A survey of mammalian browsing damage in Tasmanian eucalypt plantations

Eucalypt seedlings growing in Tasmanian forestry plantations can be damaged by the Bennett's wallaby (Macropus rufogriseus), Tasmanian pademelon (Thylogale billardierii), common brushtail possum (Trichosurus vulpecula) and rabbit (Oryctolagus cuniculus). This paper reports the results of damage surveys carried out during 1994 to 1997 at 32 Eucalyptus nitens and 3 Eucalyptus globulus plantations. Browsing damage was evident at all 35 plantations. The percentage of seedlings damaged ranged from 14 to 97% at six months after planting and from 17 to 100% at 12 months. Mean browse score (MBS) ranged from 0.2 to 3.8 at six months and from 0.2 to 4.7 at 12 months. There was a strong exponential relationship between these two measures of damage. Browsing damage was estimated to have reduced firstyear E. nitens growth rates by between 12 and 100% (mean = 36, sd = 22.9). The mean percentage of seedlings recorded with browsing damage at plantations where 1080 poisoning operations had been carried out (12 months: mean = 50, sd = 26.7) was significantly lower (P < 0.01) than for plantations where 1080 was not used (mean = 84, sd = 18.5). The mean browse score recorded at poisoned plantations (12 months: mean = 1.2, sd = 1.14) was also significantly lower (P < 0.05) than that recorded for unpoisoned plantations (mean = 2.1, sd = 0.70). Seedling survival to 12 months was generally high (mean = 88%, sd = 10.7) and there was little evidence to suggest that survival of E. nitens during the first year following planting was strongly influenced by browsing damage.