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Temporal dynamics of carbon and nitrogen in the surface soil and forest floor under different prescribed burning regimes
... Studies conducted in recent decades in different ecosystems around the world indicate that the effect of fire on soil properties is widely variable and depends on several factors such as the type, intensity, and duration of the fire and its position in the landscape (González-Pérez et al., 2004;Afifi and Oliveira, 2006;Neill et al., 2007;Shakesby, 2011;Bento-Gonçalves et al., 2012;Brown et al., 2013;Inbar et al., 2014;Oliver et al., 2015;Fultz et al., 2016;Alcañiz et al., 2018). Some studies found an increase in pH and nutrient availability after prescribed fire (Kennard and Gholz, 2001;Úbeda et al., 2005;Scharenbroch et al., 2012) and a reduction in soil organic matter (SOM) (Muqaddas et al., 2016), while others have found no significant changes (Meira-Castro et al., 2014;Valkó et al., 2016). In addition, little is known about the effect of prescribed fires on soil C compartments, especially in colloidal fractions, and on the quality and quantity of humic materials. ...
... This result is contrary to that observed in the literature. Many authors have reported an increase in pH after prescribed fires due to OH losses, SOM oxidation, and the release of cations in the ashes (Switzer et al., 2012;Muqaddas et al.,2016;Alcañiz et al., 2018). However, there are studies in which the pH remained unchanged after controlled burning (Lavoie et al., 2010;Switzer et al., 2012;Meira-Castro et al., 2014). ...
... A sharp reduction in the LOC was observed at 240 DAPF in both landscape compartments (footslope and backslope). In a study conducted by Muqaddas et al. (2016) in a tall high forest area in Southeast Queensland, the LOC contents were lower in the two yearly burning areas compared to the four yearly burning areas and, according to the authors, this reduction in the two yearly burning areas was equal to 48 % compared to the unburned area. According to Arocena e Opio (2003), the reduction in the labile compartment of C and N may be partially due to the loss of the biome of the forest/litter and soil C and N during the fire. ...
There is a need for greater knowledge about the medium- and long-term effects of prescribed fire management on soil in ecosystems prone to wildfires and more vulnerable to climate change. This study examined the short- and medium-term effects of prescribed fire on soil chemical properties and chemical fractions of soil organic matter (SOM) in two positions of the landscape in a high-elevation grassland environment. The ecosystem is located in the mountain peaks of southeastern Brazil associated with the Atlantic Forest biome. Prescribed fire was conducted in 2017 to reduce understory vegetation and thus prevent potential severe wildfires. Soil samples were collected at the layers of 0.00-0.10, 0.10-0.20, and 0.20-0.40 m, at eight composite sampling. The composite samples were collected on five different occasions: before the prescribed fire, and 10, 30, 90, and 240 days after the prescribed fire. Soil chemical properties, total organic carbon, labile C, and chemical fractionation of SOM were analyzed. All soil properties investigated were affected by the prescribed fire, with variations in landscape position, duration of effect, and soil layer. In the backslope area, the medium-term effect of fire was negative and induced soil degradation and induced soil degradation. In the footslope area, the system showed greater resilience to the effects of fire, as indicated by the recovery of the soil’s chemical properties. These results can help assess the suitability of controlled burning of vegetation for managing risks of fire in mountainous regions, such as high-elevation grasslands.
Keywords
Histosols; soil indicators; organic matter; soil management; Campos de Altitude
... After repeated prescribed fires (Table 2), a few increases [19,20,31,32] or decreases [28] in soil C content have been observed, some of them dependent on fire frequency [33] or season [34][35][36]. Most decreases have been recorded in eucalypt and pine forests in Australia [22,[37][38][39][40] but all of them were dependent on fire interval, with more frequent fires causing a reduction in C but less frequent fires resulting in fewer effects or no change; this pattern was also observed in oak forests [26]. However, the total lack of change [23][24][25][41][42][43][44][45][46][47][48] is the most frequent response, especially in oak and pine forests. ...
... The effect of the frequency of prescribed fires varies depending on the ecosystems and the conditions under which the burning is conducted. Thus, in some cases the C response is found to be independent of the prescribed fire frequency [19,25,41,42,45,46], whereas in other cases fire interval affected this variable [22,26,33,[37][38][39][40]. A more marked response to a shorter fire interval has been attributed to the cumulative combustion of the soils organic matter, litter consumption and other firerelated C inputs [26,38] and the lack of time for complete recovery between prescribed fires [39,40]. ...
... Thus, in some cases the C response is found to be independent of the prescribed fire frequency [19,25,41,42,45,46], whereas in other cases fire interval affected this variable [22,26,33,[37][38][39][40]. A more marked response to a shorter fire interval has been attributed to the cumulative combustion of the soils organic matter, litter consumption and other firerelated C inputs [26,38] and the lack of time for complete recovery between prescribed fires [39,40]. In contrast, increases in C immediately or shortly after prescribed fires, similar to the findings of a meta-analysis by Johnson and Curtis [49], have been related to the addition of necromass to the soil, or to incomplete combustion of organic matter due to low temperatures reached in the top first centimetre of mineral soil during burning [19]. ...
Prescribed burning is a tool that is frequently used for various land management objectives, mainly related to reduction of hazardous forest fuels, habitat management and ecological restoration. Given the crucial role of soil in forest ecosystem processes and functions, assessing the effects of prescribed burning on soil is particularly relevant. This study reviews research on the impacts of repeated prescribed burning on the physical, chemical and biological properties of soil. The available information shows that the effects are highly variable, rather inconsistent and generally minor for most of the soil characteristics studied, while a number of soil properties show contrasting responses. On the other hand, ecosystem characteristics, differences in fire severity, frequency of application and the cumulative effect of treatment repetition over time, have possibly made it more difficult to find a more common response in soil attributes. Our study has also revealed some limitations of previous research that may have contributed to this result, including a limited number of long-term studies, conducted at a few experimental sites, and in a limited number of forest ecosystems. Research issues concerning the effects of prescribed fire on soil are presented. The need to integrate such research into a broader interdisciplinary framework, encompassing the role of the fire regime on ecosystem functions and processes, is also highlighted.
... Prescribed burning is considered to be advantageous for forest ecosystems to promote vegetation and control pests (Biswell and Agee 1999;Alexander et al. 2017;Fuentes et al. 2018). However, it may alter the temporal dynamics of carbon (C) and nitrogen (N) pools in the forest ecosystems (Bai et al. 2015a;Karhu et al. 2015;Muqaddas et al. 2016;Merino et al. 2019;Muqaddas et al. 2019). ...
... The dynamics of C and N pools in forests after prescribed burning may be altered via various mechanisms such as C and N losses through volatilisation and mineralisation (González-Pérez et al. 2004;Prieto-Fernández et al. 2004;Huang et al. 2013;Caon et al. 2014;Karhu et al. 2015;Muqaddas et al. 2016). Releasing the inorganic C and N increases their concentrations in soils immediately after prescribed burning (Guinto et al. 1999;Prieto-Fernández et al. 2004). ...
... The practical limitation of sample collection before the prescribed burning and the absence of unburned area in the studied sites did not allow us to attribute the observed variations in labile C and N pools to the prescribed burning directly. Strong correlations among soil C and N pools and seasonal variations including air temperature have been reported and mainly attributed to the microbial activity affected by the temperature and soil moisture (Muqaddas et al. 2016). However, the lack of correlations among the soil C and N pools and climatic factors including temperature and rainfall in this study indicated that seasonal Different lowercase letters indicate significant differences among sampling seasons and plant species for that specific row at P < 0.05 effects might not be the main driving factor of the variation in labile C and N. The gradual increase in the soil labile C and N after prescribed burning has also been driven by the burninginduced factors, such as the gradual incorporation of ashes in the soil, releasing of carbohydrates from soil microorganisms and alterations in soil organic matter (Serrasolsas and Khanna 1995;Prieto-Fernández et al. 1998;Wang et al. 2012). ...
Purpose: This study aimed to understand the mechanisms of the variations in carbon (C) and nitrogen (N) pools and examine the possibility of differentiating the burning effects from seasonal and pre-existed N limitations in a native suburban forest ecosystem influenced by prescribed burning in subtropical Australia.
Methods: Soil and litterfall samples were collected from two study sites from 1 to 23 months since last burnt. Soil labile C and N pools, soil C and N isotopic compositions (δ13C and δ15N), litterfall mass production (LM), and litterfall total C, total N, δ13C and δ15N were analysed. In-situ gas exchange measurements were also conducted during dry and wet seasons for Eucalyptus baileyana and E. planchoniana.
Results: The results indicated that labile C and N pools increased within the first few months after burning, with no correlations with climatic factors. Therefore, it was possible that the increase was due to the burning induced factors such as the incorporation of ashes into the soil. The highest values of soil and litterfall δ15N, observed when the study was commenced at the experimental sites, and their high correlations with climatic factors were indicative of long-term N and water limitation. The 13C signals showed that soil N concentrations and climatic factors were also two of the main factors controlling litterfall and foliage properties mainly through the changes in photosynthetic capacity and stomatal conductance.
Conclusions: Long-term soil N availability and climatic factors were the main driving factors of C and N cycling in the studied forest sites. Further studies are needed to compare soil and litterfall properties before and after burning to profoundly understand the effects of prescribed burning on soil labile C and N variations.
... Whereas wildfires can negatively affect the biotic community (Butenko et al., 2017;Holden et al., 2013;Kuenzi et al., 2008;Prieto-Fernández et al., 1998;Rutigliano et al., 2007Rutigliano et al., , 2013 and soil organic matter (Certini et al., 2011;Hernández et al., 1997), it has been demonstrated that burning within certain prescriptions (e.g., low temperatures and high moisture content in the soil) has much milder effects (Fernandes et al., 2013;Hubbard et al., 2004;McCarthy and Brown, 2006). However, prescribed burning may be a source of damage (Fernandes et al., 2013), particularly when applied repeatedly in the same area (Eivazi and Bayan, 1996;Guinto et al., 2001;Muqaddas et al., 2016). The effects of repeated prescribed burning on the soil microbial community has so far been investigated in some detail in Australian wet sclerophyll forests (Bastias and Xu, 2006;Bastias et al., 2009;Muqaddas et al., 2015Muqaddas et al., , 2016Shen et al., 2016), US xeric oak forests (Williams et al., 2012) and savannas (Ponder et al., 2009), whereas no information on the topic is currently available for Mediterranean European forest. ...
... However, prescribed burning may be a source of damage (Fernandes et al., 2013), particularly when applied repeatedly in the same area (Eivazi and Bayan, 1996;Guinto et al., 2001;Muqaddas et al., 2016). The effects of repeated prescribed burning on the soil microbial community has so far been investigated in some detail in Australian wet sclerophyll forests (Bastias and Xu, 2006;Bastias et al., 2009;Muqaddas et al., 2015Muqaddas et al., , 2016Shen et al., 2016), US xeric oak forests (Williams et al., 2012) and savannas (Ponder et al., 2009), whereas no information on the topic is currently available for Mediterranean European forest. ...
... However, they reported a significant reduction in soil organic C content and relative abundance of Gram negative bacteria at 2-year fire intervals. Similarly, Muqaddas et al. (2015Muqaddas et al. ( , 2016 highlighted how crucial is to estimate the return time of prescribed fire (i.e., the optimum interval between successive fire treatments); based on their analysis of the effects of prescribed fire in Australian wet sclerophyllous forests, they suggested that a return time of 4 years is preferable to 2 years. Indeed, compared to untreated areas, these authors observed significant reductions in soil total C, dissolved organic C and N, inorganic N and microbial biomass when prescribed fire was applied with a return time of 2 years, whereas they did not observe significant alteration with a 4-year return time. ...
Wildfire has historically been a major disturbance in Mediterranean European ecosystems and prescribed burning is increasingly used here to mitigate possible damage and reduce hazard. This raises the issue of a possible negative impact on soil from repeated burning treatments. We investigated the effects of a single and repeated prescribed burning on total and extractable organic C, microbial biomass C, fungal mycelium, microbial activity, metabolic quotient and C mineralization rate in the fermentation layer (F-layer) and the 5-cm soil underneath of a Pinus halepensis Mill. plantation in the Cilento, Vallo di Diano e Alburni National Park, Southern Italy. Prescribed burning was sequentially applied in 2009 and 2014 and the measurements were performed during the first year following each burning treatment. The first treatment produced short-term effects on the microbial biomass and activity of the F-layer, whereas the soil layer underneath was virtually unaffected. Surprisingly, the second treatment had negligible effects on either layer, probably because of a reduction of the understory fuel load and changes in the stand structure after the first burning. Most remarkably, fire-induced changes in the soil parameters considered were generally smaller than over-time fluctuations.
... Whereas wildfires can negatively affect the biotic community ( Butenko et al., 2017;Holden et al., 2013;Kuenzi et al., 2008;PrietoFernández et al., 1998;Rutigliano et al., 2007Rutigliano et al., , 2013) and soil organic matter ( Certini et al., 2011;Hernández et al., 1997), it has been demonstrated that burning within certain prescriptions (e.g., low temperatures and high moisture content in the soil) has much milder effects ( Fernandes et al., 2013;Hubbard et al., 2004;McCarthy and Brown, 2006). However, prescribed burning may be a source of damage ( Fernandes et al., 2013), particularly when applied repeatedly in the same area ( Eivazi and Bayan, 1996;Guinto et al., 2001;Muqaddas et al., 2016). The effects of repeated prescribed burning on the soil microbial community has so far been investigated in some detail in Australian wet sclerophyll forests ( Bastias and Xu, 2006;Bastias et al., 2009;Muqaddas et al., 2015Muqaddas et al., , 2016Shen et al., 2016), US xeric oak forests ( Williams et al., 2012) and savannas ( Ponder et al., 2009), whereas no information on the topic is currently available for Mediterranean European forest. ...
... However, prescribed burning may be a source of damage ( Fernandes et al., 2013), particularly when applied repeatedly in the same area ( Eivazi and Bayan, 1996;Guinto et al., 2001;Muqaddas et al., 2016). The effects of repeated prescribed burning on the soil microbial community has so far been investigated in some detail in Australian wet sclerophyll forests ( Bastias and Xu, 2006;Bastias et al., 2009;Muqaddas et al., 2015Muqaddas et al., , 2016Shen et al., 2016), US xeric oak forests ( Williams et al., 2012) and savannas ( Ponder et al., 2009), whereas no information on the topic is currently available for Mediterranean European forest. The study aim was to evaluate the impact of a single and repeated prescribed burning on the organic C pools (total organic C, extractable organic C and microbial C) and microbial activity in the fermentation layer (F-layer = partially decomposed but recognizable organic matter; Neary et al., 2005) and the underlying 5-cm soil layer in a Pinus halepensis plantation in Southern Italy. ...
