Eve Brantley

Influence of Chinese Privet (Ligustrum sinense) on Decomposition and Nutrient Availability in Riparian Forests

Abstract As invasive species become increasingly abundant in forests, their presence may influence a number of key nutrient cycling processes. For example, Chinese privet has become well established in southeastern forests and continues to spread. Two studies, a multisite field investigation and a controlled approach on a single site, were conducted to examine the role of Chinese privet (Ligustrum sinense) on decomposition within riparian forests of the Georgia Piedmont. The field study also investigated the effects of privet presence on soil nitrogen (N) mineralization and microbial carbon and N immobilization. Both studies utilized a litterbag approach to examine how increasing proportions of privet in foliar litter influenced mass loss rates and nutrient dynamics. The field investigation included litterbags with representative proportions of the five dominant species from 16 sites. Litterbags in the controlled study were composed of specific levels of privet litter within bags (0, 10, 20, 30, 40, and 50% Chinese privet) as treatments. The litter quality of four native species was compared to Chinese privet in the controlled study. Both studies showed significant positive relationships between percentage of Chinese privet in litterbags and decomposition rates (2.6-fold rate increase with 30% privet in litterfall). Chinese privet leaf litter had lower lignin and cellulose concentrations, higher N concentrations, lower lignin ∶ N ratios, and narrower C ∶ N ratios than the native species. The positive relationship between mass loss rates and the proportion of Chinese privet in litter indicates that Chinese privet enhances decomposition rates as it becomes more abundant. During summer, N mineralization showed approximately a fivefold increase; during winter, microbial biomass N increased by approximately 30% on sites with the highest levels of privet in the understory. Consequently, C and N dynamics in Piedmont riparian forests were significantly influenced in direct proportion to the amount of privet present in the understory. Nomenclature: Chinese privet, Ligustrum sinense Lour. Interpretive Summary: This study examined the influence of a common invasive species, Chinese privet, on the biogeochemical functioning of deciduous riparian forests in the southeastern United States. Although Chinese privet is widely established as a component of floodplain forests, we know very little about how its presence might affect key drivers of forest productivity such as nutrient cycling. We found that C turnover rates in the forest floor increased by 260% on sites where litterfall was composed of 30% or more of Chinese privet. Similarly, during summer, N availability in surface soils increased fivefold on severely invaded sites. The implications of these changes for C storage and forest productivity are likely to be pronounced. Faster turnover times for C may stimulate a net decrease in soil storage since lower soil storage tends to be associated with faster decomposition. Given that virtually all forest sites in the southeastern United States are N deficient, increased N availability should stimulate net primary production. Because extensive control of Chinese privet is only feasible on a small-scale basis, it is important to understand how invasion may alter key societal values of these forests. Although forest productivity may increase, there may be a redistribution of growth toward forest components that have less economic value than many overstory species. In addition, wetland forests are stereotypically known as hotspots for C storage and sequestration and, consequently, that role may change in systems in which Chinese privet is a major component. The latter possibility is important in considerations of C mitigation strategies.

Restoring neighborhood streams: planning, design, and construction

If you are looking for an urban stream restoration roadmap that outlines the importance of community collaborations, persistence, planning, design, maintenance, and assessment to set goals for resilient stream systems—this is it. Ann Riley presents an optimistic yet pragmatic discussion on urban stream restoration technology, science, and collaboration to improve ecosystems and engage citizens. Dr. Riley encourages the reader to think outside of the channel to consider ecology, economics and social variables essential for successful restoration projects in an urban landscape. The lessons learned on project histories, motivations for implementation, and obstacles frame the need to connect stream systems to their landscapes and the people living around them. Ecological restoration is a young science that itself is still evolving. Chapter 1 walks through fundamental questions of the value of urban stream restoration given the expense, degraded watershed conditions, technical challenges, and social perceptions of what a stream should be and can be within these constraints. Examples from urban streams, such as the Los Angeles River, are shared to describe processes seemingly at odds such as sediment transport, flood control, and biodiversity. Urban stream evolution processes are presented to emphasize that these streams do evolve and are influenced by their watershed’s stage of urbanization. The author cites research suggesting stages of impacts and urban stream evolution should be considered in the design and expectations of a project. Further, the need to understand stream processes that are acting on the channel and how this influences the recovery rates is noted. The second chapter defines historical and current views of the guiding principles of restoration in urban stream projects. Restoration definitions spanning from the early days of the Society of Ecological Restoration to recent studies on ecosystem services are presented to frame what is possible in urban settings. Clarification of the terms rehabilitation, enhancement, creation, and naturalization are provided in the context of restoration intentions. Examples are given for stream restoration projects that support different levels of ecological functioning as a ladder approach, including (1) enhancement of controlled channels, (2) functional restoration, (3) ecological restoration, and (4) historical restoration. Dr. Riley notes that one dimensional projects that do not consider the complexity of stream processes tend to achieve the lowest rung of the ladder of enhancement rather than true restoration. This is typified by projects, for example, that seek aesthetic improvements through addition of flowering plants or removal of invasive species, but do not incorporate the interrelated improvement of stream functions such as functioning habitat supported by a meandering E. Brantley (&) Auburn University, Auburn, AL 36849, USA e-mail: brantley@auburn.edu

Triclopyr Application Timing and Concentration Influence Low-Volume Basal Bark Efficacy on Chinese Privet (Ligustrum sinense)

