Soil Charcoal Research Articles

Naturally Deposited Charcoal Enhances Water Retention Capacity of Subtropical Forest Soils

Charcoal, a byproduct resulting from incomplete combustion of biomass in fire events, can modify the physical properties of soil due to its high porosity and large surface area. To evaluate the impact of fire-deposited charcoal on soil hydraulic characteristics, soil–charcoal mixtures were analyzed to investigate the effects of different application doses (wt%: 0, 1%, 3%, 5%, 10% and 20%) of charcoal on soil bulk density (BD), porosity (total, capillary, and non-capillary), residual moisture after free drainage (RM), saturated water content (SC), and saturated hydraulic conductivity (Ks) of loamy and sandy soils collected from subtropical forests in south China. The results showed that the impact of charcoal on soil’s physical and hydraulic properties depends on the soil type and the application dose. The incorporation of charcoal significantly decreased the BD of sandy soil (p < 0.001), while a significant decrease in BD in loamy soil was only observed as a result of the higher application doses (10% and 20%) (p < 0.001). Charcoal application doses of 5% or higher led to a significant increase in the total porosity (TP) of sandy soil (p < 0.001) and doses of 3% and 20% resulted in a significant increase in the TP of loamy soil (p < 0.001). The capillary porosity (CP) of both sand and loamy soils significantly increased when charcoal was applied at doses of 3% or higher (p < 0.001). The minimum charcoal application dose that significantly increased the RM in sandy soil was 5%, while for loamy soil, the minimum effective dose was 10%. Charcoal applied at a dose of 3% significantly increased the Ks of sandy soil (p < 0.001), while no significant effect on Ks was observed for loamy soil (p > 0.05). Collectively, our findings suggest that fire-derived charcoal enhances the soil water-retention capacity in subtropical forests, with the effects becoming more pronounced at higher application doses and being particularly notable in sandy soil compared to loamy soil.

Tree demographics and soil charcoal evidence of fire disturbances in an inaccessible forest atop the Mount Lico inselberg, Mozambique

Tree demographics and soil charcoal evidence of fire disturbances in an inaccessible forest atop the Mount Lico inselberg, Mozambique

Relationship between extreme species richness and Holocene persistence of forest-steppe grasslands in Transylvania, Romania

The most species-rich grasslands worldwide are known from the Carpathian Mts and their periphery in East-Central Europe. They occur in forest-steppe regions, transitional between temperate forest and arid steppe biomes. Their climate, largely suitable for forests, raises questions about the origin of these grasslands. Have they been forested in the past, or locally maintained through a disturbance regime? We addressed these questions to contribute to the broader understanding of Holocene dynamics of open habitats in temperate Europe. We employed soil charcoal analysis and soil morphology to reconstruct past representation of woody species with fine spatial resolution. Our study area was Romanian Transylvania, a region renowned for a well-developed forest-steppe. Six soil profiles along a climatic gradient were assessed: four in forest-steppe grasslands, two in grasslands in adjacent forest region (forest grasslands). The results revealed profound differences between forest-steppe and forest grasslands. Forest-steppe profiles showed Phaeozems with low specific anthracomass of woody species and continuous dominance by Juniperus, suggesting a long-term presence of grasslands. Forest grasslands showed Luvisols with higher anthracomass and abundant charcoal of broad-leaved trees, indicating establishment after deforestation. The high radiocarbon ages of charcoals in basal soil horizons point to a glacial origin of soils and the link of forest-steppe grasslands to glacial forests. Siberian hemiboreal forests and related grasslands may be modern analogues of the reconstructed ecosystems, sharing many species with present day forest-steppe. We suggest that disturbances such as fire, herbivore grazing, and human activities have played an important role in shaping the forest-steppe over time, contributing to the formation of today’s richest grasslands.

Reproducible protocol for the extraction and semi-automated quantification of macroscopic charcoal from soil.

