Burnt Grassland Research Articles

Impact of fire exclusion and aspect on soil carbon fractions in Afromontane grasslands, Cathedral Peak, South Africa

AbstractDespite the importance of South Africa's Afromontane grasslands for ecosystem services (water supply and biodiversity), soil organic carbon (SOC) research remains limited. These grasslands evolved with fire, and fire exclusion leads to native plant afforestation. This study investigated SOC fractions and origin to understand the impact of fire‐exclusion‐driven afforestation and aspect on SOC storage in Afromontane grasslands. This study in Cathedral Peak Research Catchments, initiated in the 1940s, compared an afforested fire‐excluded site (AF) to a periodically burnt (accidental fires, 2–5 years interval) grassland (PB) within the same catchment (Catchment‐IX). Additionally, it compared a south‐facing periodically burnt grassland (Catchment‐IX) to a north‐facing biennially burnt grassland (Catchment‐VI). Soil samples collected at soil‐depth increments (0–5, 5–10, 10–15, 15–20, 20–30, 30–60 and 60–100 cm) revealed that, within Catchment IX, PB had more topsoil SOC stocks and microbial activity than AF but similar active carbon (C) concentrations. As expected, δ13C values revealed that SOC in PB originates from C4 grasses, whilst it mostly originates from C3 plants in AF. The south‐facing slope (Catchment‐IX) had more SOC stocks, microbial activity and active C compared to the north‐facing slope (Catchment‐VI). Fire‐exclusion‐driven afforestation changed SOC input from roots to litter, thus reducing SOC storage. Cooler south‐facing slopes are better C reservoirs. Afromontane grasslands show greater potential for C sequestration than afforested systems.

Short-Term Postfire Effects on Ground-Dwelling Arthropods and Soil Attributes in a Semiarid Grassland Ecosystem, Northwestern China

Fire-induced effects on biota activity and diversity, and soil attributes, could have implications for biodiversity conservation and recovery of semiarid grassland ecosystems. Here, we examined the abundance and diversity of ground-dwelling arthropods, and soil attributes in burned and unburned grasslands in the semiarid Nanhuashan Natural Reserve in western Loess Plateau of China. Arthropods and soil were sampled in springtime one year after fire disturbance. We found no significant differences in total abundance of ground-dwelling arthropods between burned and unburned grasslands. However, the taxonomic richness and the Shannon index of ground-dwelling arthropods were found to be significantly greater in burned than unburned grasslands. Postfire effects also indicated significant differences in dominance hierarchy among taxa within functional groups as a consequence of increasing predatory abundance but decreasing phytophagous one from unburned to burned grasslands. Likewise, soil bulk density declined, whereas soil C/N increased significantly from unburned to burned grasslands. In conclusion, fire could promote the taxonomic richness and the diversity of ground-dwelling arthropods, thus being indicators of positive effect of fire disturbance on biodiversity conservation of semiarid grassland ecosystems of northwestern China. However, soil bulk density and soil C/N could be susceptible to fire-driven changes of soil attributes.

STUDI KEMANFAATAN HUTAN BAGI MASYARAKAT HUTAN DESA SEMBELANGAAN KABUPATEN KETAPANG PROVINSI KALIMANTAN BARAT

PT. Bumitama Gunajaya Agro is a palm oil company that is committed to and contributes to sustainable economic development and conservation to help social forestry in Sembelangaan Village Forest. This partnership pattern can be an example of social forestry management that is expected by the Indonesia Government, namely multi-party support.The research methodology uses a method to assess biodiversity created by HCVF Network and WWF (https://hcvnetwork.org/library/forest-integrity-assessment-tool/). This method was created by USAID LESTARI with Michigan State University USA. The results showed that of the 17 plots with a sampling intensity of 0.02 it is known that the average value of forest usefulness for the community is 27.24 categorized as forests is a mostly healthy forest. Habitat conditions include 10 wetlands, 16 streams, 4 seasonal flood forests, 6 natural wetlands, 17 springs, 8 burned grasslands, 11 partially slope topography, wildlife habitat, 1 cave, 7 waterfalls, 4 open pandan expanses and 12 large trees only in the field. Rare animals encountered 3 red gibbon, 1 marble cat, 9 birds, 10 eagles, 6 owls, 10 wild boar, 9 deer. The encounter in the form of 23 footprints, 36 heard the animals sound, 16 saw live animals, there were 7 nests, feathers and feces.Sembelangaan Forest provides 41 species of faunal flora that are directly beneficial to the community and 9 flora and habitats that benefit local culture and wisdom. These potentials can be developed for activities in Sembelangaan Village Forest that can be done together with PT BGA in forest conservation and improving community welfare

