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Sugarcane cultivation is suitable for the exploitation of organic waste products. However, minimum complementary mineral input is necessary for optimal fertilisation. Control mineral fertilisation treatments with mulch (MCM) or without mulch (MC) were compared with two organic waste treatments, a pig slurry with mulch (PSM) and without mulch (PS), and a sugarcane vinasse with mulch (SVM) and without mulch (SV) on a Nitisol in French Reunion Island. The sugarcane yields obtained with the different treatments differed each year. However, no trend was observed and no significant and recurrent effect of the presence of mulch or of the different treatments was identified over the course of the 4 year experiment. Soil pHw and pH KCl measured in the different treatments increased from year 3 in with the treatments including organic waste products (PS, PSM, SV and SVM) but remained constant with the treatments including only mineral fertilisation (MC and MCM). With the exception of PS and PSM, which were significantly higher in year 4, soil organic carbon content was not modified by the treatments. Soil cation exchange capacity increased only slightly with the PS and PSM treatments from year 3 on. The differences in yields and soil properties can be explained by the nature of the organic waste products, the accumulation of nutrients after several applications, and the specific characteristics of the sugarcane crop. The improvement in soil properties from the third year on was not reflected in the yield of sugarcane because it was too weak, and the crop explores a much larger volume of soil.

International audience; To investigate the movement and content of the acid soil Pi fractions at different distances from the green manure (GM) application site at a GM microsite, an incubation experiment was conducted. Stylosanthes GM (10 or 40 ton/ha) was applied with or without phosphate fertilizer (monocalcium phosphate, MCP) at a concentration of 44 kg/ha P, which was laid on the surface in soil cylinders. The GM/fertilizer and soil were incubated for 14 and 28 d. The results indicated the movement distance and content of the Pi fractions (Al-, Fe-, and Ca-associated Pi as well as occluded P) in the acid soil microsite were significantly increased after the addition of MCP; however, the movement distances of the Pi fractions were all less than 3 mm after incubation for 28 d. This information will improve the efficiency of combined P and GM use and decrease the environmental load due to P pollution caused by GM and phosphate fertilizer.

International audience; The assessment of the impacts of land management on soil quality is crucial in the current environmental context. Among the many approaches available to assess soil quality, most of studies or monitoring programs consist in the measurement of stocks using an additive approach of physical, chemical and biological, parameters. More recently, functional methods have been developed to provide tools which better account the abioticbiotic interactions. The objective of our study was to evaluate and compare the capacity of physico-chemical, biological and functional parameters to assess the effect of land management on soil quality over a gradient of disturbance based on rubber tree plantations in Chachoengsao province, Thailand. Three sets of indicators were applied based on i. soil physico-chemical analyses, ii. biological analyses, based on soil free-living nematode indices iii. functional analyses, with Biofunctool (R) indicators linked to three main soil functions (carbon transformation, nutrient cycling, soil structure maintenance). A soil quality index resulting from the aggregation of each set of indicators into a single score showed that functional assessment was the most sensitive to the gradient of disturbance. Co-inertia analysis between sets revealed a significant relationship between functional analysis and both physico-chemical and biological sets of indicators, whereas the two latter were not related. Our results validated the ability of the functional method to better reflect the complexity of the abiotic-biotic interactions of the soil system.Highlights:• Three sets of soil quality indicators were compared.• Functional indicators were the most sensitive to the gradient of disturbance.• Functional set of indicators was significantly linked to physico-chemical and biological sets.• The functional method Biofunctool® integrate both soil biotic and abiotic components.

Recently, biochar has shown to be an alternative to waste disposal and a source of nutrients, acting as a soil amendment. The effects of two types of biochar on soil properties and sugar beet production as well as potential for carbon (C) sequestration were evaluated: biochar produced from sewage sludge (SB) and biochar produced from a 1:1 mixture of sewage sludge and sugarcane bagasse (MB). A greenhouse pot experiment was conducted using a sandy loam soil from the Brazilian savanna under treatments of MB applications at 2.5%, 5.0%, 7.5%, and 10.0%, SB application at 5.0%, and a conventional fertilization (CF) using lime and mineral fertilizers, with no fertilization as a control. After incubation for 45 d, seedlings were transplanted into each pot and cultivated for 55 d. Biochar characterization showed that pyrolysis reduced the biomass volume drastically, but concentrated the trace elements per unit of biochar weight. The MB treatments increased soil total C (by 27.8%) and pH (by 0.6), reduced the concentrations of nutrients, except for potassium (K), and chromium (Cr), and did not significantly alter lead (Pb) and cadmium (Cd) concentrations. Results of stable isotopes showed that all biochar treatments increased the total soil C stock and stability, suggesting a potential for application in C sequestration, and improved overall soil fertility. However, the biochar treatments also increased the concentrations of trace elements in the soil and plants. The sugar beet yields at 10.0% MB and 5.0% SB corresponded to 55% and 29% of the yield obtained in the CF treatment, respectively. These results may be due to biochar nutrients not being bioavailable when required by plants or to biochar nutrient adsorption.

