European Journal of Soil Science最新文献

Percent cropland under conservation agriculture (CA) as function of time.

Root-soil contact is a key factor in determining resource acquisition in soils; however its influence on the rhizosphere structure and the emerging plant traits are poorly understood. The present study aims to provide a comprehensive understanding of the coupled dynamics between plant roots and soil structure, with an emphasis on root-soil contact as a main explanatory variable. We investigated a fine-textured loam with a deformable soil matrix and a coarse-textured sand with rigid grains, with various degrees of compaction, structure heterogeneity, and fraction of fine particles. Over 21 days, we grew maize plants under well-watered conditions and monitored plant performance traits. After the growth period, we extracted undisturbed soil samples and scanned them with high resolution (10 μm) X-ray CT to characterize root-soil contact and root morphology. Our results show that in compressible soils, roots deform the surrounding soil matrix and induce rhizosphere compaction, whereas in non-compressible soils, the roots undergo deformation as they grow into zones with pores narrower than themselves. Increased root-soil contact did not result in increased plant transpiration or shoot biomass. Our study underscores the complex role of root-soil contact in shaping resource acquisition, and highlights the need to better understand the thresholds at which root-soil contact becomes limiting and how this depends on soil texture. It also emphasizes the influence of soil structure on root development and shows promising avenues for future work aimed at linking pore-scale heterogeneity and gas diffusion to root growth.

The characterization and assessment of soil functions is a prerequisite for agricultural and environmental policies aimed at soil health. However, there is a lack of satisfactory models for the assessment of soil functions supply to support national and intergovernmental initiatives. In this study we fill this gap by restructuring models developed to assess the multifunctionality of agricultural soils at the field scale. The multi-criteria decision models rely on soil properties, site characteristics and management information to assess the following five soil functions: (1) water regulation, (2) climate regulation, (3) nutrient cycling, (4) primary productivity and (5) provision of habitat for biodiversity. We develop models to assess soil functions supply at regional and national scales by adapting their structure to cope with the general lack of information on soil management at larger geographical scales. The restructured models are verified and a sensitivity analysis of the new model structure is performed. We further applied a comparison of the upscaled models with results from validated field-scale models using real data from 94 sites spanning across 13 European countries. We found that the upscaled models showed a similar sensitivity to the variability of the input data from the 94 sampling sites as the base models from which they were developed and that their overall supply is expected to be comparable. We describe the model structure of the upscaled models as well as their qualitative scales and integration rules. We propose the application of the models can serve for large-scale assessment of soil functions supply as part of soil health assessment for regional and national environmental and agricultural policies.

Water circulation within agroecosystems can contribute to the distribution of plant communities by inducing seed dispersal through a process known as hydrochory. As vegetation is currently intensively managed in Mediterranean agroecosystems, relying on seed dispersal to increase vegetation cover and limit soil erosion could be a cost-effective approach. However, hydrochory has rarely been studied when it occurs during surface runoff in agroecosystems. In addition, hydrochory has been observed to be an efficient dispersal agent that plays a key role in both maintaining and enhancing biodiversity. Studying the effect of simple soil surface features on seed mobilization and dispersal by hydrochory during surface runoff is thus a way to gain insight into the influence of agricultural practices on the natural seed dispersal process. Here, we used seeds marked with a UV powder to track seed mobilization and movement during a typical Mediterranean runoff event over a ploughed and a vegetated surface within interrows. Surface roughness was the main factor limiting seed remobilization after seed deposition, and buoyancy did not appear to facilitate secondary seed dispersal by hydrochory. Vegetation and surface roughness influenced seed dispersal and thus confirmed previous studies in permanent and quasi-permanent water streams. However, a slope was not associated with seed dispersal, suggesting that a certain degree of slope is required to observe an effect of the slope on seed dispersal. Our study showed that accounting for seed morphology revealed that round seeds were more sensitive to surface features such as surface roughness and vegetation cover than hooked or plumed seeds, which had an influence on patterns of seed deposit during surface runoff. In the face of climate change, our results contribute to the development of biodiversity-based mitigation strategies in Mediterranean regions and vineyards.

