VEGETATION ESTABLISHMENT FOR EROSIONCONTROL UNDER SIMULATED RAINFALL

摘要

There are approximately 4,900 native and 1,000 naturalized alien plant species inCalifornia, but only a few hundred are reliably useful in erosion control. Specifying native andnaturalized vegetation mixes for use in hydroseeding or plug planting with erosion control(EC) methods can have varying results for minimizing accelerated soil erosion. CaliforniaPolytechnic State University, San Luis Obispo, in conjunction with California Department ofTransportation (Caltrans) and California State University Office of Water Programs, Sacramento, conducted this study. The general goal of this experiment was to select nativeand non-native plant species that demonstrate initial fast growth and potential long-term ECtreatments to improve water quality. Three vegetation treatments and five erosion controltreatments were randomly assigned to each of 30 soil boxes in a replicated, crossed design.The highest amount of vegetative cover was consistently found with Jute netting(58%). The least amount of vegetative cover was seen with Gypsum (43%). Grass cover wasincreased the most by Straw. Caltrans-District 5 (D-5) native seed mix resulted in statisticallylower amounts of total runoff relative to commercial EC seed mix (11,800 g vs. 87,000 g).The control had significantly higher total runoff (965,000 g). The D-5 native seed mixproduced the lowest average total sediment (92 g) while the control had the highest (14,400g). Jute, Bonded Fiber Matrix (BFM) or Straw produced the best overall water quality. BFMhad the lowest sediment load (0.4 g) while Tackifier or Gypsum had the highest concentrationof sediment. Nitrogen uptake increased as plant cover increased, thus improving the qualityof the runoff. Phosphorus increased in the runoff as vegetation decreased.Plug planting produced three-fold the amount of cover of California Brome and onethirdthe amount of weedy annual plants as compared to the hydroseeded boxes. Plugtreatments produced no statistically significant difference in total sediment load, suggestingthat 22 plugs/m~2 may have a financial advantage over 44 plugs/m~2. Imprinting producedgreater California Brome cover than all other treatments.Preliminary results indicate benefits of using Jute netting for optimum vegetationcover. Water quality improvements were seen the most with the use of BFM, Jute and Straw.These findings suggest a strong relationship exists between vegetation establishment andEC treatment that can be useful in the field to improve water quality. Therefore it is importantto determine the final goal for each project site before determining which erosion controlproducts and vegetation are appropriate for the site.