scholarly journals Environmental Pressures on Top-Down and Bottom-Up Forces in Coastal Ecosystems

Diversity ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 444
Author(s):  
Michael J. Blum
Keyword(s):  
Multiple Stressors ◽  
Negative Impact ◽  
Plant Stress ◽  
Coastal Ecosystems ◽  
Freshwater Ecosystems ◽  
Nitrogen Enrichment ◽  
Top Down ◽  
Bottom Up ◽  
Environmental Pressures ◽  
Elevated Salinity

Global change is manifesting new and potent pressures that may determine the relative influence of top-down and bottom-up forces on the productivity of plants that undergird coastal ecosystems. Here, I present a meta-analysis conducted to assess how herbivory, nitrogen enrichment, and elevated salinity influence plant productivity according to the salinity regimes of coastal ecosystems. An examination of 99 studies representing 288 effect sizes across 76 different plant species revealed that elevated salinity negatively affected productivity across all environments, but particularly in freshwater ecosystems. Nitrogen enrichment, on the other hand, positively affected productivity. In agreement with the plant stress hypothesis, herbivory had the greatest negative impact in saline habitats. This trend, however, appears to reverse with nitrogen enrichment, with maximum losses to herbivory occurring in brackish habitats. These findings demonstrate that multiple stressors can yield complex, and sometimes opposite outcomes to those arising from individual stressors. This study also suggests that trophic interactions will likely shift as coastal ecosystems continue to experience nutrient enrichment and sea level rise.

Bottom-up and top-down effects on phytoplankton functional groups in Hulun Lake, China

2021 ◽  
Vol 57 ◽  
pp. 3
Author(s):  
Chengxue Ma ◽  
Chang Zhao ◽  
Patteson Chula Mwagona ◽  
Ziyu Li ◽  
Zixuan Liu ◽  
...  
Keyword(s):  
Functional Groups ◽  
Phytoplankton Biomass ◽  
Eutrophic Lake ◽  
Positive Influence ◽  
Freshwater Ecosystems ◽  
Top Down ◽  
Bottom Up ◽  
Physical Chemical ◽  
Phytoplankton Functional Groups ◽  
Negative Effect

The debates about the extent to which phytoplankton in freshwater ecosystems are regulated by top-down or bottom-up forces have been ongoing for decades. This study examines the effects of bottom-up and top-down factors on the phytoplankton functional groups in a eutrophic lake. Phytoplankton and zooplankton were sampled and physical-chemical variables measured from May 2019 to October 2019 in Lake Hulun, China. Approximately 43 phytoplankton species were observed and grouped into 23 functional groups. For the zooplankton, about 27 species were observed and classified into 8 functional groups. The study revealed that the bottom-up effects of physical-chemical variables on some phytoplankton functional groups was stronger than the top-down effects of zooplankton. Water temperature (WT), total phosphorus (TP), total nitrogen (TN), conductivity (Cond), water transparency (SD), and dissolved oxygen (DO) significant influence the biomass of the phytoplankton functional groups. The biomass of phytoplankton functional groups was influenced positively by nutrient availability likely because nutrients influence the growth and reproduction of phytoplankton in freshwater. WT and DO had a positive influence on biomass of phytoplankton functional groups. Conversely, phytoplankton biomass revealed a decreasing trend when SD and Cond significantly increased. This study showed that zooplankton functional groups were positively correlated with phytoplankton biomass implying that the top-down control of phytoplankton by the zooplankton in the lake is not strong enough to produce a negative effect. It is evident that the zooplankton functional groups in Lake Hulun are controlled more by bottom-up force than top-down.

