Watershed Ecology and the Environment最新文献

The expansion of saline-alkali paddy fields, coupled with the application of large amounts of nitrogen (N) fertilizers, has given rise to a host of environmental concerns. While N and carbon (C) are vital indicators for assessing soil fertility, their dynamic characteristics in saline-alkali paddy soil remain obscure. To address this knowledge gap, we established paddy mesocosms with five distinct N-fertilizer treatments: control without N-fertilizer (CK), urea (U), urea with inhibitors (UI), organic–inorganic compound fertilizer (OCF) and C-based slow-release fertilizer (CSF). The objective was to monitor the dynamic changes of various N and soil organic-C (SOC) during a 137-day rice growing season, and to clarify the microbiological characteristics. By the end of the rice growing season, soil ammonia-N (NH₄⁺-N) concentrations were UI > OCF > CSF > U > CK, and UI had a significant difference (p < 0.05) with all the other four treatments. Soil nitrate-N (NO₃⁻-N) concentrations in OCF and CSF treatments were 5.64 ± 1.25 mg kg⁻¹ and 6.81 ± 0.29 mg kg⁻¹, respectively, significantly (p < 0.05) higher than U and UI treatments. NH₄⁺-N showed a negative correlation with NO₃⁻-N regardless of the N-fertilizer types, and a significant (p < 0.01) positive relationship with alkali-hydrolyzable N (AHN). A significant (p < 0.01) positive relationship existed between total-N (TN) and Bacteria 16S rRNA gene. The SOC had a significant (p < 0.05) positive relationship with mcrA gene. During the entire rice growing season, CSF treatment had lower mean TN and SOC concentrations than all the other treatments, and exhibited the highest TN and total organic-C (TOC) content in rice. In summary, the UI can increase the residual NH₄⁺-N in saline-alkali paddy fields, and the CSF is a better choice for growing rice.

Although numerical water quality models offer valuable insights into thermal stratification (TSn) and mixing dynamics in lakes, they are often resource and time consuming, limiting their applications for investigating a large number of lakes over a wide geographical area. An alternative approach is using well-known thermal classification systems, which require minimum data to provide acceptable information on TSn and mixing patterns in lakes. This study investigates the TSn and mixing regimes in 198 dam reservoirs located in Iran, using Lewis’s method for analysis. The results highlight that all 198 investigated reservoirs in Iran can be represented by six out of eight possible thermal classifications. The majority of the northeastern reservoirs are categorized as “warm monomictic”. For the reservoirs located in the north and northwest regions, all six thermal classes are observed. However, in the southern part of Iran, only the reservoirs of “continuous warm polymictic”, “warm monomictic”, and “discontinuous cold polymictic” types are located. Our findings reveal that 35.4%, 21.2%, 17.2%, 13.1%, 6.6%, and 5.6% of the investigated reservoirs were classified as “warm monomictic”, “discontinuous cold polymictic”, “continuous cold polymictic”, “dimictic”, “discontinuous warm polymictic”, and “continuous warm polymictic”, respectively. Our results can provide authorities with initial insights for further in-depth studies and decision-making into water quality management in Iran and enhancement strategies for the reservoirs in the country.

Flash flood causes severe damage to the environment and human life across the world, no exception is Bangladesh. Severe flash floods affect the northeastern portion of Bangladesh in the early monsoon and pose a serious threat to every aspect of socioeconomic development and environmental sustainability. To manage the threat and reduce flood loss, the map of flash flood susceptible zones plays a key role. Thus, the aim of this research is to map the flash flood-susceptible areas of the northeastern haor areas of Bangladesh utilizing GIS-based bivariate statistical models. The models utilized are frequency ratio (FR), weights of evidence (WoE), certainty factor (CF), Shanon’s entropy (SE) and information value (IV). Among the 250 identified flash flood locations, 80 % data was used for training purposes and 20 % data for testing purposes. Eleven selected conditioning factors of flash flood include elevation, slope, aspect, curvature, TWI, TRI, SPI, distance to stream, stream density, rainfall and physiography. The calculated weights are assigned to the conditioning factors using ArcGIS environment to prepare the final flash flood maps. Results of AUC of ROC indicate WoE (success rate = 0.833 and prediction rate = 0.925) is the best model for flash flood susceptibility mapping followed by FR (success rate = 0.828 and prediction rate = 0.928) and SE (success rate = 0.827 and prediction rate = 0.923). According to the models, topographic (flat area) and hydrologic factors significantly control flash flood occurrence in the study area. The prepared flash flood susceptibility maps will be helpful for disaster managers and haor master planners of the study area.

