Well-drained Soils Research Articles

Tibouchina granulosa Purple Glory Tree

This document provides an overview of Tibouchina granulosa, commonly known as the purple glory tree. It describes the plant’s characteristics, including its moderate growth rate, dense foliage, and large, vibrant purple flowers that bloom throughout much of the year. The plant can be trained into a small tree or maintained as a shrub, making it versatile for various landscape uses such as screens, specimen plants, or container gardening. The document also covers the plant’s cultural requirements, including its preference for full sun and well-drained soil, as well as its propagation methods and pest resistance. Emphasis is placed on its suitability for USDA hardiness zones 10B through 11. Original publication date October, 1999.

Pittosporum tobira 'Wheeleri' Wheeler's Dwarf Pittosporum

This document provides an overview of Wheeler’s dwarf pittosporum, an evergreen shrub known for its compact, rounded form and dark green foliage. It details the plant’s characteristics, including its moderate growth rate, dense texture, and specific leaf and flower attributes. The document also covers the plant’s preferred growing conditions, such as its need for well-drained soil and partial to full sun exposure, and highlights its uses in landscaping, particularly in coastal areas. Additionally, it notes the plant’s susceptibility to certain pests and diseases, emphasizing the importance of proper maintenance and care. Original publication date October 1999.

Conservation agriculture practices: Adaptation and yield

Abstract Conservation agriculture (CA) has been promoted in sub-Saharan Africa (SSA) to increase crop productivity and for climate change adaptation. CA is the simultaneous application of the three principles: no-till, mulch cover, and crop diversification. The potential benefits are largely linked to moisture conservation of crop residues, reduced run-off and erosion, increased infiltration, and reduced evaporative losses. This study uses a review of recent literature in SSA under rain-fed conditions to synthesize evidence of the effect of CA on yield and climate change adaptation. Web of Science and Google Scholar were used for literature searches. Crop productivity results in the literature suggest that CA increases yield in certain circumstances such as well-drained soils and moderate rainfall, and that poorly drained soils in combination with excessive rains lead to depressed yields. The yield benefits reported range from as low as 4% and as high as 16%, with negative effects also reported. Stability analysis used as a proxy for adaptation revealed only a marginal benefit of CA above conventional practices suggesting the significant effect of seasonal rainfall on crop productivity. The results suggest the need to target CA practices to different agroecologies and other pragmatic local agronomic practices that may be required in cases of excessive rainfall and extended mid-season dry spells. The benefits of CA reported are largely plot level, and only a few studies consider the whole farm, especially within the holistic livelihood framework. In addition, adoption of CA remains low among smallholder farmers, and the widespread benefits of the practices cannot be realized at multiple scales.

Vegetation patterns associated with nutrient availability and supply in high-elevation tropical Andean ecosystems

