Changes in soil chemistry associated with the establishment of forest gardens on eroded,acidified grassland soils in Sri Lanka     

Ilyas Siddique  Caroline Gutjahr  Gamini Seneviratne  Broder Breckling  Sudheera W. Ranwala  Ian J. Alexander 《Biology and Fertility of Soils》2007,44(1):163-170

Topsoil properties were determined in forest gardens established about 20 years ago on eroded grassland soils (abandoned tea lands) in the wet zone of the Sri Lankan highlands. They were compared with adjacent, eroded grasslands (abandoned tea lands) on strongly weathered soils vs soils at earlier stages of pedogenic development in a two-way analysis of variance. Soil pH in forest gardens was, on average, 6.1, nearly one unit higher than in the adjacent grasslands. In the garden soils, the cation exchange capacity (CEC measured at pH 4.8) was nearly double, exchangeable calcium concentrations five times and exchangeable magnesium three times as high as in the grasslands soils. Total soil N content was found to be nearly 40% higher in the gardens. Topsoil gravel contents in the gardens were less than half as high as in the grasslands. The increases in exchangeable bases and N in gardens, relative to grasslands, were attributed to increased nutrient retention and acquisition. Higher retention was partly due to the higher CEC_pH4.8, and probably to reduced erosion and increased, continuous fine root density in the garden topsoils. Higher field CEC in gardens was likely to result from generally higher C contents and from the reversal of acidification, presumably caused by base accumulation and decomposition processes. Our results suggest that forest garden establishment on degraded grasslands can lead to accumulation of mobile nutrients in the topsoil, probably due to increased nutrient retention, subsoil uptake and litter input exceeding nutrient uptake by the standing biomass.  相似文献   

Crossing the thresholds: human ecology and historical patterns of landscape degradation   总被引：2，自引：0，他引：2  

Ian A. Simpson  Andrew J. Dugmore  Amanda Thomson  Orri Vsteinsson 《CATENA》2001,42(2-4)

In discussions of landscape sensitivity, human activities have generally been regarded as external forces contributing to landscape change, with a focus on the impacts of cultivation methods, fertiliser practices, grazing pressures and atmospheric pollution. However, there has been comparatively little study undertaken that integrates physical and social systems in a historic context to explain the basis of human activity in sensitive landscapes. Where such attempts have been made, the manner of common land management has figured prominently, with ‘tragedy of the commons’ concepts used to explain land degradation and to provide a foundation for policy response. This has also been the case in Southern Iceland and in this paper we assess the extent to which common land domestic grazing pressures were the primary external force causing soil erosion and land degradation during the period of occupation from ca. 874 AD. We first provide field observation of soil erosion, temporally defined by tephrochronology, to highlight the extent of land degradation during this period. The ‘tragedy of the commons’ explanation of degradation is then assessed by evaluating historic documentary sources, and by environmental reconstruction and modeling of historic grazing pressures. These analyses indicate that regulatory mechanisms were in place to prevent overgrazing from at least the 1200s AD and suggest that there was sufficient biomass to support the numbers of domestic livestock indicated from historic sources. We suggest that failure to remove domestic livestock before the end of the growing season and an absence of shepherding were more likely to contribute to land degradation than absolute numbers. Lack of appropriate regulation of domestic livestock on common grazing areas can be attributed to limited cultural knowledge of changing and rapidly fluctuating environmental conditions.  相似文献   

Where systems biology meets postharvest     

Maarten L.A.T.M. Hertog  David R. RudellRomina Pedreschi  Robert J. SchafferAnnemie H. Geeraerd  Bart M. Nicolaï  Ian Ferguson 《Postharvest Biology and Technology》2011,62(3):223-237

According to the dictionary, a system is something like “a group or combination of interrelated, interdependent, or interacting elements forming a collective entity”. In postharvest, fresh harvested food crops can be considered isolated small scale systems. Postharvest research aims to understand the quality of these ‘systems’ as influenced by postharvest conditions. The phenotypic quality of horticultural produce is based on genetic traits that are expressed through a cascade of reactions subject to complex regulatory mechanisms and diverse environmental conditions. Ultimately, to fully understand postharvest phenomena, a systemic approach that links genetic and environmental responses and identifies the underlying biological networks is required. Thanks to the development of high throughput omics techniques such system-wide approaches have become a viable option to support traditional postharvest research. This review provides an overview of systems biology and how it can lead postharvest research into a new era.  相似文献   

一组含叔丁基二苯基硅氧基化合物的¹³CNMR特征(简报)     

王道全  Ian W.J.Still 《中国农业大学学报》1994,(3):345-345

我们在一项研究中合成了一组含叔丁基二苯基硅氧基(TBPSO)的化合物(Ⅰ),结构如下: 并测定了它们的400MHZ ~(13)CNMR 谱。由于 TBPSO 是有机合成中重要的羟基保护基,本文提供的数据,对鉴别含此基因的化合物可能有所帮助。现将结果报导于后。  相似文献   

Did cooling oceans trigger Ordovician biodiversification? Evidence from conodont thermometry     

Trotter JA  Williams IS  Barnes CR  Lécuyer C  Nicoll RS 《Science (New York, N.Y.)》2008,321(5888):550-554

The Ordovician Period, long considered a supergreenhouse state, saw one of the greatest radiations of life in Earth's history. Previous temperature estimates of up to approximately 70 degrees C have spawned controversial speculation that the oxygen isotopic composition of seawater must have evolved over geological time. We present a very different global climate record determined by ion microprobe oxygen isotope analyses of Early Ordovician-Silurian conodonts. This record shows a steady cooling trend through the Early Ordovician reaching modern equatorial temperatures that were sustained throughout the Middle and Late Ordovician. This favorable climate regime implies not only that the oxygen isotopic composition of Ordovician seawater was similar to that of today, but also that climate played an overarching role in promoting the unprecedented increases in biodiversity that characterized this period.  相似文献   