The invasive species Spartina alterniflora has significantly disrupted the ecological stability of coastal wetland ecosystems. Consequently, its control has become an important aspect of coastal wetland conservation. When controlling S. alterniflora, it is imperative to assess the ecological impacts of control methods. In this study, the effects of different control methods, i.e. “mowing + flooding” (MF) and “mowing + plowing” (MP), on the soil carbon and nitrogen contents in coastal wetlands were investigated in the Yellow River Delta, China. The results showed that the contents of soil organic carbon, inorganic carbon, and total nitrogen in the MF area within 2 years after treatment were 2.03–3.93 g/kg, 13.74–16.06 g/kg, and 0.24–0.47 g/kg, respectively, which were 36.33 %–-199 %, 2.91 %–36.71 % and 115.42 %–212.09 % higher than that those in the CK area, respectively. The C/N ratio in the MF treatment was 6.98–8.54, which was 5.42 %–40.30 % lower than that in the CK treatment. The contents of soil organic carbon, inorganic carbon, and total nitrogen in the MP area were 1.52–2.3 g/kg, 13.07–14.94 g/kg, and 0.2–0.32 g/kg, respectively, which were 15.91 %–54.18 %, 0.97 %–15.56 % and 35.19 %–182.26 % higher than those in the CK area. The C/N ratio in the MP area was 14.72 %–46.79 % lower than that in the CK area. Correlation analysis revealed that the soil carbon and nitrogen contents in the MF area were significantly positively correlated with the soil water content and electrical conductivity, and the C/N ratio was significantly negatively correlated with the soil sand content. In the MP area, the soil carbon and nitrogen contents were affected by the soil water content and electrical conductivity. The soil organic carbon content was also significantly negatively correlated with soil pH and significantly positively correlated with soil clay content. The C/N ratio was significantly negatively correlated with the total nitrogen content. Overall, the effects of MF on the soil carbon and nitrogen content in coastal wetlands were greater than those of MP. Future studies need to pay attention to the changes in tidal hydrological processes to more accurately assess the impacts of the control of S. alterniflora on the overall carbon sink capacity of the intertidal zone.

A comprehensive understanding of how socioecological factors influence multiple ecosystem services (ESs) may provide stakeholders with a management tool to coordinate economic development and environmental protection. However, previous studies have focused more on the supply side compared with the demand of ESs. Furthermore, the underlying mechanisms for the changes in the supply–demand balance of ESs and their multiple drivers remain unclear. Therefore, in this study, an integrated theoretical framework was developed to assess the interactions of socioecological factors, including land use and cover, the social economy, climate, and topography, with the variations in ES supply, demand, and balance, which were mapped at the city scale in the Yangtze River Economic Belt (YREB). A variance inflation factor (VIF) was employed to detect the multicollinearity of the factors, and the sum of Akaike weights was used to simplify the driving factors and identify essential driving factors. We employed variation partitioning analysis (VPA) to reveal the effects of unique and combined drivers on ES supply, demand and balance. The results revealed that undersupply cities (11.93% of the area) were concentrated within the three national urban agglomerations and increased in area from upstream to downstream, whereas oversupply cities (88.07%) were distributed mainly in the surroundings of the urban agglomerations. According to the VPA, the essential driving factors effectively explain the variation in the ES supply, demand, and balance in the YREB. More importantly, these driving factors were simplified with no significant decrease in explanatory power. In oversupply cities, the ES changes were determined based on socioeconomic factors (urbanization rate and population density), land use/land cover (cropland, woodland, and unused land), and their interactions. In undersupply cities, population density (PD) explained the majority of the variation in ESs. However, the effects of climate and topography on ESs were more prominent at the scale of all cities in the YREB. In addition, PD displayed a significant negative correlation with ES supply and balance, but was positively related to ES demand in the undersupply cities. These findings contribute to a comprehensive understanding of the effects of the interactions among socioecological factors on the supply–demand balance of ESs. This study is informative for human well-being and sustainable socioeconomic development in the region.

