Selective Preservation Research Articles

Peat decomposition proxies of Alpine bogs along a degradation gradient

The carbon sink function of peatlands is the result of a relatively small imbalance between biomass production and decay and proposed to be sensitive to changes in environmental conditions. Thus, peat decomposition plays a decisive role in determining the future carbon balances of peatlands under changing climatic conditions and increasing human pressure. To evaluate the effects of peatland degradation on the degree of decomposition in light of deviating site histories and to reveal interrelations between different indicators, we analysed peat depth profiles of physicochemical peat decomposition proxies across nine study sites in two valley bogs in the Eastern Alps, Austria. For this purpose, we divided 1 m peat cores sampled at the nine sites into 4 cm sections and analysed these peat samples for bulk density, loss on ignition, pH value, carbon and nitrogen content and ratio, stable carbon and nitrogen isotope signatures, and five humification indices based on Fourier transform infrared spectroscopy. Besides, we regularly measured water levels and incubated litter bags over two years. Peat characteristics were found to be relatively homogenous across the treeless and only slightly degraded sites. At these sites, depth profiles followed similar patterns with strongly increasing decomposition in the uppermost layers and the highest degree of peat decomposition at 40–56 cm depths for most proxies. Thus, our findings suggest that even apparently only slightly degraded sites were distinctly affected by past drainages. In contrast to the open peat bog sites, the degree in peat decomposition was distinctly higher at tree-encroached sites and at long-term drained former peat-cutting sites. Both, the distinct difference in the degree of decomposition between the two peatlands and the inverse decomposition depth trends, i.e., more decomposed peat overlying less decomposed layers, highlight the importance of secondary decomposition on the depth profiles and the strong effects of site histories on the current degree of peat decomposition. The results of two-year litter bag incubations of four vascular plant species revealed distinct differences in species-specific litter decomposition rates and considerable differences for same species between the two investigated bogs. The strong interrelations between different humification indices underline the simultaneous effects of proceeding decay on the different chemical properties of the peat. Besides, humification indices were strongly related with other physical and chemical properties of peats and highest loadings on the principal component 1 that accounted for 41% of the total variance of the dataset were found for four different humification indices, bulk density and nitrogen contents. We conclude that the selective preservation of aliphatic, acid and aromatic groups during peat decomposition are well suited to elucidate small-scale differences in the degree of decomposition and to strongly interrelate with established indicators as bulk densities.

Organic chemistry insights for the exceptional soil carbon storage of the seagrass Posidonia australis

The high organic carbon (OC) stores in seagrass meadows have led to their recognition as significant Blue Carbon sinks, though the diagenetic conditions that enable OC retention in seagrass soils remain poorly understood. In this study, seagrass soils were sampled from a Posidonia australis meadow in Oyster Harbour (Albany; south-western Australia) to investigate the preservation of sedimentary OC. We analysed soil characteristics (colour, grain size and redox potential), radiocarbon age, and characterised the soil organic matter (OM) using solid state CP/MAS 13C NMR spectroscopy to examine the preservation of OM down the soil profile. There was minimal change in organic composition over 1,700 years of accumulation, indicating long-term OM preservation. Primarily, this preservation appears to be driven by the recalcitrance of seagrass detritus buried in anoxic soils. The majority (70–83%) of total sedimentary OM comprised components directly attributable to seagrass origins (lignin, carbohydrate and black carbon-like matter), while the remainder consisted mostly of protein, some of which may have been present in seagrass biomass, along with likely contributions from algae and microbes. Although black carbon originates from organic matter combustion, here we provide evidence that the 13C NMR signal identified as black carbon-like matter in our soils is possibly associated with seagrass-derived organic matter consisting of degraded lignin products or other non-pyrogenic aromatics. The increase in the relative abundance of this black carbon-like matter with aging suggests its selective preservation. The relative abundances of carbohydrates significantly decreased with age down core (i.e. they appeared to be selectively decomposed), while lignin and protein did not show any quantitative changes in relative abundance (non-selective preservation). These findings demonstrate the exceptional preservation of P. australis derived OC, which contributes to our understanding of the higher OC storage capacity of Posidonia compared to other seagrass species.

