@article{starrett_blazich_shafer_grand_2001, title={In vitro colonization of micropropagated Pieris floribunda by ericoid mycorrhizae. II. Effects on acclimatization and growth}, volume={36}, number={2}, journal={HortScience}, author={Starrett, M. C. and Blazich, F. A. and Shafer, S. R. and Grand, L. F.}, year={2001}, pages={357–359} }
 @article{starrett_blazich_shafer_grand_2001, title={In vitro colonization of micropropagated Pieris floribunda byericoid mycorrhizae. I. Establishment of mycorrhizae onmicroshoots}, volume={36}, number={2}, journal={HortScience}, author={Starrett, M. C. and Blazich, F. A. and Shafer, S. R. and Grand, L. F.}, year={2001}, pages={353–356} }
 @article{hess_campbell_fiscus_hellkamp_mcquaid_munster_peck_shafer_2000, title={A conceptual model and indicators for assessing the ecological condition of agricultural lands}, volume={29}, ISSN={["0047-2425"]}, DOI={10.2134/jeq2000.00472425002900030007x}, abstractNote={As part of an environmental monitoring and assessment effort, we developed a conceptual model for measuring and assessing the condition and sustainability of agroecosystems. An agroecosystem is a field, pasture, or orchard and the associated border areas. We focused on ecological sustainability and defined the goals for agroecosystems in terms of the values people place on them. The purpose of an agroecosystem is to produce food and fiber. Other desired outcomes can be considered as goals for the larger landscape and the rest of the world, and they sometimes function as constraints on production. Condition is defined by agroecosystem productivity and the degree to which farmers use management and stewardship practices that conserve and protect valued natural resources in the landscape and the rest of the world. An agroecosystem in good condition is productive and is managed to conserve valued resources. Sustainability is the maintenance of good condition over time. We developed indicators that link system condition and sustainability to societal values and goals. These indicators measure productivity, management practices that promote sustainability at the agroecosystem scale, and management practices that promote sustainability at landscape and global scales. Our initial efforts focused on annually harvested herbaceous crops; however, the concepts we used can be adapted to other plant and livestock systems. Our conceptual approach may be used to evaluate the effectiveness of several major programs now being implemented, including the USDA's Environmental Quality Incentive and Conservation Reserve Programs.}, number={3}, journal={JOURNAL OF ENVIRONMENTAL QUALITY}, author={Hess, GR and Campbell, CL and Fiscus, DA and Hellkamp, AS and McQuaid, BF and Munster, MJ and Peck, SL and Shafer, SR}, year={2000}, pages={728–737} }
 @article{hellkamp_bay_campbell_easterling_fiscus_hess_mcquaid_munster_olson_peck_et al._2000, title={Assessment of the condition of agricultural lands in six mid-Atlantic states}, volume={29}, ISSN={["0047-2425"]}, DOI={10.2134/jeq2000.00472425002900030015x}, abstractNote={Indicators of the condition and sustainability of agricultural lands in five mid-Atlantic states were measured in 1994. Indicators were selected to reflect crop productivity and land stewardship on annually harvested herbaceous crop (AHHC) land, which covers almost 10% of the land area in this region. Overall, condition of agricultural lands in the region is good. Crops generally yielded more than those grown in the 1980s, with a mean observed/expected yield index greater than 1. The mean soil quality index was slightly better than a “moderate” rating for crop growth. Almost 2/3 of the AHHC land is covered by crop rotation plans, with the remaining land mostly in hay fields. Insecticides were applied to less than 20% of AHHC land, and less than 20% of the land where pesticides were applied has high to moderately high potential for pesticides leaching into groundwater. However, integrated pest management (IPM) is practiced on less than 20% of AHHC land. Hay showed more efficient use of nitrogen than seed crops, and non-tilled sites, which are mostly hay, had more microbial biomass (suggesting more nutrient cycling) than tilled sites. This information could provide a baseline for a long-term monitoring program for agroecosystems in the region.}, number={3}, journal={JOURNAL OF ENVIRONMENTAL QUALITY}, author={Hellkamp, AS and Bay, JM and Campbell, CL and Easterling, KN and Fiscus, DA and Hess, GR and McQuaid, BF and Munster, MJ and Olson, GL and Peck, SL and et al.}, year={2000}, pages={795–804} }
