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Article

Fire-Derived Charcoal Attracts Microarthropods in the Litter of Boreal Deciduous Forest

by
Anjelica Kondratova
and
Semyon Bryanin
*
Institute of Geology and Nature Management, Far East Branch of Russian Academy of Sciences, Blagoveshchensk 675000, Russia
*
Author to whom correspondence should be addressed.
Forests 2023, 14(7), 1432; https://doi.org/10.3390/f14071432
Submission received: 14 June 2023 / Revised: 7 July 2023 / Accepted: 11 July 2023 / Published: 12 July 2023
(This article belongs to the Section Forest Ecology and Management)
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Abstract

:
Larch forests in the permafrost zone of Eastern Eurasia are exposed to frequent wildfires, which are expected to increase with climate warming. However, little is known about how fire-derived charcoal is linked to the decomposition process in these forests. Fire-derived charcoal can affect the faunal communities in the forest litter. In a two-year field litterbag experiment, we investigated the effect of fire-derived charcoal on the colonisation by microarthropods (Collembola and Acari) of three decomposing litter species dominant in boreal larch forests. Charcoal addition led to an average 15% decrease in body size of collembola but significantly increased their abundance by 5 times throughout the experiment and acari by 1.5 times in the second year of decomposition, and this effect was consistent across all litter species. The increased microarthropod community may have hampered microbial activity and mass loss rate in the presence of charcoal. Charcoal altered the microarthropod community composition, increasing the proportion of collembola up to 20% compared to acari. The difference in abiotic conditions (increased litter water content during dry periods) induced by fire-derived charcoal was a more substantial factor determining the microarthropod community than litter species in the boreal larch forest. Our results indicate that fire-derived charcoal influences the biological drivers of decomposition in boreal larch forests, stimulating the growth of microarthropod community in decomposing litter.

1. Introduction

It is predicted that climate change will lead to a significant increase in the intensity and frequency of forest fires, resulting in nearly one-third of the carbon from burned biomass in boreal forests being retained as fire-derived charcoal on the soil surface [1,2,3]. Charcoal is resistant to decomposition [4], but it is not an inert product of combustion. Furthermore, charcoal alters the characteristics of soil and litter [5,6,7] and affects organisms involved in litter decomposition [8,9,10]. However, the effect of charcoal on mesofauna as important decomposers remains unclear, especially in fire-affected boreal forests of Eastern Eurasia.
Microarthropods are involved in organic matter decomposition directly through fragmentation and consumption of litter and indirectly through regulation of microbial activity [11]. Fire-derived charcoal retains in litter and upper soil layers and accumulates during repeated fires [12]. Most studies on the interaction between microarthropods and pyrolysis products are either laboratory experiments or experiments in agricultural systems [13,14]. To date, to the best of our knowledge, there is no understanding of the charcoal impact on microarthropods during litter decomposition in boreal forests.
Due to the thick forest floor, temperate and boreal forests are more abundantly populated by microarthropods (acari and collembola) than warm and even tropical forests [15]. As microbivores and detritivores [16], microarthropods can enhance decomposition by stimulating and regulating microbial communities and directly consuming litter [11]. It has been shown that the number of microarthropods increases with litter decomposition time [17,18,19]. However, the acceleration of litter decomposition is not always observed with an increase in microarthropods [20,21]. Even without directly affecting mass loss, acari and collembola are essential in stabilising soil organic matter. For example, in a laboratory experiment where the community of collembola increased, it was found that collembola promoted the influx of carbon from litter as well as plant-derived components (chlorophyll and pheophytin) into the soil, modifying soil organic matter at the molecular level and increasing carbon availability to soil microorganisms [21].
Changes in the physicochemical and microclimatic conditions of the environment can also affect the quantity and morphological characteristics (body size and shape) of microarthropods. Studies conducted at the Global Change Experimental Facility (Germany) have shown that experimental climate change (temperature increase and precipitation reduction) reduced the average body size of collembola and acari [22]. It has also been found that the length of collembola increases with soil water content [23]. Acari, mainly mites, are more drought-resistant than collembola [23,24]. Charcoal, by influencing physicochemical litter properties, including increased water content [6], could promote greater microarthropod colonisation as well as alter their size in the litter of pyrogenic boreal forests.
At the same time, the density of microarthropod communities in boreal forests might be affected by the species of litter [17,25]. A field experiment conducted in a southern taiga forest showed that microarthropods more likely colonised lime leaves than spruce needles [25]. Conversely, a three-year litterbag experiment on the fine roots and litter of Chamaecyparis obtusa in Japan showed an increase in microarthropods in the substrate with higher lignin content compared to easily decomposable litter [18]. An experiment in a temperate deciduous forest zone in Germany showed no effect of different litter species on the number of acari [26]. Thus, data on microarthropod colonisation of different litter species are contradictory. The process is not well understood, and, to the best of our knowledge, there are no data on charcoal effect on microarthropods’ litter species preference.
The study aimed to determine how charcoal in boreal larch forests affects the abundance, size and community structure of major group of microarthropods (collembola, acari) depending on the litter species (grass, birch leaves, larch needles) and decomposition stage. We hypothesised that charcoal promotes an increase in the number and size of microarthropods due to increased water content and increased microbial activity; we expected a more pronounced effect for collembola that might feed on fungi. We also hypothesised that regardless of the presence of charcoal, the abundance of both acari and collembola depends on the species of litter and decomposition stage.
Our two-year field study was aimed at understanding the relationship between charcoal and microarthropod, which is important for predicting potential responses in the functioning of each component of the forest ecosystem to the increased frequency and area of fires due to climate change.