Quantifying the post‐fire recovery of taxonomic and functional diversity of dung beetles in the Brazilian Pantanal

Abstract The Pantanal is the largest wetland in the world and a World Heritage Site. During 2019–2020, the Pantanal has experienced the most severe burning in its history, with vast destroyed areas of vegetation and killed wildlife. Since the long‐term damage caused by fire to the Pantanal is still unknown, understanding how the biodiversity responds to post‐fire disturbance over a short‐term is an important step for conservation initiatives. The authors studied the effects of fire on dung beetle communities, a recognised bioindicator group, in the Brazilian Pantanal. For this, the authors assessed the patterns of taxonomic and functional diversity between unburned and burned sites (16 months post‐fire). The authors found that taxonomic and functional diversity of dung beetles were similar between unburned and burned grasslands, but with a distinct taxonomic composition post‐fire. The functional traits composition was similar between unburned and burned sites, demonstrating that this metric is less sensitive to fire effects in the Brazilian Pantanal. The study's results provide evidence that dung beetles exhibit high resistance to the occurrence of fire and fast recovery from its consequences. Thus, due to its ecological functions (secondary seed dispersion, nutrient cycling and others), these insects may assist ecological restoration of burned sites, being useful tools in restoration approaches for areas of the Pantanal that have been affected by fire. Finally, combining traditional taxonomic community attributes with functional diversity measurements provides a more comprehensive picture of responses of dung beetle communities, post‐fire, over a short‐term in the Brazilian Pantanal.

Perennial pasture grass invasion changes fire behaviour and recruitment potential of a native forb in a temperate Australian grassland

Invasive grasses can modify fire regimes of native ecosystems leading to changed ecosystem structure, composition, and functioning. Temperate grasslands in Australia are currently being invaded by a suite of exotic perennial pasture grasses, but their effects on ecosystems remain largely unknown. We aimed to determine the effect of invasion by the exotic perennial grass Phalaris aquatica on fire behaviour, as well as the regeneration potential of an endangered forb in temperate native grasslands in south-eastern Australia. Frequently burnt native grasslands invaded by exotic grasses were found to have two times more fuel than grasslands dominated by native grasses; in less-frequently burned native grasslands, exotic grasses contributed to fuel loads that were five times higher than native grasslands. Exotic-dominated grasslands burned differently than native grasslands; fire intensities were three times higher in exotic-dominated grasslands and had a wide variability in fire residence times. Soil heating was positively related to fire residence time but had no clear relationship with fire intensity. Seed germinability of Leucochrysum albicans var. tricolor (Hoary Sunray, Asteraceae) was reduced by exotic grass-fueled fire and increasing fire residence times. The observed changes in fire behaviour represent an invasion-driven shift in the ecosystem’s fire regime. By increasing fuel mass, fire residence time increased, and this influenced seed survival and subsequent germinability. Increased fire intensity following invasion highlights that invasive grasses can increase the fire-risk of grasslands. Maintaining native grasslands free of invasive pasture grasses therefore has environmental and fire-risk benefits.

