Tree canopy change and neighborhood stability: A comparative analysis of Washington,D.C. and Baltimore,MD

Trees provide important health, ecosystem, and aesthetic services in urban areas, but they are unevenly distributed. Some neighborhoods have abundant tree canopy and others nearly none. We analyzed how neighborhood characteristics and changes in income over time related to the distribution of urban tree canopy in Washington, D.C. and Baltimore, MD. We used stepwise multiple regression analysis to identify strong predictors of UTC, from variables found in neighborhoods with different patterns of wealth-stability over time. We then built spatial lag models to predict variation in UTC cover, using the results of a Principal Component Analysis of the socioeconomic, demographic, and housing characteristics of the two cities. We found that: (1) stable-wealthy neighborhoods were more likely to have more, and more consistent, tree canopy cover than other neighborhood types; (2) decreases and increases in income were negatively associated with UTC in Washington, D.C. but not Baltimore, where income stability in both wealthy and impoverished neighborhoods was a significant predictor of UTC; and (3) the association of high socioeconomic status with UTC coverage varied between the two cities.     

Field Trials of,Dichloro-Diphenyl-Trichloroethane (D.D.T.) Against the Raspberry Beetle (Byturus Tomentosus Fabr.)

Summary

Crops of early leek cv. Prelina were grown in four experiments at Wellesbourne and in Cornwall from 1995 to 1997. Treatments applied included time of sowing, plant raising temperature, transplant type and covering regime. There was no effect of plant raising temperature on marketable yield or on the percentage of flowering plants. It is suggested that with cv. Prelina it is particularly the conditions during early field growth that affect the ability to flower. Larger plants at transplanting, resulting from earlier sowing or the use of peat blocks, increased the percentage of flowering plants but effects of fleece cover were variable, depending upon how close temperatures were to the optimum for vernalization, which was shown to be close to 78C. It is suggested that rather than planting early, with subsequent air temperatures near to the optimum for vernalization, which will result in high levels of bolters, it would be better to delay transplanting. Plants can then be maintained at a raising temperature that is higher than the optimum for vernalization and transplanted when there is a strong probability of air temperatures being higher. Simple models have been developed to predict first, the rate of increase of leek diameter and secondly, the rate of flower stalk extension, so that it will be possible to predict when the crop will be large enough to harvest and when flowering stalks will become unacceptably long.     

Evaluating the quality of street trees in Washington,D.C.: Implications for environmental justice

Urban street trees are part of the bundle of environmental amenities that support healthy social, economic, and environmental functions. In this study, we systematically evaluate the quality of 196,825 street trees at the US. Census tract level in Washington D.C., as well as related impacts from socioeconomic, landscape patterns and environmental factors using Ordinary least-squares (OLS) regression, geographically weighted regression (GWR) and structural equation modeling (SEM). Our results reveal that environmental and socioeconomic factors can explain most of the spatial variation of street tree quality in Washington, D.C. There is a substantial statistical negative relationship between median household income and the percent of street trees under stress, which provided the evidence of the inequities of street tree quality in Washington D.C. Higher-income neighborhoods exhibited a lower proportion of street trees under stress. In addition, the extreme summer temperature is positively associated with the proportion of street trees under stress. The quality of street trees is directly impacted by environmental and landscape pattern factors. There is also an indirect impact from socioeconomic factor toward quality of street trees. Our findings suggest that multiple variables, related to income, age, education, landscape pattern, and environment contribute to the quality of street trees in D.C. Based upon our findings, we identify strategies and insights for urban street tree management in DC to not only address environmental inequity and injustice, but also promote a more inclusive and resilient urban greenery system.     

无籽刺梨组培苗练苗及扦插基质的筛选

以组织培养所得的无籽刺梨生根幼苗为试材,在不同的基质中进行练苗,并将半年生组培苗的枝条按不同等级在不同基质中分段扦插,研究其成活率及生长情况,以期为生产中无籽刺梨的种苗生产提供理论及实践指导。结果表明:红土∶腐殖土=3∶1组成的基质为无籽刺梨组培生根苗的最佳移栽练苗基质;无籽刺梨半年生组培苗插穗在红土∶腐殖土=3∶1的基质中平均生根率最高,为78.89%,而生根数量基本不受基质差异的影响。