Inter- and intraspecific competition and shade avoidance in the carnivorous pale pitcher plant in a nutrient-poor savanna

© 2019 Botanical Society of America Premise of the Study: Ecologists generally agree that weak interspecific competition for light contributes to high plant species diversity in ecosystems with nutrient-poor soils. However, the role of competition for light in such ecosystems that are also maintained by fire is poorly understood. I quantified intra- and interspecific competition for light in a fire-maintained nutrient-poor pine savanna by contrasting the effects of conspecific and heterospecific neighbors of the pale pitcher plant, Sarracenia alata. Methods: Accounting for initial neighbor abundance/aboveground production and initial transplant size, I measured growth and survival of small and large pitcher plant ramets of Sarracenia alata transplanted to the vicinity of natural, undisturbed mixtures of large pitcher plants and their heterospecific neighbors in the field. I tested competition for light and nutrients by clipping conspecific neighbors and by excluding prey from unclipped neighbors of transplants. I tested interspecific competition by uprooting heterospecific neighbors. Key Results: Plant survivorship increased when conspecific neighbors were clipped and/or starved but not when heterospecific neighbors were uprooted. Small pitcher plants benefited from clipping large conspecific neighbors, suggesting that competition for light was important. Large pitcher plants benefited from excluding prey from their neighbors, with no additional benefit of clipping, suggesting that competition for prey limited their survival. Transplants produced new pitchers that were taller with narrower openings (i.e., shade avoidance) when heterospecific neighbors were left intact but not when conspecifics were unclipped. Conclusions: Results demonstrate size-dependent intraspecific competition for light and nutrients and interspecific shade avoidance in Sarracenia alata, which could be important to understanding species coexistence in fire-maintained nutrient-poor ecosystems

Radial growth responses of upland oaks following recurrent restoration treatments in northern Mississippi

Fire exclusion over the past century has substantially altered composition, structure, and fuel dynamics in upland oak-hickory (Quercus-Carya) forests in the Southeastern United States. Numerous restoration efforts have been made to re-establish historical disturbance regimes into these altered forests. However, our understanding of the implications of restorative disturbances on stand dynamics has primarily been limited to shifts in species composition and post-disturbance regeneration. Therefore, we examined annual radial growth responses of dominant upland oaks following a combination of prescribed fires (2004, 2006, 2008, 2010, 2012, and 2014) and thinning (starting in 2004) treatments (thin+burn) in stands which had previously been unburned since the early 1900s. Radial stem growth rates were quantified using tree cores from 22 post oak (Q. stellata) and southern red oak (Q. falcata) in a 2.5-acre thin+burn and control stand at the Strawberry Plains Audubon Center in northern Mississippi. Radial growth rates were not significantly greater following repeated thinning and prescribed burning than prior to treatment initiation for either post oak or southern red oak. For the first 6 years after the initial thin, the annual ring width for southern red oak was identical in the thin+burn (1.9 ± 0.1 mm year-1) and control (2.0 ± 0.2 mm year-1) stands. However, in 2010 radial growth for southern red oak in the thin+burn increased such that the annual ring width for 2010 was 22 percent greater in the thin+burn than in the control stands. In contrast to the positive growth response in southern red oak (2 percent), post oak demonstrated a significantly different (p = 0.014) negative response (-19 percent) in the relative percent change in total radial growth for the 11-year period post-treatment initiation when compared to the 11-year period prior to treatment initiation. Radial growth for both species was negatively impacted by a severe drought in 2007 with southern red oak exhibiting the greatest decrease in radial growth. Results from this study highlight the underlying role of climatic factors and species life history characteristics in evaluating radial growth patterns following forest disturbances

The Determined Will

A dialogue in which Freya nan Max are determined to argue abut free will

Mapping of Forest Alliances and Associations Using Fuzzy Systems and Nearest Neighbor Classifiers

The study and management of biological communities depends on systems of classification and mapping for the organization and communication of resource information. Recent advances in remote sensing technology may enable the mapping forest plant associations using image classification techniques. But few areas outside Europe have alliances and associations described in detail sufficient to support remote sensing-based modeling. Northwestern Montana has one of the few plant association treatments in the United States compliant with the recently established National Vegetation Classification system. This project examined the feasibility of mapping forest plant associations using Landsat Enhanced Thematic Mapper data and advanced remote sensing technology and image classification techniques. Suitable reference data were selected from an extensive regional database of plot records. Fifteen percent of the plot samples were reserved for validation of map products, the remainder of plots designated as training data for map modeling. Key differentia for image classification were identified from a suite of spectral and biophysical variables. Fuzzy rules were formulated for partitioning physiognomic classes in the upper levels of our image classification hierarchy. Nearest neighbor classifiers were developed for classification of lower levels, the alliances and associations, where spectral and biophysical contrasts are less distinct. Maps were produced to reflect nine forest alliances and 24 associations across the study area. Error matrices were constructed for each map based on stratified random selections of map validation samples. Accuracy for the alliance map was estimated at 60%. Association classifiers provide between 54 and 86% accuracy within their respective alliances. Alternative techniques are proposed for aggregating classes and enhancing decision tree classifiers to model alliances and associations for interior forest types

Air/surface exchange of gaseous elemental mercury at different landscapes in Mississippi, USA