Charcoal fragments preserved in soils or sediments are used by scientists to reconstruct fire histories and thereby improve our understanding of past vegetation dynamics and human-plant relationships. Unfortunately, most published methods for charcoal extraction and analysis are incompletely described and are therefore difficult to reproduce. To improve the standardization and replicability of soil charcoal analysis, as well as to facilitate accessibility for non-experts, we developed a detailed, step-by-step protocol to isolate charcoal from soil and to efficiently count and measure charcoal fragments. The extraction phase involves the chemical soaking and wet sieving of soils followed by the collection of macrocharcoal (≥500 μm). The analysis phase is performed semi-automatically using the open-source software ImageJ to count and measure the area, length, and width of fragments from light stereo microscope images by means of threshold segmentation. The protocol yields clean charcoal fragments, a set of charcoal images, and datasets containing total charcoal mass, number of fragments, and morphological measurements (area, length, and width) for each sample. We tested and validated the protocol on 339 soil samples from tropical savannas and forests in eastern lowland Bolivia. We hope that this protocol will be a valuable resource for scientists in a variety of fields who currently study, or wish to study, macroscopic charcoal in soils as a proxy for past fires.

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.

Multidisciplinary approach to investigate human-forest relationships in southern French Alps: How to estimate the impact of populations on the local mountain wood stock?

This study presents a multidisciplinary approach between palaeoecology and the analysis of historical archives to reconstruct forest history subjected to long-term human activities. We focus on a case study from the southern French Alps (the Bléone Valley), for which a rich historical corpus but little palaeoenvironmental data are available. We compared and contrasted (i) pedoanthracological data obtained along an altitudinal transect (ca 400 m), (ii) dendrochronological data from historical buildings and old living trees, and (iii) historical data from written sources on forest management and land-use change. The aim of this paper is to demonstrate that the comparison between different proxy data to understand the history of mountain forest ecosystems and human-forest interactions is very challenging. We show that the spatial distribution of forest and treeline position have been impacted by human activities, mainly due to agro-sylvo-pastoral practices through the use of fire and forest cutting to maintain open pasture lands and local building purposes. Despite centuries of local agro-sylvo-pastoral activities, the forest composition has remained relatively unchanged since the Middle Ages. Our comparison of historical documents with dendrochronological data on local buildings and soil charcoal data shows that the local demands of wood cannot explain the observed large-scale changes in forest spatial continuity. Curiously, the highest demand for wood by local residents did not occur in pace with modern demographic boom (17th century), as would be expected. Thus, we suggest that supra-regional external regulations and State's control played a more important role in forest management. Royal shipbuilding industry, more lucrative economic stakes, and expanded demand for timber for construction of buildings in urban areas of the lower valleys and plains are among the external factors which impacted forest exploitation during periods when logging was prohibited.

Charcoal and biological activity in formiguer soils of Catalonia (Spain): Application of a micromorphological approach

The "formiguers" (earth mounds to burn woody plant residues) constituted a common practice of fertilization of soils in many regions of Spain in the past. The result of combustion is the formation of char, charcoal, soot, graphitic carbon and black carbon, which increased soil fertility. We applied a micromorphological approach to study the relationship between charcoal and features due to biological activity on some soils of Catalonia where “formiguers” were traditionally applied. Five sites with different land uses were selected in the north and south of Catalonia, and soil thin sections were obtained from undisturbed samples. The micromorphological characterization and the quantification of the total porosity, biopores, charcoal and biospheroids due to earthworms were determined. Samples from horticultural fields showed higher total porosity (15%) than those from other fields (9%). A similar pattern appeared in relation to charcoal abundance, 1.3% in horticultural plots compared to near null presence in other plots. The biopore percentage was approximately twice (11.2%) in the north sites with respect to the south sites, and biospheroids were absent in the latter while their mean abundance was 1% in the former. Our results suggest that the presence of charcoal fragments have significantly influenced bioporosity in the studied soils. The micromorphological techniques proved useful to study of the distribution and abundance of charcoal and biospheroids in formiguer soils in Catalonia.

More Than Half of Emitted Black Carbon Is Missing in Marine Sediments

Marine sediments are the ultimate reservoir for black carbon (BC) preservation, and BC burial in sediment/soils is an efficient method for carbon sequestration to mitigate CO2 emissions. A portion of soil charcoal and atmospheric BC is dissolved in inland and oceanic water, but the amount of BC in the ocean remains unclear. We analyzed multi-sediment cores from the northwestern Pacific Ocean and lakes in China and reconstructed the timeline of BC deposition from 1860 to ~2012. The lacustrine sediment cores showed an increase in BC deposition by a factor of 4–7 during the industrialization period in China compared to the years 1860–1950 (reference level). Such increasing trends in BC have also been reproduced by ten global climate model simulations. However, the marine sediment cores did not retain these significant increases in BC deposition. Meanwhile, the model simulations predicted increased trends compared to the observed flat trends of BC deposition in marine sediments. The discrepancy suggests a large amount of BC, i.e., 65 (±11)%, is missing in marine sediment sinks. Thus, since more than half of emitted BC has dissolved into oceanic water, the dissolved BC and carbon cycle should be reconsidered in the global carbon budget.

