By Bob and Ena Mcintyre Garden Route Branch

Weeds in our Area(Part Thirty Seven)

By Bob and Ena McIntyre– Garden Route Branch.

Fire.

The berg winds over the past weekend and ensuing fires once again compellingly remind us of our vulnerability as a consequence of the high levels of alien invader vegetation infestation outside “controlled” areas – i.e. plantations, etc – indeed a forceful wakeup call to the authorities and residents of the George area that these infestations are a serious threat to life and property as well as the biodiversity of our area.

Research has shown that the heat intensity of invader Acacia and Pinus is up to 10 times that of our indigenous plants. While Fynbos require fire at intervals to remain viable Fynbos burns with a ‘cool fire’ that is rarely threatening to life or property. Interestingly, our scrub forests, if not invested with aliens very rarely burn.

In badly infested areas unplanned fires can have a positive outcome as these events trigger ideal circumstances and opportunities to implement effective alien eradication programs. Fires trigger the mass germination of alien invader species seed - thus reducing the viable seed bank by as much as 80%. Prompt follow-up with the effective eradication of invader seedlings, succeeded by the implementation of a restoration program with indigenous vegetation, will significantly reduce the long-term impact of both fire and invader vegetation recurrence. Opportunities such as these cannot be ignored.

Other impacts of the higher intensity of invader vegetation fires are:

The physical damage to the soil, resulting in soil water repellency and greatly increased susceptibility for erosion after fire (for example, 6 tonnes of soil per hectare was lost following fires in pine stands, compared to 0.1 tonnes per hectare in adjacent fynbos in the Western Cape).

The viability of indigenous plant seeds is adversely affected whereas alien acacias are stimulated to germinate and thrive.

Re-growth of alien invader vegetation after fire is greatly accelerated. The quality of the soil is depleted and our indigenous plants do not have equally vigorous growth habits.

In short, a devastating and detrimental chain of events resulting in large scale environmental degradation, species and biodiversity loss in a very brief period of time.