Hydrologic restoration at the watershed scale is a complex process that can influence other processes and conditions within the watershed and downstream systems. Given these interrelated watershed scale processes, tools like models are essential to assess the potential effectiveness of sub-watershed to regional remediation strategies for ecological restoration. The goal of Everglades restoration is to restore the quality, quantity, and timing of water to one of the most ecologically unique and complex systems. This study aimed to evaluate changes to water quality associated with hydrologic restoration efforts within the Feeder Canal Basin as identified by the Western Everglades Restoration Project (WERP) by demonstrating, through simulations the potential effectiveness of implementing water quality remediation measures such as Best Management Practices (BMPs) and Stormwater Treatment Areas (STAs) within the WERP area. Additionally, to understand potential phosphorus sources and pre-develpoement conditions within the basin, a pre-development baseline was developed. Using the Watershed Assessment Model (WAM) various model alternatives including the WERP tentatively selected plan (TSP) were developed for a 22 year period of simulation. The implementation of both moderate and aggressive BMPs significantly reduced total phosphorus concentrations within the canal system at various levels indicating an improvement to near-field conditions. Meanwhile, not until the moderated BMPs and operation of an STA do water quality improvement become realized further downstream. The combined strategy of BMPs and STA demonstrates the integrated nature of nutrient remediation with both near and far-field benefits to the system with hydrologic restoration. This integrated strategy of water quality and hydrologic restoration can lead to a more sustainable and resilient restored ecosystem.

South Africa has a wealth of wetlands that provide a range of environmental, cultural and economic goods and services. In recognition of the importance of wetlands, South Africa has been a member of the Ramsar Convention on Wetlands of International Importance (also referred to as the Ramsar Convention) since 1975. Apart from this international commitment, South Africa has developed an array of environmental laws and policies that serve as instruments for protecting and managing wetlands. The study aimed to analyse the strengths and limitations of South Africa’s environmental policies and legislative framework that promotes wetland protection and management. The Constitution and nine environmental national laws with provisions relating to wetland conservation and management were thus purposefully selected and analysed qualitatively. The study found that there is no stand-alone wetland policy that protects wetlands; rather, several sectoral policies integrate objectives relating to wetland conservation in the country including those that cover agriculture, the environment, biodiversity and water. This multiplicity means there are no unified management objectives for wetlands protection and conservation. The study also found that there is a lack of harmonisation of policies and legislation, inadequate intergovernmental coordination and no integrated monitoring among the government departments involved. The study concludes that this disjointed and incoherent approach to wetlands conservation and management has weakened the effectiveness of the legal framework and this has obstructed their effectiveness in protecting this sensitive ecosystem.

The analysis of morphometric parameters plays a crucial role in understanding and managing watersheds, making it a fundamental component of hydrological investigations. This review paper talks about how important it is to objectively evaluate morphometric parameters, with a focus on the evaluation of basins' relief, linear, and areal parameters. However, it is noted that there is a lack of a distinct standard classification and implication for each parameter in some research publications. Furthermore, the range and categories of values for each morphometric parameter have not been adequately addressed in previous studies. Many papers state whether a particular parameter's resultant value is high or low without providing specific value ranges or associated implications. Also, it is emphasised that the accuracy and sources of digital elevation models (DEMs) affect how well morphometric parameter analysis works, even when DEMs with the same resolution are used. The existing literature demonstrates that determining the value of each morphometric parameter poses significant challenges. Moreover, verifying the first and second Horton's laws and assessing the correlations between morphometric parameters have been lacking in some articles. The main objective of this review article is to address these gaps by providing an in-depth study of each parameter's categorization, including the range of values, the level of input data quality, the data products generated, and the applicability of the fundamental Horton's laws. By doing so, this review aims to enhance the understanding of morphometric parameters, their value ranges, and the significance of their application in watershed analysis and management.