A soil chemical quality index is designed for cacao production systems. It is based on worldwide scientific knowledge and built using data from three municipalities of Tolima department in Colombia. Fuzzy logic is used in a multicriteria decision making framework in two different ways. First, fuzzy sets are used to model an expert preference relation for each of the individual information sources to turn raw data into satisfaction degrees. Second, fuzzy rules are used to model the interaction between sources to aggregate the individual degrees into a global score. The whole framework is implemented as an open source software called GeoFIS. A part of the data was used for calibration, then the remaining data served as a validation set. The results were easy to analyze and in agreement with field observations. The output inferred by the fuzzy inference system was used as a target to learn the weights of classical numerical aggregation operators. Only the Choquet Integral proved to have a similar modeling ability, but its optimal tuning would have been difficult without learning.

International audience; Mediterranean forests own distinct characteristics resulting from climate, soil, and vegetation that affect soil microbial communities’ assembly and their associated functions. We initiated a multi-scalar analysis of environmental drivers of soil functioning to (1) identify pertinent factorial scales and (2) determine the relative importance of soil, vegetation, and geoclimate influences in shaping soil microbial functions across the French Mediterranean forests. Soil samples (0–15 cm) were collected from 60 forest sites and soil physicochemical and microbiological properties were assessed across different factorial scales i.e., bioclimates, slope exposures, and forest stands. Patterns in microbial catabolic potential (i.e., extracellular enzymes and microbial respiration) and carbon (C) source utilization (i.e., catabolic-level physiological profiling) were partitioned between vegetation cover, soil characteristics, and geoclimate components. Our results reveal that the catabolic potential of soil microbes was strongly influenced by the forest stands and mainly relied on ammonium and nitrate contents. In contrast, variation in C source utilization was mainly explained by vegetation cover. Soil metabolic capacities of microorganisms and resulting C dynamics were largely constrained by climate parameters, which suggests potentially important consequences for soil C storage. Our study revealed diverse structuration patterns between the catabolic potential and the carbon source utilization of soil microbial communities, and gives insights into the underlying mechanisms of soil microbial functioning in Mediterranean forests.

International audience; Trees residues decomposition is a key step in forested ecosystems. In the context of sclerophyllous Mediterranean forests, the effects of residue quality on soil organic matter and microbial communities is still poorly documented. Using a mesocosm experiment, we explored microbial responses (enzyme activities, basal respiration, molecular fingerprints and catabolic profiles) and variations in soil chemical properties (pH, CaCO3, organic C and N contents, quality of soil organic matter via 13C CP/MAS NMR) induced by coarse woody debris (W) or fine residues (i.e. twigs -leaves/needles, hereafter TL) from mono-specific or mixed stands of Pinus halepensis and Quercus ilex, P. sylvestris and Q. pubescens. After a nineteen-month incubation period, we found that the origin of residues (Pinus spp. stand, Quercus spp. stand or mixed stand) shaped the genetic structure of both fungal and bacterial communities. TL inputs led to higher soil N content and increased enzyme activities and bacterial biomass. Aromatic compounds and C to N ratio increased with W inputs, strongly shaped fungal communities and increased tyrosinase activity. Thus, the type of residue and the tree species identity (Quercus spp. vs Pinus spp.) appeared to modulate the balance between fungal and bacterial biomass and soil microbial diversity. Our results revealed that logging residues management, by modulating the type of residues remaining on forest floor, could have significant impacts on soil functioning by modifying both chemical properties (e.g. soil C/N ratio) and microbial structure and functions. These findings need to be supported by in natura studies since deciphering such mechanisms controlling C fluxes in forest soils has important consequences under the context of climate change.

Many forest ecosystems are developed on acidic and nutrient-poor soils and it is not yet clearly understood how forests sustain their growth with low nutrient resources. In forestry, the soil chemical fertility is commonly defined, following concepts inherited from agronomy, as the pool of plant-available nutrients in the soil at a given time compared to the nutritional requirement of the tree species. In this two-part study, Part 1 (Hansson et al., 2020) showed, through the compiled dataset of 49 forest ecosystems in France, Brazil and Republic of Congo, the limits of this definition of soil chemical fertility in forest ecosystem contexts. In this study (Part 2), we investigated the nutrient pools and fluxes between the different ecosystem compartments at 11 of the 49 sites in order to better characterize the role of the biogeochemical cycling of nutrients in the chemical fertility of forest ecosystems, and in particular the roles of the biological and geochemical components of biogeochemical cycling.\ud \ud The analysis of our dataset shows different types of biogeochemical functioning. When the geochemical component (inputs through mineral weathering and/or atmospheric inputs, capillary rise) is predominant, sufficient nutrients are provided to the plant-soil system to ensure tree nutrition and growth. Conversely, when the geochemical component of the cycle brings too few nutrients to the plant-soil system, the biological component (litterfall, plant internal cycling) becomes predominant in tree nutrition and growth. In the latter case, forest production may be high even when pools of nutrients in the soil reservoir are low because small but active nutrient fluxes may continuously replenish the soil reservoir or may directly ensure tree nutrition by bypassing the soil reservoir.\ud \ud This study highlights the necessity to include biogeochemical cycling and recycling fluxes in the definition and diagnosis methods of soil chemical fertility in forest ecosystems. We show that the chemical fertility is not only supported by the soil in forest ecosystem but by the sum of all the ecosystem’s compartments and fluxes between these pools.

