Long-term cropping system effects on carbon sequestration in eastern Oregon

Soil organic carbon (SOC) has beneficial effects on soil quality and productivity. Cropping systems that maintain and/or improve levels of SOC may lead to sustainable crop production. This study evaluated the effects of long-term cropping systems on C sequestration. Soil samples were taken at 0- to 10-, 10- to 20-, 20- to 30-, and 30- to 40-cm soil depth profiles from grass pasture (GP), conventional tillage (CT) winter wheat (Triticum aestivum L.)-fallow (CTWF), and fertilized and unfertilized plots of continuous winter wheat (WW), spring wheat (SW), and spring barley (Hordeum vulgare L.) (SB) monocultures under CT and no-till (NT). The samples were analyzed for soil organic matter (SOM) and SOC was derived. Ages of experiments ranged from 6 to 73 yr. Compared to 1931 SOC levels (initial year), CTWF reduced SOC by 9 to 12 Mg ha(-1) in the 0- to 30-cm zone. Grass pasture increased SOC by 6 Mg ha(-1) in the 0- to 10-cm zone but decreased SOC by 3 Mg ha(-1) in the 20- to 30-cm zone. Continuous CT monocultures depleted SOC in the top 0- to 10-cm zone and the bottom 20- to 40-cm zone but maintained SOC levels close to 1931 SOC levels in the 10- to 20-cm layer. Continuous NT monocultures accumulated more SOC in the 0- to 10-cm zone than in deeper zones. Total SOC (0- to 40-cm zone) was highest under GP and continuous cropping and lowest under CTWF. Fertilizer increased total SOC only under CTWW and CTSB by 13 and 7 Mg ha(-1) in 13 yr, respectively. Practicing NT for only 6 yr had started to reverse the effect of 73 yr of CTWF. Compared to CTWF, NTWW and NTSW sequestered C at rates of 2.6 and 1.7 Mg ha(-1) yr(-1), respectively, in the 0- to 40-cm zone. This study showed that the potential to sequester C can be enhanced by increasing cropping frequency and eliminating tillage.     

运用卫星数据和来自国家森林清查的野外数据进行全国森林变量估计

瑞典约有55%的土地面积被森林所覆盖.目前,瑞典的森林覆盖没有统一的和地理学上明晰的描述.现存的独立性数据源是Landsat TM和SPOT HRV卫星数据、地图蒙片(map mask)和森林清查样地.它们在一起,使森林变量(如材枳和林分年龄)的计算机估计成为可能.这些估计的精确度在像素水平上是低的,但在林分水平上较高.在规划木材资源应如何加以利用或出于监测目的时,这类基于栅格的森林数据对政府来说是有帮助的.本文描述了以有效成本建立森林变量估计全国数据库的生成流程.我们在林分水平上评价了瑞典西南部某地森林变量估计的精确度.结果表明,总材积估计的整体均方根误差为33%,年龄估计的整体均方根误差为23%.     

A synthesis of progress and uncertainties in attributing the sources of mercury in deposition

A panel of international experts was convened in Madison, Wisconsin, in 2005, as part of the 8th International Conference on Mercury as a Global Pollutant. Our charge was to address the state of science pertinent to source attribution, specifically our key question was: "For a given location, can we ascertain with confidence the relative contributions of local, regional, and global sources, and of natural versus anthropogenic emissions to mercury deposition?" The panel synthesized new research pertinent to this question published over the past decade, with emphasis on four major research topics: long-term anthropogenic change, current emission and deposition trends, chemical transformations and cycling, and modeling and uncertainty. Within each topic, the panel drew a series of conclusions, which are presented in this paper. These conclusions led us to concur that the answer to our question is a "qualified yes," with the qualification being dependent upon the level of uncertainty one is willing to accept. We agreed that the uncertainty is strongly dependent upon scale and that our question as stated is answerable with greater confidence both very near and very far from major point sources, assuming that the "global pool" is a recognizable "source." Many regions of interest from an ecosystem-exposure standpoint lie in between, where source attribution carries the greatest degree of uncertainty.     

The relationship between protective and risk characteristics of acting and experienced workload, and musculoskeletal disorder cases among nurses

PROBLEMS: Limited research is available on the acting (work characteristics) and experienced (perceived stress) workload of nurses. The relationship between risk and protective characteristics of work-related factors and the prevalence of musculoskletal symptoms in different body regions is also unclear. METHODS: The study was a cross-sectional design with 97 female registered nurses working in a hospital setting. Two surveys were used to document the workload exposure of the nurses. One survey consisted of 148 items aimed to measure the acting workload variables from the environment; the other survey included 33 items that were aimed to measure the nurses' experienced workload. The musculoskeletal outcomes were documented with a modified version of the Nordic Musculoskeletal Symptom Survey. RESULTS: Factor analyses revealed three factors that accounted for 56% of the total variance. Factor 1 (i.e., integrated experienced energy replenishment/expenditure) represented the psychological effects of work characteristics, effort, perceived risk, and performance. Factor 2 (i.e., acting energy replenishment/expenditure) consisted of non-physical variables of the work characteristics, while Factor 3 (i.e., acting energy expenditure) included both acting and experienced workload. Logistic regression analyses indicated that Factor 3 was significantly associated with the musculoskeletal symptoms of lower and upper back, hands/wrists, and knees/lower legs (odds ratios > 1.0). Factor 2 was significantly associated with the musculoskeletal symptoms of the upper back and knees/lower legs (odds ratios < 1.0). SUMMARY: Both the acting and experienced workloads exhibited associations with musculoskeletal outcomes in the lower back, upper back, hands/wrists, and knees/lower legs in terms of risk and protective effects.     

Use of Standardized Visual Assessments of Riparian and Stream Condition to Manage Riparian Bird Habitat in Eastern Oregon

The importance of riparian vegetation to support stream function and provide riparian bird habitat in semiarid landscapes suggests that standardized assessment tools that include vegetation criteria to evaluate stream health could also be used to assess habitat conditions for riparian-dependent birds. We first evaluated the ability of two visual assessments of woody vegetation in the riparian zone (corridor width and height) to describe variation in the obligate riparian bird ensemble along 19 streams in eastern Oregon. Overall species richness and the abundances of three species all correlated significantly with both, but width was more important than height. We then examined the utility of the riparian zone criteria in three standardized and commonly used rapid visual riparian assessment protocols—the USDI BLM Proper Functioning Condition (PFC) assessment, the USDA NRCS Stream Visual Assessment Protocol (SVAP), and the U.S. EPA Habitat Assessment Field Data Sheet (HAFDS)—to assess potential riparian bird habitat. Based on the degree of correlation of bird species richness with assessment ratings, we found that PFC does not assess obligate riparian bird habitat condition, SVAP provides a coarse estimate, and HAFDS provides the best assessment. We recommend quantitative measures of woody vegetation for all assessments and that all protocols incorporate woody vegetation height. Given that rapid assessments may be the only source of information for thousands of kilometers of streams in the western United States, incorporating simple vegetation measurements is a critical step in evaluating the status of riparian bird habitat and provides a tool for tracking changes in vegetation condition resulting from management decisions.