So often these days, funding for plant ecological research is provided only on a short term basis, for one to three years - the life of a postgraduate project. And yet extrapolations made from short term research can prove to be mistaken over the longer term. For example, if two out of three years of a project are exceptionally wet, one is likely to get very different results from those when two out of three years are drier than average - extrapolating from either extreme may give a misleading picture of what really happens.
The value of long-term monitoring
Given the fragmented nature of Cumberland Plain woodland remnants we see the primary aim of managers of particular remnants is to maintain in the longer term the complete set of species that have persisted on that site and to manage the area over time so that all these native species are maintained. Our research has been focused on documenting the biota of the reserve and to developing strategies to direct change in appropriate directions to benefit long-term survival of as many native species as we can. Some species will need particular attention. With 140 native species in the woodland we still have a long way to go!
Despite the gaps and question marks, our records since 1988 are very valuable because they provide a picture of change over the medium to longer term - a picture that is normally very hard to acquire.
An example of where out work has be able to give direction to management has been our documenting of the rate and spread of the exotic woody shrub African olive *Olea europea subsp. cuspidata. The increase in Olea has been met by a program of cutting and poisoning by a team of staff and volunteers. This was begun in 2001, and has lead to the removal of most of the Olea from the woodland. Further invasion will continue particularly when wet weather allows seedling establishment, so there will continue to be a need to remove seedlings. Work with fire has however established that periodic burns may kill juvenile plants and this may help keep the Olea in check.
Field monitoring over 14 years has allowed us to develop the following very important points on vegetation dynamics in Cumberland Plain Woodland:
- many woodland species occur only in localised patches, and do not spread widely or quickly
- for most species seed dispersal is local rather than long-distance
- the force driving processes in the woodland appears to be rainfall rather than temperature
- growth and flowering of many species tends to be opportunistic in relation to rain, rather than fixed in response to day length
- periodic drought, rather than fire, appears to have been a driving evolutionary force for individual species
- for most species, persistence is via rootstocks, evolved in response to periodic dryness, but also enabling survival after fire
- recruitment from seed is episodic, related to rain after drought (or after fire if it has the same effects as drought), therefore colonisation of new areas is slow
What this means for management and conservation
- Today’s remnants need to be managed to conserve all species at each site
- Patchy plant distributions mean remnants vary in their species composition, and all remnants, not just the large ones, are likely to be needed to conserve all species
- Episodic recruitment and opportunistic behaviour need a variety of treatments in management processes such as fire
- The number of species visible at a site fluctuates in response to seasonal variables, particularly rainfall, and multiple surveys may be needed to record all species present.
Asterisk * indicates exotic species naturalised at the Australian Botanic Garden.