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Ma Y.,Purdue University | Ma Y.,Purdue Climate Change Research Center | Filley T.R.,Purdue University | Filley T.R.,Purdue Climate Change Research Center | And 2 more authors.
Soil Biology and Biochemistry | Year: 2014

In this study, we examined the response of surface soils to increased leaf and wood litter input within adjacent successional forests recovering from agricultural disturbance at the Smithsonian Environmental Research Center (SERC), Maryland, USA. Previous studies at this site demonstrated an arrested development of O-horizon, even after 130 years of forest growth, and an annual loss of leaf litter in forests with the highest abundance of invasive earthworms. Biogeochemical indices of plant biopolymer dynamics, i.e. extractable lignin and substituted fatty acids (SFAs), were applied to soil physical fractions in order to assess the fate of 5 years of increased Tulip poplar (Liriodendron tulipifera L.) wood and leaf litter into O-horizon and mineral soil particles of purportedly different protection levels in this recovering forest system. Our results showed that in this continuously-disturbed recovering system the pattern of litter incorporation into soil varied with both litter type and forest age. For example, young successional forests, that also contained higher abundances of soil feeding endogeic earthworms, incorporated wood amendments deeper into soils and in a predominantly particulate organic matter (POM) form than older successional systems with predominantly litter and surface dwelling earthworms. Soil lignin concentration increased sharply with wood amendments in both forest stages, but young successional forests exhibited incorporation of fresher lignin into both POM and silt and clay (SC) fractions over 0-5cm and 5-10cm depths while old forests only increased in POM in the 0-5cm depth. We attribute these differences to the higher rates of physical mixing from soil feeding endogeic species and potentially lower fungal activity in young successional forests. However, despite nearly 2.5 times of background annual leaf litter input over 5 years, neither total C content nor SFA concentration in soil fractions increased, a phenomenon we attribute to full decomposition of leaf litter amendments. These results demonstrate how the chemical trajectory of soils and litter layers in recovering forests can be a function of both legacy and current disturbance. © 2013 Elsevier Ltd.

Ma Y.,Purdue University | Ma Y.,Purdue Climate Change Research Center | Filley T.R.,Purdue University | Filley T.R.,Purdue Climate Change Research Center | And 5 more authors.
Organic Geochemistry | Year: 2013

The chemistry and physical association of soil organic matter in the patchwork of successional forest stands in the eastern US is strongly controlled by past land use. Invasive earthworm activity in these same systems, however, may impart a chemical and physical disturbance exceeding that of land use legacy. We established eight plots within forests of the Smithsonian Environmental Research Center (SERC) (Edgewater, MD), to compare sites with no record of significant agricultural disturbance or earthworm activity and successional mixed hardwood forests recovering from past agriculture (60-132. yr) that contained both native and non-native earthworms. Soils (0-15. cm) were separated into physical fractions by size (microaggregates) and density (light and heavy particulate organic matter) and investigated for organic carbon (C) and nitrogen (N) partitioning. In addition, molecular composition was analyzed using FTIR spectroscopy and lignin phenol and substituted fatty acid (SFA) extraction.Even after 132yr of recovery, the successional forests were nearly devoid of Oa+e horizons; a condition we attribute to high activity of invasive earthworms. Additionally, soil organic carbon (SOC) concentration profiles, and 14C derived mean residence times indicated mixing of the surface soils and fresh input of carbon to 10cm, distinct from the undisturbed, mature sites. The proportion of microaggregated particulate organic matter (iPOM) and silt+clay (iSC) was significantly higher in successional than undisturbed forests, which we attribute to the combined influence of past agricultural land use and high earthworm activity. Among the successional sites, older forests exhibited a significant decrease in the proportion of C and N in iSC but an increase in their proportion in iPOM, suggesting selective incorporation of iPOM with earthworm activity over great periods of time. In addition, continual consumption and mixing activities of the earthworm population could also be a primary control of the higher concentration and less oxidized lignin phenols as well as a higher proportion of lignin phenols to SFA in all soil fractions in the successional sites. Using partial least squares (PLS) regression of FTIR spectra, we also demonstrated a strong correlation between soil C physical distribution (microaggregated vs. non-microaggregated) and chemical aspects of specific FTIR regions which confirmed our findings from the lignin and SFA and showed distinct chemical dominance among the different sites. Our results indicated that while past agricultural practice may have been the primary initial influence on C and N stock and soil physical distribution in the successional sites, the prolonged legacy and trajectory of recovery from the past land disturbance can be controlled by the nature of the invasive and native earthworm activity during afforestation. © 2013 Elsevier Ltd.