2. Materials and Methods

2.1. Study Site

The study was conducted in Eastern Eurasia in the zone of discontinuous permafrost (53°50′ N, 127°10′ E) in a natural undisturbed larch forest including birch and aspen (Larix gmelinii (Rupr.) Rupr, Betula platyphylla, Populus sp.) with lingonberry and herb undergrowth. The study area is a part of Zeysky State Nature Reserve, where all human activity was strictly prohibited in the area of ca. 100 km2 in the East of Tukuringra mountain ridge. The average annual air temperature is −0.7 °C, with the minimum monthly average air temperature in January (−19.3 °C) and the maximum in July (+19.1 °C). The average annual precipitation is 527 mm, of which 77% falls as rain from July to September. The soils of the study area are represented by raw-humus-rich Dystric Cambisols (WRB 2014) [27]. These soils in intact condition have a thick litter layer (~10 cm), usually with several sub horizons of different decomposition degree and high acidity [28]. However, due to repeated fires, these soils often have charcoal particles and shifted physicochemical characteristics in the surface horizons [28,29,30].

2.2. Litterbag Experiment

In the forest area of 1 km2, we set 7 study plots with a size of 5 × 5 m, and the minimal distance between plots was 20 m. To study the effect of charcoal on decomposition and arthropod communities, we established a field litterbag experiment. We incubated the three species of litter typical for larch-birch forests: leaves of Betula platyphylla Sukacz., “birch”; needles of Larix gmelinii (Rupr.) Rupr., “larch”; and above-ground parts of herbs (Calamagrostis sp. and Carex globularis L.), “grass”. Litter was collected from litter traps, and herbaceous vegetation was collected by cutting plants on 10 plots of 1 m2. Charcoal for treatment was produced from larch wood in a muffle furnace at 450 °C in an oxygen-free environment. After pyrolysis, charcoal was crushed and passed through a set of sieves to obtain a homogeneous fraction of 1–2 mm. For the incubation, we used 100 × 100 mm bags made of two species of material: the upper part of nylon mesh with a mesh size of 2 mm and the lower part of nylon with a mesh size of 35 μm. Such a combination allowed us to provide access for soil fauna, and the bottom layer prevented the loss of decomposing litter fragments and charcoal particles while not hindering water transport [31].
The experiment had two treatments: “control” with only litter and “charcoal” with litter and charcoal in the same bag. In the control treatment, 4 g of litter was evenly distributed in the bag. In the charcoal treatment, 4 g of charcoal was placed at the bottom, covering the entire bag area, then 4 g of litter was placed on top of the charcoal. This approach mimics the natural process of litter accumulation over the charcoal layer in recently burned forests. For each treatment, 3 species of litter were placed on 7 plots in the space. Bags of all litter species and both treatments were randomly placed at a distance of at least 10 cm between bags. Bags were placed on the surface of the forest floor, slightly covered with fresh litter for better fixation to the ground surface. On each sampling date, 6 bags of each litter species were randomly collected from plots. The experiment started on 4 October 2019, when mean daily temperatures reached zero at the end of the natural leaf fall period and active shedding of larch needles occurred. The first microarthropod census was conducted one year after the start of the experiment, and the second one was conducted two years after.

