The Design and Development of a Closed Chamber for the in‐situ Quantification of Dryland Soil Carbon Dioxide Fluxes

This paper describes the design features and capabilities of a portable automated in‐situ closed chamber (ISCC) for the quantification of CO₂ fluxes in dryland soils where both photosynthetic and respiratory components may be associated with a cyanobacterial crust. The processes of CO₂ flux in dryland soils are briefly described in order to clarify the conditions that make quantification of these fluxes problematic. The instrumentation currently available for in‐situ soil CO₂ flux measurements is then reviewed demonstrating their inadequacies for the dryland environment. The ISCC described here is a member of the closed or enrichment class of soil respiration chambers. The ISCC, however, features an optical window possessing high (>90%) transmission in the photosynthetic active region (PAR) of the solar irradiance spectrum, permitting observations of photosynthesis. The ISCC possesses automatic venting and purging so that gaseous concentrations inside the chamber do not change from ambient sufficiently to significantly affect diffusion. The ISCC features both active and passive cooling employing internal solid‐state Peltier coolers and external aluminised Mylar respectively. This avoids severe disturbance of the microclimate within the chamber due to admission of high fluxes of PAR and permits in‐situ operation under a wide range of ambient field temperatures (~ ?5 to 40°C). Sensors internal to the chamber monitor temperature, relative humidity, irradiance and pressure. In this implementation the ISCC is coupled to a portable gas chromatograph (Agilent GC‐3000) to sample the chamber atmosphere. Indicative data for Kalahari Sand soils of Botswana are presented as an illustration of the general performance characteristics.     

THE DECLINE OF SUMMERFALLOW ON THE CANADIAN PRAIRIES

The largest and most economically and environmentally significant change in agricultural land use in the Canadian Prairies during the past quarter-century has been the decline of summerfallow. To understand the geographical patterns of this decline, the reasons why fallow became so widespread and important in the Prairies are examined. Moisture accumulation, nitrogen release, weed control, the proportion of cropland sown to wheat, and marketing controls appear to be the main factors, although they vary in relative importance throughout the region. Geographical patterns of decline since 1971 are largely accounted for by increasing use of manufactured fertilizers and herbicides, expanding markets, and a growing awareness of the disadvantages of fallowing. Overall, the patterns of fallow have become more closely aligned with soil moisture zones. Au cours du dernier quart de siecle le changement le plus important et le plus significatif sur le plan économique et environnemental portant sur l'usage de terre cultivable dans les prairies canadiennes a été le déclin de la jachere d'été. Afin de comprendre les patterns géographiques de ce déclin, nous examinons pourquoi la jachere est devenue s i répandue et importante dans les prairies. L'accumulation de Phumidité, le degagement de l'azote, le contrdle des mauvaises herbes, la proportion de terrains arables semes de blé et les contrdes du marché paraissent être les principaux facteurs, bien que leur importance differe d'une partie de la région à l'autre. Les patterns géographiques du déclin depuis 1971 sont largement expliqués par l'usage croissant des fertilisants artificiels, les marchés en expansion et une prise de conscience croissante des désavantages de la jachere. En somme, les patterns de jachere sont devenus plus étroitement liés aux zones d'humidité du sol.     

A red deer (Cervus elaphus L.) skeleton from seamer carrs, Cleveland, England: Provenance of the skeleton and palaeoecology of the site

A Red deer, Cervus elaphus L., skeleton from Seamer Carrs was excavated and the collagen fraction of one of the bones dated to 4330 ± 100 bp (Birm. 977). The bones were embedded in a limnic sediment that was dated to 7360 ± 120bp(Birm.882). This date was confirmed by the pollen assemblage, which indicated a Flandrian I/II chronozone age. The date of the Cervus bone is explained by its movement vertically downwards in the limnic sediment. Attention is drawn to the number of large mammalian skeletons that have been recovered from Seamer Carrs during drainage operations and subsequently, and to the mesolithic and neolithic artifacts recovered from the slopes around the Carrs.     

UV-fluorescence microscopy and the coherence of pollen assemblages in environmental archaeology and Quaternary geology

UV-fluorescence microscopy provides a powerful tool for the assessment of the coherence of pollen and organic-walled microfossil assemblages in situations where recycling or the intrusion of younger pollen is suspected. It also provides sensitive information about the thermal maturity of pollen, important for assessing whether material has been heated. Examples are given from the Palaeolithic sites at Barnham, Suffolk, UK; Stanton Harcourt, Oxfordshire, UK; High Lodge, Suffolk, UK; Niah Cave, Sarawak, Malaysian Borneo; and Holocene sites at Wadi Dana, Jordan; Milldale and Creswell, Derbyshire, UK; and Dooncarton Mountain, County Mayo, Republic of Ireland.     

