Article

Activated carbon amendments to soil alters nitrification rates in Scots pine forests

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Abstract

The influence of charcoal on biotic processes in soils remains poorly understood. Charcoal is a natural product of wildfires that burned on a historic return interval of ∼100 years in Scots pine (Pinus sylvestris L.) forests of northern Sweden. Fire suppression and changes in forest stand management have resulted in a lack of charcoal production in these ecosystems. It is thought that charcoal may alter N mineralization and nitrification rates, however, previous studies have not been conclusive. Replicated field studies were conducted at three late-succession field sites in northern Sweden and supporting laboratory incubations were conducted using soil humus collected from these sites. We used activated carbon (AC), as a surrogate for natural-occurring fire-produced charcoal. Two rates of AC (0 and 2000 kg ha−1), and glycine (0 and 100 kg N as glycine ha−1) were applied in factorial combination to field microplots in a randomized complete block pattern. Net nitrification, N mineralization, and free phenol concentrations were measured using ionic and non-ionic resin capsules, respectively. These same treatments and also two rates of birch leaf litter (0 and 1000 kg ha−1) were applied in a laboratory incubation and soils from this incubation were extracted with KCl and analyzed for NH4+ and NO3−. Nitrification rates increased with AC amendments in laboratory incubations, but this was not supported by field studies. Ammonification rates, as measured by NH4+ accumulation on ionic resins, were increased considerably by glycine applications, but some NH4+ was apparently lost to surface sorption to the AC. Phenolic accumulation on non-ionic resin capsules was significantly reduced by AC amendments. We conclude that charcoal exhibits important characteristics that affect regulating steps in the transformation and cycling of N.

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... In addition, few studies have applied biochar to forest ecosystems and conducted field measurements except, for example, studies of Scots pine forest in Finland [10,11], subtropical Moso bamboo forest in China [12,13], and temperate broad-leaved forest in Japan [14,15]. Given that incubation experiments are widely known to yield different results from field-based evaluations, even if the soils used were collected from the same site [16,17], it is important to measure the response of ecosystems in the field. ...
... Biochar can adsorb proteins and free amino acids, which are substrates for microbial N mineralization [36]. Berglund et al. [16] reported that biochar application alone did not change the rate of mineralization, but the addition of biochar in combination with glycine increased the mineralization rate. Furthermore, a relatively long-term (250-500 days) study by Zimmerman et al. [42] led to the hypothesis that the carbon mineralization of organic matter is reduced by biochar application because the soil biota and its extracellular enzymes lose access to the organic matter captured in the pores of the biochar (termed encapsulation). ...
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Changes in soil nutrient dynamics after biochar application may affect indirect carbon sequestration through changes in plant productivity in forest ecosystems. In the present study, we examined the effects of woody biochar application on soil nitrogen (N) cycling over 8 months in a warm-temperate deciduous broad-leaved forest. Mineral soil samples were collected from the plots treated with different biochar applications (0, 5, and 10 Mg ha−1), and the soil inorganic N concentration was measured. Net mineralization and nitrification rates were determined in each plot using the resin–core method. Soil temperature and water content did not change significantly, but the pH increased significantly following biochar application. Soil inorganic N concentrations (NH4+ and NO3−) and net N transformation rates (mineralization and nitrification rates) were significantly reduced. Microbial biomass and the nitrification ratio (the ratio of nitrification rate to mineralization rate) were unchanged, indicating that the decrease in soil inorganic N concentration was due to the reduced mineralization rate. Adsorption of substrates (from organic matter) by the applied biochar is the most likely reason for the reduction in the N mineralization rate. The results indicate that biochar application does not necessarily stimulate N transformation, which will affect indirect carbon sequestration.
... The impact was more pronounced when the application of algal biochar was combined with PGPR inoculation, thereby increasing the microbial population involved in the nitrification process. Earlier, it has been found that nitrification rate was enhanced with the application of biochar and, ultimately, total nitrogen was increased in the soil (Berglund et al. 2004). Moreover, increased pH with the addition of algal biochar is also a responsible factor in the enhancement of nitrification and, ultimately, the total nitrogen contents of the soil (Berglund et al. 2004). ...
... Earlier, it has been found that nitrification rate was enhanced with the application of biochar and, ultimately, total nitrogen was increased in the soil (Berglund et al. 2004). Moreover, increased pH with the addition of algal biochar is also a responsible factor in the enhancement of nitrification and, ultimately, the total nitrogen contents of the soil (Berglund et al. 2004). The decomposition of organic matter is also a responsible factor for enhanced total nitrogen contents in the soil as soil organic matter was increased with the addition of algal biochar. ...
... Similar results have been reported by Munera-Echeverri et al. (2020) in an Acrisol in Zambia. However, biochar did improve the conditions for nitrification, as higher concentrations of NO 3 and greater rates of gross nitrification were found in BC than in CA plots (Fig. 3, Table 4), which agrees with previous research (Berglund et al. 2004;Prommer et al. 2014;Sánchez-García et al. 2014). The increase in gross nitrification and NO 3 concentration was observed at 5 to 20 cm (where most of the biochar was found, Table 3). ...
... The reason for greater gross nitrification is likely related to the effect of biochar on soil physical properties rather than its effect on soil pH or the availability of soil mineral N. Biochar may stimulate the populations of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) by increasing soil porosity and soil moisture in well-aerated soils (Nguyen et al. 2017;Prommer et al. 2014). Also, biochar may increase nitrification by adsorbing nitrifier inhibitors (Berglund et al. 2004) . ...
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Aims: To assess how biochar addition in rainfed conservation agriculture affects short-term transformation, plant uptake, retention of nitrogen (N) in soil, and nitrous oxide (N2O) fluxes in a tropical Arenosol planted to maize. Methods: A ten-day in situ¹⁵N pool dilution and N cycling experiment, using tracer amounts (0.1 g m⁻²) of ¹⁵N labeled ammonium (¹⁵NH4⁺), nitrate (¹⁵NO3⁻) or ¹⁵N-urea, was carried out seven weeks after planting of maize (Zea mays L.) under conservation agriculture in Zambia, using planting basins without (CA) and with pigeon-pea biochar (BC) addition (4 t ha⁻¹). Results: Pigeon-pea biochar increased soil NO3⁻ concentration, gross nitrification rate, ¹⁵N recovery in extractable soil NO3⁻, and soil moisture. However, effects of biochar on soil N retention and plant N uptake were not significant. Likewise, biochar did not affect N2O fluxes. Conclusions: At low dosage, pigeon pea biochar has a positive effect on gross nitrification rate but does not affect short-term N retention in soil, N2O fluxes, nor does it help increasing the uptake of N by maize.
... Wang et al. [36] reported that the reduced nitrification rate by the addition of peanut shell biochar was mainly due to phenolic compounds present in the biochar. However, some studies indicated that incorporating biochar within soil increased the nitrification rate, mainly through improving the soil physical properties [11,37]. It should be pointed out that the nitrate concentration at the 0-10 cm depth was significantly (p≤0.05) ...
... Nitrate (NO3 -) is very mobile and can be readily leached below the root zone of plants. Therefore, NH4 + loss from the soil is much lower than NO3 -, since NH4 + adsorption mainly occurs by negatively charged soil colloids [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39]. Arbuscular mycorrhizal fungi (AMF) could help plants acquire more nutrients by forming associations with plant roots to access a larger volume of soil [40] and, as a consequence, increase the shoot dry weight. ...
Article
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Maintaining the levels of nitrogen in agricultural fields to ensure crop yield performance is challenging due to the complex dynamics of nitrogen transformation in soil. Nitrogen is mainly taken up by plant roots in the form of nitrate, but it is considered as an environmental pollutant that threatens human and animal health. Therefore, it is necessary to use adsorbent compounds to retain nitrate in the soil. The effectiveness of two types of biochar produced from rice husk (Br) and populous wood (Bp) and two arbuscular mycorrhizal fungi, namely Funneliformis intraradices (Mi) and Funneliformis versiforme (Mv), on nitrate leaching in soil was evaluated. The soil columns planted with corn were filled with an artificial sandy clay loam soil fertigated with urea fertilizer under glasshouse conditions. After nine weeks of growing the plants, a pulse of nitrogen (0.48 g urea per core) was added to the columns. One week after the addition of urea, the shoots of the plants were removed, and the columns immediately flushed with 500 ml of deionized water to leach the soil nitrogen from the columns. The results showed that the shoots' dry-weight increased significantly (p≤ 0.05) in almost all the treatments with the highest in the BrMi treatment when compared to the control (C). The nitrate concentration in the leachate decreased 79% (from 23.2 mg/l in C treatment to 4.2 mg/l in Bp treatment), but the nitrate concentration in the soil solution increased up to 6.7-fold (Bp was the highest), which suggested a high N retention by the biochars used. It was concluded that the application of biochar and mycorrhizal fungi could reduce nitrogen loss through this artificial sandy clay loam soil and may have some implications in environment conservation.
... The abundant pores act as a powerful adsorbent for organic compounds such as phenolics (Keech, Carcaillet, & Nilsson, 2005), which are particularly released from the green leaves and litter of Ericaceae species (e.g., Vaccinium and Empetrum spp.), and suppress N mineralization and nitrification in the forest floor in boreal regions (Figure 3). In such systems, charcoal adsorbs and removes phenolic compounds from soil and stimulates the activity of nitrifiers (Berglund, DeLuca, & Zackrisson, 2004;DeLuca, MacKenzie, Gundale, & Holben, 2006). It should be noted that although charcoal has the potential to remain in soil for thousands of years, the function of charcoal as an adsorbent is relatively short-lived, as the pores become clogged. ...
... Charcoal has been shown to influence plant succession, and the mechanism by which charcoal influences plant growth and succession varies even within boreal forest ecosystems. The plant-soil system introduces unique pathways that create major limiting influences either from phenolics as inhibitors of microbial activity or from N and P as nutrients in boreal forests (e.g., Berglund et al., 2004;Makoto, Hirobe, et al., 2011;Wardle, Zackrisson, & Nilsson, 1998). Understanding these pathways allows us to predict the potential influence of charcoal on plant-soil systems, which is greatly context-dependent across boreal forests and should be tested with appropriate combinations of field and laboratory experiments. ...
Article
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We summarize current knowledge about the ecosystem functions of fire-produced charcoal in boreal forests with a special focus on its effects on soil carbon, nitrogen and phosphorous dynamics as well as on plant succession. Charcoal is a carbon-enriched material with a highly aromatic and porous structure. Charcoal is highly resistant to microbial decomposition and thus remains in soil for thousands of years, providing recalcitrant carbon to boreal forest soils. The abundant pores in and on charcoal surfaces have powerful adsorption abilities that can influence biogeochemical cycles and plant succession after fire. Our review details the influence of charcoal on plant and soil systems and explains the complex direct and indirect pathways of these influences that occur during succession after fires in boreal ecosystems. Among these pathways, the most important pathway through which charcoal influences plant and soil systems relates to the element composition and nutrient availability in soils and to the abundance of phenolics released from Ericaceae plants in the understory of boreal forests. We found a strong bias in the studied processes towards nutrient mineralization rather than immobilization, which suggests that it is risky to draw general conclusions about the influence of charcoal on soil nutrient dynamics. Last, the latest studies shed light on the enhancement of litter and humus decomposition by charcoal, given the possibility that charcoal accelerates CO2 release in a postfire forest. This review suggests comparative studies that are necessary to test the context-dependency of charcoal functions across a variety of boreal forest ecosystems. © 2020 The Authors. Ecological Research published by John Wiley & Sons Australia, Ltd on behalf of The Ecological Society of Japan.
... It is also possible that the addition of biochar increases soil pH, which leads to the volatilization of NH 3 [110]. In addition, studies have shown that biochar can inhibit nitrification by adsorbing large amounts of chemicals such as phenol and terpenes, thereby reducing the concentration of alkaline nitrogen in soil [111]. Of course, this change is closely related to the properties of the soil, and the impact varies greatly among different types of soil. ...
Article
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With the rapid development of industry and agriculture, soil heavy metal contamination has become an important environmental issue faced today and has gradually attracted widespread attention. Finding a cheap, widely available, and biodegradable material that can promote crop growth and stabilize heavy metals has become a research focus. Crop straw biochar, due to its high specific surface area, rich surface functional groups, and high cation exchange capacity (CEC), has shown good effects on the remediation of inorganic and organic pollutants in the environment. This article reviews recent research on the use of crop straw biochar for soil heavy metal contamination remediation, providing a detailed analysis from the preparation, characteristics, modification of crop straw biochar, mechanisms for reducing the toxicity of heavy metals in soil, and its application and risks in remediating heavy metal-contaminated soils. It also comprehensively discusses the potential application of crop straw biochar in the remediation of heavy metal-contaminated soils. The results show that crop straw biochar can be used as a new type of immobilizing material for the remediation of heavy metal-contaminated soils, but there are issues with the remediation technology that needs to be optimized and innovated, which poses challenges to the widespread application of crop straw biochar. In the future, efforts should be strengthened to optimize and innovate the application technology of crop straw biochar, conduct research on the remediation effects of cheap modified crop straw biochar and the co-application of crop straw biochar with other immobilizing materials on heavy metal-contaminated soils, and carry out long-term monitoring of the effects of crop straw biochar in soil heavy metal remediation in order to achieve the goal of ensuring food safety and the rational use of solid waste.
... At the beginning of the soil leaching experiment, many NO 3 − -N ions were carried away by the deionized water, which caused a lot of NN leaching losses. However, the NO 3 − -N leaching losses were significantly affected by time [50], and a decreasing trend was observed in the 15 groups as the biochar adsorbed these ions [51] and nitrification was limited [52]. NO 3 − -N adsorption was possible through the following mechanisms: (1) direct adsorption; (2) unconventional H-bonding between NO 3 − and the biochar surface [36]; ...
Article
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Rainfall runoff can lead to a reduced soil quality and non-point source pollution through the removal of nutrients from the topsoil that are not utilized by plants. The use of biochar is an effective method to solve this problem. The aim of this study was to determine the optimal concentration of added biochar to reduce the soil particle, NH4+ -N (AN), NO3− -N (NN), and total phosphorus (TP) losses. Additionally, the inhibitory mechanisms of biochar that mitigate nutrient loss were revealed using FT-IR (Fourier-transform infrared) spectrometry and SEM (scanning electron microscopy). Compared with the control group, the addition of 2% biochar resulted in decreases in the AN, NN, TP, and soil erosion rates of 57.08%, 4.25%, 30.37%, and 22.78%, respectively; the leaching loss rates of AN and NN were reduced by 6.4% and 9.87%, respectively. However, it should be noted that the use of biochar resulted in an increase in the loss of soil particles smaller than 20 μm, while it resulted in a decrease in the loss of soil particles larger than 20 μm. Adsorption processes on the benzene ring may have caused the absorption peak at approximately 1600 cm−1 to disappear after adsorption. The porous structure of biochar and the presence of hydrophilic groups (such as hydroxyl groups) facilitate adsorption reactions. The optimal concentration of added biochar was 2%.
