VEGETATION MANAGEMENT PLAN for Bidjigal Reserve - Land

Vegetation Management Plan - Bidjigal ReserveTable 3.2: Criteria for Priority Ranking of Sites for Bushland Regeneration & Associated WorksCRITERION BACKGROUND METHODOLOGY FOR FIELD RANKING LIMITATIONSConservation of Core BushlandSize of Core Bushland(hectares)Level of Management Assessment: ZonePriority should be given to protecting and rehabilitating the largest, intactand therefore most robust stands of bushland. Therefore, the priorityranking gives the highest score to the largest sites.For each site, the area was calculated using a GIS within the siteboundaries shown in Figures 3.2. The areas were allocated a ranking forpriority assessment (see below). The threshold areas for each score weredetermined to form a fairly even spread of the sites over the scores,thereby creating a high level of score differentiation between the sites.1) < 5 ha,2) 5-10 ha3) 10-15 ha4) 15 – 20 ha5) > 20 haThe area was calculated independently of any adjoining bushland.The threshold areas were arbitrary and were based on providing scoredifferentiation rather than ecological principals.Length of Urban-Bushland InterfaceLevel of Management Assessment: ZonePriority should be given to protecting and rehabilitating stands of bushlandwith the shortest urban-bushland interface (thereby preserving a relativelyintact core of bushland).Management Zones with a shortest urban-bushland interface are expectedto have a lower level of edge disturbance, arising from human activities,weed invasion and influx of urban stormwater. These Zones are typicallymore cost-efficient to maintain due to the relatively smaller extent of edgeimpacts. Therefore, a higher value has been given to Zones with a shorterurban-bushland interface.The length of urban-bushland interface for each Management Zone wascalculated in metres (m) using a GIS package.These lengths were allocated a ranking for priority assessment (see Table3.3). The threshold areas for each score were determined to form a fairlyeven spread of the sites over the scores, thereby creating a high level ofscore differentiation between the sites.The length was calculated independently of any adjoining bushlandAssumed that the higher the longer the Urban-bushland interface the moreintense the edge effects. Ignored the type and likely severity of edgeeffect. Field analysis partially overcame this limitation by the addition ofthe interface disturbance criterion.Disturbances onBoundaryLevel of Management Assessment: ZoneThe effort and level of resources required to rehabilitate and maintain aZone with a high level of disturbance is correspondingly high, and thereforeit is far more cost efficient to undertaken work in less disturbed sites.Therefore, the priority ranking gave the highest score to Zones with theleast amount of disturbance.Disturbances on the boundary were taken to be those within 10 metres ofthe edge of the Zones. This threshold was loosely assigned prior to thefield survey through desktop analysis, and investigated for reliabilitythroughout the field component. It was observed during the fieldworkthat most edge impacts such as easements, edge maintenance such asfencing, and elevated light levels are generally within 10 m of reserveedge.Where disturbances such as recent burning or large amounts of mulchingand clearing for bush regeneration works were noted, these were notincorporated into these criteria as they were considered to be ‘beneficial’disturbances.A 10% threshold was assigned to the area impacted upon by a disturbancebecause it was observed that most zones had at least a small amount(