 @article{booker_shafer_wei_horton_2000, title={Carbon dioxide enrichment and nitrogen fertilization effects on cotton (Gossypium hirsutum L.) plant residue chemistry and decomposition}, volume={220}, ISSN={["0032-079X"]}, DOI={10.1023/A:1004773404948}, number={1-2}, journal={PLANT AND SOIL}, author={Booker, FL and Shafer, SR and Wei, CM and Horton, SJ}, year={2000}, pages={89–98} }
 @article{blum_staman_flint_shafer_2000, title={Induction and/or selection of phenolic acid-utilizing bulk-soil and rhizosphere bacteria and their influence on phenolic acid phytotoxicity}, volume={26}, ISSN={["0098-0331"]}, DOI={10.1023/A:1005560214222}, number={9}, journal={JOURNAL OF CHEMICAL ECOLOGY}, author={Blum, U and Staman, KL and Flint, LJ and Shafer, SR}, year={2000}, month={Sep}, pages={2059–2078} }
 @article{blum_shafer_lehman_1999, title={Evidence for inhibitory allelopathic interactions involving phenolic acids in field soils: Concepts vs. an experimental model}, volume={18}, DOI={10.1080/07352689991309441}, abstractNote={The accepted criteria for identifying allelopathic interactions in the field that have been proposed in the literature offer heuristic function, but to date have failed as a framework for research and diagnostics. If the present criteria are to be modified to make them useful empirically, their shortcomings must be identified. For this review, data from the literature and from defined model systems consisting of plants, soil, and/or microbes are used to evaluate the applicability of the accepted criteria to defined systems in which plants are responding to known allelochemicals. Based on this evaluation, modified criteria are proposed. In many respects, however, the modified criteria are as difficult to satisfy in the field as those proposed previously. The new criteria have value as a research framework because they clearly suggest that a shift in research focus to the soil environment, specifically the barrier of the rhizosphere through which allelochemicals must pass, is essential if the role of allelopathic interactions in the field is to be established.}, number={5}, journal={Critical Reviews in Plant Sciences}, author={Blum, Udo and Shafer, S. R. and Lehman, M. E.}, year={1999}, pages={673–693} }
 @inbook{blum_austin_shafer_1999, title={The fates and effects of phenolic acids in a plant-microbe-soil model system}, ISBN={8477865051}, booktitle={Recent advances in allelopathy:  I. A. science for the future}, publisher={Cadiz, Spain: Servicio de Publicaciones, Universidad de Cadiz}, author={Blum, U. and Austin, M. F. and Shafer, S. R.}, editor={F. A. Macias, J. G. C. Galindo and Molinillo, J. M. G. and Cutler, H.Editors}, year={1999}, pages={159–166} }
 @article{hellkamp_shafer_campbell_bay_fiscus_hess_mcquaid_munster_olson_peck_et al._1998, title={Assessment of the condition of agricultural lands in five mid-Atlantic states}, volume={51}, ISSN={["0167-6369"]}, DOI={10.1023/A:1005955807061}, number={1-2}, journal={ENVIRONMENTAL MONITORING AND ASSESSMENT}, author={Hellkamp, AS and Shafer, SR and Campbell, CL and Bay, JM and Fiscus, DA and Hess, GR and McQuaid, BF and Munster, MJ and Olson, GL and Peck, SL and et al.}, year={1998}, month={Jun}, pages={317–324} }
