Effects Of Fire History Research Articles

Effects of fire history on thermal regimes of permafrost in the northern Da Xing’anling Mountains, NE China

Forest fires potentially result in the irreversible and rapid degradation of permafrost, soil evolution, successions of boreal forests, and consequent development of hazardous periglacial landforms. Two burned-areas of Mangui and Alongshan at the western flank of the northern Da Xing’anling Mountains in Northeast China were chosen to study the effects of forest fires on thermal regimes of near-surface permafrost and the active layer. The study results show risen post-fire ground temperatures with increasing fire severity, and mainly at depths of 0–1.5 m. Moreover, nine years after a severe burn, the depth of evident temperature changes exceeded 6 m, and a warming of 2.7 °C at 6 m depth was inferred. Presumably due to the influences of forest fires, the active layer thickness at severely burned sites was 3.8 m compared to 1.2 m at the un-burned site. Soil moisture content and organic-layer and snow-cover thicknesses also play important roles in further complicating the fire impacts on the permafrost environment. These impacting mechanisms and thresholds await more systematic, in-depth, and quantitative studies. Numerical models deem necessary for simulating and predicting the spatiotemporal variations in ground hydrothermal regimes under different fire severity and for evaluating the contributions and thresholds of changes in these important environmental factors (e.g., organic layer and snow cover) for the hydrothermal state of near-surface permafrost and active layer.

High fire frequency and the impact of the 2019–2020 megafires on Australian plant diversity

AbstractAimTo quantify the impact of the 2019–2020 megafires on Australian plant diversity by assessing burnt area across 26,062 species ranges and the effects of fire history on recovery potential. Further, to exemplify a strategic approach to prioritizing plant species affected by fire for recovery actions and conservation planning at a national scale.LocationAustralia.MethodsWe combine data on geographic range, fire extent, response traits and fire history to assess the proportion of species ranges burnt in both the 2019–2020 fires and the past.ResultsAcross Australia, suitable habitat for 69% of all plant species was burnt (17,197 species) by the 2019–2020 fires and herbarium specimens confirm the presence of 9,092 of these species across the fire extent since 1950. Burnt ranges include those of 587 plants listed as threatened under national legislation (44% of Australia's threatened plants). A total of 3,998 of the 17,197 fire‐affected species are known to resprout after fire, but at least 2,928 must complete their entire life cycle—from germinant to reproducing adult—prior to subsequent fires, as they are killed by fire. Data on previous fires show that, for 257 species, the historical intervals between fire events across their range are likely too short to allow regeneration. For a further 411 species, future fires during recovery will increase extinction risk as current populations are dominated by immature individuals.Main conclusionMany Australian plant species have strategies to persist under certain fire regimes, and will recover given time, suitable conditions and low exposure to threats. However, short fire intervals both before and after the 2019–2020 fire season pose a serious risk to the recovery of at least 595 species. Persistent knowledge gaps about species fire response and post‐fire population persistence threaten the effective long‐term management of Australian vegetation in an increasingly pyric world.

High fire frequency reduces soil fertility underneath woody plant canopies of Mediterranean ecosystems

Spatial heterogeneity of soil properties plays a major role in regulating ecosystem structure and functioning. In general, soil resources accumulate beneath woody plant-covered patches more than in the open interspace, making them function as fertility islands. Whilst wildfire is a common disturbance, little information is available on the role of particular plant species in maintaining soil fertility underneath in areas that are subjected to recurrent fires. This is an important issue given that land abandonment, together with a warmer and drier climate, is increasing fire danger in regions such as the Mediterranean. We determined whether increasing fire frequency, producing changes from a Quercus ilex L., woodland to a shrubland, modifies the effect of woody plant canopy on soil fertility. Additionally, the effect of fire history on species-specific leaf and litter nutrient concentration was assessed. Areas affected by none, one, two or three fires were selected. Within each area, soil fertility was measured underneath Cistus ladanifer L., Retama sphaerocarpa L., Phillyrea angustifolia L. and Quercus ilex canopies and in open interspace. Unburned soils located underneath P. angustifolia and Q. ilex canopies were significantly more fertile than in open interspaces. The microsite effect on soil fertility was fire frequency dependent. As fire frequency increased, the plant canopy microsite effect decreased for soil organic matter (SOM), cation exchange capacity (CEC), total C, P, Ca, K and Mg, labile phosphate, arylsulfatase and acid phosphatase activities. Total N, ammonium, nitrate and β-glucosidase activity decreased with increasing fire frequency, but their spatial variability was maintained along all fire frequency scenarios. Fire frequency decreased foliar N concentration but increased P concentration in some species, leading to a decrease in their N:P ratio. Our findings suggest that soil fertility heterogeneity will be reduced with increasing fire frequency. This could compromise the recovery of soil and ecosystem functioning.