2.3. Microarthropod Extraction and Quantification

Collected litterbags were transported to the laboratory in a cooler and kept in the dark at 4 °C degrees until microarthropod extraction. Microarthropods were extracted using dry Tullgren funnels for 48 h and fixed in 70% ethanol solution with 5% glycerin for storage and further analysis. Collembola and acari were counted using a stereoscopic microscope (Stereoscopic Microscope NSZ-800, Ningbo Yongxin Optics Co., Ltd., Ningbo, China). Microarthropod abundance was expressed as number of individuals per 1 g of absolutely dry litter that remained at a given sampling date. The body length (from the head tip to the end of the abdomen) of each collembola individual, regardless of developmental stage, was measured with an accuracy of 0.01 mm. After microarthropod extraction, the litter was dried at 40 °C to a constant weight, and the mass residue was determined as a percentage of the initial mass. Water content was determined in the samples after 218 days, one and two years after the start of the experiment.

2.4. Microbial Activity

Microbial activity is represented as a proxy of respiration over litterbags gathered from field. Measurements of litter respiration were conducted over all litterbags gathered at the end of 1st and 2nd years of the experiment. The CO2 flux was measured under laboratory conditions at constant temperature of 22 °C with a closed static chamber system. The system comprised an infrared gas analyser (IRGA, GMP343, Vaisala, Vantaa, Finland) attached to a 0.497-L cylindrical chamber. We enclosed each litterbag in the chamber and measured the CO2 concentration for 5 min. To reduce the effects of air disturbance caused by opening the chamber, data for the first and last 30 s were not used. We calculated the CO2 flux (nmol g−1 s−1) according to the method of [31,32].
To assess whether charcoal was colonised by microbes, we observed charcoal particles using a scanning electronic microscope (SEM) before and after incubation. Morpho structural studies were carried out using the SEM at the Amur Center of Mineral-Geochemistry Investigation in the Institute of Geology and Nature Management. Image captured on JEOL JSM-6390LV, JEOL, Tokyo, Japan at 15 kV in the secondary (SEI) and reflected electron (BES) modes. The crushed charcoal particles were fixed on a conductive adhesive tape, and conductive carbon coating was applied to the samples by vacuum-thermal spraying.