... However, they reported a significant reduction in soil organic C content and relative abundance of Gram negative bacteria at 2-year fire intervals. Similarly, Muqaddas et al. (2015Muqaddas et al. ( , 2016) highlighted how crucial is to estimate the return time of prescribed fire (i.e., the optimum interval between successive fire treatments); based on their analysis of the effects of prescribed fire in Australian wet sclerophyllous forests, they suggested that a return time of 4 years is preferable to 2 years. Indeed, compared to untreated areas, these authors observed significant reductions in soil total C, dissolved organic C and N, inorganic N and microbial biomass when prescribed fire was applied with a return time of 2 years, whereas they did not observe significant alteration with a 4-year return time. ...
Wildfires are a major environmental problem in the Mediterranean area. Prescribed burning is increasingly used throughout Europe as a practice to reduce fire risk, through dead fine fuels reduction. However, to evaluate the sustainability of this practice, potential negative effects on ecosystem components should be quantified and avoided.
In this study the effect of repeated prescribed burning on soil microbial community was assayed in a Pinus halepensis Mill. plantation of the National Park of Cilento and Vallo di Diano, treated with two consecutive prescribed burning in 2009 and 2014.
In both 2009 and 2014 burns fireline intensity and flame length never exceeded 200 kW m-1 and 0.5 m, respectively, and litter consumption was around 30 %.
Microbial biomass and activity were determined 3 hours, 1, 3 and 6 months after 2014 burn in the fermentation layer and in the 5 cm of soil beneath in plots burned twice (2009 and 2014), in plots burned only in 2009 and in unburned plots (control).
Prescribed burning did not affect soil microbial biomass in the short and medium term since no significant difference was detected between burn treatments and the control. Microbial activity showed a light decrease in the fermentation layer in plots burned twice, compared to control and 2009-burned plots, only 3 hours after 2014 burn, whereas no difference appeared later.
... Whereas wildfires can negatively affect the biotic community ( Butenko et al., 2017;Holden et al., 2013;Kuenzi et al., 2008;PrietoFernández et al., 1998;Rutigliano et al., 2007Rutigliano et al., , 2013) and soil organic matter ( Certini et al., 2011;Hernández et al., 1997), it has been demonstrated that burning within certain prescriptions (e.g., low temperatures and high moisture content in the soil) has much milder effects ( Fernandes et al., 2013;Hubbard et al., 2004;McCarthy and Brown, 2006). However, prescribed burning may be a source of damage ( Fernandes et al., 2013), particularly when applied repeatedly in the same area ( Eivazi and Bayan, 1996;Guinto et al., 2001;Muqaddas et al., 2016). The effects of repeated prescribed burning on the soil microbial community has so far been investigated in some detail in Australian wet sclerophyll forests ( Bastias and Xu, 2006;Bastias et al., 2009;Muqaddas et al., 2015Muqaddas et al., , 2016Shen et al., 2016), US xeric oak forests ( Williams et al., 2012) and savannas ( Ponder et al., 2009), whereas no information on the topic is currently available for Mediterranean European forest. ...
... However, prescribed burning may be a source of damage ( Fernandes et al., 2013), particularly when applied repeatedly in the same area ( Eivazi and Bayan, 1996;Guinto et al., 2001;Muqaddas et al., 2016). The effects of repeated prescribed burning on the soil microbial community has so far been investigated in some detail in Australian wet sclerophyll forests ( Bastias and Xu, 2006;Bastias et al., 2009;Muqaddas et al., 2015Muqaddas et al., , 2016Shen et al., 2016), US xeric oak forests ( Williams et al., 2012) and savannas ( Ponder et al., 2009), whereas no information on the topic is currently available for Mediterranean European forest. The study aim was to evaluate the impact of a single and repeated prescribed burning on the organic C pools (total organic C, extractable organic C and microbial C) and microbial activity in the fermentation layer (F-layer = partially decomposed but recognizable organic matter; Neary et al., 2005) and the underlying 5-cm soil layer in a Pinus halepensis plantation in Southern Italy. ...
... However, they reported a significant reduction in soil organic C content and relative abundance of Gram negative bacteria at 2-year fire intervals. Similarly, Muqaddas et al. (2015Muqaddas et al. ( , 2016) highlighted how crucial is to estimate the return time of prescribed fire (i.e., the optimum interval between successive fire treatments); based on their analysis of the effects of prescribed fire in Australian wet sclerophyllous forests, they suggested that a return time of 4 years is preferable to 2 years. Indeed, compared to untreated areas, these authors observed significant reductions in soil total C, dissolved organic C and N, inorganic N and microbial biomass when prescribed fire was applied with a return time of 2 years, whereas they did not observe significant alteration with a 4-year return time. ...
Monitoring ecological effects of prescribed burning on ecosystem components is a crucial step to assess the sustainability of this practice on a short, medium and long term management perspective. In Mediterranean pine forests of Europe, prescribed burning is routinely used for fire hazard abatement. Monitoring studies have been mostly focused on fire effects on the tree, but very few on other important ecosystem components such as flora, soil and fauna. Moreover, as the impact of fire can be highly variable depending on several conditions, a thorough understanding of fire effects on specific ecosystem components in their own local characteristics (e.g. target or endemic species), is mandatory.
The aim of this study was to evaluate the short and medium term effects of prescribed burning on vegetation, carabids and soil parameters in a Pinus pinea plantation of Castel Volturno Reserve (Southern Italy). Vegetation studies include pre and post-burn analysis of two topics: 1) understory plant composition; 2) wood growth and ecophysiological performance of pinus trees. The experimental design and results of the topic 2 have been submitted to another work presented at this congress (see Battipaglia et al.)
Understory plant composition, carabid populations and soil have been sampled in the same stand treated by a low intensity prescribed burning (backfire; fireline intensity < 200 kW m-1; flame length < 0.5 m).
The effect of burning on understory plant composition was evaluated in terms of floristic composition and structure by means of phytosociological and dendrometric randomly located samplings before and after 6 months of treatment. The short-time effects of prescribed fire did not affect species density and richness. Moreover, no significant difference was observed in terms of individual mortality of understory shrubs. The study of carabids have been carried out by the use of fall traps (9 cm in diameter and 11cm high) monitored for species and individual number each month in burned and unburned plots. Carabid soil communities are increasingly used to assess the status of the environment for their several adaptive characteristics to habitat types or trophic resources. Only two species are detected (Calathus montivagus, Carabus rossii) in the study site both endemic of Italy. Preliminary results showed a community rather poor in species but higher both in species and individuals in burned plots compared to unburned.
As concern soil analysis litter and fermentation layer weight was measured before and 3 hours after prescribed fire. Moreover, total microbial biomass and fungal mycelium were monitored several times since burn (3 hours; 1, 3, 6 months) in the fermentation layer and soil beneath (0-5 cm depth). Weight of fermentation layer was unaffected by prescribed fire and, generally, no negative effect was observed on total microbial biomass and fungal mycelium in fermentation layer, so too in the soil beneath, even sometimes microbial parameters increased in burned plot.
Our first results highlight the sustainability of prescribed burning in Pinus pinea forests as showed by the high resistance and resilience of analyzed components.
... However, in our study this increase was relatively short-lived, as six months after burn there was no significant difference between the burned and control stands. Some studies have shown that only very frequently burns of understory vegetation in forests might cause significant changes in soil C and N concentrations (Chowdhury et al., 2022;Muqaddas et al., 2016). Other study has also shown that a single low intensity prescribed fire may create conditions, where there will be no changes in soil C and N concentrations (Hatten et al., 2008). ...
... Within the warm season, SOC and litter matter decompose more intensely and root exudates were more enriched, that might increase soil DOC concentrations (S. . In contrast, microbial activity decreases at low temperatures, resulting in reduced decomposition processes and release of C from the soil solution (Muqaddas et al., 2016). Controversially to our findings, Zhao et al. (2012) reported that burns in fall reduced soil DOC concentrations in wetlands. ...
Dissolved organic carbon (DOC) is an important function of soil organic carbon and sensitive to environmental disturbance. Few studies have explored the variations in soil DOC dynamics and effects on soil physicochemical properties following prescribed burnings. In this study, Pinus koraiensis plantation forests in Northeast China were selected and subjected to prescribed burning in early November 2018. Soil DOC and different soil physicochemical and biological properties in the 0-10 cm and 10-20 cm soil layers were sampled six times within two years after a prescribed burning. In this study, some soil physicochemical (SOC, TN, and ST) and microbial biomass properties (MBC) recovered within two years after a prescribed burning. Compared to the unburned control stands, the post-fire soil DOC concentrations in the upper and lower soil layers increased by 16% and 12%, respectively. Soil DOC concentrations varied with sampling time, and peaked one year after the prescribed burning. Our results showed that soil chemical properties (NH4+-N and pH) rather than biological properties (microbial biomass) were the main driving factors for changes in post-fire soil DOC concentrations. Current study provides an important reference for post-fire and seasonal soil C cycling in plantation forests of Northeast China.
... Previous studies at this site have shown that prescribed burning treatments led to changes in both the composition of plant species and soil characteristics (Guinto et al., 2001;Lewis et al., 2012;Liu et al., 2013). Specifically, studies have documented that the more frequent burning (2yrB) resulted in lower soil total and labile C and N pools (Liu et al., 2013;Muqaddas et al., 2015;Muqaddas et al., 2016;Muqaddas et al., 2019). This may be in part due to long-term reductions in litterfall nutrient return associated with frequent burning. ...
... The higher C:N ratios suggest that litterfall in the 2yrB treatment will decompose and release nutrients more slowly relative to the 4yrB and NB treatments (O'Connell and Menage, 1982), thus negatively affecting C and N cycling through litterfall. This has presumably led to the lower soil C and N levels soil in 2yrB plots reported in earlier studies at the site (Liu et al., 2013;Toberman et al., 2014;Muqaddas et al., 2015;Muqaddas et al., 2016;Muqaddas et al., 2019). ...
Litterfall helps maintaining nutrient return in forest ecosystems. However, the influence of long-term
prescribed burning on the dynamics of litterfall biomass and carbon (C) and nitrogen (N) cycling is
poorly understood. A 39-year old prescribed burning field trial in a wet sclerophyll forest, southeast
Queensland, Australia, was used to investigate the interactive effects of prescribed fire regimes and temporal
variation on the quantity and quality of litterfall and C and N return. Treatments included no burning
(NB) since 1969, 2 yearly burning (2yrB; burned 19 times) and 4 yearly burning (4yrB; burned 9
times) since 1972. Litterfall was collected monthly on 32 occasions between 2011 and 2013. Significant
temporal variation was observed in monthly and annual litterfall biomass. Both burning treatments had
lower monthly inputs of total litterfall and leaf litter, mean annual cumulative litter biomass, litter C
concentrations and C return via leaf litter, compared with the NB treatment. Most significant reductions
in litter N concentrations and N return via litter were associated with 2yrB treatment. The 4yrB and the
NB treatments did not differ significantly in terms of twig biomass, litterfall C:N ratios and N return via
leaf litter. Despite both long-term prescribed burning treatments negatively impacting C return to the
soil by reducing the quantity and quality of litter inputs, previous studies at the site suggest no difference
in 0–10 cm soil organic carbon levels between the 4yrB treatment and the unburnt treatment.
Hence a longer period of prescribed burning at the 4yrB frequency is likely required before lower C return
translates to differences in ecosystem productivity in this wet sclerophyll forest ecosystem
... Prescribed burning might have long-term impacts on foliar N and δ 15 N. Nearly a decade after prescribed burnings in oak woodland and chaparral in California, foliage δ 15 N was lower than the control due to N limitation (Mnich 2014). Another example showed that foliar N concentration decreased and then increased during the samplings that occurred 1, 3 and 12 years following the prescribed burning in a scrubby flatwoods community in Florida (Schafer and Mack 2014). ...
... Litter November; summer: December, January and February; autumn: March, April and May; and winter: June, July and August availability. For example, the 2-yearly prescribed burning in a wet sclerophyll forest in Australia showed a significant decrease in labile and total N pools in the forest floor and surface soil(Muqaddas et al. 2016). ...
PurposesPrescribed burning is projected to be adopted more frequently with intensifying climate change; thus, a long-term study is necessary to understand the burning impacts on forest productivity and carbon (C) and nitrogen (N) cycling. Litter fall production rate can be used to indicate burning impacts on forest productivity, whereas N concentration, and C and N isotope composition (δ13C and δ15N) can be used to infer burning impacts on C and N cycling in plant-soil system.Materials and methodsIn this study, the impacts of low-intensity prescribed burning on litter production, N concentration, and C and N isotope compositions were continuously investigated for 6 years at five study sites in a natural eucalypt forest of subtropical Australia.Results and discussionHigher leaf litter production rate, N concentration and δ15N, and lower δ13C could be seen shortly after prescribed burning. The higher leaf litter N concentration and lower δ13C were likely due to the ease of competition for soil N and moisture from understory vegetation in the short term by prescribed burning. Leaf δ15N and N concentration were closely correlated, and seasonal changes in leaf litter production rate, δ13C and δ15N were observed. Burning season and related severity might determine the suppression degree of understory vegetation. Time since fire (TSF) was a significant impact factor influencing the litter fall production rate, N concentration, δ13C and δ15N of leaf litter fall for a decade following prescribed burning. However, monthly rainfall and temperature were less consistent in their impacts.Conclusions
Nitrogen limitation was enhanced by prescribed burning through the removal of litter and understory vegetation in the N poor forest and might be responsible for the long-term burning impacts. Low-intensity prescribed burning might have a long-lasting impact on forest litter productivity in nutrient poor forests in subtropical Australia.
... This may be due to the lower intensity of prescribed burning, where heat from the fire source did not affect the subsurface soil layer, resulting in a differential response of the STC to fire in the soil layers [41,44,47,49,50]. The changes in STC observed in this study were attributed to a single prescribed burn, and the variations in soil carbon may manifest as regular oscillations or negative effects rather than a simple return to the control level when prescribed burns occur frequently [51][52][53]. It may be that further oscillations had monitoring that occurred for a longer temporal period, and there was no comparison before the fire condition as there were no measures before the fire. ...