Abstract. Plants absorb nutrients and water through their roots and modulate soil biogeochemical cycles. The mechanisms of water and nutrient uptake by plants depend on climatic and edaphic conditions, as well as the plant root system. Soil solution is the medium in which abiotic and biotic processes exchange nutrients, and nutrient concentrations vary with the abundance of reactive minerals and fluid residence times. High-altitude ecosystems of the tropical Andes are interesting for the study of the association between vegetation, soil hydrology, and mineral nutrient availability at the landscape scale for different reasons. First of all, because of low rock-derived nutrient stocks in intensely weathered volcanic soils, biocycling of essential nutrients by plants is expected to be important for plant nutrient acquisition. Second, the ecosystem is characterized by strong spatial patterns in vegetation type and density at the landscape scale and hence is optimal to study soil-water–vegetation interactions. Third, the area is characterized by high carbon stocks but low rates of organic decomposition that might vary with soil hydrology, soil development, and geochemistry, all interconnected with vegetation. The páramo landscape forms a vegetation mosaic of bunch grasses, cushion-forming plants, and forests. In the nutrient-depleted nonallophanic Andosols, the plant rooting depth varies with drainage and soil moisture conditions. Rooting depths were shallower in seasonally waterlogged soils under cushion plants and deeper in well-drained soils under forest and tussock grasses (>100 cm). Vegetation composition is a relevant indicator of rock-derived nutrient availability in soil solutions. The soil solute chemistry revealed patterns in plant-available nutrients that were not mimicking the distribution of total rock-derived nutrients nor the exchangeable nutrient pool but clearly resulted from strong biocycling of cations and removal of nutrients from the soil by plant uptake or deep leaching. Soils under cushion plants showed solute concentrations of Ca, Mg, and Na of about 3 times higher than forest and tussock grasses. Differences were even stronger for dissolved Si with solute concentrations that were 16 times higher than forest and 6 times higher than tussock grasses. Amongst the macronutrients derived from lithogenic sources, P was a limiting nutrient with very low solute concentrations (<1 µM) for all three vegetation types. In contrast K showed greater solute concentrations under forest soils with values that were 2 to 3 times higher than under cushion-forming plants or tussock grasses. Our findings have important implications for future management of Andean páramo ecosystems where vegetation type distributions are dynamically changing as a result of warming temperatures and land use change. Such alterations may lead not only to changes in soil hydrology and solute geochemistry but also to complex changes in weathering rates and solute export downstream with effects on nutrient concentrations in Andean rivers and high-mountain lakes.

Production patterns of loblolly pine plantations along a geographic gradient in southern Brazil

Pinus taeda plantations depend directly on the supply of resources (light, water, and nutrients) available to the stand. However, studies quantifying edaphic and climatic factors in P. taeda stands are scarce. This study aimed to identify the main edaphic, climatic and stand factors that influence the productivity and growth pattern of P. taeda plantations in southern Brazil. A total of 24 stands, ranging between 8 and 10 years old were evaluated. Biometric variables such as height, diameter at breast height (DBH), stem analysis, growth rings, specific gravity, and soil chemical and physical variables were evaluated. Site index (SI), stem biomass, mean annual increment without bark (MAI) and correlations between variables were calculated. We observed that by nine years after planting, none of the plots had reached their maximum growth; and MAI, standing stem biomass and SI ranged from 15 to 35 m³ ha−1 year−1, 56–131 Mg ha−1, and 12–19 m, respectively, with higher values in Três Barras site. Stem biomass were positively related with SI (r = 0.89), and stem production was related with higher available water content (r = 0.41), warm temperatures (r = 0.61), and higher relative air humidity (r = 0.58). The study corroborates the role of nutrients, well-drained soils, mild climatic conditions, and low water deficit to explain the high yields of P. taeda in Brazil compared to other locations around the world. Based on these results, studies on fertilization, genetic material, and more frequent use of stem analysis, associated with X-ray densitometry, are recommended for P. taeda.

Predicting the changing insect threat in the UK heritage environment

Environmental changes affecting museums and historic properties will probably result in increased numbers of insect pests or new species. Databases such as WhatsEatingYourCollection (WEYC) and the Global Biodiversity Information Facility have been used along with academic publications to predict such changes in the research presented here. The species mix in the WEYC database seems consistent across major London historic properties. Overall, common silverfish (Lepisma saccharinum) are often reported, although in future there may be an increase in other species such as Ctenolepisma longicaudatum and Ctenolepisma calvum given their increased frequency. Dermestidae (carpet and furniture beetles) may benefit from wood with increasing moisture content, and although not especially abundant, Attagenus smirnovi (brown carpet beetle) and Reesa vespulae (skin beetle) may increase as they have done on the European continent. Tineola bisselliella, a damaging moth, has invoked increasing concern over the last two decades and Cryptophagus spp. (fungus beetles) could mobilise fungal spores under a future climate more favourable to germination. Lyctus brunneus (powderpost beetle) may find future conditions favourable and attack sapwoods used in repairs. Furthermore, Reticulitermes flavipes (subterranean termite) is potentially an accidental import to the UK and may become more common given current temperatures are suitable for survival in well-drained loamy soils, and future climates would allow a presence in the north of England. Warmer conditions can lead to the presence of new species or a migration of species across the British Isles and their spread can also be encouraged through the loan of objects or on packing materials. Factors other than climate, such as changing indoor habitats, new food sources and novel uses of heritage venues can also encourage expanding insect populations. This article summarises these predicted changes in species distribution and outlines their potential threat to heritage.