... There are few publications of biochar effects on P transformations. The transformation of nutrients is dependent both on biotic and abiotic factors (Berglund et al., 2004;DeLuca et al., 2006). In biochar, P is present in its ash fraction (DeLuca et al., 2009;Joseph et al., 2010). ...
Article
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Biochar is a carbon rich charred organic waste resulted from pyrolysis under limited or oxygen free conditions. Biochar materials are generally characterized by higher surface area and charge density, thus have sufficient nutrients and water retention onto these charred products. Biochar may influence the soil structural stability, porosity, hydraulic conductivity, soil aeration and cation exchange capacity (CEC), resulting in improved soil fertility and productivity. In addition, biochar can also offer a favorable niche for soil microbes, resulting in elevated pattern of growth and proliferation. Phosphorus (P) is considered the most frequently deficient essential element in plant nutrition and sustainable P management is necessary for maintaining the long term soil fertility and crop productivity. Biochar may also help to improve P availability in soil by providing habitat and carbon supply to phosphate solubilizing bacteria (PSB) which can solubilize P compounds of low solubility. Integrated application of biochar and PSB can therefore, be exploited as ecofriendly strategy for the enhancement of PSB activity in soil to mobilize higher P for increased plant productivity. Present review deals with production technology and properties of biochar as well as its impact on soil health and plant growth, focusing on P solubilization and phytoavailability.
... For example, charcoal can improve soil water-holding capacity and reduce N leaching due to its highly porous structure (Lehmann et al., 2003;Villagra-Mendoza and Horn, 2018). Additionally, charcoal can also enhance metabolism and growth of soil microorganisms (Berglund et al., 2004). found that MBN content in post-fire soils increased with charcoal application in a subtropical pine plantation in south China. ...
... Additionally, differences in biochar characteristics and initial soil properties could significantly affect crop growth, carbon decomposition, and nitrogen transformation by regulating the degradation and biochemical cycling of biochar. For instance, previous research has demonstrated that the sources and pyrolysis temperatures of biochar greatly influence its properties 3 , which resulted in significant differences in the effect of biochar application [27][28][29] . Therefore, a comprehensive understanding of biochar derived from different sources and pyrolysis temperatures can help improve the utilization efficiency of agricultural wastes. ...
Article
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Biochar application is widely studied to mitigate the threats of soil degradation to food security and climate change. However, there are big variations in the effects of biochar application on crops, soils, and the atmosphere during crop production. This study provides a global dataset of biochar application effects on crop yield, soil properties, and greenhouse emissions. The dataset is extracted and integrated from 367 peer-reviewed studies with 891 independent field, laboratory, and incubation experiments across 37 countries. This dataset includes 21 variables before and after biochar application (including soil properties, crop yield, greenhouse gas emissions, etc.) of 2438 items, focusing on two main biochar application types: biochar application alone and combined with fertilizers. Background information on climate conditions, initial soil properties, management practices, and characteristics of biochar sources and production is also contained in the dataset. This dataset facilitates a comprehensive understanding of the impact of biochar application, supports the utilization of agricultural wastes for biochar production, and assists researchers in refining experimental protocols for further studies.
... Third, the low soil NH 4 -N levels result from nitrification, a process that can be accelerated following biochar additions (Nguyen et al., 2017). Adsorption of nitrifier inhibitors, water retention in pores, and activation of ammonium oxidizing archaea and bacteria can result from biochar additions (Berglund et al., 2004). Overall, the SB biochar did not affect inorganic N retention in soil. ...
Article
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Sugarcane (Saccharum spp.) represents the most valuable row crop in Louisiana. High levels of biomass production and extensive tillage have degraded portions of the state's alluvial soils used to grow sugarcane. In addition to sucrose, processing the crop generates excess bagasse each year, which can represent a disposal problem for sugar factories. However, converting the bagasse to biochar at nearby pyrolysis facilities may prove to be an economical means of improving degraded soils. The objective was to determine the impacts of low rates of biochar (<3.2 mt ha⁻¹) on soil physical, chemical, and biological properties. Plant available nutrient levels were marginally impacted by biochar additions as the biochar exhibited a relatively low surface area and neutral pH. Bagasse‐derived biochar did not affect soil nitrate retention or leaching, and overall recovery was >86%. Biochar did not increase soil CO2 evolution, indicating its stability as a soil carbon amendment. However, adding biochar with mineral nitrogen decreased CO2 evolution, compared to biochar alone, indicating a negative priming effect. Soil moisture retention was minimally impacted by biochar. Cane yield, sucrose content, and sucrose yield were not statistically affected by applying biochar with or without starter fertilizer at planting. Overall, the results indicate that lower levels of bagasse‐derived biochar minimally impacted soil properties and crop yield; however, the biochar was stable in soil and may find utility as a carbon‐rich amendment should carbon credits prove to be an additional source of grower or land‐owner revenue.
... Ada juga pendapat bahwa biochar dapat mendorong pertumbuhan mikroorganisme yang menyebabkan pembusukan senyawa yang lebih labil di dalam biochar (Hamer et al. 2004). Ada beberapa penelitian yang menunjukkan bahwa aplikasi karbon aktif (Berglund et al., 2004) dan biochar dapat meningkatkan nitrifikasi. Lingkungan mikro biochar juga dapat memberikan ceruk yang menguntungkan (pori-pori struktural halus) di mana konsentrasi oksigen menurun; untuk nitrogenase untuk berfungsi secara efektif, tekanan oksigen yang rendah diperlukan dengan ion Fe dan Mo (Thies & Rillig 2009). ...
Article
Remediasi lahan pertanian di Indonesia menjadi isu yang sangat penting untuk diteliti dan dikembangkan. Penggunaan tanah dalam jangka panjang dan metode pengelolaan yang kurang tepat disinyalir menjadi penyebab utama terus turunnya kualitas tanah pada lahan pertanian dari tahun ke tahun. Biofertilizer berbasis bahan alam dapat dipreparasi melalui proses pirolisis biomassa yang kemudian dikenal luas sebagai biochar. Penggunaan biochar baik secara individual maupun bersamaan dengan jenis pupuk lain dilaporkan mampu memperbaiki kualitas tanah dan meningkatkan produktivitas lahan pertanian, dibandingkan dengan pengelolaan tanah tanpa penambahan biochar. Bab ini mengulas kondisi lahan pertanian di Indonesia dan remediasinya menggunakan biochar untuk perbaikan kualitas tanah dan peningkatan produktivitas lahan pertanian pada budidaya tanaman tertentu.
... Biochar was reported to enhance soil nitrification in Scots pine forests, and charcoal exhibits important characteristics that affect the regulatory steps in N cycling [57]. Our results showed that biochar application increased soil TN, AN, AP, AK, and SOM as compared to the control. ...
Article
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Sugarcane yield in China is low because of the shallow A-horizon soil layer, or as it is commonly called by farmers, the “plow soil layer”, as well as low soil organic matter and fertilizer utilization efficiency. Fenlong-ridging deep tillage (FT), also called vertical rotary tillage, and amendment with biochar have been shown to improve soil quality and crop yield. In this study, field trials were conducted with newly planted and ratoon sugarcane to evaluate the effectiveness of FT, together with amendment with biochar and nitrogen fertilization, to improve sugarcane yield. The treatments were conventional tillage with chemical fertilizer without biochar (CT-CF, which was the control of this experiment), FT with chemical fertilizer without biochar (FT-CF), conventional tillage with chemical fertilizer mixed with biochar (CT-CFB), and FT with chemical fertilizer mixed with biochar (FT-CFB). FT-CFB treatment presented higher soil porosity, as well as higher contents of available N, P, K, total N, and organic matter, and lower soil bulk density. Similarly, results showed that FT-CFB presented higher sugarcane root fresh and dry weights, higher germination percentage, higher tiller number, and higher yield with statistically significant differences among treatments for both newly planted and ratoon sugarcane plants. Significant interactions between biochar and FT were observed for these crop traits. The interactions of FT and amendment with biochar improved the soil’s physical and chemical properties and increased the available nutrients, resulting in improved root growth and sugarcane yield. The statistical results of the present study imply that Fenlong-ridging deep tillage combined with chemical fertilizer mixed with biochar (FT-CFB) application is a new promising farm management practice for improving the soil’s physical and chemical properties and root growth, increasing total yield in China’s sugarcane belt area.
... The biochar physicochemical properties can cause changes in the soil nutrient and C availability, and provide physical protection to microorganisms against predators and desiccation; this may alter the microbial diversity and taxonomy of the soil. •Berglund, et al., (2004) found that activated carbon amendments to soil alters nitrification rates in Scots pine forests and concluded that charcoal exhibits important characteristics that affect regulating steps in the transformation and cycling of N. •In Europe, Biochar is seen as a technology with implications in various EU policy areas, including environment protection, waste management, agricultural policy, climate change policy, development aid, research policy, industry and energy (Montanarella, et al., 2013). •In Japan, biochar research significantly intensified during the early 1980s (Kishimoto andSugiura, 1980, 1985). ...
Presentation
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Development of biochar enriche compost and its optimization and characterisation for application as soil enhancer.
... 71 According to multiple studies, biochar increased nitrification, which increased nutrient availability, by enticing microorganisms and increasing oxygen release, particularly in the root area. 72 So it is possible to use biochar to preserve a significant amount of plant nutrients in the soil and make them available for plant growth. 73 ...
Article
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Biochar has been suggested as a soil supplement to improve soil fertility. The world is covered in microplastics (MPs). A pot greenhouse experiment was carried out to examine the effects of polystyrene (PS), sugarcane bagasse biochar (SBB), and their interactions (PS × SBB) on the CO2 emission and rice yield in a rice paddy calcareous soil. The largest CO2 emissions occurred 35–40 days following rice planting, which corresponds to the tillering stages of rice growth. Higher CO2 emissions were detected after SBB treatment. Our findings showed that applying PS increased CO2 emissions in our soil samples. Our research revealed that adding SBB can boosted the negative effects of PS in the soil. The co‐application of SBB and PS increased PS's stimulation of the CO2 emissions. We infer that PS‐SBB interactions have an impact on global warming potential, microbial community activity, and CO2 emissions. Both SBB rates resulted in a significant increase in biomass and rice grain. Our research indicates that PS has a detrimental effect on rice grain output and biomass, but that the addition of SBB can slightly lessen these effects.
... For example conifer forest soil had the greatest total extractable N following high rates of biochar addition, whereas temperate arable soils exhibited reductions in extractable N with increasing rates of biochar addition. Increased net N mineralization in black carbon-treated forest soils has been attributed to declines in inhibitory phenolic compounds or due to increased sorption of available C (DeLuca et al., 2002and Berglund et al., 2004. ...
Article
Application of biochar had significantly increased the available N, P and K contents in the post harvest soil of cotton field. However, the effect was increased with corresponding increase in the rate of application of biochar. Significantly highest values were recorded in biochar @ 10 t ha-1 application. Similar trend of direct effect was also registered in the post harvest soil of maize under both the cumulative (continuous application) and residual (one time application) studies. Proving the biochar’s ability in improving the soil physical, physico-chemical and chemical properties even in the succeeding maize crop soil. The application of biochar @ 10 t ha-1 had increased the available N by 5.21 per cent, available P by 8.97 per cent and available K by 8.18 per cent over control. Thus, proving the biochar’s ability to sustain the soil fertility status over long run.
... Failure to effectively utilize this surface area and porosity can result in the leaching of soluble nutrients from the soil, as noted by Chen et al. (2010). Biochar has been shown to increase nitrification, enhancing nutrient availability by attracting microorganisms and increasing oxygen release, particularly in the root area, according to multiple studies, including Berglund et al. (2004). Rassaei (2023a, b, c, d) reported that rice height increased by 23.28% over the control when 3% SBB was used in sandy clay loam soil. ...
Article
This study investigated the effectiveness of sugarcane bagasse biochar (SBB) in reducing the toxicity of heavy metals (HMs) in Cd-contaminated calcareous clay soil and improving the growth of rice (Oryza sativa L.). A pot experiment with a rand-omized complete block design (RCBD) was used to examine the adsorption kinetics and growth improvement of rice. Three Cd levels (0.0, 30.0, and 60.0 mg kg −1 of soil from CdSO 4. 8H 2 O) and three SBB levels (0.0, 3.0, and 6.0% by weight) were considered. The study found that the biochar's surface contains functional groups that aid in the immobilization of Cd in contaminated soil. The Langmuir model best fit the Cd adsorption data of all studied soils, predicting the highest adsorption capacity with an R 2 value of 0.9902 for the adsorption of Cd onto soil-SBB 6%. Single application of SBB at a 6% level significantly increased rice grain and biomass by 45.41 and 57.82%, respectively, in soils containing 30 and 60 mgkg −1 soil Cd, compared to single soil Cd treatments. Addition of SBB at a 6% level also significantly reduced the amounts of Cd extracted using DTPA by 53.37 and 45.14%, respectively, and absorption of Cd by 67.00 and 52.14% in soils containing 30 and 60 mgkg −1 Cd. The results suggest that incorporating SBB into soil is a suitable remedial method for promoting plant growth in Cd-contaminated soils.
... Rassaei (2023c) demonstrated that adding sugarcane bagasse biochar rates resulted in a considerable increase in height, biomass, and rice (Oryza sativa L.) grain as compared to control. According to several research, biochar boosted nutrient availability by enhancing nitrification because it stimulated microorganisms and released more oxygen, especially in the root area (Berglund et al. 2004). So, using biochar, it is possible to keep a substantial portion of plant nutrients in the soil and make them available for plant growth (Blackwell et al. 2010). ...
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Today, a variety of techniques are employed to lessen the harmful impacts of soils with high levels of heavy metals. In this case, using biochar is a fairly recent technique to lessen the toxicity of heavy metals. In this study, a pot experiment with a randomized complete block design (RCBD) was carried out to examine the impact of sugarcane bagasse biochar (SBB) on adsorption kinetics and enhancing the growth of rice (Oryza sativa L.) in Cadmium (Cd)-contaminated soil. The variables included planting rice, two levels of Cd (0 and 30 mg kg-1 of soil from CdSO4.8H2O), and two levels of SBB (0 and 3% by weight). Numerous functional groups on the surface of the biochar may contribute to the immobilization of Cd in polluted soil. According to coefficients of determination (R 2), the Langmuir model provided the best fit for the Cd adsorption data of all the studied treatments. The highest plant height was noted when the control soil was treated with SBB. By utilizing 3% SBB, rice height increased by 23.28% over control. Only Cd-contaminated soils resulted in a substantial decline in plant height. By adding 3% SBB in non-contaminated soil, rice grain output and biomass were increased 19.30 and 22.95% over control, respectively. A single application of SBB at a rate of 3% significantly increased biomass and rice grain when compared to single Cd treatments by 16.99 and 20.82%, respectively. The SBB addition to Cd-contaminated soil significantly decreased the DTPA-extractable components of Cd by 40.39% as compared to uncontaminated soil. When compared to untreated soil, SBB treatment considerably reduced the Cd levels in rice plants by 31.60%. Thus, it can be concluded that adding SBB to soil is an appropriate corrective strategy to encourage plant development in soils contaminated with Cd. Understanding how different kinds of biochar interact with contaminated soil to impact Cd uptake in plants requires more research.
