Long-term Effects Of Wildfire Research Articles

Resilience of temperate peatland vegetation communities to wildfire depends upon burn severity and pre-fire species composition.

Peatland ecosystems are of global conservation and environmental importance storing globally significant amounts of ancient carbon, regulating regional temperatures and hydrological regimes, and supporting unique biodiversity. Livestock grazing, land-use change, drainage, nutrient and acid deposition, and wildfire threaten the composition and function of many peatlands including those in the uplands of the United Kingdom. Presently, little is known about either the short- or long-term effects of wildfires within these systems in the UK. Our study aimed to evaluate how plant communities respond to wildfires across a range of vegetation communities, soil types, and burn severities. We evaluated wildfire burn severity using the ground-based Composite Burn Index adapted for treeless peatlands. Using paired burned-unburned plots, we quantified differences in the abundance of plant families and functional groups, vegetation diversity, and community composition. Multivariate differences in composition between burned and unburned areas were used as an index of community resilience to fire. Plots in heathland communities with shallow organic soils burned at the highest severities and had the greatest reductions in plant diversity and richness. There were significant declines in plot-scale species richness and diversity with increasing burn severity. Graminoids were resilient to fire whilst Ericaceae tended to increase with higher severity. Bryophyte composition was substantially altered-pleurocarpous species declined and acrocarpous species increased with greater burn severity. Community resilience was related to ground layer burn severity with higher burn severity driving greater changes in communities. Wildfire effects on temperate peatlands are a function of fire weather and site environmental and ecological characteristics. Management policy should ensure that the risk of severe wildfires is mitigated to protect ecosystem function and biodiversity. This will require system-specific fire management prescriptions across the gradient of peatland soil and vegetation types.

Long-term effects of wildfire on rock weathering and soil stoniness in the Mediterranean landscapes

The severe wildfire at Mt. Carmel, Israel, in 2010, caused massive destruction of carbonate rocks. The thermal shock caused extreme exfoliation, producing large and flat clasts, affecting rocks to a depth of up to 20 cm. A decade after the fire, most flakes and spalls disappeared from the rock outcrops and adjacent soils. From these observations, this study pursued two objectives: (a) to monitor and analyze the spatio-temporal distribution of the disintegrated flakes 10 years after the fire and (b) to test the hypothesis that fires contribute to increased soil stoniness via physical and chemical flake erosion.The studied area included five lithostratigraphic units composed of chalk, limestone, and dolomite. The Schmidt Hammer test showed that after a decade, most of the spalled surface on the burned outcrops was lost, exposing new rock surfaces to atmospheric and weathering processes. The spalls and flakes were broken down and pulverized.The most prominent effects were changes in surface stoniness on the rendzina soils over the chalks, while there was less impact on the dolomite and limestone samples. The stoniness of the non-burned chalk was 23–39% and increased significantly to 69–86% in the burned area. Chalk erosion produced large (>16 mm, median 8–16 mm) and abundant gravel, suggesting fragmentation of large spalls, and particles that lost their bladed shapes becoming oblate and equant.While earlier works suggested that increasing rock fragment cover is often associated with the removal of fine particles, our results showed a substantial increase in rock fragments due to fire-induced exfoliation of rock surfaces, leading to long-term changes in soil properties. We therefore propose that the size, shape, and spatial distribution of rock fragments should be considered when examining the effects of rock fragments on hydrological and geomorphological processes or on post-fire soil rehabilitation.

Utility of satellite-derived burn severity to study short- and long-term effects of wildfire on streamflow at the basin scale

We investigated the changes in hydrologic response in a forested catchment impacted by wildfire in Colorado U.S.A. from the storm event to the inter-annual scales. We also evaluated the utility of a remotely-sensed burn severity index to study post-fire shifts in streamflow. At the storm-scale, we evaluated hydrologic shifts through changes in the effective runoff (Q*/PTot), peak streamflow (Qpk) and response time (TR/TB) from multiple hydrographs, while at seasonal and inter-annual-scales we quantified hydrologic shifts through the runoff fraction (Q/PTot) and flow duration curves. Vegetation anomalies were monitored through comparisons of the Normalized Burn Ratio (NBR) between the burned and a hydrologically-similar, forested, neighboring, unburned catchment. We found short-term acute and long-term chronic transient streamflow shifts from the minute to the inter-annual scales. Flow duration curves indicate an order of magnitude increase in maximum flows. Event-average Q*/PTot increased by two orders of magnitude and Qpk increased by one order of magnitude relative to multiple representative pre-fire events of similar precipitation intensities. Decreases in TR/TB appear to be minimal. At the inter-annual scale, increases in the difference between simultaneous unburned and burned NBR are associated with increases in Q/PTot. A hydrologic recovery pathway is evident resembling a hysteresis effect driven by vegetation re-growth. Results illustrate the non-steady physical processes that increase flash-flooding risks post-fire in mountainous catchments and the utility of ΔNBR as a hydrologic predictor in ungauged watersheds.