Calcium Biogeochemical Cycle in a Typical Karst Forest: Evidence from Calcium Isotope Compositions

In order to better constrain calcium cycling in natural soil and in soil used for agriculture, we present the δ44/40Ca values measured in rainwater, groundwater, plants, soil, and bedrock samples from a representative karst forest in SW China. The δ44/40Ca values are found to differ by ≈3.0‰ in the karst forest ecosystem. The Ca isotope compositions and Ca contents of groundwater, rainwater, and bedrock suggest that the Ca of groundwater primarily originates from rainwater and bedrock. The δ44/40Ca values of plants are lower than that of soils, indicating the preferential uptake of light Ca isotopes by plants. The distribution of δ44/40Ca values in the soil profiles (increasing with soil depth) suggests that the recycling of crop-litter abundant with lighter Ca isotope has potential effects on soil Ca isotope composition. The soil Mg/Ca content ratio probably reflects the preferential plant uptake of Ca over Mg and the difference in soil maturity. Light Ca isotopes are more abundant in mature soils than nutrient-depleted soils. The relative abundance in the light Ca isotope (40Ca) is in the following order: farmland > burnt grassland > forests > grassland > shrubland. Our results further indicate that biological fractionation in a soil–plant system is a vital factor for Ca–geochemical transformations in soil surface systems.

Entire-area spring burning versus abandonment in grasslands: butterfly responses associated with hibernating traits

Entire-area spring burning is a common practice in many grasslands. Although there are many studies on the effects of entire-area spring burning on insects, the underlying mechanism of insect response is not well known. Herbivorous insect responses to spring burning are expected to be related to hibernating traits and grassland quality (host and nectar plants). I surveyed butterfly assemblages and vegetation characteristics (e.g., nectar flower occurrence, host plant richness, vegetation height, and vegetation coverage) as parameters of grassland quality for butterflies over 21 transects in 3 burned and 3 abandoned grasslands. Butterfly species were classified based on their hibernating traits, with a focus on endangered and grassland species. Although grassland quality as measured by nectar resources and host plants did not differ between the abandoned and burned grasslands, butterfly richness and abundance were lower in the burned grasslands. Each grassland, particularly two burned grasslands, supported a lower number of Red List grassland species, considering the presence of their host plants. Butterfly richness and abundance exhibited a unimodal response to vegetation height and were lower in burned grasslands; however, they were not related to other variables. Species associated with burned grasslands hibernated belowground or on the surface in sparse vegetation, whereas species associated with abandoned grasslands hibernated on the surface or aboveground. Therefore, although burning is an effective method to halt grassland decline, entire-area spring burning is detrimental to grassland butterfly species. Rotational patch fire and grassland restoration would be required to maintain grassland butterfly diversity.

Bryophytes Associated with Termite Mounds on the Northeastern Nigerian Highlands

Eighteen termite mounds on a stretch of undulating continuously grazed and burnt grasslands on the Mambilla Plateau, Eastern Nigeria, were surveyed for bryophytes. Bryophyte mats were present on all mounds investigated except one. The bryophyte mats were located at the base of the mounds, on a depression etched by raindrops and apparently serving to keep erosion at bay. We suggest that on grasslands with frequent fire episodes, the bryophyte mats may also play a role in fireproofing the mounds. In all, eight bryophytes species across five families were collected on the termite mounds. All species were new to the region but had been collected elsewhere from different substrates in Nigeria, except Fissidens ezukanmae Brugg.-Nann., which is a new species collected for the first time from termite mounds on Eastern Nigerian Highlands. Two species, Campylopus obrutus Ther. & P. de la Varde and Fissidens intramarginatus (Hampe) A.Jaeger, with estimated frequency of 24% each, were the most abundant species on the termite mounds.

Foraging decisions underlying restricted space use: effects of fire and forage maturation on large herbivore nutrient uptake.

