Risk Mitigation

Risk associated with crop production is probably the main limiting factor to increasing harvests from industrial wood plantations in South Africa, and the yield expectation associated with current silviculture practices is unlikely to be frequently attained in practice. Re-establishment is subject to considerable within-season variability in weather conditions. Periods of low rainfall, high temperature, hail, early and late season frost and extreme winter frost can reduce post-plant survival leading to replanting or the uncertain outcome from blanking operations. Pests and pathogens also contribute to poor re-establishment success, sometime in conjunction with abiotic environmental stress conditions. Resultant below-target stocking and stand variability will detract from harvest yield relative to expectation. Reducing the frequency of these occurrences will contribute to overall wood supply and the success of individual growers.

This research focus area aims to reduce risks associated with tree growing by developing recommendations that will mitigate specific issues, and encompasses biotic, climatic and edaphic risks. The largest component of research deals with pest and pathogen risks, addressing current major threats to different crops in the sector; wattle rust and eucalypt canopy pests. The ability of forestry sites to sustain nutrient supply and productivity over successive rotations, and in the face of changing forestry practice, remains a major uncertainty, and research is underway to address these issue.s

Research Projects

Forest Protection Research: Eucalypt Canopy Pests

There are a growing number of insect pests infesting the canopy of eucalypt plantations. These leaf-eating, sap-sucking or gall-forming pests vary in preference for different species and hybrids and different environments, and their combined impact and relative contribution to reduced crop growth and yield has received only limited attention. This project is working closely with TPCP and industry members to develop management responses to these pests (particularly Leptocybe invasa, which is having a devastating effect on eucalypt plantations across South Africa).

Forest Protection Research: National monitoring of Leptocybe and biocontrol

This research aims to monitor the extent and degree of damage associated with the gall wasp, Leptocybe invasa and the level of parasitism caused by the bio-control agent across the summer rainfall plantation area using an industry monitoring network operated by forestry companies and supported by specialist technical expertise from FABI and the ICFR.

The main outcome is effective biocontrol of Leptocyte invasa through four aspects;

Forest Protection Research: Soil Pest Complex

Most of the South African forest plantation resource is currently certified by the Forest Stewardship Council (FSC) which promotes production of wood in an environmentally friendly and sustainable manner. FSC certification is a highly regulated process and maintaining compliance with all legislation is an increasing challenge to the industry, particularly with regards to the use of chemical products. Currently, there is a need to find alternative measures that will comply with FSC regulations in controlling several forestry insect pests.

Forest Protection Research: Stand Variability & Stand Damage

In any forest plantation, there is a direct link between the intensity of silviculture practiced, and the degree of survival, uniformity and growth achieved. The more intensive the silviculture, the closer the approximation of the growth of these plots (stands), to growth data obtained from spacing trial plots. In contrast, sub-optimal silviculture, the influence of pests and disease, and/or catastrophic events during the establishment phase, result in variable growth and/or survival.

Forest Protection Research: Baboon Damage Research

During the last decade, damage to timber plantations by baboons in South Africa has reached alarming proportions. Whilst control measures have been independently developed and implemented by the affected companies, the South African forestry industry identified the need for a dedicated, industry-level focus group to deal with damage causing animals in general, with a special emphasis on baboons.

Climate Change Research

Climate change is a key uncertainty facing the forestry sector in South Africa, and there is an urgent need to link national and international research on global climate change to the issues and scale appropriate to our context, in support of considered forest management decision-making. General circulation models (GCMs) available for South Africa predict warmer temperatures and, particularly in the western part of the country, a reduction in water availability, as a consequence of reduced rainfall and increased evapo-transpiration.

Spatial Technologies: Pest & Pathogens

Monitoring and surveillance of forest pest and pathogen outbreaks together with risk assessment of the potential impact of existing and new forest pests and pathogens is an essential part of an effective forest protection management strategy, to ensure the sustainability of the sector. New generation, moderate resolution space-borne imagery is an inexpensive, effective technology for the mapping, monitoring and risk assessment of canopy pests and pathogens.

Site Productivity over Multiple Rotations

The vast majority of South African forest plantations are now in their second or subsequent rotation. However, the impact of multiple rotation forestry on soil and site productivity has not been adequately investigated or quantified. Practices that are most likely to decrease long-term site productivity include mechanised operations that lead to loss of soil porosity and promote disturbance, and biomass management practices, resulting in the loss of organic matter (i.e. biomass and carbon) and nutrients from sites.

Nutritional Sustainability

Site nutrient supply must be maintained if the productivity of successive forest plantation rotations is to be sustained.  Nutrients are supplied to trees from soil reserves that are at risk of becoming depleted through continuous removals associated with harvesting and residue management. The ability of forestry soils to resist and recover from nutrient loss is poorly understood and there is no link between laboratory-determined nutrient pool size estimates, soil supply potential and the ability of trees to take up and efficiently utilise nutrients.