Top-down and bottom-up interactions in freshwater ecosystems: emerging complexities

2015 ◽  
pp. 55-85 ◽  
Author(s):  
Jason M. Taylo ◽  
Michael J. Vanni ◽  
Alexander S. Flecker
Keyword(s):  
Freshwater Ecosystems ◽  
Top Down ◽  
Bottom Up

Feral Systems as Institutional Phenomena

2017 ◽  
pp. 1454-1478
Author(s):  
Nelson King ◽  
Bijan Azad
Keyword(s):  
Information Systems ◽  
Institutional Theory ◽  
Institutional Logics ◽  
Black Box ◽  
Institutional Characteristics ◽  
Work Practices ◽  
Top Down ◽  
Bottom Up ◽  
Environmental Pressures ◽  
Social Actors

Feral systems, which sometimes manifest as computer workarounds, are recognized in the IT literature, but little attention has been paid to their persistence. The persistent reality of some computer workarounds may be traceable to discordant top-down institutional environmental pressures and bottom-up influences of day-to-day operational work. The authors build on the constructs of neo-institutional theory to de-black-box the workaround as situated practices built upon institutional logics of work practices, power to decouple by social actors, and material constraints of work. They extend the IT research on computer workarounds by casting them as emergent outcomes that exhibit institutional characteristics lending credence to the existence of feral information systems.

SYSTEMLINK - a new project on the effects of stressors across ecosystem barriers

2020 ◽  
Author(s):  
Johanna Girardi ◽  
Ralf Schulz ◽  
Mirco Bundschuh ◽  
Martin H. Entling ◽  
Eva Kröner ◽  
...  
Keyword(s):  
Aquatic Ecosystems ◽  
Multiple Stressors ◽  
Research Training ◽  
Terrestrial Ecosystems ◽  
Water Source ◽  
Training Group ◽  
Landscape Scale ◽  
Top Down ◽  
Bottom Up ◽  
Riparian Plants

<p>The propagation of environmental stressors from water (source) to land (sink) in aquatic-terrestrial meta-ecosystems, has not been intensively investigated. The other way around has been in the focus of linking terrestrial and aquatic domains. To start bridging that gap, SYSTEMLINK, a DFG Research Training Group, addresses the bottom-up and top-down mediated interactions in terrestrial ecosystems, which origin from anthropogenic impairments on aquatic ecosystems. Micropollutants (fungicides and insecticides) as well as invasive species (riparian plants and invertebrates) are considered as crucial forms of multiple stressors in disturbed aquatic ecosystems. SYSTEMLINK will examine the general hypotheses that 1) invasive invertebrates and insecticide exposure and 2) invasive riparian plants and fungicide exposure cause top-down and bottom-up mediated responses in terrestrial ecosystems, respectively. Collaborative experiments in replicated outdoor aquatic-terrestrial mesocosms (site-scale) amended by joint pot experiments (batch-scale), field studies (landscape-scale), and modelling are used to test these general and several more specific hypotheses. The experimental setups will all represent a multi-stress environment and will be derived from the landscape scale. The regular combination of several scales will allow to overcome scale-specific limitations and to ensure both cause-effect quantification and the environmental relevance of the results. Ultimately, SYSTEMLINK thrives to increase our knowledge on effect translation across ecosystem boundaries. By combining biological subsidies and biogeochemical fluxes we will be able to quantify their relative importance. Furthermore, we will closely incorporate the often separated aquatic and terrestrial research areas.</p>

Top down, bottom up and classroom reading anxiety and their effect on reading performance of undergraduate engineering students in Pakistan

2019 ◽  
Vol 11 (3) ◽  
pp. 590-603
Author(s):  
Ashfaque Hussain Soomro ◽  
Imran Khan ◽  
Muhammad Younus
Keyword(s):  
Engineering Students ◽  
Negative Impact ◽  
Reading Performance ◽  
First Year ◽  
Top Down ◽  
Bottom Up ◽  
Content Type ◽  
Undergraduate Engineering ◽  
Reading Anxiety ◽  
The Impact

