2012 Annual Report
1a.Objectives (from AD-416):
The long-term objectives of this project are to improve understanding of the effects of rising atmospheric carbon dioxide (CO2) concentration on: agricultural productivity; the role of agronomic management in the sequestration of atmospheric CO2 as organic C in soil; and the emission of greenhouse gases (GHG) from agro-ecosystems. Specifically, we will focus on: (1) determining the impacts of elevated atmospheric CO2 and fertilization on plant production, soil C and N dynamics (including C sequestration), soil physicochemical properties, and soil biological properties for adapting Southeastern pasture systems to conditions of changing climate; (2) evaluating the interacting effects of fertilization and elevated atmospheric CO2 on emissions of GHG from soils in Southeastern pasture systems to develop strategies for mitigating the net impact of pasture systems on climate change; and (3) determining the effects of elevated atmospheric CO2 on the establishment and spread of invasive weeds and endemic crop diseases to adapt control strategies to a changing environment.
1b.Approach (from AD-416):
A long-term Southeastern pasture system, using bahiagrass exposed to current and projected levels of atmospheric CO2 and either managed (N added) or unmanaged (no N), is on-going. Carbon flux to plants (biomass growth, allocation, and quality) and soil will be determined with supporting data on soil physicochemical properties. Emphasis will be given to measuring soil C and N dynamics and C storage, root growth, decomposition, water quality, microbial community structure, and GHG (CO2, N2O, and CH4) flux from soil. In addition, container studies examining invasive weeds and endemic plant diseases important to the southeastern U.S will be conducted under the same CO2 levels as the pasture study. Invasive work will occur in two phases: (1) herbicide trials with selected invasive weeds; and (2) herbicide trials with invasives in competition with crop plants. Herbicide efficacy, re-growth, biomass, and tissue quality will be determined at study termination. Disease work will focus on various types of pathogens, i.e., fungal, bacterial, and viral, as well as soil-borne and aerial. Plants will be grown and harvested as for the invasive weed research. Plants will be monitored for symptoms and signs of disease. In all cases, disease incidence (percent plants infected) and severity (proportion of each plant affected) will be assessed. Effects of CO2 on disease development will be assessed by monitoring time to symptom development, latent period (time to sporulation), sporulation (quantity of spores produced), and sporulation period. The effect of CO2 on agronomic systems is a critical, yet neglected, area of research. Integrating data from these studies will aid understanding of the effects of future levels of atmospheric CO2 on agronomic systems in regard to production, the ability to help mitigate global change via sequestration of C in soil, and management of invasive weeds and endemic plant diseases.
Global change research at the ARS-USDA National Soil Dynamics Laboratory (NSDL), at Auburn, AL, addresses the impacts of elevated carbon dioxide (CO2) under differing pasture management practices (nitrogen) on soil carbon storage. Pasture aboveground biomass data have been collected and analyzed; soil cores for root and soil carbon as well as lysimeter solution samples have been collected and are being processed.
ARS research has begun to address the impacts of elevated carbon dioxide on invasive weeds and plant diseases. A study on the effects of elevated atmospheric CO2 on two non-native ornamental plants, including the potential for these plants to become invasive problem species was completed. Sensitive and resistant lines (to glyphosate) of pigweed were grown under elevated and ambient atmospheric carbon dioxide; data have been collected and are currently being analyzed. A herbicide study with yellow and purple nutsedge grown under ambient and elevated carbon dioxide is nearing completion. Studies on the effects of atmospheric carbon dioxide concentration on plant diseases are in preparation.
ARS research is seeking to understand factors affecting trace gas (carbon dioxide, methane, and nitrous oxide) efflux from agricultural and horticultural systems. Carbon dioxide efflux from both a pasture and an outplanted ornamental horticultural system continues to be monitored (24 hours per day) using Automated Carbon Efflux Systems (ACES). Trace gas emissions are being assessed weekly in both systems. Gas samples are collected in situ using the static closed chamber method according to USDA’s Greenhouse Gas Reduction Through Agricultural Carbon Enhancement network (GRACEnet) protocols and analyzed using gas chromatography. In both studies, soil carbon data are also being collected to determine soil Carbon (C) sequestration potential.
