The influence of soil processes on carbon isotope distribution and turnover in the British uplands     

R. A. Bol  D. D. Harkness  Y. Huang  D. M. Howard 《European Journal of Soil Science》1999,50(1):41-51

Understanding the natural variation of carbon within the soil, and between soil types, is crucial to improve predictive models of carbon cycling in high and mid-latitude ecosystems in response to global warming. We measured the carbon isotope distributions (¹²C, ¹³C and ¹⁴C) in soil organic matter (SOM) from Podzols, Brown Podzolic soils and Stagnohumic Gleysols from the British uplands, which were then compared with the total amounts and turnover of carbon in these soils. We did so by sampling at 2-cm intervals down six profiles of each soil type. The average amount of carbon stored in the top 28 cm of the Stagnohumic Gleysols is twice that of the other two soils. The ¹³C content and ¹⁴C age show a general increase with depth in all soils, and there is also a significant correlation between isotopic variation and the main pedogenic features. The latter suggests that soil-forming processes are significant in determining the carbon isotope signatures retained in SOM. Organic matter formed since 1960 is not found below 5 cm in any of the soils. Evidently organic detritus in the surface layers (LF and Oh) is rapidly mineralized. This accords with our modelled net annual C fluxes which show that more than 80% of the CO₂ emanating from these soils is derived from the top 5 cm of each profile. Although these soils contain much carbon, they do not appear to assimilate and retain SOM rapidly. The mean residence time of most of their carbon is in the 2–50 years range, so the soils are fairly ineffective sinks for excess CO₂ in the atmosphere. Under the predicted future ‘greenhouse’ climate, likely to favour more rapid microbial decomposition of organic materials, these soils are a potential source of CO₂ and are therefore likely to accelerate global warming.  相似文献   

Short Communication — Kurzmitteilung Siliziumcarbid — eine Alternative zur Aluminiumoxid‐Saugkerze?     

Axel Gttlein  Jrg Adler  Roland Blasek 《植物养料与土壤学杂志》2000,163(5):559-560

Siliciumcarbide — is it an alternative to suction cups made of aluminumoxide? Siliziumcarbide (SiC) is a novel non‐oxide ceramic material. We tested differently preconditioned SiC and aluminum‐oxide ceramics (P80) with respect to their influence on the solution passing through. For this we used a cation standard, an anion standard and a soil solution. Both ceramics released considerable amounts of Na and Al. However, in most cases SiC showed better results for anions and dissolved organic carbon. Therefore it may be a promising task to improve the properties of SiC by minimizing sinter additives and optimized conditioning procedures, and develop improved suction cups.  相似文献   

Differing trophic niches of three French stygobionts and their implications for conservation of endemic stygofauna     

Fabio Ercoli  Franois Lefebvre  Marjorie Delangle  Nil God  Michel Caillon  Roland Raimond  Catherine Souty‐Grosset 《水产资源保护:海洋与淡水生态系统》2019,29(12):2193-2203

Effects of Land‐Related Policies on Land Development during a Real Estate Boom and a Recession          下载免费PDF全文

Seong‐Hoon Cho  Seung Gyu Kim  Roland K. Roberts  Dayton M. Lambert  Taeyoung Kim 《Growth and change》2015,46(2):218-232

Our research evaluates and compares the effects of three land‐related policies on land development in a sprawling metropolitan area during a real estate boom and a recession. Our findings suggest that during a real estate boom 1) the urban growth boundary (UGB) serves its purpose of attracting urban development inside the given boundary during a boom while its effectiveness diminishes with increased development pressure from lower‐valued land outside of the UGB during a recession period, 2) the agricultural zone works well for restraining new development during a boom period while agriculture zoned parcels are more likely developed during a recession period, and 3) an increase in the land‐value tax bill increases the incentive for development during a recession period while higher tax bills do not affect development during a boom period. In anticipation of a re‐emergence of urban sprawl with the recovery of the real estate market, our findings imply that land planners and others concerned with sprawling development should pay more attention to development in sprawl‐prone areas during recession periods.  相似文献   

Adsorption process of polar and nonpolar compounds in a nanopore model of humic substances     

Daniel Tunega  Martin H. Gerzabek  Georg Haberhauer  Hans Lischka  Roland Solc  Adelia J. A. Aquino 《European Journal of Soil Science》2020,71(5):845-855

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The herbicide binding niche of photosystem II-a model     

Klaus G. Tietjen  Joachim F. Kluth  Roland Andree  Michael Haug  Markus Lindig  Klaus H. Müller  Heinz J. Wroblowsky  Achim Trebst 《Pest management science》1991,31(1):65-72