Smoldering charcoal detection in forest soil by multiple CO sensors

Cleaning up residual fires is an important part of forest fire management to avoid the loss of forest resources caused by the recurrence of a residual fire. Existing residual fire detection equipment is mainly infrared temperature detection and smoke identification. Due to the isolation of ground, temperature and smoke characteristics of medium and large smoldering charcoal in some forest soils are not obvious, making it difficult to identify by detection equipment. CO gas is an important detection index for indoor smoldering fire detection, and an important identification feature of hidden smoldering ground fires. However, there is no research on locating smoldering fires through CO detection. We studied the diffusion law of CO gas directly above covered smoldering charcoal as a criterion to design a detection device equipped with multiple CO sensors. According to the motion decomposition search algorithm, the detection device realizes the function of automatically searching for smoldering charcoal. Experimental data shows that the average CO concentration over the covered smoldering charcoal decreases exponentially with increasing height. The size of the search step is related to the reliability of the search algorithm. The detection success corresponding to the small step length is high but the search time is lengthy which can lead to search failure. The introduction of step and rotation factors in search algorithm improves the search efficiency. This study reveals that the average ground CO concentration directly above smoldering charcoal in forests changes with height. Based on this law, a CO gas sensor detection device for hidden smoldering fires has been designed, which enriches the technique of residual fire detection.

Pedoanthracology sheds light the ancientness of the pastoral highlands of three mediterranean mountain: Sierra de Gredos (Spain), southeast Massif Central (France), and northern Apennines (Italy)

The Mediterranean mountain zone is probably one of the parts of the world with the longest documented history of interactions between vegetation, climate, and human activities. The twofold objective of the present study was to examine and compare changes in three silvopastoral mountain areas, and to identify the natural and human processes that have shaped today's mountain landscapes. Although there were differences in vegetation and history between the three areas, there were also similarities in agropastoral practices, including livestock pressure and the use of fire. These similarities were supported by strong evidence based on soil charcoal and complemented by multiple other proxies (i.e., pollen analysis, archeology, historical documentation, and climatic data). The processes that led to the current physiognomy of the landscapes took place over the previous millennium, with a degree of synchrony over the past 500–800 years. The long co-evolution of humanity and landscape led us to reflect on the legacy of previous human practices and climatic changes, in terms of the composition of modern forests and the sensitivity of certain arboreal taxa (Pinus gr. sylvestris, Abies alba and Taxus baccata) that declined or disappeared during the late Holocene when the rates of vegetation change accelerated markedly. In summary, the comparative study of the history of the three highland landscapes attests to the interaction between long-term human impact (mainly pastoral societies, including livestock pressure and use of fire) and protracted climatic episodes that led to common changes in the study areas.

Addition Pinus massoniana fallen wood improved the growth of Plagiomnium acutum in a substrate cultivation

Soilless culture has been widely used in horticultural plant production, but little research has been done on bryophyte. In this study, we selected a cultivation substrate mixed and proportioned with garden soil, granular soil, grass charcoal soil, general-purpose nutrient soil, and decomposed grade II, III, and IV fallen wood of Pinus massoniana as the raw materials of soilless substrate to investigate its effects on the growth and physiology of Plagiomnium acutum. The results showed that the total porosity, water-holding porosity, and water-holding capacity of the mixed substrate containing fallen wood of P. massoniana were significantly higher than those of other cultivated substrates. The average cover of the P. acutum was significantly and positively correlated with the substrate’s total porosity and water-holding porosity. Chlorophyll content was highly significantly and positively correlated with the water holding capacity and total nitrogen content of the substrate. Among them, VIII decomposition grade Pinus massoniana fallen log:Vgrass charcoal soil = 1:1 (SW8) substrate had the highest overall evaluation index and the best overall growth condition of P. acutum. In summary, VIII decomposition grade Pinus massoniana fallen log:Vgrass charcoal soil = 1:1 (SW8) substrate can be the best substrate for cultivation of P. acutum. The addition of P. massoniana fallen wood to the soil substrate increased the total porosity, water-holding porosity, and water-holding capacity of the substrate, which was conducive to the growth of P. acutum and the increase of chlorophyll content.

