Ecological Networks Research Articles

Optimizing the ecological network of resource-based cities to enhance the resilience of regional ecological networks.

Mineral extraction in resource-based cities has caused serious damage to the original ecology, resulting in poor regional vegetation growth, reduced carbon sequestration capacity, and reduced ecosystem resilience. Especially in resource-based cities with fragile ecology, the overall anti-interference ability of the environment is relatively worse. Seeking ecological network optimization solutions that can improve vegetation growth conditions on a large scale is an effective way to enhance the resilience of regional ecosystems. This paper introduces carbon sequestration indicators and designs a differential ecological networks (ENs) optimization model (FTCC model) to achieve the goal of improving ecosystem resilience. The model identifies the patches that need to be optimized and their optimization directions based on the differences in ecological function-topology-connectivity-carbon sequestration of the patches. Finally, the resilience of the ecological network before and after optimization was compared, proving that the model is effective. The results show that the sources in the Yulin ENs form three main clusters, with connectivity between clusters relying on only a few patches. The patches in the northeastern and southwest clusters are large but their ecological functions need to be improved. After optimization, 16 new stepping stones were added, 38 new corridors were added, and the ecological function of 39 patches was enhanced. The optimized ecological network resilience was improved in terms of structure, function, and carbon sinks, and carbon sinks increased by 6364.5 tons. This study provides a reference for measures to optimize landscape space and manage ecosystem resilience enhancement in resource-based cities.

Land use is a stronger determinant of ecological network complexity than the number of trophic levels.

Land modification causes biodiversity loss and ecosystem modification. Despite many studies on the impacts of this factor, there is little empirical evidence on how it affects the interaction networks of plants, herbivores and their natural enemies; likewise, there is little evidence on how those networks change due to differences in the complexity of the communities they comprise. We analyzed the effects of land use and number of trophic levels on the interaction networks of exotic legume species and their associated arthropods. We collected seedpods from five exotic legume species (one of them invasive) in four land use types (urbanization, roadside, L. leucocephala plantation, wooded pasture) on Santa Cruz Island in the Galapagos, and obtained all arthropods that emerged from the seeds. Then, we built and analyzed the interaction networks for each land use at two community scales, each with different numbers of trophic levels: (1) three levels: plant-seed beetle-parasitoid (PSP), and (2) more than three levels: plant-seed beetle-parasitoid-predator and other trophic guilds (PSPP). Land use was more relevant than number of trophic levels in the configuration of species interactions. The number of species and interactions was highest on roadsides at PSPP and lowest in plantations at PSP. We found a significant effect of land use on connectance and interaction evenness (IE), and no significant effect of number of trophic levels on connectance, diversity or IE. The simultaneous analysis of land use and number of trophic levels enabled the identification of more complex patterns of community structure. Comparison of the patterns we found among islands and between exotic and native legumes is recommended. Understanding the structure of the communities analyzed here, as well as the relative contribution of their determinants of change, would allow us to develop conservation plans according to the dynamics of these neo-ecosystems.

Dynamic Analysis on Carbon Metabolism of the Northern Region of China Under the Background of Carbon Emission Trading Policy

The launch of the national carbon emissions trading market in China is a policy to carry out the Beautiful China initiative and to establish a low-carbon economic development system that promotes carbon emission and waste reduction. In order to detect the carbon metabolic processes of the pilot and nonpilot municipalities or provinces in the northern region of China， the theory of urban carbon metabolism and the methods of input-output analysis and ecological network analysis were introduced and used. The results showed that the direct carbon emissions of Beijing and Tianjin had decreased， but their embodied carbon emissions had increased since 2012. The direct and embodied carbon emissions of the pilot sectors in Beijing and Tianjin had the same trend； specifically， the emissions of the sectors of mining and washing of coal， extraction of petroleum and natural gas， and manufacture of non-metallic mineral products decreased significantly， but the sectors of production and supply of electric power and steam with high carbon emission increased. The same trend of the embodied carbon emission intensities of sectors with that of their embodied carbon emissions verified that the embodied added values were not growing with the promotion of the carbon emission trading market. Subsequently， the embodied carbon emission of the pilot sectors in all the municipalities and provinces of the northern region were all contributed mainly by the emissions embodied by a path length less than 6； therefore， it showed that more attention should be paid to the trade among sectors with a path length less than 6 and reducing their carbon emissions. Furthermore， from 2007 to 2012， products or service trading among sectors mostly concentrated on sectors within one municipality or province， and these products or services had the characteristics of low carbon emission. Since 2012， the integration development of the Beijing-Tianjin-Hebei urban agglomeration and the new regional economic patterns established in the northern region both promoted the trading across provinces and across sectors. This research is based on the background of the carbon emission trading policy and aims to build a methodology to identify the key actors and paths in a metabolic system. This could provide a scientific basis for regional policy implementation and regional long-term sustainable development.

