Forest Fire Disturbance Research Articles

Interactions between wind and fire disturbance in forests: Competing amplifying and buffering effects

Many studies of ecological disturbance highlight the unexpected impact that compounded disturbances have on communities. One of the well-studied mechanisms by which forest wind and fire disturbances interact is that wind damage increases flammable fuels—amplifying the effects of fire—leading to unexpected changes in vegetation composition. However, wind disturbance may also buffer the effects of fire through mechanisms such as disrupting fuel continuity. The extent to which wind and fire disturbances buffer, or reduce, the magnitude of ecological change has been less well studied. In this study, we winched trees in a Pinus taeda L. forest to simulate wind damage in experimental plots and combined this treatment with prescribed fire. This design allowed investigation of how forest regeneration responds to combinations of wind and fire disturbance, with particular emphasis on whether disturbance interactions were amplifying or buffering. We also tested for evidence of two mechanisms of disturbance interaction that are expected to buffer the cumulative ecological impact of wind and fire disturbances, testing (1) whether wind damage increased resprouting response following fire and (2) whether seedlings on tip-up mounds were protected from fire. We identified evidence for a combination of disturbance interactions occurring in both an amplifying direction (e.g., rapid recruitment and establishment of Rhus copallinum) as well as interactions occurring in a buffering direction (e.g., increased resilience in resprouting saplings in winched plots). Such varying responses may lead to a heterogeneous mixture of amplifying and buffering effects following compounded disturbances, such that at the stand scale, the aggregate regeneration response of two disturbances is the net effect of these individual interaction mechanisms. The results of this study highlight that mechanisms of disturbance interactions may vary spatially and temporally and may be best understood by considering factors such as disturbance severity, species life history traits, and timing between disturbances.

Automatic detection of forest fire disturbance based on dynamic modelling from MODIS time-series observations

ABSTRACTForest disturbances provide an important reference and a basis for studying the carbon cycle, biodiversity, and eco-social development. Remote sensing is a promising data source for monitoring forest ecosystem dynamics and detecting disturbance areas. This research used a seasonal trend method to model Moderate Resolution Imaging Spectroradiometer (MODIS) normalized difference vegetation index (NDVI) time series from 2007 to 2011 recursively with a fixed-size temporal sliding window and a step length of 1 (i.e. 16 days). Model parameter variations were monitored to detect changes in the structure of the time-series data. Significant changes in the time-series structure were captured as disturbance signals. The method was applied to the 2009 Minto Flats fire in Alaska, USA, and the forest-disturbance detection results obtained using the proposed method essentially agreed with the Monitoring Trends of Burned Severity data set. This result indicates that the proposed method can reliably reveal the occurrence of forest fire disturbances. Moreover, because the model parameter variations reflect the disturbance signal, and the modelling and detection process requires only MODIS NDVI time-series data without any other ancillary ground information, the disturbance area can be detected effectively and automatically.

Simulating the effects of climate change and fire disturbance on aboveground biomass of boreal forests in the Great Xing'an Mountains, Northeast China