Chinese privet is an invasive shrub that commonly infests roadsides and bottomland forests across the southeastern United States. Its aggressive growth and ability to prolifically sprout from the root collar and shallow lateral roots makes control very difficult. Individual plant treatment methods such as low-volume basal bark herbicide application with triclopyr are commonly used for Chinese privet control. However, little research has been done to examine optimal triclopyr concentrations and application timings for the low-volume basal bark method. Furthermore, little is known regarding basal bark treatment efficacy when plant size varies. To address these questions, field studies were conducted from 2009 to 2011 at two locations in east-central Alabama near Auburn and Opelika. The triclopyr butoxyethyl ester formulation was applied in January or March to Chinese privet shrubs across a range of sizes in a commercially available basal oil carrier at 24 (5% v/v−1), 48 (10% v/v−1), and 96 g L−1 (20% v/v−1). Additionally, a triclopyr butoxyethyl ester ready-to-use formulation (90 g L−1) was applied at 100% v/v−1. Canopy defoliation, sprout height, and mortality were quantified at 6, 12, and 18 mo after treatment. Triclopyr at all concentrations was highly effective in defoliating Chinese privet and reducing height of new basal sprouts. However, mortality was concentration dependent. The 90 and 96 g L−1 treatments resulted in 88 and 89% mortality across timings, while the 24 and 48 g L−1 treatments resulted in 63 and 76% mortality. March applications were less effective as basal diameter increased, especially at the lower triclopyr concentrations where mortality fell to less than 40%. These results indicate that triclopyr is an effective treatment for Chinese privet control, but efficacy is influenced by concentration, application timing, and plant size. Nomenclature: Triclopyr; Chinese privet, Ligustrum sinense Lour. Management Implications: Chinese privet is an aggressive shrub that is especially problematic in bottomland hardwood areas of the southeastern United States. Many land managers use individual plant treatment (IPT) methods to control Chinese privet in these areas to improve selectivity and reduce non-target damage. However, little has been published regarding IPT methods for Chinese privet control. We examined basal bark treatment with triclopyr across a range of concentrations as a method for controlling Chinese privet at January and March timings. In general, we found that winter (January) applications of triclopyr from 24 to 96 g L−1 resulted in greater than 90% defoliation while applications of 48 to 96 g L−1 achieved greater than 80% mortality. Early spring (March) applications of 24 to 96 g L−1 resulted in greater than 80% defoliation. However, application concentrations of 90 to 96 g L−1 were required to achieve 80% mortality. These results demonstrate that winter applications of triclopyr as a low-volume basal bark treatment may be effective at lower concentrations than the commercial standard of 96 g L−1. However, March applications will likely require either the 90 or 96 g L−1 concentration for successful control.

The Influence of Treatment Timing and Shrub Size on Chinese Privet ( Ligustrum sinense ) Control with Cut Stump Herbicide Treatments in the Southeastern United States

Abstract Since its introduction to the United States in 1852, Chinese privet (Ligustrum sinense Lour.) has spread throughout the Southeast, invading many natural areas. Manual control by cutting or shredding is one of the most common strategies many land managers employ. However, rapid sprouting from the root collar and lateral roots commonly results in poor control. Cutting followed by either glyphosate or triclopyr application to the stumps is generally effective, but the efficacy of these herbicides in relation to treatment timing and L. sinense root collar diameter has not been evaluated. The objective of this experiment was to determine the effectiveness of glyphosate and triclopyr cut stump treatments compared with cutting alone at spring and fall timings across a range of L. sinense size classes. Studies were conducted at two locations in Auburn, AL. Treatments included cut stump + no herbicide, cut stump+ glyphosate (120 g L-1), or cut stump + triclopyr (90 g L-1). Treatments were applied to at least 50 experimental units each at April and November timings. Root collar diameter was recorded for each stem, stems were cut 2.5 cm above the ground, and herbicide treatments were applied within 30 s. Ligustrum sinense mortality and sprouting were quantified 6, 12, and 18 mo after treatment. Both glyphosate and triclopyr amine were very effective in controlling L. sinense at both spring and fall timings. However, glyphosate provided slightly better results than triclopyr when lateral sprouting was included. Application timing also was significant, with a lower percentage of sprouting following November treatments than April treatments. Stem size influenced treatment success, as larger stumps tended to sprout more than smaller stumps. These results indicate L. sinense can be controlled with cut stump herbicide treatment using either glyphosate or triclopyr with spring or fall timings at concentrations much lower than typically used.

Floristic Composition of Alabama Piedmont Floodplains across a Gradient of Stream Channel Incision

Abstract Stream channel incision in the Piedmont of the southeastern US has resulted in a loss of stream and floodplain functions. Reduced flood frequency and lowered water tables typify incised low-order streams of the region. The objective of this study was to determine if a quantifiable shift in riparian vegetation community structure exists along a gradient of channel incision. Stream channel incision was described using bank height ratio (BHR), defined as the ratio of streambank height to bankfull depth. Ten low-order streams in the Alabama Piedmont were selected across a gradient of BHR values (1.0–5.2). Stream incision is strongly correlated with a shift of community type in the ground flora stratum, from wetland-adapted species at low degrees of incision to plants typical of upland settings at incised sites. Based on Nonmetric Multidimensional Scaling (NMDS) ordinations, functional composition of the ground flora layer was significantly related to median groundwater depth and BHR. These results suggest strong linkages between channel incision, subsequent lowered water table levels and decreased soil moisture, and herbaceous/ground flora composition in floodplains of the Alabama Piedmont.