The colonisation of leaf litter by Chironomidae (Diptera): The influence of chemical quality and exposure duration in a subtropical stream     

Cristiane Biasi  Alan M. Tonin  Rozane M. Restello  Luiz U. Hepp 《Limnologica》2013,43(6):427-433

This study tested the hypothesis that the community composition of Chironomidae will change according to the duration of the exposure of plant leaves in a subtropical stream. In addition, we expected the chemical quality of the detritus to affect the association of Chironomidae with decaying plant materials. The chironomid colonisation of leaf litter from Campomanesia xanthocarpa and Sebastiania brasiliensis was assessed in a subtropical Atlantic forest stream. Litter bags containing leaves from these two species were incubated in the stream for 22 days. We identified 7245 invertebrates associated with the leaf detritus of both plant species (5110 were Chironomidae, 70.7% of the total). Thirteen genera of Chironomidae were identified, with Rheotanytarsus, Thienemanniella and Corynoneura the most abundant (94% of all Chironomidae collected). Chironomidae assemblages changed with the duration of incubation in the stream. The dissimilarity and the functional composition of the Chironomidae communities were related to the chemical composition of the detritus. The chemical components that best explained the composition of the fauna were tannins, the C:N ratio, calcium, and magnesium. However, the functional feeding groups were explained by the chemical variables organic matter and C:N. This study found that the exposure time of the detritus and therefore its level of degradation and chemical composition are important factors determining the characteristics of the Chironomidae assemblage in subtropical streams.  相似文献   

Statistical significance testing for the association of magnetometer records at high-, mid- and low latitudes during substorm days     

I. Maslova  P. Kokoszka  L. Zhu 《Planetary and Space Science》2010,58(3):437-445

In recent years, the interaction of the auroral substorms with the equatorial and mid-latitude currents has been the subject of extensive research. We introduce a new statistical technique that allows us to test at a specified significance level whether such a dependence exists, and how long it persists. This quantitative statistical technique, relying on the concepts and tools of functional data analysis, uses directly magnetometer records in one minute resolution, and it can be applied to similar geophysical data which can be represented as daily curves. It is conceptually similar to testing the nullity of the slope in the straight line regression, but both the regressors and the responses are curves rather than points. When the regressors are daily high latitude H-component curves during substorm days and the responses are daily mid- or low latitude H-component curves, our test shows significant dependence (the nullity hypothesis is rejected) which exists not only on the same UT day but also extends into the next day for strong substorms.  相似文献   

Herbage Production and Species Richness in Sub-alpine Grasslands of Different Soil Parent Material in Northern Greece     

MPOKOS J.Panagiotis  YIAKOULAKI D.Maria  PAPAZAFEIRIOU Z.Agapi  SGARDELIS Stefanos  ALIFRAGIS Dimitrios  PAPANIKOLAOU Konstantinos 《山地科学学报》2014,(6):1579-1592

Several abiotic and biotic factors were investigated as possible predictors of local species richness in two sub-alpine grasslands of Jenna and Belles Mountains in Northern Greece.For species richness modelling a hierarchical modelling framework based on generalized additive models was adopted.The two sub-alpine grasslands differed in aspect,altitude and soil parent material（volcanic origin,mostly trachyte,and andesite（TA） for Jenna and metamorphic rocks,mostly gneiss（G） for Belles）.12 fenced squared plots,16 m2 each,were used per grassland,where soil properties,herbage production,species presence and cover of grasses,legumes and forbs were estimated.Mean herbage production was significantly affected by slope and altitude,soil K content and floristic composition as expressed by an ordination axis.Soil p H,floristic composition and average herbage production were significant predictors of forbs and total species richness.For the former,soil N content and for the latter the occurrence of Agrostis capillaris,were also included as significant terms in the predictive model.Thepredictors for grasses species richness were N content,having a positive effect,and average herbage production.In all cases higher species richness was predicted for intermediate values of average herbage production.Differential responses were found between forbs and grasses.The predictors of their species richness were different while for the case of the common predictor（N） the responses of the two groups were also different（grasses species numbers increase and forbs species numbers decreased with increasing N）.Maximum species richness of grasses was observed at relatively low production levels while forbs species richness maximized at relatively high production levels.  相似文献   

Seasonal patterns of tidepool macroalgal assemblages in the North of Portugal. Consistence between species and functional group approaches     

M. Rubal  P. Veiga  R. Vieira  I. Sousa-Pinto 《Journal of Sea Research》2011,66(3):187-194

Macroalgae are useful organisms to monitor the environmental quality and to detect impacts due to anthropogenic activities. However, it is very important to identify the scales of variation in natural assemblages, particularly for the detection of environmental impacts. Otherwise, changes due to anthropogenic impacts may be confused with differences due to natural temporal variability. Another important task is to determine the appropriate level of taxonomical effort needed to detect changes in the assemblage structure. Many taxonomical surrogates, at higher taxonomic levels than that of species, have been proposed but, the consistence in space and time of the results produced by surrogates with those obtained at specific level should be tested. The objectives of this study are to identify the seasonal patterns of tidepool macroalgal communities using objective procedures and to test the consistence between the patterns obtained considering data at the species level and functional groups. Results showed that the seasonal pattern obtained using functional groups and species was consistent. Tidepool macroalgal assemblages showed a seasonal pattern with significant differences between spring–summer and autumn–winter. This pattern can be explained by changes in environmental variables and the seasonal development of the dominating species. Ulva spp. and the non-indigenous species Grateloupia turuturu were the species responsible for this pattern due to their high seasonality in terms of biomass. Finally, the abundance and species diversity within the corticated functional group was proposed as indicator of environmental impacts due to its relatively constant abundance and its sensitivity to environmental impacts.  相似文献   

