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171.
Natalie T Boelman Gregory P Asner Patrick J Hart Roberta E Martin 《Ecological applications》2007,17(8):2137-2144
We used airborne imaging spectroscopy and scanning light detection and ranging (LiDAR), along with bioacoustic recordings, to determine how a plant species invasion affects avian abundance and community composition across a range of Hawaiian submontane ecosystems. Total avian abundance and the ratio of native to exotic avifauna were highest in habitats with the highest canopy cover and height. Comparing biophysically equivalent sites, stands dominated by native Metrosideros polymorpha trees hosted larger native avian communities than did mixed stands of Metrosideros and the invasive tree Morella faya. A multi-trophic analysis strongly suggests that native avifauna provide biotic resistance against the invasion of Morella trees and exotic birds, thus slowing invasion "meltdowns" that disrupt the functioning of native Hawaiian ecosystems. 相似文献
172.
In wetlands, translocation of Fe and Mn from reducing to oxidizing zones creates localized enrichments and depletions of oxide minerals. In zones of enrichment, oxides cement matrix particles together into aggregates. In this paper, we describe the various Fe- and Mn-cemented features present in the 1 to 2-mm size fraction of mine-waste contaminated wetland soils of the Coeur d'Alene (CDA) River Basin in northern Idaho. These aggregates are categorized based on color and morphology. Total Fe and Mn concentrations are also reported. Distribution of the aggregates in soil profiles along an elevation transect with varying water table heights was investigated. Six distinct categories of aggregates were characterized in the 1 to 2-mm size fraction. The two most predominant categories were aggregates cemented by only Fe oxides and aggregates cemented by a mixture of Fe and Mn oxides. Iron-depleted aggregates, Fe and Mn-cemented sand aggregates, and root channel linings were also identified. The remaining aggregates were categorized into a catch-all category that consisted of primarily charcoal particles. The highest Fe content was in the root channel linings, and the highest Mn content was in the Fe/Mn cemented particles. Iron-cemented aggregates were most common in surface horizons at all sites, and root channels were most common in the 30 to 45-cm core at the lowland point, reflecting the presence of deep rooting vegetation at this site. Spatial distributions of other aggregates at the site were not significant. 相似文献
173.
The longitudinal dependence of black carbon concentration on traffic volume in an urban environment 总被引:1,自引:0,他引:1
deCastro BR Wang L Mihalic JN Breysse PN Geyh AS Buckley TJ 《Journal of the Air & Waste Management Association (1995)》2008,58(7):928-939
The purpose of this study was to evaluate the effect of traffic volume on ambient black carbon (BC) concentration in an inner-city neighborhood "hot spot" while accounting for modifying effects of weather and time. Continuous monitoring was conducted for 12 months at the Baltimore Traffic Study site surrounded by major urban streets that together carry over 150,000 vehicles per day. Outdoor BC concentration was measured with an Aethalometer; vehicles were counted pneumatically on two nearby streets. Meteorological data were also obtained. Missing data were imputed and all data were normalized to a 5-min observational interval (n = 105,120). Time-series modeling accounted for autoregressively (AR) correlated errors. This study found that outdoor BC was positively correlated at a statistically significant level with neighborhood-level vehicle counts, which contributed at a rate of 66 +/- 10 (SE) ng/m3 per 100 vehicles every 5 min. Winds from the SW-S-SE quarter were associated with the greatest increases in BC (376-612 ng/m3). These winds would have entrained BC from Baltimore's densely trafficked central business district, as well as a nearby interstate highway. The strong influence of wind direction implicates atmospheric transport processes in determining BC exposure. Dew point, mixing height, wind speed, season, and workday were also statistically significant predictors. Background exposure to BC was estimated to be 905 ng/m3. The optimal, statistically significant representation of BC's autocorrelation was AR([1:6]) x 288 x 2016, where the short-term AR factor (lags 1-6) indicated that BC concentrations are correlated for up to 30 min, and the AR factors for lags 288 and 2016 indicate longer-term autocorrelations at diurnal and weekly cycles, respectively. It was concluded that local exposure to BC from mobile sources is substantially modified by meteorological and temporal conditions, including atmospheric transport processes. BC concentration also demonstrates statistically significant autocorrelation at several time scales. 相似文献
174.
Relation of waste generation and composition to socio-economic factors: a case study 总被引:3,自引:0,他引:3
Bandara NJ Hettiaratchi JP Wirasinghe SC Pilapiiya S 《Environmental monitoring and assessment》2007,135(1-3):31-39
To develop an effective waste management strategy for a given region, it is important to know the amount of waste generated
and the composition of the waste stream. Past research has shown that the amount of waste generated is proportional to the
population and the average mean living standards or the average income of the people. In addition, other factors may affect
the amount and composition of waste. These are climate, living habits, level of education, religious and cultural beliefs,
and social and public attitudes. This paper presents the findings of a study carried out in a suburban municipal area in Sri
Lanka to determine the solid waste generation rate and waste composition based on field surveys and to determine the related
socio-economic factors. A database was developed that included information on the quantity and composition of waste generated
in a sample of households in the study area over a time period. The collected data was analysed to relate waste generation
and composition data to various socio-economic factors. Over 400 sample households were selected for the study using a stratified
random sampling methodology based on municipal wards and property values. A technique that considers both the number of households
in a particular income group (property value range) and the standard deviation of property values within a given income group
was used to determine the appropriate sample size for each municipal ward. Through category and regression analyses, the quantities
of waste and waste composition were related to several socio-economic factors. The paper describes the basis for the sample
selection, the methodology adopted for data collection, the socio-economic parameters used for the analysis, and the relationships
developed from the analysis. 相似文献
175.
