e.g. Ericaceae, Rutaceae,
Rhamnaceae); and restioids, rush-like plants in the Restionaceae. Proteoids do not have a universal
presence in fynbos but the other two plant types do.
The conservation status of the Fynbos biome is geographically biased (Lombard et al., 2003). Thus,
the mountains, where most Cyclopia spp. grow, are generally well-conserved (see Figure 1),
although important areas such as the Caledon and Bredasdorp mountains are significant gaps. On
the other hand, lowland areas are massively under-represented in the protected area system
(Rouget et al., 2014).
Rainfall
While the Fynbos biome is said to grow under a winter-rainfall regime, this is not strictly true. Only
the south-west and western parts of the biome receive more than 60% of their rainfall during the
winter months (Bradshaw and Cowling, 2014). East of a line from Cape Agulhas in the south to
Laingsburg in the north, the biome experiences year-round rainfall, although the spring and autumn
months are the most reliably wet; hence the rainfall regime is better described as bimodal. West of
the Knysna/Uniondale line, the summer months are driest, while eastwards, lowest rainfall is
recorded in winter. Interestingly, the majority of Cyclopia species grow in the bimodal rainfall region
of the Fynbos biome (Figure 2).
Fire
An important feature of fynbos, and a crucial management issue, is its exposure to regular fires.
Indeed, fynbos vegetation is supremely fire-adapted and has been exposed to fire since its inception
more than 100 million years ago (He et al., 2016). Without fire, most fynbos, especially on the deeper
soils of the lower mountains slopes, would be colonised by forest and thicket. Under natural
circumstances (i.e. without anthropogenic influence), fire-return intervals for most fynbos
vegetation are in the order of 10-50 years. The season of burn varies according to climatic regime,
with the western, winter-rainfall areas predominantly experiencing fires in the dry summer and
autumn months, the western, bimodal rainfall regions also experiencing mainly summer fires, while
the eastern bimodal rainfall regions may experience fires at any time of the year, with a tendency
for winter fires associated with hot, berg wind conditions (Kraaij and Van Wilgen, 2014). Under
human influence, the fire return intervals in many parts of the Fynbos biome have become significantly shorter, owing to the massive increase in the incidence of ignitions. In some cases this
is deliberate, so as to improve the grazing value of veld, for example in the eastern grassy fynbos.
However, in most instances fires are accidently (or negligently) started by humans, or started by
arsonists. The MODIS fire data shows fire return intervals for the study area over the past 15 years.
While the data is limited by the short period of record (15 years), in the context of this study, what
is remarkable is the high frequency of fire in and around Kareedouw, Joubertina, parts of the Kouga
mountains and the Elandsberg, all of which are wild honeybush harvesting areas.
As indicated above, fire is a crucial management tool in fynbos, enabling managers to increase or
decrease the size of species’ populations, depending on the fire regime applied. Thus, in the western
biome, winter fires may reduce the populations of proteoid shrubs and throughout the biome, fires
applied at very short intervals (four years and less), proteoids may be eliminated entirely. Why
should this happen? The answer lies in the different ways in which fynbos species regenerate after
fire.
Growth form: reseeders and resprouters
For fynbos species, there are two main post-fire regeneration strategies: resprouting and reseeding
(Keeley et al., 2012). Resprouters regenerate from dormant, fire resistant buds located on the plant’s
branches and stems, or below the ground, in lignotubers or rootstocks. In the case of reseeders, the
plant is killed by fire (i.e. it is incapable of resprouting) and regeneration occurs via seeds which are
either stored in the soil (as is the case for most ericoids) or on the plant canopy (as is the case for
most proteoids). It is commonly assumed, although somewhat inaccurately, that resprouters are
more resilient to fire since they regenerate vegetatively whereas reseeders are much less resilient
to fire since they depend entirely on seeds for population growth and persistence (van Wilgen et al.,
1992; Keeley et al., 2012). Thus, a short-interval burn, which occurs before reseeders have
replenished their seed bank, will likely result in a sub-population crash. On the other hand, it is
widely, though possibly erroneously, held that resprouters will not be affected. The same applies to
fire season when timing of a burn is associated with conditions that are unsuitable for germination
of the seeds of reseeders.
In actual fact, both reseeders and resprouters are vulnerable to post-fire population decline,
although the former less so than the latter. Recent research, which has monitored populations of
fynbos reseeders and resprouters over many decades, has shown that populations of resprouters
have declined more significantly than reseeders in the long term (Thuiller et al., 2007; Slingsby et
al., 2017). The reason for this is not entirely clear, but increased summer drought associated with
climate change has been suggested as a possible influence through its impact on seedling
recruitment. It is important to note that resprouters are also dependent on some seed regeneration
for population maintenance as adult plants eventually die. As resprouters allocate more of their
resources to lignotubers and other vegetative reproductive organs, the suggestion is that their
seedlings have less resources and are consequently more vulnerable to drought (Verdaguer & Ojeda,
2002).
The important lesson here is that it is not wise to assume that resprouters will persist indefinitely in
the veld. Adult plants have limited lifespans and require occasional seed regeneration to maintain
populations. In terms of the honeybush industry, it is therefore essential to harvest resprouters
(such as bergtee – Cyclopia intermedia) in such a way that they are still able to flower and set seed.
It is also vital that harvesting regimes enable the plants to produce sufficient carbohydrate to
replenish the buds and rootstocks that enable successful resprouting. More research is required to
determine the optimum harvesting regimes for maximizing production of honeybush foliage, and
minimizing negative impacts on resprouting capacity. What we do know is that resprouters have
much shorter lifespans than originally thought. Consequently, it is important that harvesting regimes
facilitate regeneration via seed and hence seedlings, and do not further reduce lifespans by
removing too much plant material at high frequency intervals.