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  • 1
    Language: English
    In: Nature, May 2018, Vol.557(7704), pp.141
    Description: Many scientific societies have codes of conduct that specifically prohibit harassment at meetings, and some, such as the American Astronomical Society and the Geological Society of America, address the professional treatment of others in their general codes of ethics. In a 2016 survey of physicists identifying...
    Keywords: Ethics ; Lab Life ; Research Management ; Research Personnel -- Legislation & Jurisprudence ; Scientific Misconduct -- Classification ; Sexual Harassment -- Legislation & Jurisprudence
    ISSN: 00280836
    E-ISSN: 1476-4687
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  • 2
    Language: English
    In: Soil Biology and Biochemistry, Feb, 2014, Vol.69, p.251(14)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.soilbio.2013.11.011 Byline: Nina T. Chaopricha, Erika Marin-Spiotta Abstract: Understanding the source of soil organic carbon (SOC) in deep soil horizons and the processes influencing its turnover is critical for predicting the response of this large reservoir of terrestrial C to environmental change and potential feedbacks to climate. Here, we propose that soil burial is a globally important but greatly underestimated process contributing to the delivery and long-term persistence of substantial SOC stocks to depths beyond those considered in most soil C inventories. We draw from examples in the paleosol and geomorphology literature to identify the effects of soil burial by volcanic, aeolian, alluvial, colluvial, glacial, and anthropogenic depositional processes on soil C storage. We describe how the state factors affecting soil formation affect the persistence and decomposition of SOC in buried soils. Organic horizons and surface mineral soils that become buried under layers of sediment can store C several meters below the earth's surface for millennia or longer. Buried SOC concentrations can rival those of surface soils, and soils buried under volcanic deposits generally contain higher concentrations of SOC than those under alluvial or non-permafrost loess deposits. The dearth of quantitative research on buried SOC specifically, and on deep C pools in general, makes it difficult to estimate the global importance of burial as a terrestrial C storage mechanism on contemporary time scales. The handful of studies that provide data on soil C stocks in buried horizons and estimate their spatial extent suggest that buried soils can contain significant regional OC reservoirs that are currently ignored in inventories and biogeochemical models. Recent research suggests that these buried SOC stocks may cycle biologically on annual-to-decadal time scales if the processes contributing to their protection from decomposition are altered. We discuss the vulnerability of buried SOC pools to disturbance from climate change and human activities that may reconnect these deep SOC pools with the atmosphere. We also provide recommendations on how burial processes can be incorporated into soil biogeochemical models to more accurately predict dynamics of deep SOC pools under different landscapes and environmental conditions. Author Affiliation: (a) Nelson Institute for Environmental Studies, University of Wisconsin-Madison, 550 North Park Street, Madison, WI 53706, USA (b) Department of Geography, University of Wisconsin-Madison, 550 North Park Street, Madison, WI 53706, USA Article History: Received 14 August 2013; Revised 16 October 2013; Accepted 13 November 2013
    Keywords: Reservoirs (Water) -- Analysis ; Burial -- Analysis ; Geomorphology -- Analysis ; Global Temperature Changes -- Analysis ; Loess -- Analysis ; Soil Carbon -- Analysis
    ISSN: 0038-0717
    Source: Cengage Learning, Inc.
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  • 3
    In: Global Change Biology, September 2015, Vol.21(9), pp.3532-3547
    Description: Soil microorganisms regulate fundamental biochemical processes in plant litter decomposition and soil organic matter () transformations. Understanding how microbial communities respond to changes in vegetation is critical for improving predictions of how land‐cover change affects belowground carbon storage and nutrient availability. We measured intra‐ and interannual variability in soil and forest litter microbial community composition and activity via phospholipid fatty acid analysis () and extracellular enzyme activity across a well‐replicated, long‐term chronosequence of secondary forests growing on abandoned pastures in the wet subtropical forest life zone of Puerto Rico. Microbial community structure differed between young secondary forests and older secondary and primary forests, following successional shifts in tree species composition. These successional patterns held across seasons, but the microbial groups driving these patterns differed over time. Microbial community composition from the forest litter differed greatly from those in the soil, but did not show the same successional trends. Extracellular enzyme activity did not differ with forest succession, but varied by season with greater rates of potential activity in the dry seasons. We found few robust significant relationships among microbial community parameters and soil , moisture, carbon, and nitrogen concentrations. Observed inter‐ and intrannual variability in microbial community structure and activity reveal the importance of a multiple, temporal sampling strategy when investigating microbial community dynamics with land‐use change. Successional control over microbial composition with forest recovery suggests strong links between above and belowground communities.