Purpose The purpose of this paper is to explore EFL reading anxiety of first-year undergraduate engineering students and its effect on their reading performance in a public sector engineering university in Pakistan. It specifically aims to explore their top-down, bottom-up and classroom EFL reading anxiety. Design/methodology/approach Data for the present study were collected from 200 first-year engineering students to explore their reading anxiety. A 20-item questionnaire developed by Zoghi and Alivandivafa (2014) was used to measure students’ EFL reading anxiety, while an IELTS academic reading test was used to measure their reading performance. The data were analyzed through exploratory factorial analysis and multiple regression analysis to determine which type of reading anxiety has a significant effect on students’ reading performance. Findings It was found that the bottom-up reading anxiety and the classroom reading anxiety have a significant negative impact on the reading performance of the first-year undergraduate engineering students of a Pakistani university. However, top-down reading anxiety has an insignificant negative impact on the reading performance of university students. Research limitations/implications The data for the current study were drawn from one Pakistani public sector engineering university, and all the students were first-year undergraduates. The data were collected through a self-reported questionnaire and IELTS (academic) reading test. Some of the students may be unfamiliar with the IELTS test pattern, so their reading performance might have been affected. Practical implications Teachers should adopt such a methodology in their EFL classrooms which helps students reduce their reading anxiety. Reading texts must be selected considering the proficiency level of students, and reading strategies must be explicitly taught to reduce bottom-up and top-down reading anxieties. Teachers should create a positive learning environment in their classroom by encouraging students to make an effort to improve their reading skills in order to deal with classroom reading anxiety. Students must be explained that they should help one another rather than ridiculing each other’s reading mistakes. Differentiated instruction can also be adopted to facilitate weak readers. The teachers can provide additional/out of the class support to weak readers in order to help them deal with reading anxiety. Originality/value The EFL reading anxiety among university students in the Pakistani context has received little attention from the researchers. Furthermore, although the impact of EFL reading anxiety on EFL students’ reading performance has been explored previously, the impact of three types of EFL reading anxiety on EFL learners’ reading performance has not been adequately investigated.

scholarly journals Kajian Daerah Resiko Sanitasi Kabupaten Pekalongan (Penerapan Metode EHRA) Sudi Kasus: Kecamatan Kedungwuni

Teknika ◽  
2017 ◽  
Vol 12 (1) ◽  
pp. 33
Author(s):  
Agus Sarwo edi Sudrajat
Keyword(s):  
High Risk ◽  
Negative Impact ◽  
Development Planning ◽  
Economic Downturn ◽  
Public Attention ◽  
Top Down ◽  
Bottom Up ◽  
Sanitary Condition ◽  
Community Behavior ◽  
The Village