2.5. Calculations and Statistical Analysis

To assess mesofauna diversity, we used common ecological indexes. We identified collembola of 6 superfamilies (Neanuroidea, Poduroidea, Hypogastruroidea, Entomobryoidea, Isotomoidea, Tomoceroidea) and 1 family (Neelidae) according to Cipola et al., 2018 [33]. The community diversity was assessed by alpha (α) and beta (β) diversity. The α–diversity of collembola communities assessed with the Shannon–Wiener index (H) and Pielou evenness index (J). The β-diversity calculated based on paired comparisons of frequency of occurrence by Jaccard dissimilarity index (Si) as follows:
H = − ∑ P i ln ⁡ P i J = H / ln ⁡ S  
where S is the number of groups of soil mesofauna, and Pi is the proportion of the individuals of i-th group to the total individuals.
S i = j / a + b − j
where j is the number of species found in both sites and a is the number of communities in the control, while b is the number of communities in char. Data were analysed in R-studio 2022.12.0 Build 353 [34]. All data were checked for normality and homogeneity of variance. Hypothesis testing for differences and significance of calculated statistics between control and charcoal treatments was performed using the t-test (for parametric data) and Wilcoxon t-test (for nonparametric data). One-way analysis of variance (ANOVA) followed by Tukey’s HSD post hoc test or the nonparametric Kruskal–Wallis test with Dunn’s test was used to compare differences in water content, microarthropod abundance and litter mass loss between litter species. Differences were considered statistically significant when p < 0.05. The correlation between variables was calculated using Pearson’s method.

3. Results

3.1. Water Content Dynamics

In both the control and charcoal, water content did not depend on the litter species at any sampling times (p < 0.05, Figure 1). We observed an increase in water content in charcoal compared to the control after 218 days and after one year of decomposition (p < 0.05, Figure 1).

3.2. Abundance of Microarthropods

The abundance of acari significantly (p < 0.05) increased in the control in the second year for all studied litter species (Figure 2). The abundance of collembola in the control increased, but this effect was non-significant. In the presence of charcoal, the increase in microarthropod abundance is more pronounced than in the control treatment (Figure 2). We found no effect of litter species on microarthropod abundance in control or charcoal treatments (p > 0.05).
Charcoal significantly influenced the abundance of acari and collembola, and this influence depended on decomposition time (Figure 2). Collembolas were more numerous in all species of litter in charcoal than in the control, especially in the second year. However, a statistically significant increase in the abundance of collembola in the charcoal treatment compared to the control in the first year was only found for birch litter (p = 0.023) and in the second year for birch (p = 0.014) and larch (p = 0.019). The charcoal effect on the abundance of acari was only found by the end of the second year. In the presence of charcoal, there was an increase in the abundance of acari in grass and larch, but a statistically significant increase was observed only in birch (p = 0.023).
Collembola diversity based on the Shannon–Wiener index did not differ between the control and char in all sampling dates and did not depend on litter species (p > 0.05) (Figure S1). The low Pielou evenness index (J) indicates an unequal abundance of superfamilies in the microarthropod community due to the predominance of Isotomoidea and Entomobryoidea in both control and char samples. After the second year of decomposition, the similarity of the macroarthropod community between the control and char was 50%–75% (Jaccard dissimilarity index (Si) for birch was 0.5, for grass and larch 0.75).

3.3. Collembola Length

In the control, the effect of decomposition time on the mean body length of collembola individuals was not significant (p > 0.05) (Figure 3). At the same time, in the presence of charcoal, it decreased in the second year compared to the first in birch (p = 0.013) and larch (p = 0.034) and tended to decrease in the grass. The species of litter did not affect the mean body length (p > 0.05). Compared to the control, charcoal led to a fourfold increase in the total length of collembola (on average for all litter species), and this effect was associated with a larger number of collembola (Figure 2) but not with an increase in average body size (Figure 3).

3.4. Proportion of Microarthropods

The ratio of acari and collembola during decomposition did not depend on the litter species (p > 0.05). Still, it was associated with decomposition time and the presence of charcoal (Figure 4). In the control, we observed the dominance of acari (p < 0.05) in both the first and second years. However, with the decomposition with charcoal, the proportion of collembola increased (Figure 4). Charcoal might promote an increase in the proportion of collembola by 20% compared to the control. Thus, in the control, after the first year, the proportion of collembola on average for all litter species was 16%, but in charcoal, it increased to 37%; at the end of the second year, the proportion of collembola was 27.5% and 52% in the control and charcoal, respectively.