Long-term effects of post-fire restoration types on nitrogen mineralisation in a Dahurian larch (Larix gmelinii) forest in boreal China

Fire is an important disturbance agent in Chinese boreal forests but the long-term effects of wildfires on soil nitrogen (N) net mineralisation rates (Rmin) in natural versus human-assisted restorations are not well understood. In this study, we analysed upper (0–10cm) and lower layer (10–20cm) soil samples from natural restoration and afforestation plots in a Dahurian larch (Larix gmelinii) forest in north-eastern China 29years after a mega fire disturbance. Our results showed that the soil inorganic N (NH4+-N and NO3−-N) pool of the upper and lower layers of the regenerated plots remained significantly lower than in unburned control plots. This suggests that the effects of a high burn severity fire on soil N availability were still significant almost 30years after the event. Restoration type (natural restoration versus afforestation) also had significant effects on upper layer soil N availability; compared with afforestation, natural restoration was more beneficial for the accumulation of soil inorganic N and the recovery of Rmin after fire disturbance. Specifically, the concentration of inorganic N and the mean Rmin in upper layer soils in the natural restoration plots were approximately 41% greater and 3.6 times greater, respectively, than in the afforestation plots. The differences in soil N availability between the two restoration types were attributed to differences in soil water content (SWC), soil microbial biomass nitrogen (MBN), and the recovery of vegetation after the fire disturbance. Our study demonstrates that natural restoration has proved more successful than afforestation in countering soil N losses in boreal forests in China resulting from a high burn severity fire disturbance.

Assessment of the Decadal Impact of Wildfire on Water Quality in Forested Catchments

Wildfire can have significant impacts on hydrological processes in forested catchments, and a key area of concern is the impact upon water quality, particularly in catchments that supply drinking water. Wildfire effects runoff, erosion, and increases the influx of other pollutants into catchment waterways. Research suggests that suspended sediment and nutrient levels increase following wildfire. However, past studies on catchment water quality change have generally focused on the short term (1–3 years) effects of wildfire. For appropriate catchment management, it is important to know the long-term effect of wildfire on catchment water quality and the recovery process. In this study, a statistical analysis was performed to examine the effect of 2001/2002 Sydney wildfire on catchment water quality. This research is particularly important, since the catchments studied provide drinking water to Sydney. Linear mixed models were used in this study in an analysis of covariance (ANCOVA)-type change detection approach to assess the effect of wildfire. We used both burnt and unburnt catchments to aid the interpretation of the results and to help disentangle the effects of natural climate variation, as well as of the wildfire. The results of this study showed persistent long-term (10-year) effects of wildfire, including increases in total suspended sediment concentrations (64% higher than in unburnt catchments), total nitrogen concentrations (48% higher), and total phosphorus (40% higher).

Long-term effects of wildfire on available soil nutrient composition and stoichiometry in a Chinese boreal forest

Wildfire disturbance is a major driver of biogeochemical processes in Eurasian boreal forests, yet little is known about the response of soil nutrient stoichiometry to wildfire in this ecosystem. To fill this gap, we measured the composition of available soil nutrients and their stoichiometric ratios in a Chinese boreal forest along a gradient of fire history. In the 1-year-post-fire site, wildfire increased the relative abundances of element nitrogen (N), phosphorus (P), Sulphur (S), iron (Fe), and aluminum (Al), and reduced the abundances of element calcium (Ca), magnesium (Mg), and potassium (K). Available soil N:K, N:S, P:K, P:S, and S:K ratios were 240%, 70%, 440%, 160%, and 150% higher than the control, but N:P ratio was not significantly different. In the 11-year-post-fire site, the soil nutrient composition recovered to the pre-fire levels. Although most of the soil nutrient stoichiometry returned to pre-fire levels, soil N:P ratios became significantly higher. These results showed immediate wildfire effects on soil nutrient availability and composition were strongly related to fire severity, but such effects could be subdued by soil environment and topographical variations over time. Although wildfire effects on soil nutrients are mostly short-term, it could produce relatively long-term effects on balance between N and P.