Agroecosystem plant diversification at the field scale has been shown to enhance ecological pest regulation. We explored the effects of plant community composition and soil properties on the soil nematode community, with a particular interest in the regulation of banana plant-parasitic nematodes (PPN). We monitored banana phytometers (Cavendish Grande Naine cultivar) in 85 plots distributed along a plant richness gradient. Plant community composition, soil properties, abundance of bacterivorous, fungivorous and proportion of predaceous soil free-living nematodes, and abundance and damage of PPN ( Radopholus similis , Pratylenchus coffeae , Helicotylenchus multicinctus , and Meloidogyne spp.) in phytometer roots were measured. We used structural equation modeling to investigate ecological processes leading to PPN regulation. Low-stratum plant species richness, but not high-stratum, was positively related to microbivore nematode abundances, supposedly because it promoted qualitative diversity of organic inputs and micro-climatic effects supporting more soil microorganisms. Musa genotype and low-stratum plant species richness induced associational susceptibility because of differential susceptibility of Musa genotypes to PPN and because of polyphagia of PPN spreading outside the Musa family, respectively. We found no regulation of PPN by predaceous nematodes, probably because food web complexity prevented trophic cascades from propagating. Ultimately, fungivorous nematode abundance was negatively related to PPN abundance, suggesting apparent competition or increased regulation by antagonistic fungi. Our results suggest that, when facing generalist pests, cropped plant communities should be diversified to promote pest regulation but must be carefully assembled to limit pest susceptibility heterogeneity among crop genotypes and to exclude alternative host plant species.

Questions: What are the effects of abandonment on plant diversity in seminatural grasslands? Do the effects of abandonment on taxonomic and functional diversity vary along environmental gradients of climate and soil? Location: West and mid-Norway. Methods: Plant composition was surveyed in 110 subplots of 4 m2 in 14 sites across grazed and abandoned semi-natural grasslands. Climate data were extracted and soil composition analysed. To reduce the number of explanatory variables and deal with collinearity, we performed PCA. Data on the plant species vegetative height (H), leaf dry matter content (LDMC), specific leaf area (SLA), seed mass (SM) and number of seeds per plant (SNP) for 175 species were extracted from the LEDA database. Measures of plant diversity (species richness, CWM of functional traits and functional diversity (evenness and range)) were calculated for each subplot. To estimate the effects of abandonment on plant diversity and examine how these effects are moderated by gradients in soil and climate, we fitted mixed models to the data including site as a random effect. Results: Species richness in the subplots was lower in abandoned semi-natural grasslands, especially on more calcareous soils. CWM H, LDMC and SM were higher in abandoned semi-natural grasslands. CWM LDMC was only higher in the driest subplots. The ranges in H, SLA and SM, as well as evenness in LDMC were also higher in abandoned semi-natural grasslands,but the range in LDMC was lower. Conclusions: It is important to assess both taxonomic and functional diversity to understand ecosystem processes. The species pool in ecosystems influenced by a long history of intermediate grazing includes a high proportion of low stature, grazing-tolerant plant species. Abandonment of extensive land-use practices will cause a decline in taxonomic diversity (plant species richness) in such systems due to increased abundance of plants with high stature that outcompete the lower, grazing-tolerant plants. This process is predominant especially if moisture, soil fertility and pH are at intermediate levels. Changes in species communities due to abandonment will also influence ecosystem functioning, such as nutrient turnover and fodder production resilience.

International audience; Understanding the influence of soil properties and cultural practices on the communities of plant-feeding nematodes (PFNs) in agrosystems is a prerequisite for cost-efficient and environment-friendly pest control. Although plantain is a staple food crop in the Caribbean, the relationships between PFN communities and environmental factors are poorly understood in plantain agrosystems. In this study, which was conducted in Martinique (French West Indies), we quantified the PFNs in 301 root samples taken from 53 plantain fields that differed in climate, edaphic conditions, and cultural practices. The physico-chemical properties were also determined for the soil in each field. Coinertia analysis (CI) and General Linear Mixed Models (GLMMS) were used to investigate the relationships between the PFN communities, soil properties, and cultural practices. Four nematode taxa were found in plantain roots: Radopholus similis, Pratylenchus coffeae, Helicotylenchus multicinctus, and Meloidogyne spp. The lesion nematode P. coffeae was the most prominent PFN species, followed by the burrowing nematode R. similis, root-knot nematodes Meloidogyne spp., and the spiral nematode H. multicinctus. P. coffeae was significantly more abundant in ferralsols and nitisols (which have a low organic matter content and a high exchangeable cation content) than in andosols (which have a high organic matter content). Nematode abundances were apparently affected by the previous crops e.g., P. coffeae was slightly more abundant in fields where tuber plants such as sweet potato, yam, or dasheen were the previous crop; R. similis was particularly abundant in fields where banana or plantain was the previous crop; and Meloidogyne spp. were abundant in fields where a market garden was the previous crop. The results of this study will be useful for the design of PFN control methods in plantain.

