Search

Debris flow is a typical natural disaster in mountainous areas. Its occurrence has serious impacts on the ecological environment and the life, property safety of local people. The structure of mountain riverbed plays an important role in maintaining the ecological stability of debris flow gullies (DFGs) and improving the ecological condition. However, the effects of hydro-geomorphological processes induced by riverbed structure on local macroinvertebrates have not been well examined. A functional approach was applied to macroinvertebrate data collected in a field survey at sites with different riverbed structure to investigate the response of macroinvertebrate functional traits and environment factors to riverbed structure-induced processes. Riverbed structure was quantitatively calculated by concavity-convexity degree. The results showed that (a) Macroinvertebrates were mainly composed of individuals with the ability of avoiding risks and recovering quickly in DFGs. (b) The environmental factors affecting macroinvertebrates (i.e., average particle size, velocity, flow rate, water depth, and gradient) had a great relationship with riverbed structure. (c) Only 3 (trophic habit, attachment and drift) of the 10 benthic functional traits in the study area had a good correlation with riverbed structure. This study thus found that riverbed structure, as a complex of various environmental factors directly or indirectly affected the community structure and functional traits of macroinvertebrates in DFGs. Besides, it was more suitable for macroinvertebrates of different species to live, and more conducive to the maintenance of ecological stability when the concavity-convexity degree value was about 0.075. Because 5 environmental factors affecting macroinvertebrates were moderate when the degree of concavity was about 0.075. These results can provide scientific basis for ecological conservation and management in DFGs where eco-environment is very fragile., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

While taxonomic metrics are common indicators for assessing impact of acid mine drainage (AMD) on macroinvertebrates, functional diversity metrics are scarcely used. We tested the hypothesis that functional diversity metrics could be used as indicators for assessing impact of AMD on macroinvertebrates. Differences in both taxonomic metrics and functional diversity metrics were examined among sites with varying levels of AMD impact. AMD led to loss of sensitive functional groups and resulted in low functional diversity in the impacted sites. Functional richness, functional Shannon's index and functional Brillouin's index were significantly correlated with all key AMD parameters. Compared to taxonomic metrics, functional diversity metrics had higher correlations with most key AMD parameters. Functional diversity metrics were more informative than taxonomic metrics for assessing impact of AMD on macroinvertebrates since they were more effective at indicating mild or moderate AMD pollution. Functional Shannon's index and functional Brillouin's index were the most precise metrics. [ABSTRACT FROM PUBLISHER]

The relationships between temporal patterns of macroinvertebrate community and water physicochemical parameters were investigated in the Xiangxi River, which is the largest tributary to the Three Gorges Reservoir (TGR) in Hubei province, China. The construction of the TGR has strongly impacted the Xiangxi River watershed, but inter-annual patterns in stream macroinvertebrate communities have not been examined. We sampled water and macroinvertebrates monthly from 2004 to 2006. We assessed the persistence (similarity between years of species assemblage) and stability (similarity between years with respect to relative abundance of species in the community) of the macroinvertebrate community by the Bray--Curtis distance. The relationship between changes in water physicochemical conditions and changes in community structure were assessed with linear regression. The results showed that both the physical and chemical conditions of the water differed significantly among years. Similarly, the macroinvertebrate community structure and composition were significantly different among years. The compositional persistence was positively and significantly related to the physical condition, supporting the Habitat Templet Theory and indicating the importance of physical habitat protection. This study provides information for environmental assessment, which can be used to develop sustainable management strategies. [ABSTRACT FROM AUTHOR]