Suitability of treated wastewater for irrigation and its impact on groundwater resources in arid coastal regions: Insights for water resources sustainability

Water scarcity threatens agriculture and food security in arid regions like Saudi Arabia. The nation produces significant quantities of municipal wastewater, which, with adequate treatment, could serve as an alternative water source for irrigation, thereby reducing reliance on fossil and non-renewable groundwater. This study assessed the appropriateness of using treated wastewater (TWW) for irrigation in a dry coastal agricultural region in Eastern Saudi Arabia and its impact on groundwater resources. Field investigations were conducted in Qatif to collect water samples and field measurements. A multi-criteria approach was applied to evaluate the TWW's suitability for irrigation, including complying with Saudi Standards, the Irrigation Water Quality Index (IWQI), the National Sanitation Foundation water quality index (NSFWQI), and the individual irrigation indices. In addition, the impact of TWW on groundwater was assessed through hydrogeological and isotope approaches. The results indicate that the use of TWW in the study area complied with the Saudi reuse guidelines except for nitrate, aluminum, and molybdenum. However, irrigation water quality indices classify TWW as having limitations that necessitate the use for salt-tolerant crops on permeable and well-drained soils. Stable isotopic analysis (δ2H, δ18O) revealed that long-term irrigation with TWW affected the shallow aquifer, while deep aquifers were minimally impacted due to the presence of aquitard layer. The application of TWW irrigation has successfully maintained groundwater sustainability in the study area, as evidenced by increased groundwater levels up to 2.3 m. Although TWW contributes to crop productivity, long term agricultural sustainability could be enhanced by improving effluent quality, regulating irrigation practices, implementing buffer zones, and monitoring shallow groundwater. An integrated approach that combines advanced wastewater treatment methods, community involvement, regulatory oversight, and targeted monitoring is recommended to be implemented.

Predicting Redox Conditions in Groundwater at a National Scale Using Random Forest Classification.

Redox conditions in groundwater may markedly affect the fate and transport of nutrients, volatile organic compounds, and trace metals, with significant implications for human health. While many local assessments of redox conditions have been made, the spatial variability of redox reaction rates makes the determination of redox conditions at regional or national scales problematic. In this study, redox conditions in groundwater were predicted for the contiguous United States using random forest classification by relating measured water quality data from over 30,000 wells to natural and anthropogenic factors. The model correctly predicted the oxic/suboxic classification for 78 and 79% of the samples in the out-of-bag and hold-out data sets, respectively. Variables describing geology, hydrology, soil properties, and hydrologic position were among the most important factors affecting the likelihood of oxic conditions in groundwater. Important model variables tended to relate to aquifer recharge, groundwater travel time, or prevalence of electron donors, which are key drivers of redox conditions in groundwater. Partial dependence plots suggested that the likelihood of oxic conditions in groundwater decreased sharply as streams were approached and gradually as the depth below the water table increased. The probability of oxic groundwater increased as base flow index values increased, likely due to the prevalence of well-drained soils and geologic materials in high base flow index areas. The likelihood of oxic conditions increased as topographic wetness index (TWI) values decreased. High topographic wetness index values occur in areas with a propensity for standing water and overland flow, conditions that limit the delivery of dissolved oxygen to groundwater by recharge; higher TWI values also tend to occur in discharge areas, which may contain groundwater with long travel times. A second model was developed to predict the probability of elevated manganese (Mn) concentrations in groundwater (i.e., ≥50 μg/L). The Mn model relied on many of the same variables as the oxic/suboxic model and may be used to identify areas where Mn-reducing conditions occur and where there is an increased risk to domestic water supplies due to high Mn concentrations. Model predictions of redox conditions in groundwater produced in this study may help identify regions of the country with elevated groundwater vulnerability and stream vulnerability to groundwater-derived contaminants.