We observed strong positive relationships between soil properties and forest dynamics of growth and mortality across twelve primary lowland tropical forests in a phosphorus-poor region of the Guiana Shield. Average tree growth (diameter at breast height) increased from 0.81 to 2.1 mm yr−1 along a soil texture gradient from 0 to 67% clay, and increasing metal-oxide content. Soil organic carbon stocks in the top 30 cm ranged from 30 to 118 tons C ha−1, phosphorus content ranged from 7 to 600 mg kg−1 soil, and the relative abundance of arbuscular mycorrhizal fungi ranged from 0 to 50%, all positively correlating with soil clay, and iron and aluminum oxide and hydroxide content. In contrast, already low extractable phosphorus (Bray P) content decreased from 4.4 to −1 in soil with increasing clay content. A greater prevalence of arbuscular mycorrhizal fungi in more clayey forests that had higher tree growth and mortality, but not biomass, indicates that despite the greater investment in nutrient uptake required, soils with higher clay content may actually serve to sustain high tree growth in tropical forests by avoiding phosphorus losses from the ecosystem. Our study demonstrates how variation in soil properties that retain carbon and nutrients can help to explain variation in tropical forest growth and mortality, but not biomass, by requiring niche specialization and contributing to biogeochemical diversification across this region.

In the Vakinankaratra region of the Malagasy Highlands, rainfed rice cultivation has developed rapidly, which has led to rapid degradation of soil fertility and reduced productivity. This study involved a comparison of rainfed rice in rotation with maize/Brachiaria (MZ-BR) or maize/soybean (MZ-SB) intercrops, managed by direct seeding (DS) or plowed with residue burial (PB) with conventional mineral fertilization (FM) or without fertilizer (F0). The umbric Acrisol (hyperdystric) presented an anion exchange capacity (AEC) and variable charge according to the pH. Mineralizable nitrogen (Nminz.) values decreased sharply from the surface to the deep horizons and became almost nil in the 90–120 cm horizon, while the Nminz. contents of the DS treatments were systematically 5–7% higher than the PB treatment values for a given depth. The AEC of the 0–10 cm horizon was practically zero but increased significantly with depth and reached 2.58 cmol(c) kg−1. AEC values were inversely correlated with the organic carbon (Corg.) content: AEC = 1.81–0.375 Corg. The nitrate adsorption isotherms were linear and the nitrate partition coefficients (coef_nit) were correlated with the AEC values: coef_nit = 0.3363 AEC+0.1855 (R2 = 0.954). The soil nitrate stock determinants were highlighted by the matrix of correlations of the principal component analysis: excheangeable acidity and aluminum, cation exchange capacity, ΔpH, Corg. and clay and total silt contents were particularly important for the AEC and coef_nit. The different cropping systems showed no significant impact after 12 years on soil characteristics that could improve nitrogen bioavailability. We thus recommend using organic fertilization to raise the soil pH, Corg. content and nitrogen bioavailability.

International audience; The effect of organic fertilizers on soil phosphorus (P) availability is usually mainly associated with the rate and forms of P applied, while they also alter the soil physical-chemical properties, able to change P availability. We aimed to highlight the impact of pH and organic C modifications in soil on the inorganic P (Pi) sorption capacity and availability as compared to the effect of P accumulation after mineral or organic fertilizers. We conducted a 10-years-old field experiment on an andosol and compared fields that had been amended with mineral or organic (dairy slurry and manure compost) fertilizers against a non-fertilized control. Water and Olsen extractions and Pi sorption experiments were realized on soils sampled after 6 and 10 years of trial. We also realized an artificial and ex situ alkalization of the control soil to isolate the effect of pH on Pi sorption capacity. Organic fertilizer application increased total P, pH, and organic C in soil. Pi-Olsen increased mainly with soil total P (r2 adj = 0.79), while Pi-water increased jointly with soil total P and pH (r2 adj = 0.85). The Pi sorption capacity decreased with organic fertilizer application. Artificial and ex situ alkalization of the control soil showed that Pi sorption capacity decreased with increasing pH. Our study demonstrated that, beyond the P fertilization rate, the increase in organic C content and even more so in pH induced by a decade of organic fertilizer applications in soil decreased the Pi sorption capacity and consequently increased Pi-water in soil.

International audience; Several Andean countries have planned to restore forest cover in degraded and deforested land to enhance the provision of multiple ecosystem services in response to international commitments such as the Bonn Challenge. Hydrological services, e.g. water supply, hydrological regulation and erosion mitigation, are particularly important to sustain the life of forty million people. While rapid and important forest cover changes have occurred during recent decades, critical information on the impact of tree plantations or natural regeneration in previously deforested land on hydrological services has not yet been synthesized in the context of Andean ecosystems. To help improve decisionmaking on reforestation in the Andes, we reviewed the available literature concerning the impacts of tree plantation or natural regeneration of forest on water supply, hydrological regulation and mitigation of erosion and landslides. We also examined available data on the most relevant hydrological processes such as infiltration, evapotranspiration and runoff in forest stands. Hydrological services from native forests were also included as a reference state for comparing processes and services provided by reforestation. Following systematic review protocols, we searched peer-reviewed papers and unpublished theses and reports. We synthesized studies using different methods, including meta-analyses and meta-regressions. Results show that reforestation has had clear impacts on degraded soils, through reducing water erosion of soils and risk of moderate floods, increasing soil water infiltration and topsoil organic matter (SOM). We found that 20 years of tree plantation was sufficient to recover surface runoff and sediment yield close to the levels of native forests whereas SOM (used as a proxy of soil water storage) of native forests could not be recovered by reforestation in the time scales examined. The benefits in terms of hydrological regulation are at the expense of a reduction in total water supply since forest cover in the Andes was associated with higher water use (except for certain cloud montane forests). Nevertheless, we identified an important knowledge gap on forest transpiration that should be addressed to better manage water at local and regional scales. The impact of reforestation on landslides has also been largely overlooked in the Andes. At high elevations, Andean grasslands (e.g. paramo and puna) showed an excellent capacity for hydrological regulation and erosion mitigation but also lower water use than forests. People engaged in forest restoration initiative should be aware that hydrological services may take some time for society and the environment to show clear benefits after reforestation.