Recent models suggest that herbivores optimize nutrient intake by selecting patches of low to intermediate vegetation biomass. We assessed the application of this hypothesis to plains bison (Bison bison) in an experimental grassland managed with fire by estimating daily rates of nutrient intake in relation to grass biomass and by measuring patch selection in experimental watersheds in which grass biomass was manipulated by prescribed burning. Digestible crude protein content of grass declined linearly with increasing biomass, and the mean digestible protein content relative to grass biomass was greater in burned watersheds than watersheds not burned that spring (intercept; F 1,251 = 50.57, P < 0.0001). Linking these values to published functional response parameters, ad libitum protein intake, and protein expenditure parameters, Fryxell's (Am. Nat., 1991, 138, 478) model predicted that the daily rate of protein intake should be highest when bison feed in grasslands with 400–600 kg/ha. In burned grassland sites, where bison spend most of their time, availability of grass biomass ranged between 40 and 3650 kg/ha, bison selected foraging areas of roughly 690 kg/ha, close to the value for protein intake maximization predicted by the model. The seasonal net protein intake predicted for large grazers in this study suggest feeding in burned grassland can be more beneficial for nutrient uptake relative to unburned grassland as long as grass regrowth is possible. Foraging site selection for grass patches of low to intermediate biomass help explain patterns of uniform space use reported previously for large grazers in fire‐prone systems.

The long-term effects of fire regime on primary production of montane grasslands in South Africa

Natural grasslands deliver essential ecosystem services through plant production, which enhances water supply, nutrient cycling, soil retention and greenhouse gas mitigation. Although the condition of montane grasslands for provision of ecosystem services is maintained by regular annual or biennial burning, controversy exists over the impact of different frequencies and seasons of burning on grassland productivity. The objective of this study was to determine the long-term effects of different burning regimes on primary production and quality of the montane grasslands of the KwaZulu-Natal Drakensberg. There were no significant differences in the mean standing live mass between 30 years of annual winter and biennial spring burning. However, in unburnt areas productivity was 20% lower (118.2 g m−2) than in regularly burnt grassland (144.7–154.5 g m−2). Crude protein did not vary between the annual winter and biennial spring treatments (95–113 kg ha−1), but was significantly lower in unburned areas (45 kg ha−1). However, an infrequent fire in a protected area caused a temporary spike in crude protein (16%) compared with regular burning (5–10%), which can benefit wildlife. We conclude that montane grasslands can be burnt annually or biennially in the dormant season to promote long-term productivity.

Assessing biodiversity integrity for the conservation of grazed and burnt grassland systems: avian field metabolic rates as a rapid assessment tool

The South African grassland system is home to over 3,300 plant species, 15 of the country’s 34 endemic mammal species, 12 of the 40 endemic bird species (four of which are globally threatened) and five RAMSAR wetland sites. To assess and address the ecological integrity of farmed grasslands we used process-oriented techniques, including nesting success and field metabolic rates (FMR) of birds, and an adaptation of the multi-taxon biodiversity intactness index (BII) using plant, arthropod and bird diversity data which is a comprehensive tool for assessing ecological integrity using multiple taxonomic groups. Current pastoral management practices have a significant detrimental effect on avian abundance, species richness, nest density and fledgling output. Overall energy turnover and BII values confirm the importance of conserved areas for birds in moist highland grassland systems and support the need for further conservation efforts in grassland systems by both private landowners and reserve managers. Findings based on both avian FMRs and the BII in this study were found to be comparable, lending support to the use of FMR as a rapid assessment technique for assessing ecosystem integrity for future studies of this nature. Scenarios of potential biodiversity improvement with changes in fire management regimes are also presented.

Variations in soil organic carbon contents and isotopic compositions under different land uses in a typical karst area in Southwest China