Agriculture contributes to trace gas emissions. Much of the work on reducing greenhouse gas (GHG) emissions has focused on row crops and pastures, as well as forestry and animal production systems; however, little emphasis has been placed on specialty crop industries such as horticulture. Larger nursery containers had greater loss of both carbon dioxide (CO2) and nitrous oxide and loss was positively related to container size; methane loss was consistently low and had no significant effect on total trace gas loss. These results begin to address uncertainties regarding the environmental impact of the horticulture industry on climate change while providing baseline data of trace gas emissions from container production systems needed to develop future mitigation strategies.
Long-term effects of elevated carbon dioxide (CO2) on sour orange roots: Rising atmospheric CO2 concentration has positive effects on growth of most plants. However, most CO2 studies extend for short periods (months to a few years) and the long-term impacts are virtually unknown. Seventeen years of CO2 enrichment increased sour orange fine root length and weight, particularly in the upper 30 cm (12 in) of soil, but did not affect horizontal root distribution patterns. Elevated CO2 continues to have positive effects on plant root growth for many years. This will enable plants to more thoroughly explore the soil for water and nutrients which will increase their growth, yield, and overall health. This is important to the scientific community and to growers of long-lived plants (such as forest and tree crop producers).
The southeastern landscape is composed of agricultural and forest systems that can store carbon (C) in standing biomass and soil. Research is needed to quantify the effects of elevated atmospheric carbon dioxide (CO2) on terrestrial carbon dynamics including CO2 release back to the atmosphere and soil sequestration. Longleaf pine savannahs are an ecologically and economically important, yet understudied, component of the southeastern landscape. Our data indicate that, while elevated CO2 will increase feedback of CO2 to the atmosphere via loss from soil, terrestrial ecosystems will remain potential sinks for atmospheric CO2 due to greater biomass production and increased soil C sequestration. This information is important to scientists, climate modelers, and to growers interested in mitigating the rise in atmospheric CO2.
Elevated atmospheric CO2 effects invasive plants: the rising level of CO2 in the atmosphere causes most plants to grow larger; while this increases crop yield, it can also increase problems associated with non-native plants. Both Lantana and Vinca grew larger under elevated CO2; however, Lantana was much more responsive to elevated CO2 than was Vinca due to the fact that Lantana is a woody plant with a large root system. Lantana could become a problem invasive plant as atmospheric CO2 continues to rise, while Vinca likely will not. This information will make ornamental producers and people involved with invasive plants aware that non-native plants can become invasive problems as atmospheric CO2 continues to rise.
Marble, S.C., Fain, G.B., Gilliam, C.H., Runion, G.B., Prior, S.A., Torbert III, H.A., Wells, D. 2011. Landscape establishment of woody ornamentals grown in alternative wood-based container substrates. Journal of Environmental Horticulture. 30(1):13-16.
Runion, G.B., Butnor, J.R., Prior, S.A., Mitchell, R., Rogers, H.H. 2012. Effects of atmospheric CO2 enrichment on soil CO2 efflux in a young longleaf pine system. International Journal of Agronomy. vol. 2012, Article ID 549745, 9 pages, doi:10.1155/2012/549745.
Runion, G.B., Finegan, H., Prior, S.A., Rogers Jr, H.H., Gjerstad, D. 2011. Effects of elevated atmospheric CO2 on non-native plants: comparison of two important Southeastern ornamentals. Environment Control in Biology. 49(3):107-117.
Dos Santos, N., Prior, S.A., Gabardo, J., Valaski, J., Motta, A., Ferreira Neto, A. 2012. Influence of corn (Zea mays L.) cultivar development on residue production. Journal of Plant Nutrition. 35(5):750-769.
Marble, S.C., Prior, S.A., Runion, G.B., Torbert III, H.A., Gilliam, C.H., Fain, G.B., Sibley, J.L., Knight, P.R. 2012. Determining trace gas efflux from container production of woody nursery plants. Journal of Environmental Horticulture. 30(3):118-124..
Prior, S.A., Runion, G.B., Torbert III, H.A., Idso, S.B., Kimball, B.A. 2012. Sour orange fine root distribution after seventeen years of atmospheric CO2 enrichment. Agricultural and Forest Meteorology. 162-163:85-90.