内蒙古草原挥发性有机物排放通量的研究 总被引:8,自引:0,他引:8
2002年夏季,利用静态箱方法,对我国内蒙古草原生态系统挥发性有机物的排放进行了首次测量,同时观测了太阳辐射、温湿度等参数.结果表明,异戊二烯是草地挥发性有机物排放中的主要成分.异戊二烯的排放有明显的日变化、逐日变化和季节变化规律.因子分析表明,可见光辐射、温度、水汽含量是影响异戊二烯排放的主要因子,而且可见光辐射是控制其排放过程的最主要因子.根据相关分析,在考虑影响异戊二烯的排放因子时,不仅要考虑通常的影响因子--可见光辐射、温度,还要考虑水汽的作用.箱方法的使用不可避免地造成箱内外太阳辐射、温湿度等的差别,因此,必须考虑修正采样箱对挥发性有机物排放通量带来的影响.2002年夏季,异戊二烯排放通量(C)的最大值为1649.3μg/(m2·h).6、8、9月采样期间异戊二烯排放通量的日平均值分别为886.6、707.0、427.2μg/(m2·h). 相似文献
176.
Salerno Jonathan Chapman Colin A. Diem Jeremy E. Dowhaniuk Nicholas Goldman Abraham MacKenzie Catrina A. Omeja Patrick Aria Palace Michael W. Reyna-Hurtado Rafael Ryan Sadie J. Hartter Joel 《Regional Environmental Change》2018,18(3):913-928
Regional Environmental Change - Landscapes are changing rapidly in regions where rural people live adjacent to protected parks and reserves. This is the case in highland East Africa, where many... 相似文献
177.
Biotic responses to future changes in global climate are difficult to project for a particular region because the responses involve processes that operate at many spatial scales. This difficulty is exacerbated in mountainous regions, where future vegetation changes are often portrayed as simple upward displacements of vegetation zones in response to warming. We examine the scope of future responses that may occur in a mountainous area by illustrating the potential distributions of selected tree taxa in the region of Yellowstone National Park. The output of a coarse-resolution climate model that incorporated a doubling of carbon dioxide concentration in the atmosphere was interpolated onto a 5-minute grid of topographically adjusted climate data. The output was also used as input into statistical relationships between the occurrence of individual taxa and climate. The simulated vegetation changes include a combination of elevational and directional range adjustments. The range of high-elevation species decreases, and some species become regionally extirpated. The new communities have no analogue in the present-day vegetation because they mix low-elevation montane species currently in the region with extralocal species from the northern and central Rocky Mountains and Pacific Northwest. The projected climate changes within the Yellowstone region and the individualism displayed by species in their potential range adjustments are equal or greater than the changes seen in the paleoecologic record during previous warming intervals. Although the results support conservation strategies that include habitat connectivity, the magnitude of the changes may exceed the ability of species to adjust their ranges. The predicted patterns call into question the adequacy of current management objectives to cope with the scope of future changes. 相似文献
178.
Patrick Foley 《Conservation biology》1994,8(1):124-137
Managers of small populations often need to estimate the expected time to extinction Te of their charges. Useful models for extinction times must be ecologically realistic and depend on measurable parameters. Many populations become extinct due to environmental stochasticity, even when the carrying capacity K is stable and the expected growth rate is positive. A model is proposed that gives Te by diffusion analysis of the log population size nt (= loge Nt ). The model population grows according to the equation Nt+1 = Rt Nt , with K as a ceiling. Application of the model requires estimation of the parameters k = logK, rd = the expected change in n, vr = Variance(log R), and ϱ the autocorrelation of the rt . These are readily calculable from annual census data (rd is trickiest to estimate). General formulas for Te are derived. As a special case, when environmental fluctuations overwhelm expected growth (that is rd 0), Te = 2no (k - no /2)/vr . If the rt are autocorrelated, then the effective variance is vre vr (1 + ϱ)/(1 - ϱ). The theory is applied to populations of checkerspot butterfly, grizzly bear, wolf, and mountain lion. 相似文献
179.
Jean Mossman Elisabeth P. Young A. D. Patrick A. H. Fensom Marie Ellis P. P. Benson V. M. Der Kaloustian 《黑龙江环境通报》1983,3(4):347-350
We report the prenatal diagnosis of two fetuses with Sanfilippo disease type B. In both pregnancies there were excessive amounts of heparan sulphate in amniotic fluid and the activity of N-acetyl-α-D-glucosaminidase was undetectable in cultured amniotic fluid cells. The predictions were confirmed by enzyme assay of cultured skin fibroblasts from the aborted fetus or the affected infant. The disorder was excluded for two other pregnancies at risk and the predictions are considered to be correct because of the normal progress of the healthy children. 相似文献
180.
Robert L. Houghton James R. Heirtzler Robert D. Ballard Patrick T. Taylor 《Die Naturwissenschaften》1977,64(7):348-355
Plate tectonics has established the relationship of volcanism to constructional plate margins such as the Mid-Atlantic Ridge, to consuming plate boundaries such as the subduction zones comprising the Pacific “ring of fire,” and to leakage of magma along transform faults like St. Paul's Fracture Zone; however, mid-plate volcanism, which produces many oceanic islands and seamounts, is largely unexplained by plate tectonics. Studies of mid-plate volcanism have been mainly confined to oceanic islands which may be generically different from seamounts. To extend our knowledge of global tectonics and the nature of the underlying mantle source of mid-plate volcanism, we must direct our most advanced techniques to the study of seamounts and their lineaments. Herein we describe the first reported visual observations of the morphology and lithology of volcanoes comprising one such chain—the New England Seamounts. 相似文献