Land use changes can affect soil carbon storage in terrestrial ecosystems by altering either the biotic or the abiotic processes involved in carbon cycling, such as the adsorption of carbon on soil minerals. In this study, the organic carbon contents and their stable carbon isotopic compositions (δ13C) of five soil profiles under different land uses in the Maolan karst region in Southwest China were analyzed. Four non-forest samples from the karst were selected and examined to determine whether farmlands or grasslands that were converted from forestland were more effective in sequestering carbon in soils. The soil organic carbon (SOC) contents decreased in the following order: virgin forest, burnt grassland, shrubland, grassland, and farmland. However, no differences were observed in the δ13C values at the bottom of the five profiles, which indicated that most of the soil organic carbon was derived from the original virgin forest. The percentages of SOC that resulted from C4 plants in the virgin forest were significantly lower than the percentages in the other plots, while the percentages of SOC that resulted from C3 plants in the virgin forest were significantly higher than the percentages in the other plots. The δ13C values in the topsoils of the various profiles decreased in the following order: burnt grassland, farmland, grassland, shrubland, and virgin forest. From the surface to the base of the farmland profiles, little variation occurred in the δ13C values of the SOC (from -25.1 to -29.1‰). This variation in the δ13C values of the SOC in the surface soils was associated with changes in the vegetation cover. In addition, our results suggest that the plant functional type is important for controlling the depth-related changes in the SOC contents and the δ13C values of the SOC.

Fire and the dynamics of two unpalatable grass species (Cymbopogon pospischilii and Elionurus muticus) in a semi-arid climate

Cymbopogon pospischilii and Elionurus muticus are unpalatable for most of the growing season and form a reasonably large component of the vegetation composition in semi-arid grassland areas. The influence of an accidental fire on the dynamics of these two grass species was quantified over a three-year period (2008/09 to 2010/11 growing seasons) in a semi-arid grassland. After burning, the production of C. pospischilii was 18% higher than that of the total production of the rest of the burned species for the third growing season. Production of E. muticus was lowered by fire by 82% for the first season. Three years after the fire, the density of C. pospischilii was 14.52 plants m−2 versus an average for the unburned species of only 6.78 plants m−2. Seedling emergence from the seed bank for C. pospischilii and E. muticus, at the end of the third growing season, was respectively 6.6 and 12.4 seedlings m−2 more than that of unburned grassland – a reason for concern regarding plant composition stability of burnt semi-arid grasslands. This study provides a better understanding of the two unpalatable grass species Cymbopogon pospischilii and Elionurus muticus and the implications of this for the sustainable utilisation of semi-arid grassland.

Long-term weather sensitivity of open sand grasslands of the Kiskunság Sand Ridge forest-steppe mosaic after wildfires

We studied the long-term impact of wildfire on the vegetation dynamics of sand grasslands in a forest-steppe vegetation mosaic in Central Hungary (Kiskunsag). Long-term permanent quadrat monitoring was carried out from 1997 to 2008. We sampled the forest-steppe mosaic both in burnt and unburnt areas in 100 patches altogether using 1 m × 1 m quadrats. The effect of fire and precipitation on vegetation dynamics was characterized by patch type transitions between years. Patch types were defined by means of Cocktail method. Nine patch types of sand grasslands were altogether identified. The least productive patch types, bare soil and cryptogam dominance, did not occur in the burnt patches, while annual dominated patch type appeared only in burnt patches. The frequencies of patch type changes were significantly higher in burnt patches than in unburnt ones, independently on time after fire. All the eight patch types found in the unburnt patches proved permanent, while in the burnt patches only four of seven were so. The relative frequency of patch type changes did not correlate with precipitation in the vegetation period in the unburnt patches, while positively correlated in the burnt patches. It was concluded that the long-term difference in grassland dynamics between the unburnt and burnt patches, i.e., the excess of the patch type transitions in the burnt grasslands, is due to increased drought sensitivity of the grassland, which is the consequence of the elimination of the woody component of the forest-steppe vegetation.