... However, a few studies have shown that biochar application has no effect or even a negative effect on soil nitrification [55,56]. This could be due to the release of nitrification inhibitors such as ethylene and pinene, which reduce the activity of soil AOA and AOB [54,57], and the effect varies depending on the parent materials and biochar formation processes used. In our study, the abundance of NOB varied among the biochar-applied treatments; however, differences in the abundance of NOB among treatments were not significant, indicating that AOB was more sensitive to biochar application in paddy soil compared with AOA and NOB. ...
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Biochar is an important soil amendment that can enhance the biological properties of soil, as well as nitrogen (N) uptake and utilization in N-fertilized crops. However, few studies have characterized the effects of urea and biochar application on soil biochemical traits and its effect on paddy rice. Therefore, a field trial was conducted in the early and late seasons of 2020 in a randomized complete block design with two N levels (135 and 180 kg ha−1) and four levels of biochar (0, 10, 20, and 30 t ha−1). The treatment combinations were as follows: 135 kg N ha−1 + 0 t B ha−1 (T1), 135 kg N ha−1 + 10 t B ha−1 (T2), 135 kg N ha−1 + 20 t B ha−1 (T3), 135 kg N ha−1 + 30 t B ha−1 (T4), 180 kg N ha−1 + 0 t B ha−1 (T5), 180 kg N ha−1 + 10 t B ha−1 (T6), 180 kg N ha−1 + 20 t B ha−1 (T7) and 180 kg N ha−1 + 30 t B ha−1 (T8). The results showed that soil amended with biochar had higher soil pH, soil organic carbon content, total nitrogen content, and mineral nitrogen (NH4+-N and NO3−-N) than soil that had not been amended with biochar. In both seasons, the 20 t ha−1 and 30 t ha−1 biochar treatments had the highest an average concentrations of NO3–-N (10.54 mg kg−1 and 10.25 mg kg−1, respectively). In comparison to soil that had not been treated with biochar, the average activity of the enzymes urease, polyphenol oxidase, dehydrogenase, and chitinase was, respectively, 25.28%, 14.13%, 67.76%, and 22.26% greater; however, the activity of the enzyme catalase was 15.06% lower in both seasons. Application of biochar considerably increased the abundance of ammonia-oxidizing bacteria (AOB), which was 48% greater on average in biochar-amended soil than in unamended soil. However, there were no significant variations in the abundances of ammonia-oxidizing archaea (AOA) or nitrite-oxidizing bacteria (NOB) across treatments. In comparison to soil that had not been treated with biochar, the average N content was 24.46%, 20.47%, and 19.08% higher in the stem, leaves, and panicles, respectively. In general, adding biochar at a rate of 20 to 30 t ha−1 with low-dose urea (135 kg N ha−1) is a beneficial technique for improving the nutrient balance and biological processes of soil, as well as the N uptake and grain yield of rice plants.
... This process provided sufficient N for pakchoi growth in the vigorous period as a urea retarder. On the other hand, BC as a C source can provide a suitable environment and substrate for ammonifying microorganisms and nitrifying 3 bacteria, which enhances microbial activity and correspondingly increases the inorganic N content of the soil N pool [45]. The absorbed N by BC provided an N source for pakchoi growth. ...
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The problems of high nitrogen (N) fertilizer application rate and low N utilization efficiency are common worldwide in vegetable plantations. Application of brown coal (BC, also known as lignite) can increase crop yield and fertilizer N recovery efficiency (NRE). However, the effect of BC application on the utilization and distribution of exogenous N in the soil–plant system under different fertilization strategies is unclear. The pot experiment was set up in three factors of randomized design, including 15N-labeled urea fertilizer, BC, and organic manure, and pakchoi was used as the test crop. There were five rates of 15N-labeled urea, including 0, 100, 200, 300, and 400 kg N ha−1, two rates of BC with 5 and 0 t ha−1, and the organic manure with 0 t ha−1 which constitutes ten treatments. The other four treatments were the combination of one 15N-labeled urea rate of 100 kg N ha−1, two rates of BC with 5 and 0 t ha−1, and two rates of organic manure with 100 and 0 kg N ha−1. In conclusion, the interaction of all N fertilizer rates combined with BC improved soil 15N retention efficiency by 10.14% compared without BC amendment. Between 200 and 300 kg N ha−1, the average potential loss rate of 15N decreased by 10.41%. The application of BC could reduce N loss by enhancing plant N uptake and increasing soil retention. The combined use of 200 kg N ha−1 fertilizer and 5 t ha−1 of BC would maintain a high fertilizer NRE and ensure pakchoi yield.
... While POxC values in the lower mineral horizon were somewhat higher than those in the control (Table 3), levels in the kiln OM layer remained similar to those in the control (Figure 8e). This may reflect the absorption capabilities of charcoal, whereby labile forms of soil carbon are absorbed and are subsequently used by microorganisms as a substrate for growth [69,71,72]. ...
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This study examines the soil environment of eight charcoal kiln platforms and the neighboring soil in Czech and Bohemian low-altitude forest stands. Both mixed and undisturbed soil samples were used to assess the hydrophysical soil properties, nutrient content, cation exchange capacity, enzyme activity, and soil active carbon content, while soil color, stoniness, root density, and horizon thickness were estimated in the field. Charcoal-rich horizons had high total organic carbon concentrations and total nitrogen content (about 150% and 40% higher than in the organomineral horizons of the control plot, respectively), with total carbon stocks being higher than those in neighboring forest soils. Fine root density was highest in the charcoal-rich horizons, encouraged by high soil porosity, aeration, and favorable chemical properties. Enzyme group activity differed between individual soil horizons and kiln and control plots, with depolymerization enzyme activity highest in charcoal-rich horizons and humification enzyme activity highest in mineral horizons. Phosphatase, chitinase, and phenoloxidase activity were highest in charcoal-rich horizons, while β-glucosidase activity remained similar across horizons. After long-term abandonment, kiln sites shift from inhospitable sites to localized hotspots for plant and microbial growth, having more favorable physical, enzymatic, and chemical soil properties than the surrounding areas. This study confirmed that kiln production platforms act as microhabitat hotspots, also providing information on a wide spectrum of soil properties linked with soil microorganisms and root growth.
... S2), and the high concentration of PyC in all incubation processes reduced the phenolic concentration in the soil. This means that PyC adsorbs phenolic organic matter into the pore structure and reduces the phenolic concentration in the soil (Berglund et al., 2004;Bird and Ascough, 2012;Pietikäinen et al., 2000). Moreover, under incubation conditions, high concentrations of PyC accelerated the activity of phenolic-degrading microorganisms (McGivern et al., 2021;Zak et al., 2019), so more phenolics were consumed in the soil than when PyC was added at low concentrations. ...
Article
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Wildfires play a critical role in regulating soil carbon (C) budgets in peatland ecosystems, and their frequency and intensity are increasing owing to climate change and human activities. Wildfires not only emit CO2 during the combustion process but also produce pyrogenic carbon (PyC), which accumulates in the soil C pool and influences soil C decomposition. However, the role of PyC after a fire in peatland soil C mineralization has rarely been examined. This study investigated the effects of PyC addition on peatland soil C mineralization and its potential driving mechanisms using an anaerobic/aerobic incubation experiment with peat soils collected from typical peatlands in the Great Khingan Mountains, Northeast China. The effect of PyC was more pronounced under aerobic conditions than under anaerobic conditions. The mean C- mineralization rates of soil were significantly increased by 45.2 ± 15.5 % and 87.6 ± 14.3 % with 10 % PyC250°C addition after the initial stage (D7) of aerobic and anaerobic incubation, but PyC600°C addition caused a to decrease. Compared with PyC600°C, PyC250°C addition significantly increased the available N content and altered the soil microbial activities, which may be the primary reason for the increase in C mineralization rates. Furthermore, adding a high concentration of PyC (10 %) reduced the concentration of phenolics but increased phenol oxidase activity, which promoted C mineralization rates. Thus, PyC250°C addition to peat soils mainly influences the microbial biomass C content through the accumulation of available N and phenolics, which ultimately positively affects C mineralization rates.
... Major changes in the total N were found in ND. The total nitrogen content fluctuations in biochar-treated mesocosms may have been associated with both a growing need for protein from soil bacteria, and plant growth [54,55]. Moreover, the lowest values of available P and total carbon contents were registered in ND+B. ...
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In agriculture, biochar (B) application has been suggested as a green technology to reduce nitrate pollution from agricultural origins and improve crop yield. The agronomic impact of B use on soil has been extensively studied, while knowledge of its possible effects on horticultural cultivation is still scarce. A greenhouse experiment was conducted to evaluate the effect of using biochar in soils treated with two different rates of nitrogen fertilizers on soil properties and nitrogen (N) leachate. This study also investigated the vegetative parameters during the crop growing season of Brassica oleracea L. var. botrytis. Soil mesocosms were set up to test the following treatments: untreated/control (C); normal dose of N fertilizer (130 kg N ha−1) (ND); ND+B; high dose of N fertilizer (260 kg N ha−1) (HD); and HD+B. Principal component analysis and cluster analysis were exploited to assess biochar's ability to reduce nitrate leaching and enhance soil–vegetative properties. Biochar addition affected the soil chemical properties of the fertilized microcosms (ND and HD). Biochar increased the content in HD soil and the in ND soil by 26 mg/L and 48.76 mg/L, respectively. The results showed that biochar application increased the marketable cauliflower yield. In ND+B and HD+B, the curd weight was 880.68 kg and 1097.60 kg, respectively. In addition, a small number of nitrogenous compounds in the leachate were quantified in experimental lines with the biochar. Therefore, biochar use improves the marketable yield of horticulture, mitigating the negative impacts associated with the mass use of N fertilizers in agriculture.
... S2), and the high concentration of PyC in all incubation processes reduced the phenolic concentration in the soil. This means that PyC adsorbs phenolic organic matter into the pore structure and reduces the phenolic concentration in the soil (Berglund et al., 2004;Bird and Ascough, 2012;Pietikäinen et al., 2000). Moreover, under incubation conditions, high concentrations of PyC accelerated the activity of phenolic-degrading microorganisms (McGivern et al., 2021;Zak et al., 2019), so more phenolics were consumed in the soil than when PyC was added at low concentrations. ...
... These gases are 23 and 298 times more potent than CO2 as GHGs in the atmosphere. Biochar is reported to reduce N2O emission due to inhibition of either stage of nitrification or inhibition of denitrification, or promotion of the reduction of N2O, and these impacts could occur simultaneously in a soil (Berglund et al., 2004;DeLuca et al., 2006). ...
... Berglund et al. [135] conducted laboratory and field studies to investigate the effect of soil amendment with activated carbon (used as a surrogate for soil charcoal) on nitrification in boreal forest soils. Glycine was added to the soils as an organic nitrogen source, both in laboratory and field experiments. ...
Article
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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.
... However, the C:N value of subsurface layer applied with 30 t ha − 1 biochar was lower than that of the same depth layer with 15 t ha − 1 biochar. This may be because the increased application of biochar has a more obvious influence on the adsorption and retention of inorganic nitrogen, which reduced the loss of inorganic nitrogen and increased the accumulation of soil inorganic nitrogen (Berglund et al., 2004;Li and Wei, 2016;Ahmad et al., 2021). ...
Article
Biochar can significantly enhance soil organic carbon (SOC) and crop yield, and it is therefore the preferred material for soil improvement in medium-low yield fields. In this study, a field experiment was designed to explore the impacts of biochar application on SOC content and fraction composition. Results indicated that incorporation of biochar into soil increased the SOC content by 26.9%–65.3% in the surface layer (0–10 cm) and 30.3%–63.0% in the subsurface layer (10–20 cm) of soil, while water-soluble organic carbon (WSOC) of the two layers was increased by 2.2–40.0% and 2.3–39.8%, respectively. Microbial biomass carbon decreased under conventional nitrogen treatments and increased with biochar addition under increased nitrogen application. The C:N value increased with biochar application, while the water-soluble C:N value of soil applied with 30 t ha⁻¹ biochar was lower than that of soil applied with 15 t ha⁻¹ biochar, both in the two tested soil layers. Wheat yield is evidently correlated with SOC, with the correlation coefficients of 0.919 and 0.952 in the surface and subsurface soil layers (P < 0.01), respectively. Particularly, increasing fulvic and humic acid-like compounds of WSOC promoted the bioavailability of nutrient elements, thereby increasing the crop yields. Therefore, biochar application is an effective means to fertilize middle-low yield soils through increasing SOC sequestration and nutrient reserves, or adjusting soil C:N value to a proper range, thereby reducing nutrient loss and increasing wheat yield.
... 42 Although the soil alkalinization induced by biochar application is expected to promote soil nitrification, but it was observed that soil pH changes do not solely influence its rate of nitrification. 43 However, changes in the P availability can be expected due to the increases in soil pH as it is highly pH-dependent; while insolubility of iron and aluminium phosphate dominate in acidic, insoluble Ca phosphates are predominant in alkaline soils. 13 So, modification of soil pH through biochar amendment to influence the nutrient availability of particularly P, K, and Mg is depicted in the literature. ...
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Biochar application in soil can play a substantial part in altering the soil nutrients dynamics, pollutants, and microbial ecology. Also, strategic biochar treatments in soil may promote sustainable agriculture while providing numerous agronomic, economic, and environmental benefits. Both physical characteristics of biochar including surface area, particle density, and pore size distribution, and chemical characteristics like pH, electrical conductivity, total and plant-available concentrations of carbon, nitrogen, potassium, and phosphorus, cation exchange capacity, and selected minor nutrient contents influence its agronomic potential in soil. Some of the key outputs of biochar amendment include better nutrient management in soil, improved crop growth and productivity, enhanced crop physiological parameters and quality, reduced bioavailability of contaminants in soil and overall decrease in greenhouse gas emissions from soil. Moreover, the associated benefits of carbon sequestration through its highly recalcitrant nature could aid in the mitigation of climate change. The economic benefits of improved crop yield along with reduced costs of frequent fertilizers application and reduced irrigation can help in achieving economic stability and profitability to the farmers without compromising the preservation of environmental ecosystems. However, since most of these effects of biochar are highly dependent on variable factors including soil type, crop type and agroclimatic conditions, etc., long term field investigations focussing on positive and negative implications and potential limitations are necessary to propose biochar for practical agricultural applications.
... Activated carbon is widely used in a broad range of applications including agriculture [13], environmental remediation [14], energy storage [15], catalysis [16], and electrode materials for electrochemical devices [17]. One interesting application of activated carbon is its use as a mycotoxin binder. ...
... This will lead to a relatively lower N contents in the composted biochar treatments than the combined compost and biochar treatments. Berglund et al. (2004) andDe Luca et al. (2002) explained that notwithstanding the low N content of many biochars, their application may result in net nitrification due to the labile C they release and their ability to increase soil pH. This observation is confirmed by, the greater TON observed in the combined biochar and compost treatments. ...