The project, funded by the Purdue Climate Change Research Center, is one of the first to use UAVs to explore the nocturnal boundary layer, a stable atmospheric layer that forms during nighttime hours when the ground is cooler than the air. While daytime airflow is mostly predictable and measurable, nighttime airflow is poorly understood and difficult to measure, said Richard Grant, professor of agronomy at Purdue. "Air essentially sloshes around at night," he said. "The movements are much slower than in the daytime. Things are much more stable at night and therefore harder to predict." Grant's team collaborated with researchers from the Max Planck Institute of Biogeochemistry and the Karlsruhe Institute of Technology to track the flow of carbon dioxide and methane gas through the atmosphere with the goal of measuring how air flows throughout the layer. Traditionally, soil-emitted gases have been measured in closed chambers placed over the soil or on towers so the teams' use of UAVs is a significant development. "One of our goals is to see if UAV measurements are a viable way to measure and track these gases," Grant said. He said that being able to measure soil emissions at night as well as during the day is important to understanding the full impact of agricultural practices, such as chemical application, on the environment. During the planning stages of the project, Grant emailed colleagues at Purdue's School of Aviation and Transportation Technology to describe the project and request their input. Evan Flatt, an incoming senior in aeronautical engineering technology, responded with his recommendations for a vehicle that would meet Grant's needs. Flatt customized an octocopter-style UAV – a vehicle with eight rotors to provide lift and forward motion – to carry gas sensors. He also programmed the researchers' flight plans into the control software and collaborated with other team members to make sure everyone stayed safe. Under the supervision of Flatt and other team members, the Purdue UAV and others provided by the international research teams made 12-minute flights each hour, using a variety of flight plans designed to minimize disruption of the atmosphere by the vehicle rotors. "It was a pretty amazing experience for an undergrad," Flatt said. "Everyone on the trip had different needs and goals for the project. I wanted to fly safely and the researchers needed to get their data points close together. Some needed one type of data and some needed another, so you had to compromise. It was a great trip and I was excited to be involved in such a novel approach to the research."

News Article | April 13, 2016
Site: phys.org

Researchers found that the overall protein concentration of goldenrod pollen fell about one-third from the onset of the Industrial Revolution to the beginning of the 21st century. Previous studies have shown that increases in carbon dioxide can lower the nutritional value of plants such as wheat and rice - staple crops for much of the global human population - but this study is the first to examine the effects of rising CO2 on the diet of bees. "Bee food is less nutritious than it used to be," said Jeffrey Dukes, study co-author and professor of forestry and natural resources and biological sciences. "Our findings also suggest that the quality of pollen will continue to decline into the future. That's not great news for bees." Native bee species and honeybees rely on flowering plants for energy and nutrition. While nectar is the primary energy source for bee colonies, pollen is the sole source of protein for bees. Pollen is essential for the development of bee larvae and helps maintain bees' immunity to pathogens and parasites. Goldenrod, a common North American perennial that blooms from late July through October, offers bees some of the last available pollen before winter. Bees that overwinter must store substantial amounts of pollen to rear their winter young. Declines in pollen protein could potentially threaten bee health and survival and weaken bees' ability to overwinter on a continental scale, said Jeffery Pettis, study co-author and research entomologist with the U.S. Department of Agriculture's Agricultural Research Service. "A poor diet sets bees up for failure," he said. "Previous research shows bees have shorter lifespans when fed lower quality pollen." The researchers noted, however, that this study only assessed pollen protein levels and did not look at the impact of protein reductions on bee health and populations. "Our work suggests there is a strong possibility that decreases in pollen protein could contribute to declines in bee health, but we haven't yet made that final link," said Dukes, who is also director of the Purdue Climate Change Research Center housed in Discovery Park. Dukes collaborated with a team led by USDA-ARS researchers to examine protein levels in historical and experimental samples of goldenrod pollen. They found that pollen protein levels dropped about a third in samples collected from 1842-2014, a period during which the amount of carbon dioxide in the Earth's atmosphere rose from about 280 parts per million to 398 ppm. The greatest drop in protein occurred during 1960-2014, a time when atmospheric carbon dioxide levels rose dramatically. A 2-year controlled field experiment that exposed goldenrod to a gradient of carbon dioxide levels from 280 to 500 ppm showed strikingly similar decreases in pollen protein, Dukes said. "These data provide an urgent and compelling case for establishing CO2 sensitivity of pollen protein for other floral species," the researchers concluded in their study. Bees provide a valuable service to U.S. agriculture through pollination, contributing more than $15 billion in added crop value each year. But a number of new and mounting pressures are crippling colonies and endangering bee populations. These threats include emerging diseases and parasites such as deformed wing virus, Varroa mites and Nosema fungi; a lack of diversity and availability of pollen and nectar sources; and exposure to a wide variety of pesticides. From 2006 to 2011, annual losses of managed honeybee colonies averaged about 33 percent per year, according to the USDA-ARS. "Bees already face a lot of factors that are making their lives hard," Dukes said. "A decline in the nutritional quality of their food source going into a critical season is another reason to be concerned." Elevated levels of atmospheric carbon dioxide - a building block for plant sugars -have allowed many plants to grow faster and bigger. But this growth spurt can dilute plants' total protein, rather than concentrating it in the grain, resulting in a less nutritious food source. Slowing the degrading effects of rising carbon dioxide levels on plant nutrition hinges on reducing carbon emission rates from deforestation and burning fossil fuels, Dukes said. "The impact of carbon emissions on the nutritional value of our food supply is something people need to be aware of. This issue isn't just relevant to honeybees and people - it will probably affect thousands or even millions of other plant-eating species around the world. We don't yet know how they'll deal with it." Explore further: Poor diet may contribute to the decline in British bees More information: Lewis H. Ziska et al. Rising atmospheric CO is reducing the protein concentration of a floral pollen source essential for North American bees , Proceedings of the Royal Society B: Biological Sciences (2016). DOI: 10.1098/rspb.2016.0414

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