Changes in vegetation structure induced by domestic grazing in Patagonia (Southern Argentina)     

A. Cesa  J.M. Paruelo 《Journal of Arid Environments》2011,75(11):1129-1135

We analyzed the structural differences associated with grazing exclusion on vegetation by studying 24 grazed-ungrazed paired sites in Patagonia (Argentina). Our objectives were to evaluate the effect of grazing on plant species composition, plant diversity, the relative abundance of plant functional types, and the vertical and horizontal structure of the plant community. This study across the shrub-grass steppes of Patagonia highlights some important characteristics of the vegetation response to a major disturbance factor we show that shrub encroachment is not a generalized response of the steppe to grazing. Grazed areas presented lower richness and diversity than exclosures. Physiognomic changes (as describe by relative abundance of plant functional types) were less important than those observed at the species level. These results shown that the status of the shrub-grass steppes of the Occidental district of Patagonia can not be characterized in terms of contrasting physiognomic states as in the case of the grass steppes of the Subandean district. Forbs and a few mesophytic and xerophytic grasses are the key elements to identify the condition of the steppe. Monitoring programs should focus on the relative abundance of these components.  相似文献   

Forms and sources of place attachment: Evidence from two protected areas     

《Geoforum》2014

Sense of place is a widely researched concept that has been used to describe and analyze people–place relationships. However, there is no consensus regarding the forms of place attachment, the relative importance of the sources for such attachments, or the spatial extent of place formation. The purpose of the paper is to contribute case examples of sense of place for significant natural areas, thereby adding to the body of evidence that explicates the diverse sources and forms of place attachment. Using content analysis of qualitative stakeholder interviews, we identify these dimensions of place attachment for two nationally significant Australian natural areas. Our data support a tripartite structure for sense of place comprising affective, functional and cognitive forms of attachment. We also examine the extent to which these place attachments are localized on the study sites and/or spatially generalized across sites possessing the same sources of place formation. Our case studies provide evidence for both localized and generalized senses of place. Localized place attachments had affective and functional components, respectively founded on social and biophysical sources. Generalized senses of place comprised functional and cognitive components, with appreciation of historical values of these places key to the formation of the latter. Our results indicate the spatial diversity of place attachments for protected areas and their social, cultural and biophysical sources.  相似文献   

液核自由运动的变分方法   总被引：2，自引：0，他引：2       下载免费PDF全文

徐建桥  孙和平  傅容珊 《地球物理学报》2004,47(1):61-74

从流体静力平衡地球的弹性-引力运动动量方程出发,以角动 量方程控制弹性地幔、液态外核和弹性内核之间的相对转动,在球对称近似下考虑了地幔和 内核对液核边界扰动的形变响应,并以此作为液核边界运动的约束条件．根据地球简正模对 称性的一般特征,建立了自转、非黏性、椭球分层流体外核自由振荡运动的变分原理并给出 了相应的泛函．  相似文献   

氟利昂C₂Cl₂F₄分子的光谱及解离动力学研究     

何仲福  李凌昊  刘玉柱  罗礼海  王亚丽  秦朝朝 《南京气象学院学报》2016,8(2):181-185

采用密度泛函B3LYP理论对氟利昂C₂Cl₂F₄ (F-114)在6-31G++(d,p)基组水平上进行分子结构优化、红外光谱计算,理论计算所得结果与实验结果基本吻合.此外又通过从头算CIS方法计算了C₂Cl₂F₄及其离子的低激发态,将所得分子低激发态的键长、键角及二面角等参数进行了对比分析,并得到了C₂Cl₂F₄分子的UV-Vis光谱和分子前线轨道,最后对C₂Cl₂F₄⁺离子的低激发态光解离动力学进行了分析.  相似文献   

浅议房产测绘制图、面积分摊系统的开发     

陈宪章  程静 《现代测绘》2007,30(5):34-35

本文针对房屋分层分户面积测算特点，设置三个级别功能模块及流程，运用灵活方便的绘图与编辑功能，采集面积自动校验功能及合理的分摊方法、步骤，科学合理地开发出一套方便实用，面积分摊计算和管理系统。  相似文献   

Functional Community Organization of Macroinvertebrates in Lotic Habitats of the Plitvice Lakes Funktionelle Organisation der Makroinvertebraten-Gemeinschaft in den lotischen Habitaten der Seen von Plitvice     

I. Habdija  B. Primc-Habdija  I. Belini&#x; 《洁净——土壤、空气、水》1994,22(2):85-92

The community and trophic structure of benthic macroinvertebrates were studied in different types of habitats in the karstic Plitvice Lake system located in the NW Dinarid mountains (Croatia). The spatial distribution of functional macroconsumer groups shows that longitudinal community functional organization doesn't correspond with the River Continuum Concept (RCC) hypothesis. Collector guilds were the most abundant functional feeding groups at all the sites analyzed. The domination of shredders was found only in habitats in the source areas of the supply streams. The disturbed longitudinal community functional organization is caused by a discontinuum in the gradient of physical factors which is a result of the geomorphological origin of travertine barriers along the hydrosystem.  相似文献