Predicting the effects of climate warming and fire disturbance on forest aboveground biomass is a central task of studies in terrestrial ecosystem carbon cycle. The alteration of temperature, precipitation, and disturbance regimes induced by climate warming will affect the carbon dynamics of forest ecosystem. Boreal forest is an important forest type in China, the responses of which to climate warming and fire disturbance are increasingly obvious. In this study, we used a forest landscape model LANDIS PRO to simulate the effects of climate change on aboveground biomass of boreal forests in the Great Xing'an Mountains, and compared direct effects of climate warming and the effects of climate warming-induced fires on forest aboveground biomass. The results showed that the aboveground biomass in this area increased under climate warming scenarios and fire disturbance scenarios with increased intensity. Under the current climate and fire regime scenario, the aboveground biomass in this area was (97.14±5.78) t·hm-2, and the value would increase up to (97.93±5.83) t·hm-2 under the B1F2 scenario. Under the A2F3 scenario, aboveground biomass at landscape scale was relatively higher at the simulated periods of year 100-150 and year 150-200, and the value were (100.02±3.76) t·hm-2 and (110.56±4.08) t·hm-2, respectively. Compared to the current fire regime scenario, the predicted biomass at landscape scale was increased by (0.56±1.45) t·hm-2 under the CF2 scenario (fire intensity increased by 30%) at some simulated periods, and the aboveground biomass was reduced by (7.39±1.79) t·hm-2 in CF3 scenario (fire intensity increased by 230%) at the entire simulation period. There were significantly different responses between coniferous and broadleaved species under future climate warming scenarios, in that the simulated biomass for both Larix gmelinii and Betula platyphylla showed decreasing trend with climate change, whereas the simulated biomass for Pinus sylvestris var. mongolica, Picea koraiensis and Populus davidiana showed increasing trend at different degrees during the entire simulation period. There was a time lag for the direct effect of climate warming on biomass for coniferous and broadleaved species. The response time of coniferous species to climate warming was 25-30 years, which was longer than that for broadleaf species. The forest landscape in the Great Xing'an Mountains was sensitive to the interactive effect of climate warming (high CO2 emissions) and high intensity fire disturbance. Future climate warming and high intensity forest fire disturbance would significantly change the composition and structure of forest ecosystem.

산불이 산림토양의 영양염류의 동태에 미치는 영향

Forest fires are major environmental disturbances, and can affect the physical, chemical, mineralogical, and biological properties of the soil. This study was carried out to determine the effects of forest fire disturbance on functions of the ecosystem. We examined the influence of fire on the chemical properties of soil in a recently burned pine forest in Seosan, Chungcheongnam-do Province in Korea. Immediately after a fire, we established four burned plots and control plots outside the margin of the fire. Soil organic matter, water content, and total nitrogen was slightly lower than those in the unburned sites. The soil pH, NO3-N and NH4-N contents of the burned site was significantly higher than those in the unburned site. The concentrations of calcium in the burned soil was approximately 1.1～1.5 times higher than that in the top-soil (0～5cm) of the unburned site during the experimental period. In contrast, the concentration of magnesium was lower than that in all soil layers in the unburned site. The concentration of phosphorus partially increased in the burned site (1.4 times), but rapidly decreased. The total nitrogen content decreased in all soil layers of the burned sites. The chemical properties of the top-soil of the burned site were observed to be restored within five months after the fire, but we believe that the restoration of soil layers below 5cm requires additional time.

Climatic and topographic controls on patterns of fire in the southern and central Appalachian Mountains, USA

Climate and topography are two important controls on spatial patterns of fire disturbance in forests globally, via their influence on fuel moisture and fuel production. To assess the influences of climate and topography on fire disturbance patterns in a temperate forest region, we analyzed the mapped perimeters of fires that burned during 1930–2003 in two national parks in the eastern United States. These were Great Smoky Mountains National Park (GSMNP) in the southern Appalachian Mountains and Shenandoah National Park (SNP) in the central Appalachian Mountains. We conducted GIS analyses to assess trends in area burned under differing climatic conditions and across topographic gradients (elevation, slope position, and aspect). We developed a Classification and Regression Tree model in order to further explore the interactions between topography, climate, and fire. The results demonstrate that climate is a strong driver of both spatial and temporal patterns of wildfire. Fire was most prevalent in the drier SNP than the wetter GSMNP, and during drought years in both parks. Topography also influenced fire occurrence, with relatively dry south-facing aspects, ridges, and lower elevations burning most frequently. However, the strength of topographic trends varied according to the climatic context. Weaker topographic trends emerged in the drier SNP than GSMNP, and during low-PDSI (dry) years than high-PDSI (wet) years in both parks. The apparent influence of climate on the spatial patterning of fire suggests a more general concept, that disturbance-prone landscapes exhibit weaker fine-scale spatial patterning of disturbance than do less disturbance-prone landscapes.