The mechanism through which fine root biomass affects soil carbon accumulation after prescribed burning remains unclear. In this study, the biomass of fine roots in different life forms (larch, shrub, and grass) and the total soil carbon (STC) were determined after prescribed burning. Relative to a control, the total soil carbon increased one week after the fire (11.70 mg·g⁻¹; 28.1%) and decreased after 8 months (7.33 mg·g⁻¹; 16.7%), returning to control levels 10 months post-fire. There was a reduction in the larch fine root biomass (FRB) (0.20–0.48 t·ha⁻¹; 35.3%–46.1%; these ranges represent the significant variation interval of fine root biomass after the fire across different time periods, compared to the control) but an increase in the shrub FRB (0.06–0.14 t·ha⁻¹; 101.6%–158.4%) and herb FRB (0.06–0.13 t·ha⁻¹; 591%–3200%) during the vegetation recovery process after the fire. The complementary growth of different plant life forms contributed to the changes in FRB. This also caused changes in the different life forms of FRBs’ effects on STC. Prescribed burning increased the contribution of FRB to STC. The compensatory growth of fine roots from different life forms drives the stabilization of the soil carbon pool after prescribed burning. Prescribed burning reduced the litter fuel and changed the FRB of different life forms, but it did not affect the long-term accumulation of STC.
... Prescribed burning has been widely used as a forest management tool to reduce the risk of wildfire spread (May and Attiwill 2003;Reverchon et al. 2011;Bai et al. 2012;Francos and Úbeda 2021). Prescribed burning may cause N losses through volatilization and release terrestrial carbon (C) into the atmosphere (Thonicke et al. 2010;Muqaddas et al. 2016). Acacia species can help soil nutrient recovery by biological N fixation (BNF) and increasing carbon (C) sequestration, especially in forests after prescribed burning and fire Bai et al. 2014;Witt et al. 2017;Reverchon et al. 2020). ...
Purpose
The fuel reduction prescribed burning and biochar application can have significant impacts on water and nitrogen (N) use efficiency of understory acacia species as well as soil carbon (C) and N pools in a suburban native forest subject to N deposition in Southeast Queensland, Australia.
Methods
We evaluated the impact of biochar application rates (0, 5.0 and 10.0 t biochar per hectare) and prescribed burning on soil-plant interactions in carbon (C) and N cycling in a suburban native forest in the first two years of biochar application or three and half years of the recently prescribed burning.
Results
Anthropogenic N deposition not only enhanced N losses caused by N leaching and denitrification, but also inhibited biological N fixation (BNF) by increasing N availability in forest systems. The Acacia leiocalyx with higher water use efficiency was more inclined to utilize easily available N resources (from N deposition), compared with A. disparismma. In this study, biochar application could indeed reduce N loss in forest soil and improve soil fertility by improving plant water and N use efficiency. Meanwhile, soil moisture content affected by biochar application also influenced soil N transformations by affecting soil microbial activity.
Conclusion
For urban forest soils, the high N availability caused by N deposition could inhibit the BNF in a suburban native forest ecosystem. The high-porosity physical structure of biochar applied increased the soil water content and soil N retention capacity.
... Prescribed burning has been widely used as a common forest management practice for reducing fuel load and minimizing the risk of wildfires in natural forests in Australia (Reverchon et al. 2020;Wang et al. 2020a). However, prescribed burning directly acts on the surface soil layer and leads to the depletion of soil C and N pools and a decline in soil quality (Muqaddas et al. 2016). It has been reported that fire-adapted understory legume Acacia species rapidly reestablish after fire, which contributes to C replenishment and N cycles depending either on the N fixation process that closely relies on C availability in dissolved organic C form as the energy source (Hart et al. 2005;Witt et al. 2017), or on the higher quality of litter inputs to soils derived from a higher tree cover rate (Hart et al. 2005;Coetsee et al. 2010;Bai et al. 2014). ...
Purposes
Soil labile carbon (C) and nitrogen (N) pools are vital indicators of soil fertility and soil organic matter (SOM) dynamics. We aimed to evaluate the short-term effects of biochar application on soil labile C and N pools in nutrient-deficient soil in subtropical Australia.
Materials and methods
A 9-month field study was conducted to investigate the short-term changes in soil water-extractable organic C (WEOC) and total N (WETN) as well as hot water-extractable organic C (HWEOC) and hot water-extractable total N (HWETN) in response to biochar application rates under two Acacia species (Acacia leiocalyx (A. leiocalyx) and Acacia disparrimma (A. disparrima)) and Eucalyptus psammitica (E. psammitica) in a native subtropical forest in southeast Queensland, Australia. Biochar was applied at three rates: 0 t ha⁻¹ (B0), 5 t ha⁻¹ (B5), and 10 t ha⁻¹ (B10). We collected soil samples from 0–5 cm, 5–10 cm, and 10–20 cm depth after 6 months of biochar application, and soil samples at 0–5 cm depth were also collected shortly before biochar application and after 1, 2, 3, 6, and 9 months of biochar application.
Results
Soil WEOC and WETN significantly decreased with the biochar application rate during the study period. In the 10–20 cm layer, soil WEOC, WETN, HWEOC, and HWETN under E. psammitica were significantly higher than those under the Acacia species. Sampling time also significantly affected the soil labile C and N pools, and soil WEOC and HWEOC were significantly higher in the third month after biochar application than at other sampling times, whereas soil WETN and HWETN continuously increased from the third month and peaked in the ninth month after biochar application.
Conclusions
Our results indicate that although biochar application consequently decreases labile pools on short timescales, it still highlights the potential to maintain stability of soil labile C and N pools in forest ecosystems in the short term. Our findings might further contribute to accelerating C sequestration and N cycles in low fertility soils and might ultimately be conducive to improving the adaptive capacity of vulnerable ecosystems in response to frequent prescribed burning and climate change.
... It begins to volatilize at 200 • C, and more than half of the N in organic matter is lost once the temperature exceeds 500 • C [21]. The soil N pool and availability are largely determined by the fire severity [22][23][24][25], fire frequency [26][27][28], fire type [29,30], and recovery time [31,32]. Previous studies have explored the changes that occur in the soil NH 4 + -N and NO 3 − -N contents in response to wildfire and have confirmed that wildfires induce short-term increases in the mineral N content, which subsequently returns to its pre-fire level over a period of years to decades. ...
This study investigates the evolution of soil nitrogen (N) contents and forms along a 17-year wildfire chronosequence in the Daxing’an Mountains. Surface soil and subsoil samples were collected during different recovery periods after wildfires. Then, the mineral N (i.e., NH4⁺-N and NO3⁻-N) and amino acid-N (AAN) contents in the soil extracts were measured and used to calculate the different ratios as indicators of the N forms. The results showed that the NH4⁺-N, NO3⁻-N, and AAN contents increased immediately after the wildfire. With vegetation restoration, the NH4⁺-N and NO3⁻-N contents became similar to those of unburned forests nine years and two months after the wildfire, respectively. The AAN content was mostly recovered one year post-fire. The wildfire did not lead to substantial changes in the mineral N form, but the ratio significantly increased and recovered after nine years. The soil available N form was altered by wildfires. After the wildfire, the dominant available N form changed from equivalent AAN and mineral N to a predominance of AAN in the growing season, and the predominance of AAN decreased to varying degrees in the non-growing season. With the recovery of the white birch and Dahurian larch, AAN again became the dominant N form, but the predominance of AAN was low before the freeze-up. Our study demonstrates that wildfires directly affect the soil N contents and forms, and such effects could be diminished by the restoration of the soil environment and vegetation over time.
... Prescribed burning has been widely used to reduce the risk of severe wildfire spread by managing fuel loads in the native forests of subtropical Australia. Prescribed burning volatilizes N, which increases N deficiency in the N-poor soils of this area and releases terrestrial C (Muqaddas et al. 2016). However, Acacia species can improve the soil capacities for nutrient recovery and C pool replenishment through the N fixation process and through competitive physiological traits in burned forests (Yang et al. 2009;Bai et al. 2014;Witt et al. 2017). ...
Purposes
Biochar has received widespread attention as a means for improving carbon (C) sequestration and soil fertility over the long term. However, information on its short-term effects on the soil C and nitrogen (N) pools is scarce, particularly in poor soils that are subjected to prescribed burning.
Materials and methods
In an effort to better understand the short-term effects of biochar on the soil C and N pools, a half-year field study was conducted in a suburban forest that is subjected to prescribed burning in subtropical Australia. In this experiment, biochar was applied to the soil once at rates of 0, 5 and 10 t ha⁻¹, and soil samples were collected for the top 20 cm soil profile under the canopies of leguminous Acacia leiocalyx (A. leiocalyx) and Acacia disparimma (A. disparimma) in the third month (August 2019) and the sixth month after biochar application (November 2019). At this site, we measured soil total C, total N, δ¹³C and δ¹⁵N.
Results
We observed that biochar generally impacted the soil C and N pools in the third month after biochar application: soil total C, particularly at the 0–5 cm depth, significantly decreased with increased biochar application rates. Soil C and N pools, particularly at the 10–20 cm depth, varied with sampling times, and soil total C and N under the A. leiocalyx canopy were significantly higher, while soil δ¹³C and δ¹⁵N were lower in the sixth month relative to the third month. Soil δ¹³C and δ¹⁵N were primarily linearly related to soil total C and N in the third month, while the linear relationship was closer than that between soil δ¹³C and δ¹⁵N and the labile C and N pools in the sixth month, which were regulated by biochar application rates.
Conclusions
Biochar application significantly decreased the soil C and N pools at the 0–5 cm depth in the third month after biochar application. The soil C and N pools and soil labile C and N pools were responsible for the changes in the processes of soil organic matter (SOM) turnover and N cycling that were revealed by soil δ¹³C and δ¹⁵N, and the changes were governed by the biochar application rates and the time elapsed after biochar application. The influence of understorey legume Acacia species, particularly A. leiocalyx, on N inputs and C sequestration in the poor forest soils was significantly enhanced in the sixth month after biochar application.
... Many studies (Badía et al., 2014;Bennett et al., 2014;Bird et al., 2000;Girona-García et al., 2018;Muqaddas et al., 2015;Muqaddas et al., 2016) suggested that the total soil organic carbon (TOC) would decrease after the burning due to thermal decomposition and combustion of the soils organic matter. However, in our study, the 1 cm soil exhibited an increase in TOC immediately after the burning. ...
A grassland was burned to investigate how a short prescribed fire affected soil physical and hydraulic properties, soil water balance, and emergent vegetation. Three years before the experiment at Řisuty, Czech Republic, the grassland was re-established on arable soil. At the experimental site there is a weather station and sensors measuring soil temperature and moisture at three different depths. The 5 m × 5 m burned plot was compared to a nearby unburned reference location. The loamy Cambisol soil was not water-repellent. 250 m2 of sun-dried grass was raked and burned at the burned plot. The fire lasted approximately 15-minute and reached 700 °C. Soil samples were taken immediately after the fire and weekly to monthly thereafter to quantify organic carbon content, soil structure stability, hydraulic conductivity, bulk density, and texture. According to the research results, it appears that temporary burning improved the hydraulic properties of the topsoil. The fire plot’s infiltration capacity was increased, and soil water content was higher than the control plot throughout the year, providing suitable habitat for colonizing vegetation. The results suggest that small-scale controlled biomass burning can be risk-free to the soil ecosystem and may even temporarily improve the hydraulic properties of the upper soil layer.
... soil type, vegetation cover, flammability, topography), temperature/severity reached, post-fire weather conditions and vegetation recuperation. Muqaddas et al. 178 observed that a high prescribed fire frequency (2 years) in a native Eucalyptus forest located in Australia, reduced importantly soil moisture, carbon and nitrogen content. Dissolved organic carbon, dissolved organic nitrogen and bioavailable carbon were reduced as well. ...
... Prescribed burning is used widely as a forest management technique to prepare sites for seeding or planting, reduce fuel loads and control plant disease (Muqaddas et al. 2016). Meanwhile, prescribed burning in forest management can reduce resource competition between target trees and shrubs, improve above and below-ground ecosystem structures and functions, and help maintain the biodiversity and ecological balance of forest ecosystems (Glitzenstein et al. 2012). ...
Prescribed burning is a common practice of site preparation before afforestation in subtropical forests. However, the effects of prescribed burning on carbon (C) dynamics of an ecosystem are poorly understood. Therefore, a Eucalyptus urophylla plantation (EU) and a naturally recovered shrubland (NS), each treated with prescribed burning and no burning were examined in subtropical China. Biomass of trees and shrubs in the 1st, 3nd, 4th, and 6th year after treatments were estimated by quadrat survey and allometric equations. Biomass of herbs and forest floors were estimated by harvest method. Plant biomass C storage was calculated by plant biomass multiplying by its C concentration. Soil organic C (SOC) storage in the 6th year after treatments was estimated by SOC concentration multiplying by soil bulk density and soil volumes. Tree biomass C storage was significantly higher in the burned EU (BEU) than in the unburned EU (UEU) in the 1st year after treatments, yet the difference decreased over time. Conversely, tree biomass C storage was lower in the burned NS (BNS) than in the unburned NS (UNS), although the difference was not significant. However, in the 6th year after treatments, the total plant biomass C storage was 14.56% higher in the BEU than that in the UEU, and 59.93% higher in the BNS than that in the UNS, respectively, although the significant difference was only found between UNS and BNS. In addition, neither SOC storage at 0–20 cm nor ecosystem C storage in either the EU or NS was significantly affected by prescribed burning. Prescribed burning has little impact on overall C storage of forest ecosystems, we consider that prescribed burning may be an option for forest site preparation regarding plant biomass C accumulation.
... While burning positively influences soil organic matter and nutrient availability by increasing the rate of nutrient cycling through the rapid mobilization of nutrients, frequent and inappropriate prescribed burning regimes negatively affects the functioning of many ecosystems (DeBano and Conrad, 1978;Thonicke et al., 2001;Muqaddas et al., 2016). Amongst others, studies conducted in southern African savannas by Aranibar et al. (2003), Mills and Fey (2004), Coetsee et al. (2010), Holdo et al. (2012) and Pellegrini et al. (2018) investigated the relationship between prescribed experimental fires and soil nutrients and, except for Aranibar et al. (2003), generally found that frequent burning reduced soil Carbon (C) and Nitrogen (N) with some suggesting indirect effects due to changes in woody cover. ...