<p align="center"><strong><em>Abstract</em></strong></p><p>Sanitation is one of the basic urban infrastructure and requires special attention in its management. The causes of poor sanitation conditions in Indonesia are weak sanitation development planning: not integrated, misdirected, not according to needs, and unsustainable, as well as lack of public attention to clean and healthy living behavior (PHBS). The poor sanitation conditions have a negative impact on many aspects of life, ranging from the decline in quality of life, contamination of drinking water sources, increasing number of diarrhea incidents and the emergence of diseases in infants, decreased competitiveness and image, to the economic downturn. One of the efforts to improve sanitation conditions is by preparing a responsive and sustainable sanitation development plan that has principles based on actual data, at the district / city scale, prepared by the local government: from, by and for districts / cities, and incorporating a bottom-up approach up and top-down. The purpose of this study is to provide an overview of a sanitary condition including the behavior of people who are at risk for environmental health both in the household and its surroundings so that accurate initial information will be obtained according to reality and can be used as a basis for sanitation risk assessment as well as consideration for policy making sanitation sector. One method used is the EHRA is a participatory study to identify the condition of sanitation, hygiene and community behavior on a household scale. The resulting data can be used for the development of sanitation programs including advocacy in the district / city up to the village. Based on the results of the EHRA analysis, it can be concluded that Kedungwuni District has various sanitation risks. The IRS results indicate that the village with a level of risk: is less risk is 6 villages; moderate risk is 5 villages; high risk is 6 villages and very high risk 2 villages.</p><p align="center"><strong>Abstrak</strong></p><p>Sanitasi merupakan salah satu prasarana dasar perkotaan dan memerlukan perhatian yang khusus dalam pengelolaannya. Penyebab buruknya kondisi sanitasi di Indonesia adalah lemahnya perencanaan pembangunan sanitasi: tidak terpadu, salah sasaran, tidak sesuai kebutuhan, dan tidak berkelanjutan, serta kurangnya perhatian masyarakat pada perilaku hidup bersih dan sehat (PHBS). Buruknya kondisi sanitasi ini berdampak negatif di banyak aspek kehidupan, mulai dari turunnya kualitas hidup, tercemarnya sumber air minum, meningkatnya jumlah kejadian diare dan munculnya penyakit pada balita, turunnya daya saing maupun citra, hingga menurunnya perekonomian. Salah satu upaya memperbaiki kondisi sanitasi adalah dengan menyiapkan sebuah perencanaan pembangunan sanitasi yang responsif dan berkelanjutan serta memiliki prinsipberdasarkan data aktual, berskala kabupaten/kota, disusun sendiri oleh pemerintah daerah: dari, oleh, dan untuk kabupaten/kota, serta menggabungkan pendekatan <em>bottom-up</em> dan <em>top-down</em>. Adapun tujuan dalam studi ini adalah memberikan hasil gambaran dari suatu kondisi sanitasi termasuk perilaku masyarakat yang berisiko terhadap kesehatan lingkungan baik dalam rumah tangga maupun sekitarnya sehingga akan diperoleh informasi awal yang akurat sesuai realita dan dapat dipergunakan sebagai dasar dalam penilaian risiko sanitasi sekaligus pertimbangan bagi pengambilan kebijakan bidang sanitasi. Salah satu metode yang digunakan adalah EHRA yaitu sebuah studi partisipatif di untuk mengenai kondisi sanitasi dan higinitas serta perilaku-perilaku masyarakat pada skala rumah tangga.Data yang dihasilkan dapat dimanfaatkan untuk pengembangan program sanitasi termasuk advokasi di kabupaten/kota sampai dengan desa/kelurahan. Berdasarkan hasil analisa EHRA dapat disimpulkan bahwa Kecamatan kedungwuni memiliki resiko sanitasi beragam. Hasil IRS menunjukkan bahwa desa/ kelurahan dengan tingkat resiko: kurang beresiko yaitu 6desa; resiko sedang yaitu 5 desa; resiko tinggi yaitu 6 desa dan resiko sangat tinggi 2 desa.</p>

Feral Systems as Institutional Phenomena

2014 ◽  
pp. 43-67
Author(s):  
Nelson King ◽  
Bijan Azad
Keyword(s):  
Information Systems ◽  
Institutional Theory ◽  
Institutional Logics ◽  
Black Box ◽  
Institutional Characteristics ◽  
Work Practices ◽  
Top Down ◽  
Bottom Up ◽  
Environmental Pressures ◽  
Social Actors

Feral systems, which sometimes manifest as computer workarounds, are recognized in the IT literature, but little attention has been paid to their persistence. The persistent reality of some computer workarounds may be traceable to discordant top-down institutional environmental pressures and bottom-up influences of day-to-day operational work. The authors build on the constructs of neo-institutional theory to de-black-box the workaround as situated practices built upon institutional logics of work practices, power to decouple by social actors, and material constraints of work. They extend the IT research on computer workarounds by casting them as emergent outcomes that exhibit institutional characteristics lending credence to the existence of feral information systems.

scholarly journals Integrative systems approach reveals dynamics of microbiome-metal-ion axis in mesocosms representing tropical urban freshwater canal ecosystem