An empirical assessment of whether urban green ecological networks have the capacity to store higher levels of carbon

Carbon–neutral growth is a crucial long-term climatic aim in the context of global warming. This paper introduces complex network theory and explores its potential application to achieve this goal. Specifically, we investigate the spatial and temporal distribution of nodes and sources in the ecological network, and examine whether a relationship exists between the topological index of network nodes and the landscape pattern index of ecological source areas. We also determine the contribution of nodes to the carbon stock of the entire network by exploring the correlation between the carbon stock of nodes and sources to develop an optimization strategy based on the synergistic effect of node-source carbon enhancement. Finally, we test the effect of network optimization through robustness. Our results show that: (1) The correlation topological feature index analysis reveals that the degree distribution of the node network's topological characteristics becomes dispersed and modular, exhibiting the characteristics of small-world networks according to a large clustering coefficient. The heterogeneity and extent of ecological source landscapes have increased by modularity index but remain distributed and locally fragmented; (2) According to correlation analysis, by enhancing the eccentricity of the node topology, the patch cohesion index (COHESION) of the ecological source site can maximize the contribution of the node to the enhancement of the carbon stock benefits of the source site; (3) According to the tests on the robustness of nodes and edges and the robustness of network links, network stability is improved and carbon sink capacity is enhanced. Simultaneously, the restoration and rejuvenation of ecological space through national ecological construction projects can effectively improve the carbon sink within the organized region, contributing to the carbon neutrality aim. This research gives scientific and quantifiable references for potential ecological construction projects for sustainable cities and the optimization of urban ecological space structure.

Large-scale cultural heritage conservation and utilization based on cultural ecology corridors: a case study of the Dongjiang-Hanjiang River Basin in Guangdong, China

In the field of world heritage conservation, there has been broad consensus on carrying out heritage conservation research on the basis of spatial integration and interregional and international cooperation. However, there are still many deficiencies in the integration of culture with the environment, regional economic and social development, and the regional, holistic and multimodal conservation and utilization of cultural heritage sites. In China, the Dongjiang-Hanjiang River Basin is a representative area of substantial cultural and ecological value for both Guangdong Province and the whole country. This paper uses the morphological spatial pattern analysis and the minimum cumulative resistance model to integrate cultural ecology sources and establish a cross-regional and large-scale cultural ecology network system that includes 1 main corridor, 22 important corridors and 17 secondary corridors. In addition, based on identified cultural landscape nodes and cultural ecology services, the economy of the cultural ecology corridor could be developed with large-scale co-construction, co-governance and shared working mechanisms to overcome administrative limits and realize the conservation and utilization of multimodal and large-scale heritage sites. This approach has strong theoretical and practical significance for innovative methods in cultural ecology research, as well as for new content in the research of Lingnan culture, ecosystem restoration, and the economic and social development of towns and villages. This article supplements unilateral studies of regional culture and ecology and demonstrates an in-depth application of cultural ecology theory.