Contrasting processes of microbial anabolism and necromass formation between upland and paddy soils across regional scales

Well-drained upland soils generally have stronger microbial catabolism during organic C transformation than water-logged paddy soils. However, the intensity of microbial anabolism and necromass formation processes in these contrasting agricultural soils is unclear. To quantify these processes, 40 pairs of adjacent upland and paddy soils collected from four climates (mid-temperate, warm temperate, subtropics, and tropics) across eastern China were incubated with 13C-labeled root exudates under simulated field water conditions for 50 days. Upland soil collected from warm temperate exhibited a higher 13C incorporation into living microbial biomass than other climates. In contrast, the lowest newly formed necromass was detected due to the inhibition of fungal anabolism under the high pH condition. Paddy soils collected from cooler climates (mid-temperate and warm temperate) exhibited faster microbial biomass growth than those from warmer climates (subtropics and tropics). Still an opposite trend was observed for microbial necromass accumulation, possibly because of the faster turnover rate of microbial biomass induced by the high N availability in warmer climates. Regardless of climates, 13C incorporated into living microbial biomass (phospholipid fatty acids) was 1.4–2.6 times higher in upland than paddy soils, resulting in 1.8–3.9 times greater accumulation of newly-formed microbial necromass in the former. This was mainly caused by the stronger fungal anabolism (2.5–5.6 times higher) due to the oxygen-sufficient condition of upland soil. Our findings highlighted the weaker accumulation but stronger stability of organic C stored in upland soils because of the greater microbial catabolism and anabolism during organic C transformation.

Assessing the performance of farm soil-based and hybrid biofilters for methane abatement

ABSTRACT Mitigating methane (CH4) emissions using methanotrophs (methane-oxidizing bacteria, MOB), is a simple, energy efficient and cheap technology. The abundance and distribution of MOB in the environmental samples is critical for efficient removal of emitted CH4 from any source. This study evaluated the performance of farm soils without and with cheap, easily accessible bulking materials as sustainable hybrid biofilter media. Soil-only biofilters removed up to 865 ± 19 g CH4 m−3 d−1 with well-drained organic carbon-rich soils compared with 264 ± 14 g CH4 m−3 d−1 for poorly drained soil. The removal efficiency decreased with increasing flow rate (0.16→0.24 L min−1) and subsequent priming could not return soil biofilters to their previous removal rate. Hybrid biofilters using organic, carbon-rich soils and compost removed up to 2698 g CH4 m−3 d−1 (flow rate 0.35 L min−1). Increasing CH4 flow rates also reduced their efficiency, but the hybrid biofilters with compost quickly regained most of their efficiency and removed up to 2262 g CH4 m−3 d−1 (flow rate 0.3 L min−1) after remixing of biofilter media. These results show that hybrid biofilters removed higher CH4 than soil-only biofilters and were also more resilient. The MOB gene abundance results complement the CH4 removal capacity of both soil-only and hybrid biofilter materials used. The more aerobic, carbon-rich soils had more abundant MOB than the poorly drained soil. The most porous hybrid biofilter with compost and more available nutrients to sustain bacterial growth and activity had the highest MOB abundance and removed the most CH4.

