Grassroots Vol 22 No 1 | Page 12

FEATURE

Hollows bring new life to bare patches in Karoo even in drought

Sue Milton 1 , 2 and Ken Coetzee 3

Current Address : ¹ Wolwekraal Conservation and Research Organisation , Prince Albert www . wcro . co . za ; ² South African Environmental Observation Network , Arid Lands Node , Kimberley , www . saeon . ac . za / nodes ; ³ Conservation Management Services , George , www . conservationmanagementservices . co . za

Grazing , ploughing and kraaling can all reduce vegetation cover , and in arid parts of the Karoo , bare patches in the veld may stay bare and continue to erode for centuries . This is because , once the plant roots are gone , wind and water move away the loose soil permeable soil leaving a pavement of desert dust or bedrock . Hard surfaces shed water and dry out soon after rain , moreover wind- and water-dispersed seeds are quickly washed or blown off bare patches . Deflation hollows on Khoekhoen kraal abandoned 250 years ago are evidence for the slow recovery of bare patches . Much larger-scale damage to natural veld is now a daily occurrence as developments such as roads , mines and energy infrastructure sweep across the rugged koppies and vast , sparsely vegetated plains of the Karoo ( Milton & Dean 2021 ). Ongoing repair or rehabilitation of damaged veld is essential to sustain future livelihoods in this arid region and counter the effects of climate change ( Genis 2021 ).

With the assistance of B-tech students from Nelson Mandela University , we designed and implemented the trials described in this article .
Sites and treatments
Trials we set up in 2016 and 2017 during an unusually severe drought that lasted from 2015 until 2021 in the Central and southern Karoo and led to a loss of 25- 40 % of plants and vegetation cover ( Milton et al . 2022 ; Saayman 2021 ). The average monthly precipitation recorded on the Wolwekraal Nature Reserve from January 2016 until September 2021 was 10.3 mm . In 2017 and 2019 < 100 mm of rain was recorded over a period of 12 months . The soils of the two sites selected for the rehabilitation trials differed in depth and texture , but both were fairly flat .
Site 1 : Eroded deep silty-sand In August 2016 a group of 25 students
Wolwekraal Nature Reserve ( -33.1902 S , 22.0292 E ) to the north of Prince Albert is typical of rain-shadow succulent Karoo in that the long-term annual rainfall is 170 mm and non-seasonal . Although the property has carried no livestock for 50 years , reduced vegetation cover in comparison with neighbouring properties , a historical stone boundary wall and Khoekhoen kraals and campsites along the riverbank suggests that the land had a history of intensive grazing from which the veld has not yet recovered . It was therefore a suitable site for testing various types of restoration infrastructure described in restoration guidelines for the Karoo ( Coetzee & Stroebel 2015 , Milton & Dean 2021 ).
Figure 1 . Rehabilitation structures installed at Site 1 in 2016 . ( A ) mulched and brush-covered hollow , ( B ) materials used , ( C ) alternating brush-covered hollows and brush fences , ( D ) brush-packed gullies . ( D )
11 Grassroots Vol 22 No 1 March 2022