The Q_B binding niche of photosystem II is also the binding site for many different herbicides. In order to understand the mode of binding of the herbicides, a 3-dimensional model of the binding niche was constructed. The model was based upon a comparison of the known structure of the Q_B binding niche in purple bacteria with sequence and mutant data of the D-1 protein of photosystem II. Plastoquinone builds up hydrogen bonds to phenylalanine 265 backbone amide nitrogen, to serine 264 hydroxyl, and to histidine 215 delta-1 nitrogen. In addition to these hydrogen bond donors and acceptors, herbicides can build up hydrogen bonds to backbone carbonyl of alamine 263 and to serine 268 hydroxyl. This is supported by binding data of inhibitors in Chlamydomonas reinhardtii chloroplasts of wild type and of five D-1 protein mutants (Ser264 Ala, Ala251 Val, Phe255Tyr, Val2191le, Leu275Phe).  相似文献   

Onderzoekingen verricht in 1937 over de vergelingsziekte en enkele minerale gebreken bij de biet en de spinazie     

G. Roland 《European journal of plant pathology / European Foundation for Plant Pathology》1939,45(1):1-22

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Onderzoekingen Verricht in 1938 Over De Vergelingsziekte,De Zwarte Vlekken,De Vorming Van Anthocyaan En De Ontleding Van Zetmeel Bij De Biet     

G. Roland 《European journal of plant pathology / European Foundation for Plant Pathology》1939,45(5):181-203

Ohne Zusammenfassung Recherches effectuées en 1938 sur la jaunisse, les taches noires, la formation d’anthocyanine et l’analyse de l’amidon chez la betterave  相似文献   

Measuring nitrogen fixation by <Emphasis Type="Italic">Sesbania sesban</Emphasis> planted fallows using <Superscript>15</Superscript>N tracer technique in Kenya     

Lena?St?hlEmail author  Peter?H?gberg  Anita?Sellstedt  Roland J.?Buresh 《Agroforestry Systems》2005,65(1):67-79

A field experiment was performed in eastern Kenya to estimate N₂ fixation by Sesbania sesban over an 18-month period using the ¹⁵N dilution method. The influence of three reference species, Senna spectabilis, Eucalyptus saligna and Grevillea robusta, on the estimates of N₂ fixation was also assessed. Percentage Ndfa (nitrogen derived from the atmosphere) was calculated based on foliar atom excess (FAE), above-ground atom excess (AAE) or whole tree atom excess (WAE) data. The differences in atom% ¹⁵N excess values between species and plant parts are presented and discussed. We recommend the use of several reference species for estimating %Ndfa and that the different results obtained should be carefully considered in relation to the issues being addressed. In this study, Senna was the most suitable of the three reference species because its N uptake pattern and phenology were very similar to those of Sesbania. When well established, the amount of N fixed by Sesbania accounts for more than 80% of its total N content, according to FAE-based estimates. We estimated the Ndfa by Sesbania after 18 months to between 500 and 600 kg ha⁻¹ , depending on whether FAE, AAE or WAE data were used and on the choice of reference species. The substantial accumulation of N in planted Sesbania highlighted its potential to increase the sustainability of crop production on N-limited soils. We consider the ¹⁵N dilution method to be appropriate for quantifying N₂ fixation in improved fallows in studies, similar to this one, of young trees with high N₂-fixing ability.  相似文献   

Effects of tension wood on specific conductivity and vulnerability to embolism of Quercus ilex seedlings grown at two atmospheric CO2 concentrations     

Gartner BL  Roy J  Huc R 《Tree physiology》2003,23(6):387-395

To determine whether there are decreases in hydraulic function of a woody stem when it has increased mechanical loading, Quercus ilex L. seedlings were grown upright or inclined to force the production of large amounts of tension wood (TW). Seedlings were grown in ambient or elevated carbon dioxide concentrations ([CO2]) for 16-17 months to provide two sets of seedlings differing in growth rates and allocation patterns. In both CO2 environments, inclination caused formation of large amounts of TW at the base and mid-section of most stems, but not at the stem tips. Contrary to expectation, there were no significant effects of stem inclination or amount of TW on specific conductivity (k(s)) or vulnerability to embolism. Samples with high amounts of TW had higher vessel frequency, similar average vessel lumen area, similar vessel lumen fraction (6% of the transverse area), elevated frequency of vessels in the smallest diameter class, and higher wood density than samples with very little TW. Samples from seedlings in the elevated [CO2] treatment had similar vessel frequency, larger average vessel lumen area (caused by a higher frequency of large-diameter vessels), similar vessel lumen fraction, and similar wood density as samples from seedlings in the ambient [CO2] treatment. There was a strong position effect: the highest wood density and lowest ks were at the stem base, intermediate values were at the middle, and the lowest density and highest ks were at the stem tip. We conclude that, in a species that uses different cells for mechanical support and water transport, there can be large modifications in performance of the mechanical function through TW formation without impacting the water transport functions-ks and vulnerability to embolism.  相似文献