Article
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Soil fertility decline is a major constraint to crop production in sub-Saharan Africa. The positive effect of biochar and compost applications on soil fertility has been reported by many authors. In this study, a 30-day laboratory incubation experiment was done using 120 g samples each of a Haplic acrisol amended with corn cob biochar (cbio), rice husk biochar (rbio), coconut husk biochar (coco300 and coco700) or poultry manure compost (compost); and co- composted rice husk biochar (rcocomp) or co-composted corn cob biochar (cococomp) at rates of 1 % w/w amendment: soil, respectively. Other treatments in the study were combined poultry manure compost and corn cob biochar or rice husk biochar (1 % compost + 1% biochar: 1% soil w/w), respectively, to examine their effects on basal soil respiration, soil pH; soil microbial carbon; cation exchange capacity; total organic carbon, total nitrogen and available nitrogen concentration. Biochar and compost applied solely or together, and composted biochar increased soil pH by 0.28–2.29 pH units compared to the un-amended control. Basal respiration from the sole compost or composted rice husk, or corn cob biochar or combined biochar and compost were higher than the un-amended control, which was similar to that from the biochar only treatments. TOC in the sole compost and combined corn cob biochar and compost treatments were up to 37% and 117% higher, respectively, than the control. Combined application of rice husk biochar and compost increased MBC by 132% while sole compost addition increased MBC by 247%, respectively, compared to the control. In conclusion, the study demonstrated that sole or combined application of compost and biochar, or composted biochar improved soil quality parameters such as soil pH and MBC, and promoted soil C stabilization through enhanced TOC and reduced soil C loss through basal respiration.
... The interactions between biochar and plant roots were promoted by biochar entrance through root hairs into the water-filled macropores or bonding onto the biochar surface for nutrients [71,72]. Some studies have reported that biochar increased nutrient availability by increasing nitrification due to microorganism stimulation and greater oxygen release, particularly in the root area [73,74]. Thus, with biochar, a significant fraction of plant nutrients can be retained in the soil and made available for plant growth [20,75,76]. ...
Article
Biochar has been recommended as a soil amendment to improve soil fertility and mitigate methane (CH4) emissions from rice cultivation. Its effects, however, vary depending on soil type, biochar characteristics, and application rate. This study was aimed to evaluate the potential of mangrove biochar on CH4 mitigation, soil properties, and the productivity of rice cultivated in a clay loam soil in Thailand. Biochar was used at a rate equivalent to 10 t ha⁻¹ season⁻¹, both with (biochar + fertilizer: BF) and without (biochar alone: BI) fertilizer, for two cultivation seasons. BI reduced CH4 flux at most stages of rice growth. Relative to control soil (no biochar, no fertilizer: CT), BI significantly decreased cumulative CH4 emissions by 21.1% in the first season and 24.9% in the second season. CH4 emissions from BF soil were also less than those from the use of fertilizer alone (FE). Rice grain yield in BI was 7.85% and 14.4% greater than in CT, and in BF by 1.47% and 3.72% greater than FE, in the first and second seasons, respectively. The decrease in CH4 emissions and increase in rice grain yield decreased CH4 emission intensity under biochar treatments. Soil pH, organic carbon, cation exchange capacity, and available nutrients in the soil increased with biochar addition. The soil organic carbon stock was significantly increased by 32.6% in BI and 27.5% in BF after the first season, and by 43.5% in BI and 39.6% in BF after the second season.
... Application of BC (1) may accelerate the growth of soil microbes which reduce N 2 O emission by supporting denitrification of NO 3 to N 2 (2) facilitates the mycobacterial reduction of NO 3 to NH 4 + (3) adsorbs NH 4 + on its surface (4) decrease the abundance of microorganisms involved in nitrification of NH 4 + to nitrite (NO 2 -) (Anderson et al., 2011) (5) act as "electron shuttle" facilitating electron transfer to soil denitrifying microbes . BC adsorb NH 4 + on its surface and reduces its availability for nitrification as a result, N 2 O emission is declined (Berglund et al., 2004;Lehmann et al., 2006). Application of BC to soil increased soil N mineralization, suppressed denitrification and reduced cumulative N 2 O emission by 91 % in a sandy loam soil . ...
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... One of the pathways for loss of 15 NH 4 + -N could be the conversion of 15 NH 4 + -N to 15 NO 3 − -N through nitrification followed by 15 NO 3 − -N leaching and gaseous N losses: mostly as N 2 O during nitrification, and N 2 O and N 2 during denitrification (Huber et al. 1977). The recovery of 15 NO 3 − -N in the leachate in 15 NH 4 NO 3 treatments with their magnitudes as high as that in NH 4 15 NO 3 treatments ( Fig. 3g and h) indicates that part of the added 15 NH 4 + -N was converted to 15 NO 3 − -N (through nitrification), which is in line with the findings that biochar can stimulate the nitrification process (Berglund et al. 2004;Dannenmann et al. 2018). Nevertheless, we found that the application of biochars helped to reduce NO 3 − -N leaching and N 2 O emission. ...
Article
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A ¹⁵ N tracing pot experiment was conducted using two types of wood-based biochars: a regular biochar and a Kon-Tiki-produced nutrient-enriched biochar, at two application rates (1% and 5% (w/w)), in addition to a fertilizer only and a control treatment. Ryegrass was sown in pots, all of which except controls received ¹⁵ N-labelled fertilizer as either ¹⁵ NH 4 NO 3 or NH 4 ¹⁵ NO 3 . We quantified the effect of biochar application on soil N 2 O emissions, as well as the fate of fertilizer-derived ammonium (NH 4 ⁺ ) and nitrate (NO 3 ⁻ ) in terms of their leaching from the soil, uptake into plant biomass, and recovery in the soil. We found that application of biochars reduced soil mineral N leaching and N 2 O emissions. Similarly, the higher biochar application rate of 5% significantly increased aboveground ryegrass biomass yield. However, no differences in N 2 O emissions and ryegrass biomass yields were observed between regular and nutrient-enriched biochar treatments, although mineral N leaching tended to be lower in the nutrient-enriched biochar treatment than in the regular biochar treatment. The ¹⁵ N analysis revealed that biochar application increased the plant uptake of added nitrate, but reduced the plant uptake of added ammonium compared to the fertilizer only treatment. Thus, the uptake of total N derived from added NH 4 NO 3 fertilizer was not affected by the biochar addition, and cannot explain the increase in plant biomass in biochar treatments. Instead, the increased plant biomass at the higher biochar application rate was attributed to the enhanced uptake of N derived from soil. This suggests that the interactions between biochar and native soil organic N may be important determinants of the availability of soil N to plant growth.
... The biochar could act as a nutrient source of labile carbon though with its small contribution (Prendergast-Miller et al. 2014). The porous structure and NH 4 + retention capacity of biochar stimulate the nitrification in soil (Berglund et al. 2004). Furthermore, the presence of fertilizer may benefit the root development, and accelerate the activities of rhizospheric microorganism, which may further enhance the nitrification effect and provide more nitrate. ...
Article
Biochar can enhance crop production and sequester carbon, but there have been few studies with tree crops. Rubber plantations cover more than 8 million hectares in Southeast Asia, so we assessed the feasibility of biochar application in these plantations with a pot trial. Rubber seedlings were planted in soil with four concentrations (0, 1.25%, 2.5% and 5%, w/w) of biochar combined with two concentrations of compound fertilizer (0 kg/ha and 300 kg/ha). Soil properties and seedling growth were measured, and a leaching experiment was conducted in the rainy season. Our results show that biochar increased pH, water content (27.4–65.1%), total carbon (25.4–53.6%), nitrate nitrogen, and available phosphorus in the soil, and decreased bulk density (3.2–23.9%). Biochar treatment reduced leaching of ammonium nitrogen and ortho-P. Biochar increased seedling nutrient uptake (C, N, P and K), with 2.5% and 5% biochar showing the largest effects, but seedling biomass was the highest with 1.25%, and declined in 2.5% and 5%. Our results suggest that biochar addition is an effective way to improve rubber plantation soils, sequester more carbon and decrease nutrient leaching, but the optimum application rate under field conditions needs further research.
... The unavailability of these recalcitrant phenolic compounds by such active interventions may block the protein complexation chain, reactivate microbial enzyme activity and accelerate the conversion of organic N to inorganic forms (Gundale, Sverker, & Albrectsen, 2010;Kraus et al., 2003). Besides altering enzyme-mediated transformation of soil organic N, sorption of phenolic compounds by activated carbon and biochar may reduce the presence of factors inhibitory to nitrification in the soil environment that further allows nitrification to proceed (White, 1994) since phenolics generally have a negative effect on nitrifying bacteria (Berglund, DeLuca, & Zackrisson, 2004;White, 1994). Many studies have reported increased nitrification or abundance of ammonia-oxidising bacteria, a microbial functional group that mediates nitrification, after treatment with both activated carbon and biochar (Ball, MacKenzie, DeLuca, & Montana, 2010;DeLuca et al., 2006;Dempster, Gleeson, Solaiman, Jones, & Murphy, 2012). ...
Article
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Invasive plants are key drivers of global environmental changes leading to the disruption of ecosystems. Many invasive species engage in novel niche construction through plant–soil feedbacks that are driven by plant secondary compounds. These compounds can persist in the soil even after removing the invader, thus creating a legacy effect that inhibits the return of native flora and fauna. The formulation of active intervention strategies that can reverse niche construction is therefore critical for the restoration of these invaded ecosystems. We conducted this study in an old‐field in Massachusetts, USA, that has been invaded by Japanese knotweed (Polygonum cuspidatum) for >20 years. We chose knotweed as a model system as it alters soil chemistry and microbial community through the input of polyphenols such as tannins that creates a legacy effect. Following the removal of knotweed biomass, we investigated the effect of two soil carbon (C) amendments (biochar and activated carbon) on the growth and establishment of newly seeded native and prairie species. We measured the percent plant cover and above‐ground biomass to assess the establishment of the native and prairie species. We also measured soil and microbial characteristics including nutrient availability, extracellular enzyme activities and fungal biomass to elucidate the effect of C amendments in reversing the legacy effect. Eventhough the native species did not respond positively to C amendments, the biomass of the prairie species was 80% higher in activated carbon and biochar amended plots than the non‐amended control plots. The nitrate content of the C amended plots was five times higher than the non‐amended plots indicating an increased N mineralisation in the C amended plots. This could be potentially due to the amelioration of phenolic compounds by activated carbon and biocharthrough sorption. The phenol peroxidase activity also increased in the activated carbon and biochar amended plots potentially due to the less inhibition by phenolic compounds. With the decrease in polyphenols, the fungal biomass decreased in C amended plots that may have resulted in faster nutrient cycling and increased availability of soil N. Synthesis and applications. The phenolic compounds from the litter of invasive species that persist in soil C fractions can negatively affect the germination and growth of the native or non‐invasive plant species. The polyphenols such as tannins from the litter can complex nitrogenous compounds in soils making the N unavailable to the native or non‐invasive species. Our results revealed the potential of soil C amendments in reversing niche construction and legacy effects of polyphenol‐rich invasive species and indicated that biochar could be a more economically feasible alternative to activated carbon in restoring invaded ecosystems. These results also emphasise thatunderstanding the mechanisms through which invasive species create a legacy effect is pivotal in formulating suitable knowledge‐based practices for restoring invaded ecosystems.
... Although, biotic and abiotic factors are known to be the primary influencers of nutrient transformation, a volume of research have been focussing on the application of biochar on the nutrient cycling (Rahman et al., 2020). Studies reported that biochar affects the nitrification and ammonification process in the soil (Berglund et al., 2004;DeLuca et al., 2015). Biochar increases N-mineralization, which is positively correlated with biochar H/C ratio, so less recalcitrant biochar (high H/C ratio), easily decompose and releases N (DeLuca et al., 2015). ...
Article
Surface coal mining activities completely destroy vegetation cover, soil and biodiversity. The aftermaths include huge coal mine spoil dumps, changed topography, drainage and landscape, deteriorated aesthetics and increased pollution load. These coal mine spoils are characterised by high rock fragments, extremely low water holding capacity, compacted and high bulk density, lack of organic carbon and plant nutrients, low cation exchange capacity, acidic pH and toxic metal contamination, which poses difficulties in reclamation. An array of studies has been focused on the sustainable use of biochar for restoration of degraded agricultural soil by improving the soil physicochemical, nutritional and biological properties. Although a volume of studies has been done on biochar application, its specialised application in reclamation of coal mine spoils is still atypical, also a systematic review on the mechanism by which biochar amends the mine spoil is lacking. This review focuses on i) factors affecting the biochar properties, ii) the mechanism involved in altering the physical, chemical and biological properties by biochar, (iii) remediation of potentially toxic elements in soil and restoration of degraded land using biochar, and, iv) highlighting the important aspects to be considered while using biochar for reclamation of coal mine spoil. Biochar prepared at 450 °C from a lignocellulosic rich biomass can be an alternative for reclamation for coal mine spoil. Review also suggested suitable methodologies for bulk production, application and economics of biochar in coal mine spoil reclamation.
Article
In the short term, biochar effectively retains water and nutrients, thereby enhancing water productivity and nitrogen (N) use efficiency, consequently increasing crop yield. Over time, however, the ability of biochar to regulate water and N may diminish, leading to changes in its mechanisms for enhancing yield. Therefore, the time-dependent effects of aged biochar on yield enhancements need to be assessed. We conducted a two-year field experiment using a split-plot design with varying periods of biochar addition as the main plots, denoted as one year (Y1), two years (Y2), five years (Y5), and six years (Y6), and three addition rates as the subplots, denoted as no biochar addition (C0), 6 t·hm−2 biochar (C6), and 12 hm−2 biochar (C12). The results showed that under identical conditions, short-term biochar addition significantly outperformed medium- to long-term addition in enhancing maize yield, water productivity, N-use efficiency, and soil fertility index (SFI). There was no significant difference between the Y6C6 treatment and the control with no biochar addition, however high biochar addition may help mitigate this decline. Structural Equation Model (SEM) analysis demonstrated a positive correlation between increases in soil NH4+-N and NO3−-N content and SFI. Additionally, nitrate nitrogen (NO3−-N) content positively affected water productivity. However, with extended periods of biochar addition, the effect of NO3−-N on both SFI and water productivity weakens, whereas that of ammonium nitrogen (NH4+- N) on SFI intensifies, influencing yield. Therefore, C12 treatment not only improves yield, water productivity, and N-use efficiency but also mitigates the reduction of positive effects on crops and soil after medium- and long-term addition of biochar.