Spatial variation of soil organic matter and metal mobility in wetland soils: Implications for biogeochemical processes in lateritic landscape

The evolution of the lateritic landscape over time changes the path of pedogenesis and soil hydrology. The occurrence of upland wetlands in the savannah flat plateau transforms well-drained lateritic soils into hydric soils enriched in organic matter. We investigated the composition of soil organic matter (SOM) produced in a wetland and their link with the mineral constituents of soil and their contribution to the mobility of Si, Fe, and Al in the soil. Six tranches were opened in a soil catena located from the plateau toward the center of the wetland, representing different hydromorphic features. Soil morphology was described, and chemical, physical and mineralogical analyses were performed to evaluate soil properties. Chemical fractionation of Soil Organic Matter (SOM) was performed and total organic carbon (TOC), dissolved organic carbon (DOC), particulate organic carbon (POC), and water-extractable organic matter (WEOM) were determined in the soil horizons. Metal complexing properties of DOM were determined using an excitation-emission matrix of fluorescence. The occurrence of Fe eluviation in the superficial horizons, Fe2O3 enrichment in the mottled horizons, and ferricrete formation in the center of the wetland were observed. Geochemical transfer assessment and the variation of oxides within the horizons showed that Fe2O3 and SiO2 were more mobile than Al2O3, whose variability in the gley horizon reflected the mobility of Fe2O3 and SiO2. The stability constants of Al and Cu showed an increase with the depth for WEOM and SOM. The pattern of the organic carbon fraction varied according to the level of hydromorphy and soil depth. It was also observed an increase in the C/N ratio with depth, possibly related to the reduced bioavailability of DOC due to its adsorption with soil solids.

Organic soils in Southeastern Brazilian highlands: formation and relations to vegetation history

Well-drained organic soils form in distinctive highland environments in contrast to wetland organic soils. Similar to the concept of endemic soils, they are restricted to specific geographic areas due to a unique combination of soil-forming factors. In this contribution, we aim to improve the pedological knowledge of the Brazilian highlands, focusing on well-drained organic soils. The objective was to propose a soil formation scheme for the study area, combining traditional techniques and paleoenvironmental reconstruction (phytoliths, isotypes, dating). Organic soils were formed by litter accumulation in two pedoenvironments: (1) directly on bedrock in the high-elevation grasslands, by the processes of addition and transformation of the litter, which constitute the parent material from these soils; and (2) in upper-montane forests, with organic horizons formed above mineral horizons. In both conditions, the cold and humid climate and vegetation (organisms) are the main soil-forming factors, reducing organic matter decomposition, and influencing the physical and chemical soil properties. Phytolith records and isotopic composition of soil organic matter indicated four environmental phases: Phase I (before ∼18,9k yr BP). A cooler and drier climate than present, with predominance of subtropical grassland vegetation and fire events; Phase II (∼18,9k yr BP to ∼11,1k yr BP). A slightly increase of humidity, decrease of fire events, and expansion of forest formations, with rare presence of Araucaria angustifolia; Phase III (from ∼11,1k years BP) increase in humidity, the establishment of current climate conditions (cold and humid climate, typical of Southeastern Brazilian highlands), and significant presence of Araucaria in upper-montane forests; Phase IV (present) environmental changes related to increased fire events, reduction of Araucaria and increase of Bambusoid, Arecaceae and C4 plants, possibly resulted from human activities. This contribution enhances the understanding of well-drained organic soils in the Southeastern Brazilian highlands, showing their unique formation under cold and humid climates, influenced by vegetation history and environmental phases, as revealed through phytolith records, isotopic composition, and dating.