Characteristics of organic matter sources from Guadiana Estuary salt marsh sediments (SW Iberian Peninsula)

Estuaries are dynamic interfaces between land, rivers and the ocean that play major roles in the global carbon cycle. These coastal wetlands store huge amounts of organic carbon (OC), commonly known as “blue carbon” and excellent places to study C cycling. The Guadiana river estuary is among the most important tidal salt marshes in the South - Iberian coastal margin. Here, a detailed organic geochemical study is described that includes the identification of sedimentary OM composition at a molecular and isotopic level. Total organic carbon content (TOC) of core sediments ranged from 0.39 to 2.23% and stable carbon isotope composition (δ13C) also showed a wide range between −22.4 and −27.0‰. A13C depletion trend observed from the surface to bottom in the core sediments profiles, reflects loss of labile biogenic 13C enriched compounds i.e. polysaccharides and a selective preservation of more depleted compounds with depth i.e. lignin and lipids in the core sediments. Series of n-alkanes were found in the range from C10 to C31. Carbon preference index ratio (CPI) calculated for long-chain n-alkanes (C24–C31) that ranged between 1.17 and 1.94 reflecting diverse OM inputs to the sediments. A study of the lignin-derived phenolic composition pointed to a recalcitrant OM derived from both gymnosperm and angiosperm plants. Moreover, high abundance of vinyl phenol and vinyl guaiacol points to a dominant contribution of lignins from grasses and aquatic macrophytes to the sediments. A well-resolved series of long-chain linear alkyl benzenes (LABs from C4 to C22) were recorded in all core sediment samples indicating direct discharge of untreated domestic and/or industrial effluents to the estuary. Polycyclic aromatic hydrocarbons (PAHs) with more than 3 rings reflects the pyrogenic origin of a portion of the sedimentary OM. This study highlights the importance of different OM sources to the lower Guadiana estuarine sediments and contributes to a better knowledge about its origin, dynamics and fate.

“Die While I Can Still Remember Who I Am”: Postcolonial Nostalgia and Trauma in Tan Twan Eng’s The Garden of Evening Mists

In his novel The Garden of Evening Mists, Tan Twan Eng, a contemporary novelist from Malaysia, meditates on the nature of remembering and forgetting, of selective preservation of the past and willful amnesia that constitutes the work of nostalgia and memory. Individual recollections are intertwined with the historical references to give a glimpse of trauma and nostalgia which undercut the discourses of collective history and nation-building in Malaysia. This paper unpacks the silences and erasures that create this overlap of trauma and nostalgia in The Garden of Evening Mists. Traumatizing memories of the colonial past, willfully forgotten and repressed, permeate the nostalgic narratives of the present. Through the metaphor of the garden which is central to the novel, Tan creates a space for interconnected memories, some explicit and some hidden in the landscape. Through these multidirectional memories where each act of remembrance evokes other memories of loss and suffering, the narrative reflects on the parallel tasks of remembering and forgetting in shaping the present and its accounts of the past. The novel touches on the forms of historical nostalgia where forgetting plays as important a role as remembering. In Tan’s novel, the postcolonial condition entails a form of survival where nostalgia for the past is forever linked to its trauma.

Late Palaeozoic red beds elucidate fluvial architectures preserving large woody debris in the seasonal tropics of central Pangaea

