Platbos is a dry forest growing on nutrient weak soils. It is thought that the forest established itself during a period when the rainfall patterns of further east, other side of the Breede river, extended to us here at Platbos. The advantage of both winter and summer rainfall is significant. Since that rainfall pattern has retreated and there is winter rain only, the forest has had to make many adaptations to survive. The onset of anthropogenic climate change has exacerbated an existing challenge for trees to survive and adapt to natural climate change.

One adaptation is called “facilitation” it is where trees abandon the normal practice of spacing themselves, and growing with canopies separate from each other (crown shyness), and adopt a strategy of growing from communal clusters centered around an old stump or dying tree that has extensive decay. The decaying tree is a nutrient pocket in an otherwise dry and nutrient weak soil. What little rain that we get is also channeled down the trunks into the nutrient pocket. Decaying timber holds the moisture better than the sand which tends to repel moisture.
The second adaptation is potentially more severe in its consequences for the forest. It is the adoption of asexual propagation as a means of survival.

Sexual propagation, seed production and germination and trees growing from this, will always be first prize for a natural system. It is that process that give rise to variation of type, the breeding of adaptive strains, the ability to change with a changing climate. It is essentially our hope for systems to survive a rapidly changing climate.

It is therefore of concern that many, if not most, of the tree species at Platbos have had to adopt asexual reproduction as a means to survive, they are cloning themselves, not evolving.

They do this by coppicing, so the decaying stump of the dying tree is actually re-sprouting from its periphery. They also do this by suckering, mature nearby trees send roots over to the nutrient pocket and send up a shoot in amongst the other trees coppicing shoots. The third way is layering, the milkwood trees are very good at this. They collapse or grow along the ground and where they make good contact with the ground the stem grows roots and a “new “ tree forms.
This gives Platbos its distinctive appearance.

All the trees still valiantly produce seeds, many of which germinate, but the dry summer months however kill off the vast majority.

Having watched the forest dynamics for nearly 20 years now I can safely say that only Chionanthus trees are solely reliant on sexual reproduction for as a survival strategy. It still however makes use of the nutrient pockets. The other forest species try for sexual reproduction, and some achieve it better than others, some succeed with a mixed strategy, while other species have not to my knowledge succeeded with sexual reproduction for a long time.

The first thing to note therefore is that when we harvest the germinated seedlings from the forest floor in spring, and grow them on till they are tough enough to be planted out, we are in fact reintroducing vitally needed sexual reproduction. Variation of type, the possibility that more resilient strains are entering the landscape is hugely important, when faced with the evolutionary cul de sac that is asexual reproduction.

The actual planting technique is also taking cognisance of the dynamics that are special at Platbos. We mimic the nutrient pocket by using woodchip processed from neighboring alien vegetation stands. A 700mmx700mm pit is dug and the excavated soil is used as to make a berm to capture runoff. The pit is then filled with chip and the saplings are planted in the edge of the pit where the soil and chop meet. Approximately 7 trees are planted in each pit, the aim being to achieve a closed canopy around the pit a soon as possible. The cooling of the soil helps their survival and retards the germination of aliens. The pockets are made close to each other to minimise the time needed for complete canopy closure.

The high density planting patterns are also informed by observation and species counts done in areas where forest had naturally recovered after the farming on deforested lands ceased. As these young stand grow they will obviously thin themselves out, but as they grow the natural system will also compliment our starting efforts, and natural regeneration will occur. Reforestation by planting trees should be seen as a very necessary “kick start” of tipping systems back to balance and recovery.

This information has been supplied by Francois Krige, co-owner of Platbos Forest. Francois lives in the Platbos forest, taking on the roles of indigenous tree nursery manager, arborist, forest custodian and passionate naturalist