Processing of an underutilized fruit crop sumac berry from the north-eastern region of India: A Review

Sumac, a native wild fruit crop with over 250 varieties, grows 12-25 feet in sub-tropical to tropical climates with well-drained soil, creamy white blooms, and waxy-coated seeds. R. chinensis Mill. is a promising natural medicine with health benefits, anti-cancer, antiinflammatory, antimicrobial, antiviral, and antidiarrheal properties. Its methanolic extract has reduced kidney stone risk, suppresses bone resorption, and inhibits HIV-1 activity. Evidence suggests that R. chinensis contains flavonoids, phenolics, and triterpenoids because of its excellent nutritional profile, and distinctive tangy flavor, Rhus chinensis has enormous potential as a niche fruit crop. Rhus chinensis Mill. fruits are notably rich in carbohydrates(15.49 ± 1.60%), ascorbic acid (840.45 ± 86.44 μg/g), and minerals like potassium and phosphorus. While the fruit pulp is naturally acidic, processing it into tablets and candies reduces its acidity by 3.70% and 3.68%, enhancing its palatability and potential health benefits. Sumac processing typically adheres to traditional methods, with the berries sun-dried for approximately one week. Additionally, dried fruits, jams, juices, and tea can be made from Rhus chinensis. Some difficulties are raising customer awareness, conquering ignorance about cultivation, and adjusting its flavor to Western palates. Breeding programs, post-harvest technology, marketing, and sustainable farming methods are needed to overcome these obstacles.

Application of the ensemble of T&P models for estimating the respiration of forest soils in the zone of temperate continental climate

The aim of the study was by using an ensemble of T&P models, i.e. empirical models of soil respiration dependent on temperature, precipitation and other meteorological and soil parameters, to show the dependence of the choice of optimal empirical models of soil respiration on the soil types in forest ecosystems, in this case Entic Podzol and Haplic Luvisol, as well as on options for parameterizing models using soil or air temperatures, precipitation and soil organic carbon stock. Location and time of the study. Temperate continental climate zone of the Central Russia: mixed forest in the north shore of Oka River and deciduous forest on the south shore of Oka River. The data were collected in 1998–2022. Methods. An ensemble of empirical models of soil respiration was used, linking soil respiration to monthly mean soil or air temperatures and precipitation and soil organic carbon stock. At the same time, a method for determining soil respiration at zero degrees was proposed based on the results of a comparative analysis of simulated data with field measurements. Results. For the forest Entic Podzol, i.e. the well-drained soil poor in organic carbon, the model that relates soil respiration to soil temperature, precipitation and organic carbon storage was the best, whereas for Haplic Luvisol, i.e. the soil with good water retention capacity, the Reich-Hashtmoto model with a quadratic dependence on temperature at an exponent point was the best model. Conclusions. When choosing optimal empirical models of soil respiration, it is important to take into account such soil parameters as organic carbon stock and the ability to retain water.

Revised Approach, Conditions, and Cultivation Practices of Cicer arietinum L. in the Cerrado

Chickpeas, a nutritionally rich legume that is widely appreciated in world cuisine, require specific care for effective cultivation. Its ability to thrive in hot climates, poor soils, and well-drained soils is essential, as it makes it possible to grow crops in different regions. The ideal planting period, typically in the spring, requires attention to seed depth and spacing, as well as careful irrigation during flowering and pod formation to avoid fungal problems. Its ability to fix nitrogen is an advantage, but controlling pests and diseases such as aphids and powdery mildew is vital for ensuring a healthy harvest. The harvest, carried out after the drying of the plants, requires careful procedures for the storage of the grains, avoiding damage by fungi. Chickpea cultivation is constantly evolving, adopting modern practices to ensure efficiency and sustainability, driven by its nutritional significance and crucial presence in global cuisine, encouraging continuous improvements in production to meet growing demand. The research adopted methods based on the methodological framework outlined in the study "Factorial Experimental Design: A Brief Review".

Nitrogen fertilizer and pronitridine rates for corn production in the Midwest U.S.

