Provenance an Evolving Definition

The focus on provenance has only been a hot topic for the last ten to fifteen years and its definition is constantly changing as more research is carried out. Ten years ago provenance was defined by a 5 or 10 km geographic distance from the project site. More recently local provenance has been defined as a catchment area. The problem with this is that any plants that have adapted to very specific local conditions may not readily establish in different conditions within that catchment. These days the growing belief is that more time should be spent on habitat matching to ensure the best outcomes. This process focuses on matching the environmental conditions at the seed collection site with those at the new project site. Matching soil type, slope position, aspect altitude and rainfall gives the new plants the best chance of survival.

In the context to a major roadway or a project, where there will be significant soil disturbance and conceivably changes to the topography and hydrology, a broader view of provenance should be applied. Changes that have been made to the landscape as a consequence of the construction need to be taken into account and suitable plants from the broader area chosen to match the changed site conditions rather than selecting immediately local species that may have no adaptations to help them cope with the changed site.For a long time there have been concerns that introducing plants from other areas will adversely affect the genetic makeup of the local plant populations and each case does need to be assessed on its own merits but the overwhelming evidence indicates that the greatest threat to the long term viability of our native forests comes from inbreeding rather than the threat of outbreeding from introduced plants. This is a result of the fact that many of our smaller pockets of remnant forests have become fragmented and isolated and  are no longer able to cross pollinate in the same way they were able to when  they were part of larger and naturally diverse forests. With this in mind there is a growing belief that seed sourcing should concentrate less on collecting from local environments and more on capturing high quality and genetically diverse seed so that our plantings have ample genetic diversity to respond to the changing environments over the coming decades.

To embrace and achieve a good provenance collection and growing contract takes considerable time. The points that are worth considering are

• When is the seed going to be available? Some plants only flower once per year and if there is no seed available from seed banks you will need to wait until the local plants flower and set seed before you can collect it.
• Will permission need to be obtained to collect seed? Will a licence be needed? How long will it take to obtain and at what cost?
• How long will it take to grow the plants to the required size? Tube stock will be relatively quick but 100 litre trees will take many years to reach the required size.

These are just a few of the issues that ideally need to be discussed with the nursery at the time of planning the job so that a realistic decision can be reached on whether a true provenance outcome is achievable. The other point to consider is whether provenance is really relevant to the particular site or is it being considered because it is politically correct to do so?

Finally it worth remembering that our definition of what provenance is will change considerably as time goes by due to the increasing amount of scientific research that is being carried out and we should be open to new interpretations and keep informed of the changes that will take place.