Ecological Effects of Forest Canopy Disturbance on the Understory Plant, American Ginseng (Panax quinquefolius L.)

Historical accounts suggest that American ginseng was once far more abundant than it is today, and extensive changes in forest canopy structure and ginseng habitat caused by clearcut timber harvest occurred coincidentally to the precipitous decline in abundance. The presence of natural American ginseng populations after widespread clearcuts suggests that ginseng can survive under sparse canopies, and the presence of ginseng in the second growth forests common today suggest that ginseng can survive under dense canopies. However, performance may not be optimal at either end of the disturbance spectrum, and the net effect of direct and indirect anthropogenic canopy disturbances on ginseng has been unknown. The present suite of studies addresses the question how does American ginseng respond to changes in forest dynamics that result from changes in canopy disturbance regimes caused by humans? I first determined how different types of disturbances affected canopy openness on the scale of a small herbaceous plant. In Chapter 2, I found that canopy openness after timber harvest was greatest at the most intensely harvested site, and that subsequent understory canopy closure differed from that occurring in higher strata. Relative canopy closure was greatest in areas with high densities of shade-intolerant weedy and invasive species. The purpose of Chapter 3 was to determine if canopy disturbances via patch cut timber harvest were physiological stressors to American ginseng, or whether increases in light following timber harvest benefited carbon assimilation and growth. I found that ginseng is a \u27slow opportunist;\u27 photosynthesis and growth increased following canopy disturbance, but stimulation lagged behind changes in canopy structure. Although ginseng benefited from a patch cut timber harvest, it was unclear whether varying intensities of timber harvest deferentially affected the survival, growth, and reproduction of ginseng. In Chapter 4, I found that survival generally decreased following timber harvest, and was lowest at the most intensely harvested site. However, growth and seed production increased in individuals that survived. In order to provide an integrated assessment of survival, growth, and fertility following canopy disturbance, I quantified the demographic response of five populations of American ginseng to natural disturbances whose regimes are being altered by climate change. In Chapter 5, I found that population growth rate increased after natural canopy disturbances, and did so even at the current frequency of disturbance within American ginseng populations. Additionally, canopy disturbances produced sustained increases in population size via influxes of seeds to the seed bank. These studies provide clear evidence that American ginseng is surprisingly resilient in the face of rapid environmental shifts. Further, American ginseng, and perhaps similar herbs, benefit from moderate intensity, anthropogenic canopy disturbances whose frequencies and spatial extents are predicted to increase

Demographic hallmarks of an overbrowsed population state in American ginseng

Effects of high deer herbivory in North America on populations of favored plant browse species have been well-documented, however since less palatable plants now dominate the understory, we asked whether these species could be vulnerable as well, and if so, what symptoms might signal that this was occurring? Using American ginseng (Panax quinquefoliusL.) as our representative less palatable understory plant, we compared two subpopulations within a single natural population that were differentially exposed to browse; one isolated from deer by growing atop a large, flat-topped boulder, and a browse-exposed subpopulation in the surrounding low-lying area. We tested the hypothesis that deer effects would be manifested in all parts of the life history; through reduced growth, survival and reproduction. In turn, we hypothesized that browse would reduce population growth rates, and that differences in stage structure of the population would be produced. Taking advantage of a 20 year record of formal demographic censusing, we showed that browse effects were manifested primarily in reduced size-specific growth, while size-specific fertility and survival were relatively unaffected by exposure to browse. Demographically, these differences in growth were sufficient to drive population size reductions of 4.5%/y in the off rock subpopulation while the on rock plants slowly increased in number. High browse off the rock resulted in high proportions of plants in a stunted juvenile state in the off rock population relative to the on rock plants. A high proportion of juveniles is therefore a clear symptom of an understory subjected to chronic overbrowsing, providing land managers a rapid way to assess whether deer could be impacting understory biodiversity. The sharp demographic contrasts we observed between browsed and unbrowsed subpopulations also implies that promotion of refugia within managed lands will likely become increasingly important management tools for biodiversity preservation as long as unchecked deer populations persis

