Ecosystem responses to channel restoration decline with stream size in urban river networks

2020 ◽  
Vol 30 (5) ◽  
Author(s):  
Peter S. Levi ◽  
Peter B. McIntyre
Keyword(s):  
Urban River ◽  
River Networks ◽  
Ecosystem Responses ◽  
Stream Size ◽  
Channel Restoration

scholarly journals Spectral and Spatial Feature Integrated Ensemble Learning Method for Grading Urban River Network Water Quality

2021 ◽  
Vol 13 (22) ◽  
pp. 4591
Author(s):  
Xiaoteng Zhou ◽  
Chun Liu ◽  
Akram Akbar ◽  
Yun Xue ◽  
Yuan Zhou
Keyword(s):  
Remote Sensing ◽  
Water Quality ◽  
Ensemble Learning ◽  
Urban River ◽  
River Networks ◽  
Spectral Features ◽  
Learning Method ◽  
Spatial Feature ◽  
Spatial Features ◽  
Quality Grading

Urban river networks have the characteristics of medium and micro scales, complex water quality, rapid change, and time–space incoherence. Aiming to monitor the water quality accurately, it is necessary to extract suitable features and establish a universal inversion model for key water quality parameters. In this paper, we describe a spectral- and spatial-feature-integrated ensemble learning method for urban river network water quality grading. We proposed an in situ sampling method for urban river networks. Factor and correlation analyses were applied to extract the spectral features. Moreover, we analyzed the maximum allowed bandwidth for feature bands. We demonstrated that spatial features can improve the accuracy of water quality grading using kernel canonical correlation analysis (KCCA). Based on the spectral and spatial features, an ensemble learning model was established for total phosphorus (TP) and ammonia nitrogen (NH3-N). Both models were evaluated by means of fivefold validation. Furthermore, we proposed an unmanned aerial vehicle (UAV)-borne water quality multispectral remote sensing application process for urban river networks. Based on the process, we tested the model in practice. The experiment confirmed that our model can improve the grading accuracy by 30% compared to other machine learning models that use only spectral features. Our research can extend the application field of water quality remote sensing to complex urban river networks.

scholarly journals Environmental filtering and spatial processes equally contributed to macroinvertebrate metacommunity dynamics in the highly urbanized river networks in Shenzhen, South China

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Zhenyuan Liu ◽  
Tingting Zhou ◽  
Yongde Cui ◽  
Zhengfei Li ◽  
Weimin Wang ◽  
...  
Keyword(s):  
South China ◽  
Community Dynamics ◽  
Environmental Filtering ◽  
Ecological Factors ◽  
Urban River ◽  
River Networks ◽  
Ecological Communities ◽  
Spatial Processes ◽  
Metacommunity Ecology ◽  
Dry Seasons

Abstract Background Disentangling the relative roles of environmental filtering and spatial processes in structuring ecological communities is a central topic in metacommunity ecology. Metacommunity ecology in the temperate river ecosystems has been well developed, while less attention has been paid to subtropical urban river networks. Here, we examined the ecological factors and seasonal difference in structuring macroinvertebrates metacommunity assembly in the subtropical urban river networks in Shenzhen, South China. Results Our results revealed that there was no significant distinction of macroinvertebrate community composition among seasons, with only the relative abundance of Mollusca and Odonata significantly differed in both wet and dry seasons. One possible explanation was that most macroinvertebrates are generally pollution-tolerant taxa characterized with nonseasonal life cycle. In addition, distance-based redundancy analysis and variation partitioning approach revealed that metacommunity was determined equally by the environmental and dispersal-related factors. Further, our results showed that, although a slight temporal variation of relative contribution, the identity and explanation power of ecological factors were different among seasons. Specifically, stronger environmental filtering structuring community dynamics was observed in the dry than wet seasons, which might be owing to higher environmental heterogeneity under a low water-flow condition. Moreover, we detected that the influence of spatial processes was stronger in the wet than dry seasons, indicating an obvious dispersal processes due to high connectivity among sites. Conclusion Overall, our results revealed that environmental and spatial factors equally explained variations of macroinvertebrate metacommunity, implying the necessity of considering dispersal-related processes structuring ecological communities in river bioassessment programs. Moreover, degraded habitat conditions and water quality were the predominant factors that affected macroinvertebrate communities, indicating the significance and feasibility of improving local abiotic conditions to sustain local biodiversity. Further, our findings revealed the importance of seasonal dynamics of these urban river networks in structuring macroinvertebrate metacommunity. Thereby, our study improves the understanding of ecological processes governing macroinvertebrate metacommunity and underlines the idea that community ecology studies should go beyond the single snapshot survey in river networks.

Historically linked residues profile of OCPs and PCBs in surface sediments of typical urban river networks, Shanghai: Ecotoxicological state and sources

2019 ◽  
Vol 231 ◽  
pp. 1070-1078 ◽  
Author(s):  
Abdul Qadeer ◽  
Sai Liu ◽  
Min Liu ◽  
Xinran Liu ◽  
Zeeshan Ajmal ◽  
...  
Keyword(s):  
Surface Sediments ◽  
Urban River ◽  
River Networks

Biological assessment of an urban river using algal indices

2006 ◽  
Vol 8 (1) ◽  
pp. 19-31 ◽  
Author(s):  
N. Jafari Ghavzan ◽  
V. R. Gunale ◽  
R. K. Trivedy
Keyword(s):  
Urban River ◽  
Biological Assessment
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