Belowground nitrogen dynamics in relation to hurricane damage along a tropical dry forest chronosequence

Understanding and predicting the responses of plant communities to multiple overlapping disturbances remains a challenging task. Hurricane Wilma represents a large, yet infrequent type of disturbance that was superimposed on an existing disturbance gradient of time since fire. We examined disturbance and recovery patterns in response to these overlapping disturbances by measuring how canopy structure, fine roots, mycorrhizae, and soil nitrogen dynamics, varied along a fire chronosequence in the 2 years after Hurricane Wilma. Hurricane damage increased canopy openness in all seral stages. In the early-seral stage, canopy openness returned to pre-hurricane conditions within 2 years, whereas canopy openness in the late-seral stage remained significantly higher throughout the study. We observed no significant change in root length density in the early- and mid-seral stages. However, in the late-seral stage, root length density was significantly reduced immediately after the hurricane and remained so 2 years after the hurricane. In the late-seral stage, we also observed a significant reduction in percent soil nitrogen and a significant increase in soil nitrogen isotopic composition (δ15N) values, indicating a loss of soil nitrogen. In contrast, in the early- and mid-seral stages, there were no significant changes in percent nitrogen or soil δ15N values. Results from this study suggest that forest fire disturbance history influences responses to hurricane damage. Moreover, feedbacks between aboveground and belowground processes have the potential to influence forest recovery.

Forest regrowth as the controlling factor of soil nutrient availability 75 years after fire in a deciduous forest of Southern Quebec

The effects of secondary succession on soil nutrient availability following fire in the 1920s was investigated in a hardwood forest of southern Quebec by correlation analyses between soil and solution chemistry, tree species composition, tree growth, litterfall nutrient fluxes and presence of charcoal monitored in six 300 m 2 plots between 1994 and 1998. The results suggests that the pioneer stand of largetooth aspen, paper birch and yellow birch that followed fire enriched the forest floor and upper mineral soil with its K-rich litter, but lowered solution NH4, NO3 and Mg concentrations through its high nutrient demand. High woody biomass primarily observed in the maple-dominated stands was associated with low exchangeable base cation concentrations in the forest floor, suggesting that nutrient immobilisation in trees is also a significant process leading to spatial variation in base cation availability in the forest floor. Finally, charcoal was positively correlated with exchangeable base cations in the forest floor which leads to believe that charcoal has a high affinity for base cations and that it can increase base cation availability decades after forest fire disturbance.

Multialtitude airborne observations of insolation effects of forest fire smoke aerosols at BOREAS: Estimates of aerosol optical parameters

Forest fire disturbance, as part of the natural cycle of the boreal ecosystem renewal, proved a significant factor in the acquisition scheduling of optical remote imagery at the northern study site of the Boreal Ecosystem‐Atmosphere Study (BOREAS), conducted in northern/central Canada during the July/August months of 1994. One such episode, between July 28 and 31, was due entirely to smoke transported over the study site from nearby and distant downwind fires. Noon insolation was reduced from 800 W/m2 on July 28 to 680 W/m2 on July 31 and incident PAR radiation from 320 to 250 W/m2. During the July 31 smoke episode the compact airborne spectrographic imager (CASI) was flown at 150, 300, 900, 1500, and 3200 m agl over a forested site, while measuring the scene‐reflected radiance as well as upwelling and downwelling irradiances in the spectral range 403 and 916 nm (2.5 nm resolution). These multialtitude observations of upwelling and downwelling irradiance and the hemispherical reflectance are used to estimate at two wavelengths, 550 and 672 nm, the vertical profiles of aerosol optical depth, attenuation coefficient, and single‐scattering albedo representative of the smoke aerosols encountered at BOREAS. For smoke aerosols from distant fires (high altitude) the single‐scattering albedo was 0.9 and the attenuation coefficient was 0.32 km−1 at 672 nm, whereas for smoke aerosols from nearby fires, values of 0.6 and 0.60 km−1 were found. This is qualitatively consistent with differences expected for distant primarily sulfate aerosols and higher soot aerosols for nearby flaming fires.