Annual burning drives plant communities in remnant grassland ecological networks in an afforested landscape

Landscape ecological networks (ENs) are used to mitigate the negative effects of commercial forestry plantations on the biodiversity of southern Afromontane grasslands. Annually-burned firebreaks are fundamental to plantation forestry management, as they protect timber compartments from runaway fires. Here, we investigated the effect of annual burning with different levels of domestic cattle grazing in ENs, and annual burning without domestic cattle grazing in the adjacent protected area (PA). Sampling was conducted on three firebreak types, as well as two natural control grasslands (in the EN and PA each). The first two types (PA firebreaks and peripheral EN firebreaks) were on either side of the PA/plantation fenceline. The third type, plantation EN firebreaks, had forestry compartments on two sides and heavy cattle grazing. Although plant species richness was not significantly affected, plant communities of annually-burned firebreaks differed compositionally from those in the reference grasslands in the EN and PA respectively. Furthermore, plant species turnover was lower in annually-burned firebreaks than in reference EN and PA grasslands. Comparisons among different annually-burned firebreak types showed no difference in plant species richness. However, species composition and turnover of plant communities in peripheral EN fenceline firebreaks were similar to those of PA fenceline firebreaks, but both differed from the plantation EN firebreaks. Plant communities of longer-rotation burned grassland in the EN and PA were similar in species richness, composition and turnover. Overall, these results indicate that annual burning of firebreaks leads to homogeneous plant communities but not necessarily a reduction in species richness. High levels of cattle grazing exacerbate the effect of annual burning, as in plantation EN firebreaks. We recommend that managers should control heavy cattle grazing in annually-burned areas to maintain the natural plant communities as much as possible, while at the same time protecting the plantation blocks from runaway fires through necessary annual burning of appropriate firebreaks.

Evidence for Transceptor Function of Cellodextrin Transporters in Neurospora crassa

Neurospora crassa colonizes burnt grasslands and metabolizes both cellulose and hemicellulose from plant cell walls. When switched from a favored carbon source to cellulose, N. crassa dramatically up-regulates expression and secretion of genes encoding lignocellulolytic enzymes. However, the means by which N. crassa and other filamentous fungi sense the presence of cellulose in the environment remains unclear. Previously, we have shown that a N. crassa mutant carrying deletions of three β-glucosidase enzymes (Δ3βG) lacks β-glucosidase activity, but efficiently induces cellulase gene expression and cellulolytic activity in the presence of cellobiose as the sole carbon source. These observations indicate that cellobiose, or a modified version of cellobiose, functions as an inducer of lignocellulolytic gene expression and activity in N. crassa. Here, we show that in N. crassa, two cellodextrin transporters, CDT-1 and CDT-2, contribute to cellulose sensing. A N. crassa mutant carrying deletions for both transporters is unable to induce cellulase gene expression in response to crystalline cellulose. Furthermore, a mutant lacking genes encoding both the β-glucosidase enzymes and cellodextrin transporters (Δ3βGΔ2T) does not induce cellulase gene expression in response to cellobiose. Point mutations that severely reduce cellobiose transport by either CDT-1 or CDT-2 when expressed individually do not greatly impact cellobiose induction of cellulase gene expression. These data suggest that the N. crassa cellodextrin transporters act as "transceptors" with dual functions - cellodextrin transport and receptor signaling that results in downstream activation of cellulolytic gene expression. Similar mechanisms of transceptor activity likely occur in related ascomycetes used for industrial cellulase production.

Grassland Bird Response to Vegetation Structural Heterogeneity and Clearing of Invasive Bramble

Spatial and temporal patterns of disturbance and the subsequent heterogeneity are critical in maintaining biodiversity within grassland ecosystems. Grassland birds have evolved within this ‘shifting mosaic’ to become reliant on specific habitat characteristics maintained under varying levels of both natural and anthropogenic disturbance. Unfortunately, grasslands in South Africa have been extensively transformed and remain poorly conserved, threatening grassland avifauna. Mistbelt grassland is a threatened vegetation type endemic to the province of KwaZulu-Natal, of which only 0.3% is formally protected. This study investigated seasonal and patch type heterogeneity in a Mistbelt grassland avian community by determining avian community structure and composition in four patch types, i.e. i) untransformed open grassland, ii) burnt grassland, iii) bramble-invaded and, iv) bramble-cleared grassland, during winter and summer. Avian assemblages were significantly different between the different patch types for e...