3.5. Microbial Activity

Litter species and charcoal did not affect CO2 respiration at any sampling times (p > 0.1). Mean respiration in the control after the first year was 2.76 and 5.62 nmol g−1 s−1 at the end of the second year (Table 1). We observed extensive colonisation of charcoal by fungi hyphae after field incubation (Figure 5). Hyphae were more abundant on the surface, however, found inside of charcoal pores.

3.6. Litter Mass Loss

After the first year, in the control, the remaining mass of grass was 67%, while larch was 83% and birch 74% (Table 1). At the end of the second year, the remaining mass did not differ between litter species and was about 50%. Throughout the experiment, charcoal did not affect litter mass loss, except for faster decomposition of larch in the beginning of the incubation.

4. Discussion

Our study showed that fire-derived charcoal in the frequently burned boreal forests, affecting body size, number and proportion of microarthropods in a decomposing litter through alteration of physical and physic-chemical litter parameters.
We found an increase in the abundance of microarthropods with litter decomposition, both in the control and charcoal (Figure 2). This is consistent with previous studies and indicates an increasing role of reducers in organic matter transformation over time [17,18,19]. We expected higher colonisation of collembola and acari in grass and birch litter but not in larch needles, as a previous study showed that mesofauna prefers more labile litter [25,35]. Thus, an experiment in a spruce forest in the southern taiga zone showed that microarthropods prefer to inhabit a labile leaf litter (linden leaves) compared to spruce needles [25]. However, our hypothesis was not confirmed—we did not find statistically significant differences in the number of acari and collembola between litter species in the control. Plant litter provides food and habitat for litter decomposers [36], among which mesofauna, compared to macro- and microfauna, depends less on litter as a food resource. For mesofauna, the physical quality of litter is rather important [37]. Larch needles, in terms of chemical (food resource) and physical (habitat) characteristics, are more similar to leaf than to evergreen needles [38]. This feature may explain the similarity of microarthropod numbers between larch needles and other litters in our experiment in the control. The presence of charcoal did not change the preference of microarthropods but might have increased their number.
We found a positive effect of charcoal on the collembola number in all litter species, significant for birch and larch at early decomposition stages, and this effect was amplified over time (Figure 2). The presence of charcoal resulted in an increase in the number of acari in all species of litter in the second year of the experiment, and this effect was statistically significant for birch (Figure 2). The increase in the number of microarthropods might be related to the charcoal effect on environmental conditions (humidity, sorption of water-soluble substances, etc.) and changes in microbial abundance that serves as a food resource [39]. Our study showed an increase in litter water content in the presence of charcoal under water deficiency conditions (Figure 1). This is consistent with the previous study on oak leaf decomposition, which found that charcoal contributed to increased litter water content when the water content was less than 50% [6]. We also found that in charcoal treatment, the number of collembola increased more than that for acari. Charcoal probably creates more favourable conditions for the reproduction of collembola. In our experiment, charcoal promoted an increase in the proportion of collembola compared to acari, and this effect was the same for all litter species (Figure 4). Collembola have a thin and permeable cuticle, which makes them very vulnerable to drought [40]. Therefore, the number of collembola often positively correlates with water content [41]. It is also known that acari (mainly oribatid mites) are more resistant to drying out than collembola [23,24]. An experiment in Japan on the decomposition of different litter species [18] showed that the number of collembola was determined mainly by water content, and changes in the ratio of collembola and acari were mainly determined by abiotic conditions rather than litter species. The presence of charcoal in our experiment increased litter water content during dry periods (Figure 1), which could promote the survival of collembola under water deficiency conditions and be one of the reasons for the increase in the number and share of collembola relative to acari. Given the similar trophic niche of acari and collembola, which are mainly microbivores and detritivores feeding on fungi, litter and other microorganisms [16], changes in water content in the presence of charcoal are one of the likely explanations for the observed changes in the ratio of these microarthropods. An analysis of the α-diversity of the collembola assemblage using the Shannon–Wiener index (H) and the Pielou index showed little difference between the control and char. However, the similarity in the composition of collembola superfamilies between the control and char, as determined by the Jaccard dissimilarity index (Sj), was 50% for birch and 75% for grass and needles. Charcoal led to a decrease in the similarity of the superfamily composition compared to control samples, and this effect was more pronounced for