The objective of our work was to evaluate soil quality in different cacao agroforestry systems (AFS) in the Colombian Amazon. We compared soil quality of AFS at the study site with soil quality of two control systems: a pasture and a secondary forest. The study was conducted at the Macagual Amazon Research Center in western Colombian Amazon. We set up eight 600 m² plots in each study system. We collected soil samples in each plot, and assessed macrofauna diversity, aggregate morphology, and physical and chemical soil properties. We integrated these variables in a General Indicator of Soil Quality (GISQ). We found GISQ values of 0.85 for forest, 0.5, 0.65 and 0.59 for AFS and 0.21 for pasture, and the values differed significantly between land uses. The establishment of cacao AFS on degraded pasture was found to significantly improve soil fertility, i.e., by 42%. The intensification level between land uses (Pasture > AFS > Forest) negatively affected macrofauna populations due to soil compaction (physical properties). Forest had the highest physical and biological quality. Our results show that AFS not only have the capacity to maintain key soil ecological functions, but also to restore soil quality of degraded pastureland. Cacao-based AFS could therefore be a key restoration strategy for degraded pastureland. These results are very important in the context of the Colombian Amazon, where cacao is currently known as the “crop of peace”.

SUMMARYFruit and vegetable farming generally involves high levels of chemical inputs despite the fact that consumers are increasingly concerned about the sanitary and organoleptic aspects of fruit quality. Pineapple is largely subject to these issues since it is dominated by conventional monocropping with high levels of agrochemical inputs due to nitrogen (N) and potassium (K) fertilisation, weed management, crop protection and flowering induction. However, low-input pineapple cropping systems are both rare and little documented. Our study aimed at replacing all or part of the chemical fertilisers used with local organic fertilisers. It was conducted on the cultivar ‘Queen Victoria’, without pesticides or herbicides, in Reunion Island. We compared the impacts of three fertilisation treatments on pineapple growth and yield, fruit quality traits, symptoms of two major fungal diseases in fruit and production costs and labour times: (i) conventional: NPK fertiliser at recommended doses (265.5 kg ha−1N–10.53 kg ha−1P–445.71 kg ha−1K); (ii) integrated:Mucuna pruriensgreen manure (240.03 kg ha−1N, 18.62 kg ha−1P, 136.11 kg ha−1K) incorporated into the soil and a half-dose of NPK fertiliser and (iii) organic:M. pruriensgreen manure incorporated into the soil and foliar applications of sugarcane vinasse from a local distillery, rich in K (14.44 g L−1). Our results showed that NPK fertilisation could be replaced by organic fertilisers as well as by integrated fertilisation. ‘D’-leaf analysis showed that vinasse supplies a largely sufficient K level for growing pineapples. With organic fertilisation, pineapple growth was slower, 199 days after planting vs. 149 days for integrated or conventional fertilisations, and fruit yield was lower, 47.25 t ha−1vs. 52.51 and 61.24 t ha−1, probably becauseM. pruriensgreen manure provided an early increase in soil mineral N, whereas N requirements are much higher four months after planting. However, the fruit weight (709.94 ± 123.53 g) was still within the size range required for the export market (600–900 g). Interestingly, organic fertilisation significantly reduced Leathery Pocket disease and produced the best quality fruit with the highest total soluble solids contents (TSS) and the lowest titratable acidity (TTA). Fruit quality was also significantly improved with integrated fertilisation, with fruit weight similar to that of conventional fertilisation. To conclude, these findings have implications for the sustainability of pineapple production and could lead to low-input innovative cropping systems that reduce production costs and develop local organic inputs.

Soil redox potential is an important factor affecting soil functioning. Yet, very few agronomy studies included soil redox potential in relation to soil processes. The objective of this study was to evaluate the spatial and temporal variation in soil redox potential and to determine the soil parameters affecting its variation. Soil redox potential, soil moisture, soil temperature, pH and bulk electrical conductivity were measured in upland rice fields during two growing seasons at six positions along an upland&ndash, lowland continuum, including two positions at the upland, two at the fringe and two at the lowlands in central C&ocirc, te d&rsquo, Ivoire (West Africa). The measurements were made at the following soil depths: 3, 8, 20 and 35 cm. Soil redox potential varied between 500 and 700 mV at the upland positions, 400 and 700 mV at the fringe positions and 100 and 750 mV at the lowland positions, and increased with soil depth. Variations in soil redox potential were driven by soil moisture, bulk electrical conductivity and soil organic carbon. We concluded that for proper interpretation of soil redox potential, sampling protocols should systematically include soil pH, moisture and bulk electrical conductivity measurements.