2020 ◽  
Author(s):  
Gourvendu Saxena ◽  
Eric Dubois Hill ◽  
Ezequiel M. Marzinelli ◽  
Shivshankar Umashankar ◽  
Toh Jun Wei ◽  
...  
Keyword(s):  
Land Use ◽  
Metal Ion ◽  
Management Practices ◽  
Natural Disturbance ◽  
Intrinsic Property ◽  
Freshwater Ecosystems ◽  
System Level ◽  
Top Down ◽  
Bottom Up ◽  
Geochemical Environment

AbstractFreshwater ecosystems of tropical urban canals systems (TrUCS), are highly dynamic and experience constant pressures from interspersed effects of land-use and rain. The dynamic nature of TrUCS ecosystems presents a unique opportunity to unravel the signature interactions between the macro-organisms (top-down), sedimentary microbial communities (SedMICs), their functioning and the geochemical environment (bottom-up). A systems level understanding of the molecular and mechanistic basis of the highly dynamic behaviour that leads to specific ecosystem outcomes, is currently lacking. Therefore, a research framework to identify the direct link between top-down and bottom-up ecological effects on SedMICs in a highly dynamic urban canal sedimentary system is needed. Here, we present a framework of integrated multi-dimensional data across system-level biotic and abiotic ecological descriptors, such as environmental variables and active SedMICs. We followed the ecosystem shifts after a natural disturbance (rain) in two different anthropogenic disturbance (land-use) regimes. Shifts in profiles of metabolically active community were conserved across different land-use types, indicating resilience to perturbation is an intrinsic property of the TrUCs ecosystem. Three distinct phases, which were dominated sequentially by autotrophy, anoxic-heterotrophy and oxic-heterotrophy, were identified within these shifts. The first two phases were influenced by the bottom-up effects of specific metal-ion combinations of nitrates and sulfates with magnesium, aluminum and iron, and the third phase was triggered by top-down influences of bioturbation. This generalized systems-level approach, which provides an ecosystem-centric understanding of TrUCS and integrates them in sustainable management practices, can also be extended to other freshwater ecosystems.

Bottom-up and top-down approaches to assess multiple stressors over large geographic areas

2000 ◽  
Vol 19 (4) ◽  
pp. 1066-1075 ◽  
Author(s):  
Scott D. Dyer ◽  
Charlotte White-Hull ◽  
Gregory J. Carr ◽  
Eric P. Smith ◽  
Xinhao Wang
Keyword(s):  
Multiple Stressors ◽  
Top Down ◽  
Bottom Up

scholarly journals Improving reading fluency and comprehension in adult ESL learners using bottom-up and top-down vocabulary training

2016 ◽  
Vol 6 (1) ◽  
pp. 111-133
Author(s):  
Rhonda Oliver ◽  
Shahreen Young
Keyword(s):  
Reading Fluency ◽  
Negative Impact ◽  
Language Instruction ◽  
Top Down ◽  
Bottom Up ◽  
English As Second Language ◽  
Adult Esl ◽  
Fluency And Comprehension ◽  
Quasi Experimental ◽  
Esl Learners

The current research examines the effect of two methods of vocabulary training on reading fluency and comprehension of adult English as second language (ESL) tertiary-bound students. The methods used were isolated vocabulary training (bottom-up reading) and vocabulary training in context (top-down reading). The current exploratory and quasi-experimental study examines the effectiveness of these methods in two intact classes using pre- and posttest measures of students’ reading fluency and comprehension. The results show that bottom-up training had a negative impact on fluency and comprehension. In contrast, top-down training positively affected fluency but had no impact on comprehension. Further, the results do suggest that fast-paced reading may potentially lead to improved comprehension. These findings have implications for the type of language instruction used in classrooms and, therefore, for teachers of adult ESL learners.

Sign in / Sign up

Export Citation Format

Share Document