Carolinea 76

36 Carolinea 76 (2018) Threatened Ecosystems of South Africa, about 12 % of the original extent of all renosterveld ty- pes in the Overberg still remains – although other estimates are as low as 4-6 %. Renosterveld is listed as Critically Endangered and is at high risk of functional extinction. The viability of renoster- veld as a functioning ecosystem is influenced by a suite of factors, from those occurring as a re- sult of significant shifts in management regimes to those occurring as a result of significant frag- mentation and habitat loss. The man-induced transformation of renosterveld started with the arrival of the first European sett- lers in the mid-late 1600’s, who started by exter- minating most large game species and then be- gan to plough land for crop cultivation. However, the most significant losses occurred over the last 50-100 years. Today, almost all remnant re­ nosterveld is found on privately-owned land, ma- king it very vulnerable to the deleterious effects of poor management. There are four different types of Renosterveld in the Overberg: Rûens Silcrete Renosterveld, We- stern Rûens Shale Renosterveld, Central Rûens Shale Renosterveld and Eastern Rûens Shale Renosterveld ( M ucina & R utherford 2006). All are listed as Critically Endangered (S anbi & D eat 2009). The Overberg ‘grain-belt’ (i.e. previous- ly renosterveld regions) comprises a variety of cash crops (wheat, barley, canola, oats) as well as lucerne pastures for livestock (mostly sheep and cattle). Essentially, food crops are planted on a rotational basis and alternated with lucerne as artificial pasture for livestock. Almost all crops depend on winter rain and as with all extensive monocultures, a substantial amount of pesticide and herbicide is used on these crops. Research has shown that even a fragment of only a few hectares of renosterveld can contain exceptionally high plant diversity ( C urtis et al. 2013, K emper et al. 1999) and new plant species are still being discovered ( C urtis et al. 2013, D uncan 2017, M agee et al. 2016). While the flora in renosterveld is generally well-described, the lichen biota have been poorly explored, sugge- sting that there are species and communities of lichen yet to be discovered and described. There are very few descriptions of the lichen bio- ta at distinct sites or locations within South Africa and particularly in any of the Critically Endange- red Renosterveld vegetation types, which have been largely unexplored by lichen biologists. In this study, we explore the lichen diversity on a renosterveld reserve in the Eastern Rûens Shale Renosterveld and present a register of the spe- cies recorded here to date, during three short site visits. Despite the short sampling period, given the scarcity of information on cryptogams in this region, this study adds great value to the overall biodiversity inventory for this vegetation type. It also highlights potential indicator species found in healthy, intact patches of renosterveld, which may assist with ecological assessments of other renosterveld sites in future. Lichens are adapted to special substrate types. They are often specialized on the bark of trees and shrubs, on soil or on rock, where the sub- strate pH is responsible for further differentiated site selection. Acidic, SiO 2 rich rock types such as quartzite, bear different lichens than rock types poor in SiO 2 and rich in minerals, such as is the case with many magmatic orshale rock (the latter found in the study area). Foliose lichens which grow relatively fast may switch from one substrate type to another, mostly within a small pH-range. Thus some of the more spectacular lichen spe- cies may be found on rock or on soil (especially in dry climate regions), or on twigs and on rock. 2 Study area This study took place on the Haarwegskloof Re- nosterveld Reserve, in the Overberg region of the Western Cape, South Africa. The Overberg essentially lies between Grabouw and Heidel- berg (west to east), and includes the Agulhas Plain in the south, with the Riviersonderend and Langeberg Mountains forming its boundary in the north. There are 23 types of Renosterveld described in the Cape Floristic Region ( M ucina & R utherford 2006) and these are broadly divided into moun- tain and lowland renosterveld. The lowlands of the Cape Floristic Region are further divided into two broad types: West Coast and South Coast Renosterveld. The Overberg comprises South Coast Renosterveld, which is further divided into four different vegetation types (Eastern-, We- stern-, Central-Rûens Shale Renosterveld and Rûens Silcrete Renosterveld). Due to the extensive transformation of the Over- berg lowlands, renosterveld now only persists as hundreds of isolated remnants in a sea of mono- culture, varying in size from under 1 ha to 500 ha. However, fewer than 50 remnants are larger than 100 ha. One of the largest and most contiguous remaining remnants is found at Haarwegskloof Renosterveld Reserve, owned by WWF-SA and