 @article{shafer_blum_horton_hesterberg_1998, title={Biomass of tomato seedlings exposed to an allelopathic phenolic acid and enriched atmospheric carbon dioxide}, volume={106}, ISSN={["0049-6979"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0032145076&partnerID=MN8TOARS}, DOI={10.1023/A:1004944731826}, number={1-2}, journal={WATER AIR AND SOIL POLLUTION}, author={Shafer, SR and Blum, U and Horton, SJ and Hesterberg, DL}, year={1998}, month={Aug}, pages={123–136} }
 @article{miller_shafer_schoeneberger_pursley_horton_davey_1997, title={Influence of a mycorrhizal fungus and/or rhizobium on growth and biomass partitioning of subterranean clover exposed to ozone}, volume={96}, ISSN={["0049-6979"]}, DOI={10.1023/A:1026496420809}, number={1-4}, journal={WATER AIR AND SOIL POLLUTION}, author={Miller, JE and Shafer, SR and Schoeneberger, MM and Pursley, WA and Horton, SJ and Davey, CB}, year={1997}, month={May}, pages={233–248} }
 @article{shafer_reinert_eason_spruill_1993, title={ANALYSIS OF OZONE CONCENTRATION - BIOMASS RESPONSE RELATIONSHIPS AMONG OPEN-POLLINATED FAMILIES OF LOBLOLLY-PINE}, volume={23}, ISSN={["1208-6037"]}, DOI={10.1139/x93-092}, abstractNote={Tropospheric ozone may contribute to the reported growth decline of pines in the southeastern United States. Ozone concentration–response relationships were quantified for open-pollinated families of loblolly pine (Pinustaeda L.) seedlings. Seedlings from 30 families were exposed to ozone (0, 80, 160, 240, or 320 nL O 3 /L air) in greenhouse chambers for 6 h per day, 4 days per week, for 12 weeks. Top (shoot) and root biomass were determined for each of 900 plants. Twelve families were selected for a subsequent experiment to examine consistency of results (360 plants). For each response variable, statistical models consisting of fixed and random effects were based on combined data for all families and both experiments. Data were fit to both polynomial and Weibull model types. The maximum suppression of any biomass variable (top, root, or total dry weight) predicted by a regression model for plants exposed for 12 weeks to 320 nL/L was 25% for total dry weight (Weibull model based on data representing all 42 family–year combinations, total of 1260 plants). Families were ranked for sensitivity based on estimates of a single parameter from the models, and model type had no effect on the order of sensitivity rankings of the 42 family–experiment combinations. The same families represented the extremes in sensitivity among the 12 families that were exposed in both experiments.}, number={4}, journal={CANADIAN JOURNAL OF FOREST RESEARCH}, author={SHAFER, SR and REINERT, RA and EASON, G and SPRUILL, SE}, year={1993}, month={Apr}, pages={706–715} }
 @article{shafer_koenning_barker_1992, title={INTERACTIONS OF SIMULATED ACIDIC RAIN WITH ROOT-KNOT OR CYST NEMATODES ON SOYBEAN}, volume={82}, ISSN={["0031-949X"]}, DOI={10.1094/Phyto-82-962}, abstractNote={The influence of simulated acidic rain on interactions of root-knot (Meloidogyne hapla, M. incognita) or cyst (Heterodera glycines) nematodes with soybean plants (Glycine max) was investigated in greenhouse experiments. Seedlings inoculated with rhizobia were transplanted into pots of nematode egg-infested soil (one nematode species per pot) or noninfested soil. Three days later, plants and soil were exposed to simulated rain (2 cm in 1 h) adjusted to pH 5.3, 4.3, 3.3, or 2.3 (...)}, number={9}, journal={PHYTOPATHOLOGY}, author={SHAFER, SR and KOENNING, SR and BARKER, KR}, year={1992}, month={Sep}, pages={962–970} }
 @article{shafer_1992, title={RESPONSES OF MICROBIAL-POPULATIONS IN THE RHIZOSPHERE TO DEPOSITION OF SIMULATED ACIDIC RAIN ONTO FOLIAGE AND OR SOIL}, volume={76}, ISSN={["0269-7491"]}, DOI={10.1016/0269-7491(92)90146-2}, abstractNote={Air pollutants or some chemicals applied to plant foliage can alter the ecology of the rhizosphere. Experiments were conducted to distinguish among possible foliage-mediated versus soil- or root-mediated effects of acid deposition on microorganism in the rhizosphere. Seedlings of a sorghum × sudangrass hybrid in pots of non-sterile soil-sand mix in a greenhouse were exposed to simulated