Savannas make up about 20% of the global land-surface and are dependent on fires to maintain a balanced ecosystem. Fires in other fire-driven landscapes, particularly wildfires, were found to have negative effects on various soil properties. However, there is a lack of studies confirming the effect of fires on soil hydrology in African savanna soils. A long-term fire experiment in a South African savanna provided an opportunity to investigate the effect of different prescribed fire frequencies on soil properties in situ across coarse-grained granitic and fine-textured basalt-derived soils. Soil properties were compared between soils exposed to annual fires, fires every 2–4 years and where fires have been excluded for approximately 60 years. Across all three fire treatments, unsaturated hydraulic conductivity (K unsat ) was measured using a Tension Disc Infiltrometer to infer infiltration rates, saturated hydraulic conductivity (K sat ) measured with a Guelph Permeameter, soil water potential calculated using a Decagon WP4-T Dewpoint Potentiometer to infer soil water retention and soil total C and N measured using a LECO CNS TruMac Series Analyser. Our study found that K unsat is not affected by frequent annual fires which have infiltration rates similar to soils where fires have been excluded for nearly 6 decades. However, recently burnt granitic soils, i.e. three months prior, have significantly slower K unsat which were as low as <1 mm hr ⁻¹ compared to a mean K unsat of 30 mm hr ⁻¹ on annually burnt soils, alluding to short term fire impacts on soil infiltration. Hence, we believe that time following a fire plays a greater role on K unsat than fire frequency. Fires did not affect K sat within the initial 2–5 cm of the soil surface. In general, the granitic soils had faster K unsat and K sat than the basaltic soils. Soil water potential, total C and N was significantly greater in the fire exclusion sites over both parent materials. Soil water and nutrient availability is critical in a post-fire environment to facilitate vegetation recovery in African savannas. These systems are resilient to fires which do not have long-term negative impacts on soil hydrology and nutrients, but instead increases the spatio-temporal variation in soil properties necessary in maintaining savanna heterogeneity.
... This result may indicate that the water-soluble, labile C is still being degraded by the remaining active microorganisms (Choromanska & DeLuca, 2001). Furthermore, soil DOC content highly depends on the inputs by the organic layers (Muqaddas et al., 2016) so its combustion eliminates the main DOC source. Additionally, these compounds are easily leached and lost by runoff (Michalzik and Martin, 2013). ...
... abundance supports this hypothesis. Other than habitat structure, fire regime in south east Queensland eucalypt forests also influences soil properties (Muqaddas et al. 2015(Muqaddas et al. , 2016Butler et al. 2018), resulting in potential flowon effects that influence biologically available nutrients for invertebrate consumers. ...
Fire has a varied influence on plant and animal species through direct (e.g. fire‐induced mortality) and indirect (e.g. modification of habitat) effects. Our understanding of the influence of fire regime on invertebrates and their response to fire‐induced modifications to habitat is poor. We aimed to determine the response of a beetle family (Coleoptera: Cerambycidae) to varying fire treatments and hypothesised that the abundance of cerambycid beetles is influenced by fire frequency due to modifications in habitat associated with the fire treatments. Arthropods were sampled across 3 months in annually and triennially burnt areas (treatments starting in 1952 and 1973 respectively), an area unburnt since 1946, and a former unburnt treatment, burnt by wildfire in 2006. Eleven different cerambycid taxa were collected using flight intercept panel traps, dominated by three species (Ipomoria tillides, Adrium sp. and Bethelium signiferum) which made up 99% of individuals collected. Over the sampling period the long unburnt treatment had significantly lower species richness than the triennial and wildfire treatments. Cerambycid abundance was significantly higher in the triennially burnt treatment than in all other fire treatments. Ipomoria tillides was more abundant in both frequently burnt treatments, Adrium sp. was more common in triennially burnt areas, whereas B. signiferum, was more common in the wildfire affected treatment. Some, but not all, cerambycid beetles were more common in areas with a more open understorey (i.e. resulting from frequent burning), and lower tree basal area, as this likely influences their ability to fly easily between food sources. Cerambycid abundance was positively related to the volume of coarse woody debris and healthy tree crowns. Cerambycid beetles were clearly influenced by historic fire regime, suggesting that changes in fire regime can potentially have a profound influence on arthropod assemblages, and subsequent influences on ecosystem processes, which are currently poorly understood.
... Some studies have demonstrated important alterations in P cycling in prescribed burning of higher intensity and severity or frequency than those recorded in the present study (Alcañiz et al., 2016;Ferreira et al., 2016;Muqaddas et al., 2016;Santín et al., 2018;García-Oliva et al., 2018). In comparison with these studies, the present study focused on prescribed burning of low-moderate intensity, carried out under conditions of high levels of soil moisture, revealed moderate perturbations in the P cycling (partial losses of organic P in the soil organic layer) that may be counteracted in the medium term. ...
Various different factors have led to the accumulation of biomass in forest soils in the Mediterranean-climate region in the last few decades, thus exacerbating the effects of wildfires. Although prescribed burning is used to decrease the fuel load and reduce the currency of mega-wildfires, the impacts on soil organic matter (SOM) and nutrient cycling, and therefore on forest ecosystem sustainability, are uncertain. The present study was designed to cover a range of conditions and therefore to assess the variability in the responses in similar geographical areas. Three prescribed burning treatments producing different levels of soil burn severity were conducted in two different types of forests (Pinus nigra and Pinus pinaster) and one (previously treated by prescribed burning) shrubland ecosystem (Cytisus oromediterraneus), all characterized by different fuel loads and depths of soil organic layer, in Central Spain. After the treatments, the SOM content, its thermal properties, and the distribution of Phosphorus (P) forms (³¹P NMR spectroscopy) were measured in the soil organic layer and mineral soils (0–2 cm depth), and the results were related to the temperatures reached. The prescribed burning les to low-moderate perturbations in SOM quality and Carbon (C) and P dynamics. The organic P, which in the unburnt plots represented 70% of the extractable P, was greatly depleted (by 56 and 95% with respect the initials values). This effect was concurrent with decreases in the most thermolabile SOM fractions, suggesting that organic P is readily mineralized, even at relatively low temperatures. Release of large amounts of soluble orthophosphate may occur when the prescribed burning leads to a high level of soil burn severity. The findings show that prescribed burning treatments should be planned carefully in order to prevent long-term perturbation of C and P cycling.
... Martínez,et al.,Contenido de nitrógeno en regosoles… 276 Actualmente, los incendios forestales son los principales causantes del disturbio natural, y sus efectos en el ciclo de nitrógeno son importantes, porque es un elemento fundamental para mantener los ecosistemas terrestres (Fernández et al., 2017). Muqaddas et al. (2016) citan que las quemas prescritas de baja intensidad aumentan las cantidades de nitrógeno; sin embargo, en aplicaciones repetidas causan pérdidas en sus reservorios. En zonas mediterráneas, la quema prescrita no perjudica la naturaleza del suelo para uso agrícola (Montoya et al., 2014). ...
Las actividades antropogénicas han sido factor de la degradación de los recursos naturales, por lo que se han implementado técnicas mecánicas y naturales como el rodillo aireador y el fuego, para disminuir su impacto. Se evaluó el contenido del nitrógeno total en un suelo Regosol presente en el Desierto Chihuahuense, con vegetación de matorral desértico micrófilo (MDM) y matorral desértico rosetófilo (MDR), bajo tratamiento de manejo con rodillo aireador en tres fechas diferentes: 2004 (RA-04), 2008 (RA-08) y 2011 (RA-11); además de un área incendiada en 2011 (IN-11) y una testigo (T). En cada sitio se recolectaron cuatro muestras compuestas de suelo en profundidades de 0-15 y 15.1-30 cm, para un total de 80, las cuales se analizaron por el método Kjeldahl. Los contenidos de nitrógeno, en promedio, en el MDM fueron: T= 0.174 %, RA-04= 0.087 %, RA-08= 0.080 %, RA-11= 0.261 % e IN-11= 0.195 %; mientras que para el MDR se obtuvo T= 0.075 %, RA-04= 0.125 %, RA-08=0.082 %, RA-11= 0.170 % e IN-11= 0.178 %. Con base en el análisis de varianza hubo diferencias (p≤0.05) por tipo de vegetación y tratamiento, no se observó un efecto por profundidad. Los valores fueron de clasificación baja (MDM RA-08, 15.1-30 cm = 0.051 %) a muy alta (MDM RA-11, 0-15 cm = 0.309 %). En ambos, los contenidos de nitrógeno total variaron, considerablemente, después de los tratamientos mecánicos, dado que el Nt aumenta o disminuye, en relación al tratamiento aplicado y al tipo de vegetación.
... This result may indicate that the water-soluble, labile C is still being degraded by the remaining active microorganisms (Choromanska and DeLuca, 2001). Furthermore, soil DOC content highly depends on the inputs by the organic layers (Muqaddas et al., 2016) so its combustion eliminates the main DOC source. Additionally, these compounds are easily leached and lost by runoff (Michalzik and Martin, 2013). ...
Prescribed burning has been readopted in the last decade in the Central Pyrenees to stop the regression of subalpine grasslands in favour of shrublands, dominated among others by Echinospartum horridum (Vahl) Rothm. Nevertheless, the effect of this practice on soil properties is uncertain. The aim of this work was to analyse the effects of these burnings on topsoil organic matter and biological properties. Soil sampling was carried out in an autumnal prescribed fire in Buisán (NE-Spain, November 2015). Topsoil was sampled at 0–1 cm, 1–2 cm and 2–3 cm depth in triplicate just before (U), ~ 1 h (B0), 6 months (B6) and 12 months (B12) after burning. We analysed soil total organic C (TOC), total nitrogen (TN), microbial biomass C (Cmic), soil respiration (SR) and β-D-glucosidase activity. A maximum temperature of 438 °C was recorded at soil surface while at 1 cm depth only 31 °C were reached. Burning significantly decreased TOC (− 52%), TN (− 44%), Cmic (− 57%), SR (− 72%) and β-D-glucosidase (− 66%) at 0–1 cm depth while SR was also reduced (− 45%) at 1–2 cm depth. In B6 and B12, no significant changes in these properties were observed as compared to B0. It can be concluded that the impact of prescribed burning has been significant and sustained over time, although limited to the first two topsoil centimetres.
The iconic sand dune systems of Minjerribah (North Stradbroke Island), in southeastern Queensland, Australia, host numerous lakes and swamps containing organic‐rich sediment deposits that record changes in climate, fire and surrounding vegetation. Palaeoenvironmental reconstructions from individual locations can provide insights into changes in the environment, but determining the regional extent of these changes is seldom possible from a single site. Multi‐site compilations help elucidate the geographical nature of environmental changes and determine if they are driven by local or regional forces. Here, a synthesis of palynological records from six Minjerribah wetlands using a muti‐tiered Monte Carlo empirical orthogonal function (EOF) analysis allows island‐wide patterns of vegetation change to be identified. Coherent changes in vegetation were recorded, with first‐order changes (EOF1) indicating a long‐term shift in vegetation composition from closed forests towards woodland and heath vegetation. A compilation of macroscopic and microscopic charcoal from the same sites shares coherent patterns of change with a rainfall record from the island, suggesting that regional fire occurrence between 7000 and 2000 cal a bp was driven primarily by long‐term variations in rainfall and its influence on biomass. Comparison with fire activity, rainfall, sedimentary carbon, nitrogen and dust records from Minjerribah suggests that regional vegetation changes occur primarily in response to long‐term changes in nutrients and increasing rainfall variability. This analysis highlights the multi‐millennial connection between vegetation composition, climate, nutrients and fire occurrence across the Holocene in subtropical environments.
The objective of this study was to evaluate the effects of wildfire on the adsorption-desorption of soil free amino acids in a Dahurian larch forest in Northeast China. The study examined the adsorption and desorption of glutamic acid (Glu), glycine (Gly), and lysine (Lys) using the batch equilibrium method in two soil depths-surface soil (0–5 cm) and subsurface soil (5–10 cm)-under unburned (UB) and heavily burned (HB) conditions. Regardless of wildfire occurrence, the adsorption and desorption curves at the same exogenous concentration were determined by the types of the amino acid. Adsorption decreased in the order Lys > Gly > Glu, and desorption decreased in the order Lys > Glu > Gly. Five years after the wildfire, the adsorption of the three amino acids increased, but surface Lys adsorption decreased. An increase in the amount of clay was beneficial for the adsorption of Glu and Lys, and an increase in the amount of free iron oxide (Fed) promoted the adsorption of Gly. Wildfire also promoted the desorption of Gly caused by decreased soil organic matter (SOM) and inhibited the desorption of Lys and subsurface Glu, which were the combined results of these three changes in Fed, amorphous iron oxides (Feox) and free aluminum oxide (Ald). Overall, 5 years after the wildfire, the fixation and re-release of the three free amino acids were still affected by fire disturbance in the cold temperate coniferous forest of the Daxing’an Mountains.
Ecosystems managed with contrasting fire regimes provide insight into the responses of vegetation and soil. Heathland, woodland and forest ecosystems along a gradient of resource availability were burnt over four decades in approximately 3‐ or 5‐year intervals or were unburnt for 45–47 years (heathland, woodland), or experienced infrequent wildfires (forest: 14 years since the last fire). We hypothesized that, relative to unburnt or infrequent fires, frequent burning would favour herbaceous species over woody species and resprouting over obligate seeder species, and reduce understorey vegetation height, and topsoil carbon and nitrogen content. Our hypothesis was partially supported in that herbaceous plant density was higher in frequently burnt vegetation; however, woody plant density was also higher in frequently burnt areas relative to unburnt/infrequently burnt areas, across all ecosystems. In heathland, omission of frequent fire resulted in the dominance of fern Gleichenia dicarpa and subsequent competitive exclusion of understorey species and lower species diversity. As hypothesized, frequent burning in woodland and forest increased the density of facultative resprouters and significantly reduced soil organic carbon levels relative to unburnt sites. Our findings confirm that regular burning conserves understorey diversity and maintains an understorey of lower statured herbaceous plants, although demonstrates the potential trade‐off of frequent burning with lower topsoil carbon levels in the woodland and forest. Some ecosystem specific responses to varied fire frequencies were observed, reflecting differences in species composition and fire response traits between ecosystems. Overall, unburnt vegetation resulted in the dominance of some species over others and the different vegetation types were able to withstand relatively high‐frequency fire without the loss of biodiversity, mainly due to high environmental productivity and short juvenile periods.
