نتایج جستجو برای: have variable ecosystems

تعداد نتایج: 3135311  

2017
Richard Guyette Michael C Stambaugh Daniel Dey Rose Marie Muzika

The effects of climate on wildland fire confronts society across a range of different ecosystems. Water and temperature affect the combustion dynamics, irrespective of whether those are associated with carbon fueled motors or ecosystems, but through different chemical, physical, and biological processes. We use an ecosystem combustion equation developed with the physical chemistry of atmospheri...

Journal: :Journal of environmental management 2017
Minaco Adachi Akihiko Ito Seiichiro Yonemura Wataru Takeuchi

Soil respiration is one of the largest carbon fluxes from terrestrial ecosystems. Estimating global soil respiration is difficult because of its high spatiotemporal variability and sensitivity to land-use change. Satellite monitoring provides useful data for estimating the global carbon budget, but few studies have estimated global soil respiration using satellite data. We provide preliminary i...

2009
Ian C. Burke Krishna N. Reddy Charles T. Bryson

Two greenhouse studies were conducted to investigate the variability in tolerance to a sublethal dose of glyphosate among accessions of pitted morningglory, hybrid morningglory (a fertile hybrid between pitted and sharppod morningglory), and sharppod morningglory, collected from several states in the southern United States. The first study was conducted to evaluate the variability in tolerance ...

2005
John D. Schade Javier F. Espeleta Christopher A. Klausmeier Megan E. McGroddy Steven A. Thomas Lixia Zhang

The development of ecological stoichiometry has centered on organisms and their interactions, with less emphasis on the meaning or value of a comprehensive ecosystem stoichiometry at larger scales. Here we develop a conceptual framework that relates internal processes and exogenous factors in spatiallyand temporally-linked ecosystems. This framework emerges from a functional view of ecosystem s...

this thesis attempts to investigate the effects of prelistening activities on enhancing iranian efl learners` listening comprehension. the present study investigated ways in which learners` background knowledge could be activated in order to enhance their l2 listening comprehension by limiting the number of possible text interpretations prior to listening. the experiments conducted in this study examined the effect of prior knowledge and vocabulary teaching on iranian efl learners listening comprehension. the current study has two purposes: one is to investigate the effect of background knowledge on the second language listening comprehension of iranian intermediates and the other is to determine whether second language is facilitated by the introduction of unknown vocabularies in the form of prelistening activities. to conduct the study different instruments such as listening proficiency test and four listening tests such as pre and posttests were used and various statistical processes and techniques including paired-sample t-test, and analysis of variance (anova) were used. the findings of this study supported all three hypotheses tested. differences were found between the means of preteaching vocabulary variable, the background knowledge activation variable, and mean difference between these two strategies variable. subjects scored higher when the unknown words were taught in advance. likewise, subjects scored higher when they were asked some relevant questions about the topic than on those without them. there was, in addition, a significant difference between the means of preteaching vocabulary strategy and background knowledge activation strategy. in fact, preteaching vocabulary had a better effect in enhancing the students’ listening comprehension, in comparison to background knowledge activation strategy.

پایان نامه :دانشگاه آزاد اسلامی - دانشگاه آزاد اسلامی واحد تهران مرکزی - دانشکده زبانهای خارجی 1390

this thesis attempts to investigate the effects of prelistening activities on enhancing iranian efl learners` listening comprehension. the present study investigated ways in which learners` background knowledge could be activated in order to enhance their l2 listening comprehension by limiting the number of possible text interpretations prior to listening. the experiments conducted in this stud...

Ali Johari, Hamid Salari-joo, Mohammad Reza Kalbassi,

Background: In recent years, silver nanoparticles due to their antimicrobial properties, have formed about 56% of nanoparticles global production. Since the released nanoparticles ultimately enter water ecosystems, their maximum toxic effects are magnified in aquatic ecosystems. The aim of this study is to show how salinity can decrease the toxic effects of silver nanoparticles on exposed rai...

2017
André M. Amado Fábio Roland

Microorganisms have been recognized as central to nutrient mineralization and recycling in aquatic ecosystems since Lindeman's groundbreaking work on the trophic-dynamic aspect of ecology (Lindeman, 1942). Since the seventies, the development of new analytical technologies led to important conceptual perspectives, such as the microbial loop and the microbial food web (as summarized elsewhere, e...

Journal: :iranian journal of toxicology 0
محمدرضا کلباسی mohammad reza kalbassi ph.d. student, department of fisheries, faculty science, tarbiat modares university, noor, iran حمید سالاری جو hamid salari-joo m. sc. student, department of fisheries, faculty marine science, tarbiat modares university, noor, iran علی جوهری ali johari associate professor, department of fisheries, faculty marine science, tarbiat modares university, noor, iran

background: in recent years, silver nanoparticles due to their antimicrobial properties, have formed about 56% of nanoparticles global production. since the released nanoparticles ultimately enter water ecosystems, their maximum toxic effects are magnified in aquatic ecosystems. the aim of this study is to show how salinity can decrease the toxic effects of silver nanoparticles on exposed rainb...

Journal: :Environmental management 2003
Francine M R Hughes Stewart B Rood

Floodplain forests are flood-dependent ecosystems. They rely on well-timed, periodic floods for the provision of regeneration sites and on tapered flood recession curves for the successful establishment of seedlings. These overbank flood events are described as "regeneration flows." Once floodplain forest trees are established, in order to grow they also require adequate, although variable, riv...

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