Article
The fertosphere, as the interfaces between fertilizer granular and soil particles, represents a key hotspot for nitrogen transformation processes, particularly for ammonia (NH3) and nitrous oxide (N2O) emissions. Understanding the heterogeneity of the fertosphere, especially when incorporating organic amendments like biochars, is crucial for predicting NH3 and N2O emissions after soil fertilization. In this study, we investigated the effects of three types of biochar (pristine, aged, and acid-washed biochar) on heterogeneity of fertosphere induced by localized urea application. pH-specific planar optodes were employed to visualize pH gradients in fertosphere hotspots with high spatial and temporal resolution. In addition, we conducted thorough measurements of the gradient distribution of electric conductivity (EC), mineral N, aqueous NH3 in soil and enzyme activities relevant to nitrification. Concurrently, NH3 and N2O emissions from the soil were continuously monitored at a high temporal resolution. Initially, urea-induced fertosphere exhibited significant NH3 emissions, primarily attributed to the pH elevation resulting from urea hydrolysis. However, after 6 days, NH3 emissions subsided, and there was a notable sharp increase in N2O emissions. Importantly, compared to urea application alone, the inclusion of pristine biochar led to a delay in soil pH decline with a 19% rise in NH3 emission. Aged biochar, characterized by a higher content of oxygen functional groups, demonstrated increased NH4+/NH3 adsorption capacity and enhanced ammonia monooxygenase (AMO) activity in soil, resulting in an 18% reduction in NH3 emission. While a slight decrease of 5% in NH3 cumulative emission was observed in the acid-washed biochar treatment. Notably, biochar could potentially promote nitrification-derived N2O emissions due to the accumulation of NH3 oxidation products (NH2OH). These findings could contribute to refining N transformation models for fertilized soils, and optimizing N fertilizer application strategies.
Article
With the development of the mining and metallurgy industries, heavy metal emissions are rising and increasingly polluting the soil. Heavy metals cause soil degradation, reductions in crop yield and quality, and the sustainability of land resources, and threaten regional biodiversity and human health. Accordingly, soil heavy metal pollution and remediation are attracting increasing global attention. Biochar is an excellent fixation agent that has been widely used in the remediation of heavy metal-contaminated soils. In this study, the feasibility of biochar remediation was explored by adding various doses of it to contaminated soil. Five treatments were explored: contaminated soil (controls), and contaminated soil with biochar doses of 1%, 2%, 4% and 10%. The influences of biochar on the forms and contents of soil heavy metals and microbial activity were determined. Biochar was found to passivate heavy metals, reduce the contents of acid-soluble and reducible Cd, Pb, Cu, and Zn, increase the contents of oxidizable and residual Cd, Pb, Cu, and Zn, increase soil basal respiration and microbial carbon, reduce microbial respiration entropy, reduce fluorescein diacetate (FDA) hydrolase activity, and increase the activities of dehydrogenase, catalase, and urease. Biochar clearly affected the forms and availability of heavy metals in red soil and soil microbial activity. Biochar is an ideal conditioner for the remediation of heavy metal-contaminated red soil in mining areas, for which the present study provides a theoretical basis and practical guidance.
Article
Biochar has been suggested as a soil supplement to improve soil fertility and mitigate methane (CH4) emissions from rice farming. On the other side, the world is covered in microplastics (MPs), which are tiny pieces of degraded plastic. Studies have paid little attention to the combined biochar and soil contamination caused by MPs, particularly the mechanism of their interactions with CH4 emissions. In this study, a pot greenhouse experiment with a randomized complete block design (RCBD) was carried out to examine the impact of polystyrene (PS), sugarcane bagasse biochar (SBB), and their interaction (PS*SBB) on the CH4 emission and rice yield in a rice-cultivated paddy calcareous soil. The largest CH4 emission occurred at 30 and 70 days following rice planting, which corresponds to the tillering and heading stages of rice growth. Adding SBB to our paddy soil samples reduced CH4 emissions. Our findings showed that applying PS at different rates greatly increased CH4 emissions in our soil samples under ambient conditions. Our results showed that adding SBB can partially offset the negative effects of PS in the soil. In comparison with when PS was applied alone, the co-application of SBB and PS reduced PS’s stimulation of the global warming potential (GWP) by altering its impacts on the structure and function of the soil’s microbial community and the carbon and nitrogen contents of the microbial biomass. We come to the conclusion that interactions between PS and the use of SBB have an impact on GWP, microbial community activities, and CH4 emissions. Both SBB rates resulted in a considerable increase in height, biomass, and rice grain as compared to control. Our findings indicated that PS negatively impacts rice height, grain yield, and biomass and that the addition of SBB can partially counteract PS’s negative effects on the rice. Further study is needed to understand how various types of MPs interact with soil amendments to affect ecosystem function.
Article
Biochar creates a resistant soil carbon pool that is carbon-negative, provides long-lasting improvements in soil fertility and serves as a net withdrawal of atmospheric carbon dioxide stored in highly stable soil carbon stocks. The enhanced nutrient retention, improved soil fertility and water holding capacity of biochar-amended soil not only reduces the total fertilizer requirements, but also the climate and environmental impact of croplands with generally increased production. I hypothesized that biochar increases plant growth by ameliorating negative soil physicochemical, and enhancing microbial, properties with special relation to nutrient availability and contributes actively to modify ecosystem gas exchange. Moreover, I hypothesized that the rate of biochar application influences the rate of biochar surface oxidation, nature and mineralization of functional groups, when it was added to soil for a long period of time in a controlled environment. The present study focused on determining the potential of a wood-based, high temperature (1100°C) biochar, to increase strawberry plant growth and ecosystem gas exchange in topsoil and its influence on soil quality. The results discussed in this thesis were obtained from a long-term investigation conducted under controlled conditions and is novel because of its duration (18 months), and because of the use of biochar derived from demolition wood. There is currently much interest in utilising biochar as a soil amendment for increased soil health and for carbon sequestration and European and International voluntary standards for biochar safety are under review in the UK post-Brexit. All work on biochar to date, has utilised biochar from virgin wood or agricultural residues. To the best of my knowledge, this is the first study to quantify effects of biochar derived from demolition wood on soil health. The importance of this is twofold; firstly, the stock of virgin wood for biochar production is limited, therefore it is important to be aware of any dangers of ‘diluting’ virgin wood with unapproved feedstock during production, and secondly, it is possible that biochar from such feedstocks might be acceptable for restoration programmes of already contaminated land. Biochar (0, 2.5, 5, 10 and 15% w/w) was mixed with topsoil, added to 14 L pots and maintained in a growth room at 20/16°C (16 hours day/night) and 50 % relative humidity for 18 months. Pots were either planted or left bare and soils in planted and unplanted pots were regularly sampled for microbiological and soil chemical determinations and plant growth measured. Biochar addition did not affect strawberry shoot growth or carbon or nitrogen content, but the 2.5% addition of biochar slightly increased root biomass, whilst the highest concentration (15%), reduced biomass relative to the 2.5% amendment, but not to the control. In the strawberry shoot, K, P, Zn, Cu, and As concentrations increased with biochar addition, while Pb content decreased with increasing rate of biochar compared to the control. Other than these, none of the shoot or root elements analysed exhibited clear biochar-driven trends. Neither leaf conductance nor leaf temperature were affected by biochar amendment. However, biochar amendment generally reduced ecosystem respiration (Re), net ecosystem exchange (NEE), gross ecosystem exchange (GEE) and soil enzyme activities. Biochar had no effect on microbial biomass nitrogen and carbon. CO2 and CH4 fluxes in soil were generally reduced by biochar amendment, but presence or absence of strawberry plants had no effect. However, soil water content, pH and Olsen P concentrations all increased with biochar amendment, as did soil nitrate concentrations in unplanted soils (but not as markedly in the presence of plants). Bulk density of the soil deceased in line with increasing biochar addition. Results from FTIR analysis showed that when this high temperature wood biochar was applied to soil, due to microbial and plant mediated transformation, it becomes more aromatic because of the loss of aliphatic and labile compounds and broadening of aromatic bands. The maximum number of functional groups (aliphatic, aromatic and carbohydrates) was recorded in the control soil (0 % biochar) both with and without plants. Aromatics (C-C and CH) were more prevalent than oxygen containing compounds (carboxyl and carbonyl), or aliphatic compounds and there were very few hydrocarbons. Shifts in the spectra for all wave numbers were observed in planted biochar-amended soils compared to control (0 % biochar). After 12 months, a marked decrease in spectral bands between 500 and 4000 cm−1 was noted in treatments with 2.5 %, 10 % and 15 % biochar. Overall, the use of biochar made from demolition wood ought to be avoided in agricultural settings. However, in contaminated areas, concentrations up to the lowest used in this study may be beneficial if pH changes or improvements in bulk density are desired.
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In the presented chapter, various aspects related to carbon stabilization and storage in the form of biochar (an important soil amendment) are discussed. The following questions were considered: (i) what is the current general knowledge on biochar and its physicochemical composition, (ii) how manufacturing conditions affect biochar characteristics, including their role in carbon stabilization, (iii) how biochar contributes to soil carbon balance and storage, (iv) what are the effects of biochar on water retention in soil, soil erosion, production yields and economic productivity in agriculture, (iv) what are the effects of biochar on soil microbial community and activity, and (v) how biochar affects other soil amendments and their roles in soil. The present studies assess scientific outcomes and results which conclude that soil organic matter gained by organic residues can be used to enhance soil carbon storage. Following the published scientific results, the biochar amendment appears to be a promising way for increasing the stocks of recalcitrant carbon in the soil from a long-term perspective. Future research should focus on the designing, production, and use of enriched biochar, e.g. with nutrients, minerals, or microorganisms, to improve soil physicochemical properties, supply nutrients, and prevent their leaching. The fertilizer supplies accessible nutrients available to plants, and biochar can sequester depleted elements and prevent leaching of the added ones.
Chapter
Biochar is a balanced out, natural carbon compound, made when biomass is heated to temperatures ranges between 250 and 700 °C, under low oxygen focuses. It is created from an assortment of biomass feedstock, for example, horticultural buildups, wood chips, fertiliser and metropolitan strong waste, through an assortment of warm medicines, among which moderate pyrolysis is the most broadly utilised because of its moderate working conditions and enhancement of biochar yields. Soil mineral exhaustion is a significant issue mainly due to soil disintegration and supplement draining. The expansion of biochar is an arrangement in light of the fact that biochar has been appeared to improve soil richness, to advance plant development, to expand crop yield and to reduce pollutions and so forth. These early developments have largely focused on the use of biochar as a soil amendment in agriculture, but other applications in environmental remediation. Thus, this chapter offers comprehensive and updated information related to production of biochar, its use for agriculture sustainability as well as environmental remediation.
Chapter
Global warming is an important issue of the twenty-first century. Robust attention is needed to mitigate the negative impacts of global warming and climate change on environmental health which ultimately impact humans and other animals on planet earth. Different sectors release greenhouse gases (GHGs) into the atmosphere which contribute to global warming and climate change. Agriculture, forestry, and land-use change is one of the sectors releasing a significant amount of GHGs into the atmosphere. Major GHG emitted from agricultural soils is nitrous oxide (N2O) which has 298 times more global warming potential than carbon dioxide (CO2). Different strategies have been used in agriculture to reduce the GHG emissions from soil including fertilizer management, nitrification inhibitors, diversified crop rotation, biochar (BC) application, etc. Biochar is a black material produced by thermochemical conversion of organic waste in the absence of oxygen. The BC application received enormous attention after 1998 and became the focal point of multidisciplinary research. It also impacts GHG emissions from agricultural soils, however, different factors impact the BC performance to reduce GHG emissions from soils including BC application rate, feedstock, pyrolysis temperature, pH, C:N ratio, soil texture, pH and land use, etc. Studying all these factors in a single study is laborious and expensive. However, the results from different studies are combined in the form of meta-analysis to compare the impact of different factors on BC performance to mitigate GG emissions. Here we summarized the key findings from latest meta-analysis conducted on multiple published studies on BC’s role to impact GHGs emissions. Possible mechanisms of how BC application impacts soil physicochemical properties and processes are also discussed.
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The effect of biochar on the growth of autotrophic nitrifiers in crude oil contaminated soil was investigated at different levels of crude oil contamination and with different concentrations of biochar in the laboratory. Three levels of crude oil (5 %, 10 % and 15 %) were considered at five (5) concentrations of biochar (2 %, 4 %, 6 %, 8 % and 10 %). The samples were incubated for thirty five (35) days and subsamples drawn at seven days interval to evaluate the population of culturable Ammonium Oxidising Bacteria (AOB) and culturable Nitrite Oxidising Bacteria (NOB) as well as changes in soil pH. Soil samples contaminated with 15 % crude oil exhibited the least cell count of AOB (2.07 x 10 5 cfu/g) and NOB (2.60 x 10 5 cfu/g) in the absence of biochar. Addition of 10 % biochar to the soil samples contaminated with 15 % crude oil significantly (P < 0.05) increased the growth of the organisms. Addition of biochar to the soil samples also increased the soil pH in a manner proportional to the concentrations of biochar and crude oil contamination level. When 10 % of biochar was added to soil contaminated with 15 % of crude oil, the soil pH increased from 4.37 to 6.39. However, when 10 % of biochar was added to the control (no crude oil) and 5 % crude oil contaminated soil, the pH increased from 5.69 in the control to 8.51 and 7.66 respectively. There was no significant effect (P > 0.05) on pH when 2 % of biochar was added to soil samples contaminated with 15 % of crude oil. Adding 6 % biochar to soil samples with 5 % w/w of crude oil exhibited the highest cell count of both AOB and NOB. In conclusion, crude oil contamination inhibited the growth of AOB, NOB. However, the inhibitory effects were overcome by addition of biochar in concentration dependent manner.
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The effect of biochar on the growth of autotrophic nitrifiers in crude oil contaminated soil was investigated at different levels of crude oil contamination and with different concentrations of biochar in the laboratory. Three levels of crude oil (5 %, 10 % and 15 %) were considered at five (5) concentrations of biochar (2 %, 4 %, 6 %, 8 % and 10 %). The samples were incubated for thirty five (35) days and subsamples drawn at seven days interval to evaluate the population of culturable Ammonium Oxidising Bacteria (AOB) and culturable Nitrite Oxidising Bacteria (NOB) as well as changes in soil pH. Soil samples contaminated with 15 % crude oil exhibited the least cell count of AOB (2.07 x 10 5 cfu/g) and NOB (2.60 x 10 5 cfu/g) in the absence of biochar. Addition of 10 % biochar to the soil samples contaminated with 15 % crude oil significantly (P < 0.05) increased the growth of the organisms. Addition of biochar to the soil samples also increased the soil pH in a manner proportional to the concentrations of biochar and crude oil contamination level. When 10 % of biochar was added to soil contaminated with 15 % of crude oil, the soil pH increased from 4.37 to 6.39. However, when 10 % of biochar was added to the control (no crude oil) and 5 % crude oil contaminated soil, the pH increased from 5.69 in the control to 8.51 and 7.66 respectively. There was no significant effect (P > 0.05) on pH when 2 % of biochar was added to soil samples contaminated with 15 % of crude oil. Adding 6 % biochar to soil samples with 5 % w/w of crude oil exhibited the highest cell count of both AOB and NOB. In conclusion, crude oil contamination inhibited the growth of AOB, NOB. However, the inhibitory effects were overcome by addition of biochar in concentration dependent manner.