Fire is one of the main disturbances in the world's forested ecosystems and its impacts are projected to increase in many regions due to global change. Fire impacts have been studied for decades, but integrative assessments of its effects on multiple ecosystem services (ES) across scales are rare. We thus conducted a global analysis of persistent (>1yr.) fire effects on eight ES reported over the last 30 years, evaluating qualitative and quantitative information from 207 peer-reviewed studies. Significant effects were predominantly positive for 'water provision' and negative for 'water quality', 'climate regulation' and 'erosion control'. For 'food provision' and 'soil fertility' no overall significant effects emerged. For 'recreation' or 'pollination', data was insufficient. Significant effects were generally short-lived (1-2yr.) and were more common after wildfires than after prescribed burns. These overall findings, however, are dominated by data from a few countries/biomes and short timescales, highlighting the need for future studies focusing on underrepresented regions, biomes, timescales and ES. In a nutshell • Fire is a major disturbance in many regions, but its wider effects on ecosystem services remain poorly evaluated. • We conducted a systematic review of 30 years of literature on environmental effects of forest fires, examining 207 studies that allowed assessing eight major ecosystems services. • Effects were significantly positive for 'water provision' and negative for 'water quality', 'climate regulation' and 'erosion control' and non-significant for 'food provision' and 'soil fertility'. • Negative effects were more dominant after wildfires than after prescribed burns, and, generally, effects were short-lived (1-2yr.). • Key gaps are the lack of data for some regions and biomes (e.g. tropical forests) and for long-term impacts (>10yr.).
Changes in fire frequency from historical norms are becoming more frequent due to both changes in management and climate change factors. There is uncertainty about whether increasing fire frequency will lead to decreased carbon pools due to shorter inter-fire recovery periods, or increased carbon pools due to lowered fire intensity due to lighter fuel loads. Additionally, data are needed to determine whether plant and soil carbon pools respond similarly and whether ecosystem responses are consistent across environmental gradients that can affect fire intensity, such as soil moisture. We measured soil and vegetation carbon pools and fluxes at sites that had experienced different experimental burn treatments over the previous 8 years and across a range of soil moisture in a longleaf pine (Pinus palustris) ecosystem in North Carolina, USA. We found that increasing fire frequency, assessed by either the number of days since a previous fire or the number of fires a plot had experienced over the previous 8 years, significantly reduced carbon stocks in the litter pool and soil carbon pool and reduced the productivity of understory plants. Total carbon stocks also significantly declined, and there was a marginally significant shift away from soil carbon and toward tree carbon as being the dominant carbon pool in the system with increasing fire. None of the results showed any interaction with soil moisture, suggesting that in this landscape, fire effects are consistent across an important environmental gradient. Over the timeframe of this study, management that increases prescribed fire frequency appears to reduce carbon storage.
Litterfall helps maintaining nutrient return in forest ecosystems. However, the influence of long-term prescribed burning on the dynamics of litterfall biomass and carbon (C) and nitrogen (N) cycling is poorly understood. A 39-year old prescribed burning field trial in a wet sclerophyll forest, southeast Queensland, Australia, was used to investigate the interactive effects of prescribed fire regimes and temporal variation on the quantity and quality of litterfall and C and N return. Treatments included no burning (NB) since 1969, 2 yearly burning (2yrB; burned 19 times) and 4 yearly burning (4yrB; burned 9 times) since 1972. Litterfall was collected monthly on 32 occasions between 2011 and 2013. Significant temporal variation was observed in monthly and annual litterfall biomass. Both burning treatments had lower monthly inputs of total litterfall and leaf litter, mean annual cumulative litter biomass, litter C concentrations and C return via leaf litter, compared with the NB treatment. Most significant reductions in litter N concentrations and N return via litter were associated with 2yrB treatment. The 4yrB and the NB treatments did not differ significantly in terms of twig biomass, litterfall C:N ratios and N return via leaf litter. Despite both long-term prescribed burning treatments negatively impacting C return to the soil by reducing the quantity and quality of litter inputs, previous studies at the site suggest no difference in 0-10 cm soil organic carbon levels between the 4yrB treatment and the unburnt treatment. Hence a longer period of prescribed burning at the 4yrB frequency is likely required before lower C return translates to differences in ecosystem productivity in this wet sclerophyll forest ecosystem. The 2yrB can potentially alter forest C and N cycling and net primary productivity, but these alterations are unlikely to be detected through short-term studies.
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.
A variety of physical and chemical techniques are used to fractionate soil organic matter, but detailed comparisons of the different approaches and tests of how separation methods influence the properties of isolated organic matter pools are lacking. In this case study based on A horizon samples of 2 California coniferous forests soils, we 1) evaluate the effects of root removal and ultrasonic dispersion on the properties of the <2 g cm ⁻³ light fraction and 2) compare the properties of fractions obtained by sequential density separations of ultrasonically treated soil with those obtained by density followed by acid/base hydrolysis (Trumbore et al. 1996).
A root-removal effort based on hand-picking visible roots reduced the radiocarbon content and increased the estimated turnover time of the light fraction by roughly 12%. Root-removal protocols that vary between investigators thus can potentially confound variability in carbon cycling for this fraction caused by environmental factors, such as climate. Ultrasonic dispersion did not have a clear effect on the light fraction C and N content or isotopic signature, but led to a decrease in the % C and C/N of the recovered heavy fractions, and losses of 12–19% of the total soil C to the sodium metatungstate density solution.
Sequentially isolated density fractions clearly differed in mineralogy and organic matter chemistry, but natural-abundance ¹⁴ C analyses indicated that distinct mineral phases did not correspond to unique C-turnover pools. Density fractions containing kaolinite group minerals alone and in combination with hydroxy-interlayered vermiculite were found to harbor both fast and slow cycling carbon. In contrast, severe chemical treatment isolated a carbon pool with the lowest overall ¹⁴ C content and longest inferred mean turnover time. Overall, our results show that care must be taken when relying on physical (density) separation to isolate soil fractions with different dynamics, as the details of treatment will influence the results.
We examined the cumulative effects of 20 years of two-year interval prescription burning on available nitrogen (N) and total N and phosphorus (P) pools in the upper 15 cm of mineral soil of a southwestern ponderosa pine (Pinus ponderosa Dougl. ex Laws.) forest over a complete two-year burn cycle. Repeated burning reduced anaerobically mineralizable N up to 25%. However, burned and control plots had similar monthly ammonium and nitrate pool sizes in the mineral soil during both years of the two-year burn cycle. Mineral soil total N in the upper 15 cm was reduced by 110 kg N/ha (about a 7% reduction) after 20 years of prescription burning at this site. This estimate, coupled with a calculated 470 kg/ha loss of N from the forest floor, indicates repeated burning has substantially depleted soil N stocks at this site. In contrast to N, mineral soil total P in burned plots was similar to control plots. Our results suggest that repeated prescription burning at two-year intervals may have deleterious long-term effects on N cycling in southwestern ponderosa pine forests.
Recent patterns of prolonged regional drought in southern boreal forests of the Great Lakes region, USA suggest that the ecological effects of disturbance by wildfire may become increasingly severe. Losses of forest soil organic matter (SOM) during fire can limit soil nutrient availability and forest regeneration. These processes are also influenced by the composition of post-fire SOM. We sampled the forest floor layer (i.e., full organic horizon) and 0–10 cm mineral soil from stands dominated by Coniferous (Pinus banksiana Lamb.) or Deciduous (Populus tremuloides Michx.) species 1–2 months after the 2011 Pagami Creek wildfire in northern Minnesota. We used solid-state 13C NMR to characterize SOM composition across a gradient of fire severity in both forest cover types. SOM composition was affected by fire, even when no statistically significant losses of total C stocks were evident. The most pronounced differences in SOM composition between burned and unburned reference areas occurred in the forest floor for both cover types. Carbohydrate stocks in forest floor and mineral horizons decreased with severity level in both cover types, whereas pyrogenic C (PyC) stocks increased with severity in the Coniferous forest floor and decreased in only the highest severity level in Deciduous forest floor. Loss of carbohydrate and lignin pools contributed to a decreased SOM stability index and increased decomposition index. Our results suggest that increases in fire severity expected to occur under future climate scenarios may lead to changes in SOM composition and dynamics with consequences for post-fire forest recovery and C uptake.
The Australian Government acting through the Bureau of Rural Sciences has exercised due care and skill in the preparation and compilation of the information and data set out in this publication. Notwithstanding, the Bureau of Rural Sciences, its employees and advisers disclaim all liability, including liability for negligence, for any loss, damage, injury, expense or cost incurred by any person as a result of accessing, using or relying upon any of the information or data set out in this publication to the maximum extent permitted by law.
The objective of this work was to evaluate the distribution pattern and composition of soil organic matter (SOM) and its physical pools of Leptosols periodically affected by fire over the last 100 years in South Brazil. Soil samples at 0-5, 5-10, and 10-15 cm depths were collected from the following environments: native pasture without burning in the last year and grazed with 0.5 livestock per hectare per year (1NB); native pasture without burning in the last 23 years and grazed with 2.0 livestock per hectare per year (23NB); and an Araucaria forest (AF). Physical fractionation was performed with the 0-5 and 5-10 cm soil layers. Soil C and N stocks were determined in the three depths and in the physical pools, and organic matter was characterized by infrared spectroscopy and thermogravimetry. The largest C stocks in all depths and physical pools were found under the AF. The 23NB environment showed the lowest soil C and N stocks at the 5-15 cm depth, which was related to the end of burning and to the higher grazing intensity. The SOM of the occluded light fraction showed a greater chemical recalcitrance in 1NB than in 23NB. Annual pasture burning does not affect soil C stocks up to 15 cm of depth.
Traps were used to quantify charcoal production and transport during three experimental forest fires in Boreal Scandinavia. The traps were spatially arranged to collect charcoal particles inside burn areas, and outside burn areas at different distances (0.1–100 m) from the fire edge. The number of inside and outside traps was 280 and 424, respectively. Trap area was 48 cm2. After the burn, trap content was sorted and sieved in two size-classes of charcoal particles, namely small (0.5–2.0 mm) and large (. 2.0 mm), and number and mass of particles were determined. The production and distribution of charcoal were highly variable at fine spatial scales inside burn areas. On average, inside traps contained 12.1 small and 10.1 large particles, and the average charcoal mass was 0.112 g per trap (corresponding to 235 kg ha-1). The largest size-class made up 94% of the mass. Outside traps contained 0.3 small and 0.1 large particles per trap, and 45% of the outside particles were distributed, 1 m from the fire edge. It is concluded that the occurrence of macroscopic charcoal ($ 0.5 mm) in forest soils provides a solid evidence for local fire influence, and that the presence of large charcoal particles can be used to distinguish between fire-prone and fire-free areas with high spatial precision. Absence of large particles must, however, be more carefully interpreted as 14% of the inside traps lacked macroscopic charcoal. We argue that the charcoal in Boreal forest soils should be less persistent than previously suggested because documented fire-return intervals result in an unrealistic charcoal accumulation presupposing high persistence.
AimsNatural secondary forest (NSF) and larch plantation are two of the predominant forest types in Northeast China. However, how the two types of forests compare in sustaining soil quality is not well understood. This study was conducted to determine how natural secondary forest and larch plantation would differ in soil microbial biomass and soil organic matter quality.Methods
Microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), soil organic carbon (SOC) and total nitrogen (TN) in the 0- to 15-cm and 15- to 30-cm soil layers were investigated by making chemical and biological measurements in the montane region of eastern Liaoning Province, Northeast China, during the growing season of 2008 in stands of NSF and Larix olgensis plantation (LOP).Important FindingsWe found that soil MBC and MBN were significantly lower in the LOP than in the NSF. Both MBC and MBN declined significantly with increasing soil depth in the two types of stands. The ratios of MBC to SOC (MBC/SOC) and MBN to TN (MBN/TN) were also significantly lower in the LOP than in the NSF. Moreover, the values of MBC, MBC/SOC, and MBN/TN significantly varied with time and followed a similar pattern during the growing season, all with an apparent peak in summer. Our results indicate that NSF is better in sustaining soil microbial biomass and nutrients than larch plantation in the temperate Northeast China. This calls for cautions in large-scale conversions of the native forests to coniferous plantations as a forest management practice on concerns of sustaining soil productivity.
We evaluated the importance of dissolved organic matter as a vehicle for the movement of N and P from the canopy and the forest floor into the mineral soil of a deciduous forest. We also examined the origin and nature of dissolved organic matter from the forest floor to see whether it was simply soluble plant material or highly humified matter. The average annual output from the forest floor in the form of dissolved organic matter was 18, 28, and 14% of the input in solid litterfall for C, N, and P, respectively. In throughfall, about half of the dissolved N and P was organic. But, in solution percolating from the forest floor, 94% of the N and 64% of the P was organic. Leaching from the forest floor was not a source of inorganic N and P for the mineral soil. Instead, the forest floor was a sink for the removal of these inorganic nutrients delivered in throughfall. Microbial immobilization was the most likely explanation for much of the inorganic nutrient removal. In contrast, the forest floor was an abundant contributor of N and P to the mineral soil in the form of dissolved, and possibly particulate, organic matter. Much of the dissolved organic matter entering the A horizon originated from the upper (Oa and Oe horizon) forest floor, but it was modified in several respects compared to the original soluble material. The solution percolating from the forest floor over most of the year was much richer in nitrogen, contained a much larger proportion of hydrophilic acids, and contained a much smaller proportion of carbohydrate-rich hydrophilic neutrals, than did the original water- extractable material in autumn litter. However, the fresh autumn litter did contain a similar proportion of soluble hydrophobic acids that resembled dissolved humic substances in several respects. Most of the flux of nitrogen from the forest floor to the A horizon was carried by humic substances and highly colored hydrophilic acids.
We extracted light-fraction material densimetrically in Nal solution (specific gravity 1.65 g/cm3) from root-free soil samples from a forested site in the Oregon Cascade Mountains. We chose extraction at this density because it excluded most of the organomineral particles from the light fraction. Major components identifiable from scanning electron micrographs were dead root fragments, hyphae, charcoal, and pumice-all with adsorbed or entrapped colloidal particles. Total soil carbon (C) and nitrogen (N) at the site averaged 145 and 7.4 megagrams per hectare, respectively, to a depth of 83 centimeters. Light-fraction material accounted for 53 percent of the total C and 45 percent of the total N in the 0- to 3-cm layer; these proportions decreased abruptly in the next layer and then more gradually over the remainder of the 83-cm profile. Amounts of light-fraction material increased by 50 to 100 percent from early spring to summer and then peaked again in the fall. This large seasonal fluctuation indicates that the light fraction provides an important labile reservoir of C and nutrient elements in the forest ecosystem.