AbstractFluvial red beds containing anatomically preserved large woody debris shed new light on seasonally dry biomes of the Pennsylvanian–Permian transition and elucidate the concurrence of river depositional systems and vegetation. As a result, the occurrence, distribution and preservation of petrified large woody debris accumulations are considered crucial to understanding the role of arborescent vegetation in shaping fluvial environments. This study reports sizeable silicified trunks and corresponding fluvial architectures from the uppermost Pennsylvanian (upper Gzhelian) Siebigerode Formation (Kyffhäuser, central Germany). The origin, taphonomy and depositional environment of the fossil woods are elucidated by using a multidisciplinary approach including geological mapping, lithofacies analysis, sediment petrography, wood anatomical studies and microstructure analyses. Results reflect the gradual burial of a gentle basement elevation by sand‐bed to gravel‐bed braided rivers at the north‐western margin of the perimontane Saale Basin. Facies architectures resulted from a complex interplay of syndepositional tectonics, repeated palaeorelief rejuvenation, high‐frequency channel avulsion, seasonally dry climate and woody debris–sediment interactions. The alluvial influx and cut‐bank erosion recruited trunks from adjacent semi‐riparian slope habitats vegetated by up to 40 m tall cordaitaleans and conifers. High discharge in wide braids facilitated uncongested transport of large woody debris. Trunk entombment and initial preservation resulted from grounding on barforms, anchoring by attached roots and subsequent burial. The post‐depositional two‐phase silicification was influenced by hydrothermal hematite mineralization and determined a selective wood preservation pattern known as ‘pointstone’. Large woody debris‐induced sedimentary structures (‘LWDISS’) are introduced as a class of sediment structures formed by the biogenic impact on terrestrial deposition.

An Ancient and Eroded Social Supergene Is Widespread across Formica Ants.

Supergenes, clusters of tightly linked genes, play a key role in the evolution of complex adaptive variation [1, 2]. Although supergenes have been identified in many species, we lack an understanding of their origin, evolution, and persistence [3]. Here, we uncover 20-40 Ma of evolutionary history of a supergene associated with polymorphic social organization in Formica ants [4]. We show that five Formica species exhibit homologous divergent haplotypes spanning 11 Mbp on chromosome 3. Despite the supergene's size, only 142 single nucleotide polymorphisms (SNPs) consistently distinguish alternative supergene haplotypes across all five species. These conserved trans-species SNPs are localized in a small number of disjunct clusters distributed across the supergene. This unexpected pattern of divergence indicates that the Formica supergene does not follow standard models of sex chromosome evolution, in which distinct evolutionary strata reflectan expanding region of suppressed recombination [5]. We propose an alternative "eroded strata model" in which clusters of conserved trans-species SNPs represent functionally important areas maintained by selection in the face of rare recombination between ancestral haplotypes. The comparison of whole-genome sequences across 10 additional Formica species reveals that the most conserved region of the supergene contains a transcription factor essential for motor neuron development in Drosophila [6]. The discovery that a very small portion of this large and ancient supergene harbors conserved trans-species SNPs linked to colony social organization suggests that the ancestral haplotypes have been eroded by recombination, with selection preserving differentiation at one or a few genes generating alternative social organization.

On the negative carbon isotope excursion across the Wuchiapingian–Changhsingian transition: A regional event in the lower Yangtze region, South China?

Previous studies have reported faunal changeover and carbon isotope excursions through the Wuchiapingian–Changhsingian (WC) transition, a geologically significant period of time that bridged two major extinction events: the end-Permian and Guadalupian–Lopingian boundary mass extinctions. However, the causes of the carbon isotope excursion across the WC interval remain poorly understood. This study presents sedimentological and geochemical data from three well-exposed sections in the lower Yangtze region, South China. A strong negative carbon isotope excursion in organic matter is recorded across the WC interval and correlates well with other sections in South China. Sedimentology and elemental geochemistry indicate that the lower Yangtze region experienced a distinct regional deepening during the WC transition inducing bottom water redox changes increased primary productivity. Possible causes of the negative carbon isotope excursion at the WC boundary include selective preservation of organic matter during early diagenesis under anoxic/euxinic conditions and changes in terrigenous organic matter input. Both of these factors were controlled by regional relative sea-level rise triggered by contemporaneous tectonic movements.