Response of Lizards to High-Severity Wildfires in a Southern United States Mixed Pine/Hardwood Forest

High-severity forest fires are increasing in large areas of the southern and western United States as the climate becomes warmer and drier. Natural resource managers need a better understanding of the short- and long-term effects of wildfires on lizard populations, but there is a paucity of studies focused on lizard-wildfire relationships. We used a before-after, control-impact (BACI) sample design to assess the response of three lizard species—Six-lined Racerunner (Aspidoscelis sexlineata), Prairie Lizard (Sceloporus consobrinus), and Little Brown Skink (Scincella lateralis)—to high-severity wildfires that occurred in the Lost Pines Ecoregion, Texas, USA. Specifically, we analyzed monitoring data collected across 17 trapping sessions from spring 2008 to spring 2013 using stratified N-mixture models to estimate trends in lizard abundances, while accounting for environmental parameters that might influence lizard detectability. We found no evidence of a fire-induced change in abundance for any of the lizar...

Mid- and long-term effects of wildfire and debris flows on stream ecosystem metabolism

Wildfire is an important and prevalent agent of disturbance in vegetated landscapes across much of the Earth’s surface, including forested watersheds in the arid western USA. Between 1992 and 2003, >40% of the watersheds in the upper reaches of the Boise River watershed in central Idaho burned. The purpose of our study was to investigate the legacy effects of wildfire on stream ecosystems by analyzing the relationship between wildfire and resulting debris flows and their joint effects on stream ecosystem metabolism in 31 streams. The watersheds of ∼½ of these streams burned within the last 11 y, and some of these burned watersheds also experienced large-scale debris flows 1 y postfire. Streams with burned watersheds recovered quickly, and estimates of photosynthetically active radiation, gross primary production, and ecosystem respiration were indistinguishable from those in streams draining unburned watersheds. However, streams that experienced debris flows after their watersheds burned were remarkably different. They exhibited higher production and incident light and lower ecosystem respiration. Debris flows resulted in nearly complete removal of streamside vegetation, slowed recovery of the riparian canopy, and altered stream ecosystem metabolism. Our results suggest a synergistic interaction between wildfire and associated geomorphological processes whereby debris flows delay succession of stream ecosystems, possibly resulting in altered recovery trajectories, communities, and foodweb interactions.

The effects of catastrophic wildfire on water quality along a river continuum

AbstractTo further our understanding of the linkages among wildfire, streamflow pathways, and water chemistry, we used a network of water-quality sensors and streamflow gages to assess initial and long-term effects of wildfire along a river continuum. We assessed water quality of a 2nd- and a 4th-order stream in a single watershed for 5 monsoon seasons before, during, and after a catastrophic wildfire. Fire had significant and sustained long-term effects on both streams. In the 2nd-order stream, variability in dissolved O2 (DO) increased after the fire. Daily total precipitation was unchanged, but episodic storm events resulted in significant increases in stream discharge that led to elevated turbidity and specific conductance (SC). In the 4th-order stream, fire led to minimal measurable effects on turbidity, elevated SC, and greater variability of the DO signal. We also assessed water-quality data from 4 sites along the river continuum for a 4-mo period before, during, and after the wildfire. Large overl...

Dale W. Johnson, et al. The Long-Term Effects of Wildfire and Post-Fire Vegetation on Sierra Nevada Forest Soils. Forests 2012, 3, 398-416

The authors would like to add a co-author “Brittany G. Johnson” as sixth author in the published paper [1], doi: 10.3390/f3020398, website: http://www.mdpi.com/1999-4907/3/2/398. After publication, we discovered that we left our one deserving graduate student author from the published paper, Brittany G. Johnson, who helped in collecting data for this paper. The authors apologize for any convenience this may have caused. [...]

Effect of wildfires on soil respiration in three typical Mediterranean forest ecosystems in Madrid, Spain

Mediterranean forests are vulnerable to numerous threats including wildfires due to a combination of climatic factors and increased urbanization. In addition, increased temperatures and summer drought lead to increased risk of forest fires as a result of climate change. This may have important consequences for C dynamics and balance in these ecosystems. Soil respiration was measured over 2 successive years in Holm oak (Quercus ilex subsp. ballota; Qi); Pyrenean Oak (Quercus pyrenaica Willd; Qp); and Scots pine (Pinus sylvestris L.; Ps) forest stands located in the area surrounding Madrid (Spain), to assess the long term effects of wildfires on C efflux from the soil, soil properties, and the role of soil temperature and soil moisture in the variation of soil respiration. Soil respiration, soil temperature, soil moisture, fine root mass, microbial biomass, biological and chemical soil parameters were compared between non burned (NB) and burned sites (B). The annual C losses through soil respiration from NB sites in Qi, Qp and Ps were 790, 1010, 1380 gCm−2 yr−1, respectively, with the B sites emitting 43 %, 22 % and 11 % less in Qi, Qp and Ps respectively. Soil microclimate changed with higher soil temperature and lower soil moisture in B sites after fire. Exchangeable cations and the pH also decreased. The total SOC stocks were not significantly altered, but 6–8 years after wildfires, there was still measurably lower fine root and microbial biomass, while SOC quality changed, indicated by lower the C/N ratio and the labile carbon and a relative increase in refractory SOC forms, which resulted in lower Q10 values. We found long term effects of wildfires on the physical, chemical and biological soil characteristics, which in turn affected soil respiration. The response of soil respiration to temperature was controlled by moisture and changed with ecosystem type, season, and between B and NB sites. Lower post-burn Q10 integrated the loss of roots and microbial biomass, change in SOC quality and a decrease in soil moisture.