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Wildfires affect soil organic matter (SOM), mainly resulting in losses of the most labile fractions (in particular carbohydrates), an increased abundance of recalcitrant fractions and, specifically, an increase in SOM aromaticity. Most of these effects have been studied in laboratory experiments: under field conditions, post-fire recovery of the vegetation must be taken into account, for it results in new and fresh inputs of organic matter to the soil. Thus the short-term effects of wildfires on SOM biochemical characteristics could be of little relevance in the medium or long term. We tested this hypothesis in the Valencia region (E Spain), in very healthy shrublands, never cropped, and which have been diversely affected by wildfires in recent decades (either 0, 1 or 2 wildfires). The study aimed at a quantitative description of SOM recalcitrance. Soil samples (uppermost 5 cm) were submitted to a four-step chemical fractionation, consisting of an extraction with dilute K2SO4 solution, and two consecutive hydrolyses, first with H2SO4 2.5 M and next with 72% H2SO4, further diluted down to 1 M. The unhydrolysed residue was taken as the recalcitrant fraction, and submitted to a further chemical attack with H2O2, to obtain the refractory fraction. Wildfires dropped both total OC and N in soil, and increased the fraction of total C and (somewhat less clearly), the total N found in both recalcitrant and refractory fractions. Carbohydrates accounted for about 20% of total OC, irrespective of the number of fires. Carbohydrates are selectively lost as a consequence of thermal shock during wildfires; thus their recovery in burned soils is an indicator of the post-fire restoration of the C cycle. The effects of wildfires are shown in the relationship between several parameters (cellulose to total carbohydrates ratio, aromatic extractable C, etc.) and total OC in the horizon, which suffer shifts as a consequence of the first wildfire, and disappear after the second. Overall, our dataset show that in burned plots the biochemistry of SOM has apparently recovered many features of the unburned plots, but a long-term effect of wildfires is still detectable in the relative abundance of recalcitrant or refractory forms. We did not detect increased aromaticity either in the overall SOM (by 13C NMR analysis) or in the extractable or hydrolysable fractions (either by absorption at 280 nm or by analysis of phenolic compounds), a fact that suggests that the increased SOM recalcitrance results from an increased abundance of condensed forms, not necessarily linked to an increase in aromatic C.
The Australian Soil Classification provides a framework for organising knowledge about Australian soils by allocating soils to classes via a key. Since its publication in 1996, this book has been widely adopted and formally endorsed as the official national system. It has provided a means of communication among scientists and land managers and has proven to be of particular value in land resource survey and research programs, environmental studies and education. Classification is a basic requirement of all science and needs to be periodically revised as knowledge increases. This Second Edition of The Australian Soil Classification includes updates from a working group of the National Committee on Soil and Terrain (NCST), especially in regards to new knowledge about acid sulfate soils (sulfidic materials). Modifications include expanding the classification to incorporate different kinds of sulfidic materials, the introduction of subaqueous soils as well as new Vertosol subgroups, new Hydrosol family criteria and the consistent use of the term reticulate. All soil orders except for Ferrosols and Sodosols are affected by the changes.
In the next decades, the influence of wildfires in controlling the cycling and composition of soil organic matter (SOM) globally and in the Western US is expected to grow. While the impact of fires on bulk SOM has been extensively studied, the extent at which heating of soil affects the soluble component of SOM remains unclear. Here, we investigated the thermal transformations of water-extractable organic matter (WEOM) by examining the changes in the distribution of carbon (C) functional groups in WEOM from soils heated at low and intermediate temperatures. WEOM (<0.7 µm particle size) was extracted from topsoils (0-5 cm depth) of five soil series formed from a non-glaciated granitic bedrock and sampled along a Sierra Nevada climosequence. Soils were heated in a muffle furnace at 150 oC, 250 oC, and 350 oC for 1 hour. The extracted solution was analyzed for WEOM aromaticity, mean molecular weight, organic C (OC) concentration, and major structural components by employing optical spectrophotometry and liquid-state 1H-NMR spectroscopy. At 150 oC and 250 oC, OC concentrations increased relative to the thermally unaltered samples, with losses of oxygenated functional C groups and enrichment of aliphatic C structures observed at 250 oC. Conversely, OC concentration and mean molecular weight decreased as heating increased from 250 oC to 350 oC, whereas WEOC became more enriched in aromatic C structures. Our results suggest that low and intermediate fire intensities significantly alter the nature of dissolved organic matter exported from soils to rivers in the Sierra Nevada and beyond.
Wildfires and prescribed burning can affect both the quality and the quantity of organic matter in soils. In this study, we investigated qualitative and quantitative changes of soil humic substances in two different soils (an Entisol from a paddy field and an Inceptisol from a cedar forest) under several controlled heating conditions. Soil samples were heated in a muffle furnace at 200, 250, or 300°C for 1, 3, 5, or 12h. The humic acid and fulvic acid contents of the soil samples prior to and after heating were determined. The degree of darkness, elemental composition, carbon and nitrogen stable isotope ratios, (13)C nuclear magnetic resonance spectra, and X-ray diffraction patterns of humic acids extracted from the soils before and after heating were measured. The proportion of humic acids in total carbon decreased with increasing heating time at high temperature (300°C), but increased with increasing heating time at ≤250°C. The degree of darkness of the humic acids increased with increasing heating time and temperature. During darkening, the H/C atomic ratios, the proportion of aromatic C, and the carbon and nitrogen stable isotope ratios increased, whereas the proportions of alkyl C and O-alkyl C decreased. X-ray diffraction analysis verified that a stacking nanostructure developed by heating. Changes in the chemical structure of the humic acids from the heated soils depended on the type of soil. The major structural components of the humic acids from the heated Entisol were aromatic C and carboxylic C, whereas aliphatic C, aromatic C, and carboxylic C structural components were found in the humic acids from the heated Inceptisol. These results suggest that the heat-induced changes in the chemical structure of the humic acids depended on the source plant.
Prescribed fire is one of the most widely-used management tools for reducing fuel loads in managed forests. However the long-term effects of repeated prescribed fires on soil carbon (C) and nitrogen (N) pools are poorly understood. This study aimed to investigate how different fire frequency regimes influence C and N pools in the surface soils (0-10cm). A prescribed fire field experiment in a wet sclerophyll forest established in 1972 in southeast Queensland was used in this study. The fire frequency regimes included long unburnt (NB), burnt every 2years (2yrB) and burnt every 4years (4yrB), with four replications. Compared with the NB treatment, the 2yrB treatment lowered soil total C by 44%, total N by 54%, HCl hydrolysable C and N by 48% and 59%, KMnO4 oxidizable C by 81%, microbial biomass C and N by 42% and 33%, cumulative CO2-C by 28%, NaOCl-non-oxidizable C and N by 41% and 51%, and charcoal-C by 17%, respectively. The 4yrB and NB treatments showed no significant differences for these soil C and N pools. All soil labile, biologically active and recalcitrant and total C and N pools were correlated positively with each other and with soil moisture content, but negatively correlated with soil pH. The C:N ratios of different C and N pools were greater in the burned treatments than in the NB treatments. This study has highlighted that the prescribed burning at four year interval is a more sustainable management practice for this subtropical forest ecosystem.
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Thinning and prescribed fire are common management tools used to eliminate thick fuel loads that could otherwise facilitate and encourage a more severe catastrophic wildfire. The objective of this study was to quantify the lasting effects of prescribed fire on forest floor and soil nutrients approximately 9 yr after a burn occurred near Truckee, CA. The study site includes a prescribed fire following various harvest and understory removal treatments: whole-tree thinning, cut-to-length thinning, and no thinning. Data were collected before, immediately after, and 9 yr later following a prescribed burn. All forest floor and soil samples were analyzed for nutrients (O horizon: total N; mineral soil: total N, total C, mineral N). Fuel reductions were evident 9 yr after the fire in the burned plots. No significant changes in total C or total N in surface (0-20-cm) mineral soils occurred during the 9-yr period. Mineral N concentrations in surface soils were greater in unburned than in burned cut-to- length thinning treatments after 9 yr. These differences were attributed to N inputs from decomposing slash and to the reduction in the biomass of N2 fixers by burning. © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA All rights reserved.
We used a long‐term fire experiment in south‐east Queensland, Australia, to determine the effects of frequent prescribed burning and fire exclusion on understorey vegetation (Eucalyptus pilularis forest. Our study provided a point in time assessment of the standing vegetation and soil‐stored vegetation at two experimental sites with treatments of biennial burning, quadrennial burning since 1971–1972 and no burning since 1969. Vegetation composition, density and richness of certain plant groups in the standing and soil‐stored vegetation were influenced by fire treatments. The density of resprouting plants Document Type: Research Article DOI: http://dx.doi.org/10.1111/j.1442-9993.2011.02337.x Affiliations: 1: Sunshine Coast Regional Council, Nambour 2: Environmental Futures Centre, Griffith University, Gold Coast Campus, Gold Coast Publication date: November 1, 2012 (document).ready(function() { var shortdescription = (".originaldescription").text().replace(/\\&/g, '&').replace(/\\, '<').replace(/\\>/g, '>').replace(/\\t/g, ' ').replace(/\\n/g, ''); if (shortdescription.length > 350){ shortdescription = "" + shortdescription.substring(0,250) + "... more"; } (".shortdescription a").click(function() { (".originaldescription").slideDown(); return false; }); }); Related content In this: publication By this: publisher In this Subject: Biology , Ecology By this author: LEWIS, TOM ; REIF, MICHAEL ; PRENDERGAST, ELLY ; TRAN, CUONG GA_googleFillSlot("Horizontal_banner_bottom");
Although numerous studies have demonstrated the effects of fire on the total amount of soil organic carbon (SOC), much remains unknown. In Autumn 2009, a well-controlled fire experiment was conducted in the boreal forest of Daxing'an Mountains, China. Over the next three years, repeated samplings were performed at settled points, taking the pre-fire state as the reference base (control). All soil samples were collected at a fixed sampling depth (0–10 cm). Soil organic carbon content (SOCC) and soil organic carbon density (SOCD) were examined simultaneously. A paired-samples T-test was employed to ascertain any possible significant changes after the fire. The total amount of SOC in 0–10 cm soil was dynamic after fire disturbance, and the direction and magnitude of the changes largely depended on the burning severity and the post-fire period. The spatial patterns of SOC changes and their temporal succession were closely associated with the primitive pattern of fire severity. For low- and medium-severity fires, no significant immediate change in SOCC or SOCD was detected. After one or two leaching seasons, a statistically significant increase (less than + 5% on average for SOCC, less than + 10% on average for SOCD) was observed in low- and medium-severity burning areas due to incorporation of fire-derived forest debris and semi-decomposed dead roots, but this minor increase was diminished or offset by the third year. High-severity fire caused significant immediate C loss in topsoil through direct combustion, while the subsequent changes varied: either rapidly and continually decreased until the third year (from approximately − 10% to − 60% for SOCC, and from − 5% to − 40% for SOCD) as a result of subsequent erosion, or increased dramatically (from + 40% to more than + 100% for SOCC) due to deposition of burnt OM and/or organic soil, depending on the convex or concave microtopography. The sensitivities of SOCC and SOCD to fire disturbance were inconsistent due to changes in soil bulk density. SOCD was relatively sensitive to the temporary increase after medium-severity fire, while SOCC was more sensitive to the prolonged decrease following high-severity burning. Factors affecting changes in SOC were more complicated than previously reported. In particular, the collapse, burning and erosion of topsoil all contributed to the downward-shift of actual sampling depth, which resulted in a “dilution effect” on SOCC and a “superaddition effect” on SOCD. This effect was an underlying reason for the sensitivity differentiation of the two indices and further complicated the characterization of changes in SOC.
Fire is a major driver of ecosystem change and can disproportionately affect the cycling of different nutrients. Thus, a stoichiometric approach to investigate the relationships between nutrient availability and microbial resource use during decomposition is likely to provide insight into the effects of fire on ecosystem functioning. We conducted a field litter bag experiment to investigate the long-term impact of repeated fire on the stoichiometry of leaf litter C, N and P pools, and nutrient-acquiring enzyme activities during decomposition in a wet sclerophyll eucalypt forest in Queensland, Australia. Fire frequency treatments have been maintained since 1972, including burning every two years (2yrB), burning every four years (4yrB) and no burning (NB). C:N ratios in freshly fallen litter were 29-42% higher and C:P ratios were 6-25% lower for 2yrB than NB during decomposition, with correspondingly lower 2yrB N:P ratios (27-32) than for NB (34-49). Trends in litter soluble and microbial N:P ratios were similar to the overall litter N:P ratios across fire treatments. Consistent with these, the ratio of activities for N-acquiring to P-acquiring enzymes in litter was higher for 2yrB than NB while 4yrB was generally intermediate between 2yrB and NB. Decomposition rates of freshly fallen litter were significantly lower for 2yrB (72±2% mass remaining at the end of experiment) than for 4yrB (59±3%) and NB (62±3%), a difference that may be related to effects of N limitation, lower moisture content, and/or litter C quality. Results for older mixed-age litter were similar to those for freshly fallen litter although treatment differences were less pronounced. Overall, these findings show that frequent fire (2yrB) decoupled N and P cycling, as manifested in litter C:N:P stoichiometry and in microbial biomass N:P ratio and enzymatic activities. These data indicate that fire induced a transient shift to N-limited ecosystem conditions during the post-fire recovery phase. This article is protected by copyright. All rights reserved.
The effects of fire on labile soil C and N in forest ecosystems are important for understanding C sequestration and N cycling not only because labile soil C and N are often variables that determine soil fertility but also because the role of soils as a source or sink for C is important on an ecosystem and on the regional level. In the current study, the literature on the effects of fire on soil organic C, total N, microbial biomass C and N, dissolved organic C, and total N, respiration, and N mineralization in mineral soil was reviewed, and the results of a meta-analysis on literature data were reported. Overall, fire significantly increased the soil total N, microbial biomass N, dissolved organic C, and total N, but decreased soil organic C, microbial biomass C, respiration and N mineralization. Among the significant effects of different fire types, wildfire had the higher effects on the soil organic C, total N, microbial biomass C and N, dissolved total N and respiration of soil than prescribed fire. In addition, responses of soil organic C, total N and N mineralization to wildfire depended on forest type and natural zone. Positive responses of soil organic C, total N were found in broadleaved forests and Mediterranean zones, and negative responses in coniferous forests and temperate zones. Wildfire significantly decreased N mineralization in coniferous forests. The effects of fire on soil microbial biomass C and N, dissolved organic C and N mineralization generally decreased with time after the fire. In general, the effects of fire on soil organic C, microbial biomass C, and dissolved total N and N mineralization decreased with increasing soil depth. These results suggest that fire increases C and N availability and increases microbial activity, which consequently decreases the potential rates of C sequestration.
