The dynamic consequences of invasion: negative plant-soil feedbacks on natives increase ver the time course of invasion

*a) Background/Questions/Methods*
Exotic species can negatively impact native community members, directly through interference competition, or indirectly by altering interactions between native species and other species such as pathogens and mutualists. Soil microbial communities have been shown to respond to invasive species, yet are relatively stable and may take time to respond to perturbations. For this reason, microbe-mediated effects of invasives on natives may take time to develop and may change throughout the invasion process. Few studies have investigated how species interactions between natives and exotics change during invasions.

_Acer platanoides_ was introduced into the US from Europe in 1756 and has since invaded intact forests, lowering understory diversity and inhibiting native tree species regeneration. We hypothesize that _A. platanoides_ invasion will decrease seedling survival in the native _A. saccharum_ by changing the soil microbial community through plant-soil feedbacks (PSF), and this relationship will intensify over the course of an invasion. We collected soil samples from beneath the canopies of both species co-occurring in Michigan forests that had been invaded by _A. platanoides_ for varying time periods. In the greenhouse, we inoculated seedlings of both species with the microbial communities to determine how the soil community affects seedling survival and growth.

*b) Results/Conclusion*
The microbe-mediated negative effects of _A. platanoides_ on survival of the native congener _A. saccharum_ increased with increasing invasion age (negative correlation between invasion age and _A. saccharum_ survival; r = -0.806, R^2^ = 0.65, p = 0.032). This result was not related to _A. platanoides_ density, suggesting that age of invasion drives this pattern. Contrastingly, invasion age did not significantly influence survival of _A. platanoides_ seedlings, indicating that _A. platanoides’_ PSF impacts native species but not on conspecific regeneration. Overall, _A. platanoides_ seedlings had increased growth (more and larger leaves) when grown in soil communities collected from the native _A. saccharum_, but _A. saccharum_ seedlings had reduced growth when grown in conspecific soil (p = 0.044). These results suggest that invasive species may have increased performance in exotic ranges by their ability to modify the soil microbial community in a manner that suppresses the growth of native species.

We show the microbial community cultivated by an invader alters the performance of a native plant species, and this effect increases over the course of an invasion. In future work, we plan to identify changes in microbial community composition and the relative abundances of mutualists versus antagonists in response to invasion to identify potential mechanisms

Septic tank/absorption field systems : a homeowner's guide to installation and maintenance (2001)

A septic tank/absorption field is the most common onsite sewage treatment system in use in Missouri. Nearly 30 percent of all housing units in Missouri use onsite wastewater treatment systems and most of these are septic tank/absorption field systems. Several surveys throughout the state have shown that 70 percent, or 150,000, of these systems are not functioning properly.Revised 10/01/7

Residential sewage lagoon systems: a homeowner’s guide to installation and maintenance

Revised 6/97/6M"Residential waste stabilization lagoons are commonly used for onsite sewage treatment in Missouri in low-population areas where soils are not suited for conventional absorption field systems. An estimated 30 percent of all housing units in Missouri use onsite wastewater treatment systems. Several surveys throughout the state have shown that 70 percent, or 150,000, of these systems are not functioning properly. Counties in the Missouri Ozarks are particularly at risk. Human contact with sewage is a serious public health risk. Drinking water contaminated with sewage can cause health problems such as diarrhea, nausea, cramps, dysentery and hepatitis. Exposure to sewer gases can also cause discomfort and illness."--Page 1.Robert A. Schultheis, Extension Agricultural Engineering Specialist, University of MissouriIncludes bibliographical reference

The Effective temperature scale of M dwarfs from spectral synthesis

We present a comparison of low-resolution spectra of 60 stars covering the whole M-dwarf sequence. Using the most recent PHOENIX BT-Settl stellar model atmospheres (see paper by F. Allard, in this book) we do a first quantitative compari- son to our observed spectra in the wavelength range 550-950 nm. We perform a first confrontation between models and observations and we assign an effective tempera- tures to the observed M-dwarfs. Teff-spectral type relations are then compared with the published ones. This comparison also aims at improving the models' opacities.Comment: To be published in the on-line version of the Proceedings of Cool Stars 16 (ASP Conference Series) New version with bibliography correcte

Residential sewage lagoon systems : a homeowner's guide to installation and maintenance (1997)

"Revised 6/97/6M.""Water Quality.""Focus area : nutrients and bacterial wastes.""Published by University Extension, University of Missouri-System.