Optimization of operating parameters and microbiological mechanism of a low C/N wastewater treatment system dominated by iron-dependent autotrophic denitrification

Ferrous iron (Fe2+) reduces the amount of external carbon source used for the denitrification of low-C/N wastewater. The effects of key operating parameters on the efficiency of ferrous-dependent autotrophic denitrification (FDAD) and the functioning mechanism of the microbiome can provide a regulatory strategy for improving the denitrification efficiency of low C/N wastewater. In this study, the response surface method (RSM) was used to explore the influence of four important parameters–the molar ratio of Fe2+ to NO3−-N (Fe/N), total organic carbon (TOC), the molar ratio of inorganic carbon to NO3−-N (IC/N) and sludge volume (SV, %)–on the FDAD efficiency. Functional prediction and molecular ecological networks based on high-throughputs sequencing techniques were used to explore changes in the structure, function, and biomarkers of the sludge microbial community. The results showed that Fe/N and TOC were the main parameters affecting FDAD efficiency. Higher concentrations of TOC and high Fe/N ratios provided more electron donors and improved denitrification efficiency, but weakened the importance of biomarkers (Rhodanobacter, Thermomonas, Comamonas, Thauera, Geothrix and unclassified genus of family Gallionellaceae) in the sludge ecological network. When Fe/N > 4, the denitrification efficiency fluctuated significantly. Functional prediction results indicated that genes that dominated N2O and NO reduction and the genes that dominated Fe2+ transport showed a slight decrease in abundance at high Fe/N levels. In light of these findings, we recommend the following optimization ranges of parameters: Fe/N (3.5–4); TOC/N (0.36–0.42); IC/N (3.5–4); and SV (approximately 35%).

Soil health hazards of di(2-ethylhexyl) phthalate: New perspectives on earthworms from different ecological niches DNA damage, gut microbial disruption and soil enzyme changes

Di(2-ethylhexyl) phthalate (DEHP) is perceived an emerging threat to terrestrial ecosystem, however, clear and accurate studies to fully understander ecotoxicity and underlying mechanisms of DEHP on the soil fauna remain poorly understood. Therefore, this study conducted a microcosm experiment of two earthworm ecotypes to investigate the ecological hazards of DHEP from multiple perspectives. The results showed that DEHP significantly increased the 8-hydroxy-deoxyguanosine (8-OHdG) content both in Eisenia foetida (13.76–133.0%) and Metaphire guillelmi (11.01–49.12%), leading to intracellular DNA damage. Meanwhile, DEHP negatively affected the expression of functional genes (ATP-6, NADH1, COX), which may be detrimental to mitochondrial respiration and oxidative stress at the gene level. The two earthworm guts shared analogous dominant bacteria however, the incorporation of DEHP drastically suppressed the homogeneity and diversity of the gut microbes, which further disrupted the homeostasis of the gut microbial ecological network. The keystone species in the gut of E. foetida decreased under DEHP stress but increased in the gut of M. guillelmi. Moreover, DEHP presented detrimental effects on soil enzyme activity, which is mainly associated with pollutant levels and earthworm activity. Collectively, the findings expand the understanding of soil ecological health and reveal the underlying mechanisms of the potential exposure risk to DEHP.

Impact of different grade roads on ecological networks: A case study of Fuzhou City, China.

The expansion of roads exacerbates the fragmentation of ecological networks and obstructs landscape connectivity. Scientific analysis of the impacts of different grades of roads on landscape connectivity and ecological networks is crucial for guiding road planning and ecological conservation. Based on the data of 2020 road network, land cover types, and digital elevation models, we used morphological spatial pattern analysis and circuit theory to construct ecological networks within different species dispersal distances (1, 3, 5, 10 km) in Fuzhou. We analyzed the impacts of roads of different grades (motorway, urban expressway, primary and secondary highway) on landscape connectivity at the landscape-patch-corridor scale. The results showed that at the landscape scale, overall landscape connectivity was significantly positively correlated with species dispersal distance. The motorway, urban expressway, primary and secondary highway had the lowest decline rate of overall landscape connectivity within a 10 km species dispersal range, being reduced by 15.6%, 5.3%, 1.5% and 5.2%, respectively. At the patch scale, in the comparison of roads of different grades, motorway led to the highest decline rate of patch connectivity within 1 and 5 km species dispersal range, while primary highway led to the highest decline rate of patch connectivity within 3 and 10 km species dispersal range. At the corridor scale, urban expressway led the highest increase rate of indices. The cost-weighted distance of the overall least-cost path, the ratio of cost-weighted distance to length, ove-rall effective resistance, and total corridor length within 5 km species dispersal range were increased by 43.4%, 33.2%, 57.3%, and 7.3%, respectively. As the distance of species dispersal increased, the patches with high importance were reduced from the northern, central, and northwestern regions to the northern regions, leading to a decrease in the living space of species, and the key corridors were gradually extending from the northwestern and southern regions to the central regions. Our results can guide the construction and optimization of Fuzhou's ecological network from an overall perspective, and provide a scientific basis for biodiversity conservation, ecological restoration, and road network planning under the context of limited land resource utilization.

