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' • Protocol Appro~ Cor Etrecuve E & S Conwl - 90 <br />' whether or not it gives up this moisture for plants. In grid climates the <br />percentage of water available for plant use may be in fact the most critical <br />variable in the long term erosion control effectiveness of a system. A surface <br />applied or incorporated mulch may reduce runoff by absorption or adsorption, <br />but the retained moisture serves has no benefit to plants unless that water is in <br />' proximity to plant roots or held at tensions where it can be available to plants. <br />Field Notes: For quanritative measurement of percentage moisture retention by <br />' weight, standard AS71N tesr methods for geoteztiles can be employed. <br />' AS Available Moisture in Soil <br /> Some BMPs are better than others at preventing soil from drying out, and <br /> keeping moisture available for plants. For a quick, quantification of available <br /> soil moisture, a soil tensiometer or a soil bridge can be employed. These <br /> appararus measure the resistance an electrical current encounters when it passes <br /> through soils of varying moisture content. <br />' TM Temperature Modification <br />' Similar in some respects to increasing available moisrure, some BMPs moderate <br /> the temperature of the environment for plants and thereby influence germination <br /> and growth. In some respects, where a surface cover is concerned, color may <br /> play a major role in reflecting or absorbing sunlight. Whether or not <br /> temperature modification is important depends a great deal on the geographic <br />' area of application and slope aspect (the direction in which a slope is facing). <br /> For example, a surface applied organic mulch which reflects heat might be <br /> advantageous on a south facing slope where it reflects sunlight, modifying <br />' temperature and retaining moisture in the soil for developing plants. On the <br /> otherhand, the same mulch applied on a north facing slope late in the fall might <br /> slow soil warmup in the spring, retain too much over-winter moisture and cause <br /> seed rot. <br />' Field Notes: Temperature modiftcation can easily be determined by measuring <br />the soil temperature of an umreated area and comparing it to soil temperature <br />from a created area. Ambient air temperature above the treated soil surface can <br />' also be compared ro soil Temperatures in the soil below. <br /> <br />1 <br />O 1995 IECA <br />1 <br />