Lindsey Sanders Ivy Removal Techniques Spring 2010 1 Algerian Ivy Removal Techniques along a Riparian Zone in Berkeley, California Lindsey Sanders ABSTRACT Algerian ivy is an invasive vine not native to Berkeley, California which limits native plant biodiversity. In this study I examined three removal techniques for managing Algerian ivy: manual removal, foliar herbicide application, and cut-stem herbicide application. I hypothesized that cut-stem herbicide application would be the most effective removal technique and that herbicide application would not affect native seedling growth. I measured plots monthly for ivy and native seedling growth and analyzed results using a Random Complete Block Design, Tukey-Kramer analysis, and Simpson’s Diversity Index (SDI). I found no significant difference in ivy re-growth between plots, and no significant difference in native seedling growth between plots. I found that manual removal plots had an SDI double that of other treatments (0.7652). Based on these results I recommend that further use of herbicides be ceased until investigations into the effects of herbicide on native plant diversity have been completed. KEYWORDS Invasive species, Strawberry Creek, restoration, glyphosate, species diversity.Lindsey Sanders Ivy Removal Techniques Spring 2010 2 INTRODUCTION Non-native invasive plants are the second largest threat worldwide to native plant biological diversity (Scott and Wilcove 1998). Successful invaders have a high reproductive capacity and rapid growth rate, often reproducing asexually and multiple times throughout the year (Cain et al 2008). A lack of natural restraints and a generalist strategy affords many invasive species a competitive advantage (Cain et al 2008). Invasive species typically enter communities after large disturbances such as floods and droughts, which disrupt ecosystem dynamics, and establish themselves before native species can recover (Roques et al 2001). Once established, invasive plants cause a number of negative effects, include blocking sunlight and nutrients from reaching sprouting natives (Levine et al 2003) and altering nutrient cycles, hydrology, sediment deposition, fire regimes, and erosion patterns (Bossard et al 2000). For these reasons, the removal of invasive species is common in ecosystem restoration work. Algerian ivy (Hedera canariensis algeriens) is a largely invasive perennial vine native to the Canary Islands, Portugal, the Azores, and Northern Africa (Bossard et al 2000). It is classified as a weed in California with severe invasiveness, severe distribution implications, and severe impact on native plant life (CIPC 2009, USDA 2009). Like other Hedera ivy species, it has a high seed survival rate, rapid vegetative spread rate and high shade tolerance (Bossard et al 2000, CIPC 2009), making it a fierce competitor to many native plant populations with much lower growth rates and more fragile equilibrium conditions (Thomas 1998, Bossard et al 2000). Algerian Ivy has the ability to quickly spread into an area and form a thick ground cover, thereby blocking sunlight from other plants and limiting native seed dispersal (MacDougall 2005, Biggerstaff and Beck 2007). It is highly persistent and difficult to remove entirely once it has become established, as a result of its ability to re-sprout from small stem fragments and nodes (Bossard et al 2000). These characteristics make Algerian ivy a threat to native plants and are cause for its removal in restoration efforts. Algerian ivy has become a problem within the nature areas on the University of California, Berkeley campus, and has been the center of recent efforts to restore these areas. Algerian ivy has overtaken much of the riparian zone along Strawberry Creek running through the campus, and can be seen climbing native trees, weakening their branches and making them more vulnerable to damage in future storms (pers. comm., Tim Pine). In 1969, three nature areas were established on the campus to retain wildlife habitat and provide ecological study areas forLindsey Sanders Ivy Removal Techniques Spring 2010 3 students (Unknown Author 1969). In the past decade restoration efforts focused on manual removal of invasive ivy and planting native vegetation to return the nature areas to their original state as oak woodlands (Purcell et al 2007). Despite these efforts, the areas are still largely overrun with Algerian ivy, and there are simply not sufficient funds or labor provided by the University to maintain the nature areas through manual removal (pers. comm., Tim Pine). For this reason, the Strawberry Creek Restoration Project is considering the use of an herbicide to inhibit Algerian ivy growth. The product under consideration is the commercially available herbicide, Round Up® Pro. Various studies have examined the effectiveness of plant removal techniques on English ivy (Hedera helix) and similar low-lying woody shrubs (Derr 1993, Roques et al 2001, Biggerstaff and Beck 2007, Love and Anderson 2009). Derr (1993) found that herbicide application was most effective on English ivy in March when new growth was emerging. Biggerstaff and Beck (2007) cut the stems of English ivy before herbicide application to open the plant’s pores for increased herbicide absorption during the spring and found that herbicide application greatly inhibited native plant growth. Because restoration work on the UC Berkeley campus takes place primarily during the fall and winter, evaluations of the most effective methods for ivy removal and native replanting, as in this study, need to consider these cold winter months. In this study, I examined the potential of three techniques for riparian habitat restoration and Algerian ivy removal: (1) manual removal of ivy (2) foliar herbicide application onto green ivy leaves, and (3) cut-stem herbicide application onto freshly cut green ivy stems. I assessed the effectiveness of habitat restoration by (1) monitoring the re-growth of Algerian ivy after treatment and (2) monitoring the sprouting of native seedlings after treatment. I hypothesized that (1) herbicide application on cut stems would be the most effective method for reducing ivy growth, and (2) herbicide application would not hinder the growth of native seedlings. METHODS Study Sites This study took place along both the North and South forks of Strawberry Creek on the University of California, Berkeley campus (37o52’N 122o15’W). I
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