Construction and optimization of ecological network based on morphological spatial pattern analysis and minimum cumulative resistance models in Haihe River basin

AbstractIn recent years, landscape fragmentation has become increasingly serious due to the impact of human activities. The ecological network can ensure the ecological function of the region through linearly connecting ecological corridors and effectively solving the problem of landscape fragmentation that occurs in the evolution of landscape patterns. Based on MSPA and MCR models, the article analyses the distribution and changes of landscape types in the Haihe River basin and constructs an ecological network in the study area by combining the local ecological characteristics of the basin. The network structure is optimized in the end by selecting three large stepping stones, constructing 69 internal ecological stepping stones, identifying 212 fracture points, and adding seven ecological corridors to build a point–line surface network structure with an internal and external double‐loop structure. The connectivity of the network structure is evaluated by using complex network method. It is calculated that the network connectivity performance is improved by 13.95% after optimization, which means the species exchange in the study area is closer.

Identification of priority areas for territorial space ecological restoration in arid area of Northwest China: A case study of Zhangye City in Heihe River basin.

Determining priority areas for territorial ecological restoration in the arid region of Northwest China based on the holistic protection and systematic governance is an important measure to build solid national ecological security barrier and promote the construction of territorial ecological civilization. Taking Zhangye City, a typical arid area city in Northwest China, as an example, we constructed the research framework of "ecological network-ecological sensitivities-ecological degradation" from two aspects of internal defects and external threats of ecological networks by using circuit theory and assessment methods of ecological service function importance, ecological sensitivity, and ecological degradation. We then identified the priority areas of territorial ecological restoration in northwest arid region and put forward the restoration strategies. The results showed that the priority areas of ecological restoration in Zhangye City were concentrated in the artificial shelterbelt along rivers and the plain-desert-oasis transition zone with fragile ecology and strong human interference. The ecological network of the study area included 39 ecological sources and 99 ecological corridors, and the highly sensitive and degraded areas were 1595.40 and 6.65 km2. Based on the internal defects and external threats of the ecological network, we identified 31 ecological pinch points, 7 obstacle points, and 753.56 km2 ecological source areas in the territorial spatial ecological restoration priority area. These areas were related to the connectivity of the ecological network internally and the stability maintenance of the ecosystem outwards, and were the areas to restoration in the future. Following the concept of overall protection and system restoration of territorial space, we put forward the idea of territorial space restoration by integrating internal defects and external threats of ecological network, which could provide scientific decision-making basis for comprehensive ecosystem management and territorial optimization of Zhangye City.

Exploring interactions between parasites and their hosts in the Pantanal floodplain using an ecological network approach.

The study of host-parasite interactions is essential to understand the role of each host species in the parasitic transmission cycles in a given community. The use of ecological network highlights the patterns of interactions between hosts and parasites, allowing us to evaluate the underlying structural features and epidemiological roles of different species within this context. Through network analysis, we aimed to understand the epidemiological roles of mammalian hosts species (n = 67) and their parasites (n = 257) in the Pantanal biome. Our analysis revealed a modular pattern within the network, characterized by 14 distinct modules, as well as nestedness patterns within these modules. Some key nodes, such as the multi-host parasites Trypanosoma cruzi and T. evansi, connect different modules and species. These central nodes showed us that various hosts species, including those with high local abundances, contribute to parasite maintenance. Ectoparasites, such as ticks and fleas, exhibit connections that reflect their roles as vectors of certain parasites. Overall, our findings contribute to a comprehensive understanding of the structure of host-parasite interactions in the Pantanal ecosystem, highlighting the importance of network analysis as a tool to identifying the main transmission routes and maintenance of parasites pathways. Such insights are valuable for parasitic disease control and prevention strategies and shed light on the broader complexities of ecological communities.