Soil and organic carbon losses from varying land uses: a global meta‐analysis

Soil (SL) and organic carbon losses (SOC_L) have increased with human population and climate change linked extreme events. While SL and SOC_L are clearly associated with surface run‐off, the impact of land use is still not well understood. This article elucidates the effects of land use, surface cover, and other environmental factors on SL and SOC_L using data from 55 published studies. The overall SL (12.34 ± 2.25 Mg ha^?1 year^?1) and SOC_L (21.80 ± 0.91 g C m^?2 year^?1) suggests substantial losses of the fertile topsoil globally. Grasslands (4.19 ± 1.22 Mg ha^?1 year^?1) had 77%, 66%, and 41% lower SL than orchards, croplands, and forests, respectively, which is attributable to higher soil organic matter and surface cover. Croplands had the highest SOC_L at 22.78 ± 2.22 g C m^?2 year^?1. Natural vegetation had 98% and 70% lower run‐off and SL than did plant residue mulched plots, indicating its great potential for surface run‐off and soil erosion control. Rainfall and slope were key drivers of soil erosion, while soil surface cover, SOC, and clay content decreased. These findings improve our knowledge on soil and organic carbon losses, which is useful for fostering sustainable management of soils and natural vegetation to enhance ecosystems functionality.     

Lives Versus Livelihoods? Deepening the Regulatory Debates on Soil Fumigants in California's Strawberry Industry

Soil fumigants have been critical to the California strawberry industry's success, but they are also highly toxic to farmworkers and nearby residents. This article traces recent regulatory debates over restrictions on their use which were cast as a contest of lives and livelihoods: activists emphasized the danger of the chemicals while industry emphasized their necessity. Activists’ claims were typical of environmental justice battles that focus on disproportionate toxic exposure to marginalized populations, but I problematize that they downplayed industry concern with farmworker jobs. Drawing on Marx, Foucault and recent literature on surplus populations and disposability, I suggest that the analytical separation of lives and livelihoods is complicit in the making of disposable workers such as California farmworkers. Strategically, upholding the separation was a missed opportunity to leverage the strawberry industry's new‐found concern with farmworker employment and push for measures that protect current and future farmworker health.     

Chemical changes in buried animal bone: Data from a postmedieval assemblage

Macroscopic chemical analysis of animal bone recovered from dated excavation contexts of known pH from Castle Bromwich Hall, West Midlands, UK, allows an assessment of the rate and effects of bone decomposition, and the evaluation of current models of chemical decay. The results show great variation, and it is suggested that factors such as mechanical disturbance have a more significant effect on the differential destruction of excavated bone assemblages than chemical decay. The implications of this conclusion for the attempted reconstruction of past faunas, diet and behaviour are summarized, recommending caution in the acceptance of assemblages as unbiased samples.     

"以玉帛为草土"解

杨明照先生《抱朴子外篇校笺·嘉遯》:"草土,鄙夷之辞。""‘粪土’与此文之‘草土’,字虽有异,含义固不殊也。"庞月光先生《抱朴子外篇全译·嘉遯》注释:"草土,犹言粪土,鄙夷轻贱之辞也。"译文:"将宝玉绫罗视如粪土。"按,两位先生所言,皆与"玉帛""草土"内涵无涉。"玉帛"乃朝廷礼聘之物,"草土"乃居亲丧所用之物。"草土"指居父母大丧时,寝苫枕块,哀亲在草在土。句谓:把朝廷用"玉帛"礼聘自己为高官这种喜庆事视为居父母大丧时寝苫枕块哀亲在草在土的悲伤事。     

水硬性石灰改性土修复加固材料性能研究

针对土遗址土体坍塌、残缺等病害,为选择更好的土遗址修复加固材料,通过遗址土中添加水硬性石灰进行改性,分析检测水硬性石灰改性土修复材料的性能,并与石灰改性土材料性能进行对比分析。研究结果表明,与石灰改性土性能相比,水硬性石灰改性土修复材料夯土收缩率小、水稳定性好、抗压强度大和强度增加快、耐冻融性好;其性能优于石灰改性土材料的性能,适合土遗址土体坍塌、残损病害的修补加固,其研究成果为土遗址的保护修复加固提供科学依据。     

On the post-mortem accumulation of lead by skeletal tissues

Lead concentrations in a number of bones and soil samples taken from the same graves at the site of Bordesley Abbey were significantly correlated. Statistical analysis of the results indicated that 59% of the variation in the bone lead concentrations was due to contamination from the soil.A study of the distribution of lead in a tooth from the Romano-British site at Cirencester by fast particle activation analysis indicated that virtually all the lead was on the external surface, indicating post-mortem absorption.These results strongly suggest that lead is absorbed by skeletal tissue after death even in soils which have an alkaline pH. In the light of these findings, suggestions are made for the strategies which might be adopted for further research in this area.