T cell activation by lipopeptide antigens   总被引：2，自引：0，他引：2  

Moody DB  Young DC  Cheng TY  Rosat JP  Roura-Mir C  O'Connor PB  Zajonc DM  Walz A  Miller MJ  Levery SB  Wilson IA  Costello CE  Brenner MB 《Science (New York, N.Y.)》2004,303(5657):527-531

Unlike major histocompatibility proteins, which bind peptides, CD1 proteins display lipid antigens to T cells. Here, we report that CD1a presents a family of previously unknown lipopeptides from Mycobacterium tuberculosis, named didehydroxymycobactins because of their structural relation to mycobactin siderophores. T cell activation was mediated by the alphabeta T cell receptors and was specific for structure of the acyl and peptidic components of these antigens. These studies identify a means of intracellular pathogen detection and identify lipopeptides as a biochemical class of antigens for T cells, which, like conventional peptides, have a potential for marked structural diversity.  相似文献   

CoRoT measures solar-like oscillations and granulation in stars hotter than the Sun     

Michel E  Baglin A  Auvergne M  Catala C  Samadi R  Baudin F  Appourchaux T  Barban C  Weiss WW  Berthomieu G  Boumier P  Dupret MA  Garcia RA  Fridlund M  Garrido R  Goupil MJ  Kjeldsen H  Lebreton Y  Mosser B  Grotsch-Noels A  Janot-Pacheco E  Provost J  Roxburgh IW  Thoul A  Toutain T  Tiphène D  Turck-Chieze S  Vauclair SD  Vauclair GP  Aerts C  Alecian G  Ballot J  Charpinet S  Hubert AM  Lignières F  Mathias P  Monteiro MJ  Neiner C  Poretti E  de Medeiros JR  Ribas I  Rieutord ML  Cortés TR  Zwintz K 《Science (New York, N.Y.)》2008,322(5901):558-560

Oscillations of the Sun have been used to understand its interior structure. The extension of similar studies to more distant stars has raised many difficulties despite the strong efforts of the international community over the past decades. The CoRoT (Convection Rotation and Planetary Transits) satellite, launched in December 2006, has now measured oscillations and the stellar granulation signature in three main sequence stars that are noticeably hotter than the sun. The oscillation amplitudes are about 1.5 times as large as those in the Sun; the stellar granulation is up to three times as high. The stellar amplitudes are about 25% below the theoretic values, providing a measurement of the nonadiabaticity of the process ruling the oscillations in the outer layers of the stars.  相似文献   

The global circulation of seasonal influenza A (H3N2) viruses     

Russell CA  Jones TC  Barr IG  Cox NJ  Garten RJ  Gregory V  Gust ID  Hampson AW  Hay AJ  Hurt AC  de Jong JC  Kelso A  Klimov AI  Kageyama T  Komadina N  Lapedes AS  Lin YP  Mosterin A  Obuchi M  Odagiri T  Osterhaus AD  Rimmelzwaan GF  Shaw MW  Skepner E  Stohr K  Tashiro M  Fouchier RA  Smith DJ 《Science (New York, N.Y.)》2008,320(5874):340-346

Antigenic and genetic analysis of the hemagglutinin of approximately 13,000 human influenza A (H3N2) viruses from six continents during 2002-2007 revealed that there was continuous circulation in east and Southeast Asia (E-SE Asia) via a region-wide network of temporally overlapping epidemics and that epidemics in the temperate regions were seeded from this network each year. Seed strains generally first reached Oceania, North America, and Europe, and later South America. This evidence suggests that once A (H3N2) viruses leave E-SE Asia, they are unlikely to contribute to long-term viral evolution. If the trends observed during this period are an accurate representation of overall patterns of spread, then the antigenic characteristics of A (H3N2) viruses outside E-SE Asia may be forecast each year based on surveillance within E-SE Asia, with consequent improvements to vaccine strain selection.  相似文献   

Coeval large-scale magmatism in the Kalahari and Laurentian cratons during Rodinia assembly     

Hanson RE  Crowley JL  Bowring SA  Ramezani J  Gose WA  Dalziel IW  Pancake JA  Seidel EK  Blenkinsop TG  Mukwakwami J 《Science (New York, N.Y.)》2004,304(5674):1126-1129

We show that intraplate magmatism occurred 1106 to 1112 million years ago over an area of two million square kilometers within the Kalahari craton of southern Africa, during the same magnetic polarity chron as voluminous magmatism within the cratonic core of North America. These contemporaneous magmatic events occurred while the Rodinia supercontinent was being assembled and are inferred to be parts of a single large igneous province emplaced across the two cratons. Widespread intraplate magmatism during Rodinia assembly shows that mantle upwellings required to generate such provinces may occur independently of the supercontinent cycle.  相似文献   

Service-oriented science   总被引：1，自引：0，他引：1  

Foster I 《Science (New York, N.Y.)》2005,308(5723):814-817

New information architectures enable new approaches to publishing and accessing valuable data and programs. So-called service-oriented architectures define standard interfaces and protocols that allow developers to encapsulate information tools as services that clients can access without knowledge of, or control over, their internal workings. Thus, tools formerly accessible only to the specialist can be made available to all; previously manual data-processing and analysis tasks can be automated by having services access services. Such service-oriented approaches to science are already being applied successfully, in some cases at substantial scales, but much more effort is required before these approaches are applied routinely across many disciplines. Grid technologies can accelerate the development and adoption of service-oriented science by enabling a separation of concerns between discipline-specific content and domain-independent software and hardware infrastructure.  相似文献