Grassland bird response to vegetation structural heterogeneity and clearing of invasive bramble

Spatial and temporal patterns of disturbance and the subsequent heterogeneity are critical in maintaining biodiversity within grassland ecosystems. Grassland birds have evolved within this ‘shifting mosaic’ to become reliant on specific habitat characteristics maintained under varying levels of both natural and anthropogenic disturbance. Unfortunately, grasslands in South Africa have been extensively transformed and remain poorly conserved, threatening grassland avifauna. Mistbelt grassland is a threatened vegetation type endemic to the province of KwaZulu-Natal, of which only 0.3% is formally protected. This study investigated seasonal and patch type heterogeneity in a Mistbelt grassland avian community by determining avian community structure and composition in four patch types, i.e. i) untransformed open grassland, ii) burnt grassland, iii) bramble-invaded and, iv) bramble-cleared grassland, during winter and summer. Avian assemblages were significantly different between the different patch types for each season. The bramble patch type negatively affected grassland bird species diversity. Bramble-cleared grassland and untransformed grassland had similar vegetation structure and avian communities in the summer, suggesting that the grassland bird community benefitted soon after the clearing of invasive vegetation. This study provides further evidence that bird diversity is enhanced in structurally heterogeneous grassland landscapes. Furthermore, the protection and appropriate management of privately owned Mistbelt grassland, conserved in the form of rangeland, is an important refuge for threatened and endemic avifauna, such as the globally-threatened blue swallow (Hirundo atrocaerulea) and wattled crane (Bugeranus carunculatus).

Spatial models for monitoring the spatio-temporal evolution of ashes after fire – a case study of a burnt grassland in Lithuania

Abstract. Ash thickness is a key variable in the protection of soil against erosion agents after planned and unplanned fires. Ash thickness measurements were conducted along two transects (flat and sloping areas) following a grided experimental design. In order to interpolate data with accuracy and identify the techniques with the least bias, several interpolation methods were tested in the grided plot. Overall, the fire had a low severity. However, the fire significantly reduced the ground cover, especially on sloping areas, owing to the higher fire severity and/or less biomass previous to the fire. Ash thickness depended on fire severity and was thin where fire severity was higher and thicker in lower fire severity sites. The ash thickness decreased with time after the fire. Between 4 and 16 days after the fire, ash was transported by wind. The greatest reduction took place between 16 and 34 days after the fire as a result of rainfall, and was more efficient where fire severity was higher. Between 34 and 45 days after the fire, no significant differences in ash thickness were identified among ash colours and only traces of the ash layer remained. The omni-directional experimental variograms showed that variable structure did not change significantly with time. The ash spatial variability increased with time, particularly on the slope, as a result of water erosion.

Induction of lignocellulose-degrading enzymes in Neurospora crassa by cellodextrins

Neurospora crassa colonizes burnt grasslands in the wild and metabolizes both cellulose and hemicellulose from plant cell walls. When switched from a favored carbon source such as sucrose to cellulose, N. crassa dramatically upregulates expression and secretion of a wide variety of genes encoding lignocellulolytic enzymes. However, the means by which N. crassa and other filamentous fungi sense the presence of cellulose in the environment remains unclear. Here, we show that an N. crassa mutant carrying deletions of two genes encoding extracellular β-glucosidase enzymes and one intracellular β-glucosidase lacks β-glucosidase activity, but efficiently induces cellulase gene expression in the presence of cellobiose, cellotriose, or cellotetraose as a sole carbon source. These data indicate that cellobiose, or a modified version of cellobiose, functions as an inducer of lignocellulolytic gene expression in N. crassa. Furthermore, the inclusion of a deletion of the catabolite repressor gene, cre-1, in the triple β-glucosidase mutant resulted in a strain that produces higher concentrations of secreted active cellulases on cellobiose. Thus, the ability to induce cellulase gene expression using a common and soluble carbon source simplifies enzyme production and characterization, which could be applied to other cellulolytic filamentous fungi.