Identification of thermal signature and quantification of charcoal in soil using differential scanning calorimetry and benzene polycarboxylic acid (BPCA) markers

Abstract. Black carbon (BC) plays an important role in terrestrial carbon storage and can sustainably improve soil fertility. However, the accurate quantification of BC remains critical to fully unravelling the functions and dynamics of BC in soil. In this study, we explored the potential of differential scanning calorimetry (DSC) to identify, characterize and quantify charcoal in the soil of pre-industrial charcoal kiln sites from various forest and cropland areas in Belgium and Germany. Pre-industrial charcoals and uncharred soil organic matter (SOM) demonstrated a distinct thermal signature that could be used to distinguish between them, with charcoal being more thermally stable than SOM. The DSC pattern of charcoals was characterized by one to three specific exothermic peaks, varying in size and position depending on soil conditions. Our data suggest that the thermal moieties within charcoal depend on the strength of chemical bonds of C atoms (increasing with the degree of aromatic condensation and decreasing with weathering) and on the activation energy required to initiate combustion. Despite the specific thermal features of charcoal, its decomposition spans a wide range of temperatures that overlaps with the thermal signature of uncharred SOM. This stresses the challenge of BC quantification in soil and hinders the use of cut-off temperatures to accurately quantify charcoal in soil. Therefore, charcoal-C content was estimated from the relative height of exothermic peaks, attributed either to the combustion of charcoal or SOM. For a selection of 45 soil samples, charcoal-C content estimated by DSC was compared to benzene polycarboxylic acid (BPCA) abundance, a widely used method to quantify BC in soil. The two methods correlated strongly (R2=0.97), with BPCA C representing about one-fifth of DSC-derived charcoal C. This reinforces the view that operationally defined BC content has an absolute quantitative value only if the recovery rate is controlled, which is very complicated for many case studies. Overall, our results demonstrate that dynamic thermal analysis is largely under-exploited despite providing quantitatively interpretable information across the continuum of SOM.

Insight into the carbonaceous fraction of three cultural layers of different age from the area of Verona (NE Italy)

Cultural layers are deposits resulting from settlement and human activity on natural soil in the past. Materials from past domestic activities that become buried into the soil can be used to reconstruct human impact in a specific area in the past. For instance, humans have used fire for millennia, and charcoal in soils and sediments is applied as evidence of anthropic activity. In this context, assessing the abundance and degradation level of charcoal fragments can clarify anthropic activities in cultural deposits. In European towns, cultural layers with similar characteristics, have been defined as urban “Dark Earth” (UDE) but their age, formation and composition often differ significantly across sites.This study examined three archaeological sites in Verona, Italy, where UDE layers with similar characteristics have been identified. The primary aim of this research is to understand the anthropogenic influence on the development of UDE layers, by characterizing their geochemistry and the carbonaceous materials. To pursue this goal, we provide a micromorphological description of the sites, evaluate UDE features and the abundance of charred material andcharacterize the amorphous/crystalline degreethrough µ-Raman spectroscopy. Bulk material was described in terms of amounts of total organic carbon (TOC), recalcitrant organic carbon (ROC), total inorganic carbon (TIC), and trace element concentration. Radiocarbon dating of charred and humin fractions was performed to clarify the dynamics underlying UDE origin. We investigate the relationship between the different variables analyzed in the UDE layers at each site. Results show that a diverse array of human activities including metal tool and/or ceramic manufacturing were related to the formation of UDE layers. The investigation of carbonaceous fractions highlight differences in soil organic carbon and charred material, both of which are correlated with human influence.

Forest Fire History in Amazonia Inferred From Intensive Soil Charcoal Sampling and Radiocarbon Dating

