VEGETATION MANAGEMENT PLAN for Bidjigal Reserve - Land

Vegetation Management Plan - Bidjigal Reserve3.3.4 GPS MethodologyA Thales MobileMapper GPS unit was used to log data in the field, with locations being recorded inthree (3) second increments. The MobileMapper is a hand-held unit, accurate of 3.5 metres, andallowing for rapid translation of data into a Geographical Information System (GIS).Note that the GPS unit used provides an average accuracy of 3.5 metres under favourableconditions. However, due to the challenging terrain, areas of very dense canopy vegetation whichblocks satellite detection, and at times overcast or unfavourable weather conditions, the accuracy ofsome readings may have been affected. As a precaution, all data derived from GPS records providedin this Report should be regarded as indicative only.3.3.5 Bushland Condition MappingThe bushland condition mapping system used is an adaptation of the quantitative weed mappingmethod first developed by Ku-ring-gai Municipal Council (1995). This simple mapping approachdetermines the degree of weed invasion in each stratum (or layer) of a plant community – i.e. thecanopy, shrub and groundcover strata by measuring the percentage cover of weeds compared tonative species in each stratum. Each area is assigned a ‘weed class’, which is calculated from therecorded value for each stratum, and this ‘class’ is then be assigned a colour code to provide a visualrepresentation of bushland condition or health.This approach was first developed for community Bushcare volunteers and has the advantage thatbotanical expertise is not required. The observer has only to recognise the difference between anative and an introduced species, and to be consistent in their approach (see Appendix 11 for anexplanation of the Ku-ring-gai Method).However, the Ku-ring-gai Method is not particularly accurate when one or more stratum is absent –for example, in open grasslands which lack shrubs or tree cover. For the purposes of this study, theKu-ring-gai Method was modified to overcome this limitation in those Management Units where onestratum was missing. This modification assigned the missing stratum/strata weight to the remainingstratum/strata value, while maintaining the ratio value between the strata. Vines (climbers orscramblers) were assigned to the ground cover stratum for consistency.Detailed investigation of survey sites was necessarily limited by the time available, by inaccessibleterrain in some areas, and in some instances, by restricted safe access to the Reserve interior.Mapping priority was therefore given to areas where weed infestations were known to occur, orwhere they were considered most likely to occur. These included areas of known or predicted highlevels of on-going disturbance, for example, areas adjacent to tracks and trails, below stormwateroutlets, and along creeklines (particularly areas downstream from known weed sources), the urbanbushlandinterface (particularly those areas where an Asset Protection Zone was present), andareas/sites suspected of being weedy as detected from aerial photograph interpretation.Data gathered during field surveys was used to develop a condition of bushland map (commonlyknown as a ‘weed map’), and then to record priority ranking values (see Section 3.3.5 forMethodology). All impacts and management issues relevant to the spread and control of weedswere also recorded. These management issues are discussed in more detail in Section 6.UBM Ecological Consultants Pty Ltd 37