Floristic diversity of patches generated by protected Ficus ‘trees outside forests’ in agricultural landscapes in Madagascar

AbstractFicus trees play an important role as key species in both ecological and sociocultural networks in Madagascar. This study focused on species of isolated Ficus growing in agricultural areas adjoining a forest corridor linking the Ranomafana and Andringitra National Parks in east‐central Madagascar, with the aim of understanding the structural and floristic characteristics of the vegetation regenerating under these Ficus ‘trees outside forests’. Two main aspects were studied: (1) the characteristics of the habitats under the crown of isolated Ficus species (Ficus tiliifolia, Ficus reflexa and Ficus lutea), and (2) the specific structure and composition of the vegetation under these Ficus trees: minimum area, species richness, floristic regularity, diversity and similarity, biological type, vegetation type, proportion of annual and herbaceous species, and seed dispersal methods. The results indicate that each of these three Ficus species has its own community composition. The vegetation under F. reflexa is a shrubby formation dominated by autochorous and zoochorous species located on high slopes with a minimum area of 6–12 m2. The vegetation under F. lutea is a highly anthropized herbaceous formation dominated by autochorous species located on high slopes at an altitude of 1150–1200 m, with a southwest exposure and a minimum area that ranges from 6 to 9 m2. Under F. tiliifolia, different types of plant formations are found in different topographic positions: herbaceous, shrubby or tree‐like, with different modes of seed dispersal.

Construction and stability evaluation of ecological networks in the Loess Plateau

Enhanced and optimized ecological security patterns in ecologically fragile areas are conducive to promoting their sustainable development. A valuable strategy for achieving multi-dimensional coexistence and stability of regional functions is constructing ecological networks and optimizing them. Given its susceptibility to human activities and climate change, enhancing the ecological security pattern of the Loess Plateau is particularly crucial. This study selects nine indicators from natural and human activity perspectives and constructs an ecological network using MCR and gravity models. Then, complex network analysis is performed to examine the ecological network topology and stability under deliberate attacks and random failures in the Loess Plateau. The results indicate that ecological sources are primarily located in the central and northern regions of the Loess Plateau, and the links adhere to the proximity effect theory, displaying an inverse relationship with the spatial distance separating the sources. Both preferential attachment and a power-law distribution are observed in the degree distribution of the ecological network. Additionally, deliberate attacks and random fault simulations lead to a significant decrease in both connectivity and transmission efficiency of the ecological network. The failure of hub nodes exerts a diverse range of influences on the ecological network. This study enhances our understanding of ecosystem interactions and presents crucial insights for ecological conservation and restoration strategies.

Study on the Characteristics of Ecological Network and Critical Areas of Ecological Restoration in Hebei-Tianjin Coastal Wetlands

Study on the Characteristics of Ecological Network and Critical Areas of Ecological Restoration in Hebei-Tianjin Coastal Wetlands

Integrating pattern, process, and function in urban landscape ecological network planning: A case study of Harbin central city

Scientific planning of landscape ecological networks can promote the overall improvement of urban ecosystems, but the current basis on single index and simple landscape ecological network extraction is not enough to support sustainable urban development. Comprehensively understanding the mechanism of landscape ecosystem operation, this study firstly constructed an urban landscape ecological health (LEH) assessment model integrating pattern, process, and function. Taking Harbin central city as the study area, conducting a LEH practical assessment to provide a scientific basis for its landscape ecological network planning. Secondly, the principal component analysis (PCA), minimum cumulative resistance (MCR) model, and hydrological analysis were applied to extract the landscape ecological network. Finally, introducing complex network theory to optimize the network and determine key ecological nodes. The results indicated that (1) The LEH index of Harbin central city decreased from 0.481 to 0.446 from 2011 to 2020, with significant spatial differentiation. (2) 50 source landscapes and 8 sink landscapes were identified, with fewer ecological corridors, 50 source-type ecological nodes and 28 weak-type ecological nodes were selected. (3) Based on the LDF strategy of complex network theory, there were 14 additional ecological corridors, the connectivity and resilience of the landscape ecological network were greatly enhanced, and eight key ecological nodes were identified. (4) The plan presented a spatial pattern consisting of “three rings, four pieces, eight cores, and multiple corridors”, which can maintain the sustainable development of the urban ecosystem. In addition, this study aims to propose a more scientific and efficient landscape ecological network planning framework to provide new ideas for the ecological construction of the central city areas, which are the most profoundly urbanized in the world.

