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COURSE TITLE: Valley-bottom palmiet wetlands: the mysterious peatlands at the tip of southern Africa

INSTRUCTORS Alanna Rebelo

COURSE DESCRIPTION Valley-bottom palmiet wetlands: the mysterious peatlands at the tip of southern Africa

Abstract:
Peatlands are rare in the Cape Floristic Region, located along the south-eastern coast of South Africa, with weather conditions not conducive for the formation of peat. The Cape Floristic Region has a predominantly mediterranean-type climate characterised by summer drought and winter rainfall resulting from the passage of cold fronts. Mean annual rainfall for South Africa is about 464mm, and in the Western Cape is 323mm, with mean annual A-pan equivalent potential evaporation of around 2230mm. Yet surprisingly, peatlands exist in this region. Notably, valley-bottom palmiet wetlands.

Palmiet wetlands are dominated by the wetland plant Palmiet (Prionium serratum), which is a unique species taxonomically, recently moved from its own family ‘Prionaceae’, to ‘Thurniaceae’ (Poales). Palmiet has been suggested to be an ecosystem engineer by some, cited to be the species that was able to stabilize these valley-bottoms originally, and allow sedimentation and eventually the formation of peat (several peat basins have been dated to around 5000-5500 years old). Palmiet wetlands are located in high energy catchments, subjected regular flood events of high force, which would rip out any shallow rooted species. Palmiet, a deep-rooted clonal species, is highly adapted to this disturbance, and therefore is typically flattened by the flood waters, able to recover afterwards.

Palmiet wetland soils and groundwater are naturally oligotrophic with a low pH, largely due to the soils of the Cape Floristic Region being mainly highly leached dystrophic lithosols associated with the sandstone mountains of the Cape Supergroup. As a result of occupying valley bottoms, palmiet wetlands tend to be long and narrow (around 300m across). They are sparsely distributed across the Cape Floristic Region, with around eight significant palmiet wetlands remaining across the region (about 1000km across), remarkably similar in their species composition despite their isolation.

With the arrival of western agricultural practices around 300 years ago, the landscape of South Africa was to change dramatically, with the removal of wetlands, the channelization of rivers, alteration of the natural fire regime and the introduction of invasive alien trees. These changes were to alter the functioning and structure of many wetland systems in South Africa.

In this talk, the presenter will introduce (1) what is known about the structure and functioning of palmiet wetlands, (2) how this has changed with degradation as a result of agriculture and invasion by alien trees, (3) restoration and rehabilitation efforts and (4) how these peatlands and rehabilitation interventions compare with others globally.

Short Bio:
Dr Alanna Rebelo is currently a postdoctoral researcher in the Conservation Ecology Department at Stellenbosch University, South Africa. Her primary field is wetland ecology, though she is a generalist with many research interests, including wetland biogeochemistry, the ecological applications of remote sensing, the impacts of invasive alien plants (particularly trees) on the water cycle and biodiversity, and the benefits to society of intact or restored wetland ecosystems (ecosystem services). Currently Alanna is part of a large transdisciplinary team investigating the socio-economic benefits of investing in ecological infrastructure related to water security in South Africa.

Credit Points: 0.06

SYLLABUS/TOPICAL OUTLINE Palmiet wetlands are named for their dominant wetland plant, palmiet (Prionium serratum). Palmeit wetlands are found in the Floristic Region of South Africa that is characterized by a Mediterranean type of environment with moderate rainfall and high evaporation potential. Palmeit has been suggested to be an ecosystem engineer by stabilizing high energy catchments subjected to regular flood events, eventually forming peatlands through the accretion of sediments. Palmeit wetlands occur in an oligotrophic environment with low pH. They are typically long and narrow, due to their colonization of valley environments. Palmiet wetlands are sparsely distributed in South Africa, partially due to agricultural development, which has included wetland removal, river channelization, alteration of the natural fire regime, and the introduction of invasive alien trees. A synopsis is presented in palmiet wetland restoration and rehabilitation efforts, with a comparison to similar efforts across the globe.

COURSE CONTACT

Louis Mantini
9225 CR49, Live Oak, FL 32060
lfm@srwmd.org
P: 386.647.3144
F:

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