Demographic hallmarks of an overbrowsed population state in American ginseng

Effects of high deer herbivory in North America on populations of favored plant browse species have been well-documented, however since less palatable plants now dominate the understory, we asked whether these species could be vulnerable as well, and if so, what symptoms might signal that this was occurring? Using American ginseng (Panax quinque- foliusL.) as our representative less palatable understory plant, we compared two sub- populations within a single natural population that were differentially exposed to browse; one isolated from deer by growing atop a large, flat-topped boulder, and a browse-exposed subpopulation in the surrounding low-lying area. We tested the hypothesis that deer ef- fects would be manifested in all parts of the life history; through reduced growth, survival and reproduction. In turn, we hypothesized that browse would reduce population growth rates, and that differences in stage structure of the population would be produced. Taking advantage of a 20 year record of formal demographic censusing, we showed that browse effects were manifested primarily in reduced size-specific growth, while size-specific fertility and survival were relatively unaffected by exposure to browse. Demographically, these dif- ferences in growth were sufficient to drive population size reductions of 4.5%/y in the off rock subpopulation while the on rock plants slowly increased in number. High browse off the rock resulted in high proportions of plants in a stunted juvenile state in the off rock population relative to the on rock plants. A high proportion of juveniles is therefore a clear symptom of an understory subjected to chronic overbrowsing, providing land managers a rapid way to assess whether deer could be impacting understory biodiversity. The sharp demographic contrasts we observed between browsed and unbrowsed subpopulations also implies that promotion of refugia within managed lands will likely become increasingly important management tools for biodiversity preservation as long as unchecked deer populations persist

The Probability of Spotted Lanternfly, Lycorma delicatula (Hemiptera: Fulgoridae), Escape Differs Among Life Stages and Between Two Trapping Techniques Commonly Used By Landowners, Sticky Bands and Duct Tape.

The invasive Lycorma delicatula (White) was first identified in Pennsylvania, U.S.A. in 2014, and has since increased its range to several Eastern states. Lycorma delicatula pose a serious threat to many native species, including hardwoods and grapes, and land owners are continually seeking effective traps to control populations. Both commercially-produced Web-Cote brand sticky bands and less expensive duct tape are often used by land owners to trap L. delicatula. However, the probability of escape from these adhesives has not been formally assessed, and almost certainly differs as a function of life stage and type of adhesive used. The purpose of this work was to determine if the effect of adhesive type (Web-Cote sticky bands vs. duct tape) on the probability of escape differs based on life stage. Additionally, we wanted to know how escape probability differs among life stages when individuals were exposed to each adhesive type, separately. In all life stages, the probability of escape from duct tape was greater than from Web-Cote sticky bands, indicating that sticky bands are a more effective tool in L. delicatula population control. In trials using only Web-Cote sticky bands, the probability of escape was low in second (21.1%), third (32.6%), and fourth (38.5%) instars relative to adults (84.1%). In trials using only duct tape, the probability of escape remained high among all life stages, with approximately 72% of second instars and 100% of adults escaping. Recent studies indicate that alternate trapping techniques, including circle trunk traps, are even more effective at capturing L. delicatula than sticky bands, though they are costlier. We propose a hybrid approach to L. delicatula trapping which utilizes relatively inexpensive sticky bands early in the season, and fewer, more effective circle trunk traps later in the season

Correction to The Probability of Spotted Lanternfly, Lycorma delicatula (Hemiptera: Fulgoridae), Escape Differs Among Life Stages and Between Two Trapping Techniques Commonly Used by Landowners, Sticky Bands and Duct Tape. The Great Lakes Entomologist 53(3-4): 170-177.

This is a manuscript correction in reference to: Desko M, Schiebel C, Silverman S, Bickel J, Felton K, and Chandler JL. (2020) The Probability of spotted lanternfly, Lycorma delicatula (Hemiptera: Fulgoridae), escape differs among life stages and between two trapping techniques commonly used by landowners, sticky bands and duct tape. The Great Lakes Entomologist 53(3-4): 170-177

Defoliation severity is positively related to soil solution nitrogen availability and negatively related to soil nitrogen concentrations following a multi-year invasive insect irruption

Understanding connections between ecosystem nitrogen (N) cycling and invasive insect defoliation could facilitate the prediction of disturbance impacts across a range of spatial scales. In this study we investigated relationships between ecosystem N cycling and tree defoliation during a recent 2015–18 irruption of invasive gypsy moth caterpillars (Lymantria dispar), which can cause tree stress and sometimes mortality following multiple years of defoliation. Nitrogen is a critical nutrient that limits the growth of caterpillars and plants in temperate forests. In this study, we assessed the associations among N concentrations, soil solution N availability and defoliation intensity by L. dispar at the scale of individual trees and forest plots. We measured leaf and soil N concentrations and soil solution inorganic N availability among individual red oak trees (Quercus rubra) in Amherst, MA and across a network of forest plots in Central Massachusetts. We combined these field data with estimated defoliation severity derived from Landsat imagery to assess relationships between plot-scale defoliation and ecosystem N cycling. We found that trees in soil with lower N concentrations experienced more herbivory than trees in soil with higher N concentrations. Additionally, forest plots with lower N soil were correlated with more severe L. dispar defoliation, which matched the tree-level relationship. The amount of inorganic N in soil solution was strongly positively correlated with defoliation intensity and the number of sequential years of defoliation. These results suggested that higher ecosystem N pools might promote the resistance of oak trees to L. dispar defoliation and that defoliation severity across multiple years is associated with a linear increase in soil solution inorganic N

