Monitoring land use and soil salinity changes in coastal landscape: a case study from Senegal

An insight into effect of soil salinity on vegetation dynamics in the exposed seafloor of the Aral Sea

The desiccation of the Aral Sea has precipitated significant ecological degradation, resulting in the progressive development of vegetation on the exposed seafloor. Soil salinity emerges as a pivotal determinant in this ecological succession process. Employing a comprehensive methodology integrating multi-source datasets spanning from 1986 to 2023, this study elucidates the temporal changes in vegetation dynamics and soil salinity levels. Satellite imagery (Landsat-4/5/7/8), field soil samplings, hydrological and topographic data were analyzed to understand their interactions with regression analysis. The results reveal a consistent increasing trend in the Normalized Difference Vegetation Index (NDVI) across the exposed seabed since 1986. However, NDVI demonstrates a non-linear relationship with elevation in the North Aral Sea region. Interestingly, NDVI levels near an elevation of 42 m on the exposed seabed approximate those observed during the pre-recession period in the 1960s. Conversely, in the South Aral Sea region, NDVI demonstrates a linear upward trend with increasing elevation. Furthermore, the spatial distribution of soil salinity on the exposed seabed was delineated with linear regression analysis. It revealed water salinity levels at the time of sea recession can serve as a proxy for soil salinity in cases where direct soil data is unavailable. Through establishing a robust correlation between NDVI and soil salinity, the range of stable NDVI values on the exposed seabed was delineated. Lastly, three hypothetical scenarios of rising water levels were considered to evaluate changes in stable NDVI across different elevation gradients. If the water level returns to 45 m, the salt-desert area would decrease by 4.5 × 104 km2, accounting for 23 % of the total area in 1960. At this water level, it is anticipated that lake hydrological conditions and ecological environments may restore to those observed in 1981. This study provides a long-term perspective on environmental changes in the Aral Sea region by integrating multiple data sources and analytical methods. The predictive insights from the scenario analysis offer valuable guidance for future water management and ecological restoration efforts. Compared with previous studies, it presents a detailed and comprehensive picture of the interplay between vegetation dynamics and soil salinity, highlighting the critical impact of water level changes on the region's ecosystem.

Individual and mutual effects of elevated carbon dioxide and temperature on salt and cadmium uptake and translocation by rice seedlings

Plant kingdoms are facing increasingly harsh environmental challenges marked by the coexposure of salinity and pollution in the pedosphere and elevated CO₂ and temperature in the atmosphere due to the rapid acceleration of industrialization and global climate change. In this study, we deployed a hydroponics-based experiment to explore the individual and mutual effects of different temperatures (low temperature, T1: 23°C; high temperature, T2: 27°C) and CO₂ concentrations (ambient CO₂: 360 ppm; medium CO₂: 450 ppm; high CO₂: 700 ppm) on the uptake and translocation of sodium chloride (NaCl, 0.0, 0.2, 0.6, and 1.1 g Na/L) and cadmium nitrate (Cd(NO₃)₂·4H₂O, 0.0, 0.2, 1.8, and 5.4 mg Cd/L) by rice seedlings. The results indicated that Cd and Na exposure significantly (P< 0.05) inhibited plant growth, but T2 and medium/high CO₂ alleviated the effects of Cd and Na on plant growth. Neither significant synergistic nor antagonistic effects of Cd and Na were observed, particularly not at T1 or high CO₂. At increasing temperatures, relative growth rates increased despite higher concentrations of Cd and Na in both rice roots and shoots. Similarly, higher CO₂ stimulated the growth rate but resulted in significantly lower concentrations of Na, while the Cd concentration was highest at medium CO₂. Coexposure experiments suggested that the concentration of Cd in roots slightly declined with additional Na and more at T2. Overall, our preliminary study suggested that global climate change may alter the distribution of mineral and toxic elements in rice plants as well as the tolerance of the plants.

Climate resilient integrated soil-crop management (CRISCM) for salt affected wheat agri-food production systems

Maximizing opportunities for climate resilient agriculture is vital for global food security, and ecological sustainability. To explore the improvement potential of mitigation and adaptation strategies in stabilizing wheat production and increasing farm income in sodicity-prone Ghaghar Basin of Haryana, India, participatory research trials on land reclamation (gypsum/pressmud) and crop management (varieties, nutrient management and weed control) practices were undertaken during 2016-2020. Results indicated that combining gypsum and pressmud together accelerated the reclamation process (soil pH: -3.3% and ESP: -22.1%) and improved plant adaptability (RWC: 10%; MI: -15%; Pn: 40%; gS: 36%; NaK_S: -38% and NaK_R: -42%), which in turn increased wheat yield by 20% compared to unamended control. With increasing sodicity stress, salt tolerant wheat variety KRL 210 exhibited better morpho-physiological adaptation, lesser yield reduction (0.8-1.1 t ha^-1) and attained 4.1% mean yield advantage compared to traditionally cultivated HD 2967. There were genotypic differences for N requirements in sodicity stressed wheat, with 173 kg ha^-1 in KRL 210 and 188 kg ha^-1 in HD 2967 as the economically optimum dose; further advocating for upward revision of current N recommendations beyond 150 kg N ha^-1. Balanced nutrition through foliage applied K compensated the sodicity hazards with lower proportion of Na⁺/K⁺ in leaf tissues (13%), and attained higher grain yield (4%) and incremental income (34 US$ ha^-1) compared to farmers' practice. Sequential use of herbicides provided affordable solution to check Phalaris minor infestation (84% WCE) and enhanced wheat productivity (5.7% higher) with incremental income of 48 US$ ha^-1 compared to farmers' sole dependency on post-emergence herbicides. Synergistic integration of gypsum and pressmud-mediated sodic land reclamation, usage of stress tolerant wheat variety, 15% higher N application, foliar K-nutrition and effective P. minor control substantiate appreciable reduction in soil sodicity, improved crop resilience, and ultimately translated into 5% and 26% higher yields over the recommended and local farm practices, respectively. The key insights of this study suggest a range of opportunities wherein inputs of CRISCM could potentially stabilize the wheat production, improve farm economy and reduce environmental risks beyond what is currently being achieved with existing farm practices.

Modelling Land Use and Land Cover in the Transboundary Mono River Catchment of Togo and Benin Using Markov Chain and Stakeholder’s Perspectives

Integrating both modeling approach and stakeholders’ perspectives to derive past and future trends of land use land cover (LULC) is a key to creating more realistic results on LULC change trajectories and can lead to the implementation of appropriate management measures. This article assessed the past changes of LULC in the Mono River catchment using Landsat images from the years 1986, 2000, 2010, and 2020 by performing Machine Learning Classification Method Random Forest (RF) technique, and using Markov chain method and stakeholder’s perspective to simulate future LULC changes for the years 2030 and 2050. LULC was classified as savanna, cropland, forest, water bodies, and settlement. The results showed that croplands and forests areas declined from 2020 to 2050 with decreases of −7.8% and −1.9%, respectively, a modest increase in settlement (1.3%), and savanna was the dominant LULC in the study region with an increase of 8.5%. From stakeholders’ perspective, rapid population growth, deforestation, rainfall variability/flood, urbanization, and agricultural expansion were the most important drivers associated with the observed LULC changes in the area. Other factors, such as lack of political commitment, distance to river, and elevation were also mentioned. Additionally, most the land-use scenarios identified by stakeholders would intensify land degradation and reduce ecosystem services in the area. By considering all of these potential LULC changes, decision-makers need to develop and implement appropriate solutions (e.g., land use planning strategies, reforestation campaigns, forest protection measures) in order to limit the negative effects of future LULC changes.