Figure 1. Location of study site show<strong>in</strong>g relationship of experimental area <strong>and</strong> White Elephant Reserve
Table 1. Some characteristics of <strong>the</strong> <strong>Parwan</strong> sub<strong>catchment</strong>sNumber 1 2 3 4 5 6 7aspect north north north south south south northarea (ha) 1.5 1.5 1.5 1.6 1.6 1.6 80.9l<strong>and</strong> cover woodl<strong>and</strong> permanentpasturenative pasture woodl<strong>and</strong> permanentpasturenative pasture see Table 62.2 L<strong>and</strong>scapeThe l<strong>and</strong>scape of <strong>the</strong> experimental area has twodom<strong>in</strong>ant features; <strong>the</strong> north face of <strong>the</strong> WhiteElephant Hill (27 ha), which has slopes of 20° to 30°,<strong>and</strong> <strong>the</strong> lower slopes (54 ha) which are relatively flat(5° to 10°').The development of <strong>the</strong> Rowsley fault l<strong>in</strong>e hasremoved any stable base po<strong>in</strong>t <strong>in</strong> <strong>the</strong> stream system.Consequently, <strong>the</strong> <strong>Parwan</strong> Creek cont<strong>in</strong>ues to downcut, disturb<strong>in</strong>g <strong>the</strong> side slopes of <strong>the</strong> <strong>Parwan</strong> <strong>Valley</strong>.The comb<strong>in</strong>ation of a geomorphic <strong>in</strong>stability, basaltcapp<strong>in</strong>g <strong>and</strong> highly unstable substrate has resulted <strong>in</strong>a range of l<strong>and</strong> degradation problems, <strong>in</strong>clud<strong>in</strong>g gullyerosion, sheet erosion <strong>and</strong> mass movement.2.3 SoilsThe soils of <strong>the</strong> experimental area are of Mioceneorig<strong>in</strong>. The surface soil horizon has compactedfollow<strong>in</strong>g removal of vegetation. Ra<strong>in</strong>drop action hasproduced a widespread crusty surface layer. Thelower soil horizon has very poor structure <strong>and</strong> quicklyloses stability when wet (Hexter et al. 1956).Consequently, sheet <strong>and</strong> gully erosion are widespreadon <strong>the</strong> White Elephant Hills. The major problem is<strong>the</strong> extensive tunnel erosion, which <strong>in</strong> places hasdeveloped <strong>in</strong>to gullies up to 5 metres deep (Hexter etal. 1956). These sites provide harbour <strong>for</strong> rabb<strong>its</strong>.Where <strong>the</strong> surface layer of soil has been eroded, <strong>the</strong>ground cover degrades until eventually, only lichenssurvive (Forbes, 1948).3. STRATEGY FOR RABBIT CONTROLWITHIN THE RESERVEThe strategy <strong>for</strong> rabbit <strong>control</strong> started when <strong>the</strong>response of <strong>the</strong> experimental plot to fenc<strong>in</strong>g wasobserved <strong>in</strong> 1982-83 (Section 3.1). This promptedmore fenc<strong>in</strong>g (Section 3.2) <strong>and</strong> poison<strong>in</strong>g (Section3.3). The results lead to development of <strong>the</strong> plan. Theeffects have been monitored by surveys of rabbitnumbers (Section 3.4), <strong>and</strong> by assessment of <strong>the</strong>change <strong>in</strong> biomass follow<strong>in</strong>g rabbit exclusion(Section 3.5).3.1 Reclamation at Western end of WhiteElephant HillsAn experimental plot of 1.6 ha at <strong>the</strong> western end of<strong>the</strong> White Elephant Hills was fenced <strong>for</strong> rabbitexclusion <strong>in</strong> 1958, <strong>and</strong> 344 trees of 19 species wereplanted with tree guards. However, <strong>the</strong> exclusionfence was not ma<strong>in</strong>ta<strong>in</strong>ed, rabb<strong>its</strong> re<strong>in</strong>fested <strong>and</strong> <strong>the</strong>condition of <strong>the</strong> plot deteriorated. By 1975, <strong>the</strong> fencehad been underm<strong>in</strong>ed to a large degree, <strong>and</strong> gave onlym<strong>in</strong>imal protection. A vegetation survey at that timeshowed that <strong>the</strong>re were 250 survivors from <strong>the</strong>orig<strong>in</strong>al plant<strong>in</strong>g. There were 120 additional shrubs ofAcacia pycnantha (Golden Wattle), which regenerateprofusely <strong>and</strong> appear to be less palatable to rabb<strong>its</strong>,but <strong>the</strong>re were no o<strong>the</strong>r species (Soil ConservationAuthority, unpublished data). In 1982, rabb<strong>its</strong> wereexcluded from <strong>the</strong> plot by repair of <strong>the</strong> fence, bypoison<strong>in</strong>g <strong>and</strong> by lack of food caused by <strong>the</strong> 1982-83drought. The effectiveness of attempts at revegetationwas exam<strong>in</strong>ed, <strong>and</strong> <strong>the</strong> importance of ma<strong>in</strong>ta<strong>in</strong><strong>in</strong>g <strong>the</strong>fences was recognised as a key factor <strong>in</strong> exclud<strong>in</strong>grabb<strong>its</strong>. This lead to <strong>the</strong> development of <strong>the</strong> rabbit<strong>control</strong> strategy. By 1984, an estimated 3000seedl<strong>in</strong>gs had germ<strong>in</strong>ated <strong>in</strong> <strong>the</strong> experimental plot,with most of <strong>the</strong> orig<strong>in</strong>al 19 species be<strong>in</strong>g present.S<strong>in</strong>ce 1984, <strong>the</strong>re has also been extensiveregeneration of understorey native grasses <strong>and</strong>shrubs.
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