Effect of Hydrological Connectivity on Soil Carbon Storage in the Yellow River Delta Wetlands of China

Hydrological connectivity has significant effects on the functions of estuarine wetland ecosystem.This study aimed to examine the dynamics of hydrological connectivity and its impact on soil carbon pool in the Yellow River Delta,China.We calculated the hydrological connectivity based on the hydraulic resistance and graph theory,and measured soil total carbon and organic carbon under four different hydrological connectivity gradients(Ⅰ0‒0.03,Ⅱ0.03‒0.06,Ⅲ0.06‒0.12,Ⅳ0.12‒0.39).The results showed that hydrological connectivity increased in the north shore of the Yellow River and the south tidal flat from 2007 to 2018,which concentrated in the mainstream of the Yellow River and the tidal creek.High hydrological connectivity was maintained in the wetland restoration area.The soil total carbon storage and organic carbon storage significantly increased with increasing hydrological connectivity fromⅠtoⅢgradient and decreased inⅣgradient.The highest soil total carbon storage of 0‒30 cm depth was 5172.34 g/m^(2),and organic carbon storage 2764.31 g/m^(2)inⅢgradient.The hydrological connectivity changed with temporal and spatial change during 2007‒2018 and had a noticeable impact on soil carbon storage in the Yellow River Delta.The results indicated that appropriate hydrological connectivity,i.e.0.08,could effectively promote soil carbon storage.

Evolution characteristics of hydrological connectivity pattern of marsh wetland in Naoli River Basin

As an important indicator of the structural and functional stability of wetland landscapes,hydrological connectivity plays an important role in maintaining the stability of wetland ecosystems.Large-scale human activities have led to significant changes in the hydrological connectivity pattern of wetlands in Naoli River Basin since 1950 s.Combined with the availability of wetland habitat and the spreading capacity of aquatic birds,hydrological connectivity indices of marsh wetlands were calculated in the studied area,and the temporal and spatial changes were analyzed from 1950 s to 2015.The results indicate that:(1)the hydrological connectivity index of the marsh wetlands shows a growth trend with increasing distance threshold.All patches of marsh wetlands linked together when the distance threshold reached 35--40 km;(2)the optimal distance of hydrological connectivity is about 10 km for marsh wetlands of whole Naoli River Basin;(3)the total hydrological connectivity of marsh wetlands decreased in the Naoli River Basin from 1950 s to 2015.Although the hydrological connectivity index increased after 2005,the fragmentation of the landscape has not been improved.The analysis of the wetland hydrological connectivity can provide a scientific basis for the ecological restoration and protection of the wetland in the Naoli River Basin.

Surface storm flow prediction on hillslopes based on topography and hydrologic connectivity

Background:Hillslopes provide critical watershed ecosystem services such as soil erosion control and storm flow regulation through collecting,storing,and releasing rain water.During intense rainstorms,rainfall intensity and infiltration capacity on the hillslope control Hortonian runoff while the topographic attributes of the hillslope(e.g.,slope,aspect,curvature)and the channel network define the structural hydraulic connectivity that determines how rapidly excess water is transferred.This paper discusses literature on the link between topographic attributes and hydrologic connectivity and demonstrates how this link can be used to define a parsimonious model for predicting surface runoff during high intensity rainfall.Main text:First,we provide a topographic characterization of the hillslope necessary to determine the structural hydrologic connectivity of surface flow based on existing literature.Subsequently,we demonstrate a hydrologic surface response model that routes the geomorphologic unit hydrograph(GIUH)through a spatial domain of representative elementary hillslopes reflecting the structural hydrologic connectivity.Topographic attributes impact flow and travel time distributions by affecting gravitational acceleration of overland flow and channel,solar irradiance,flow deceleration by vegetation,and flow divergence/convergence.Conclusions:We show with an example where we apply the GIUH-based model to hypothetical hillslopes that the spatial organization of the channel network is critical in the flow and travel time distribution,and that topographic attributes are key in obtaining simple yet accurate representations of hydrologic connectivity.Parsimonious GIUH models of surface runoff that use this hydrologic connectivity have the advantage of low data requirements,being scalable and applicable regardless of the spatial complexity of the hillslope,and have the potential to fundamentally improve flood forecasting tools used in the assessment of ecosystem services.