leaves litter (Figure S1). According to our observations, the differences in the composition of the collembola communities in control and charcoal samples could be derived from higher abundance of Neanuroidea in charcoal samples. Neanuroidea are high-level consumers and feed on different groups of microfauna and microorganisms in contrast to the quantitatively dominant Isotomoidea in our samples, whose bedforms are more detritophagous [42]. The higher abundance and number of Neanuroidea in the charcoal treatment may indicate greater microbial activity. This is probably of interest and requires a more detailed taxonomic analysis in future studies. Interestingly, in our experiment, the increase in microarthropod communities in the presence of charcoal did not lead to an acceleration of litter mass loss (Figure 2, Table 1). Microscopic observations of the inhabited space of coal have shown that the surface and pores of charcoal can serve as a microenvironment for soil organisms [43]. This is confirmed by our images of particles from the experiment (Figure S1). Increased foraging due to colonisation of the charcoal surface by at least fungi could be the reason for the growth of the microarthropod community. We did not consider the surface and pores as a habitat for microarthropods because the microarthropods could migrate during transport and subsequent separation of the litter from the charcoal in the laboratory. This is undoubtedly a limitation of our study; however, due to the observed colonisation by fungal hyphae in the charcoal, we expected increased emissions from charcoal bags compared to controls.
However, in the charcoal treatment, we found no increase in CO2 emission as an indicator of microbial activity in the contrast to previous findings [8,9] (Table 1). The positive effect of charcoal on microbial activity may be diminished by increased microarthropod community. This opposite effect of charcoal and microarthropods can be expressed in the lack of differences in mass loss. The lack of acceleration of decomposition with increasing microarthropod numbers has been shown in some other studies [20,21,25], which may have several explanations. The increase in microarthropod numbers in the presence of charcoal may be due to an increased number of fungi that decompose litter [25]. The active consumption of saprotrophic microflora by predator species of collembola may slow down plant litter decomposition. For example, a decrease in microscopic fungi has been shown at the maximum activity of microarthropods in coniferous and broadleaf forests in the southern taiga zone [25]. The activity of collembola can lead to a disruption of the mycelial bond between soil and litter, slowing down the entry of mobile soil nitrogen into plant residues and the rate of litter decomposition [44].
Moreover, the magnitude of the mass loss indicator is not solely related to the loss of organic matter during decomposition [45]. Thus, an increase in the numbers of acari and collembola suggests an increase in their biomass, necromass and excreta [21,34], as well as the accumulation of microbial and faunal transformation products [45]. The biomass of collembola is often estimated based on regression equations that assess weight based on linear dimensions [46,47,48]. The average body size of soil microarthropods has been shown to negatively correlate with their density [22]. In our experiment, charcoal, by promoting the reproduction of collembola, probably increased the number of young individuals of smaller size. Despite some decreases in the mean length of individuals (Figure 3) in the presence of charcoal (p < 0.05), the total length per 1 g of litter in the charcoal treatment was significantly higher than in the control as a result of increased number (Figure 2 and Figure 3, p < 0.05). This might suggest a higher biomass, necromass and amount of excreta and thus a greater contribution of collembola to the transformation and accumulation of C in the charcoal treatment. Therefore, the “mass loss” indicator did not fully characterise the effect of increasing microarthropod numbers in the presence of fire-derived charcoal on organic matter transformation.
However, previous research indicates the critical role of microarthropods in organic matter transformation, even without visible impact on mass loss [11,21,49]. For example, an experiment on decomposition in tallgrass prairies showed that a reduction in the number of microarthropods (collembola and acari) led to a decrease in the input of carbon from litter into the soil and a significant narrowing of the C/N ratio of organic matter derived from litter, which in the long term (based on a model) will slow down soil organic matter accumulation [11]. Also, a field “litter-bag” experiment in cold alpine forests showed that soil fauna, dominated by collembola, contributes significantly to the accumulation of humic substances in the soil during litter decomposition (more in coniferous forests), promoting soil carbon sequestration [49]. Furthermore, the presence of collembola led to greater availability of C from litter for the soil microbial community and transport of compounds obtained from alder (chlorophyll and its breakdown product pheophytin) into the soil, indicating that collembola modifies soil organic matter at a molecular level [21]. Thus, fire-derived charcoal, by promoting an increase in the microarthropod community density, can affect carbon transformation and sequestration processes in boreal forests.