Fire has a historical role in tropical forests related to past climate and ancient land use spanning the Holocene; however, it is unclear from charcoal records how fire varied at different spatiotemporal scales and what sampling strategies are required to determine fire history and their effects. We evaluated fire variation in structurally intact, terra-firme Amazon forests, by intensive soil charcoal sampling from three replicate soil pits in sites in Guyana and northern and southern Peru. We used radiocarbon (14C) measurement to assess (1) locally, how the timing of fires represented in our sample varied across the surface of forest plots and with soil depth, (2) basin-wide, how the age of fires varies across climate and environmental gradients, and (3) how many samples are appropriate when applying the 14C approach to assess the date of last fire. Considering all 14C dates (n = 33), the most recent fires occurred at a similar time at each of the three sites (median ages: 728–851 cal years BP), indicating that in terms of fire disturbance at least, these forests could be considered old-growth. The number of unique fire events ranged from 1 to 4 per pit and from 4 to 6 per site. Based upon our sampling strategy, the N-Peru site—with the highest annual precipitation—had the most fire events. Median fire return intervals varied from 455 to 2,950 cal years BP among sites. Based on available dates, at least three samples (1 from the top of each of 3 pits) are required for the sampling to have a reasonable likelihood of capturing the most recent fire for forests with no history of a recent fire. The maximum fire return interval for two sites was shorter than the time since the last fire, suggesting that over the past ∼800 years these forests have undergone a longer fire-free period than the past 2,000–3,500 years. Our analysis from terra-firme forest soils helps to improve understanding of changes in fire regime, information necessary to evaluate post-fire legacies on modern vegetation and soil and to calibrate models to predict forest response to fire under climate change.

Potentially Toxic Substances and Associated Risks in Soils Affected by Wildfires: A Review.

The presence of toxic substances is one of the major causes of degradation of soil quality. Wildfires, besides affecting various chemical, physical, and biological soil properties, produce a mixture of potentially toxic substances which can reach the soil and water bodies and cause harm to these media. This review intends to summarise the current knowledge on the generation by wildfires of potentially toxic substances, their effects on soil organisms, and other associated risks, addressing the effects of fire on metal mobilisation, the pyrolytic production of potentially toxic compounds, and the detoxifying effect of charcoal. Numerous studies ascertained inhibitory effects of ash on seed germination and seedling growth as well as its toxicity to soil and aquatic organisms. Abundant publications addressed the mobilisation of heavy metals and trace elements by fire, including analyses of total concentrations, speciation, availability, and risk of exportation to water bodies. Many publications studied the presence of polycyclic aromatic hydrocarbons (PAH) and other organic pollutants in soils after fire, their composition, decline over time, the risk of contamination of surface and ground waters, and their toxicity to plants, soil, and water organisms. Finally, the review addresses the possible detoxifying role of charcoal in soils affected by fire.

Once upon a time biomass burning in the western Alps: Nesting effects of climate and local drivers on long-term subalpine fires

The present article questions the relative importance of local- and large-scale processes on the long-term dynamics of fire in the subalpine belt in the western Alps. The study is based on soil charcoal dating and identification, several study sites in contrasting environmental conditions, and sampling of soil charcoal along the elevation gradient of each site. Based on local differences in biomass combustion, we hypothesize that local-scale or landscape-scale processes have driven the fire history, while combustion homogeneity supports the hypothesis of the importance of large-scale or macro-ecological processes, especially climate. Biomass burning during the Holocene resulted from the nesting effects of climate, land use, and altitude, but was little influenced by slope exposure (north versus south), soil (dryness, pH, depth), and vegetation. The mid-Holocene (6500–2700 cal BP) was an important period for climate-driven biomass burning in the subalpine ecosystems of the western Alps, while fires over the last 2500 years appear much more episodic, prompting us to speculate that human activity has played a vital role in their occurrence. Our working hypothesis that the strength of local drivers should offset the effects of regional climate is not validated. The homogeneity of the fire regime between sites thus underscores that climate was the main driver during the Holocene of the western Alps. Long-term subalpine fires are controlled by climate at the millennial scale. Local conditions matter for little in determining variability at the century scale. The mid-Holocene was a chief period for climatic biomass burning in the subalpine zone, while fires during the late Holocene appear much more episodic, suggesting that social drivers has exercised key function on their control.

Inferring the ancientness of the Mirambel woodland from soil charcoal: A local exception to the regional pattern of the Millevaches plateau (Limousin, Massif Central, France)