    Keywords: Extracellular Enzymes ; Forest Succession ; Land‐Use Change ; Litter ; Microbial Communities ; Plfa‐Fame ; Soil ; Tropics
    ISSN: 1354-1013
    E-ISSN: 1365-2486
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  • 4
    Language: English
    In: Forest Ecology and Management, 01 January 2015, Vol.335, pp.270-280
    Description: Tropical dry forests are subject to intense human pressure and land change, including conversion to agricultural crops, pasture or agroforestry, and urban encroachment. Decades, and even centuries, of conversion, expansion, regrowth, and changing land-use practices can result in a mosaic of secondary growth patches with different land-use histories. Whereas post-agricultural landscapes may appear as contiguous areas of forest regeneration, the successional trajectory of forest patches from historic land cover to their current state may differ substantially, with consequences for species composition and ecosystem structure and function. We examined the effect of different land-use histories on current forest structure, biomass, and composition in subtropical dry forests in St. Croix, U.S. Virgin Islands. We sampled three types of secondary forests that followed different regeneration pathways after centuries of sugarcane agriculture: 40-year old secondary forests that naturally regenerated after sugarcane abandonment, 40-year old secondary forests that were reforested with timber plantations before management ceased and they were overtaken by natural succession, and 10-year old secondary forests that were intensive pasture prior to recent forest regeneration. Secondary forests that naturally regenerated after sugarcane had similar structural characteristics, in terms of basal area, stem density, aboveground biomass, and species diversity compared to secondary forests of the same age that were former plantations. Species composition, however, remained distinct. Compositional differences between the two types of 40-year old secondary forests could be partially attributed to plantation species, specifically , whereas naturally regenerated forests were dominated by common secondary forest species, such as and . The effects of hurricane damage helped to explain structural similarity and compositional dissimilarity between naturally regenerated secondary forests and former plantations. Forest age had a significant effect on forest structure and composition. Differences between 10-year old and both types of 40-year old secondary forests were driven by a dominance of the nitrogen-fixing species , which rapidly established in 10-year old secondary forests and resulted in greater stem density and lower basal area, biomass, and species richness. Our results show that land-use history plays an important role in shaping species composition, especially in post-agricultural tropical dry forests. Although forests with differing land-use histories may structurally resemble one another within decades of abandonment, species composition may remain distinct for much longer. Understanding the legacy of human land use is important for dry forests that have a long history of disturbance and for predicting their response to future environmental change.