© 2019 by the authors. Mercury (Hg) is a global pollutant with human health and ecological impacts. Gas exchange between terrestrial surfaces and the atmosphere is an important route for Hg to enter and exit ecosystems. Here, we used a dynamic flux chamber to measure gaseous elemental Hg (GEM) exchange over different landscapes in Mississippi, including in situ measurements for a wetland (soil and water), forest floor, pond, mowed field and grass-covered lawn, as well as mesocosm experiments for three different agricultural soils. Fluxes were measured during both the summer and winter. Mean ambient levels of GEM ranged between 0.93-1.57 ng m-3. GEM emission fluxes varied diurnally with higher daytime fluxes, driven primarily by solar radiation, and lower and more stable nighttime fluxes, dependent mostly on temperature. GEM fluxes (ng m-2 h-1) were seasonally dependent with net emission during the summer (mean 2.15, range 0.32 to 4.92) and net deposition during the winter (-0.12, range -0.32 to 0.12). Total Hg concentrations in the soil ranged from 17.1 ng g-1 to 127 ng g-1 but were not a good predictor of GEM emissions. GEM flux and soil temperature were correlated over the forest floor, and the corresponding activation energy for Hg emission was ~31 kcal mol-1 using the Arrhenius equation. There were significant differences in GEM fluxes between the habitats with emissions for grass \u3e wetland soil \u3e mowed field \u3e pond \u3e wetland water ≈ forest ≈ agriculture soils. Overall, we demonstrate that these diverse landscapes serve as both sources and sinks for airborne Hg depending on the season and meteorological factors

Tree thinning and fire affect ectomycorrhizal fungal communities and enzyme activities

Common ecological restoration treatments such as thinning trees and prescribed burning could result in changes to soil fungal communities and changes to the function of those communities. Ectomycorrhizal fungi are especially likely to be affected as they are symbionts on plant roots and exhibit host and niche preferences. Ectomycorrhizal fungi also produce extracellular enzymes that are important in soil nutrient cycling. We conducted a community survey of ectomycorrhizal fungi and assayed ectomycorrhizal root tip enzyme activity using substrate plugs in northern Mississippi upland oak–pine woodland plots differing in restoration history to explore the influence of woodland restoration on ectomycorrhizalfungal community composition and function. Restoration treatment was significant in explaining the occurrence of the most common fungal species (Russula xerampelina) and the most common family (Thelephoraceae) in the ectomycorrhizal fungal community survey. Highest potential laccase, peroxidase, and N-acetyl-b-D-glucosaminidase enzyme activity were found in a prescribed burn plot, and the lowest enzyme activities at a wildfire plot, where richness of ectomycorrhizal fungi was also lower. Different fungal families displayed significantly different enzymatic capabilities, with Hydnangiaceae having the highest laccase activity and Tuberaceae having significantly higher peroxidase and chitinase activity than several other families. These results suggest that restoration treatments can affect ectomycorrhizal fungal community composition and function, and better understanding these changes can aid understanding of the niches of ectomycorrhizal fungi and the impacts of restoration

Effects of Pramipexole on Impulsive Choice in Male Wistar Rats

This article may not exactly replicate the final version published in the APA journal. It is not the copy of record.Clinical reports, primarily with Parkinson’s patients, note an association between the prescribed use of pramipexole (and other direct-acting dopamine agonist medications) and impulse control disorders, particularly pathological gambling. Two experiments examined the effects of acute pramipexole on rats’ impulsive choices where impulsivity was defined as selecting a smaller-sooner over a larger-later food reward. In Experiment 1, pramipexole (0.1 to 0.3 mg/kg) significantly increased impulsive choices in a condition in which few impulsive choices were made during a stable baseline. In a control condition, in which impulsive choices predominated during baseline, pramipexole did not significantly change the same rats’ choices. Experiment 2 explored a wider range of doses (0.01 to 0.3 mg/kg) using a choice procedure in which delays to the larger-later reinforcer delivery increased across trial blocks within each session. At the doses used in Experiment 1, pramipexole shifted choice toward indifference regardless of the operative delay. At lower doses of pramipexole (0.01 & 0.03 mg/kg), a trend toward more impulsive choice was observed at the 0.03 mg/kg dose. The difference in outcomes across experiments may be due to the more complex discriminations required in Experiment 2; i.e., multiple discriminations between changing delays within each session

Lessons Learned from the Design, Certification, and Operation of the Space Shuttle Integrated Main Propulsion System (IMPS)

The Space Shuttle Integrated Main Propulsion System (IMPS) consists of the External Tank (ET), Orbiter Main Propulsion System (MPS), and Space Shuttle Main Engines (SSMEs). The IMPS is tasked with the storage, conditioning, distribution, and combustion of cryogenic liquid hydrogen (LH2) and liquid oxygen (LO2) propellants to provide first and second stage thrust for achieving orbital velocity. The design, certification, and operation of the associated IMPS hardware have produced many lessons learned over the course of the Space Shuttle Program (SSP). A subset of these items will be discussed in this paper for consideration when designing, building, and operating future spacecraft propulsion systems. This paper will focus on lessons learned related to Orbiter MPS and is the first of a planned series to address the subject matter