RATIONALE The rapid expansion of intensive monoculture in coffee farms, from the 1980's onward, resulted in coffee becoming an important commodity crop in Yunnan Province, China. This expansion was followed by a large-scale transition towards shaded coffee, starting in 2013 with the free distribution of shade tree seedlings by local governments. The current study initiates an early on follow up of this unprecedented large scale conversion by focusing on impacts of shade tree species on soil fertility at a temporally and spatially fine scale. METHODS 124 soil samples were collected in 2017-2018, both in the dry (winter) and rainy (summer) seasons, within and outside of coffee rows, below and outside of the canopy of 3 commonly found shade tree species (Bischojiajavanica, Cinnamomum camphora and Jacaranda mimosifolia). Analysis were run for chemical composition (pH, OM, N, P, K, Ca, Mg), biological communities (nematodes abundance, PLF A) and enzymatic activities (ß-glucosidase , N-acetylglucosaminidase and acid phosphatase). RESULTS 1) There was a marked seasonal effect on soil communities (higher nematodes, bacterial and fungi communities during the rainy season). P cycling also increased during the rainy season, but C and N cycling slowed down. 2) Soils below coffee plants had higher chemical fertility (OM, Ca and Mg) than paired samples outside of coffee rows. During the rainy season, soils below coffee also had more abundant soil communities (nematode, bacteria and arbuscular mycorrhiza fungi) and nutrient cycling rates (C, N and P). 3) Shade trees had a positive impact on soil chemical fertility below coffee plants (pH, OM, N, P and Ca) and a buffering effect on soil communities during the dry season (bacteria and fungi). CONCLUSIONS & PERSPECTIVES This study sets up the baseline (open coffee) and first follow up after the transition to agroforestry (5 years) on soil fertility. Results testify of the high heterogeneity of soil fertility within coffee farms, at a fine temporal and spatial scale. Importantly, shade trees were shown to have a locally positive impact on soil chemical and biological fertility after as little as 5 years, although no significant differences could be found between the 3 shade tree species. Future studies should keep monitoring changes as shade trees grow older.

In this study, diffuse reflectance spectroscopy (DRS) approach was examined for making fertiliser recommendations in the smallholder cocoa farms of Papua New Guinea (PNG). Soil samples were collected from four provinces of PNG. Soil samples from four different depths (0–10, 10–30, 30–60 and 60–90 cm) of 32 profiles in each of these sited were used to create a database of soil chemical and physical properties. Spectral reflectance values at 1 nm interval covering visible to shortwave‐infrared (350‐2500 nm) were collected for each of these soil samples to develop partial‐least‐squares regression (PLSR) models. Soil textural fractions, soil organic carbon (SOC) contents and available N were well predicted by the DRS approach with R2 values larger than 0.75. Moderate to poor estimation efficiencies were observed for remaining parameters. Nevertheless, the estimated soil attributes and their corresponding measured soil parameters were used as inputs to a fertilizer recommendation model of Soil Diagnosis to create fertilizer recommendation for a targeted cocoa yield of 1000 kg dry cocoa beans/ha. Resulting fertilizer recommendations were similar for both of these input sources (measured and DRS‐estimated) suggesting that the DRS approach may provide an easy way to create fertilizer recommendations.

International audience; The aim of this study was to assess how soil organic C (SOC) stocks and earthworm communities were modified in agroforestry systems compared to treeless control plots and within the agroforestry plots (tree rows vs alleys). We used a network of 13 silvoarable agroforestry sites in France along a north/south gradient. Total earthworm abundance and biomass were significantly higher in the tree rows than those in the control plots, but were not modified in the alleys compared to those in the control plots. Earthworm species richness, Shannon index, and species evenness were significantly higher in the tree rows than those in the alleys. Total abundance of epigeic, epi-anecic, strict anecic, and endogeic was higher in the tree rows. Surprisingly, earthworm individual weight was significantly lower in the tree rows than that in the alleys and in the control plots. SOC stocks were significantly higher in the tree rows compared to that in the control plots across all sites. Despite higher SOC stocks in the tree rows, the amount of available C per earthworm individual was lower compared to those in the control. The absence of disturbance (no tillage, no fertilizers, no pesticides) in the tree rows rather than increased SOC stocks therefore seems to be the main factor explaining the increased total abundance, biomass, and diversity of earthworms. The observed differences in earthworm communities between tree rows and alleys may lead to modified and spatially structured SOC dynamics within agroforestry plots.

