Seed ecology research for improved restoration in the Cape Floristic Region

Introduction to our ‘Guest Blog’ below (by Marnie Light)

Through some connections to our blog, it was suggest that we ask Dr Patricia Holmes to give us some information on a project that she has been involved in on the restoration of areas of fynbos in the Cape Floristic Region that have been invaded by alien (non-native) species. While this perhaps is not specifically related to ‘forest seed research’, there are certainly aspects of this study that are pertinent to many of our fellow researchers. We hope you find this guest blog interesting!

Guest Blog by Patricia Holmes (Biophysical Specialist, Biodiversity Management Branch, Environmental Resource Management Department, City of Cape Town, South Africa)

Seed ecology research improves restoration potential
in alien-invaded fynbos of the Cape Floristic Region global biodiversity hotspot

The Blaauwberg Nature Reserve spans 1500 ha of irreplaceable lowland habitat within the City of Cape Town Municipality, South Africa. All three vegetation types present are nationally threatened and under-conserved. One of these, Cape Flats Sand Fynbos, occurs on nutrient-poor, acid sands and is one of the most transformed and poorly conserved vegetation types in the country. It also supports 16 endemic plant species and over 80 IUCN-listed as threatened with extinction. Unfortunately, fynbos in the reserve has long been invaded and degraded by the Australian tree species, Acacia saligna, and is a top conservation priority to restore.

Fynbos, like Australian kwongan, is a species-rich, Mediterranean-climate and fire-driven shrubland with a very high proportion of obligate re-seeding species. Many species depend on canopy or soil-stored persistent seed banks for recruitment after fire. However, invading alien tree species out-compete the fynbos and the seed banks are no longer replenished between fires. The restoration potential, therefore, depends on the size and diversity of the residual persistent seed bank in the soil. Species with canopy seed storage, such as proteas, are among the first to be eliminated following dense alien tree invasion.

Earlier research in Sand Fynbos, as well as current research at Blaauwberg (the latter funded by Arcadia through the Millenium Seed Bank Partnership, Kew), have indicated that soil-stored seed banks are indeed highly depleted and that active restoration, in the form of species re-introduction by seed, is required post-alien clearance. Sources of seed for important functional components of the vegetation are in short supply and it is imperative to optimize restoration success through an improved understanding of the required pre-sowing treatments to break dormancy and promote germination and establishment. Current research has focussed on applying fire-related germination cues in the growth chamber, nursery and also in field trials. Some species were found to be stimulated by heat pulse alone (or in combination with smoke), smoke, scarification and diurnal temperature fluctuations for various durations. Application of appropriate pre-treatments to species prior to sowing in the field is showing positive results and demonstrates the importance of seed research in ecological restoration.

For more information on The Centre for Invasion Biology, Stellenbosch University, which is the research partner hosting the students involved in the project, click here.

A patch of Cape Flats Sand Fynbos surrounded by dense alien Acacia saligna at Blaauwberg Nature Reserve
A patch of Cape Flats Sand Fynbos surrounded by dense alien Acacia saligna at Blaauwberg Nature Reserve
An aerial image of the 100ha restoration site indicating the two main alien clearance treatments as well as the uncleared areas
An aerial image of the 100 ha restoration site indicating the two main alien clearance treatments as well as the uncleared areas
Establishment of fynbos species 18 months post-restoration sowing
Establishment of fynbos species 18 months post-restoration sowing
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