Atmospheric Co2 And O3 Alter The Flow Of 15n In Developing Forest Ecosystems

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/116984/1/ecy200788102630.pd

Annual Reports

This section contains the annual reports of the Society’s president, William A. Sherman, the executive director, Wilbur T. Holmes, and the curator of manuscripts, Gladys E. Bolhouse

Initial test results on bolometers for the Planck high frequency instrument

We summarize the fabrication, flight qualification, and dark performance of bolometers completed at the Jet Propulsion Laboratory for the High Frequency Instrument (HFI) of the joint ESA/NASA Herschel/Planck mission to be launched in 2009. The HFI is a multicolor focal plane which consists of 52 bolometers operated at 100 mK. Each bolometer is mounted to a feedhorn-filter assembly which defines one of six frequency bands centered between 100-857 GHz. Four detectors in each of five bands from 143-857 GHz are coupled to both linear polarizations and thus measure the total intensity. In addition, eight detectors in each of four bands (100, 143, 217, and 353 GHz) couple only to a single linear polarization and thus provide measurements of the Stokes parameters, Q and U, as well as the total intensity. The measured noise equivalent power (NEP) of all detectors is at or below the background limit for the telescope and time constants are a few ms, short enough to resolve point sources as the 5 to 9 arc min beams move across the sky at 1 rpm

Elevated atmospheric CO 2 , fine roots and the response of soil microorganisms: a review and hypothesis

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65243/1/j.1469-8137.2000.00687.x.pd

Plant Diversity, Soil Microbial Communities, And Ecosystem Function: Are There Any Links?

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/117152/1/ecy20038482042.pd

Simulated Atmospheric No3− Deposition Increases Soil Organic Matter By Slowing Decomposition

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/117243/1/eap20081882016.pd

Chemistry and decomposition of litter from Populus tremuloides Michaux grown at elevated atmospheric CO 2 and varying N availability

It has been hypothesized that greater production of total nonstructural carbohydrates (TNC) in foliage grown under elevated atmospheric carbon dioxide (CO 2 ) will result in higher concentrations of defensive compounds in tree leaf litter, possibly leading to reduced rates of decomposition and nutrient cycling in forest ecosystems of the future. To evaluate the effects of elevated atmospheric CO 2 on litter chemistry and decomposition, we performed a 111 day laboratory incubation with leaf litter of trembling aspen ( Populus tremuloides Michaux) produced at 36 Pa and 56 Pa CO 2 and two levels of soil nitrogen (N) availability. Decomposition was quantified as microbially respired CO 2 and dissolved organic carbon (DOC) in soil solution, and concentrations of nonstructural carbohydrates, N, carbon (C), and condensed tannins were monitored throughout the incubation. Growth under elevated atmospheric CO 2 did not significantly affect initial litter concentrations of TNC, N, or condensed tannins. Rates of decomposition, measured as both microbially respired CO 2 and DOC did not differ between litter produced under ambient and elevated CO 2 . Total C lost from the samples was 38 mg g −1 litter as respired CO 2 and 138 mg g −1 litter as DOC, suggesting short-term pulses of dissolved C in soil solution are important components of the terrestrial C cycle. We conclude that litter chemistry and decomposition in trembling aspen are minimally affected by growth under higher concentrations of CO 2 .Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75335/1/j.1365-2486.2001.00388.x.pd

Belowground competition and the response of developing forest communities to atmospheric CO 2 and O 3

As human activity continues to increase CO 2 and O 3 , broad expanses of north temperate forests will be simultaneously exposed to elevated concentrations of these trace gases. Although both CO 2 and O 3 are potent modifiers of plant growth, we do not understand the extent to which they alter competition for limiting soil nutrients, like nitrogen (N). We quantified the acquisition of soil N in two 8-year-old communities composed of trembling aspen genotypes ( n = 5) and trembling aspen–paper birch which were exposed to factorial combinations of CO 2 (ambient and 560 ΜL L −1 ) and O 3 (ambient = 30–40 vs. 50–60 nL L −1 ). Tracer amount of 15 NH 4 + were applied to soil to determine how these trace gases altered the competitive ability of genotypes and species to acquire soil N. One year after isotope addition, we assessed N acquisition by measuring the amount of 15 N tracer contained in the plant canopy (i.e. recent N acquisition), as well as the total amount of canopy N (i.e. cumulative N acquisition). Exposure to elevated CO 2 differentially altered recent and cumulative N acquisition among aspen genotypes, changing the rank order in which they obtained soil N. Elevated O 3 also altered the rank order in which aspen genotypes obtained soil N by eliciting increases, decreases and no response among genotypes. If aspen genotypes respond similarly under field conditions, then rising concentrations of CO 2 and O 3 could alter the structure of aspen populations. In the aspen–birch community, elevated CO 2 increased recent N (i.e. 15 N) acquisition in birch (68%) to a greater extent than aspen (19%), suggesting that, over the course of this experiment, birch had gained a competitive advantage over aspen. The response of genotypes and species to rising CO 2 and O 3 concentrations, and how these responses are modified by competitive interactions, has the potential to change the future composition and productivity of northern temperate forests.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72323/1/j.1365-2486.2007.01436.x.pd