5. Conclusions

Our results suggest that fire-derived charcoal affects biological processes in boreal larch forests, stimulating the growth of the microarthropod community in decaying litter. The difference in abiotic conditions caused by charcoal is a more decisive factor determining the microarthropod community than the litter quality. Since the microarthropod abundance in our experiment was weakly related to litter species, microarthropods will likely be more abundant in the litter layer rich in charcoal, regardless of the vegetation species at different stages post-fire succession. In the presence of charcoal, shifts in microarthropod communities are possible, as charcoal creates more favourable conditions for collembola reproduction than acari.
Our results open up prospects for future research. Thus, we must understand how long the charcoal’s influence on microarthropods will last after the formation, the consequences of shifts in the composition of soil microarthropod groups for the decomposition process in the presence of charcoal and whether the effect of charcoal on soil fauna depends on its stocks in the litter layer and soil. Given the vulnerability of larch forests in the sporadic permafrost zone to climate warming, future research might contribute to predicting the effect of increasing fire frequency and pyrogenic carbon stocks in soils on the carbon stabilisation function in northern forests.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/f14071432/s1, Figure S1. Characteristics of collembola diversity, evenness and dissimilarity assessed by Shannon–Wiener, Pielou and Jaccard index. Data are means ± SE for n = 7.

Author Contributions

Conceptualisation: A.K. and S.B.; Methodology: A.K. and S.B.; Writing—original draft preparation: A.K.; Writing—review and editing: S.B. All authors have read and agreed to the published version of the manuscript.

Funding

The study was funded by a grant from the Russian Science Foundation, No. 23-27-00346, https://rscf.ru/en/project/23-27-00346/, accessed on 1 July 2023.

Data Availability Statement

The data are available on request from the corresponding author.

Acknowledgments

We would like to thank Irina Smuskina for data visualisation and statistical analysis. We are grateful to Makoto Kobayashi for the valuable comments and suggestions to earlier versions of this manuscript.

Conflicts of Interest

The authors declare that the research was conducted without any commercial or financial relationships that could be construed as potential conflicts of interest.

