Spatiotemporal Change Analysis of Soil Moisture Based on Downscaling Technology in Africa

Evaluating the long-term spatiotemporal variability in soil moisture (SM) over Africa is crucial for understanding how crop production is affected by drought or flooding. However, the lack of continuous and stable long-term series and high-resolution soil moisture records impedes such research. To overcome the inconsistency of different microwave sensors (Advanced Microwave Scanning Radiometer-EOS, AMSR-E; Soil Moisture and Ocean Salinity, SMOS; and Advanced Microwave Scanning Radiometer 2, AMSR2) in measuring soil moisture over time and depth, we built a time series reconstruction model to correct SM, and then used a Spatially Weighted Downscaling Model to downscale the SM data from three different sensors to a 1 km spatial resolution. The verification of the reconstructed data shows that the product has high accuracy, and can be used for application and analysis. The spatiotemporal trends of SM in Africa were examined for 2003–2017. The analysis indicated that soil moisture is declining in Africa as a whole, and it is notably higher in central Africa than in other subregions. The most significant decrease in SM was observed in the savanna zone (slope < −0.08 m3 m−3 and P < 0.001), followed by South Africa and Namibia (slope < −0.07 m3 m−3 and P < 0.01). Seasonally, the most significant downward trends in SM were observed during the spring, mainly over eastern and central Africa (slope < −0.07 m3 m−3, R < −0.58 and P < 0.001). The analysis of spatiotemporal changes in soil moisture can help improve the understanding of hydrological cycles, and provide benchmark information for drought management in Africa.

Degrading permafrost river catchments and their impact on Arctic Ocean nearshore processes

Arctic warming is causing ancient perennially frozen ground (permafrost) to thaw, resulting in ground collapse, and reshaping of landscapes. This threatens Arctic peoples' infrastructure, cultural sites, and land-based natural resources. Terrestrial permafrost thaw and ongoing intensification of hydrological cycles also enhance the amount and alter the type of organic carbon (OC) delivered from land to Arctic nearshore environments. These changes may affect coastal processes, food web dynamics and marine resources on which many traditional ways of life rely. Here, we examine how future projected increases in runoff and permafrost thaw from two permafrost-dominated Siberian watersheds—the Kolyma and Lena, may alter carbon turnover rates and OC distributions through river networks. We demonstrate that the unique composition of terrestrial permafrost-derived OC can cause significant increases to aquatic carbon degradation rates (20 to 60% faster rates with 1% permafrost OC). We compile results on aquatic OC degradation and examine how strengthening Arctic hydrological cycles may increase the connectivity between terrestrial landscapes and receiving nearshore ecosystems, with potential ramifications for coastal carbon budgets and ecosystem structure. To address the future challenges Arctic coastal communities will face, we argue that it will become essential to consider how nearshore ecosystems will respond to changing coastal inputs and identify how these may affect the resiliency and availability of essential food resources.

Modulation of Ground Deformation and Earthquakes by Rainfall at Vesuvius and Campi Flegrei (Italy)

Volcanoes are complex systems whose dynamics is the result of the interplay between endogenous and exogenous processes. External forcing on volcanic activity by seasonal hydrological variations can influence the evolution of a volcanic system; yet the underlying mechanisms remain poorly understood. In the present study, we analyse ground tilt, seismicity rates and rainfall amount recorded over 6 years (2015–2021) at Vesuvius and Campi Flegrei, two volcanic areas located in the south of Italy. The results indicate that at both volcanoes the ground deformation reflects the seasonality of the hydrological cycles, whereas seismicity shows a seasonal pattern only at Campi Flegrei. A correlation analysis on shorter time scales (days) indicates that at Vesuvius rain and ground tilt are poorly correlated, whereas rain and earthquakes are almost uncorrelated. Instead, at Campi Flegrei precipitations can affect not only ground deformation but also earthquake rate, through the combined action of water loading and diffusion processes in a fractured medium, likely fostered by the interaction with the shallow hydrothermal fluids. Our observations indicate a different behavior between the two volcanic systems: at Vesuvius, rain-induced hydrological variations poorly affect the normal background activity. On the contrary, such variations play a role in modulating the dynamics of those metastable volcanoes with significant hydrothermal system experiencing unrest, like Campi Flegrei.