Prevalence and Correlates of HIV-Risk Behaviors among Homeless Adults in a Southern City

This paper aims to describe the prevalence and correlates of HIV-risk behaviors among adults receiving transitional and emergency housing services in Memphis, Tennessee. A cross-sectional, interviewer-administered survey was conducted with a convenience-based sample (N=116) of homeless adults. Sex without a condom, sex while on drugs or drunk, and sex with an unknown person emerged as the three most prevalent HIV-risk behaviors. Sex while drunk or high on drugs was also assessed as a significant predictor for sex without a condom and sex with an unknown person. Multivariate logistic regressions revealed that mental health status, duration of homelessness, incarceration history, and sex while drunk or high on drugs were significant predictors of HIV-risk behaviors. Consideration of these important correlates in designing HIV prevention programs for this vulnerable sub-group of adults is warranted

First Year Physical Activity Findings From Turn up the Heat (Healthy Eating and Activity Time) in Summer Day Camps

Background Summer day camps (SDCs) serve 14 million children yearly in the U.S. and aim to provide participating children with 60 minutes of moderate-to-vigorous physical activity (MVPA). This study evaluated an intervention designed to increase the percent of children meeting this MVPA guideline. Design Two-group, pre-post quasi-experimental. Setting/Participants Twenty SDCs serving 1,830 children aged 5–12 years were assigned to MVPA intervention (n = 10) or healthy eating attention control (n = 10). Intervention The STEPs (Strategies to Enhance Practice) intervention is a capacity-building approach grounded in the Theory of Expanded, Extended and Enhanced Opportunities. Camp leaders and staff receive training to expand (e.g., introduction of activity breaks/active field trips), extend (e.g., schedule minimum of 3 hours/day for PA opportunities), and enhance (e.g., maximize MVPA children accumulate during schedule activity) activity opportunities. Camps in the comparison condition received support for improving the types of foods/beverages served. Main outcome measures Percent of children accumulating the 60min/d MVPA guideline at baseline (summer 2015) and post-test (summer 2016) measured via wrist-accelerometry. Results Multilevel logistic regression conducted fall 2016 indicated boys and girls attending intervention SDCs were 2.04 (95CI = 1.10,3.78) and 3.84 (95CI = 2.02,7.33) times more likely to meet the 60min/d guideline compared to boys and girls attending control SDCs, respectively. This corresponded to increases of +10.6% (78–89%) and +12.6% (69–82%) in the percentage of boys and girls meeting the guideline in intervention SDCs, respectively. Boys in comparison SDCs increased by +1.6% (81–83%) and girls decreased by -5.5% (76–71%). Process data indicated intervention SDCs successfully extended and enhanced PA opportunities, but were unable to expand PA opportunities, compared to control SDCs. Conclusions Although substantial proportions of children met the MVPA guideline at baseline, no SDCs ensured all children met the guideline. This intervention demonstrated that, with support, SDCs can help all children in attendance to accumulate their daily recommended 60min MVPA. Trial registration ClinicalTrials.gov NCT0216180

Natural images from the birthplace of the human eye

Here we introduce a database of calibrated natural images publicly available through an easy-to-use web interface. Using a Nikon D70 digital SLR camera, we acquired about 5000 six-megapixel images of Okavango Delta of Botswana, a tropical savanna habitat similar to where the human eye is thought to have evolved. Some sequences of images were captured unsystematically while following a baboon troop, while others were designed to vary a single parameter such as aperture, object distance, time of day or position on the horizon. Images are available in the raw RGB format and in grayscale. Images are also available in units relevant to the physiology of human cone photoreceptors, where pixel values represent the expected number of photoisomerizations per second for cones sensitive to long (L), medium (M) and short (S) wavelengths. This database is distributed under a Creative Commons Attribution-Noncommercial Unported license to facilitate research in computer vision, psychophysics of perception, and visual neuroscience.Comment: Submitted to PLoS ON