Selective Preservation of Coccolith Calcite in Ontong‐Java Plateau Sediments

AbstractDissolution of calcite in deep ocean sediments, which is required to balance global marine CaCO3 production and burial fluxes, is still a poorly understood process. In order to assess the mechanisms of dissolution in sediments, we analyzed four multicore tops taken along a depth transect on the Ontong‐Java Plateau. These cores were taken directly on the equator, and span water column calcite saturation states from ∼0.93 to ∼0.74, allowing us to assess the effect of dissolution on carbonate sediment composition. The top 2 cm of each multicore was sectioned and sieved to separate coccolith from foraminiferal calcite, and the %CaCO3, δ13C, Δ14C, and Mg/Ca were evaluated. The mass ratio of coccoliths to foraminifera increases by a factor of 3 as a function of water depth, reflecting the preferential dissolution of foraminifera. Carbon isotope (δ13C and Δ14C) data suggest that most dissolution takes place at the sediment‐water interface and primarily affects foraminifera. Mg/Ca analyses indicate that the Mg content of the entire foraminiferal assemblage decreases as a function of dissolution. In contrast, coccolith dissolution takes place within the sediments, rather than at the interface. Together these two processes cause coccoliths to be up to 1,000 radiocarbon years younger than foraminifera from the same depth horizon. Despite this within‐sediment coccolith dissolution flux, sediments below the calcite saturation horizon remain enriched in coccolith calcite. Combined with global seafloor hypsometry and calcium carbonate content, this enrichment suggests that globally, coccoliths may outweigh foraminifera in deep ocean sediments by a factor of 1.8.

Molecular differences between water column and sediment pore water SPE-DOM in ten Swedish boreal lakes

Boreal lakes are considered hot spots of dissolved organic matter (DOM) processing within the global carbon cycle. This study has used FT-ICR mass spectrometry and comprehensive data evaluation to assess the molecular differences of SPE-DOM between lake column water SPE-DOM and sedimentary pore water SPE-DOM in 10 Swedish boreal lakes of the Malingsbo area, which were selected for their large diversity of physicochemical and morphological characteristics. While lake column water is well mixed and fairly oxygenated, sedimentary pore water is subject to depletion of oxygen and to confinement of molecules. Robust trends were deduced from molecular compositions present in all compartments and in all 10 lakes (“common compositions”) with recognition of relative abundance. Sedimentary pore water SPE-DOM featured higher proportions of heteroatoms N and S, higher average H/C ratios in presence of higher DBE/C ratios, and higher average oxygenation than lake column water SPE-DOM. These trends were observed in all lakes except Ljustjärn, which is a ground water fed kettle lake with an unique lake biogeochemistry. Analogous trends were also observed in case of single or a few lakes and operated also for compounds present solely in either lake column water or sedimentary pore water. Unique compounds detected in either compartments and/or in a few lakes showed higher molecular diversity than the “common compositions”. Processing of DOM molecules in sediments included selective preservation for polyphenolic compounds and microbial resynthesis of selected molecules of considerable diversity.

Climatic reconstruction at the Sannai-Maruyama site between Bond events 4 and 3\u2014implication for the collapse of the society at 4.2\u2009ka event

The Jōmon period/culture corresponds to the Neolithic period/culture in Japanese prehistory. The Sannai-Maruyama site (5.9–4.2 cal. kyr BP), the most famous, the largest, and the well-studied mid-Holocene (mid-Jōmon) archeological site inhabited by hunter-gatherers with sedentary lifestyle in northern Japan, started at early Bond event 4 and collapsed at late Bond event 3 (4.2 cal. kyr BP at the boundary between mid-Holocene, Northgrippian, and late-Holocene, Meghalayan), synchronous with the decline of the north Mesopotamian civilization and the Yangtze River civilization in China. Alkenone sea surface temperatures (SSTs), a proxy for early-midsummer SSTs, generally suggest that the early-midsummer SSTs (and atmospheric temperatures (ATs)) at 41° 00′ N, 140° 46′ E, about 20 km north to the Sannai-Maruyama site, located in Aomori Prefecture, peaked around 4.8–4.3 cal. kyr BP and showed minima at 5.9 and 4.1 cal. kyr BP. In spite of some discrepancy in short periods, this feature is consistent with that estimated from the assemblages of Ostracodas. δ18O value of benthic foraminifera of Nonionellina labradorica and Nonionella stella, alkenone production flux, and pollen assemblages could reflect annual-based temperature, which generally suggests that the climate was warmer at 6.0–4.2 cal. kyr BP, which could show the warmer environments at 6.0–5.0 cal. than expected from alkenone SST in early-midsummer. Overall, northward shift of the westerly jet, in association with a strengthened East Asian Summer Monsoon, could cause a relatively warm climate around 6.0–4.3 cal. kyr BP, when the Sannai-Maruyama site flourished. High food production density, by effective hansaibai (selective preservation or growth) in Castanea- and Aesculus-dominated forests, up to one sixth of the rice production density, could have supported high population density, resulting large community at the Sannai-Maruyama site. Cooling episode at 4.2 cal. kyr BP could have resulted in the decline of chestnut hansaibai, leading to the collapse of the site. Recent results from a compiled archeological site map suggested no large decline of the population but, instead, a dispersal to the surrounding area at 4.2 cal. kyr BP. It is consistent with ancestral population dynamics for the descendent from Jōmon people, in contrast to those from the immigrants from Far East Asia to the Japanese Archipelago with paddy rice cultivation technology after 2.9 cal. kyr BP, based on modern Japanese molecular sequences.