Artificial biocrust establishment on materials of potash tailings piles along a salinity gradient

Biocrust communities provide a pallet of ecosystem services, such as soil stabilization, altering of hydrological cycles and primary production, and often are the first colonizers of unvegetated surfaces during succession. Therefore, artificially establishing biocrusts can improve soil properties, for example, by stabilizing bare soil surfaces against erosion or by accumulating nutrients. In this study, the establishment of artificial biocrusts was tested for the restoration of potash tailings piles that result from potash fertilizer production and mostly consist of NaCl. A biocrust cover as primary vegetation could decrease the saline seepage waters by trapping rainwaters, thereby reducing the environmental pollution. In a laboratory experiment, we created a salt gradient by mixing the tailings materials with non-saline dune sand. Surface material of the abandoned potash tailings pile Neuhof-Ellers (NE) and material of the Infiltration Hampering Stratum (IHS) were tested, along with a treatment with bone charplus (BCplus) and sodium alginate. A mixture of 50% (w/w) IHS and dune sand was most successful for the establishment of green biocrust microalgae, based on increased biomass and photosynthetic performance. The chlorophyll a content was negatively correlated with the electrical conductivity (EC), and was significantly increased in the BCplus and sodium alginate treatment, while biocrusts failed to establish on pure tailings piles substrates. The limit of the substrates EC for biocrust establishment was 35 mS cm−1. This limit provides a baseline for future studies that should use BCplus and sodium alginate to increase the success of biocrust establishment on potash tailings piles.

Plant herbivore interactions: combined effect of ground water level, root vole grazing and sedge silication

1. Silicon mediated plant–herbivore interactions have gained increasing recognition and have now been studied in a wide range of species. Many studies have also considered accumulation of Si by plants as a process largely driven by geo-hydrological cycles. 2. To identify factors driving the water - plant Si - herbivore nexus we analysed the concentration of Si in fibrous tussock sedge (Carex appropinquata), the population density of the root vole (Microtus oeconomus) and the ground water level, over 11 years. 3. The largest influence of autumn Si concentration in leaves (Sileaf) was the level of the current year’s ground water table, which accounted for 13.3% of its variance. The previous year’s vole population density was weakly positively correlated with Sileaf and alone explained 9.5% of its variance. 4. The only variable found to have a positive, significant effect on autumn Si concentration in rhizomes (Sirhiz) was the current year spring water level explaining as much as 60.9% of its variance. 5. We conclude that the changes in Si concentration in fibrous tussock sedge are predominantly driven by hydrology, with vole population dynamics being secondary. Our results provide only partial support for the existence of plant-herbivore interactions, as we did not detect the significant effects of Si tussock concentration on the vole density dynamics. This was mainly due to low level of silification of sedges, which was insufficient to impinge herbivores. Future studies on plant–herbivore interactions should therefore mainly focus on identification of mechanisms and conditions allowing plants to accumulate silica at the levels sufficient to act as an anti-herbivore protection.

Early Peak of Latent Heat Fluxes Regulates Diurnal Temperature Range in Montane Cloud Forests

Hydro-climate in the montane cloud forest (MCF) regions is unique for its frequent fog occurrence and abundant water interception by tree canopies. Latent heat (LH) flux, the energy flux associated with evapotranspiration (ET), plays an essential role in modulating energy and hydrological cycles. However, how LH flux is partitioned between transpiration (stomatal evaporation) and evaporation (non-stomatal evaporation), and how it impacts local hydro-climate remain unclear. In this study, we investigate how fog modulates the energy and hydrological cycles of MCF by using a combination of in-situ observations and model simulations. We compare LH flux and associated micrometeorological conditions at two eddy-covariance sites—Chi-Lan (CL), a MCF, and Lien-Hua-Chih (LHC), a non-cloud forest in Taiwan. The comparison between the two sites reveals an asymmetric LH flux with an early peak at 9:00 in CL as opposed to LHC, where LH flux peaks at noon. The early peak of LH flux and its evaporative cooling dampen the increase in near-surface temperature during the morning hours in CL. The relatively small diurnal temperature range, abundant moisture brought by the valley wind, and local ET result in frequent afternoon fog formation. Fog water is then intercepted by the canopy, sustaining moist conditions throughout the night. To further illustrate this hydrological feedback, we used a land surface model to simulate how varying canopy water interception can affect surface energy and moisture budgets. Our study highlights the unique hydro-climatological cycle in MCF and, specifically, the inseparable relationship between the canopy and near-surface meteorology during the diurnal cycle.

INFILTRATION WELLS ALTERNATIVES TO REDUCE WATER PUDDLE IN LOWOKWARU DISTRICT, MALANG CITY

Surface waters give a plentiful supply of waters ready to be utilized for residence, farmland, fishery, industry, and electric generating machine, and most importantly, to deal with the problem of water scarcity (crisis). Rain is one of the hydrological cycles that help to preserve groundwater (shallow groundwater). During the rainy season, most waters go directly to the river and the sea without processing, creating inundations and flood in some places. Water resources, however, begin to lose their supporting capacity. Water supply is no longer balanced with the demand that starts to bulge up excessively. This disrupted balance is indicated by many critical lands that are less productive and incapable of absorbing waters to the ground. Considering this outline, the implementation of environmentally friendly infiltration wells can be a strategic option to solve the water balance issue. Some alternatives of infiltration wells are proposed as the solution to the problem that this research deals with. It is estimated that these wells can reduce 10%-15% of surface runoff rate in Lowokwaru District of Malang City, especially around Soekarno-Hatta Street that always leaves massive water puddle, especially during the rainy season. This research gives the relevant institutions and user community information about drainage construction, drainage network, and land use above drainage network. Through this information, it is expected that the follow-up can be given efficiently to produce an optimum and effective drainage network. Community participation, therefore, is needed to maintain the benefits of alternative infiltration wells to ensure their sustainability in the future.