The Mirambel woodland on the margins of the Millevaches plateau (Massif Central) is one of the few ancient broad-leaved woodlands in France. Historical sources show that it has occupied the same surface area for the past 250 years, despite being in a region that underwent considerable anthropogenic changes during this period. We explored the Mirambel's Holocene history and ancientness by means of soil charcoal analysis, chosen because of its high accuracy on a local scale. We excavated five pedoanthracological pits in the woodland and its open marginal spaces. The 29 radiocarbon dates ranged from the Atlantic (8700–5500 cal yr BP) – Subboreal transition to the Subboreal (5500–2800 cal yr BP) and Subatlantic (2800–0 cal yr BP, i.e. AD 1950) periods, revealing the existence of fire events corresponding to six contemporaneous cultural periods: Neolithic (ca. 3877–2991 cal yr BC), Neolithic-Chalcolithic transition (ca. 2528–2525 cal yr BC), Protohistory (ca. 147 cal yr BC), Roman period (AD 326–579), Middle Ages (AD 732–1187), and contemporary times (AD 1781 to present day). Three Tilia charcoal fragments dating from ca. 3717–2919 cal yr BC indicated the presence of a diversified Mid-Holocene deciduous woodland featuring Tilia and Acer nowadays-absent taxa in this area. Deciduous Quercus and Fagus sylvatica dominated most of the soil profiles, as they do nowadays in the woodlands. Other taxa (Salix, Corylus avellana, Betula) were identified, as well as in the current vegetation. The occurrence of Cytisus-type (Fabaceae) and Calluna vulgaris suggested that there were forest clearing phases at all the points sampled. Widely varying levels of abundances may reflect differences in the duration of these open phases.

The Mediterranean Old-Growth Forests: Anomalies or Relicts? The Contribution of Soil Charcoal Analysis

Old-growth forests are of high interest for biodiversity conservation, especially in the disturbance-prone Mediterranean landscapes. However, it remains unclear whether the survival of patches of old-growth forest in the degraded Mediterranean landscapes results from local anomalies or from past, larger forests. Therefore, in this study, we assessed (1) the origin, (2) the long-term ecological trajectory, and (3) the mechanism(s) that explain the survival of a Mediterranean old-growth forest, the Sainte-Baume forest. To achieve this, we used soil charcoal analysis. We opened fifteen soil profiles in the forest and five in its surrounding areas for soil description and sampling. The soil descriptions enabled us to highlight in situ soil horizon and colluvial layers. A total of 1656 charcoal pieces from different soil samples were taxonomically identified to characterize the composition of past forests. Selected charcoal pieces (n = 34) were dated to obtain chronological data. Our investigations indicate that the survival of the Mediterranean old-growth forest, in the context of the semi-open/open Mediterranean landscapes, is the result of a combination of biotic and abiotic factors, which reduced the influence of past forest disturbances. Thus, the resistance and resilience of the forest areas are preserved over a long-term ecological trajectory. Therefore, the potential of Mediterranean old-growth forests as baseline reference points for the conservation of biodiversity is related to the identification and maintenance of the local biotic and abiotic factors which allowed the survival of the old-growth forest.

Integrated Instillation Technology for the Synthesis of a pH-Responsive Sodium Alginate/Biomass Charcoal Soil Conditioner for Controlled Release of Humic Acid and Soil Remediation.

In this work, pH-responsive gel spheres for controlled release of humic acid (CSGCHs) were prepared by an integrated instillation technology using a composite material of sodium alginate (SA) and charcoal activated carbon (CAC) as a carrier, and their slow-release performance, pH-responsive performance, and soil amendment performance were investigated. The results showed that the prepared CSGCH was uniform in size with obvious base responsiveness. Soil remediation experiments revealed that CSGCH could play a good role in the remediation of different types of soils. After 50 days of remediation, the content of nutrients and organic matter in the soil increased significantly and the pH and salt content of saline soils decreased by 15.2 and 29.8%, respectively. The plant experiment showed that CSGCH could effectively promote the growth of crops. Therefore, the prepared soil conditioner has a great potential value for improving soil conditions and promoting crop growth in agricultural applications.

Soil Nitrogen Sorption Using Charcoal and Wood Ash

This paper reviews the use of charcoal and wood ash in acid soils as adsorbents to improve N availability at the same time improving their soil fertility and crop productivity. Soil acidification poses a major challenge in agricultural sustainability and it is serious in highly weathered soils such as Ultisols and Oxisols which are noted for nutrient deficiency and Al and Fe ions toxicities. Understanding sorption mechanisms and isotherms is important for the improvement of soil N availability particularly inorganic N. However, understanding the sorption mechanisms in relation to charcoal and wood ash as absorbents in the literature is difficult because the soil amendments vary depending on their raw materials or sources of origin. Therefore, one of the objectives of this review is to provide recent research findings and theory development on the role of charcoal and wood ash in agriculture. Furthermore, this review focuses on how charcoal and wood ash improve N availability through physical, chemical and biological processes in mineral acidic soils. Balanced application and good understanding of the role of charcoal and wood ash as soil amendments have potential benefits to improve N availability and crop productivity.