Made available in DSpace on 2020-12-10T20:01:02Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-01. Added 1 bitstream(s) on 2021-07-15T15:25:04Z : No. of bitstreams: 1 S1980-50982020000100117.pdf: 1255717 bytes, checksum: cb32f05c60784ed1d46889ded03b66f3 (MD5) Anglo American Arauco Arborgen ArcelorMittal Cenibra CMPC Copener Duratex Eldorado Fazenda Campo Bom Fibria Florestal Itaquari Forestal Gerdau GMR International Paper Jari Klabin Lwarcel Montes del Plata Plantar Rigesa Suzano Vallourec Veracel University of Sao Paulo - Brazil State University of Sao Paulo - Brazil Federal University of Lavras - Brazil Federal University of Rio Grande do Norte - Brazil Colorado State University - USA North Carolina State University - USA USDA Forest Service Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The present study aimed to evaluate the correlations between productivity and eucalyptus drought (DR) response between soil attributes in two distinct climatic types in Brazil. For this, 24 experiments were installed in Brazil with four common clones in all the experiments to obtain strong edaphoclimatic contrasts, and, thus, to measure the productivity and the response to drought and to describe its relationship with the attributes of the soils. Two climatic groups were evaluated: Wet (precipitation rate: evapotranspiration between 1.0 to 2.5) and Sub-Humid (precipitation rate: evapotranspiration between 0.5 to 1.0). The attributes of the evaluated soils were: Sand, Silt, Clay, organic matter (O.M.), cation exchange capacity (CEC). For sites located in the wet climate class, CVWB correlated negatively with O.M. and clay, and positively with the sand. For DR, the correlations were observed for the Sub-Humid climate for the CEC and Sand variables, and for the Humid climate, no correlations were observed between the attributes of soils with DR. Univ Estadual Paulista, VIMEF Solucoes Florestais, Av Brasil Sul 56, BR-15385000 Ilha Solteira, SP, Brazil Univ Estadual Paulista, Dept Fitossanidade Engn Rural & Solos, Fac Engn Ilha Solteira, Av Brasil Sul 56, BR-15385000 Ilha Solteira, SP, Brazil Univ Montpellier, Montpellier SupAgro, Eco & Sols, CIRAD,INRA,IRD, 389 Ave Agropolis, F-34980 Montpellier, France Univ Estadual Paulista, Dept Ciencias Exatas, Fac Ciencias Agr & Vet, Campus Jaboticabal, BR-14884900 Jaboticabal, SP, Brazil Eldorado Brasil Celulose, BR-158,Km 231 S-N, BR-79641300 Tres Lagoas, MS, Brazil Univ Estadual Paulista, VIMEF Solucoes Florestais, Av Brasil Sul 56, BR-15385000 Ilha Solteira, SP, Brazil Univ Estadual Paulista, Dept Fitossanidade Engn Rural & Solos, Fac Engn Ilha Solteira, Av Brasil Sul 56, BR-15385000 Ilha Solteira, SP, Brazil Univ Estadual Paulista, Dept Ciencias Exatas, Fac Ciencias Agr & Vet, Campus Jaboticabal, BR-14884900 Jaboticabal, SP, Brazil

International audience; Some volcanic soils like andosols contain short-range order nanoclays (allophane) which build aggregates with a tortuous and fractal microstructure. The aim of the work was to study the influence of the microstructure and mesoporosity of the allophane aggregates on the pesticide chlordecone retention in soils. Our study shows that the allo-phane microstructure favors pollutants accumulation and se-questration in soils. We put forth the importance of the meso-porous microstructure of the allophane aggregates for pollutant trapping in andosols. We show that the soil contamination increases with the allophane content but also with the mesopore volume, the tortuosity, and the size of the fractal aggregate. Moreover, the pore structure of the allophane aggregates at nanoscale favors the pesticide retention. The fractal and tortuous aggregates of nanoparticles play the role of nanolabyrinths. It is suggested that chlordecone storage in allophanic soils could be the result of the low transport properties (permeability and diffusion) in the allophane aggregates. The poor accessibility to the pesticide trapped in the mesopore of allophane aggregates could explain the lower pollutant release in the environment.

9 pages; International audience; It has been repeatedly argued that mineral fertiliser application combined with in situ retention of crop residue biomass can sustain long-term productivity of West African soils. Using 20-year experimental data from southern Togo, a biannual rainfall area, we analysed the effect of two rates of mineral NPK fertiliser application to maize–cotton rotation on the long-term dynamics of soil C and nutrient contents, as compared with two control treatments. Mineral fertiliser treatments consisted of application to both maize (first season) and cotton (second season) the research-recommended NPK rates (Fertiliser-RR) and 1.5 times these rates (Fertiliser-1.5 RR). Control treatments consisted of cropping maize and cotton without fertiliser use (No-Fertiliser) and of double annual soil tillage (as done for planted treatments) without planting a crop (Tillage-NoCrop). Maize residue biomass was every year returned to the soil of crops planted treatments, whereas cotton stems were uprooted, piled and burnt on the experimental plots as done locally for phyto-sanitary reasons. Treatment effects were analysed through a long-term change in crop productivity, in soil C and nutrient contents. Our results indicate that productivity of maize and notably of cotton cannot be sustained in this Ferralsol without nutrient inputs. On average, maize yields without fertilisers decreased from 2 t ha−1 after woodland clearing to 0.5 t ha−1 after 10 years of cultivation, while cotton yields decreased from 1.5 to 0.5 t ha−1 only after 5 years. In spite of the need of mineral fertiliser use to sustain productivity of this soil, there was little justification to increase inputs of mineral fertiliser over the research recommended rate. Over 20-year experiment, both maize and cotton while received N, P and K inputs at the research-recommended rates produced virtually the same yields as when these rates were increased by 50%. Although C inputs to soil under RR and 1.5 RR were greater than in the No-Fertiliser control (nil for Tillage-NoCrop), and the N input was more favourable for 1.5RR, the rates in which contents of soil C and N decreased over time did not differ substantially between treatments. Soil available P decreased for all treatments, while exchangeable K concentration increased under RR and 1.5 RR and decreased in unfertilised treatments (No-Fertiliser and Tillage-NoCrop). In fertilised plots and in tillage no-planted plots, soil pH decreased more than in No-Fertiliser plots. A decline of soil pH was associated with a decline of exchangeable Ca and Mg, which were on average 20 and 40% higher in fertilised plots than in No-Fertiliser plots. We conclude that soil C and N decline in this Ferralsol was more determined by a change in soil conditions due to woodland clearance and continuous tillage than by the quantities of C or N inputs added annually.

