Robustness of a parsimonious subsurface drainage model at the French national scale

Drainage systems are currently implemented on agricultural plots subjected to temporary or permanent waterlogging issues. Drained plots account for 9 % of all arable soils in France. As such, the need for accurate hydrological modeling is crucial, especially in an unstable future context affected by climate change. The aim of this paper is to assess the capacity of the SIDRA-RU hydrological drainage model to represent the variability in pedoclimatic conditions within French metropolitan areas and to demonstrate the utility of this model as a long-term management tool. The model is initially calibrated using the KGE′ criterion as an objective function (OF) on a large and unique database encompassing 22 plots spread across France and classified according to three main soil textures (silty, silty–clay, and clayey). The performance of SIDRA-RU is evaluated by monitoring both the set of KGE′ calibration values and the quality of simulations on each plot with respect to high and low discharges, as well as the annual drained water balance. Next, the temporal robustness of the model is assessed by conducting, on selected plots, the split-sample test capable of satisfying the data requirements. Results show that the SIDRA-RU model accurately simulates drainage discharge, especially on silty soils. The performance on clayey soils is slightly weaker than that on silty soils yet remains acceptable. Similarly, the split-sample test indicates that SIDRA-RU is temporally robust on all three soil textures. Consequently, the SIDRA-RU model closely replicates the diversity of French drained soil and could be used for its long-term management potential.

Differences in the Content of Zn Fractions in the Profiles of Soils from Allotment and Domestic Gardens in South-Eastern Poland

The aim of the research was to show the distribution of fractions as well as bioavailability and the total forms of Zn in the profiles of soils from domestic gardens and family allotment gardens in six cities in south-eastern Poland. Results found that the level of Zn total form varied in the ranges from A horizon: 12.75–154.75 mg·kg−1 in sandy soils and 18.20–104.00 mg·kg−1 in silty soils. Accumulation of metals was assessed using concentration indices, Igeo, and the Cav/Ct and BF indices of bioavailable forms. The analysis took into account the role of organic matter as an important component in binding the analyzed metals in soil horizons subjected to long-term horticultural cultivation. In the two groups of sandy and silty soils distinguished according to their particle size distribution, horticultural treatments were found to exert a greater impact on sandy soils. Additionally, higher contents of the examined element were stated in the humus horizons, as indicated by the high values of concentration and Igeo indices showing high Zn pollution in the soils. The content of bioavailable zinc forms was significantly high, especially in soils with a higher metal content.

VEGETATIVE COVER OF THE MOUTH OF THE CHESNAVA RIVER (YAROSLAVL REGION)

Rivers are the basis for the creation of reservoirs, which can radically change the structure and functioning of aquatic and terrestrial ecosystems. Despite the fact that small rivers have long become a model object of research, work on them remains relevant to this day. The purpose of our study was to study the vegetation cover of the mouth section of the small river Chesnava, flowing in the Nekouz and Breitovsky districts of the Yaroslavl region and flowing into the Rybinsk reservoir. The most typical here are open zones with a depth of 0.9–2.5 m, shallow waters 0.1–0.8 m deep with silty, silty-sandy and sandy soils, and strips of periodically flooded coasts with sandy and silty soils that are drained after the water recession. The flora contains 82 species from 30 families and 57 genera. The dominant ecogroup is hygrophytes, cryptophytes and hemicryptophytes predominate in life forms, and boreal and holarctic species in the zonal-regional relation. The vegetation of the river is represented by 19 associations, united in 14 formations, the main ones of which are: Lemna-Hydrochairetum morsus-ranae, Typhetum angustifoliae, Phalarito arundinaceae-Glycerietum maximae, Sparganio emersi-Eleocharietum palustris, Heteroherboso-Eleocharietum palustris, Careto acutae-Phalaroidetum arundinaceae. The expansion of the shallow and gently sloping coastal zone contributes to the active overgrowing of the investigated area.

Robustness of a parsimonious subsurface drainage model at the French national scale

Drainage systems are currently implemented on agricultural plots subjected to temporary or permanent waterlogging issues. Drained plots account for 9 % of all arable soils in France. As such, the need for accurate hydrological modeling is crucial, especially in an unstable future context affected by climate change. The aim of this paper is to assess the capacity of the SIDRA-RU hydrological drainage model in representing the variability of pedoclimatic conditions within French metropolitan areas, as well as to demonstrate the utility of this model as a long-term management tool. The model is initially calibrated using the KGE' criterion as an Objective Function (OF) on a large and unique database encompassing 22 plots spread across France and classified according to three main soil textures (silty, silty-clayey and clayey). The performance of SIDRA-RU is evaluated by monitoring the KGE' calibration values, as well as the quality of the simulations of both high and low discharges and the annual drained water balance on each plot. Next, the temporal robustness of the model is assessed by conducting the split-sample test on the selected plots that satisfy the data requirements. Results show that the SIDRA-RU model accurately simulates the drainage discharge, especially on silty soils. The performance on clayey soils is slightly weaker than that on silty soils yet remains acceptable. Similarly, the split-sample test indicates that SIDRA-RU is temporally robust on all three soil textures. Consequently, the SIDRA-RU model closely represents the diversity of French drained soil and could be used for its long-term management.

Soil texture can predominantly control organic matter mineralization in temperate climates by regulating soil moisture rather than through direct stabilization

<p>Soil organic carbon (OC) levels generally increase with increasing clay and silt content under a similar climatic zone because of increased association of OC to clay minerals and stronger occlusion inside aggregates. Surprisingly though, in Western Europe many silt loam soils actually bear low topsoil OC levels compared to lighter textured soils. Soil texture obviously also strongly controls moisture availability with consequent indirect impact on heterotrophic activity. We hypothesized that with increasingly frequent summer drought: 1) soil microbial activity in sandy soils is more likely impeded due to their limited water holding capacity retention during droughts, while soil OC mineralization in silty soils remain be less drought-limited; 2) capillary rise from sufficiently shallow groundwater would, on the other hand, alleviate the water stress in lighter textures. To test these hypotheses, we established a one-year field trial with manipulation of soil texture, monitoring of soil moisture and maize-C decomposition via <sup>13/12</sup>C-CO<sub>2</sub> emissions. The upper 0.5 m soil layer was replaced by sand, sandy loam and silt loam soil with low soil OC. Another sandy soil treatment with a gravel layer was also included beneath the sand layer to exclude capillary rise. Soil texture did not affect maize-C mineralization (C<sub>maize</sub>-min) until April 2019 and thereafter C<sub>maize</sub>-min rates were higher in the silt loam than in the sandy soils (P=0.01). θ<sub>v</sub> correlated positively with the C<sub>maize</sub>-min rate for the sand-textured soils only but not for the finer textures. These results clearly highlight that soil texture controlled C<sub>maize</sub>-min indirectly through regulating moisture under the field conditions starting from about May, when soils faced a period of drought. By the end of the experiment, more added C<sub>maize</sub> was mineralized in the silt loam soil (81%) (P<0.05) than in the sandy soil (56%). Capillary rise did not result in a significant increase in cumulative C<sub>maize</sub>-min in the sandy soil, seemingly because the capillary fringe did not reach the sandy topsoil layer. These results imply that, under future climate scenarios the frequency of drought is expected to increase, the largely unimpeded microbial activity in silty soils might lead to a further stronger difference in soil OC with coarser textured soils under similar management.</p>