Accretion by the Galaxy

Cosmology requires at least half of the baryons in the Universe to be in the intergalactic medium, much of which is believed to form hot coronae around galaxies. Star-forming galaxies must be accreting from their coronae. HI observations of external galaxies show that they have HI halos associated with star formation. These halos are naturally modelled as ensembles of clouds driven up by supernova bubbles. These models can fit the data successfully only if clouds exchange mass and momentum with the corona. As a cloud orbits, it is ablated and forms a turbulent wake where cold high-metallicity gas mixes with hot coronal gas causing the prompt cooling of the latter. As a consequence the total mass of HI increases. This model has recently been used to model the Leiden-Argentina-Bonn survey of Galactic HI. The values of the model's parameters that are required to model NGC 891, NGC 2403 and our Galaxy show a remarkable degree of consistency, despite the very different natures of the two external galaxies and the dramatic difference in the nature of the data for our Galaxy and the external galaxies. The parameter values are also consistent with hydrodynamical simulations of the ablation of individual clouds. The model predicts that a galaxy that loses its cool-gas disc for instance through a major merger cannot reform it from its corona; it can return to steady star formation only if it can capture a large body of cool gas, for example by accreting a gas-rich dwarf. Thus the model explains how major mergers can make galaxies "red and dead."Comment: Invited review at "Assembling the Puzzle of the Milky Way", Grand Bornand, April 2011; 6 page

The Galactic bulge as seen in optical surveys

The bulge is a region of the Galaxy of tremendous interest for understanding galaxy formation. However measuring photometry and kinematics in it raises several inherent issues, such as severe crowding and high extinction in the visible. Using the Besancon Galaxy model and a 3D extinction map, we estimate the stellar density as a function of longitude, latitude and apparent magnitude and we deduce the possibility of reaching and measuring bulge stars with Gaia. We also present an ongoing analysis of the bulge using the Canada-France-Hawaii Telescope.Comment: In SF2A-2008: Proceedings of the Annual meeting of the French Society of Astronomy and Astrophysic

Constraining the Milky Way potential using the dynamical kinematic substructures

We present a method to constrain the potential of the non-axisymmetric components of the Galaxy using the kinematics of stars in the solar neighborhood. The basic premise is that dynamical substructures in phase-space (i.e. due to the bar and/or spiral arms) are associated with families of periodic or irregular orbits, which may be easily identified in orbital frequency space. We use the "observed" positions and velocities of stars as initial conditions for orbital integrations in a variety of gravitational potentials. We then compute their characteristic frequencies, and study the structure present in the frequency maps. We find that the distribution of dynamical substructures in velocity- and frequency-space is best preserved when the integrations are performed in the "true" gravitational potential.Comment: 2 pages, 4 figures, to appear in the proceedings of "Assembling the Puzzle of the Milky Way", Le Grand Bornand (Apr. 17-22, 2011

The visibility of the Galactic bulge in optical surveys. Application to the Gaia mission

The bulge is a region of the Galaxy which is of tremendous interest for understanding Galaxy formation. However, measuring photometry and kinematics in it raises several inherent issues, like high extinction in the visible and severe crowding. Here we attempt to estimate the problem of the visibility of the bulge at optical wavelengths, where large CCD mosaics allow to easily cover wide regions from the ground, and where future astrometric missions are planned. Assuming the Besancon Galaxy model and high resolution extinction maps, we estimate the stellar density as a function of longitude, latitude and apparent magnitude and we deduce the possibility of reaching and measuring bulge stars. The method is applied to three Gaia instruments, the BBP and MBP photometers, and the RVS spectrograph. We conclude that, while in the BBP most of the bulge will be accessible, in the MBP there will be a small but significant number of regions where bulge stars will be detected and accurately measured in crowded fields. Assuming that the RVS spectra may be extracted in moderately crowded fields, the bulge will be accessible in most regions apart from the strongly absorbed inner plane regions, because of high extinction, and in low extinction windows like the Baades's window where the crowding is too severe.Comment: 11 pages, 9 figures, accepted for publication in A&A, latex using A&A macro