The Long-Term Effects of Wildfire and Post-Fire Vegetation on Sierra Nevada Forest Soils

This paper compares carbon (C) and nutrient contents in soils (Alfisols derived from andesite), forest floor and vegetation in a former fire (1960) and an adjacent forest in the Sagehen Watershed in the Sierra Nevada Mountains of California. Soils from the former fire (now occupied predominantly by Ceanothus velutinus, a nitrogen-fixing shrub) had significantly lower contents of extractable SO42− and P (both Bray and bicarbonate) but significantly greater contents of exchangeable Ca2+ than the adjacent forested site (dominated by Pinus jeffreyii). 15N data suggested that N fixation had occurred in the former fire site, but N contents did not differ between the two sites. O horizon C and nutrient contents did not differ between the two sites, but vegetation C and nutrient contents were significantly greater in the forested than former fire site. These results contrast with those from a nearby, previous study at Little Valley Nevada, also dominated by P. jeffreyii growing on a different soil type (Entisols derived from granite). In the Little Valley study, soil C, N, Ca2+, Mg2+, and K+ contents within the former fire (1981, now also occupied predominantly by Ceanothus velutinus) were greater than in the adjacent forest (Pinus jeffreyii) but soil extractable P contents either did not differ or were greater in the former fire. We conclude that soil parent material is an indirect but strong mediator of the effects of post-fire vegetation on soils in this region, especially with respect to soil P changes, which vary substantially between andesite- and granite-derived soils.

Long-term effects of wildfires on the biochemical quality of soil organic matter: A study on Mediterranean shrublands

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 5cm) were submitted to a four-step chemical fractionation, consisting of an extraction with dilute K2SO4 solution, and two consecutive hydrolyses, first with H2SO4 2.5M and next with 72% H2SO4, further diluted down to 1M. 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 280nm 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.

Long-term effects of a wildfire on a lizard assemblage in the Arid Chaco forest

The long-term (14 years) effects of a high-intensity wildfire on a lizard assemblage were studied in Chancaní Provincial Natural Park and Forest Natural Reserve (Córdoba, Argentina), by comparing a burned area with an unburned one within the protected area. Lizard diversity and abundance were measured using 25 drift-fence pitfall traps in the burned area and in a portion of the unburned forest during two summers (2006–2007 and 2007–2008). A total of 426 lizards belonging to eight species were captured. Total captures were 40% higher in the unburned area than in the burned one. From the eight species recorded, five ( Homonota fasciata, Leiosaurus paronae, Stenocercus doellojuradoi, Liolaemus chacoensis, and Teius teyou) were more abundant in the unburned area, whereas the remaining species ( Tropidurus etheridgei, Mabuya dorsivittata and Vanzosaura rubricauda) did not differ between areas. The differences observed in lizard numbers between sites may be related to fire-driven changes. A marked increase in grass cover determining the reduced availability of bare and litter-covered ground, fallen logs and dead wood, favorite microhabitats for most lizard species, is of particular significance.

Changes in net N mineralization rates and soil N and P pools in a pine forest wildfire chronosequence

The concern that climate change may increase fire frequency and intensity has recently heightened the interest in the effects of wildfires on ecosystem functioning. Although short-term fire effects on forest soils are well known, less information can be found on the long-term effects of wildfires on soil fertility. Our objective was to study the 17-year effect of wildfires on forest net mineralization rates and extractable inorganic nitrogen (N) and phosphorus (P) concentrations. We hypothesize that (1) burned forest stands should exhibit lower net mineralization rates than unburned ones; (2) these differences would be greatest during the growing season; (3) differences between soil variables might also be observed among plots from different years since the last fire; and (4) due to fire-resistant geochemical processes controlling P availability, this nutrient should recover faster than N. We used a wildfire chronosequence of natural and unmanaged Pinus canariensis forests in La Palma Island (Canary Islands). Soil samples were collected during winter and spring at 22 burned and unburned plots. We found significantly higher values for net N mineralization and extractable N pools in unburned plots. These differences were higher for the winter sampling date than for the spring sampling date. Unlike extractable N and N mineralization rates, extractable P levels of burned plots exhibited a gradual recovery over time after an initial decrease. These results demonstrate that P. canariensis forest soils showed low resilience after wildfires, especially for N, and that this disturbance might induce long-term changes in ecosystem functioning.