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Soil fertility decline represents a major constraint to crop productivity in sub-Saharan Africa. Many studies have shown that addition of biochar or compost can effectively improve soil quality. Biochar produced from crop residues are often N-poor but rich in stable C while poultry manure composts, which is often rich in nutrients including N decomposes rapidly under high rainfall and temperature conditions. Combined biochar and compost application can compensate for the shortcomings of each other such that their interactive effect is likely to improve soil quality. A 30-days incubation experiment was carried out on a Haplic acrisol amended with corn cob biochar, rice husk biochar, coconut husk biochar, poultry manure compost and composted rice husk or corn cob biochar to examine the effect of compost and biochar, applied singly, in combination or as co-compost on basal soil respiration, and soil quality indicators such as soil pH; soil microbial carbon; cation exchange capacity; total organic carbon, total nitrogen and available nitrogen concentration. The results showed that addition of the different amendments increased soil pH compared with the untreated control with the combined corn cob and rice biochar and compost treatments recording the highest pH values. Basal respiration following sole compost, composted biochar and combined biochar and compost application were significantly greater than the sole biochar and the control treatments. TOC increased by 37% in the sole compost treatment to 117.3% in the combined corn cob biochar and compost treatment, respectively. MBC increased by 132.2% in the combined rice husk biochar and compost treatment and by 247% in the sole compost treatment compared to the control. The study has demonstrated the potential of compost, biochar and especially composted biochar to enhance soil quality, C stabilization and reduce soil C loss through basal respiration.
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A comprehensive and quantitative evaluation of the effects of fire on ecosystem nitrogen (N) is urgently needed for directing future fire research and management. This study used a meta-analysis method to synthesize up to 185 data sets from 87 studies published from 1955 to 1999. Six N response variables related to fire were examined: fuel N amount (FNA) and concentration (FNC), soil N amount (SNA) and concentration (SNC), and soil ammonium (NH 4) and nitrate (NO 3) pools. When all comparisons (fire treatment vs. control) were considered together, fire significantly reduced FNA (58%), increased soil NH 4 (94%) and NO 3 (152%), and had no significant influences on FNC, SNA, and SNC. The responses of N to fire varied with different independent variables, which were vegetation type, fire type, fuel type, fuel consumption amount, fuel consumption percentage, time after fire, and soil sampling depth. The response of FNA to fire was significantly influenced by vegetation type, fuel type, and fuel consumption amount and percentage. The reduction in FNA was linearly correlated with fuel consumption percentage (r 2 0.978). The response of FNC to fire was only affected by fuel type. None of the seven independent variables had any effect on SNA. The responses of SNC, NH 4 , and NO 3 depend on soil sampling depth. The responses of both NH 4 and NO 3 to fire were significantly affected by fire type and time after fire but had different temporal patterns. The soil NH 4 pool increased approximately twofold immediately after fire, then gradually declined to the prefire level after one year. The fire-induced increase in the soil NO 3 pool was small (24%) immediately after fire, reached a maximum of approximately threefold of the prefire level within 0.5-1 year after fire, and then declined. This study has identified the general patterns of the responses of ecosystem N that occur for several years after fire. A key research need relevant to fire management is to understand how the short-term responses of N to fire influence the function and structure of terrestrial ecosystems in the long term.
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THE importance of nitrate (NO-3) in the internal nitrogen cycle of undisturbed coniferous ecosystems has not been widely recognized1,2. Nitrate concentrations in soils from these forests tend to be low, and assays measuring net nitrification usually show exceedingly slow rates3,4. It may be, however, that microbial assimilation of NO-3 is substantial in these soils, and that net nitrification rates greatly underestimate gross rates5. Here we use a 15N isotope-dilution technique in intact soil cores to measure gross rates of nitrification and microbial assimilation of NO-3 in eleven undisturbed forest ecosystems of New Mexico and Oregon. We found that gross nitrification rates were surprisingly high in all of the forests examined. Net nitrification rates poorly predicted gross rates because the soil microbial communities had the capacity to assimilate almost all of the NO-3 produced. To our knowledge, this is the first report of gross nitrification and NO-3 assimilation rates in intact soil samples from a large number of contrasting forest ecosystems. Our results contradict previous assumptions that nitrification rates are low in mature coniferous forests and suggest that current models greatly underestimate the role of the microbial community in preventing NO-3 loss.
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Currently there is no effective method for capture, identification and quantification of root exudates and rhizosphere secondary metabolites in situ. The purpose of the work reported was to assess if capsules containing non‐ionic carbonaceous resins could be used to non‐destructively sample and compare rhizosphere organic compounds associated with contrasting plant communities. Polyester capsules (Unibest, Inc., Bozeman, MT) containing non‐ionic carbonaceous resins, Ambersorb 563 or XAD‐7 (Rohm and Haas, Inc.), were placed within the rhizosphere of spotted knapweed (Centaurea maculosa), and the native grass, Idaho fescue (Festuca idahoensis), as well as a bare‐soil control in both greenhouse and field studies. At the end a 14‐day period, resins were removed and extracted with sequential elution by water, 50% methanol, and 100% methanol. The eluent fractions were then analyzed for total organic carbon (TOC), total hexose sugars as anthrone reactive carbon (ARC), and total phenols. Samples were then concentrated by rotary evaporating to dryness and analyzed on HPLC equipped with a C‐18 column and tunable ultra‐violet (UV) detector or a photodiode array (PDA) detector. Ambersorb 563 resin extracts from greenhouse and field trials consistently showed 2 times more soluble C and 3–7 times more total soluble sugars in the rhizosphere of knapweed compared to Idaho fescue during the 1996 and 1997 field seasons. This difference was not observed using the XAD‐7 resins during the rather wet field season of 1998. In these studies fescue was found to release higher levels of sugars than knapweed, but not significantly different than control soils. Compounds sorbed to the resins from the knapweed rhizosphere were more effectively eluted by methanol than water and demonstrated both the presence of carbohydrate groups and UV absorption. The XAD‐7 resins allow for sorption of phenolic compounds similar to that of Ambersorb 563, but allow for far greater desorption of these compounds. Non‐ionic resins may provide an effective means of capturing rhizosphere organic compounds in situ, but the low concentrations of sorbed compounds may limit their utility.
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Ponderosa pine-bunchgrass ecosystems of the western United States were altered following Euro-American settlement as grazing and fire suppression facilitated pine invasion of grassy openings. Pine invasion changed stand structure and fire regimes, mo- tivating restoration through forest thinning and prescribed burning. To determine effects of restoration on soil nitrogen (N) transformations, we replicated (0.25-ha plots) the fol- lowing experimental restoration treatments within a ponderosa pine-bunchgrass community near Flagstaff, Arizona: (1) partial restoration—thinning to presettlement conditions, (2) complete restoration—removal of trees and forest floor to presettlement conditions, native grass litter addition, and a prescribed burn, and (3) control. Within treatments, we stratified sampling to assess effects of canopy cover on N transformations. Forest floor net N min- eralization and nitrification were similar among treatments on an areal basis, but higher in restoration treatments on a mass basis. In the mineral soil (0-15 cm), restoration treatments had 2-3 times greater annual net N mineralization and 3-5 times greater annual net nitri- fication than the control. Gross N transformation measurements indicate that elevated net N mineralization may be due to increased gross N mineralization, while elevated net ni- trification may be due to decreased microbial immobilization of nitrate. Net N transfor- mation rates beneath relict grassy openings were twice those beneath postsettlement pines. These short-term (1 yr) results suggest that ecological restoration increases N transformation rates and that prescribed burning may not be necessary to restore N cycling processes. 15 N; N mineralization; nitrification; northern Arizona; Pinus ponderosa Laws.; pon- derosa pine-bunchgrass communities; prescribed burning; restoration ecology; tree thinning.
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Although studies have addressed the influence of fire on soil biochemical processes, there have been no reports on how prescribed fire followed by wildfire influences microbial activity and nutrient cycling. Over a 21-mo period we monitored changes in soil nitrogen (N) and carbon (C) of a ponderosa pine (Pinus ponderosa P.&C. Lawson) and Douglas-fir [Pseudotsuga menziesii var. glauca (Beissn.) Franco] forest (both O horizon and 0-10 cm of mineral soil) that had been exposed either to prescribed fire (PB), wildfire (WF), prescribed fire three months prior to wildfire (PBWF), or no fire as an unburned control. Total N, potentially mineralizable N (PMN), NH4/+-N and NO3/--N concentrations in surface (0-10 cm) mineral soils were significantly increased immediately after WF. Soils exposed to prescribed fire prior to wildfire also had elevated concentrations of total N, PMN and NH4/+-N, but were significantly lower than in WF alone. Potentially mineralizable N was significantly reduced on all fire-exposed sites from 9 mo to the end of the study period. Although mineral soil NO3/--N concentrations in fire-exposed soils were similar to the unburned control 12 mo after fire, resin sorbed NO3/--N was 88 μg capsule-1 in WF soils vs. 24 μg capsule-1 in PBWF soils, and 1.3μ g capsule-1 in the unburned control. Microbial biomass in the WF mineral soils was as low as 52 μg g-1 21 mo after fire while microbial biomass in PBWF soils remained above 100 μg g-1 throughout the study. It appears that prescribed fire prior to wildfire may attenuate the effects of wildfire on soil and may have predisposed the microbial community to the effects of heating.
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THE importance of dissolved organic nitrogen in ecosystem nutrient fluxes and plant nutrition is only beginning to be appreciated1,2. Here we report that the polyphenol concentration of decomposing Pinus muricata litter controls the proportion of nitrogen released in dissolved organic forms relative to mineral forms (NH+ 4 + NO- 3). We have previously shown that concentrations of polyphen-ols in P. muricata foliage vary along an extreme soil acidity/ fertility gradient3. Apparently this feedback to soil conditions controls the dominant form in which litter nitrogen is mobilized, facilitating nitrogen recovery through pine-mycorrhizal associations, minimizing nitrogen availability to competing organisms, and attenuating nitrogen losses from leaching and denitrification. Polyphenol control of nitrogen dynamics helps explain the convergent evolution of tannin-rich plant communities on highly leached soils.
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Wildfires produce a charcoal layer, which has an adsorbing capacity resembling activated carbon. After the fire a new litter layer starts to accumulate on top of the charcoal layer, which liberates water-soluble compounds that percolate through the charcoal and the unburned humus layer. We first hypothesized that since charcoal has the capacity to adsorb organic compounds it may form a new habitat for microbes, which decompose the adsorbed compounds. Secondly, we hypothesized that the charcoal may cause depletion of decomposable organic carbon in the underlying humus and thus reduce the microbial biomass. To test our hypotheses we prepared microcosms, where we placed non-heated humus and on top one of the adsorbents: non-adsorptive pumice (Pum), charcoal from Empetrum nigrum (EmpCh), charcoal from humus (HuCh) or activated carbon (ActC). We watered them with birch leaf litter extract. The adsorbing capacity increased in the order Pum<HuCh<EmpCh<ActC, the adsorbents being capable of removing 0%, 26%, 42% and 51% of the dissolved Corg in the litter extract, respectively. After one month, all adsorbents harboured microbes, but their amount and basal respiration was largest in EmpCh and HuCh, and smallest in Pum. In addition, different kinds of microbial communities with respect to their phospholipid fatty acid and substrate utilization patterns were formed in the adsorbents. The amount of microbial biomass and number of bacteria did not differ between humus under different adsorbents, although different microbial communities developed in humus under EmpCh compared with Pum, which is obviously related to the increased pH of the humus under EmpCh, and also ActC. We suggest that charcoal from burning can support microbial communities, which are small in size but have a higher specific growth rate than those of the humus. Although the charcoal layer induces changes in the microbial community of the humus, it does not reduce the amount of humus microbes.
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Wildfire is the principal disturbance regime in northern Boreal forests, where it has important rejuvenating effects on soil properties and encourages tree seedling regeneration and growth. One possible agent of this rejuvenation is fire-produced charcoal, which adsorbs secondary metabolites such as humus phenolics produced by ericaceous vegetation in the absence of fire, which retard nutrient cycling and tree seedling growth. We investigated short-term ecological effects of charcoal on the Boreal forest plant-soil system in a glasshouse experiment by planting seedlings of Betula pendula and Pinus sylvestris in each of three humus substrates with and without charcoal, and with and without phenol-rich Vaccinium myrtillus litter. These three substrates were from: (1) a high-productivity site with herbaceous ground vegetation; (2) a site of intermediate productivity dominated by ericaceous ground vegetation; and (3) an unproductive site dominated by Cladina spp. Growth of B. pendula was stimulated by charcoal addition and retarded by litter addition in the ericaceous substrate (but not in the other two), presumably because of the high levels of phenolics present in that substrate. Growth of P. sylvestris, which was less sensitive to substrate origin than was B. pendula, was unresponsive to charcoal. Charcoal addition enhanced seedling shoot to root ratios of both tree species, but again only for the ericaceous substrate. This response is indicative of greater N uptake and greater efficiency of nutrient uptake (and presumably less binding of nutrients by phenolics) in the presence of charcoal. These effects were especially pronounced for B. pendula, which took up 6.22 times more nitrogen when charcoal was added. Charcoal had no effect on the competitive balance between B. pendula and P. sylvestris, probably due to the low intensity of competition present. Juvenile mosses and ferns growing in the pots were extremely responsive to charcoal for all sites; fern prothalli were entirely absent in the ericaceous substrate unless charcoal was also present. Charcoal stimulated active soil microbial biomass in some instances, and also exerted significant although idiosyncratic effects on decomposition of the added litter. Our results provide clear evidence that immediately after wildfire fresh charcoal can have important effects in Boreal forest ecosystems dominated by ericaceous dwarf shrubs, and this is likely to provide a major contribution to the rejuvenating effects of wildfire on forest ecosystems.
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Scots pine (Pinus sylvestris L.) forests of northern Sweden are often considered to be N limited. This limitation may have been exacerbated by the elimination of wildfire as a natural disturbance factor in these boreal forests. Phenolic inhibition of N mineralization and nitrification (due to litter and exudates of ericaceous shrubs) has been proposed as a mechanism for N limitation of these forests, but this hypothesis remains largely untested. N mineralization rates, nitrification rates, and sorption of free phenolic compounds were assessed along a fire-induced chronosequence in northern Sweden. A total of 34 forest stands varying in age since the last fire were identified and characterized. Overstorey and understorey vegetative composition and depth of humus were analysed in replicated plots at all 34 sites. Eight of the forest stands aged 3–352 years since the last fire were selected for intensive investigation in which ten replicate ionic resin capsules (used to assess net N mineralization and nitrification) and non-ionic carbonaceous resin capsules (used to assess free phenolic compounds) were installed at the interface of humus and mineral soil. A highly significant correlation was observed between site age and net sorption of inorganic N to resin capsules. Net accumulation of NH4+ and NO3– on resin capsules followed a linear decrease (R 2=0.61, P<0.01) with time perhaps as a result of increased N immobilization with successional C loading. NO3– sorption to resin capsules followed a logarithmic decrease (R 2=0.80, P<0.01) that may be related to a logarithmic increase in dwarf shrub cover and decreased soil charcoal sorption potential along this chronosequence. A replicated field study was conducted at one of the late successional field sites to assess the influence of charcoal and an added labile N source on N turnover. Three rates of charcoal (0, 100, and 1,000 g M–2) and two rates of glycine (0 and 50 g N as glycine M–2) were applied in a factorial design to microplots in a randomized complete block pattern. Net ammonification (as assessed by NH4+ sorption to resins) was readily increased by the addition of a labile N source, but this increase in NH4+ did not stimulate nitrification. Nitrification was stimulated slightly by the addition of charcoal resulting in similar levels of resin-sorbed NO3– as those found in early successional sites. Resin-sorbed polyphenol concentrations were decreased with charcoal amendments, but were actually increased with N amendments (likely due to decomposition of polyphenols). Net N mineralization appears to be limited by rapid NH4+ immobilization whereas nitrification is limited by the lack of an appropriate environment or by the presence of inhibitory compounds in late successional forests of northern Sweden.