rain solution adjusted with H2SO4 + HNO3 to pH 4·9, 4·2, 3·5 or 2·8. Solutions were applied as simulated rain to foliage and soil, foliage only (soil covered by plastic, and deionized water applied directly to the soil), or soil only (solution applied directly to the soil). Solutions were applied on 16 days during a 6-week period (1·5 cm deposition in 1 h per application). Plant shoot and root dry weights and population densities of selected types of bacteria, filamentous actinomycetes and fungi in the rhizosphere were quantified after exposures were completed. Deposition of simulated acidic rain onto foliage alone had no effect on plant biomass or microbial population densities in the rhizosphere (colony-forming units per gram of rhizosphere soil). However, plant growth was stimulated and all microbial populations in the rhizosphere increased 3- to 8-fold with increased solution acidity (relative to pH 4·9 solution) when solution penetrated the soil. Statistical analyses indicated that the acid dose-population response relationships for soil-only and foliage-and-soil applications were not different. Thus, no foliage-mediated effect of simulated acidic rain on rhizosphere ecology was detected.}, number={3}, journal={ENVIRONMENTAL POLLUTION}, author={SHAFER, SR}, year={1992}, pages={267–278} }
 @article{bruck_shafer_1991, title={A role for plant pathologists in global climate change research}, volume={75}, number={5}, journal={Plant Disease}, author={Bruck, R. I. and Shafer, S. R.}, year={1991}, pages={437} }
 @article{shafer_blum_1991, title={INFLUENCE OF PHENOLIC-ACIDS ON MICROBIAL-POPULATIONS IN THE RHIZOSPHERE OF CUCUMBER}, volume={17}, ISSN={["0098-0331"]}, DOI={10.1007/BF00994339}, number={2}, journal={JOURNAL OF CHEMICAL ECOLOGY}, author={SHAFER, SR and BLUM, U}, year={1991}, month={Feb}, pages={369–389} }
 @article{shafer_schoeneberger_1991, title={MYCORRHIZAL MEDIATION OF PLANT-RESPONSE TO ATMOSPHERIC CHANGE - AIR-QUALITY CONCEPTS AND RESEARCH CONSIDERATIONS}, volume={73}, ISSN={["0269-7491"]}, DOI={10.1016/0269-7491(91)90048-2}, abstractNote={The term 'global climate change' encompasses many physical and chemical changes in the atmosphere that have been induced by anthropogenic pollutants. Increases in concentrations of CO2 and CH4 enhance the 'greenhouse effect' of the atmosphere and may contribute to changes in temperature and precipitation patterns at the earth's surface. Nitrogen oxides and SO2 are phytotoxic and also react with other pollutants to produce other phytotoxins in the troposphere such as O3 and acidic substances. However, release of chlorofluorocarbons into the atmosphere may cause depletion of stratospheric O3, increasing the transmittance of ultraviolet-B (UV-B) radiation to the earth's surface. Increased intensities of UV-B could affect plants and enhance photochemical reactions that generate some phytotoxic pollutants. The role of mycorrhizae in plant responses to such stresses has received little attention. Although plans for several research programs have acknowledged the importance of drought tolerance and soil fertility in plant responses to atmospheric stresses, mycorrhizae are rarely targeted to receive specific investigation. Most vascular land plants form mycorrhizae, so the role of mycorrhizae in mediating plant responses to atmospheric change may be an important consideration in predicting effects of atmospheric changes on plants in managed and natural ecosystems.}, number={3-4}, journal={ENVIRONMENTAL POLLUTION}, author={SHAFER, SR and SCHOENEBERGER, MM}, year={1991}, pages={163–177} }
