Developing and implementing long-term monitoring protocols for restoration efforts along riparian corridors in Northern New England

The conservation community is implementing riparian restoration projects throughout the State of Vermont, USA. In an effort to improve the effectiveness of restoration plantings, this study was designed to assess how tree health and survival was related to plant species, plant protection (tree tubes and brush mats), nursery provider, tree planter, planting technique, and plant origin. Researchers visited riparian restoration projects in six watersheds in Vermont, and collected data at 41 sites. Fourteen sites were surveyed the year they were planted and the following growing season (May thru September 2008 and 2009), while an additional 30 sites were surveyed in 2009 that were planted as far back as 1997. Trees were surveyed along transects set up at each restoration site. Transects were marked with stakes at their endpoints and each tree was marked with a numbered tag. Each transect sampled a minimum of 10 trees. Contingency tables were used to compare the frequency of survivorship for seedlings with different forms of tree protection (tree tube, mat, both), species, project, condition, and girdling activity. A nonparametric three-way analysis of variance (Wilcoxin signed rank ANOVA) was used to analyze the effects of survival, tree protection and girdling on variation in mean seedling height. Of the trees planted in 2008, 88% survived the first growing season, and 80% survived the second growing season. Identifiable tree death causes include competition by reed canary grass (Phalaris arundinacea) and other grasses, flooding, bank erosion, trampling, accidental mowing, girdling by beavers and meadow voles, and browsing by deer. Species most likely to survive the first full growing season included ash (Fraxinus spp.), maple (Acer negundo), willow (Salix spp.), and dogwood (Cornus spp.). Surviving trees increased in height after the first full growing season, but trees planted with tree protection (mats and tree tubes) increased the least. Although mats and tubes do not promote height growth, they do increase survival. Girdling was one variable that decreased survival, but tree tubes do not prevent trees from being girdled. Additionally, tubes on trees planted eight years ago showed no signs of disintegration and were actually found to be girdling otherwise healthy mature trees.