Climate change alters rainfall patterns and increases temperatures, which disrupt soil processes, enhance CO₂ emissions, and reduce the capacity of soils to store carbon. Soil respiration, the CO₂ released into the atmosphere from the soil, is a vital process in the terrestrial carbon cycle. We performed a two-year study investigating the seasonal variation of soil CO₂ efflux in two typical oak-dominated Mediterranean ecosystems, a deciduous and a broadleaf evergreen one, as we lack sufficient information on this topic. To understand the drivers of soil respiration, we also monitored soil water content and temperature, as well as organic matter input by sampling litterfall and fine roots and by applying in parallel a litter and root exclusion approach. We found a 30%–54% higher soil CO₂ efflux in broadleaf evergreens vs. deciduous oaks, depending on the season. We also identified significant effects of all tested drivers on soil respiration. Soil water content controlled the dependency of soil respiration on temperature and resulted in the highest CO₂ emissions in spring, when these conditions were optimal. The high litterfall input and turnover rate in spring further supported the peak of CO₂ respired by broadleaf evergreens' soil in this period. On the contrary, low water availability limited soil respiration during summer in both ecosystems. The litter and fine root exclusion resulted in a 69.9% and 38.7% reduction in CO₂ efflux in spring, for deciduous and evergreen oaks, respectively, verifying the important contribution of these organic inputs to soil respiration. However, it led to overestimation of soil respiration in summer and in the second year of the study, probably due to water retention. We developed a polynomial regression model that predicts CO₂ efflux with soil temperature and water content as multipliers, and it is novel in including carbon fluxes of litterfall and fine root production as explanatory variables. The model predictions are good for broadleaf evergreen oaks (R² = 0.64) and lower, but fair, for deciduous oaks (R² = 0.48) and can efficiently illustrate how microclimate in combination with organic input and affects soil respiration. Our findings can improve our knowledge of soil CO₂ effluxes and their drivers in typical oak-dominated Mediterranean ecosystems and support their climate-adapted management.

No-till may have the potential to improve the resilience of agricultural systems to climate change by enhancing soil structure and soil health. However, the experimental evidence for this is inconclusive because few field trials have been established long enough for the soil to reach a new (quasi-) equilibrium state upon adopting no-till practices. Soil-crop models should be useful tools to fill this knowledge gap, but most neglect the dynamics of soil properties and so cannot predict long-term changes in soil health. One exception is Uppsala model of Soil Structure and Function (USSF), which accounts for soil structure dynamics due to physical (e.g., swell-shrink, tillage) and biological (e.g., faunal activity, aggregation) processes. In this study, we used the USSF model to evaluate the potential long-term impacts of no-till systems on soil structure, soil organic matter (SOM), water balance, and yields of winter wheat based on data obtained from a long-term farming systems trial near Zürich, Switzerland. The model was first calibrated against field measurements during one growing season of soil water contents, leaf area index, and grain yield and aboveground biomass of winter wheat. The calibrated model was then used to simulate a baseline period (1985–2015) and 18 transient future climate scenarios for the period 2020 to 2090 for continuous winter wheat in conventionally cultivated and no-till systems. In the simulations driven by future climate projections, SOM stocks decreased by 3%–15% in the tilled soil, whereas they were maintained under no-till despite rising temperatures. Enhanced physical protection associated with soil aggregation and improved thermal regulation from the surface residue cover were identified as mechanisms contributing to the maintenance of SOM stocks under no-till. Wheat yields increased slightly and were similar for tilled and no-tilled treatments, as simulated drought stress rarely occurred at the site, which has a wet climate, despite reductions in summer rainfall. The no-till system also showed an improved water balance, with smaller losses by surface runoff and soil evaporation, suggesting that conservation agriculture should be a promising strategy for sustaining soil health and soil functions in the face of a warming climate.