Easement of forests and forest land for the growing of perennial crops - the analysis of (non)functionality regarding the ecological network and ecosystem functions

By the Government's decisions from the period 2004 to 2013, a significant amount of state forests and forest land was eased for the growing of perennial crops (vineyards and olive yards) on a total surface of 24,310.24 ha throughout the state. Although greatly opposed by forestry professionals, since a vast amount of private agricultural land in the state is not utilized due to unresolved proprietary issues, these surfaces have become agricultural land by coming into force from the Forest Act of 2014. In case these dedicated surfaces are not put into function, the amount of non-utilized agricultural land is increasing and so is the danger from forest fires, and loss of biological and landscape diversity. On the other hand, if all these surfaces were utilized, a significant adverse impact on the ecological network would occur because on many ecological network sites more than 1% of the dedicated area consists of target habitat types (mostly maquis). The purpose of this paper is, to use GIS tools and analysis of the so-far signed easement contracts, to determine what amount of dedicated surfaces were utilized and point out the failure and environmental dangers that may arise from these decisions which can still be revoked, and the affected area can be brought back into the forest area of the Republic of Croatia, i. e. sustainable forest management can still be reinstated and forest functions restored.

Synergies between biodiversity conservation and drinking water protection in an agriculture dominated landscape – Case study of the Lower Savinja Valley in Slovenia

The growing world population and global market competition are putting pressure on high-yield food production, reducing the space available for low-intensity agricultural practices that support high biodiversity. In search of synergies between different environmental policy instruments, the potential of drinking water protection zones (WPZ) for high nature value (HNV) farmland conservation and connectivity in the Lower Savinja Valley in Slovenia was examined. In drinking water protection zones, restrictions of fertilizer and pesticide use are enforced, which have demonstrated beneficial effects on biodiversity. Overall, HNV farmland covered 25.8% of the area, of which 6% was protected in almost equal proportions by Natura 2000 sites and WPZ. Zonation prioritization assigned higher average scores to cells in WPZ compared to Natura sites and unprotected areas indicating high value of WPZ for HNV connectivity. The proportion of WPZ receiving the highest Zonation prioritization scores ranged from 23% to 70% depending on connectivity scale. Simulation of conversion of arable to HNV farmland on WPZ added 58.2 ha, and increased overall HNV farmland cover in the Lower Savinja Valley from 25.8% to 26.3%, further reinforcing the importance of WPZ for connectivity. Drinking water protection zones under different levels of protection cover approximately 20% of the territory of Slovenia. Given their large extent, we suggest that when planning for HNV farmland conservation and ecological networks within intensive agriculture dominated landscapes, WPZ should be evaluated for their potential and integrated into planning. Analysis focused on the spatial configuration of HNV farmland but lacked information on habitat quality, species presence and management practices in WPZ. Further studies of the effect of WPZ management restrictions on biodiversity are needed.

Deciphering the carbon and nitrogen component conversion in humification process mediated by distinct microbial mechanisms in composting from different domestic organic wastes.