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Soil microorganisms have numerous functional roles in forest ecosystems, including: serving as sources and sinks of key nutrients and catalysts of nutrient transformations; acting as engineers and maintainers of soil structure; and forming mutualistic relationships with roots that improve plant fitness. Although both prescribed and wildland fires are common in temperate forests of North America, few studies have addressed the long-term influence of such disturbances on the soil microflora in these ecosystems. Fire alters the soil microbial community structure in the short-term primarily through heat-induced microbial mortality. Over the long-term, fire may modify soil communities by altering plant community composition via plant-induced changes in the soil environment. In this review, we summarize and synthesize the various studies that have assessed the effects of fire on forest soil microorganisms, emphasizing the mechanisms by which fire impacts these vital ecosystem engineers. The examples used in this paper are derived primarily from studies of ponderosa pine-dominated forests of the Inland West of the USA; these forests have some of the shortest historical fire-return intervals of any forest type, and thus the evolutionary role of fire in shaping these forests is likely the strongest. We argue that the short-term effects of fire on soil microflora and the processes they catalyze are transient, and suggest that more research be devoted to linking long-term plant community responses with those of the mutually dependent soil microflora.
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Island area is frequently a major determinant of the species composition of biological communities; community structure, in turn, often has important effects on ecosystem-level properties. Fifty islands of varying area were selected in an archipelago in the northern Swedish boreal forest zone, in which larger islands burn more frequently than smaller ones through wildfire arising from lightning strike, thus inducing a significant relationship between island area and plant species composition. This relationship was found to be a major factor in determining several ecosystem-level properties of these islands, including standing biomass, plant litter decomposition, nitrogen mineralization, terrestrial carbon partitioning, humus accumulation, and plant nitrogen acquisition.
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A study was performed to gain insight into the mechanism of acid-tolerant, chemolithotrophic nitrification. Microorganisms that nitrified at pH 4 were enriched from two Dutch acid soils. Nitrate production in the enrichment cultures was indicated to be of a chemolithoautotrophic nature as it was (i) completely inhibited by acetylene at a concentration as low as 1 mumol/liter and (ii) strongly retarded under conditions of carbon dioxide limitation. Electron microscopy of the enrichment cultures showed the presence of bacteria that were morphologically similar to strains of known chemolithotrophic nitrifying genera. Many of the enriched bacteria, in particular those that were identified as ammonium oxidizers, were aggregated. Filtration experiments indicated that aggregated cells were able to nitrify at low pH, whereas single cells were not. It is hypothesized that cells inside the aggregates are protected against the toxicity of nitrous acid. Nitrification by aggregated chemolithoautotrophic bacteria may be the dominating process of nitrate formation in many acid soils as it does not appear to depend on the existence of microsites of high pH (acid-sensitive autotrophic nitrification) or on the availability of organic carbon (heterotrophic nitrification).
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Wildfire is a major disturbance factor in boreal forests where it is important in rejuvenating soil properties and encouraging tree regeneration and growth. However, the mechanisms behind these effects are poorly understood and little is known as to the ecological effects of charcoal produced by wildfire in these ecosystem. In this study we firstly quantified the mass of charcoal in a chronosequence of twelve forest sites in northern Sweden and found charcoal mass in soil to vary from 984 to 2074 kg ha-1; these levels appear to be sufficient for charcoal to have important ecological effect through its sorptive abilities. We then investigated the ability of charcoal from 32 forest stands (representing a range of ages from 1 to 350 yr since last fire) to adsorb phenolic compounds produced by the late successional dwarf shrub Empetrum hermaphroditum; phenolic compounds from this species have previously been shown to have important phytotoxic effects in boreal forests. Charcoal in soil from forests younger than 100 yr was very effective at reducing these effects while older charcoal was not, suggesting that the sorptive ability is likely to be most important in earlier-successional forests. Experimental reheating of deactivated older charcoal from soil showed that temperatures above 450°C could reactivate charcoal. A microcosm experiment also revealed that soil microbes could effectively reactivate young charcoal that had been saturated with phenolics. Finally we investigated the effects of artificially made charcoal on soil microbial properties at six sites. The microbial biomass was consistently enhanced in humus when it was placed adjacent to charcoal particles. Decomposition of plant litter was sometimes also affected by being in the proximity of charcoal but the direction of these effects was unpredictable. We conclude that charcoal might catalyse important ecological soil processes in early-successional boreal forests, effects that diminish as succession proceeds, and ultimately may have important long-term consequences for stand productivity and ecosystem function, especially in forests under strict fire control.
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The frequency of forest fires during the past 600 yr was studied on 281 sample plots within boreal forest ecosystems in a river valley in northern Sweden. Fire scars in living and dead trees were used for dating past fires. Before fire suppression started in the 19th century the coniferous forest had burned at a mean interval of 80 yr; in contrast, the mean time since the latest fire was found to be 155 yr. Fire frequency was studied in relation to physiographic and biotic features, e.g. exposition, surface relief, edaphic conditions, and vegetation type. It was found that all these factors have influenced the vegetation pattern induced by past fires, and led to a widespread vegetation mosaic. Fire maintained the diversity and long-term stability of the forest and represented a natural factor in the boreal forest ecosystem. Due to efficient fire suppression during the past two centuries, fire is no longer a rejuvenating factor in the forests. /// Исследовали частоту лесных пожаров за последние 600 лет на 281 участке бореальных лесных зкосистем речной долины в северной Швеции. Для определения сроков пожаров использованы рубцы от огня на живых и мертвых деревьях. До того, как началась борьба с пожарами, в XIX веке, хвойные леса горели со спедним интервалом в 80 лет. В отличие от зтого, со времени последнего пожара прошло в среднем 155 лет. Частота пожаров исследовалась в зависимости от ландшафтных и биотических факторов, например, от экспозиции склона, рельефа местности, характера почвы и растительности. Установлено, что все эти факторы влияли на характер растительного покрова, развивающегося после пожара и приводили его мозаичностк. Пожар поддерживал различия и долгосрочную стабильность леча и представлял естественный фактор в бореальных лесных экосистемах. В результате зффективного подавления пожаров за последние 200 лет, пожар в лесу 60 льше не является омолаживающим фактором.
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Although many plant species produce high levels of secondary metabolites, comparatively little is known about the temporal variability of the production and concentrations of these compounds, either in terms of quantitative or qualitative aspects. In the Swedish boreal forest the dwarf-shrub species Empetrum hermaphroditum produces high levels of phenolics which are important agents of allelopathy, regulators of herbivory and determinants of plant litter decomposition. We performed quantitative analyses of total phenolics and monitored the phytotoxic activity (defined as the ability of the extracts to retard germination of Populus tremula seeds) of aqueous leaf extracts from three age classes of leaves, collected from the field approximately every two weeks for every growing season from 1988 to 1995. The concentrations of the dihydrostilbene batatasin-III, an E. hermaphrodium metabolite with a documented phytotoxic effect, were determined in both extracts and entire leaves for material collected in 1988 and 1994. We also studied leaf gland variation of first-year leaves in relation to phenolic concentration and phytotoxic activity. Large differences existed between sampling times within years, with first-year shoots producing high levels of phenolics; these levels were maintained for second-year shoots but phenolic concentrations declined for third-year shoots, i.e. prior to leaf senescence. Phytotoxic activity was low immediately after leaf emergence, and was not consistently correlated to total phenolic concentrations of the leaves. However, more detailed analyses showed that much of the phytotoxic activity of E. hermaphrodium extracts is due to the production of batatasin-III, which reaches its maximum concentration not until September of the first year. We believe that batatasin-III is critical in determining the phytotoxic effects of E. hermaphrodium and that this compound may have additional benefits for E. hermaphrodium other than deterring herbivory. Leaf glands were present on newly formed leaves, and were produced continuously over the growing season. However, correlation analyses between the number of leaf glands and either the release of phenolics or phytotoxic activity did not reveal any significant relationships. There were also important differences in both leaf phenolic concentrations and phytotoxicity between years, although we were unable to relate this to inter-year macroclimatic parameters collected from the same site. We conclude that temporal variability of the production of phenolic compounds by E. hermaphrodium is considerable and is almost certainly of importance in introducing a degree of temporal variability into the biotic interactions that E. hermaphrodium participates in.
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This article explores the evidence for monoterpenes to alter rates of nutrient cycling, with particular emphasis on the nitrogen (N) cycle, from an ecosystem perspective. The general N cycle is reviewed and particular processes are noted where monoterpenes could exert control. The theoretical and conceptual basis for a proposed mode of action by which monoterpenes effect the processes of N mineralization and nitrification is presented, along with recent developments. It is hypothesized that monoterpenes retained in litter enhance the frequency of fire, which in turn changes many N-cycling processes. Experimental support for these roles is presented that includes effects at the cellular level and progresses through populations and communities (microbial and invertebrate) involved in N mineralization and immobilization processes. Since many inhibitors of ammonium oxidation also inhibit methane oxidation, monoterpenes also may alter processes within the carbon cycle. Finally, areas for future research that appear most promising are suggested.
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Quantitative measurement of phlorotannins (polyphenolics) in brown algae (Phaeophyta) by colorimetric assays can be confounded because: (1) most such assays also react to nonphlorotannin substances (interferences) and (2) the appropriate reference compound for such assays is not always clear, although phloroglucinol is typically used. We developed a new assay in which 2,4-dimethoxybenzaldehyde (DMBA) reacts specifically with 1,3-and 1,3,5-substituted phenols (e.g., phlorotannins) to form a colored product. This new assay, as well as eliminating the problem of measuring interferences, is inexpensive, rapid, and can be used with small sample volumes. We recommend it for all assays of phlorotannins from one or a set of closely related species where the structural types of phlorotannins present are likely to be similar among samples. It is also appropriate for broader surveys of phlorotannin levels across many species, but in this case a reference must be chosen with care. We also compared the DMBA assay to existing assays, including the Folin-Denis [both before and after the samples were mixed with polyvinylpolypyrrolidone (PVPP)] and the Prussian blue assays. PVPP was not 100% efficient (and often much less) at removing phlorotannins from solution, and its effectiveness varied among different phlorotannins. Thus, in contrast to previous studies, measuring phenolic levels in extracts before and after treatment with PVPP will not necessarily result in an interference-free measure of phlorotannins. Based on an analysis of reactive substances in red and green algae (which do not contain phlorotannins) in the Folin-Denis and Prussian blue assays, we estimate that the average level of interferences (nonphlorotannins) in brown algae measured in these two assays is on the order of 0.5% by dry weight.
Article
Abstraci. A comprehensive 'and quantitative evaluation of the effects of fire on eco- system nitrogen (N) is urgently needed for directing future fire research and management. This study used a meta-analysis method to synthesize up to 185 data sets from 87 studies published from 1955 to 1999. Six N response variables related to fire were examined: fuel N amount (FNA) and concentration (FNC), soil N amount (SNA) and concentration (SNC), and soil ammonium (NH4+) and nitrate (NO3-) pools. Wheq all comparisons (fire treatment vs. control) were considered together, fire significantly reduced FNA (58% ), increased soil NH4+ (94%) and NO3- (152%), and had no significant influences on FNC, SNA, and SNC. The responses of N to fire varied with different independent variables, which were vegetation type, fire type, fuel type, fuel consumption amount, fuel consumption percentage, time after fire, and soil sampling depth. The response of FNA to fire was significantly influenced by vegetation type, fuel type, and fuel consumption amount and percentage. The reduction in FNA was linearly correlated with fuel consumption percentage (r2 = 0.978). The response of FNC to fire was only affected by fuel type. None of the seven independent variables had any effect on SNA. The responses of SNC, NH4+, and NO3- depend on soil sampling depth. The responses of both NH4+ and NO3- to fire were significantly affected by fire type and time after fire but had different temporal patterns. The soil NH4+ pool increased ap- proximately twofold immediately after fire, then gradually declined to the prefire level after one year. The fire-induced increase in the soil NO3- pool was small (24% ) immediately after fire, reached a maximum of approximately threefold of the prefire level within 0.5- 1 year after fire, and then declined. This study has identified the general patterns of the responses of ecosystem N that occur for several years after fire. A key research need relevant to fire management is to understand how the short-term responses of N to fire influence the function and structure of terrestrial ecosystems in the long term.
Article
The natural age and stand structure of Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) Karst.), and birch (Betula pubescens Ehrh.) was studied in a virgin forest stand in northern Sweden. The stand has been unaffected by fire during the past 500 years. It is suggested that the variations in age structure and invasion pattern are the result of low-frequency climatic fluctuations influencing seed production, germination, and early survival of seedlings. The periods of climatic amelioration that occurred during the 1870s and during this century have been especially favourable to pine, resulting in a pine-dominated regeneration underneath a tree layer where spruce and birch are the most abundant species. This is contrary to generally accepted theories concerning postfire successional trends in this part of the boreal zone. It is concluded that small gap-phase replacement of trees by climatically induced regeneration and mortality events probably is the reason for the general weak correlation between age and size of trees. It is also concluded that this postfire succession will not lead to a total spruce dominance during a continuous succession under prevailing climate regimes.
Article
 The impact of soil organic carbon dynamics on the global carbon cycle is still largely uncertain despite studies of agricultural activities and control emissions of greenhouse gases to the earth's atmosphere. Improved knowledge of organic matter dynamics should lead to reduction in CO2 emissions. We used stable carbon isotope analysis to detect small changes in organic carbon storage and turnover upon soil treatments with a 13C-labeled aliphatic alcohol previously partitioned into soluble humic substances of varying hydrophobicity. We found that labeled organic carbon is increasingly protected from mineralization with increased hydrophobic character of humic matter. The stabilization of organic carbon by hydrophobic protection significantly reduced decomposition during incubation time in soil. Hydrophobic protection can become an useful tool to limit decomposition of fresh organic matter in soil and thus reduce CO2 emission from agricultural soils on a global scale.