    Keywords: Tropical Dry Forest ; Secondary Forest ; Land Change ; Hurricane ; N-Fixing Species ; Novel Ecosystem ; Forestry ; Biology
    ISSN: 0378-1127
    E-ISSN: 1872-7042
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  • 5
    Language: English
    In: Soil Biology and Biochemistry, February 2014, Vol.69, pp.251-264
    Description: Understanding the source of soil organic carbon (SOC) in deep soil horizons and the processes influencing its turnover is critical for predicting the response of this large reservoir of terrestrial C to environmental change and potential feedbacks to climate. Here, we propose that soil burial is a globally important but greatly underestimated process contributing to the delivery and long-term persistence of substantial SOC stocks to depths beyond those considered in most soil C inventories. We draw from examples in the paleosol and geomorphology literature to identify the effects of soil burial by volcanic, aeolian, alluvial, colluvial, glacial, and anthropogenic depositional processes on soil C storage. We describe how the state factors affecting soil formation affect the persistence and decomposition of SOC in buried soils. Organic horizons and surface mineral soils that become buried under layers of sediment can store C several meters below the earth's surface for millennia or longer. Buried SOC concentrations can rival those of surface soils, and soils buried under volcanic deposits generally contain higher concentrations of SOC than those under alluvial or non-permafrost loess deposits. The dearth of quantitative research on buried SOC specifically, and on deep C pools in general, makes it difficult to estimate the global importance of burial as a terrestrial C storage mechanism on contemporary time scales. The handful of studies that provide data on soil C stocks in buried horizons and estimate their spatial extent suggest that buried soils can contain significant regional OC reservoirs that are currently ignored in inventories and biogeochemical models. Recent research suggests that these buried SOC stocks may cycle biologically on annual-to-decadal time scales if the processes contributing to their protection from decomposition are altered. We discuss the vulnerability of buried SOC pools to disturbance from climate change and human activities that may reconnect these deep SOC pools with the atmosphere. We also provide recommendations on how burial processes can be incorporated into soil biogeochemical models to more accurately predict dynamics of deep SOC pools under different landscapes and environmental conditions.
    Keywords: Soil Organic Carbon ; Paleosol ; Subsoil ; Deep Soil ; Soil Burial ; Deposition ; Erosion ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 6
    Language: English
    In: BioScience, 1 February 2014, Vol.64(2), pp.92-104
    Description: In the high-elevation humid tropics, human- and climate-driven land transitions can alter hydrologic connections between the atmosphere and surface waters, with local and downstream effects. We conducted a data synthesis to examine the influence of forest-to-grassland conversion, agroforest-to-nonforest conversion, tree plantation establishment on nonforest land, and recent glacier retreat on throughfall, evapotranspiration, runoff, and nitrate fluxes in montane Latin America (including the Caribbean) and Hawaii. Our synthesis reveals heterogeneous—sometimes unexpected—responses to land change. For example, in contrast with temperate highlands, forest-to-grassland conversion in the high-elevation tropics often results in little runoff increase and lower streamwater nitrate loss. Tree plantation establishment leads to diminished runoff; the magnitude of this effect is tenfold greater than with forest-to-grassland transitions. We highlight cases in which land use, land cover, and water relationships derived from temperate ecosystems do not apply to and, therefore, should not underpin watershed management programs in the high-elevation tropics.
    Keywords: Biology;
    ISSN: 00063568
    E-ISSN: 15253244
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  • 7
    In: Journal of Geophysical Research: Biogeosciences, September 2011, Vol.116(G3), pp.n/a-n/a
    Description: This study aimed to better understand the mechanisms for soil organic matter delivery to and accumulation in mineral horizons of tropical rain forest, volcanic soils. We used soil morphology, lysimetry, isotopes, and spectroscopy to investigate the role of preferential flow paths in the delivery of carbon (C) to the subsoil. High rainfall, high primary productivity, and the dominance of highly reactive, short‐range‐order minerals combine to sequester substantial stocks of soil C with long mean residence times. The soils have large peds, separated by wide cracks, which form a network of channels propagating downward through the top 40 to 60 cm, facilitating macropore flow. The channel infillings and crack surfaces were enriched in organic material (OM) with lower C:N ratios, and had higher ammonium