Project reference: 1999-02
Quantifying Possum Damage in Radiata Pine Plantations
Project description:
Background:
The influence of introduced animal pests on native forest ecosystems has been extensively monitored throughout New Zealand over the last 40-50 years (Stewart et al. 1989, Allen 1993). Most studies have focused on the impact of ground browsers (deer, goats) on forest understorey vegetation. More recently attempts have been made to quantify damage to forest canopies caused by brushtail possums (Meads 1976, Payton et al. 1997a).
Between 1992 and 1997 the Department of Conservation (DoC) funded Landcare Research to develop the Foliar Browse Index method, a ground-based system for monitoring possum damage to forests and rare or endangered plant species (Payton et al. 1997b). The method is now widely used by DoC staff throughout New Zealand to monitor possum damage in native forests, and vegetation response after 1080 poison operations. It will be published as a joint DoC/Landcare Research manual later this year.
Possums also reside in and cause damage to radiate pine plantations. A recent study by Jacometti et al. (1998) built on earlier work by Keber (1987) to assess possum damage to 3-20 year old radiate pine at Tairua Forest near Whangamata. The authors report low but highly variable levels (0-30%) of damage between plantation blocks, with needle clipping and damage to lateral branches most common.
Direct observation of tree canopies has been widely used to assess the impact of insect populations, nutrient deficiency, and pollutants on the health of dominant timber producing species. Tree canopies are assigned to one of a series of predetermined classes, often defined using diagrams or photographs (e.g., Innes 1990). Because these methods are based on a scoring system, rather than on counts or measurements, careful attention needs to be paid to questions of reliability and repeatability (e.g., Innes 1988, Innes & Boswell 1990).
Proposal:
Given the patchy nature of possum damage radiata pine and the lack of a standardised method for assessing possum damage to pine plantations, we propose to use our recent experience in developing a scoring-based method for assessing possum damage to native forests to develop an assessment method for use by plantation forest managers.
We will (1) review existing methods used by foresters for assessing damage to tree canop (2) trial the proposed method in at least two New Zealand plantation forests, (3) describe the method in a report, and (4) present the results of our study to a meeting of the New Zealand Forest Health Collaborative. As with the Foliar Browse Index method (Payton et al. 1997b) we would propose letting forest managers trial the method for several years before finalising the methodology and publishing it as a manual for plantation foresters.
The proposed project would run over two years. In year 1 we would complete the review of existing methods, ask members of the Forest Health Collaborative to identify pine plantations that are being damaged by possums, and establish trials in at least two of these forests. The trials would be remeasured in year 2.
Research Provider:
Landcare Research