Article
Nitrate production was detected in untreated soil of a Norway spruce (Picea abies L.) stand only after clear-cutting the stand. The aim of this study was to determine whether allelochemical inhibition of nitrification by monoterpenes played any role in inhibiting nitrification in the stand. Therefore, soils from a clear-cut plot and from a forest plot were studied. In the field, monoterpenes (mostly - and -pinenes), measured by soil microair diffusive samplers, were intensively produced in the forest plot, but not in the clear-cut plot. In the laboratory, soil samples taken from the forest plot produced only small amounts of monoterpenes, indicating that monoterpenes were mainly produced by the roots and not to great extent by the soil microbial population. The effect of a mixture of monoterpenes (seven major monoterpenes detected in the field) on net nitrification, net N mineralization and denitrification activities of soil from the clear cut plot, and on carbon mineralization of soils from both the forest and clear-cut plots, was studied in the laboratory. In both aerobic incubation experiments and in soil suspensions with excess NH4-N, nitrification was inhibited by exposure to the vapours of monoterpenes at similar concentrations at which they had been detected in forest plot. This indicates direct inhibition of nitrification by monoterpenes. Exposure to monoterpenes did not affect denitrification. However, it increased respiration activity of both soils. This could also indicate indirect inhibition of nitrification by monoterpenes, due to immobilization of mineral N. Thus it seems that monoterpenes could play a role in inhibiting nitrification in the forest soil.
Article
One hundred years of timber harvest and reduced fire frequency have resulted in the conversion of once open stands of ponderosa pine (Pinus ponderosa) forests to dense forests dominated by Douglas-fir (Pseudotsuga menziesii). Selection harvest and harvest with prescribed fire have been identified as possible tools to restore ponderosa pine stands to pre-settlement stand structures. Case studies were performed at three separate sites in western Montana to assess the influence of selection harvest and prescribed burning on soil N dynamics. These sites had been exposed to either selection harvest, selection harvest with prescribed burning, or a no-treatment control 0 (Lubrecht Experimental Forest), 2 (E/L Ranch), or 11 (Lick Creek Demonstration Site) years prior to initial soil analyses. Replicate soil samples were collected over at least two growing seasons at each site and analyzed for total C and N, potentially mineralizable N (PMN), short-term soil respiration rates, soil microbial biomass N, extractable NH4+ and NO3−, and soluble sugars (measured as 0.5 M K2SO4 extractable anthrone reactive carbon (KARC)). Selection harvest without prescribed burning had little or no influence on levels of available N or microbial activity relative to the control at all three sites. Selection harvest with prescribed fire, however, significantly increased extractable NH4+, NO3− and KARC immediately following treatment. Such differences were not observed 2 or 11 years following treatment. Potentially mineralizable N was significantly increased immediately following fire, but decreased to levels lower than the control 1 year following treatment. Levels of PMN were also found to be less than the control 2 and 11 years after treatment. Similarly, microbial biomass N was elevated immediately following prescribed burning, but was significantly lower than the control for up to 11 years following prescribed burning. Levels of mineralizable N were lowered within a year of treatment as a result of (1) N loss during soil heating, (2) N loss to plant uptake, and (3) potential leaching losses. The effect of reduced mineralizable N on long-term site productivity is not clear, however, these losses of N from the ecosystem should be considered along with stand mortality and yield when assessing the potential sustainability of forest management strategies.
Article
Fire history and stand structure was examined in twelve virgin forest stands situated within forest reserves in northern Sweden. The selected stands represented fire refuges as well as different successional stages after fire. Six of the stands were dominated by Norway spruce (Picea abies L. Karst.), three were dominated by Scots pine (Pinus sylvestris L.), and three were dominated by hairy birch (Betula pubescens Ehrh.) or aspen (Populus tremula L.). In 3 of the southernmost stands, the average fire interval was 34 to 65 years during the late 1600s to late 1800s, but since 1888 no fires had occurred in any of the stands. The absence of fire disturbance since 1888 is probably caused by the fire suppression in the overall landscape. The standing volume of living trees ranged between 87 and 511 m3 ha−1 while the volume of dead trees, including both snags and logs, ranged between 27 and 201 m3 ha−1. The volume of dead trees constituted ca. 30% of the total stem volume. In the conifer dominated stands, there was a statistically significant relationship between total stem volume, including both living and dead trees, and site productivity. A comparison between the amount of dead and living trees indicated substantial changes in tree species composition in several stands. It is suggested that data on the amount of dead trees, especially logs, and its distribution over decay classes could be used to examine the continuity of certain tree species. All stands had a multi-sized tree diameter distribution, which in most cases was similar to a reversed J-shaped distribution. In general spruce was numerous in the seedling cohort and in small diameter classes, indicating that its proportion in the stands was stable, or was increasing at the expense of pioneer tree species such as pine, aspen and silver birch (Betula pendula Roth.). The most numerous species in the seedling cohort, rowan (Sorbus aucuparia L.), was almost totally missing in the tree layer, indicating a high browsing pressure preventing rowan seedlings from growing into trees. The general increase of spruce and the sparse regeneration of pioneer species, in the stands previously affected by fire, are discussed in relation to natural disturbance regimes, biological diversity and nature conservation policies. It is proposed that reintroduction of fire disturbance is a necessity for future management plans of forest reserves. Other management practices to increase species diversity within forest reserves are also discussed.
Article
Net nitrification in forest soils is potentially problematic as it can promote nitrogen and cation losses as well as soil acidification and favor competing vegetation in regenerating forests. Rates of net nitrification have been associated with vegetation and soil types. However, this phenomenon is difficult to predict. Our objectives were to describe the relationships between stand types and net nitrification in the forest floor of five stand types (Paper birch: Betula papyrifera, trembling aspen: Populus tremuloides, white spruce: Picea glauca, jack pine: Pinus banksiana, white cedar: Thuja occidentalis) typical of the boreal mixedwood of northwestern Quebec and to experimentally verify the effect of pH and ammonium availability as well as the occurrence of persistent allelopathic inhibitors on net nitrification rates. All samples came from well-drained lacustrine clay soils and all forest stands originated from wildfires. The net accumulation of nitrate and ammonium was measured during the course of 6-week laboratory incubations. Nitrate accumulation was highest under aspen and birch, low under white spruce and cedar and not detectable under jack pine. The forest floor of jack pine had the lowest pH and exchangeable bases and the widest C:N ratio. Ammonium addition did not promote a significant increase in net nitrification. Increase of forest floor pH had a positive effect on net nitrification while acidification depressed it. The absence of net nitrate production in jack pine forest floor appeared to be related to the absence of nitrifiers as it was stimulated by the addition of a small amount of nitrifying forest floor. Our results suggest that jack pine and aspen, which occupy the same habitat, may have the capacity to change soil conditions in order to favor or depress nitrification. Observed rates of nitrification under these species is coherent with their preference for a particular form of mineral N. Although pH appeared as an important regulator of net nitrification, the effects of other factors are yet to be established.
Article
Nitrification in acid soils was first reported in the beginning of the 20th century. Although this finding has been well substantiated by countless studies since then, it has until recently remained unclear which micro-organisms were responsible for nitrate production at low pH. Substantial evidence now supports the role of chemolitho–autotrophic bacteria as the main nitrifying agents in most acid soils. Heterotrophs may make some contribution to nitrification in acid soils, but this is difficult to demonstrate conclusively. Current insights in the phylogenetic position of autotrophic nitrifying bacteria in acid soils and the mechanisms that may enable them to be active at low pH are presented. In addition, the spatial variability of their activity and their contribution to the flux of the greenhouse gas N2O is discussed.
Article
Soil drying and rewetting impose a significant stress on the soil microbial community. While wetting events are common in most environments, the short and long-term effects of soil rewetting on microbial processes have not been well studied. Furthermore, it is not clear if stress history is important to consider when modeling microbial controls on ecosystem dynamics. In this experiment, we manipulated the frequency of soil rewetting events during 2 months to determine how stress history influences the response of soil microbial communities to rewetting events. Two soils were collected from the Sedgwick Ranch Natural Reserve in Santa Ynez, CA, one from an annual grassland, the other from underneath an oak canopy. Soils were incubated in the lab and went through either 0, 1, 2, 4, 6, 9, or 15 drying–rewetting cycles over 2 months. Soil moisture content was adjusted so that the average moisture content over the course of the incubation was the same for all samples, compensating for the number of drying–rewetting cycles. Soils were analyzed for respiration rate, substrate utilization efficiency, nitrification potential, microbial biomass, and NH4+ and NO3− concentrations. Total CO2 loss during incubation significantly increased with number of rewetting events for oak soils but not for grass soils, where a large number of rewetting events decreased total CO2 loss. Exposure to frequent drying–rewetting events decreased the amount of CO2 released upon rewetting and dramatically increased the activity of autotrophic nitrifier populations. For up to 6 weeks after the last drying–rewetting cycle, respiration rates in soils exposed to a history of drying–rewetting events were substantially lower than their non-stressed controls. In all cases, the effects of the rewetting stress were greater in oak than in grass soils. The results indicate that drying–rewetting events can induce significant changes in microbial C and N dynamics and these effects can last for more than a month after the last stress. The frequency of drying–rewetting stress events has important ecosystem-level ramifications and should be incorporated into models of soil microbial dynamics.
Article
Heat generated during fire induces chemical oxidation of soil organic matter thereby altering carbon (C) and nitrogen (N) transformations. Prior soil fire history and soil moisture content at the time of heating can be confounding factors in the interpretation of the influence of heat on soil processes. In this study we evaluated how soil heating (160 and 380°C) under three moisture regimes (−0.03, −1.0, and −1.5 MPa) influences microbial activity and N mineralization in two soils: (1) not exposed to fire for the past 80 years, (2) recently exposed to wildfire. Initially, the fire exposed soil had lower basal respiration rates and lower concentrations of microbial biomass C, potentially mineralizable nitrogen (PMN), soluble hexose sugars, and NH4+–N, but higher NO3−–N concentrations than the soil not exposed to fire. Both soils responded similarly to elevated temperatures. Higher temperatures resulted in greater microbial mortality and a greater release of soluble sugars and NH4+–N. PMN concentrations increased at 160°C, but decreased at 380°C in both soils. The highest NH4+–N concentrations were observed in soils not previously exposed to fire that were incubated at −0.03 MPa after heating. Soils previously exposed to fire had low NH4+–N concentrations and high NO3−–N concentrations. Heating at low soil water potentials resulted in elevated concentrations of microbial biomass C and soluble sugars, and lower NH4+–N and NO3−–N concentrations. Initial C availability appeared to be an important factor in the recovery of microbial biomass during 14-d post-heating incubation, which was greatest after heating at 380°C and −1.5 MPa. Both soils demonstrated slow rates of recovery of nitrifying organisms despite high rates of net NH4+–N accumulation. It appears that low soil water potential at the time of heat exposure reduces losses of mineralizable N.
Article
The overall effects of fire on ecosystems are complex, ranging from the reduction or elimination of aboveground biomass to impacts on belowground physical, chemical and microbial mediated processes. Since a key component of overall ecosystem sustainability occurs belowground, recovery is tied to the soil's physical, chemical, and biological functions and processes. Depending on several fire severity measures, changes in belowground components can be either beneficial or deleterious to the entire ecosystem. Low-impact burning can promote a herbaceous flora, increase plant available nutrients, and thin over-crowded forests, all of which can foster healthy systems. Severe fires can often cause changes in successional rates, alter above- and belowground species composition, generate volatilization of nutrients and ash entrainment in smoke columns, produce rapid or decreased mineralization rates, alter C : N ratios, and result in subsequent nutrient losses through accelerated erosion, leaching or denitrification. In addition, changes in soil hydrologic functioning, degradation of soil physical properties, decreases in micro- and macrofauna, and alterations in microbial populations and associated processes can occur. The direct effect of fire on belowground systems is a result of the burning severity, which integrates aboveground fuel loading (live and dead), soil moisture and subsequent soil temperatures, and duration of the burn. The time for recovery of belowground systems will not only depend on the burning intensity and its effect on key ecosystem processes and components, but also on the previous land-use practices. Thus, the impacts of fire on belowground systems can be highly variable and may not be predictable. Our paper is a general review of the effects of fire on belowground systems with emphasis placed on the changes in physical, biogeochemical and biological properties of soils and the resulting consequences these changes have for ecosystem sustainability.
Article
Soil organic matter is often viewed as comprising large pools of carbon and nitrogen with long residence times. However, the organic horizon that lies on the soil surface in temperate forests is a dynamic component of ecosystem carbon and nitrogen cycling. Responses to elevated inputs of nitrogen in this organic layer are emerging as key facets of ecosystem retention or loss of dissolved nitrogen. Research along nitrogen deposition gradients in the USA and Europe reveals a link between the ratio of organic carbon:nitrogen in the forest floor and nitrogen turnover rates, nitrification and leaching losses. Characteristics and processes in the forest floor are now recognized as key indicators or determinants of ecosystem ‘nitrogen status’.
Article
The pattern of phenolic polymers (tannins) and monomers (phenolic acids, flavonoids) was followed from living organs (leaves and roots) of Picea abies (L.) Karst and Vaccinium myrtillus (L.) to litter types and humus, in two stands (1630 and 1860 m) of a mountain forest of Northen Alps (France). Quantitative and qualitative criteria were found to characterize species: abundance of tannins in bilberry; and, presence of p-hydroxyacetophenone a specific (and variable) metabolite in spruce needles. Compared to green foliage, an important loss of monomeric compounds in brown foliage was observed, when tanning activity greatly increased. As biodegradation proceeded the amounts of the degradation intermediates (protocatechuic, vanillic acids) increased in litters, and the influence of phenol-rich plants, such as bilberry, on organic layers was expressed by higher amounts of tanning activity and phenolic acids under bilberry cover. Because of its specificity and abundance, special attention might be given to p-hydroxyacetophenone in spruce forest floor. Control of phenolic compounds dynamics by their structure was equally emphasized.
Article
The effects of prescribed underburning on soil total C pools, total and inorganic N pools, and in situ net N mineralization were examined during a 1-year study in ponderosa pine (Pinus ponderosa Dougl. ex P. & C. Laws.) sites that had been experimentally burned 4 months, 5 years, or 12 years earlier. At the sites burned 4 months previously, total C concentration and inorganic N concentration increased significantly (p < 0.1) after prescribed burning, compared with unburned controls. However, inorganic N concentration declined during the 1-year duration of this study to reach the levels of the control plots at the end of the second growing season. At the site burned 5 years previously, total C and N concentrations, inorganic N concentration, and net N mineralization decreased significantly after prescribed burning. At the sites burned 12 years previously, N and C pools were not affected, but net N mineralization decreased significantly after burning. The decrease in net N mineralization is likely caused by a decrease in substrate quantity 5 years after burning, and by changes in substrate quality 12 years after burning. A long-term decrease in net N mineralization in the N-poor ponderosa pine stands of central Oregon may result in a decrease in long-term site productivity and may explain the observed pattern of long-term decrease in stand growth after prescribed burning.
Nitrification in acid soils: micro-organisms and mechanisms
  • De Boer
De Boer, W., Kowalchuk, G.A., 2001. Nitrification in acid soils: microorganisms and mechanisms. Soil Biology & Biochemistry 33, 853-866.
Effects of drying-rewetting frequency on soil carbon and nitrogen transformations
  • Fierer