ContextReducing nitrogen (N) losses can be accomplished by applying recommended N rates and using nitrification inhibitors (NI). In some agricultural systems, managing N application rate or using a NI could improve N use efficiency and increase crop yields. ObjectiveThe objectives of this 13 site-year study were to determine the agronomic optimum N rate (AONR) application rate using linear plateau and quadratic plateau models, determine the optimum pronitridine rate when applied with 70 % of the recommended N amount, and evaluate the effect of nitrapyrin and pronitridine on corn (Zea mays L.) yield. MethodsIn this experiment, pronitridine and nitrapyrin were used as NIs and were applied in the fall and spring. This research was conducted in the US in Illinois (IL), Missouri (MO), and Nebraska (NE) from 2016 to 2019. ResultsThe AONR varied from 176 to 291 kg ha-1 in different site-years. The optimal pronitridine rate was predicted using the generalized additive model (GAM) for each site. A pronitridine rate of 5.6 g kg-1 N and 8.2 g kg-1 N was recommended for well drained (NE) and poorly drained (MO and IL) sites, respectively. The pronitridine application at an average rate of 5.6 g kg-1 N increased corn grain yield 4 % compared to the non-treated control. Economic analysis showed an increase in gross margin returns of 32–67 $ ha-1 in poorly drained soils (MO & IL) when applied at 8 g kg-1 with fall and spring N application. Whereas 10–30 $ ha-1 higher gross margins were observed in well-drained soils (NE) with an application of 4 g kg-1 of pronitridine for fall and spring application timings. ConclusionThe differences in AONR and pronitridine rate prediction observed in this study emphasize the variability caused by factors such as the soil, environment, and their interaction with the N cycle. When we evaluated pronitridine and nitrapyrin with all site years combined, no differences between the two NIs were observed in terms of corn yield production. SignificanceOur findings are the first to quantify corn yield response for pronitridine applications at different locations and multiple rates in the Midwest U.S. The results of this study highlight the optimum pronitridine optimum rate for improved corn yield in poorly drained and well-drained soils in the Midwest U.S. Profitability of pronitridine can be improved by applying an optimum rate based on N requirements and soil conditions.

Are western European oak forests man-made constructs? The pedoanthracological perspective

Fagus sylvatica L. is among the most competitive trees in European temperate deciduous forests on well-drained but not too dry soils and is known to be a major species in the mature stages of natural succession over large areas. However, even under favourable conditions, it is often sporadic or even absent from present-day stands whereas Quercus spp. are dominant. Based on written sources, the predominance of Quercus spp. has been identified as a potential heritage of historical management. To test the hypothesis that past human practices caused the replacement of Fagus by Quercus spp. on well-drained soils, we carried out a soil charcoal analysis on current mature Quercus spp. stands in 19 forest sites of the Lorraine Plateau in northeastern France. ‘Mega-charcoal’ assemblages were extracted from soil trenches and taxonomically identified. Our results, based on more than 5600 charcoal pieces, identified 19 taxa and showed the presence of Quercus and Fagus in all sites. Quercus was dominant, followed by Carpinus and Fagus, as it is today in the on-site forests, except for Fagus, which is not observed in any of the studied stands. Other taxa, such as Prunus, Populus, Betula, were present at lower abundances, occurring in only a few sampling sites. The 71 radiocarbon dates indicated that i) a Fagus forest had been in place during the Bronze Age, without any dated oak pieces found; ii) Quercus became common from the end of the Bronze Age, iii) and was mixed with Fagus from the middle of the Iron Age. These results provide a new evidence that historical forest management in western Europe caused the replacement of Fagus by Quercus, and therefore the manipulation of forest stand species composition started during the Bronze Age.