Does ectomycorrhiza have a universal key role in the formation of soil organic matter in boreal forests?

Forest soil organic matter (SOM) is an important dynamic store of C and N, which releases plant available N and the greenhouse gases CO2 and N2O. Early stages of decomposition of recent plant litters are better known than the formation of older and more stable soil pools of N and C, in which case classic theory stated that selective preservation of more resistant plant compounds was important. Recent insights heighten that all plant matter becomes degraded and that older SOM consists of compounds proximally of microbial origin. It has been proposed that in boreal forests, ectomycorrhizal fungi (ECMF), symbionts of trees, are actively involved in the formation of slowly-degrading SOM.We characterized SOM in the mor-layer along a local soil N supply gradient in a boreal forest, a gradient with large variations in chemical and biological characteristics, notably a decline in the biomass of ECMF in response to increasing soil N supply.We found contrasting and regular patterns in carbohydrates, lignin, aromatic carbon, and in N-containing compounds estimated by solid-state 13C and 15N nuclear magnetic resonance (NMR) spectroscopy. These occurred along with parallel changes in the natural abundances of the stable isotopes 13C and 15N in both bulk SOM and extracted fractions of the SOM. The modelled “bomb-14C″ age of the lower layers studied ranged between 15 years at the N-poor end, to 70 years at the N-rich end of the gradient. On average half the increase in δ13C with soil depth (and hence age) of the mor-layer can be attributed to soil processes and the other half to changes in the isotopic composition of the plant C inputs. There was a decrease in carbohydrates (O-alkyl C) with increasing depth. This supports the classical hypothesis of declining availability of easily decomposable substrates to microorganisms with increasing soil depth and age. The observed increase in δ13C with depth, however, speaks against the idea of selective preservation of more resistant plant compounds like lignin. Furthermore, from the N-poor to the N-rich end the difference between 15N in plant litter N and N in the deeper part of the mor-layer, the H-layer, decreased in parallel with a decline in ECMF.The latter provides evidence that the role of ECMF as major sink for N diminishes, and hence their potential role in SOM stabilization, when the soil N supply increases. At the N-rich end, where bacteria dominate over fungi, other agents than ECMF must be involved in the large build-up of the H-layer with the slowest turnover rate found along the gradient.

Enzymatic Incorporation of a Coumarin–Guanine Base Pair

AbstractPrevious expansions beyond nature's preferred base‐pairing interactions have utilized either nonpolar shape‐fitting interactions or classical hydrogen bonding. Reported here is a hybrid of these systems. By replacing a single N−H with C−H at a Watson–Crick interface, the design space for new drug candidates and fluorescent nucleobase analogues is dramatically expanded, as demonstrated here by the new, highly fluorescent deoxycytidine mimic 3‐glycosyl‐5‐fluoro‐7‐methoxy‐coumarin‐2′‐deoxyribose (dCC). dGTP is selectively incorporated across from a template dCC during enzymatic DNA synthesis. Likewise, dCC is selectively incorporated across from a template guanine when dCC is provided as the triphosphate dCCTP. DNA polymerase I (Klenow fragment) exhibited about a 10‐fold higher affinity for dCCTP than dCTP, allowing selective incorporation of dCC in direct competition experiments. These results demonstrate that a single C−H can replace N−H at a Watson–Crick‐type interface with preservation of functional selectivity and enhanced activity.