Fimbristylis littoralis (lesser fimbristylis).

F. littoralis is a tufted leafy annual or short-lived herb (sedge) included in the Global Compendium of Weeds where it is listed as an agricultural and environmental weed (Randall, 2012). It has escaped from cultivation and become established along waterways and wetlands (Flora of China Editorial Committee, 2014). The species is of particular concern in rice plantations around the world (Holm et al., 1977). It shows allelopathic activity and once established it can change features of ecosystem functions including hydrological cycles, biophysical dynamics, nutrient cycles, and community composition (Holm et al., 1977; Holou et al., 2013).

Evaluating ecosystems services values due to land use transformation in the Gojeb watershed, Southwest Ethiopia

Background Land use land cover (LULC) transformation and ecosystems service valuation (ESVs) play important roles for vegetation restoration and design restoration options such as payment for ecosystems service programs. The objective of this work was to quantify LULC transformations and associated ESVs in the Gojeb sub-basin by analyzing LULC between 1986 and 2016 using satellite images, field observations and ancillary datasets. And Ecosystems service valuations of different land use types were carried out using benefit transfer method. Results The summarized LULC classes are: bareland, cropland, grassland, forest, plantation, settlement, shrub, water-body and woodland. The ESVs were evaluated for each LULC based on these LULC classes. Forests had the highest cover (> 423,000 ha ~ 60%) in 1986 but it reduced to 317,000 ha (~ 45%) in 2016. About > 56,000 ha of forests were changed to cultivated land, and > 105,000 ha to different classes. Cultivated land increased to > 258,000 ha (~ 37%) in 2016 compared to 150,000 ha (~ 21.5%) in 1986. The sub-basin had ESVs of US$2.52 billion in 1986 but decreased to US$ 1.97 billion in 2016; losing about US$ 0.551 billion within the last 30 years (annual loss rate of US$ 18.4 million). Potential drivers would be agricultural expansion, land degradation/erosion, landslide and deforestation, indicating that requires concerted effort to restore and manage landscapes for sustainable socio-ecological and economic uses. Conclusion This study is meaningful for management of natural resources in the catchment, improvement of hydropower production and lifespan of the hydropower reservoir besides to improving land productivity for small holder farmers as hydrological cycles and biodiversity components of the catchment can be improved. This study assist policy makers in designing evidence-based programs such as payment for ecosystem services in the study area and elsewhere.

Laboratory evaluation of water vapour concentration dependence of commercial water vapour isotope cavity ring-down spectrometers for continuous onsite atmospheric measurements in the Amazon rainforest

&lt;p&gt;Commercially available laser-based spectrometers permit continuous field measurements of water vapour (H&lt;sub&gt;2&lt;/sub&gt;O) stable isotope compositions, yet continuous observations in the Amazon, a region that significantly influences atmospheric hydrological cycles on regional to global scales, are largely missing. In order to achieve accurate on-site observations in such conditions, these instruments will require regular on-site calibration, including for H&lt;sub&gt;2&lt;/sub&gt;O concentration dependence ([H&lt;sub&gt;2&lt;/sub&gt;O]-dependence) of isotopic accuracy.&lt;/p&gt;&lt;p&gt;With the aim of conducting accurate continuous &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O and &amp;#948;&lt;sup&gt;2&lt;/sup&gt;H on-site observation in the Amazon rainforest, we conducted a laboratory experiment to investigate the performance and determine the optimal [H&lt;sub&gt;2&lt;/sub&gt;O]-dependence calibration strategy for two commercial cavity-ring down (CRDS) analysers (L1102i and L2130i models, Picarro, Inc., USA), coupled to our custom-built automated calibration unit. We particularly focused on the rarely investigated performance of the instruments at atmospheric H&lt;sub&gt;2&lt;/sub&gt;O contents above 35,000 ppm, a value regularly reached at our site.&lt;/p&gt;&lt;p&gt;The later analyser model (L2130i) had better precision and accuracy of &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O and &amp;#948;&lt;sup&gt;2&lt;/sup&gt;H measurements with a less pronounced [H&lt;sub&gt;2&lt;/sub&gt;O]-dependence compared to the older L1102i. The [H&lt;sub&gt;2&lt;/sub&gt;O]-dependence calibration uncertainties did not significantly change with calibration intervals from 28 h up to 196 h, suggesting that one [H&lt;sub&gt;2&lt;/sub&gt;O]-dependence calibration per week for the L2130i and L1102i analysers is enough. This study shows that with both CRDS analysers, correctly calibrated, we should be able to discriminate natural diel, seasonal and interannual signals of stable water vapour isotopes in a tropical rainforest environment.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;