Site preparation can alter soil physical, chemical and biological properties, which in turn may have significant impacts on tree growth of the following rotation. The major objective of this study was to investigate the impacts of season, soil compaction by mechanical harvesting and soil cultivation on soil microbial biomass carbon (C) and nitrogen (N) during the early stages of a second-rotation (2R) hoop pine (Araucaria cunninghamii) plantation. Soil (0–10 cm depth) was sampled for 14 consecutive months in an established factorial field trial at Yarraman, southeast Queensland. There were three compaction treatments (0 forwarder pass, 1 forwarder pass and 16 forwarder passes) and two cultivation treatments (zero cultivation and disc plough), which were randomly arranged in three blocks. There was seasonal and spatial variation in soil microbial biomass in mineral soils among the different compaction and cultivation treatments, with soil microbial biomass C (MBC) ranging from 167 to 1149 μg g−1, microbial biomass N (MBN) from 16 to 257 μg g−1, and microbial C:N ratios from 4.0 to 14.6. Fluctuations in soil microbial biomass were mainly driven by the seasonal changes in environmental conditions (including rainfall, temperature and soil moisture). The MBC was less variable with season than the MBN. In general, seasonal fluctuations in MBN were similar amongst the treatments with an apparent peak in August (late winter), followed by a sharp decrease to a lowest point in October (mid-spring), and then a second peak in December (early summer). Soil compaction did not significantly affect MBC and MBN, while soil cultivation significantly reduced MBC and MBN only in the 0 forwarder pass for the experimental period except February and March 2001 (summer–early spring) for MBC and January–March 2001 (summer–early spring) for MBN. The potential mechanisms for the diverse impacts of soil compaction and cultivation on soil microbial processes are discussed in relation to the seasonal environmental changes.
Few studies have examined the long-term responses of soil labile organic carbon (C) and nitrogen (N) and microbial activities to climate change in semiarid and arid regions. Here we investigated soil extractable organic carbon (EOC) and nitrogen (EON), microbial biomass and microbial metabolic activities at two depths of 0–10 and 10–20 cm in response to single and combined effects of warming and increased precipitation in a semiarid grassland of northern China since April 2005. Soil EOC and EON pools were measured using KCl and hot water extractions, and microbial metabolic activities were measured using MicroResp. Results showed that warming had no effects on EOC, EON and microbial biomass C (MBC) and N (MBN) in the two extracts as well as the ratio of MBC to MBN at the two depths, but increased precipitation significantly increased MBC, MBN, EON and microbial quotient at the 0–10 cm depth. Warming significantly decreased microbial metabolic activities at both soil depths, but significantly increased microbial metabolic diversity (H) and evenness (E) at the 10–20 cm depth. Increased precipitation significantly decreased microbial metabolic activities, but significantly increased H and E at the two depths. Warming and increased precipitation significantly interacted to affect microbial metabolic activities at the two depths as well as H and E at the 10–20 cm depth. Redundancy analysis determined that microbial quotient, i.e., the ratio of MBC to total C, pH and NH4+–N greatly accounted for the variances in the soil microbial metabolic profiles, but the ratio of EOC to EON, moisture and microbial quotient largely accounted for the variances in the soil microbial metabolic profiles specifically at the 10–20 cm depth, implying that microbial physiology such as microbial quotient rather than the amounts of labile organic C and N pools exerted more influence on driving the patterns of microbial metabolic profiles. Our results indicated that soil EOC and EON, microbial biomass and microbial metabolic activities at the two depths differentially responded to warming and increased precipitation in this semiarid region.
The release of extractable C and N by chloroform fumigation of 10 forest and two arable soils was compared with microbial C measured by direct microscopic counting (membrane filter technique). The soils varied with respect of pH (3.9–6.8) and content of organic C (2.6–36%). The amount of microbial C based on microscopic counts ranged from 332 to 1342 μ g cm−3.The release of C caused by fumigation correlated well with the results obtained from direct microscopic counting (R2 = 0.87). The regression model calculated for microbial C is Cm = (1.30 Cf + 309) μg cm−3 soil, where subscript m refers to the values for microscopic counting and subscript f to the release caused by fumigation. Assuming that fumigation causes a release of microbial N in the same proportion as for microbial C, the following regression model for microbial N was obtained: Nm (1.38 Nf + 45.3) fig cm−3 soil. The average amount of microbial C determined with the fumigation-extraction method for coniferous forest soils, deciduous forest soils and arable soils was 1.19, 1.13 and 1.40% of total C, respectively. The avarage amount of microbial N in these soils was 5.9, 3.4 and 2.5% of total N.The results suggest that the fumigation-extraction method can be used for the determination of microbial C and N in different types of forest soil.
Soil moisture strongly controls the uptake of atmospheric methane by limiting the diffusion of methane into the soil, resulting in a negative correlation between soil moisture and methane uptake rates under most non-drought conditions. However, little is known about the effect of water stress on methane uptake in temperate forests during severe droughts. We simulated extreme summer droughts by exclusion of 168mm (2001) and 344mm (2002) throughfall using three translucent roofs in a mixed deciduous forest at the Harvard Forest, Massachusetts, USA. The treatment significantly increased CH4 uptake during the first weeks of throughfall exclusion in 2001 and during most of the 2002 treatment period. Low summertime CH4 uptake rates were found only briefly in both control and exclusion plots during a natural late summer drought, when water contents below 0.15g cm−3 may have caused water stress of methanotrophs in the A horizon. Because these soils are well drained, the exclusion treatment had little effect on A horizon water content between wetting events, and the effect of water stress was smaller and more brief than was the overall treatment effect on methane diffusion. Methane consumption rates were highest in the A horizon and showed a parabolic relationship between gravimetric water content and CH4 consumption, with maximum rate at 0.23g H2Og−1 soil. On average, about 74% of atmospheric CH4 was consumed in the top 4–5cm of the mineral soil. By contrast, little or no CH4 consumption occurred in the O horizon. Snow cover significantly reduced the uptake rate from December to March. Removal of snow enhanced CH4 uptake by about 700–1000%, resulting in uptake rates similar to those measured during the growing season. Soil temperatures had little effect on CH4 uptake as long as the mineral soil was not frozen, indicating strong substrate limitation of methanotrophs throughout the year. Our results suggest that the extension of snow periods may affect the annual rate of CH4 oxidation and that summer droughts may increase the soil CH4 sink of temperate forest soils.
Pine forests bordering the Mediterranean Sea are often affected by severe wildfires, which cause major changes to soil organic matter (SOM). In this paper, recently burned and adjacent unburned areas of two coastal pine forests of Tuscany, Central Italy, were compared in terms of SOM quantity and quality to assess the nature and intensity of such fire-induced changes. Quantitative modification of the SOM stock was investigated by sampling in a grid pattern. Pre-fire and post-fire bulk SOM were analysed for stable carbon and nitrogen isotopes concentrations (δ13C and δ15N) and spectroscopic properties (solid-state CP-MAS 13C NMR). In addition, we determined the fraction of SOM resistant to acid dichromate oxidation, here assumed to be “pyrogenic” carbon, and the lignin composition after CuO oxidation.The results showed that at the two sites there were similar, significant losses in soil C, in spite of different times passed since the fire. Such C losses are attributable to the almost complete elimination of the litter layer, whereas the underlying mineral soil did not show any significant change in its carbon content. In terms of composition, the bulk SOM did experience a minor decrease in O-alkyl C and a parallel increase in aromatic C, but no significant change in the relative concentrations of 13C and 15N and the amount of pyrogenic C. On the contrary, fire markedly modified soil lignin composition. We recorded changes in the coumaryl to vanillyl and syringyl to vanillyl ratios of lignin-derived phenols, both of which are indicators of the lignin source. Furthermore, at one site, fire significantly increased the acid to aldehyde ratio of vanillyl and syringyl phenols, indicating that fire can affect soil lignin degradation and the overall C cycle. In conclusion, this study suggests that in fire-prone Mediterranean pine forests each fire may influence total SOM stocks and its chemical composition.
Prescribed burning is commonly used in forests to reduce fuel load, prevent encroachment of exotic species, maintain biological diversity and improve wildlife habitat. The low intensity burns that are conducted at intervals of 1–10years may have long-term effects on the abiotic and biotic components of the soil. We assessed how prescribed burning altered litter, soil physical and chemical properties, and soil microbial communities in upland oak forests subjected to prescribed burning at frequencies of 0 (unburned), 2.5 and 5 fires per decade (FPD) over a 20year period. Prescribed burning at 5 FPD reduced soil organic matter by 60% and soil organic carbon by 64% and increased bulk density by 20%. Compared to unburned controls, litter nitrogen was reduced by 20% and 21% and C/N ratio increased by 25% and 28% in sites burned at 2.5 and 5 FPD, respectively. Litter lignin/N ratio was reduced 28% at 2.5 FPD, compared to litter from unburned sites. We found no changes in soil pH, total N, NO3-N, NH3-N, plant-available Ps or K due to prescribed burning. Microbial biomass of Gram negative bacteria, as determined by phospholipid fatty acid (PLFA) analyses, decreased from 25% of biomarker abundance at the unburned sites to 20% at the 5 FPD sites. No other microbial functional group was significantly influenced by fire frequency. Our results indicate prescribed burning with low intensity fires in upland oak forests do not have major effects on the soils if these fires occur infrequently, i.e. less frequent than 2.5 FPD. However, frequent burning of these upland oak forests (5 FPD) resulted in important changes in the litter and soil that may adversely affect litter decomposition rates, soil carbon storage, soil water holding capacity, and soil erosion rates. Our findings indicate prescribed burning can be an important management tool, however, at high fire frequencies there may be tradeoffs between vegetation management goals and long-term adverse affects on the soil.
The N-2 fixation by understorey acacias in repeatedly burnt dry and wet sclerophyll forest sites in subtropical Australia was assessed using N-15 isotope dilution techniques. In the first study, aboveground parts of established acacias and nonlegume reference plants at the two sites were collected from plots subjected to varying fire frequencies for measurements of N-15 natural abundance (delta(15)N). The delta(15)N values of acacias and nonlegumes were similar, and substantial variation in these delta(15)N values precluded any evaluation of N-2 fixation. In the second study, N-15 enrichment method was used to examine N-2 fixation of acacia seedlings grown for 5 months in glasshouse pots of top 10-cm soils collected from the fire plots at the two sites. In Acacia leiocalyx (Domin) Pedley at the dry site, whole plant percent N derived from the atmosphere (%Ndfa) was 25% in unburnt soil, 66% in periodically burnt soil, and 42% in annually burnt soil (referenceAlphitonia excelsa (Cunn. ex Fenzl) Reisseck ex Benth.), compared with 33, 69, and 66%, respectively (reference Corymbia variegata (Hook.) K.D. Hill & L.A.S. Johnson). In Acacia oshanesii F. Muell. & Maiden at the wet site, whole plant %Ndfa was 9% in unburnt soil, 41% in quadrennially burnt soil, and 50% in biennially burnt soil (reference Dodonaea triquetra Andr.), compared with -4, 26, and 55%, respectively (reference Eucalyptus pilularis Sm.).
Additions of 15-N labelled ammonium sulfate were used to evaluate the effects of burning at 2- and 4-yr intervals during a 24 yr period on N mineralization and immobilization in a Pinus taeda stand in the Francis Marion National Forest, South Carolina. Net N mineralization in 10-d laboratory incubations of Oe + Oa plus 0-10 cm mineral soil was greatest in the control (210 mg N/m2), intermediate for the 2 yr interval burn treatment (87 mg N/m2), and lowest for the 4 yr interval burn treatment (78 mg N/m2). Forest floor and mineral soil C/N ratios were greater for burn treatments than for the control. All samples showed >95% immobilization of added 15N ammonium sulfate. -from Authors
The authors separated DOC from two freshwater environments, a lake and a blackwater marsh, into humic and nonhumic DOC. The humic fraction was used by natural bacterial assemblages from the lake and marsh as a C and energy source. Humic substances supported fourfold less bacterial secondary production per unit of initial C, however, than did nonhumic substances from the same environment. Bacterial utilization of humic compounds accounted for a significant fraction of the total bacterial production on DOC; humic substances supported an average of 22% of total growth on DOC from the lake and 53% of the total growth on DOC from the marsh. The relative bioavailability of both the humic and nonhumic fractions of DOC differed between the lake and blackwater marsh, with less bacterial production per unit of initial C occurring on marsh-derived dissolved compounds. -from Authors
Longleaf pine ecosystems throughout the southeastern United States developed under recurring fire disturbance, which often leads to conditions of low fertility, particularly reduced N pools in the soil. While numerous studies have documented short-term effects of prescribed burning on nutrient dynamics, few have evaluated the consequences of repeated fire on N availability and ecosystem productivity over longer time frames, such as a 3-year fire return interval. We assessed the environmental controls on soil inorganic N flux over a typical burn interval (3yr) and related N availability patterns to aboveground net primary productivity (ANPP) and N demand across a hydrologic gradient in a longleaf pine—wiregrass landscape. Net N mineralization was measured within 0–10 and 0–90cm soil depths to determine the influence of belowground litter inputs (via fine root turnover) on N dynamics. After 42mos, annual estimates of N mineralization were 11.8, 6.8 and 3.5kgha−1yr−1 for the top 10cm of soil and 15.5, 11.4, and 5.3kgha−1yr−1 for the top 90cm of soil for xeric, mesic and wet-mesic sites, respectively. Overall, N mineralization rates were negatively correlated with both ANPP and bulk soil moisture, and were insufficient to supply estimated ANPP-N demands. These results suggest that belowground litter inputs may indeed influence N cycling patterns in these frequently burned systems but may not entirely account for the discrepancy between N availability and ANPP-N demand.
The new Australian classification system is a multi-categoric scheme with classes defined on the basis of diagnostic horizons or materials and their arrangement in vertical sequence as seen in an exposed soil profile. This book brings together soils data from all over Australia accumulated over the past three decades. Serving as a framework for organising knowledge about Australian soils it provides a better means of communication among and between scientists of various disciplines and those who use the land. In the new scheme classes are mutually exclusive, and the allocation and identification of new and unknown soil types is by means of a key.