Enzymatic Incorporation of a Coumarin-Guanine Base Pair.

Previous expansions beyond nature's preferred base-pairing interactions have utilized either nonpolar shape-fitting interactions or classical hydrogen bonding. Reported here is a hybrid of these systems. By replacing a single N-H with C-H at a Watson-Crick interface, the design space for new drug candidates and fluorescent nucleobase analogues is dramatically expanded, as demonstrated here by the new, highly fluorescent deoxycytidine mimic 3-glycosyl-5-fluoro-7-methoxy-coumarin-2'-deoxyribose (dCC ). dGTP is selectively incorporated across from a template dCC during enzymatic DNA synthesis. Likewise, dCC is selectively incorporated across from a template guanine when dCC is provided as the triphosphate dCC TP. DNA polymerase I (Klenow fragment) exhibited about a 10-fold higher affinity for dCC TP than dCTP, allowing selective incorporation of dCC in direct competition experiments. These results demonstrate that a single C-H can replace N-H at a Watson-Crick-type interface with preservation of functional selectivity and enhanced activity.

Chemical structure of soil organic matter

Selective preservation belongs among the important stabilization mechanisms of soil organic matter (SOM). Conceptually, it is based on non-covalent intermolecular interactions of organic molecules, which leads to a decrease in the Gibbs’ energy of the SOM structure. Earlier works suggested that this stabilization of SOM physical structure is supported also by water molecules that form clusters bridging SOM moieties. This article reports results suggesting that water is connected also to stabilization of SOM chemical structure. We analyzed the dynamics and composition of gases evolved during drying of 33 mineral soils, which were exposed to 40% relative humidity prior to the analysis. It was observed that moisture elimination occurring below 100 °C is accompanied by evolution of a small amount of low molecular mass gases representing typical degradation products of organic materials. In particular, analyses revealed the evolution of CO, HCN, NO, and probably traces of NH3 and CO2, which implied degradation of N-containing molecules. The peak temperature of evolved CO correlated with the amount of adsorbed water. The amount of evolved CO positively correlated with the amount total organic C and N contents and clay content. On the contrary, the amount of CO evolved during degradation did not correlate with the amount of CO2 produced during incubation of analyzed soils either at short or longer incubation times. Evolution of gases started and culminated simultaneously with drying. The analysis of soils exposed to higher relative humidity levels resulted in a shift of the CO peaks to higher temperatures. Therefore, the results suggested a possible causality between water desorption at elevated temperature and SOM degradation processes.

Deposition and preservation of fluvio‐tidal shallow‐marine sandstones: A re‐evaluation of the Neoproterozoic Jura Quartzite (western Scotland)