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Forests 14 01432 g001 550
Figure 1. Dynamics of the water content of litter in control and charcoal. Data are means ± SE; asterisks indicate the statistical significance of differences between treatments for each litter species: * p < 0.05, ** p < 0.01, *** p < 0.001, ns—not significant.
Figure 1. Dynamics of the water content of litter in control and charcoal. Data are means ± SE; asterisks indicate the statistical significance of differences between treatments for each litter species: * p < 0.05, ** p < 0.01, *** p < 0.001, ns—not significant.
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Forests 14 01432 g002 550
Figure 2. Number of collembola and acari in control and charcoal depending on the species of litter and decomposition time, means ± SE. Asterisks above the bars indicate the statistical significance of differences in the number of collembola and acari between control and charcoal for each species of litter: * p < 0.05, ns—not significant.
Figure 2. Number of collembola and acari in control and charcoal depending on the species of litter and decomposition time, means ± SE. Asterisks above the bars indicate the statistical significance of differences in the number of collembola and acari between control and charcoal for each species of litter: * p < 0.05, ns—not significant.
Forests 14 01432 g002
Forests 14 01432 g003 550
Figure 3. Collembola body length of control and charcoal, depending on the litter species and decomposition time, means ± SE. Asterisks indicate the significant differences in collembola length between control and charcoal for each species of litter: * p < 0.05, ** p < 0.01, ns—not significant.
Figure 3. Collembola body length of control and charcoal, depending on the litter species and decomposition time, means ± SE. Asterisks indicate the significant differences in collembola length between control and charcoal for each species of litter: * p < 0.05, ** p < 0.01, ns—not significant.
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Forests 14 01432 g004 550
Figure 4. Relative proportion of collembola and acari (% of the total number in g of litter) of control and charcoal depending on the species of litter and decomposition time. Asterisks between bars indicate significant differences in the proportion of collembola and acari, and asterisks above bars indicate significance of differences in the proportion of collembola between control and charcoal for each species of litter: * p < 0.05, ** p < 0.01, *** p < 0.001, ns—not significant.
Figure 4. Relative proportion of collembola and acari (% of the total number in g of litter) of control and charcoal depending on the species of litter and decomposition time. Asterisks between bars indicate significant differences in the proportion of collembola and acari, and asterisks above bars indicate significance of differences in the proportion of collembola between control and charcoal for each species of litter: * p < 0.05, ** p < 0.01, *** p < 0.001, ns—not significant.
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Forests 14 01432 g005 550
Figure 5. Scanning electron micrograph of charcoal before the incubation (a) and extensive fungi hyphae colonisation 2 years after inside the charcoal (b) and on the surface (c).
Figure 5. Scanning electron micrograph of charcoal before the incubation (a) and extensive fungi hyphae colonisation 2 years after inside the charcoal (b) and on the surface (c).
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Table
Table 1. The remaining mass and respiration of control and charcoal after 1 and 2 years of decomposition (mean ± SE) and significance of differences between treatments. Significant p-values at p 0.05 are bolded.
Table 1. The remaining mass and respiration of control and charcoal after 1 and 2 years of decomposition (mean ± SE) and significance of differences between treatments. Significant p-values at p 0.05 are bolded.
GrassLarchBirch
YearControlCharp-ValueControlCharp-ValueControlCharp-Value
remaining mass, g
166.9 ± 1.467.7 ± 0.60.9183.4 ± 2.376.8 ± 1.20.0474.0 ± 1.570.0 ± 1.30.2
254.2 ± 1.448.8 ± 2.80.3250.8 ± 3.951.1 ± 4.40.9248.5 ± 3.150.1 ± 3.20.8
CO2, nmol g−1 s−1
12.86 ± 0.671.52 ± 0.120.082.45 ± 0.542.34 ± 0.210.852.67 ± 0.292.35 ± 0.230.42
27.05 ± 1.646.76 ± 0.760.874.84 ± 0.535.76 ± 0.560.265.68 ± 0.665.32 ± 0.860.74
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Kondratova, A.; Bryanin, S. Fire-Derived Charcoal Attracts Microarthropods in the Litter of Boreal Deciduous Forest. Forests 2023, 14, 1432. https://doi.org/10.3390/f14071432

AMA Style

Kondratova A, Bryanin S. Fire-Derived Charcoal Attracts Microarthropods in the Litter of Boreal Deciduous Forest. Forests. 2023; 14(7):1432. https://doi.org/10.3390/f14071432

Chicago/Turabian Style

Kondratova, Anjelica, and Semyon Bryanin. 2023. "Fire-Derived Charcoal Attracts Microarthropods in the Litter of Boreal Deciduous Forest" Forests 14, no. 7: 1432. https://doi.org/10.3390/f14071432

APA Style

Kondratova, A., & Bryanin, S. (2023). Fire-Derived Charcoal Attracts Microarthropods in the Litter of Boreal Deciduous Forest. Forests, 14(7), 1432. https://doi.org/10.3390/f14071432

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