This study aimed to compare the process of maturity and humus fraction evolution as well as bacterial community dynamics in composting from different domestic organic wastes (food waste (FW), and vegetable waste (VW)) and decipher the key biotic influencing factors of humic acid formation through correlation analysis and ecological network. The results showed that organic carbon components in FW with high ratio of soluble organic carbon and hemicellulose were more easily to be degraded in composting compared to VW. After 30days of composting, the content of HA-C generated by VW was 35.41%, higher than 29.01% of FW, and the growth rate of HA-C generated was 38.42% and 28.34%, respectively. PARAFAC analysis showed that the structure of HA generated in VW was more complex, and the proportion of humic acid-like components (C3 + C4) was 60.32%, while FW only accounted for 43.86%. However, the evolution growth rate of aromatic components in HA in FW was 26.88% in 30days of compost, which was higher than 15.17% in VW. High-throughput sequencing indicated that Lactobacillus was the initial dominated genera in composting from different domestic wastes. Thermobifida, Thermovum, and Pusillimas as well as Aeribacillus were core bacterial genera that promoted the humification process in FW and VW, respectively. Network analysis showed that there was higher bacterial interacted connection degree and complexity in FW compared to VW. This study was of great significance for optimizing organics conversion and humification efficiency of household waste composting.

Temporal profiling of sediment microbial communities in the Three Gorges Reservoir Area discovered time-dissimilarity patterns and multiple stable states

Microbial communities play vital roles in cycling nutrients and maintaining water quality in aquatic ecosystems. To better understand the dynamics of microbial communities and to pave way to effective ecological remediation, it's essential to reveal the temporal patterns of the communities and to identify their states. However, research exploring the dynamic changes of microbial communities needs a large amount of time-series data, which could be an extravagant requirement for a single study. In this research, we overcame this challenge by conducting a meta-analysis of years of accumulations of 16S rRNA high-throughput sequencing data from the Three Gorges Reservoir Area (TGRA), an ecological and environmental hotspot. For better understanding the microbial communities time-dissimilarity dynamics, three microbial communities time-dissimilarity patterns were hypothesized, and the linear pattern in the TGRA was validated. In addition, to explore the stability of microbial communities in the TGRA, two alternative stable states were revealed, and their differences in community richness, alpha diversity indices, community composition, ecological network topological properties, and metabolic functions were demonstrated. In short, two states of microbial communities showed distinct richness and alpha diversity indices, and the communities in one state were more dominated by Halomonas and Nitrosopumilaceae genera, facilitating nitrogen cycling metabolic processes; whilst the main genera of the other state were Bathyarchaeia and Methanosaeta, which favored methane-related metabolism. Moreover, different studies and environmental differences between mainstream and tributaries were attributed as the potential inducing factors of the state division. Our study provides a comprehensive insight into the dynamics and stability of microbial communities in the TGRA, and a reference for future studies on microbial community dynamics.

Trait‐matching models predict pairwise interactions across regions, not food web properties

AbstractAimFood webs are essential for understanding how ecosystems function, but empirical data on the interactions that make up these ecological networks are lacking for most taxa in most ecosystems. Trait‐based models can fill these data gaps, but their ability to do so has not been widely tested. We test how well these models can extrapolate to new ecological communities both in terms of pairwise predator–prey interactions and higher level food web attributes (i.e. species position, food web‐level properties).LocationCanada, Europe, Tanzania.Time PeriodCurrent.Major Taxa StudiedTerrestrial vertebrates.MethodsWe train trait‐based models of pairwise trophic interactions on four independent vertebrate food webs (Canadian tundra, Serengeti, alpine south‐eastern Pyrenees and Europe) and evaluate how well these models predict pairwise interactions and network properties of each food web.ResultsWe find that, overall, trait‐based models predict most interactions and their absence correctly. Performance was best for training and testing on the same food web (AUC > 0.90) and declined with environmental and phylogenetic distances with the strongest loss of performance for the tundra‐Serengeti ecosystems (AUC > 0.75). Network metrics were less well‐predicted than single interactions by our models with predicted food webs being more connected, less modular, and with higher mean trophic levels than observed.Main ConclusionsTheory predicts that the variability observed in food webs can be explained by differences in trait distributions and trait‐matching relationships. Our finding that trait‐based models can predict many trophic interactions, even in contrasting environments, adds to the growing body of evidence that there are general constraints on interactions and that trait‐based methods can serve as a useful first approximation of food webs in unknown areas. However, food webs are more than the sum of their parts, and predicting network attributes will likely require models that simultaneously predict individual interactions and community constraints.