A century of nitrogen dynamics in agricultural watersheds of Denmark

Intensive agriculture has been linked to increased nitrogen loads and adverse effects on downstream aquatic ecosystems. Sustained large net nitrogen surpluses have been shown in several contexts to form legacies in soil or waters, which delay the effects of reduction measures. In this study, detailed land use and agricultural statistics were used to reconstruct the annual nitrogen surpluses in three agriculture-dominated watersheds of Denmark (600–2700 km2) with well-drained loamy soils. These surpluses and long-term hydrological records were used as inputs to the process model ELEMeNT to quantify the nitrogen stores and fluxes for 1920–2020. A multi-objective calibration using timeseries of river nitrate loads, as well as other non-conventional data sources, allowed to explore the potential of these different data to constrain the nitrogen cycling model. We found the flux-weighted nitrate concentrations in the root zone percolate below croplands, a dataset not commonly used in calibrating watershed models, to be critical in reducing parameter uncertainty. Groundwater nitrate legacies built up in all three studied watersheds during 1950–1990 corresponding to ∼2% of the surplus (or ∼1 kg N ha yr−1) before they went down at a similar rate during 1990–2015. Over the same periods active soil nitrogen legacies first accumulated by approximately 10% of the surplus (∼5 kg N ha yr−1), before undergoing a commensurate reduction. Both legacies appear to have been the drivers of hysteresis in the diffuse load at the catchments’ outlet and hindrances to reaching water quality goals. Results indicate that the low cropland surpluses enforced during 2008–2015 had a larger impact on the diffuse river loads than the European Union’s untargeted grass set-aside policy of 1993–2008. Collectively, the measures of 1990–2015 are estimated to have reset the diffuse load regimes of the watersheds back to the situation prevailing in the 1960s.

Arctic soil methane sink increases with drier conditions and higher ecosystem respiration

Arctic wetlands are known methane (CH4) emitters but recent studies suggest that the Arctic CH4 sink strength may be underestimated. Here we explore the capacity of well-drained Arctic soils to consume atmospheric CH4 using >40,000 hourly flux observations and spatially distributed flux measurements from 4 sites and 14 surface types. While consumption of atmospheric CH4 occurred at all sites at rates of 0.092 ± 0.011 mgCH4 m−2 h−1 (mean ± s.e.), CH4 uptake displayed distinct diel and seasonal patterns reflecting ecosystem respiration. Combining in situ flux data with laboratory investigations and a machine learning approach, we find biotic drivers to be highly important. Soil moisture outweighed temperature as an abiotic control and higher CH4 uptake was linked to increased availability of labile carbon. Our findings imply that soil drying and enhanced nutrient supply will promote CH4 uptake by Arctic soils, providing a negative feedback to global climate change.

Conventional soil test phosphorus failed to accurately predict dissolved phosphorus release in agricultural hydromorphic soils in Brittany, Western France

Researches have proved that agricultural phosphorus (P) loss contributes significantly to surface water eutrophication. Various soil test P (STP) methods have been developed to assess the P loss risk from agricultural soils. In the intensively-cultivated Brittany region of Western France, hydromorphic soils in wetland domains exhibit high risks of leaching and transferring dissolved P - the most bio-available form of P - to surface waters. It remains unclear whether STP conventionally developed for well-drained soils can accurately predict the risk of dissolved P release from these hydromorphic soils. In this study, we measured the dissolved reactive P (DRP) concentrations in soil solutions sampled in situ from 26 hydromorphic soils in the Brittany region and examined their relationship with several STPs available on the corresponding soils, such as the degree of soil P saturation, the equilibrium soil P concentration, or the soil Olsen P, Dyer P, and water extractable P contents. DRP concentrations ranged from 0.01 to 0.310 mg P l−1 (mean = 0.075 mg P l−1), highlighting the potential of hydromorphic soils as hotspots for DRP release in agricultural landscapes. Correlations between DRP concentrations and STPs were relatively weak (0.09 < r2 < 0.64), indicating that conventional STPs are generally unable to accurately predict the DRP release risks in hydromorphic soils. Tentatively, Olsen P showed promises as a useful risk indicator, with a relatively high r2 value of 0.6 and wide inclusion in the current STP database, especially in the Brittany region. Nevertheless, this hypothesis requires further evaluation with additional data. This study confirms the high risk of dissolved P release from hydromorphic soils in agricultural wetland domains and emphasizes the need for developing specific risk assessment tools to these hydromorphic soils.