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   

Nitrogen-fixing legume tree species for the reclamation of severely degraded lands in Brazil     

Chaer GM  Resende AS  Campello EF  de Faria SM  Boddey RM 《Tree physiology》2011,31(2):139-149

The main challenges faced in the reclamation of severely degraded lands are in the management of the systems and finding plant species that will grow under the harsh conditions common in degraded soils. This is especially important in extremely adverse situations found in some substrates from mining activities or soils that have lost their upper horizons. Under these conditions, recolonization of the area by native vegetation through natural succession processes may be extremely limited. Once the main physical and chemical factors restrictive to plant growth are corrected or attenuated, the introduction of leguminous trees able to form symbioses with nodulating N?-fixing bacteria and arbuscular mycorrhizal fungi constitutes an efficient strategy to accelerate soil reclamation and initiate natural succession. These symbioses give the legume species a superior capacity to grow quickly in poor substrates and to withstand the harsh conditions presented in degraded soils. In this article we describe several successful results in Brazil using N?-fixing legume tree species for reclamation of areas degraded by soil erosion, construction and mining activities, emphasizing the potential of the technique to recover soil organic matter levels and restore ecosystem biodiversity and other environmental functions.  相似文献   

Pine wilt disease: a short review of worldwide research   总被引：1，自引：0，他引：1  

Alexander Yu. RYSS  Oleg A. KULINICH  Jack R. SUTHERLAND 《中国林学(英文版)》2011,13(2):132-138

This article summarizes the results of the research papers presented at the International Symposium on pine wilt disease (IUFRO Working Party Meeting 4.04.03) held in July 2009, at Nanjing, China. The general topics covered were on pine wilt disease (PWD), its causal organism, the pinewood nematode (PWN) Bursaphelenchus xylophilus, plus other PWN-associated microorganisms that play a significant role in PWD such as bacteria (e.g. Pseudomonas fluorescens). Most of the papers that are reviewed are based on work on PWD-PWN in East Asia and Russia. Specific topics covered include: 1) the fundamental conceptions of PWD development, 2) pathogenicity, 3) host-parasite relationships including the histopathology of diseased conifers and the role of toxins from bacteria-nematode ecto-symbionts, 4) PWN life cycle and transmission, 5) B. xylophilus dissemination models, 6) associations (with other nematodes), 7) diagnostics, 8) quarantine and control of the PWN and 9) biocontrol of the PWN.  相似文献   

Cadmium and other heavy metals in sea-skaters     

Lanna Cheng  George V. Alexander  Paul J. Franco 《Water, air, and soil pollution》1976,6(1):33-38

Exceptionally high concentrations of Cd (100 to 200 ppm dry weight) were found in samples of Halobates collected off Baja California. In contrast, no detectable Cd was found in Rheumatobates collected from mangrove lagoons in the Gulf of California. Concentrations of five other heavy metals in the two marine insects are also presented.  相似文献   

Responses by iron-efficient and inefficient oat cultivars to inoculation with siderophore-producing bacteria in a calcareous soil     

D. B. Alexander  D. A. Zuberer 《Biology and Fertility of Soils》1993,16(2):118-124

Rhizosphere bacteria may enhance plant uptake of Fe by producing siderophores that chelate sparingly soluble Fe³⁺ in calcareous soils. To evaluate the extent to which plants benefit from colonization of the roots by prolific siderophore-producing bacteria, we inoculated two oat cultivars with six strains of bacteria that produced high concentrations of siderophores under Felimiting conditions in vitro. Oat cv Coker 227, an Fe-efficient cultivar, which produces the phytosiderophore avenic acid, and cv TAM 0-312, and Fe-inefficient cultivar, which does not produce the phytosiderophore, were grown in a calcareous soil (Weswood silt loam) on a light bench in the laboratory. Half of the plants were fertilized with a nutrient solution containing 5 mM Fe and half with a nutrient solution containing no Fe. After 6 weeks of growth, we compared colonization of the roots by the inoculant bacteria and the dry weight and Fe content of roots and shoots. Three species of Pseudomonas colonized the roots of both oat cultivars in high numbers (10⁶ cells g^-1 root dry weight), whereas the remaining bacteria colonized the roots in substantially lower numbers (10⁴ cells g^-1 root dry weight). Plants fertilized with 5 mM Fe were larger and supported greater numbers or rhizosphere bacteria per gram of root than plants not supplied with Fe. Comparisons of the Fe content and dry weight of roots and shoots revealed few significant differences between inoculated and uninoculated plants, or among the plants inoculated with the different strains of siderophore-producing bacteria. The differences that were observed revealed no consistent response to inoculation. We conclude that inoculation of the roots of the two oat cultivars with bacteria that produce high concentrations of siderophores in response to an Fe deficiency had little or no effect on Fe acquisition by the plants.  相似文献   