oxalate‐extractable Al, and lower ammonium oxalate‐extractable Fe than the adjacent mineral bulk soil. CP MAS C‐NMR spectra of OM accumulating at depth showed strong signal intensities in the carboxyl and carbonyl C regions, indicative of organic acids, while decaying roots showed greater contributions of aromatic and O‐alkyl C. The ratios of alkyl‐to‐O‐alkyl C in the organic infillings were more similar to those of the bulk Bh and to dissolved organic matter than to those of decaying roots. Radiocarbon‐based ages of OM infillings at 〉50 cm depth were significantly younger than the mineral soil (2000 years versus 7000 years). Respired CO from incubated soils showed that OM accumulating at depth is a mixture of modern and much older C, providing further evidence for the downward movement of fresh C. Deep soil organic matter resembles recent surface organic horizon Preferential flowpaths facilitate downward transport of carbon Organic matter in flowpaths is different from bulk soil
    Keywords: Deep Soils ; Dissolved Organic Matter ; Soil Carbon ; Volcanic Soils
    ISSN: 0148-0227
    E-ISSN: 2156-2202
    E-ISSN: 21698961
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  • 8
    Language: English
    In: Plant and Soil, 2015, Vol.396(1), pp.1-26
    Description: BACKGROUND: Knowledge of biological and climatic controls in terrestrial nitrogen (N) cycling within and across ecosystems is central to understanding global patterns of key ecosystem processes. The ratios of ¹⁵N:¹⁴N in plants and soils have been used as indirect indices of N cycling parameters, yet our understanding of controls over N isotope ratios in plants and soils is still developing. SCOPE: In this review, we provide background on the main processes that affect plant and soil N isotope ratios. In a similar manner to partitioning the roles of state factors and interactive controls in determining ecosystem traits, we review N isotopes patterns in plants and soils across a number of proximal factors that influence ecosystem properties as well as mechanisms that affect these patterns. Lastly, some remaining questions that would improve our understanding of N isotopes in terrestrial ecosystems are highlighted. CONCLUSION: Compared to a decade ago, the global patterns of plant and soil N isotope ratios are more resolved. Additionally, we better understand how plant and soil N isotope ratios are affected by such factors as mycorrhizal fungi, climate, and microbial processing. A comprehensive understanding of the N cycle that ascribes different degrees of isotopic fractionation for each step under different conditions is closer to being realized, but a number of process-level questions still remain. ; p. 1-26.
    Keywords: Nitrogen ; Nitrogen isotopes ; Soil organic matter ; Plants ; Nutrient supplies ; Denitrification ; Decomposition
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 9
    In: Global Change Biology, June 2009, Vol.15(6), pp.1584-1597
    Description: Our research takes advantage of a historical trend in natural reforestation of abandoned tropical pastures to examine changes in soil carbon (C) during 80 years of secondary forest regrowth. We combined a chronosequence approach with differences in the natural abundance of C between C3 (forest) and C4 (pasture) plants to estimate turnover times of C in the bulk soil and in density fractions. Overall, gains in secondary forest C were compensated for by the loss of residual pasture‐derived soil C, resulting in no net change in bulk soil C stocks down to 1 m depth over the chronosequence. The free light fraction (LF), representing physically unprotected particulate organic matter, was most sensitive to land‐use change. Reforestation replenished C in the free LF that had been depleted during conversion to pastures. Turnover times varied with model choice, but in general, soil C cycling rates were rapid for the 0–10 cm depth, with even the heavy fraction (HF) containing C cycling in decadal time scales. Turnover times of C in the free LF from the 0–10 cm depth were shorter than for the occluded and HFs, highlighting the importance of physical location in the soil matrix for residence time in the soil. The majority of the soil C pool (82±21%) was recovered in the mineral‐associated density fraction. Carbon‐to‐nitrogen ratios and differences in natural abundance N of soil organic matter (SOM) showed an increasing degree of decomposition across density fractions with increasing mineral association. Our data show that the physical distribution of C in the soil has a large impact on soil C turnover and the ability of soils to maintain SOM stocks during land‐use and land‐cover change.
    Keywords: Carbon‐13 ; Density Fractionation ; Nitrogen‐15 ; Puerto Rico ; Secondary Forests ; Succession
    ISSN: 1354-1013
    E-ISSN: 1365-2486
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  • 10
    In: Eos, 01/28/2016, Vol.97
    ISSN: 2324-9250
    E-ISSN: 2324-9250
    Source: American Geophysical Union (via CrossRef)
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