Fire history and plant community composition outweigh decadal multi‐factor global change as drivers of microbial composition in an annual grassland

Abstract Soil microbial communities regulate and respond to key biogeochemical cycles and influence plant community patterns. However, microbial communities also respond to disturbance events, motivating an assessment of the relative roles of decadal multi‐factor global change, disturbance and plant community structure on microbial community responses. We used high‐throughput amplicon sequencing to characterize the diversity and composition of bacterial and fungal communities in bulk soil (0–7 cm) collected in 2014 from the Jasper Ridge Global Change Experiment, a full‐factorial field experiment in which ambient and elevated levels of nitrogen deposition (+7 g N m−2 yr−1 calcium nitrate), CO2 concentration (+275 ppm), temperature (+1–2°C) and precipitation (+50% volume with +3 weeks duration) were applied to a California annual grassland from 1998 to 2014. We used linear mixed‐effects modelling to test for the effects of global change on microbial diversity (observed richness, Shannon index). We also used generalized dissimilarity modelling (GDM) to study controls on compositional dissimilarity in fungal and bacterial communities. Bacterial community composition was best explained by exposure to fires in 2003 and 2011, whereas fungal community composition was best explained by plant community composition. The richness of fungi increased under elevated nitrogen deposition; bacterial diversity metrics decreased under warmer temperatures. Interactions between global change factors were statistically insignificant or weak. Synthesis. Our results indicate that even on decadal time‐scales, the effects of fire history and plant community composition on bacterial and fungal community composition, respectively, outweigh the effects of multi‐factor global change. Furthermore, global change factors have mostly additive effects on microbial diversity patterns. Our results show that highly variable mediators such as fire history and plant community composition limit the generalizability of soil microbial responses to long‐term global change.

The effect of fire history on soil nutrients and soil organic carbon in a semi-arid savanna woodland, central Namibia

Fire is an integral part of savanna ecosystems that has shaped these systems since the Miocene. Substantial uncertainty about fire effects in semi-arid ecosystems exists. Fire may affect ecosystem productivity directly through nutrient volatilisation, increased mineralisation and altering organic matter quantity, and indirectly through altering vegetation structure. We explored the effects of fire history and vegetation patch types (tree canopy vs inter-canopy) on soil nutrients and soil organic carbon (SOC) in a semi-arid ecosystem. We collected soil samples along transects in four treatments with different fire histories (1 to 24 years since the last burn). In the statistical analyses, tree canopy and inter-canopy samples along transects were differentiated. Fire showed an inconsistent effect on soil nutrients and SOC. There was a short-term negative influence on total nitrogen, whereas phosphorus, potassium and magnesium increased in the 1-year treatment. Sodium consistently decreased with increasing time since the last burn, whereas SOC and calcium were not affected. Calcium and magnesium were significantly higher under canopy relative to inter-canopy patches. There was no significant interactive effect between fire history and vegetation patch type on soil nutrients and SOC. Management decisions regarding fire within the frequency experienced in this system appear not to necessitate concern regarding soil resource impacts.

The effects of fire history on hollow-bearing tree abundance in montane and subalpine eucalypt forests in southeastern Australia

Hollow-bearing trees provide critical habitat resources for forest fauna, yet there is evidence of a ubiquitous decline in the large, old trees most likely to provide this resource. Fire can influence the formation and persistence of tree hollows. In this study, we investigated the effects of stand-level fire history and individual tree attributes on tree hollow abundance in two forest types in Namadgi National Park in the Australian Capital Territory: subalpine woodlands dominated by Eucalyptus pauciflora Sieber ex Spreng (snow gum); and tall-open E. delegatensis R.T.Baker (alpine ash) montane forest. These forests can be differentiated by their distinct response to fire; E. pauciflora resprouts following fire and E. delegatensis reproduces exclusively via seed. We employed a ground-based approach to measure 1044 trees across 36 sites selected by forest type and fire history as recorded since 1920. For both species, hollow abundance decreased with total fire count at stand level and increased for E. delegatensis in response to an extensive wildfire that occurred in the study area in 2003. The probability of a tree containing a hollow increased with tree diameter and if the tree was dead. Our results show that fire frequency and severity have strong implications for tree hollow abundance in montane and subalpine eucalypt forests.