Ecological effects of climate change on terrestrial and marine ecosystems are increasingly apparent but evidence from freshwater is scarce, particularly in Asia. Using data from two subtropical Central China streams, we predicted the changes of some benthic macroinvertebrate communities under various climatic scenarios. Our results show that the average annual air temperature, in the study watershed, increased significantly ( P < 0.05) by 0.6 °C over the last 30 years (1978-2007), whereas the average annual water flow declined by 30.9 m3 s-1. Based on the winter sampling of benthic macroinvertebrates at four stream locations over last six years, we observed that macroinvertebrate abundance and Margalef diversity dropped with increasing water temperatures or decreasing smoothed sea surface temperatures (SSST). The winter macroinvertebrate abundance and biodiversity declined by 11.1% and 6.8% for every 1 °C water temperature rise. In contrast, increases in future SSST by one unit would increase winter macroinvertebrate abundance and biodiversity by 38.2% and 16.0%, respectively. Although many dominant taxa were predicted to persist when water temperatures increase by 1 °C, several scarce taxa, e.g., Orthocladius clarkei and Hippeutis umbilicalis, could be at a level of potential local extinction. Our identification of these links, between climate change and stream macroinvertebrate communities, has wide implications for the conservation of mountain stream ecosystems in the upper Yangtze River under scenarios of climate change. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Flow disturbances and conversions of land-use types are two major factors that influence river ecosystems. However, few studies have considered their interactions and separated their individual effects on aquatic organisms. Using monthly monitoring data from two streams with different land-use types ( i.e. forest and agriculture) in the subtropical Central China over three years, we accurately predicted the changes of macroinvertebrate communities under flood disturbances and land-use type conversions. The dominant taxa and main community metrics significantly declined following flash floods. Several mayflies and chironomid had rapid rates of recovery, which could reach high abundance in three months after floods. And most of the community metrics recovered more rapidly in the forested river than that in the agricultural river. Stepwise multiple regression (SMR) models were used to investigate the relationships between biotic metrics and hydrological and temporal variables. For example, SMR revealed that floods reduced the stability of benthic communities, and the length of low flow period was of considerable importance to the recovery of the fauna. Two-way ANOVA indicated that intra-annual fluctuation had more ( e.g. the total abundance and wet biomass), equal ( e.g. total richness, EPT richness, percent EPT abundance, and Margalef index), or less ( e.g. tolerant value) influence on macroinvertebrate communities than land-use types. Consequently, the effects of floods on macroinvertebrates should be taken into account when macroinvertebrates are used as indicators for assessing river ecosystem. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

• Macroinvertebrate communities were investigated in ten mountainous streams. • Indicators were proved to be efficient in discriminating environmental gradients. • Trait-based metrics responded more readily to human disturbances. The selection of suitable indicators is the key to the development of multi-metric bioassessment. Here, we examined how taxonomic and functional structures of macroinvertebrate communities responded to the environmental gradients in ten mountainous streams in the Weihe River and Hanjiang River basins, two subtropical biodiversity hotspots in central China. Our main objectives were: 1) to examine whether trait-based metrics performed better than taxonomic compositions in differentiating environmental gradients; 2) to test whether indicators (species and traits) were more efficient than entire communities in discriminating three site groups subjected to different levels of human disturbances. Our results showed that both taxonomic and functional trait compositions, including species- and trait-based indicators, were all sensitive to environmental disturbance. Particularly, the trait-based variables responded more sensitive to human disturbances. Indicator assemblages can be effective surrogates of entire communities in response to environmental changes. Traits- and indicators-based metrics should be considered as useful supplements in the existent bio-monitoring schemes in China. We argued that the combination of taxonomic and functional indicators should be implemented in bioassessment, as they reflect different aspects of environmental changes and anthropogenic disturbances. [ABSTRACT FROM AUTHOR]

Dispersal is an essential natural process that influences community assembly, yet directional dispersal through wind and water may have distinctive effects. Environmental and spatial factors jointly influence community structure, but their relative importance is anticipated to vary with spatial distance, dispersal mode, and season. Accordingly, a systemic survey was conducted in subtropical Chinese mountain lotic systems to distinguish the relative contributions of environmental control and spatial structuring upon communities of macroinvertebrates with different dispersal ability. Macroinvertebrate samples were collected from the upper reaches and five tributaries of the Hanjiang River in October 2017 (autumn) and April 2018 (spring). These macroinvertebrates were identified and classified into three dispersal groups: aquatic passive (AqPa), terrestrial passive (TePa), and terrestrial active (TeAc). Variation partitioning analyses were performed on environmental factors and different sets of spatial factors (overland dispersal: Overland, directional downwind dispersal: AEM_Wind, along watercourse dispersal: Watercourse, and directional downstream dispersal: AEM_Water). Findings showed that both environmental filtering and spatial structuring influenced the structure of macroinvertebrate metacommunities. For AqPa and TePa groups, pure environmental effects were stronger than pure spatial effects based on most distance matrices; however, in AEM_Water, the effects of spatial processes surpassed those of environmental filtering. For TeAc group, the role of environmental control and spatial structuring varied depending on different spatial models. The results also highlighted seasonal shifts in metacommunity structuring processes. Spatial structures featuring direction, especially AEM_Water, were predominant in explaining the construction of macroinvertebrate communities. This work suggests that directional dispersal should be explicitly considered when examining the structure of ecological communities. • Environmental and spatial effects on macroinvertebrate communities varied with spatial distance, dispersal mode, and season. • Seasonal variation characterized the assembly mechanisms of benthic communities. • Directional spatial processes outperformed other processes in explaining community variation. • Directional spatial processes should be highlighted in further studies of community assembly. [ABSTRACT FROM AUTHOR]