AbstractThe 2 to 5 km thick, sandstone‐dominated (>90%) Jura Quartzite is an extreme example of a mature Neoproterozoic sandstone, previously interpreted as a tide‐influenced shelf deposit and herein re‐interpreted within a fluvio‐tidal deltaic depositional model. Three issues are addressed: (i) evidence for the re‐interpretation from tidal shelf to tidal delta; (ii) reasons for vertical facies uniformity; and (iii) sand supply mechanisms to form thick tidal‐shelf sandstones. The predominant facies (compound cross‐bedded, coarse‐grained sandstones) represents the lower parts of metres to tens of metres high, transverse fluvio‐tidal bedforms with superimposed smaller bedforms. Ubiquitous erosional surfaces, some with granule–pebble lags, record erosion of the upper parts of those bedforms. There was selective preservation of the higher energy, topographically‐lower, parts of channel‐bar systems. Strongly asymmetrical, bimodal, palaeocurrents are interpreted as due to associated selective preservation of fluvially‐enhanced ebb tidal currents. Finer‐grained facies are scarce, due largely to suspended sediment bypass. They record deposition in lower‐energy environments, including channel mouth bars, between and down depositional‐dip of higher energy fluvio‐ebb tidal bars. The lack of wave‐formed sedimentary structures and low continuity of mudstone and sandstone interbeds, support deposition in a non‐shelf setting. Hence, a sand‐rich, fluvial–tidal, current‐dominated, largely sub‐tidal, delta setting is proposed. This new interpretation avoids the problem of transporting large amounts of coarse sand to a shelf. Facies uniformity and vertical stacking are likely due to sediment oversupply and bypass rather than balanced sediment supply and subsidence rates. However, facies evidence of relative sea level changes is difficult to recognise, which is attributed to: (i) the areally extensive and polygenetic nature of the preserved facies, and (ii) a large stored sediment buffer that dampened response to relative sea‐level and/or sediment supply changes. Consideration of preservation bias towards high‐energy deposits may be more generally relevant, especially to thick Neoproterozoic and Lower Palaeozoic marine sandstones.

A patient- and assessor-blinded randomized controlled trial of axillary reverse mapping (ARM) in patients with early breast cancer

BackgroundAxillary lymph node dissection (ALND) in breast cancer patients is infamous for its accompanying morbidity. Selective preservation of upper extremity lymphatic drainage and accompanying lymph nodes crossing the axillary basin - currently resected during a standard ALND - has been proposed as a valuable surgical refinement. MethodsPeroperative Axillary Reversed Mapping (ARM) was used for selective preservation of upper extremity lymphatic drainage. A multicentre patient- and assessor-blinded randomized study was performed in clinical node negative, sentinel node positive early breast cancer patients. Patients were randomized to undergo either standard-ALND or ARM-ALND. Primary outcome was the presence of surgery-related lymphedema at six, 12 and 24 months post-operatively. Secondary outcomes included patient reported and objective signs and symptoms of lymphedema, pain, paraesthesia, numbness, loss of shoulder mobility, quality of life and axillary recurrence risk. ResultsNo significant differences were found between both groups using the water displacement method with respect to measured lymphedema. ARM-ALND resulted in less reported complaints of lymphedema at six, 12 and 24 months postoperatively (p < 0.05). No axillary recurrence was found in both groups. ConclusionsIn contrast to results of volumetric measurement, patient reported outcomes support selective sparing of the upper extremity lymphatic drainage using ARM as valuable surgical refinement in case of ALND in clinically node negative, sentinel node positive early breast cancer. If completion ALND in clinically node negative, sentinel node positive early breast cancer is considered, selective sparing of upper extremity axillary lymphatics by implementing ARM should be carried out in order to reduce morbidity.

Spectral characteristics of water-soluble and alkaline-soluble organic substance of fallow light-gray forest soils

The content of organic matter (OM) and its individual fractions were studied in different ages (7 and 75-80 years-old) fallow soils. The qualitative composition of labile OM fractions was evaluated by the criteria of SUVA254 and Sr, which were calculated from the absorption spectra in the UV range. It was shown that as deposits age, there is a significant increase in the content of total organic carbon (TOC) in soils and a change in the qualitative composition of its labile fractions. From the nature of changes in the degree of aromaticity and molecular masses of labile fractions with the age of deposits, a conclusion can be drawn that the factor of selective preservation of compounds resistant to degradation is relevant only to stabilize the water-soluble OM. The stability of alkaline-soluble OM fractions is most likely provided by the formation of organic and organic-mineral associations.