Effects of Fire History on Amphibian and Reptile Assemblages in Rosemary Scrub

Abstract Florida scrub is a fire-maintained ecosystem with a high concentration of endemic and imperiled species. To assist in the conservation of these taxa, we evaluated how communities and populations of amphibians and reptiles varied with fire history in rosemary (Ceratiola ericoides) scrub. We calculated species richness, evenness, total abundance, and individual species abundance for all amphibians and reptiles captured from May through August 2003 and May 2004 at 12 rosemary scrub sites in Highlands County, Florida, that differed in fire history (time since last fire, TSF). Vegetation structure (bare ground and canopy cover) varied polynomially with TSF, with intermediate TSF sites most open and long-unburned sites least open. Species richness, evenness, and total abundance did not vary with fire history. At the species level, only two species, Plestiodon reynoldsi and Aspidoscelis sexlineata, showed significant relationships with TSF: P. reynoldsi was most common in least open, longest-unburned ar...

Effects of Fire History Upon Soil Macroarthropod Communities in Pinus Halepensis Stands in Attica, Greece

The composition of the soil macroarthropod community was studied in three forest stands which constitute a gradient of increased fire frequency. All stands were adjacent to each other, on the foothills of Mt. Penteli, Attica, Greece, and they shared similar physiography, climate, altitude, while their original pre-fire vegetation was a well-developedPinus halepensisforest. The stands were severely burned by a large fire early in summer 1995. Two of them had been burned previously: the first in 1978 and the second in 1978 and 1987. Sampling was carried out during the 2nd year after the last fire event. Although the phenology of soil macroarthropods was not altered in frequently burned stands, the number of taxa collected, as well as their population size, was extremely low. Canonical Correspondence Analysis showed that fire frequency does not directly affect soil arthropod communities, but influences them through increased abundance of specific plant groups, i.e., phrygana vegetation and legumes. Seasonality of climate seemed to be another significant factor controlling the structure of macroarthropod communities in the stands studied.

Effects of fire history on the structure and floristic composition of woody vegetation around Kalumburu, North Kimberley, Australia: a landscape-scale natural experiment

Indigenous landscape burning is practiced around remote communities in the Kimberleys but has been replaced by wildfires across uninhabited areas. A landscape-scale natural experiment was established to investigate the effects of these different fire histories (derived from a 10-year Landsat remote-sensing sequence) on the floristic structure and composition of woody vegetation within and among three of the major vegetation types on three landscape types (sandplain, sandstone and volcanics) near Kalumburu in the North Kimberley bioregion.Substrate factors determine vegetation and associated fire patterns within the landscape such that each landscape type needs to be examined independently. Basalt soils are dominated by an open savanna and tend to have very high fire frequencies. Basalt vegetation showed few significant response variables to fire-history parameters. The total density of woody stems showed no significant relationship to fire-history variables, regardless of size class. The 0–2.0-m size class of Erythrophleum chlorostachys (F.Muell.) Baillon showed significant (P < 0.005) responses to the various interactions involving all three fire-history variables, indicating that seedling density is sensitive to fire.Sandplain is dominated by open woodland, with relatively low fire frequency. Total stem density, shrub density and the densities of Grevillea agrifolia Cunn. Ex R.Br., Canthium sp. A and Stenocarpus cunninghamii R.Br. showed strong positive (P < 0.005) relationships with the total number of fire-free months. In sandstone, the density of all woody stems, acacias and a range of mid-storey trees showed significant positive relationships with the total number of fire-free months. Other species showed strong relationships with the number of late dry season fires. Vegetation thickening was evident in sand environments through the accumulation of woody stems in fire-free years and in sandstone through the promotion of 'fireweeds' such as Acacia gonocarpa F.Muell. after fire events.Mid-storey tree species capable of resprouting after fire showed some evidence of structural suppression in response to frequent fire events, including Planchonia careya (F.Muell.) Knuth, Persoonia falcata R.Br. and Buchanania obovata Engl.Results are discussed in the context of indigenous landscape burning and biodiversity conservation.