Transfer of veterinary drugs and pharmacologically-active feed additives into soil with special consideration of tetracyclines – executive summary     

Christoph Winckler  Alexander Grafe 《Journal of Soils and Sediments》2001,1(1):58-62

Conclusions  

–	•In intensive animal production, a considerable proportion of the livestock population must be expected to receive animal pharmaceuticals.
–	•The administration of pharmacologically-active feed additives has been influenced through the revocation of approval for some individual substances over the last few years. Aside from the substitution of these forbidden substances, further reductions in the use of antibiotic growth promotors can be expected primarily because of economic reasons.
–	•Animal pharmaceuticals frequently consist of so-called older preparations whose ecotoxicological potentials have only been investigated inadequately.
–	•High elimination rates of the active substances and their stability during storage, which could be demonstrated for tetracyclines, might also lead to a significant incorporation of these substances into the soil even when they are employed correctly. In the future, ecotoxicological investigations should be demanded in cases where the EMEA/CVMP trigger values (which are substantially lower) have been exceeded, a procedure which is currently only required for the newly approved agents.
–	•There is presently a considerable need for research into the environmental fate of these older preparations and their ecotoxicological effects. Here, it will be especially important to take the degradation and transformation processes in the soil into account, as well as especially considering the consequences on the microbiological impacts affecting the soil.
–	•Improved transparency in the application of these substances, in the sense of a quantitative’registration of the animal pharmaceuticals (especially the older preparations) which are employed, as well as the environmental monitoring of animal pharmaceuticals (e.g. in groundwater and surface water), would considerably improve the significance of the basic data for future appraisals.

German federal research plan from the German Federal Ministry for the Environment, Wildlife Conservation and Nuclear Safety - Treatment and utilization of wastes. Research report 297 33 911 - UBA-FB 000074. Original title: Charakterisierung und Verwertung von Abf?llen aus der Massentierhaltung unter Berücksichtigung verschiedener B?den. Stoffeintrag in B?den durch Tierarzneimittel und pharmakologisch wirksame Futterzusatzstoffe unter besonderer Berücksichtigung von Tetrazyklinen. A research article on this topic follows in JSS No. 2. DOI: http://dx.doi.org/10.1065/jss2001.02.006. By courtesy of the German Federal Environmental Agency (Umweltbundesamt - UBA). The complete research report is available as UBA-TEXTE 44/00 (ISSN 0722-186X) by payment of DM 20,00 (Euro 10,26), account no. 4327 65-104, Postbank Berlin (BLZ 10010010), Fa. Werbung und Vertrieb, Ahornstra?e 1-2, D-10787 Berlin, Germany  相似文献   

A mobile rain exclusion canopy system to determine dose-response relationships for crops and forest species     

Allen Kuja  Randy Jones  Alexander Enyedi 《Water, air, and soil pollution》1986,31(1-2):307-315

A fully automated rain exclusion canopy system has been designed and constructed to study the impact of simulated acid rain on the growth and yield of agricultural crops. The system consists of three, mobile greenhouse shelters which exclude ambient rainfall and apply simulated acid rain (SAR) treatments to crops established in field plots. All aspects of the field system are controlled by a microcomputer and data acquisition system. In addition, elevated ambient levels of gaseous pollutants (e.g. O₃, SO₂, NO_x) are reduced in field plots via an air exclusion system consisting of large blowers, potassium permanganate-treated alumina filters and perforated polyethylene tubes. Gaseous pollutants can be injected into the treatment plots via the blowers.  相似文献   

Räumliche Variabilität und Verteilung von Schwermetallen in den Böden einer 1 km2 großen Modellfläche im Siegerland     

Holger Geiler  Frank Aschenbrenner  Hildegard S. Denge  Alexander Donsbach  Rüdiger Ostermann  Klaus Knoblich  Wolfgang Maurer 《植物养料与土壤学杂志》1997,160(5):603-612

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JESSE G. M. BULLOWA     

Alexander J 《Science (New York, N.Y.)》1944,99(2580):462-463

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Neuron activity related to short-term memory   总被引：39，自引：0，他引：39  

J M Fuster  G E Alexander 《Science (New York, N.Y.)》1971,173(997):652-654

Nerve cells in the monkey's prefrontal cortex and nucleus medialis dorsalis of the thalamus show changes of firing frequency associated with the performance of a delayed response test. Most cells increase firing during the cue presentation period or at the beginning of the ensuing delay; spike discharge highler than that in intertrial periods is present in some cells throughout the delay. These changes are interpreted as suggestive evidence of a role of frontothalamic circuits in the attentive process involved in short-term memory  相似文献