The frontier evolution and emerging trends of hydrological connectivity in river systems:a scientometric review

With the intensification of climate change and human activities,the watershed ecosystem is seriously fragmented,which leads to the obstruction of hydrological connectivity,and further causes the degradation of the ecosystem.As the value of wetlands continues to be exploited,hydrological connectivity becomes increasingly significant.In this paper,the characteristics and development of hydrological connectivity research from 1998 to 2018 were analyzed through the scientometric analysis based on Web of Science database.CiteSpace,an analytical software for scientific measurement,is used to visualize the results of the retrieval.The analysis results of co-occurrence,co-operative and co-cited network indicate that the hydrological connectivity is a multidisciplinary field which involves the Environment Science and Ecology,Water Resources,Environmental Sciences,Geology and Geosciences.According to Keyword cooccurrence analysis,ecosystem,floodplain,dynamics,climate change and management are the main research hotspots in each period.In addition,the co-cited analysis of references shows that“amphibians”is the largest cluster of hydrological connectivity,and the“channel network”is the most important research topic.It is worth noting that the“GIWS”(Geographically Isolated Wetlands)is the latest research topic and may be a major research direction in the future.

Rehabilitation and improvement of Guilin urbanwater environment: Function-oriented management

Economicdevelopment and population growth havedeeplydamaged the urbanwater environment of Guilin City, China. Main problems involved structuraldamage and functionaldeterioration of the urbanwaters. An integrated technical schemewasdeveloped to rehabilitate the urbanwater environment and to enhance thewaters＇ functionsduring 1998-2008. Improvement ofwaters＇ functions includedwater system reconstruction,water pollution control,water safety assurance, and aquatic ecological restoration. Thewater systemwas reconstructed to connectdifferentwaters and cleanwater supplies to the lakes. Moreover,water pollutionwas controlled to improvewater quality by endogenous pollutant elimination and extraneous pollutant interception. In addition, ecological measures put in place serve to enhancewater system functions and better benefit both nature and humans. The project has brought about sound ecological, economic and social benefits in Guilin City,which can potentially be extended to similar cities.

Soil particle and moisture-related factors determine landward distribution of bacterial communities in a lateral riverside continuum of the Xilin River Basin

Continuous landscape components along the lateral riverside are affected by both hydrologic connectivity and disconnectivity.In recent years,anthropogenic activities and climate changes have caused wetland shrinkage and land degradation along the lateral riverside of many arid and semiarid regions.Since microorganisms are major drivers of soil biochemical cycling,it is essential to examine soil microbial communities along the lateral landscape continuum to understand their ecosystem functioning and predict future land changes.Here,we collected samples along a lateral riverbed center-riverbed edge-oxbow lake-floodplain-terrace continuum(i.e.,landward distribution)in the Xilin River Basin,Inner Mongolia,China.The floodplain had the highest microbial diversity and heterogeneity,with Bacteroidetes,β-andγ-Proteobacteria being the most abundant taxa.In contrast,the terrace had the lowest microbial diversity and heterogeneity,with Acidobacteria,Actinobacteria,Verrucomicrobia,Gemmatimonadetes,andα-Proteobacteria as the most abundant taxa.Silt particle,salinity,and moisture were the most influential factors for landward variation of bacterial communities along the riverside continuum.Altogether,we demonstrate that dominant bacterial lineages,soil particles,and moisture-related factors are valuable indicators of this continuum,which can be leveraged for the early prediction of drought-induced wetland shrinkage and grassland desertification.