International Scholarly Research Notices / 2012 / Article / Tab 2 / Review Article
A Habitat-Based Framework for Communicating Natural Resource Condition Table 2 Summary of thresholds and references used to justify thresholds for the Rock Creek Park habitat-based condition assessment (see Supplementary Materials available online at doi: 10.5402/2012/384892 for threshold justifications).
Metric (by habitat) Threshold References/justification Forest Exotic tree/shrub density <5% (of total basal area) Guideline to commence removal Presence of forest pest species <1% of trees infested [46 , 47 ] see also [48 ] Presence of forest interior dwelling species (FIDS) of birds >1 “highly sensitive” FIDS [49 ] see also [50 ] Deer density Forest: < 8 deer km−2 [51 ] see also [52 , 53 ] Native seedling regeneration >31,875 seedlings ha−1 [54 –56 ] Critical connectivity (Dcrit; within Park) <360 m [27 , 57 , 58 ] Proportion of impervious surface (within Park) <0.1 [25 , 59 ] also see [60 ] Wetland (inland) Total phosphorus <36.56
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[61 ] Salinity <0.25 g L−1 [44 , 62 ] Nitrate <2 mg L−1 [24 ] Dissolved oxygen June 1–Jan 31: ≥ 3.2 mg L−1 −1 [63 , 64 ] Benthic index biological integrity (IBI) >3 [24 , 44 , 65 ] Proportion of area occupied (PAO) by amphibians 20% < PAO < 80% each spp. Management guideline; see also [66 –68 ] Physical habitat index (PHI) >42 [24 , 44 ] Artificial-terrestrial Deer density Grassland: <20 deer km−2 [51 ] see also [52 , 53 ] Proportion of impervious surface (within Park) <0.1 [25 , 59 ] also see [60 ] PM2.5 concentration <15 mg m3 [69 –71 ] also see [72 ] Ozone <0.075 ppm [26 , 69 ] also see [72 , 73 ] Wet SO4 deposition <10 kg ha−1 yr−1 [74 , 75 ] also see [72 , 76 ] Total NO3 deposition (cultivated) <10 kg ha−1 yr−1 [75 , 77 ] also see [72 ] Hg deposition <2 ng L−1 [78 –80 ]
