Laserfiche WebLink
Herbaceous Cover , <br />For both Pre -2008 and Post -2008 revegetation targeting (and achieving) the rangeland <br />land use subcomponent of rg azin lg and, herbaceous cover of the revegetated area will be <br />considered adequate for final bond release if it is not less than 90% of the herbaceous <br />cover as determined from the reference areas with a 90% statistical confidence utilizing a <br />standard students statistical t-test comparison of the means. As allowed under the rules <br />promulgated on 9/14/05, these comparisons may utilize one of three methods detailed <br />under Rule 4.15.11 (2) [(a), (b) or (c)]. Also as allowed by Rule 4.15.7 (4), either <br />weighted- average or individual protocols will be followed depending on the resulting <br />community that evolves (see Section 4.15.7 above). For grassland testing the weighted <br />average approach (Rule 4.15.7 (4) (b)) will be utilized where reference area data and <br />revegetated area data are "weighted" (each combined into single values for comparison) <br />based on the proportional acreage of pre -mine communities within the disturbance area <br />footprint. Testing will then follow procedures detailed under Rule 4.15.11 (2) with <br />preference being given first to subsection (a) [direct comparison], second to subsection <br />(c) [reverse -null testing], and third subsection (b) [classic t- test]. <br />For "targeted" Post -2008 sagebrush steppe revegetation (targeting the rangeland land use <br />subcomponent of wildlife habitat), herbaceous cover will be considered adequate for final <br />bond release if it is not less than 70 %* of the sagebrush reference area's herbaceous cover <br />with a 90% statistical confidence utilizing a standard students statistical t -test comparison <br />of the means. If necessary, a reverse -null hypothesis testing procedure may be utilized in <br />accordance with procedures detailed in Rule 4.15.11 (2) (c). As allowed under Rule <br />4.15.8 (3) (ii), relaxation of the herbaceous cover standard for areas targeting wildlife <br />habitat post- mining land uses is designed to compensate for revegetation techniques <br />(prescribed ecological reclamation approach) that must discourage grasses to encourage <br />shrubs in the post - revegetated community. For "evolved" post -2008 sagebrush steppe <br />revegetation, the grazingland cover standard will be maintained. <br />A higher percentage of herbaceous cover is not practical or desirable for the following <br />reasons: <br />It is well documented that in mined -land reclamation the establishment of shrubs <br />to reach bond release levels has proven to be very difficult. Perhaps the most <br />detrimental condition affecting shrub establishment is the competition from <br />herbaceous vegetation. At a minimum herbaceous cover levels should be less <br />than the premining condition. If the herbaceous levels to be obtained were set <br />higher than the premining condition, the ability to achieve bond release levels for <br />• The value of 70% has been selected given the following rationale: 1) herbaceous competition must be <br />significantly restricted to facilitate emergence and growth of shrubs as indicated under Rule 4.15.11 (3) (ii); <br />2) the original value is 90 %; 3) a value of 50% seems too low to adequately control erosion; 4) by regulation <br />(4.15.11 (3)(a)) a reduction: to 70% is allowed for one of the demonstrations for revegetation success for <br />woody plant density; and 5) 70% of the herbaceous material in a native reference area should be adequate to <br />control erosion on slopes 10% or less. <br />4.15 -23 Revision Date: 6/21/11 <br />Revision No.: TR -84 <br />