Natural abundances of the rare stable isotope of nitrogen, 15N, are now being used widely in research on N cycling in organisms and ecosystems. 15N natural abundances are used in fundamentally different ways from traditional 15N tracers by integrating N cycle processes via N isotope fractionations and the mixing of various N-containing pools. This approach of using 15N natural abundances still requires certain technical and conceptual advances before it can be used routinely in ecological research. Here, the basis of the natural abundance 15N approach and opportunities for applying it in ecology are reviewed, and recent progress towards overcoming some of the key technical problems and in revealing large-scale patterns in N cycle processes is discussed.
The N2 fixation by understorey acacias in repeatedly burnt dry and wet sclerophyll forest sites in subtropical Australia was assessed using 15N isotope dilution techniques. In the first study, aboveground parts of established acacias and nonlegume reference plants at the two sites were collected from plots subjected to varying fire frequencies for measurements of 15N natural abundance (<Q150E00000010446D80BFFEFF88A45505A9A1C8282ADCC6210090483DA6ED4F658F80>15N values of acacias and nonlegumes were similar, and substantial variation in these <$Q150E00000010446D80BFFEFF88A45505A9A1C8282ADCC6210090483DA6ED4F658F80>15N values precluded any evaluation of N2 fixation. In the second study, 15N enrichment method was used to examine N2 fixation of acacia seedlings grown for 5 months in glasshouse pots of top 10-cm soils collected from the fire plots at the two sites. In Acacia leiocalyx (Domin) Pedley at the dry site, whole plant percent N derived from the atmosphere (%Ndfa) was 25% in unburnt soil, 66% in periodically burnt soil, and 42% in annually burnt soil (referenceAlphitonia excelsa (Cunn. ex Fenzl) Reisseck ex Benth.), compared with 33, 69, and 66%, respectively (reference Corymbia variegata (Hook.) K.D. Hill & L.A.S. Johnson). In Acacia oshanesii F. Muell. & Maiden at the wet site, whole plant %Ndfa was 9% in unburnt soil, 41% in quadrennially burnt soil, and 50% in biennially burnt soil (reference Dodonaea triquetra Andr.), compared with -4, 26, and 55%, respectively (reference Eucalyptus pilularis Sm.).
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.
This before-and-after-impact study uses the natural abundance N isotope ratio (δ(15)N) to investigate the effects of a wildfire on sub-alpine ecosystem properties and processes. We measured the (15)N signatures of soil, charred organic material, ash and foliage in three sub-alpine plant communities (grassland, heathland and woodland) in south-eastern Australia. Surface bulk soil was temporarily enriched in (15)N immediately after wildfire compared to charred organic material and ash in all plant communities. We associated the enrichment of bulk soil with fractionation of N during combustion and volatilization of N, a process that also explains the sequential enrichment of (15)N of unburnt leaves > ash > charred organic material in relation to duration and intensity of heating. The rapid decline in (15)N of bulk soil to pre-fire values indicates that depleted ash, containing considerable amounts of total N, was readily incorporated into the soil. Foliar δ(15)N also increased with values peaking 1 year post-fire. Foliar enrichment was foremost coupled with the release of enriched NH4 (+) into the soil owing to isotopic discrimination during volatilization of soluble N and combustion of organic material. The mode of post-fire regeneration influenced foliar (15)N enrichment in two species indicating use of different sources of N following fire. The use of natural abundance of (15)N in soil, ash and foliage as a means of tracing transformation of N during wildfire has established the importance of combustion products as an important, albeit temporary source of inorganic N for plants regenerating after wildfire.
Production of nitrous oxide (N2O) by anaerobic denitrification is one of the most important processes in the global nitrogen (N) cycle and has attracted recent attention due to its significant impacts on climatic change. Fire is a key driver of many ecosystem processes, however, how fire drives the shift in microbial community and thus alters nutrient cycling is still unclear. In this study, a 35-year-old repeated prescribed burning trial, with three treatments (no burning, 2 yearly burning and 4 yearly burning), was used to explore how the long-term repeated prescribed burning affects N2O flux, key soil properties(inorganic N, dissolved organic carbon (DOC) and N, pH, electrical conductivity (EC), moisture), denitrification gene abundance and their interactions. Soil samples were collected in January and April 2011. Quantitative real-time PCR was employed to quantify the gene copy number of target genes, including narG, nirK, nirS and nosZ. In situ N2O fluxes ranged from 0 to 8.8 g N2OeN ha!1 h!1 with an average of 1.47 g N2O-N ha-1 h-1. More frequent fire (2 yearly burning) significantly reduced soil N2O fluxes, availability of C and N substrates and moisture, but increased soil pH and EC compared with no burning and 4 yearly burning treatments. Fire treatments did not significantly affect the abundance of most denitrification genes. There were no significant differences in most parameters measured between the 4 yearly burning and no burning treatments, indicating microbial community function is not affected by less frequent (4 year interval) burning. Variation in the N2O fluxes among the treatments can largely be explained by soil substrate (NO3-, DOC and total soluble nitrogen (TSN)) availability and soil environmental factors (pH, EC, and moisture), while the abundance of most denitrification genes were not related to the N2O fluxes. It is concluded that soil environmental factors rather than denitrification gene
abundance control N2O fluxes in this wet sclerophyll forest in response to long-term repeated fires.
A second rotation forest sand (Mt Burr sand) was separated by a combination of dry sieving and winnowing into different particle sizes rich in either soil or organic matter. These fractions were analysed for % loss on ignition, % organic carbon, total organic nitrogen and mineral nitrogen. Mineralization of soil organic nitrogen and nitrification of ammonium sulphate added to these fractions were studied. Amongst the heavier fractions obtained by sieving, the
The objectives of this study were to quantify the effects of prescribed fire on forest floor C and nutrient content, soil chemical properties, and soil leaching in a Jeffrey pine (Pinus jeffreyi [Grev. and Balf.]) forest in the eastern Sierra Nevada Mountains of California. The study included a prescribed fire and three timber harvest treatments: whole-tree (WT) thinning, cut-to-length (CTL) thinning, and no harvest (CONT). Prescribed fire resulted in significant decreases in forest floor C (-8 to -23 mg ha-1, or 39% to 61% decrease), N (-114 to -252 kg ha-1, or -31% to 51% decrease), S (0 to -15 kg ha-1, or 0% to 48% decrease), and K (-3 to -45 kg ha-1, or 12% to 51% decrease) contents but no significant change in Ca or Mg contents. In each case, the decreases were greatest in the CTL treatment, where slash accumulation before burning was greatest. Burning caused statistically significant effects on soil total nitrogen, C:N ratio, pH, water-extractable ortho-P, and water-extractable SO42- in some cases, but these effects were generally small, inconsistent among harvest treatments and horizons, and in the case of ortho-P much less than the temporal variation in both burned and unburned plots. There were no statistically significant effects of burning on total C, Bray-extractable P, bicarbonate-extractable P, and exchangeable Ca2+, K+, or Mg2+. Burning had no significant effect on soil solution pH, ortho-P, SO42-, NO3-, or NH4+ as measured by ceramic cup lysimeters and no effect on the cumulative leaching of ortho-P, NO3-, or NH4+ as measured by resin lysimeters. Burning had no effect on needle weight or nutrient contents as measured by the vector analysis. We conclude that prescribed fire had minimal effects on soils or water quality at this site, and that the most ecologically significant effect was the loss of N from the forest floor.
Dissolved organic matter (DOM) in soils plays an important role in the biogeochemistry of carbon, nitrogen, and phosphorus, in pedogenesis, and in the transport of pollutants in soils. The aim of this review is to summarize the recent literature about controls on DOM concentrations and fluxes in soils. We focus on comparing results between laboratory and field investigations and on the differences between the dynamics of dissolved organic carbon (DOC), nitrogen (DON), and phosphorus (DOP).
Both laboratory and field studies show that litter and humus are the most important DOM sources in soils. However, it is impossible to quantify the individual contributions of each of these sources to DOM release. In addition, it is not clear how changes in the pool sizes of litter or humus may affect DOM release. High microbial activity, high fungal abundance, and any conditions that enhance mineralization all promote high DOM concentrations. However, under field conditions, hydrologic variability in soil horizons with high carbon contents may be more important than biotic controls. In subsoil horizons with low carbon contents, DOM may be adsorbed strongly to mineral surfaces, resulting in low DOM concentrations in the soil solution. There are strong indications that microbial degradation of DOM also controls the fate of DOM in the soil.
Laboratory experiments on controls of DOM dynamics have often contradicted field observations, primarily because hydrology has not been taken into account. For example, laboratory findings on the effects of plant species (conifer vs. deciduous) on DOM release from forest floors and on the effects of substrate quality (e.g.: C/N ratio) or pH on DOC concentrations were often not confirmed in field studies. The high adsorption capacity of soil clay minerals and oxides for DOM shown in laboratory studies may not control the transport of DOM in soils in the field if macropore fluxes dominate under field conditions. Laboratory findings about the biodegradability of DOM also await verification under field conditions.
Studies that include DON and DOP dynamics in addition to DOC are few. The rate of release and the fate of DOC, DON, and DOP in soils may differ to a far greater extent than previously assumed. Controls established for DOC might thus be not valid for DON and DOP.
Despite intensive research in the last decade, our knowledge of the formation and fate of DOM in soils and its response to changing environmental conditions is still fragmented and often inconsistent. Predictions at the field scale are still very uncertain, and most of the information available today is the result of studies on temperate soils and forest ecosystems. Thus, future research on controls of DOM dynamics should be extended to soils under different land uses and in other climate zones. Emphasis should also be given to: (i) the effects of soil organic matter properties on the release of DOM (ii) environmental factors controlling DOM quantity and quality (iii) the assessment of biological versus physico-chemical controls on the release and retention of DOM in soils, and (iv) the differences between DOC, DON, and DOP. Finally, if our goal is to predict DOM concentrations and fluxes in soils, future research on the controls of DOM dynamics should have a strong focus on field studies.
This study is about the effects of forest fire on the organic matter from a Dystric Xerochrept under Quercus rotundifolia. In laboratory experiments carried out to simulate the effects of fire on isolated humic fractions, several physicochemical characteristics were described in the heated samples, as well as in humic substances extracted from samples of control and postfire soil areas.
The results obtained suggested that humic and fulvic acids underwent moderate structural modifications, but we found important changes in their colloidal properties, particularly regarding solubility.
The composition and properties of pyromorphic humus are discussed by using a tentative model for humus transformation on the basis of different fire-induced modifications of the soil organic fractions.
(C) Williams & Wilkins 1990. All Rights Reserved.
Summary Understanding the response of soil organic carbon (SOC) to environmental and management factors is necessary for estimating the potential of soils to sequester atmospheric carbon. Changes over time in the amount and distribution of SOC fractions with different turnover rates can be estimated by means of soil SOC models such as RothC, which typically consider two to five SOC pools. Ideally, these pools should correspond to measurable SOC fractions. The aim of this study was to test the relationship between SOC pools used in RothC and fractions separated through a fractionation procedure. A total of 123 topsoil samples from agricultural sites (arable land, grassland and alpine pasture) across Switzerland were used. A combination of physical and chemical methods resulted in two sensitive (particulate organic matter and dissolved organic carbon), two slow (carbon associated to clay and silt or stabilized in aggregates) and one passive (oxidation-resistant carbon) SOM fractions. These fractions were compared with the estimated equilibrium model pools when the corresponding soils were modelled with RothC. Analysis revealed strong correlations between SOC in measured fractions and modelled pools. Spearman's rank correlation coefficients varied between 0.82 for decomposable plant materials (DPM), 0.76 for resistant plant mate- rials (RPM), 0.99 for humified organic matter (HUM) and biomass (BIO), and 0.73 for inert organic matter (IOM). The results show that the proposed fractionation procedure can be used with minor adaptations to identify measurable SOC fractions, which can be used to initialize and evaluate RothC for a wide range of site conditions.
Four Italian surface soils were used to compare four different acid hydrolyses for the determination of the total content of carbohydrates in soils. Soil hydrolyses in 0.25M and 1M H2SO4 and by mechanical shaking for 16 h released carbohydrates as efficiently as the 8 h soil hydrolysis under reflux. Degradation of released carbohydrates was probably the cause of the low values given by the hydrolysis in 72% H2SO4 for 15 min followed by a 16 h shaking in 0.5M H2SO4. This study confirms that the carbohydrate determination based on the colorimetric phenol‐sulphuric acid method is more accurate than the colorimetric anthrone‐sulphuric acid method. Moreover, soil characteristics may influence the accuracy and precision of results depending on the hydrolysis procedure as it was shown by the soils rich in organic carbon and clay.
Soil from a field under long-term grass was treated with 0.02m sodium periodate for various periods up to 1176 h, followed by 0.1 d sodium tetraborate for 6 h. This destroyed an increasing proportion of microaggregates >45 μm and carbohydrate. After periodate treatment for 6 h about 70% of the soil sugars remained in the residue as measured by reducing sugar content and about 67% as individual sugars measured by gas-liquid chromatography. After 48 h the reducing sugar content was about 45%. An inverse linear relationship was established between the proportion by weight of microaggregates >45 μm and residual carbohydrate. The residual carbohydrate showed an enrichment in sugars commonly found in plant materials; glucose, arabinose and xylose, suggesting that the microbial carbohydrate had been preferentially destroyed. When the concentration of the periodate was increased to 0.05 m the residue contained about 50% of the original carbohydrate after 6 h treatment, and 25% after 48 h and an additional increase of about 10% in the proportion by weight of particles in the <45 μm range.
These results throw doubt on the validity of assumptions made in a number of studies about the limited extent to which soil polysaccharide is involved in aggregation.
Thermal resistance of the organic matter from two Humic Cambisols from the NW of Spain, developed over granite and under pine forest, was determined by heating samples of the upper 5 cm of soils at 220 and 350 °C for 30 min. Unheated samples of the same soils were used as control. Lignin, holocellulose, lipids and water-soluble compounds as well as humic substances were determined by different chemical fractionation methods. At 220 °C, the losses of holocellulose exceeded 75%, this being the most vulnerable organic fraction. At this temperature, the lipidic fraction exhibited different thermal resistance in both soils, showing losses of 73% in one case and only 11% in the other. Lignin exhibited the lowest losses, increasing proportionally. Fulvic and humic acids decreased at 220 °C but humin exhibited a net increase. At 350 °C, holocellulose practically disappeared and lignin losses were significant, whereas lipid loss slightly increased compared with the loss observed at 220 °C. All humic substances decreased at 350 °C, but humin was the most resistant humic fraction. Heating the soils at 220 and 350 °C increased the Fe and Al extracted with Na4P2O7 and NaOH and the percentage of humification of the remaining soil organic matter.