Selective preservation of pyrogenic carbon across soil organic matter fractions and its influence on calculations of carbon mean residence times

The long-standing perspective that recalcitrance of soil organic carbon (SOC) controls its stability and persistence has shifted to one in which physical inaccessibility of SOC to microorganisms plays a predominant role. This paradigm shift has been facilitated by analytical techniques that isolate SOC into physical fractions protected from decomposers by different mechanisms. The correlation between these fractions and SOC age has reinforced the emphasis of SOC inaccessibility. Pyrogenic C (PyC; also called charcoal or black carbon), which has been thermally altered by fire, is known to contain highly recalcitrant components that decompose very slowly and could represent an exception to this paradigm shift. We employed hydrogen pyrolysis to quantify the contribution of PyC to total SOC across soil fractions from three long-term agricultural experiments with land use conversions that caused reductions in SOC. We show that all soil fractions contain PyC and up to one-fifth of SOC in soil fractions considered to have low accessibility is comprised of PyC. Regardless of the soil fraction in which it was located, PyC was relatively unaffected by land use conversion compared to biogenic C (organic C not altered by fire), which suggests that selective preservation, rather than physical protection, is the dominant mechanism limiting PyC decomposition in these sites. We accounted for PyC in calculations of C mean residence times (MRTs) using differences in stable C isotope ratios between PyC and SOC. Though results varied by site and soil fraction, MRTs for biogenic C were generally shorter than for total SOC. Based on these results, PyC decomposition is controlled by a different mechanism than biogenic C, and this should be considered in studies of soil C dynamics. In addition, methods based on physical fractionation alone may place too great an emphasis on the role of inaccessibility for long-term SOC persistence.

Species–area relationships in isolated coastal sandy patches: Implications for the conservation of beach–dune flora in a rocky coastal region of western Japan

AbstractQuestionsIn many places worldwide, dune vegetation has rapidly declined owing to the expansion of various land uses, which pose a serious threat to many native dune plant species. A better understanding of species–area relationships in coastal sandy patches (i.e., beaches and dunes) is valuable for designing effective management strategies for the conservation of beach–dune flora in coastal regions. We investigated how the area and other attributes of sandy patches affect the number of species (dune, inland, and alien species) and whether the occurrence of all dune species is area‐dependent.LocationSandy coast of San'in Kaigan National Park, western Japan.MethodsAll vascular plants at 43 sites (sandy patches) were recorded. Using generalized linear models, we analyzed the relationships of the area and other attributes of sandy patches with the number of species and the relationship between the area of sandy patches and the occurrence (presence/absence) of each dune species.ResultsLarger sandy patches maintained a greater number of dune species and harbored some nationally threatened ones. The number of inland and alien species also increased with an increasing area of sandy patches, although the effects of other size and site attributes varied; shoreline length, beach–dune height, and high openness of the beach were selected as important positive factors for the number of dune species. Furthermore, most dune species in herb and dwarf shrub zones were area‐dependent and tended to occur in larger sandy patches, whereas some species of the tidal drift zone, including locally threatened dune species, were area‐independent.ConclusionsEffective conservation of beach–dune flora demands not only the protection of larger sandy patches but also the selective preservation of sandy patches with better developed dunes. Moreover, the maintenance of unstable habitats for area‐independent dune species is important.

Unsupervised feature selection with adaptive residual preserving

Many feature selection approaches are proposed in recent years. Most approaches utilize graph-based methods in studying the structure and relationship among data. However, many data relationships may loss during the graph construction, such as the residual relationships. To better preserve the relationships between data, in this paper, we propose a novel unified learning framework - unsupervised feature selection with adaptive residual preserving (UFSARP). The framework unifies feature selection, data reconstruction, and local residual preserving into one unified process, in which these tasks are completed simultaneously. We use the distance of projected data to learn the similarity matrix and simultaneously impose it on the data representation term to enforce that similar samples have similar reconstruction residuals. The use of such learning way has three-fold advantages: (1) The reconstruction residuals aim to maintain the residual relationships between data samples, namely, similar samples have similar residuals, and this helps to reconstruct the original data better; (2) Imposing the similarity matrix on the data representation term encourages similar samples not only have similar reconstruction residuals but also have similar reconstruction coefficients; (3) The similarity matrix and the reconstruction coefficient can be promoted by each other during the learning process. The experimental results show that the proposed algorithm is superior to other similar researches.