 @article{shafer_heagle_1989, title={GROWTH-RESPONSES OF FIELD-GROWN LOBLOLLY-PINE TO CHRONIC DOSES OF OZONE DURING MULTIPLE GROWING SEASONS}, volume={19}, ISSN={["1208-6037"]}, DOI={10.1139/x89-126}, abstractNote={Dose–response relationships were developed for ozone and four full-sib families of Pinustaeda L. Seedlings were planted in field plots in open-top chambers near Raleigh, North Carolina, and exposed daily during three growing seasons (1985, 1986, and 1987) to ozone at concentrations from 0.022 to 0.092 μL/L of air (seasonal mean concentrations for the daily exposure period 08:00 to 20:00 eastern standard time). Plants were harvested on five dates during the study to quantify effects of ozone on growth. Ozone suppressed stem height, root collar diameter, total branch length, and (or) dry weights of above-ground parts of plants in three families, but response to ozone depended upon dose, family, and the plant part measured. One family exposed during 1985 and 1986 did not exhibit significant growth responses to ozone. The family that exhibited the greatest growth suppression in 1985 and 1986 was exposed during the 3rd year, and ozone continued to reduce growth. Suppression of root dry weight was observed after three seasons of exposure. Root collar diameter and dry weight of stem + branches (without needles) may be the most useful measurements of growth response in multiple-year experiments. Dose–response models predicted that ambient levels of ozone could reduce growth relative to the growth predicted for chronic exposure to half-ambient levels (charcoal-filtered air). For aboveground woody tissue, this suppression ranged from 0 to 19% among the four families after two seasons of exposure and was 13% for the most sensitive family after three seasons.}, number={7}, journal={CANADIAN JOURNAL OF FOREST RESEARCH}, author={SHAFER, SR and HEAGLE, AS}, year={1989}, month={Jul}, pages={821–831} }
 @article{shafer_grand_bruck_heagle_1985, title={FORMATION OF ECTOMYCORRHIZAE ON PINUS-TAEDA SEEDLINGS EXPOSED TO SIMULATED ACIDIC RAIN}, volume={15}, ISSN={["0045-5067"]}, DOI={10.1139/x85-012}, abstractNote={Effects of simulated acidic rain on formation of ectomycorrhizae were studied with Pinustaeda seedlings grown in plastic trays in a greenhouse. Trays of ectomycorrhizal seedlings were exposed 37 times over 16 weeks to simulated rains adjusted to pH 5.6, 4.0, 3.2, or 2.4. After exposures, mean percentages of short roots that were mycorrhizal (%M) were greatest (62.2%) for seedlings exposed to rains of pH 2.4. Values of %M exhibited a quadratic relationship with rain acidity (%M = 146.49 − 48.96 (rain pH) + 5.68 (rain pH) 2 ). Values of R/S (root/shoot ratio) were negatively correlated (P < 0.01) with %M. Responses of ecetomycorrhiza formation and associated shoot growth to acidity of simulated rains suggest that rains of intermediate acidity (pH 4.0 and 3.2) inhibited ectomycorrhiza formation, or that increased soil acidity or other factors induced by rains at pH 2.4 enhanced ectomycorrhiza formation.}, number={1}, journal={CANADIAN JOURNAL OF FOREST RESEARCH-REVUE CANADIENNE DE RECHERCHE FORESTIERE}, author={SHAFER, SR and GRAND, LF and BRUCK, RI and HEAGLE, AS}, year={1985}, pages={66–71} }
 @article{shafer_bruck_heagle_1985, title={INFLUENCE OF SIMULATED ACIDIC RAIN ON PHYTOPHTHORA-CINNAMOMI AND PHYTOPHTHORA ROOT-ROT OF BLUE LUPINE}, volume={75}, ISSN={["0031-949X"]}, DOI={10.1094/Phyto-75-996}, number={9}, journal={PHYTOPATHOLOGY}, author={SHAFER, SR and BRUCK, RI and HEAGLE, AS}, year={1985}, pages={996–1003} }
 @inbook{bruck_shafer_1983, title={Effects of acidic precipitation on air-borne, soil-borne pathogens and mycorrhizal symbionts of forest trees}, booktitle={Acid rain and forest resources}, publisher={Washington, DC: USDA}, author={Bruck, R. I. and Shafer, S. R.}, year={1983}, pages={91–109} }
 @inbook{bruck_shafer_1983, title={Effects of acidic precipitation on plant diseases}, booktitle={Effects of acidic deposition on terrestrial ecosystems}, publisher={Ann Arbor, MI: Ann Arbor Press}, author={Bruck, R. I. and Shafer, S. R.}, year={1983}, pages={19–32} }
 @inbook{bruck_heagle_shafer_1982, title={Effects of simulated acid precipitation on foliar and root diseases of forest trees}, booktitle={EPA Acidic Deposition Ecological Effects Research Peer Review}, author={Bruck, R. I. and Heagle, A. S. and Shafer, S. R.}, year={1982}, pages={67–76} }