Coarse Woody Debris Treatment
In temperate forests and woodlands globally, fallen timber, or ‘coarse woody debris’(CWD), has a major influence on the structure and function of ecosystems, it provides shelter and foraging sites for native mammals, reptiles, invertebrates and frogs. There is limited information on the structure and function of CWD in yellow box – Blakely’s red gum grassy woodlands, but the negative effects of broadscale removal of CWD on biodiversity and ecosystem function is well recognised in Australia.
Coarse woody debris takes a long time to accumulate in woodlands, and reversing the negative effects of loss cannot be achieved simply by preventing removal. To overcome the lack of CWD and its slow accumulation, deliberate addition of CWD can be an effective way of reversing negative effects. To our knowledge, this has never been attempted in yellow box – Blakely’s red gum grassy woodlands on the scale undertaken in this experiment.
There are no pre-European ‘benchmark’ sites containing yellow box-Blakely’s red gum grassy woodland from which to assess ‘natural’ levels of CWD. Therefore, the amount of CWD that was added to the treatment sites was determined from an earlier investigation in both reserves. This study showed that 20.5 tonnes/ha was a medium amount of CWD to added to both reserves (Manning et al 2007). It was not assumed that represented the ‘natural’ levels of CWD, but rather that it would produce a significant treatment effect. As well as overall tonnage, there is some evidence that the pattern of CWD is also important to organisms. Understanding the effect of that pattern of CWD distribution is important because:
- it is useful for managers to be able to optimise the effectiveness of additional CWD as a management practice;
- there could be different levels of effort and disturbance associated with placing CWD in the field;
- the amount and spatial arrangement of cover from predators affects the ‘useability’ of a landscape by animals.
The CWD treatments were as follows:
- No added CWD (controls);
- 20 tonnes of CWD per ha distributed in a dispersed pattern – ‘Dispersed’;
- 20 tonnes of CWD per ha distributed to mimic a natural tree fall - ‘Clumped’;
- 40 tonnes of CWD per ha with both dispersed and clumped distribution sites - ‘Dispersed and clumped’.
In October 2007, a total of 2000 tonnes of CWD was added to 72 experimental sites for the experimental treatments. The diagram below shows the different treatments applied to the sites.
- Manning, A. D., Lindenmayer, D. B. , Cunningham, R. B., (2013) Bring forward the benefits of coarse woody debris in the ecosystem recovery under different levels of grazing and vegetation densities. Biological Conservation 157, 204-214. Abstract
- Goldin, S. R. and Hutchinson, M. F. (2013) Coarse woody debris modifies surface soils of degraded temperate eucalypt woodlands. Plant and Soil doi: DOI 10.1007/s11104-013-1642-z Abstract
- Killey, P., McElhinny, C., Rayner, I., and Wood, J. (2010) Modelling fallen branch volumes in a temperate eucalypt woodland: implications for large senescent trees and benchmark loads of coarse woody debris. Austral Ecology no. doi: 10.1111/j.1442-9993.2010.02107.x Abstract
- Manning, A. D., Lindenmayer, D. B. , Cunningham, R. B., (2007). A study of coarse woody debris volumes in two box-gum grassy woodland reserves in the Australian Capital Territory. Ecological Management and Restoration 8, 221-224. Abstract