Research data on the mechanisms of C stabilization and saturation affected by soil management systems in highly weathered soils remain scarce. Past studies have revealed the fundamental role of aggregation promoted by soil conservation practices in the physical protection of C fractions. This study is based on the hypothesis that the increased physical C protection provides sufficient time to strengthen the interaction between C fractions and soil minerals, as being the pathway for C stabilization and accumulation in highly weathered soils. Thus, the objectives of this study were to: i) evaluate the C stocks including labile and mineral-associated C fractions in soil under conventional (CT), no-till (NT) and native vegetation (NV), and, ii) assess the C saturation level in different C fractions through the use of contrasting mathematical models of C accumulation. Soil samples were collected (0–100 cm depth) from agroecosystems established in tropical (Lucas do Rio Verde) and subtropical (Ponta Grossa and Londrina) regions of Brazil. The data show that all C fractions were affected by soil management systems. However, the impact was more pronounced with the labile C fractions than with the mineral-associated C fractions. The depletion of C stock of labile fractions in the 0–5 cm layer upon conversion of NV to CT accounted for 86, 89 and 72% of total C in soil of Ponta Grossa, Londrina and Lucas do Rio Verde, respectively. On the other hand, compared to CT, restoration of 89, 15 and 12% of these labile fractions was observed at these respective sites with adoption of NT. The mineral-associated C fraction was the best fit to a C saturation model at all sites. The estimated C saturation level for this fraction was 98.1, 60.2 and 39.1 g C kg− 1 silt + clay at the Ponta Grossa, Londrina and Lucas do Rio Verde sites, respectively, which is still far from the current C content. Thus, the long-term use of NT might be the pathway for physical protection of the labile C fractions as well as strong organo-mineral associations. Together, these processes contribute to C stabilization and accumulation in highly weathered soils.

Tree anchorage is a primary function for plant survival which may reach its limit under extreme conditions such as windstorms. To better understand the processes and influential factors underlying tree anchorage, we analyzed the mechanical effects of root morphology and the material properties of roots and soil on the tree-overturning process with the recently developed finite element model RootAnchor. The root system was represented by a simplified 3D root pattern derived from an ensemble average of seven measured root systems of 19-year-old Pinus pinaster grown in sandy spodosol. Soil properties were measured by direct shear tests. Taguchi orthogonal arrays were used to examine the sensitivity of the geometric and material factors of roots and soil to tree anchorage. Tree anchorage was characterized by anchorage strength TMc and anchorage stiffness K0. Using a small number of numerical experiments, the sensitivity analysis prioritized only two key factors contributing to tree anchorage among the 34 factors considered. The results showed root morphological traits that played a dominant role in the material properties of roots and soil in tree anchorage. Taproot depth, the dimensions of the Zone of Rapid Taper (ZRT) and basal diameter of the windward shallow roots were the key factors contributing to TMc (variations > 8%). The dimensions of the taproot, root and soil stiffness, and the basal diameter of the leeward shallow roots were the most active factors for K0 (variations > 10%). These results provide insight into simplified tree anchorage expressions for the prediction of wind-induced uprooting.

Mediterranean forests are found in the Mediterranean basin, California, the South African Cape Province, South and southwestern Australia and parts of Central Chile. They represent 1.8 % of the world forest areas of which the vast majority is found in the Mediterranean basin, where historical and paleogeographic episodes, long-term human influence and geographical and climatic contrasts have created ecosystemic diversity and heterogeneity. Even if evergreen is dominant, deciduous trees are also represented, with different forest types including dense stands with a closed canopy (forests sensu stricto) and pre-forestal or pre-steppic structures with lower trees density and height. The Mediterranean basin is also a hot spot of forest species and genetic diversity, with 290 woody species versus only 135 for non-Mediterranean Europe. However, the characteristics of the Mediterranean area (long-standing anthropogenic pressure, significant current human activity and broad biodiversity) make it one of the world’s regions most threatened by current changes. Four examples of Mediterranean forest types, present in south and north of the Mediterranean basin and more or less threatened, are developed in order to show that linking “hard sciences” and humanities and social sciences is necessary to understand these complex ecosystems. We show also that these forests, in spite of specific climatic constraints, can also be healthy and productive and play a major ecological and social role. Furthermore, even if the current human activity and global change constitute a risk for these exceptional ecosystems, Mediterranean forests represent a great asset and opportunities for the future of the Mediterranean basin.